John W. Easton

National Center for Space Exploration Research, Glenn Research Center, Cleveland, Ohio

Peter M. Struk

Glenn Research Center, Cleveland, Ohio

Soldering in a Reduced Gravity 

Environment (SoRGE)

NASA/TM—2012-217119

January 2012
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John W. Easton

National Center for Space Exploration Research, Glenn Research Center, Cleveland, Ohio

Peter M. Struk

Glenn Research Center, Cleveland, Ohio

Soldering in a Reduced Gravity 

Environment (SoRGE)

NASA/TM—2012-217119

January 2012

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Acknowledgments

The SoRGE team would like to thank Astronaut Sunita Williams for her outstanding work on the SoRGE experiment during 

Expeditions 14 and 15 on the International Space Station, and for graciously providing time after the mission for a debriefing 

as well as generating the normal gravity samples used in this analysis. Ivy Apostolakopoulos of the Operational Support Office 

and Arthur Perry and Alyssa Mueller of the SDTO Office at NASA Johnson Space Center provided support for preparing and 

operating SoRGE aboard the ISS. The team would also like to thank Richard Pettegrew, formerly with the National Center for 

Space Exploration Research, Cleveland, Ohio, who was one of the original Principal Investigators and instrumental in the early 

work on reduced gravity aircraft as well as in the design, implementation, and operation of this work. Eric Anderson, formerly 

with ZIN Technology and currently with Arctic Slopes Research Corporation, Cleveland, Ohio, who designed the circuit board 

layout for this experiment. Gregory Funk of ZIN Technologies helped with the approval process and packaging for flight of the 

SoRGE hardware. Gary Gorecki of NASA Glenn Research Center provided soldering expertise and performed the inspections 

of the video record and circuit boards. Former students Anthony Rotella of Case Western Reserve University, Cleveland, Ohio, 

Joseph Ferry of the University of Missouri Science and Technology, Rolla, Missouri, and Robert Banks of Shaker Heights High 

School, Shaker Heights, Ohio all provided assistance with the analysis and measurement of the internal void structure and fillet 

length. YXLON International, Akron, Ohio, provided the CT x-ray scanning service generating the still images of the joint internal 

structure for this work. This work was funded by the Supportability Project of the Exploration Technology Development Program 

Office at NASA Langley Research Center.

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Trade names and trademarks are used in this report for identification 

only. Their usage does not constitute an official endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2012-217119 iii

Contents

1.0 Introduction...........................................................................................................................................1

1.1 Background...................................................................................................................................1

2.0 Experiment Description and Data Analysis..........................................................................................2

2.1 Experiment Description ................................................................................................................2

2.2 Description of Data Analysis........................................................................................................5

2.2.1 Fillet Length Analysis.......................................................................................................6

2.2.2 Visual Inspection and Selection of Joints for Analysis.....................................................6

2.2.3 Sample Preparation and Computed Tomography (CT) Analysis......................................6

3.0 Results.................................................................................................................................................10

3.1 Crew Debrief...............................................................................................................................10

3.2 Inspection of Operations Video Record......................................................................................11

3.3 Visual Inspection ........................................................................................................................13

3.4 Fillet Length................................................................................................................................16

3.5 Internal Void Analysis................................................................................................................18

4.0 Discussion and Recommendations .....................................................................................................26

4.1 Recommendations.......................................................................................................................28

Appendix A.—Tables of Board Visual Inspection Results ........................................................................31

Appendix B.—Graphs of Void Fraction Distribution.................................................................................43

References...................................................................................................................................................61
NASA/TM—2012-217119 iv
NASA/TM—2012-217119 1

Soldering in a Reduced Gravity Environment (SoRGE)

John W. Easton

National Center for Space Exploration Research

Glenn Research Center

Cleveland, Ohio 44135

Peter M. Struk

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

1.0 Introduction

Future long-duration human exploration missions will be challenged by constraints on mass and 

volume allocations available for spare parts. Addressing this challenge will be critical to the success of 

these missions. As a result, it is necessary to consider new approaches to spacecraft maintenance and 

repair that reduce the need for large replacement components. Currently, crew members on the 

International Space Station (ISS) recover from faults by removing and replacing, using backup systems, 

or living without the function of Orbital Replacement Units (ORUs). These ORUs are returned to a depot 

where the root cause of the failure is determined and the ORU is repaired. The crew has some limited 

repair capability with the Modulation/DeModulation (MDM) ORU, where circuit cards are removed and 

replace in faulty units. The next step to reducing the size of the items being replaced would be to 

implement component-level repair. This mode of repair has been implemented by the U.S. Navy in an 

operational environment and is now part of their standard approach for maintenance. It is appropriate to 

consider whether this approach can be adapted for future spaceflight operations. To this end, the 

Soldering in a Reduced Gravity Environment (SoRGE) experiment studied the effect of gravity on the 

formation of solder joints on electronic circuit boards.

This document describes the SoRGE experiment, the analysis methods, and results to date. This 

document will also contain comments from the crew regarding their experience conducting the SoRGE 

experiment as well as recommendations for future improvements. Finally, this document will discuss the 

plans for the SoRGE samples which remain on ISS. 

1.1 Background

This SoRGE experiment is a first step in developing a capability for crew members to perform repairs 

on electronic equipment at the component level, a potentially enabling capability for long duration 

missions, such as those to the moon and to Mars. The development of this capability is the objective of 

the Component Level Electronic Assembly Repair (CLEAR) task under the Supportability Project of 

NASA’s Exploration Technology Development Program. CLEAR has grown from and includes earlier 

reduced-gravity aircraft testing of the formation of solder joint in low-gravity. An electronics repair 

capability may also reduce some of the logistics burden imposed on the International Space Station (ISS) 

by the retirement of the space shuttle through the gradual testing and implementation of tools and 

techniques developed by the CLEAR effort.

The original research leading to the development of SoRGE focused on the formation of solder joints 

using plated through-hole components and circuit boards in reduced gravity (Ref. 1). The researchers 

conducted tests aboard NASA Reduced Gravity Aircraft (Ref. 2) using various fluxes with tin/lead 

solders, and compared these results with similar solder joints formed in normal gravity. One part of this 

analysis included sectioning the solder joints and analyzing the solder joint interior at the midplane. This 

research found that forming the solder joint in reduced gravity affected the inner structure of the joint.
NASA/TM—2012-217119 2

Solder joints formed in reduced gravity had more internal voids than similar joints formed in normal 

gravity. Internal voids form due to gasses evolved during the soldering process, from volatiles or other 

chemicals present in solder flux to water vapor released from the circuit board, as well as other possible 

sources. These voids are potential sources of reduced circuit performance, as the voids can reduce the 

electrical conductivity, thermal conductivity, and provide less support to mechanical loads, board stresses, 

and vibration. A hypothesis for the increase in void formation at low gravity focuses on the reduction of 

buoyant forces driving the gas bubble out of the solder joint before the solder freezes.

In 2000, this team proposed the SoRGE to be flown as a Station Development Test Objective (SDTO) 

task aboard the ISS to assess the effect of true micro-g on the soldering process. The g-jitter present 

during aircraft operations is not present on ISS, and may affect the creation and distribution of gas 

pockets and voids within the solder joint. Furthermore, the previous research also evaluated potential 

mitigation techniques to minimize the void formation—these techniques were to also be tested as part of 

the SDTO. The SoRGE SDTO was delayed several years due to the Return to Flight activities and reemerged as an activity for the newly formed CLEAR task. The CLEAR team felt that exploring this 

question is important to developing an electronics repair capability. Later, as the CLEAR task evolved, 

the SoRGE opportunity was viewed as a first chance to attempt training an astronaut, who most likely 

will not have previous experience in performing electronics repairs, to perform this type of work in 

reduced gravity. At that time, the CLEAR team felt that repairs were a contingency item and that 

crewmembers would get only very limited training for this activity. As such, the training consisted only 

of video and written procedures that were uplinked to the crew.

This document will begin by describing the experiment, including the solder and flux combinations 

used, the layout of the circuit boards used for forming joints, and the process and tools used by the 

astronaut to form the solder joints. The experiment description will also include the methods used to view 

and inspect the video record of the operations, the inspection of the circuit boards themselves, measuring 

the fillet lengths, and measuring the amount of voids formed within the solder joints. The results section 

will present the data acquired from these analyses, and briefly compare them to previous work. The 

document will conclude with a discussion of the results and recommendations for future work and for 

enabling an electronics repair program for future space flight missions.

2.0 Experiment Description and Data Analysis

The SoRGE experiment focused on the formation of solder joints in reduced and normal gravity. In 

particular, the experiment focused on the ability and difficulties for a minimally trained crew member to 

perform the task, and on the formation of voids within the solder joint as a function of gravity. The 

following sections describe the experiment, including the three types of solder and flux used as well as the 

circuit boards and tools and facilities available on the ISS. These sections also discuss the returned 

materials and data analysis.

2.1 Experiment Description

The SoRGE flight experiment examined three solder and flux combinations, described in Table 1. All 

fluxes were active rosin (RA), type “44” manufactured by Kester, Inc., and all wires were 0.031 in. in 

diameter. The first combination consisted of a 60% tin, 40% lead solder wire with a core of rosin solder 

flux, referred to as “Flux Core Kit A” in the experiment kit. Solder joints formed on returned circuit 

boards labeled as either “A” or “B” as well as the board “GA” produced on Earth used this solder and flux 

combination. This solder is identical to the solder currently part of the US Soldering Kit. The second 
NASA/TM—2012-217119 3

combination was similar to the first, but used a eutectic1 tin-lead solder while using the same flux as used 

in the “Flux Core Kit A” samples. These flight kits are referred to as “Flux Core Kit B”, and the returned 

circuit boards using this solder and flux are labeled either “E” or “F”. The third combination used a solid 

60% tin, 40% lead solder wire and a liquid rosin flux supplied in a syringe which was applied to the 

circuit board and component immediately before soldering; these are referred to as “Liquid Flux Kits” in 

the flight manifest, and joints formed with this solder and flux combination are from boards “J” and “K”, 

with ground samples formed on board “GC”. Figure 1 shows one of these kits, including the circuit board, 

solder wires, solder return bag, and flux syringe, and Table 1 shows the solder, flux, gravity level, and 

board designations. Each kit contained a circuit board (Figure 2) with 16 standard resistors fixed to the 

board with a RTV adhesive and each resistor lead positioned within a through hole on the circuit board.

This provides the astronaut-operator with thirty-two solder joints to form on each circuit board. The kit 

also contains 32 individually weighed solder wires of the appropriate type, one for each solder joint. The 

SoRGE team recorded the weight of the solder wires prior to launch; weighing the returned wires 

provided a measure of the solder used to form the joint.

TABLE 1.—LIST OF SOLDER, FLUXES AND GRAVITY LEVELS USED IN SoRGE EXPERIMENT

Solder Flux Gravity level 

(g)

Board letter

60% tin-40% lead RA, core of solder wire 0 A

60% tin-40% lead RA, core of solder wire 0 B

60% tin-40% lead RA, core of solder wire 1 GA

Eutectic RA, core of solder wire 0 E

Eutectic RA, core of solder wire 0 F

60% tin-40% lead RA, external liquid 0 J

60% tin-40% lead RA, external liquid 0 K

60% tin-40% lead RA, external liquid 1 GC

Once on orbit, the crew assigned to this task used the kits described with ISS materials to form solder 

joints. The astronaut assembled the Containment Area, a tent-like glovebox which mounts on the 

Maintenance Work Area (MWA), a table that attaches to rack frames in the walls of the ISS. With this 

equipment in place, the U.S. Soldering Kit and board clamp were installed within the Containment Area

(Figure 3). The U.S. Soldering Kit is a commercial soldering iron wand with a 600 °F tip, modified to 

accept a power tool battery for power. Finally, the astronaut installed a camera and mounting arm within 

the Containment Area to record the soldering process. Reference 3 contains more information on these 

items. After assembling this equipment, the astronaut then placed one of the SoRGE kits in the 

Containment Area, placed the circuit board in the circuit board clamp, and arranged the solder wires and 

flux (if used) as comfortable. Prior to soldering, the astronaut closed the access port of the Containment 

Area, using glove ports to work with objects and viewing the work through the clear plastic side walls or 

a Fresnel lens (0.9X magnification) mounted in the wall. Based on the previous work already described, 

the SoRGE experiment called for a specific process for forming a solder joint, described in the written 

experiment procedures and a training video developed by the team. In this process, the crew member 

applied the hot soldering iron tip to the joint area for a “mental count” of 3 sec to preheat the area, then 

applied the appropriate solder wire to form the joint, removed the wire, and finished with a post-heating 

period of 3 sec (again using a “mental count”) prior to removing the soldering iron. The astronaut applied 

the soldering iron and solder wire to the component leg on the side of the circuit board opposite the 

component. In the analysis, this fillet is referred to as the soldered fillet. The fillet formed on the 

component side of the circuit board, from solder flowing through the through-hole, is referred to as the 

flowed fillet.

 1

Eutectic alloys are alloys where, for a specific ratio of constituents, the constituents completely melt at the same 

temperature. Non-eutectic alloys have states where one constituent does not completely melt for a given 

temperature. This plastic state may contribute to the formation of voids or other flaws in the soldering process. For 

tin-lead alloys commonly used in electronics soldering, the eutectic ratio of constituents is 63% tin and 37% lead.
NASA/TM—2012-217119 4

Figure 1.—A SoRGE soldering kit, including numbered solder wires, flux syringe, and solder return bag. The 

inset photo shows the circuit board taped to the back of the solder wire holder.

Figure 2.—An unused SoRGE circuit board and 

drawing of a resistor and two joint locations. The 

soldering occurs on the bare leg of the resistor, 

forming the soldered fillet. Solder flows into the 

through hole and forms the flowed fillet on the 

resistor body side of the circuit board.
NASA/TM—2012-217119 5

Figure 3.—Astronaut Sunita Williams performing the SoRGE experiment in the Containment Area on the 

International Space Station.

Over the course of Increments 14 and 15 aboard the ISS (March and May of 2007) Astronaut Sunita 

Williams conducted six runs of the SoRGE experiment (Figure 3), using two kits from each of the three 

solder-flux combinations. Circuit boards A and B were soldered using a 60% tin-40% lead, rosin flux 

cored solder wire in reduced gravity, while joints on board GA were soldered with this material in normal 

gravity. Joints from boards E and F were formed using a eutectic solder wire with a rosin flux core.

Normal gravity samples formed with this solder and flux were taken from previous work (Ref. 4). Circuit 

boards J and K were formed using 60% tin-40% lead solid solder wire with an external liquid flux in 

reduced gravity, while joints on board GC were formed with this solder and flux combination in normal 

gravity. These kits were returned to the SoRGE team in fall 2007, with the six unused kits remaining on 

the ISS for potential future use. In addition, the SoRGE team received video tapes and some limited 

photographs of the solder process to determine the effectiveness of and future improvements to the 

training materials, and to document any difficulties encountered during the soldering process.

2.2 Description of Data Analysis

The following sections describe the analysis of the returned SoRGE solder samples and the 

accompanying video recordings of the work, as well as a later debriefing of the astronaut who performed 

the work. The first section discusses the measurement of fillet length, for a comparison of the lengths 

between joints formed in normal gravity to those formed in reduced gravity. Next, the discussion focuses 

on the inspection of the joint quality based on NASA standards, and an inspection of the video record for 

techniques used and problems encountered while forming the solder joints. The final section describes the 

method for selecting and preparing solder joints for analysis of the internal structure, and how the series 

of images describing the internal structure of the joints are analyzed.
NASA/TM—2012-217119 6

Figure 4.—Side view of a solder joint, showing 

the leg length of the joint’s bottom fillet.

2.2.1 Fillet Length Analysis

Measuring the length of the soldered fillet and the flowed fillet and comparing these measurements 

for joints formed in reduced gravity with those formed in normal gravity gives an indication of the 

gravitational effects on joint formation. Earlier work (Ref. 1) has shown a gravitational effect. Measuring 

the fillet lengths from the SoRGE samples will show if a lower gravity level, with less variation in gravity 

due to g-jitter, has an effect on the joint shape. The first step to measuring fillet lengths is to photograph 

the fillets. Two fixtures constructed on an optical table with optical mounts allowed for positioning a 

video camera at the same height and parallel to the sample circuit card edge. Individual still images of 

each fillet are taken from the video, with a sample shown in Figure 4. This figure also shows the leg 

length, defined as the distance from the circuit board face to the point on the resistor lead where the 

applied solder stops and no longer wets the lead. A macro written for the image analysis software ImageJ

(Ref. 5) records the pixel location of the solder/circuit board and solder/component leg interfaces, which 

are manually determined by the user. The calculated distance between these two points is reported as the 

fillet length.

2.2.2 Visual Inspection and Selection of Joints for Analysis

This section summarize the results of a visual inspection performed by a NASA trained, flight 

qualified electronics technician. The technician used a stereo microscope set to 4X magnification to 

inspect for a variety of surface flaws in the solder joint, described in the NASA soldering standards 

(Ref. 6) and indicative of problems with the soldering process for that specific joint. The inspection 

included analysis of the topside (component side) of the circuit board, the bottom (soldering) side, and the 

overall acceptance of the solder joint, requiring acceptance of both the top and bottom sides of the joint.

Each board side passed, marginally passed, or failed inspection. Joints that marginally passed had some 

problem with the soldering process that would have lead to a failing evaluation for an experienced 

technician, but may be allowed given the astronaut’s experience level and minimum impact to the circuit.

The top and bottom side analyses included notes on why the joint did not pass inspection, but no notes 

when the joint passed. Marginally acceptable solder joint sides also had notes on the potential problem 

with the solder joint.

2.2.3 Sample Preparation and Computed Tomography (CT) Analysis

After examining the exterior features of the solder joints and evaluating them against the NASA 

Standard criteria, the next analyses focused on the joint interior. The results give a measure of the interior 

voids within the solder joint, and the effect of gravity and solder and flux combinations on the amount of

voids. This process begins with a NASA soldering technician and instructor conducting a secondary 

examination of the SoRGE flight and ground solder joints. Additional examination is required because, in 

the case of the flux cored solder, more than ten joints passed the original inspection, while the solid core 
NASA/TM—2012-217119 7

solder with liquid flux cases yielded fewer than ten acceptable joints, requiring a selection of joints that 

did not initially pass inspection. Selecting samples from those made with a solid cored solder (again using 

60% tin, 40% lead solder) with a liquid flux required choosing joints that did not pass the initial selection 

in order to provide samples for CT analysis. Selecting flawed joints focused primarily on the appearance 

of the flowed fillet side of the solder joint. Joints with the best flowed fillet indicated that the solder 

flowed through the through-hole properly, forming an effective joint even with problems forming the 

soldered fillet. Further, the soldered side of the joint must not show excessive problems; it must have 

good wetting, but may exhibit excessive solder amounts or small spikes. Joints with large spikes, solder 

drags, or poor wetting on the bottom were not selected. Joints where the soldered fillet was overheated 

were accepted in this analysis. The methods of selection apply to ground samples as well as flight 

samples.

After selecting the solder joints for internal analysis, a technician removes the joints from the circuit 

board by cutting the lead close to the resistor body, preserving the bend in the lead, and then cutting the 

joint area out of the circuit board. The bend in the resistor lead is preserved to distinguish between the 

flowed fillet (fillet closest to the bend) and soldered fillet (fillet farthest from the bend) in the x-ray 

images. The individual solder joints are then encapsulated in a plastic disk, using a technique developed 

to prepare samples for metallographic grinding. Each disk contains between one and three solder joints 

such that each disk only contains joints from one of the circuit boards. The plastic disk protects the solder 

joints from damage or loss after removal from the circuit board, and prepares the joints for potential 

destructive testing where the joint is ground to a specific depth and the revealed inner plane is analyzed 

for voids.

After encapsulating the solder joints in plastic disks, the samples were sent to a commercial nondestructive testing laboratory, YXLON International in Akron, Ohio. This laboratory performed CT 

scanning of the individual solder joints in a process described in (Ref. 7), producing a series of images 

numbering from 250 to 300 for each solder joint, each image taken along the center axis (parallel to the 

component lead) of the solder joint. Figure 5 shows a sequence of images from one of these joints, with a 

resolution of 0.018 mm/pixel for this joint. Images a and b show the increasing diameter of the soldered 

fillet, while images i and j show the decreasing diameter of the flowed fillet. The remaining images are 

from the interior through-hole region. These images show the solder as a bright white, with gray lead and 

gray-to-black internal voids. The resolution of these images ranges from 0.015 to 0.020 mm/pixel.

With the sequence of images describing the internal structure of the solder joints, the analysis begins 

to determine the fraction of voids within the solder joint, and compare these values for the various flux 

combinations in both reduced and normal gravity. The SoRGE team used ImageJ (Ref. 5). The process 

for measuring void areas and volumes requires two steps. First, the total area of the solder joint in each 

image is measured, using a grayscale threshold (a minimum gray level, counting pixels above this level 

and ignoring those below) to isolate the joint area from external features in the image, such as x-ray 

reflections or plating. This process counts the area (or pixels) highlighted by the thresholding process and 

includes any interior holes not highlighted by thresholding. In the through-hole area of the joint, threshold 

levels that excluded reflections and plating did not always close and include voids near the edge of the 

joint. For these images, the user drew in a line, based on the line of plating, to close off these voids and 

include them in the total area measurement. Measuring the total area required few changes in the 

threshold level throughout the joint; typically, the fillets and the through-hole regions required different, 

though similar, threshold levels, with little if any change in threshold within these regions. Figure 6 shows 

this process.
NASA/TM—2012-217119 8

Figure 5.—Sequence of images describing the interior of a 

solder joint. The images show the lead and voids within 

the equally spaced images. Images a and b are taken 

from the soldered fillet, images c through h from the 

annular region, and images i and j from the flowed 

fillet. Image b demonstrates the lead and typical voids.
NASA/TM—2012-217119 9

Figure 6.—Applying threshold to measure total joint area. The process begins with the original image (left), 

applies a threshold (center), then draws a line or lines to close the image (right).

Figure 7.—Process for measuring solder area. Begin with the original image (left), then apply Unsharp Mask 

and Smooth (center), followed by threshold and Despeckle (right).

The next step in the void measurement process is to measure the area (or pixels) of solder, isolating 

and removing the voids. This process begins by using the Unsharp Mask function in ImageJ, to increase 

the contrast between the gray levels of the solder and voids, followed by a smoothing function to reduce 

granularity introduced by the Unsharp Mask. The user then sets the threshold level for the image. While 

only one level is typically used for the through-hole region, a range of levels is required for the fillet 

regions. The fillet images require a range of threshold levels because the amount of solder varies from 

image to image, with more solder near the plating region decreasing the contrast between solder and void, 

while near the ends of the joint the small amount of solder leads to greater contrast between the voids and 

the solder. After setting the threshold, the routine then performs a Despeckle operation to remove more 

noise, then a Watershed operation to isolate voids from the solder. After this operation, the routine then 

counts the highlighted pixels representing solder in the joint area. (All the functions and operations used 

in the analysis routine are described in Ref. 5.) This is shown in Figure 7. For both the total area and 

solder area measurements, regions near the circuit board, transitioning from fillet to or from through-hole 

region, were difficult to measure due to plating on the circuit board and the sudden change in joint 

diameter. For this reason, these areas are not included in the analysis and calculations. The transitions 

from fillet to through-hole region to opposite fillet also mark the boundaries for three regions of the joint, 

as shown in Figure 8. The soldered fillet and flowed fillet have already been described. The region of 

solder filling the through-hole of the circuit board is referred to as the annular region. The use of “annular 

region” is restricted to the analysis of voids within the joint interior.
NASA/TM—2012-217119 10

Figure 8.—Drawing of the three regions of a solder 

joint: the soldered fillet, where heat and solder 

are applied, the annular region within the circuit 

board through-hole, and the flowed fillet near 

the resistor.

After making these two measurements, total joint area and solder area, the user must then measure the 

area of the component lead. This is done manually, using the average of the lead area in five evenlyspaced images along the image set for the joint. Once this is done, the void area may be calculated. First, 

the average lead area and solder area are subtracted from the total area measurement for each image. The 

remaining value is the area of voids in the image. Dividing the void area by the total area, minus lead 

area, for each slice gives the slice void fraction. Plotting the slice void fraction as a function of position 

along the joint gives a measure of the distribution of voids within the joint and a method for determining 

any trends in this distribution among flux types and/or gravity levels. Additionally, integrating the total 

joint area (minus lead area) as well as the void area over the joint gives the total volume and void volume.

The integrations were calculated using the trapezoidal rule (Ref. 8). The ratio of the void volume and total 

volume, the void volume fraction, gives a measure of the total amount of voiding in a particular joint, and 

is used to compare joints across solder and flux type and in varying gravity.

3.0 Results

The following section describes the results of the SoRGE operations and analysis. It begins with a 

summary of the comments of Astronaut Sunita Williams, who conducted the SoRGE experiment during 

Expeditions 14 and 15, in March and May 2007. It is followed by the results of viewing the video record 

of SoRGE operations aboard the ISS, and then by the results of a visual inspection of the returned circuit 

boards and formed solder joints. Next, the results of measurements of the fillet lengths are reported, and 

finally the results of examining the internal voids of the solder joints are reported as well.

3.1 Crew Debrief

On August 27, 2007, the SoRGE team had the opportunity to speak with and debrief Astronaut Sunita 

Williams, who conducted the SoRGE testing during Expeditions 14 and 15, March and May 2007. The 

following section summarizes her comments, focusing mainly on prior training and experience, comments 

on conducting the soldering tests, and comments on requirements for a future capability, based on 

performing the SoRGE experiment.

Astronaut Williams commented that she did not have any soldering experience prior to performing 

SoRGE operations. Pre-launch familiarization sessions introduced Astronaut Williams to the various tool 

kits available on the ISS, including the U.S. Soldering Kit used for SoRGE. This familiarization did not 

include any demonstrations or hands-on experience in soldering, either with a SoRGE sample or with a 

standard training circuit board. The SoRGE written procedures and training video were the first exposure 

to soldering provided by NASA. Astronaut Williams found both the written procedures and, particularly, 

the training video helpful. She read the procedures prior to working on SoRGE. During operations she 

conducted the various soldering tasks without referring to the step-by-step procedures, as reading during 

this process is not possible.
NASA/TM—2012-217119 11

The initial set-up of the MWA and the Containment Area took quite a bit of time in the initial stages 

of the SoRGE experiment, though the soldering progressed quickly afterwards. Astronaut Williams 

commented that she used the procedures for forming a solder joint (described earlier) consistently, and 

became more comfortable with the work as it progressed. One area of difficulty with this experiment 

arose from working with the Containment Area, mostly focusing on visibility. The Containment Area 

effectively provided visibility only through a small (approximately one foot long and a half foot wide) 

lexan viewport with a small amount of magnification. The clear plastic side walls were difficult to see 

through due to wrinkles introduced by packing and storing the Containment Area for extended periods.

The use of safety glasses while working within the Containment Area may have also contributed to the 

visibility problems, but many of the difficulties arose from the Containment Area itself. Astronaut 

Williams used the video camera installed in the Containment Area as a visual aid, watching the work area 

with the camera view finder and using the lens zoom function to improve joint visibility. Another 

problem with the Containment Area was the size of the area, which physically increased the distance from 

the work area and the operator. One of the purposes of the Containment Area, preventing the release of 

solder balls into the module cabin, did not arise. Soldering and forming joints on the circuit board did not 

generate solder balls, though they were formed when cleaning solder from the soldering iron tip with a 

damp sponge. Astronaut Williams kept track of these solder balls, which typically stuck to the side walls 

or other objects within the Containment Area and were removed with the vacuum. Due to noise, the 

vacuum was run periodically to clean solder balls rather than continuously.

Based on her first-hand experience soldering in reduced gravity with the SoRGE experiment, 

Astronaut Williams had some recommendations for a future repair capability. A repair capability will 

require good training, including on-the-job training, and ground support. Training videos and a “cheat 

sheet” outline common repair steps should be provided to the crew conducting a repair, as well as 

resources and materials for practicing soldering techniques, both for a specific job as well as for general 

skill maintenance. Real time downlink and communications with a ground support team will also improve 

the repair, with the support team providing help and critiques of the work in a timely manner. Also, as 

crew size increases, a member of the crew should be knowledgeable about performing soldering repairs, 

and have experience and training before the mission begins. Another area for improvement is the 

Containment Area. The Containment Area should be smaller, allowing the operator to position 

themselves closer to the work area, improving visibility and comfort. Magnification should also be 

improved. This can include the use of a video camera and monitor, requiring the camera to be oriented 

and focused correctly, and after some practice by the crew working to a monitor rather than with direct 

viewing.

3.2 Inspection of Operations Video Record

The video record of SoRGE operations provided information on the tools and operating environment 

of the ISS, as well as the effectiveness of the training video provided by the SoRGE team. In general, the 

circuit board fills the camera field of view, providing a close enough view to see the soldering techniques 

used, as well as any difficulties encountered during soldering. The still image shown in Figure 9

demonstrates a typical view from the video record. This view generally was not sufficient to judge the 

quality of a solder joint, except in some cases where the operator encountered problems while soldering 

the joint.

The video record showed a problem with the ISS Soldering Iron Kit that was not expected by the 

SoRGE team, and may have negatively impacted the solder joint quality. As seen in Figure 10, the 

soldering iron tip used was curved, with an approximate 45° bend at the approximate middle of the tip.

The ISS Soldering Iron Kit does not include any soldering iron tips with a bend; all provided tips are 

straight. This indicates that the soldering iron tip was damaged prior to use on the SoRGE experiment.

Additionally, the soldering iron tip appeared discolored, which could be indicative of reduced 

performance.
NASA/TM—2012-217119 12

Figure 9.—Typical image from videotaped record of SoRGE solder joint formation by Sunita Williams 

aboard the ISS.

Figure 10.—Close-up image of the ISS 

Solder Kit soldering iron tip. The bent 

section of the tip is in contact with the 

solder wire, component lead, and 

circuit board land.

The damaged soldering iron tip has a number of implications in terms of effectiveness for both the 

SoRGE experiment and general use during other ISS operations. First, the bend could indicate a change in 

tip temperature. The soldering iron tip is resistively heated, and the action that caused the tip to bend may 

have damaged the electrical connection between the tip and the soldering iron, connections between 

layers of material in the tip, electrical connections within the tip, or any combination of these effects. The 

change in tip shape could also affect the contact between the soldering iron tip and the circuit 

components—the resistor leg and circuit board through hole or land—in a way that reduces the rate of 
NASA/TM—2012-217119 13

heat transfer from the soldering iron tip to the joint area. While the tip used did provide enough heat to 

melt the solder wire and form solder joints, the potential reduction in performance of the tip may have 

made the astronaut’s task more difficult than expected, and adversely affect the results of the experiment.

Analysis of the videotaped operations also pointed out a problem with the video training that the 

SoRGE team provided. The training video did not adequately emphasize proper soldering technique for 

someone who never soldered previously. This video focused on an end-to-end process for forming solder 

joints, including applying an external liquid flux if necessary, the time required to preheat the joint prior 

to adding solder, and the post-heat time which occurs after adding solder to the joint but prior to removing 

the soldering iron. Although the video showed the end-to-end process, more emphasis needed to be 

placed on the proper position of the soldering iron relative to the resistor leg and circuit board, forming a 

heat bridge between the soldering iron and joint area with a small amount of solder, and the proper 

techniques for applying and removing the solder wire and removing the soldering iron. As a result, only a 

limited number of solder joints passes the post-flight visual inspection as discussed below. Nonetheless, 

the SoRGE team feels that the training video format can be effective provided that it emphasizes certain 

key techniques of the soldering process.

3.3 Visual Inspection

As the data in Table 2 through Table 7 show only one circuit board had joints with over 50 percent

pass rate, a kit with a flux cored solder wire. Two other kits showed an overall pass rate of approximately 

20 percent, both of which were also flux cored kits. The other three kits, two with solid cored solder wire 

and external liquid flux and the third with a flux cored wire, demonstrated problems with forming solder 

joints, with pass rates of 6 percent or less. Figure 11 and Figure 12 show a good solder joint, which passes 

NASA Standard 8739.3. This joint’s fillets are concave, relatively smooth and symmetric about the lead, 

and have a bright surface finish. Problems with wetting the solder joint were one of the most common 

problems with the soldering process. In a number of cases, the operator added solder to the bottom of the 

board, sometimes in large or excessive amounts such as Figure 13, but the solder did not flow, or flowed 

poorly, through the circuit card through hole and did not wet the component leg and circuit board pad on 

the top side of the circuit board, seen in Figure 14. The poor wetting occurred with all solder-and-flux 

combinations. This problem can be caused by insufficient heating of the solder joint, whether through 

technique (such as not forming a heat bridge prior to adding solder for the joint, or through improper 

placement of the soldering iron tip in the solder joint area) or through damage to the soldering iron tip not 

allowing the tip to reach full operating temperature. Contamination of the solder joint as evidenced by the 

discolored soldering iron tip is, in general, another potential cause.

TABLE 2.—VISUAL INSPECTION RESULTS FOR 

SOLDER JOINTS FORMED IN REDUCED GRAVITY 

USING 60% TIN-40% LEAD FLUX CORED SOLDER, BOARD A

Location Number passed Percentage passed

Flowed fillet 7 22%

Soldered fillet 16 50%

Both fillets 7 22%

TABLE 3.—VISUAL INSPECTION RESULTS FOR 

SOLDER JOINTS FORMED IN REDUCED GRAVITY 

USING 60% TIN-40% LEAD FLUX CORED SOLDER, BOARD B

Location Number passed Percentage passed

Flowed fillet 16 50%

Soldered fillet 18 56%

Both fillets 6 19%
NASA/TM—2012-217119 14

TABLE 4.—VISUAL INSPECTION RESULTS FOR SOLDER 

JOINTS FORMED IN REDUCED GRAVITY USING 

EUTECTIC FLUX CORED SOLDER, BOARD E

Location Number passed Percentage passed

Flowed fillet 11 34%

Soldered fillet 8 25%

Both fillets 2 6%

TABLE 5.—VISUAL INSPECTION RESULTS FOR SOLDER 

JOINTS FORMED IN REDUCED GRAVITY USING 

EUTECTIC FLUX CORED SOLDER, BOARD F

Location Number passed Percentage passed

Flowed fillet 18 56%

Soldered fillet 22 69%

Both fillets 18 56%

TABLE 6.—VISUAL INSPECTION RESULTS FOR SOLDER 

JOINTS FORMED IN REDUCED GRAVITY USING 60% TIN40% LEAD SOLDER WITH EXTERNAL LIQUID FLUX, BOARD J

Location Number passed Percentage passed

Flowed fillet 15 47%

Soldered fillet 2 6%

Both fillets 1 3%

TABLE 7.—VISUAL INSPECTION RESULTS FOR SOLDER

JOINTS FORMED IN REDUCED GRAVITY USING 60% TIN40% LEAD SOLDER WITH EXTERNAL LIQUID FLUX, BOARD K

Location Number passed Percentage passed

Flowed fillet 8 25%

Soldered fillet 2 6%

Both fillets 2 6%

Figure 11.—Example of a successful solder joint, seen 

from the soldered fillet of the circuit board (Eutectic 

flux cored solder, joint F28).

Figure 12.—Example of a successful solder joint, seen 

from the flowed fillet of the circuit board (Eutectic flux 

cored solder, joint F28).
NASA/TM—2012-217119 15

Figure 13.—Example of excessive solder, seen from the 

soldered fillet side of the circuit board (60%tin-40% 

lead flux cored solder, joint B3).

Figure 14.—Example of poor wetting seen from the 

flowed fillet side of the circuit board (Eutectic flux 

cored solder, joint E10).

Figure 15.—Example of a solder spike, seen from the 

soldered fillet side of the circuit board (Eutectic flux 

cored solder, Joint E5).

Figure 16.—Example of an overheated joint with a solder 

spike, seen from the soldered fillet side of the circuit 

board (60% tin-40% lead external liquid flux, joint 

K14).

Other problems, typically seen on the bottom side of the circuit board, include solder spikes and 

solder drag. Solder spikes, such as the one shown in Figure 15, occur when the soldering iron is removed 

before the solder wire; the solder cools and solidifies as the wire is removed, leaving a spike. Solder drag 

deforms the bulk of the solder fillet when the iron tip drags along the fillet while removing the iron. In 

both cases, molten solder does not immediately detach from the soldering iron as the iron is removed 

from the joint. The solder does not release from the soldering iron tip for several potential reasons, 

including overheating of the joint, the operator not removing the tip fast enough, or the flux in the joint 

area deactivating due to time or overheating. Underheating may also be a cause of solder spikes and 

drags, as it can lead to decreased solder wetting and the flux not activating properly. This pulling action 

can form a spike of solder, while moving the soldering iron tip through the bulk solder of the joint can 

form a drag. Solder spikes can create a region prone to arcing in high voltage applications; spike should 

also be avoided in low voltage applications, but may be permissible in limited circumstances. Solder drag 

can redistribute solder through the joint, leading to voids and poor wetting on the opposite side of the 

circuit board. In other cases, the operator did not add enough solder to form a solder joint, or added the 

solder to the end of the component lead, not at the lead-circuit board land interface. These joints failed 

simply because there was not enough solder to form the joint. Another problem found in the inspection 

was overheating the solder joint, shown in Figure 16, where the operator leaves the soldering iron tip in 

contact with the joint too long. An overheated solder joint may become brittle or develop more voids than 
NASA/TM—2012-217119 16

Figure 17.—Example of a blowhole seen from the 

flowed fillet side of the circuit board (Eutectic 

flux cored solder, joint F3).

joints formed with shorter soldering iron tip contact times. A final problem found during inspection was 

voids (sometimes referred to as “blowholes”) seen in the surface of the solder joint, as in Figure 17.

Trapped gases within the solder joint escaped just before the solder solidified, leaving a dimple in the 

surface of the solder joint. This is usually indicative of voids remaining within the solder joint, and leads 

to rejection during the visual inspection. The detailed inspection results for each board and joint are 

shown in 0.

3.4 Fillet Length

The fillet ratio is defined as the ratio of the height of the soldered fillet to the flowed fillet measured 

along the resistor lead (Figure 4 and Figure 8). Table 8 through Table 12 list the fillet height ratio for each 

solder joint that passed visual inspection2

. The tables list the joint, the fillet ratio, and the average and 

standard deviation of the corresponding data set. In reduced gravity (Table 8, Table 10, and Table 11), the 

data show that the fillet lengths are not equal with the soldered fillet typically being longer than the 

flowed fillet (i.e., the fillet ratio of 1.61 ± 0.33, 1.20 ± 0.16, 2.25 ± 0.54). Previous work using NASA’s 

Reduced Gravity Aircraft (Ref. 1) showed mean values of 1.08±0.04 for flux-cored solder in normal 

gravity. For solid-core solder with external flux, the reduced-gravity ratio was similar, specifically 1.16 

±0.04. Although the number of samples in the current tests were limited making true statistical 

comparisons difficult, the results are generally consistent with the results obtained in the previous aircraft 

experiments and show that the absence of gravity has an effect on drawing solder from the soldered to 

flowed fillet.

In normal gravity (Table 9 and Table 12), the fillet ratio were 0.98 ± 0.40 and 1.38 ± 0.29, for fluxcored and solid solder, respectively. The previous work showed mean values of 0.76 ± 0.03for flux-cored 

solder in normal gravity and 0.71± 0.10 for solid-core solder with external flux. The solders and fluxes 

used in both cases were similar, with the exception of the eutectic solder in this study, as were the circuit 

board layouts and soldering techniques. While the results for the flux-cored solder are consistent (within 

the confidence intervals) with the previous normal gravity results, the authors believe that the higher fillet 

ratio for solid-core wire was due to the inherent difficulty experienced by the operator in making the solid 

core wire flow properly leaving more solder on the soldered side of the joint.

 2 For some cases using an external liquid flux, solder joint were select that did not pass inspection but were 

functional to allow for large sample sizes.
NASA/TM—2012-217119 17

TABLE 8.—SOLDERED FILLET TO FLOWED FILLET LENGTH

RATIO FOR REDUCED GRAVITY, 60% TIN-40% LEAD 

ROSIN FLUX CORED SAMPLES

Joint Fillet ratio

A13 ...................................................................................1.14

A14 ................................................................................... 1.29

A25 ................................................................................... 2.00

A29 ................................................................................... 0.95

A30 ................................................................................... 1.32

B6 ..................................................................................... 2.00

B8 ..................................................................................... 1.39

B13.................................................................................... 1.91

B21.................................................................................... 1.40

B29.................................................................................... 2.72

Average............................................................................. 1.61

Standard deviation ............................................................ 0.53

95% confidence int. ..........................................................0.33

TABLE 9.—SOLDERED FILLET TO FLOWED FILLET LENGTH

RATIO FOR NORMAL GRAVITY, 60% TIN-40% LEAD

ROSIN FLUX CORED SAMPLES.

Joint Fillet ratio

GA1 .................................................................................. 0.83

GA4 .................................................................................. 1.78

GA5 .................................................................................. 0.68

GA6 .................................................................................. 0.83

GA7 .................................................................................. 0.78

Average............................................................................. 0.98

Standard deviation ............................................................ 0.45

95% confidence int. .......................................................... 0.40

TABLE 10.—SOLDERED FILLET TO FLOWED FILLET LENGTH

RATIO FOR REDUCED GRAVITY, EUTECTIC

ROSIN FLUX CORED SAMPLES

Joint Fillet ratio

E26....................................................................................1.13

F6...................................................................................... 1.69

F9...................................................................................... 1.00

F11.................................................................................... 1.14

F13.................................................................................... 1.07

F31.................................................................................... 1.21

F32.................................................................................... 1.19

Average............................................................................. 1.20

Standard deviation ............................................................ 0.22

95% confidence int. .......................................................... 0.16
NASA/TM—2012-217119 18

TABLE 11.—SOLDERED FILLET TO FLOWED FILLET LENGTH

RATIO FOR REDUCED GRAVITY, 60% TIN-40% LEAD

EXTERNAL LIQUID FLUX SAMPLES

Joint Fillet ratio

J19..................................................................................... 1.68

J20..................................................................................... 3.81

J22..................................................................................... 3.11

J28..................................................................................... 1.38

J29..................................................................................... 2.48

K7 ..................................................................................... 1.90

K14 ................................................................................... 2.17

K22 ................................................................................... 3.12

K23 ................................................................................... 1.15

K25 ................................................................................... 1.70

Average............................................................................. 2.25

Standard deviation ............................................................ 0.86

95% confidence int. .......................................................... 0.54

TABLE 12.—SOLDERED FILLET TO FLOWED FILLET LENGTH

RATIO FOR NORMAL GRAVITY, 60% TIN-40% LEAD

EXTERNAL LIQUID FLUX SAMPLES

Joint Fillet ratio

GC3................................................................................... 1.64

GC6................................................................................... 1.61

GC7................................................................................... 1.62

GC8................................................................................... 1.04

GC10................................................................................. 0.99

Average............................................................................. 1.38

Standard deviation ............................................................ 0.33

95% confidence int. .......................................................... 0.29

The key differences between the two studies were the prior experience of the operator and the 

soldering iron temperature. The operator in this study had less soldering experience and training than 

those individuals in the earlier work. Also, the solder iron tip temperature in reduced gravity aircraft tests 

was higher (~700 °F) compared with the ISS maximum tip temperature (~600 °F). Both of these make 

soldering with solid-core solder more difficult and could prevent proper solder flow.

3.5 Internal Void Analysis

Analyzing the sequence of images provided by CT scans of the solder joints provides two sets of data.

One is a graph of the void fraction for each image, which shows the distribution of voids within a solder 

joint. The second set of data is the result of integrating the void volume and total volume of the joint in 

the soldered fillet, annular, and flowed fillet regions, and using those data to find the void volume fraction 

in each region and for the entire joint. The first part of this section will present typical results of the 

distribution of voids within a joint for each solder and flux type and gravity level (reduced and normal).

The second section will present the integrated void volume fraction for each joint.

The data in Figure 18 and Figure 19 show the total joint area for each slice and the void area for each 

slice, respectively, for a 60% tin-40% lead, flux cored solder joint formed in reduced gravity. These data 

are representative of the general trends seen in all the analyzed joints, and illustrate the process of 

analyzing the data. The “Position Along Joint” begins with the first instance of solder on the soldered 

fillet, and progresses along the lead towards the circuit board. Red vertical lines on the graph indicate the 

region where the widening fillet transitions to the constant area of the annular region, which combined 

with the effects of plating on the circuit board make analysis in this region difficult. The data in Figure 18
NASA/TM—2012-217119 19

shows how the fillets increase in size along the lead, reaching a maximum at the circuit card plating 

surface. The opposite trend is seen in the flowed fillet, as expected. The annular region has a relatively 

constant area, which is expected since the circuit card through-hole itself has a constant area. Figure 19

shows the void area for each slice along the solder joint, demonstrating how the voids can appear in

clusters, and grow in size to a maximum, then decrease in size. The slice void fraction is the ratio of the 

void area to the total area for each slice, or data point in Figure 18 and Figure 19, respectively. The total 

joint volume is the integrated area under the curves in Figure 18, while the total void volume is the 

integrated area under the curves in Figure 19. The ratio of total void volume to total joint volume is 

reported later as the void volume ratio.

Figure 20 shows the void fraction distribution in a typical joint formed in reduced gravity using 60% 

tin-40% lead solder with a rosin flux core, plotting the image or slice void fraction as a function of 

distance along the joint. The results presented in Figure 20 are typical for other joints with 60% tin-40% 

lead flux cored solder formed in reduced gravity. The majority of voids form in the annular region, and 

usually show growing and shrinking void fractions as new voids form, grow to a maximum, then begin 

shrinking. The void fraction in this region also typically has a minimum, non-zero level as voids are 

always present in some amount for each location within the joint. The fillets in this, and similar, joints 

have smaller void fractions than the annular region of the joint. The annular region has several areas 

where the void fraction grows to a maximum then decreases, while the fillets typically have only one such 

area.

Position Along Joint (mm)

Figure 18.—Slice total area along a joint formed in reduced gravity using 60% tin-40% lead flux cored solder 

wire (Joint A29).

0

2

4

6

8

10

12

14

16

18

20

0 0.5 1 1.5 2 2.5 3 3.5

Slice Total Area (mm2)

 

Soldered Fillet 

Total Volume = 3.2 

mm3

Annular Region Total Volume = 6.5 

mm3

Flowed Fillet Total Volume = 2.3 mm3

Joint total Volume = 12.0 mm3

Plating Plating
NASA/TM—2012-217119 20

Position Along Joint (mm)

Figure 19.—Slice void area along a joint formed in reduced gravity using 60% tin-40% lead flux cored 

solder wire (Joint A29).

Position Along Joint (mm)

Figure 20.—Slice Void Fraction along the interior of a joint formed in reduced gravity with 60% tin-40% 

lead, rosin flux cored solder (Joint A29).

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Area (mm2)

 

Plating Plating

Soldered Fillet Void 

Volume = 0.1 mm3

Annular Region Void 

Volume = 0.9 mm3

Flowed Fillet Void Volume = 0.2 mm3

Total Joint Void Volume = 1.2 mm3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 10.2%

Soldered Fillet Void 

Volume Fraction = 

4.0%

Through Hole Void Volume Fraction = 

14.3%

Flowed fillet Void Volume Fraction = 7.0% 
NASA/TM—2012-217119 21

Figure 21 shows the void fraction distribution for a solder joint formed in normal gravity with the 

same 60% tin-40% lead rosin flux cored wire as shown in Figure 20. As was typical when comparing 

joints formed in normal gravity to those formed in reduced gravity, the normal gravity case presented 

fewer internal voids than in the reduced gravity cases. The results in the case shown indicate a larger void 

fraction in the normal gravity soldered fillet than in the one formed in reduced gravity, but variation from 

joint to joint makes this difficult to conclusively demonstrate. The large void fraction at the top of the

soldered fillet (small “Position Along Joint” values) is unusual for the solder joints studied in this 

experiment.

The data in Figure 22 shows the void fraction distribution in a solder joint formed with eutectic solder 

wire with a rosin flux core in reduced gravity. The distribution of voids in this joint is typical for other 

joints formed in reduced gravity with this solder wire or with the 60% tin-40% lead solder wire. The 

annular region has a larger void volume fraction, and maximum slice void fraction, than in the fillets, and 

the distribution of voids in each section tends to be random. The distribution again shows regions where 

the void fraction, and the number and size of voids, increases to a maximum, then falls, with the cycle 

repeating in the annular region. 

Position Along Joint (mm)

Figure 21.—Slice Void Fraction along the interior of a joint formed in normal gravity with 60% tin-40% 

lead, rosin flux cored solder (Joint GA6).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 5.2%

Soldered Fillet 

Void Volume 

Fraction = 7.9%

Annular Region Void Volume Fraction = 5.9% Flowed Fillet Void Volume Fraction = 3.4%
NASA/TM—2012-217119 22

Position Along Joint (mm)

Figure 22.—Slice Void Fraction along the interior of a joint formed in reduced gravity with eutectic, rosin 

flux cored solder (Joint F9).

The graph in Figure 23 shows the void fraction distribution for a joint formed in reduced gravity with 

a solid 60% tin-40% lead solder wire and external liquid flux. As with other cases, the annular region had 

the largest amount of voids, both overall and as a maximum for a particular image or slice. This joint, as 

with others, has a larger amount of voiding in the annular region than in the fillets, with regions where the 

amount and/or size of the voids grows towards a maxima, then decreases, only to increase at a point 

further along in the joint. 

Figure 24 presents the void fraction distribution in a joint formed in normal gravity, with solid 60% 

tin-40% lead solder with an external liquid flux. As is typical with these joints, the overall void volume 

fraction, and the void volume fraction for the joint as a whole, is very low compared to all other solder 

and flux types. Also typical for these joints, each region only shows one area where a void or small 

number of voids forms, grows, then shrinks, with the rest of the joint virtually free of voids. Void fraction 

distribution for all joints analyzed are shown in Appendix B.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 9.4%

Soldered Fillet Void 

Volume Fraction = 

4.7%

Annular Region Void Volume Fraction = 11.5% Flowed Fillet Void Volume 

Fraction = 9.9%
NASA/TM—2012-217119 23

Distance Along Soldered Joint (mm)

Figure 23.—Slice Void Fraction along the interior of a joint formed in reduced gravity with 60% tin-40% 

lead solder wire, external liquid rosin flux (Joint K23).

Position Along Joint (mm)

Figure 24.—Slice Void Fraction along the interior of a joint formed in normal gravity with 60% tin-40% 

lead solder wire, external liquid rosin flux (Joint GC3).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Volume Void 

Fraction = 9.1%

Plating Plating

Soldered Fillet Void 

Volume Fraction = 8.2%

Annular Region Void Volume Fraction = 13.5% Flowed Fillet Void Volume 

Fraction = 6.1%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 2.1%

Soldered Fillet Void Volume 

Fraction = 2.5 %

Annular Region Void Volume Fraction = 1.9 % Flowed Fillet Void Volume Fraction 

= 1.7 %
NASA/TM—2012-217119 24

After analyzing individual images from the joints, the statistics for each solder and flux combination, 

in both reduced and normal gravity, was analyzed. Table 13 through Table 17 present the void volume 

fraction in the soldered fillet, annular region, and flowed fillet for each joint, as well as the overall void 

volume fraction for that joint. The tables also include the average and standard deviation of the void 

volume fraction for each joint region, providing an overall metric on the internal voiding typical for a 

solder and flux as well as the variation in voiding from joint to joint. The first of these tables, Table 13, 

shows the void volume fractions for joints produced in microgravity with 60% tin-40% lead rosin flux 

cored solder. These results show quite a bit of variation in void volume fraction from joint to joint, 

demonstrated by the large standard deviations, relative to the average values, of the void volume 

fractions. In all cases shown in Table 13, the annular region had a larger void volume fraction than either 

of the fillet regions.

Table 14 includes the void volume fraction results for solder joints formed in normal gravity with 

60%tin-40% lead rosin flux cored solder. Overall, total void volume fraction for these joints is smaller 

than the void volume fraction for joints formed in reduced gravity using the same solder and flux type.

The distribution of voids within the joint has also changed, with more voids in the soldered fillet and 

fewer voids in the annular region for normal gravity joints, compared to those in joints formed in reduced 

gravity. The graphs of individual slice void fraction show this trend in some cases, but the large variation 

from test to test in both gravity regimes makes a definite conclusion difficult.

TABLE 13.—VOID VOLUME FRACTION FOR REDUCED GRAVITY,

60% TIN-40% LEAD ROSIN FLUX CORED SAMPLES

Solder joint Soldered fillet 

void volume 

fraction 

(%)

Annular region 

void volume 

fraction 

(%)

Flowed fillet void 

volume fraction 

(%)

Void volume 

fraction 

(%)

A13 1.3 39.5 4.4 15.5

A14 15.1 45.2 16.1 23.8

A25 1.7 23.3 5.8 13.5

A29 4.0 14.3 7.0 10.2

A30 2.4 19.6 12.4 12.6

B6 3.0 9.2 1.8 4.8

B8 3.8 21.7 8.4 9.4

B13 3.3 29.9 3.2 12.8

B21 2.3 8.8 2.8 4.7

B29 4.0 21.5 5.2 11.0

Average void 

volume fraction

4.1 23.3 6.7 11.8

Standard deviation 4.0 12.0 4.5 5.5

TABLE 14.—VOID VOLUME FRACTION FOR NORMAL GRAVITY, 

60% TIN-40% LEAD ROSIN FLUX CORED SAMPLES

Solder joint Soldered fillet 

void volume 

fraction 

(%)

Annular region 

void volume 

fraction 

(%)

Flowed fillet void 

volume fraction 

(%)

Void volume 

fraction 

(%)

GA1 1.8 18.4 4.1 11.0

GA4 15.3 10.2 13.4 11.4

GA5 7.2 12.5 0.7 8.1

GA6 7.9 5.9 3.4 5.2

GA7 3.7 5.0 0.7 3.3

Average void volume 

fraction

7.2 10.4 4.5 7.8

Standard deviation 5.2 5.4 5.2 3.5
NASA/TM—2012-217119 25

TABLE 15.—VOID VOLUME FRACTION FOR REDUCED GRAVITY,

EUTECTIC ROSIN FLUX CORED SAMPLES

Solder joint Soldered fillet 

void volume 

fraction 

(%)

Annular region 

void volume 

fraction 

(%)

Flowed fillet void 

volume fraction 

(%)

Void volume 

fraction 

(%)

E26 3.6 8.8 7.1 6.6

F6 2.7 28.9 6.7 12.9

F9 4.7 11.5 9.9 9.4

F11 4.2 26.5 7.7 17.1

F13 0.8 7.4 3.2 4.3

F31 9.5 10.2 19.7 13.2

F32 1.2 13.8 1.3 4.4

Average void volume 

fraction

3.8 15.3 7.9 9.7

Standard deviation 2.9 8.7 5.9 4.9

TABLE 16.—VOID VOLUME FRACTION FOR REDUCED GRAVITY,

60% TIN-40% LEAD EXTERNAL LIQUID ROSIN FLUX SAMPLES

Solder joint Soldered fillet 

void volume 

fraction 

(%)

Annular region 

void volume 

fraction 

(%)

Flowed fillet void 

volume fraction 

(%)

Total void volume 

fraction

(%)

J19 3.8 26.5 7.3 10.9

J20 1.0 3.2 1.0 1.7

J22 1.4 9.3 2.5 4.0

J28 1.9 10.7 2.2 4.9

J29 12.1 17.5 3.8 11.3

K7 3.5 8.0 3.5 4.9

K14 4.0 18.1 12.4 10.7

K22 6.4 21.9 3.3 9.4

K23 8.2 13.5 6.1 9.1

K25 0.9 7.4 6.4 4.5

Average void volume 

fraction

4.3 13.6 4.9 7.1

Standard deviation 3.6 7.3 3.3 3.5

TABLE 17.—VOID VOLUME FRACTION FOR NORMAL GRAVITY, 

60% TIN-40% LEAD EXTERNAL LIQUID ROSIN FLUX SAMPLES

Solder joint Soldered fillet 

void volume 

fraction 

(%)

Annular region 

void volume 

fraction 

(%)

Flowed fillet void 

volume fraction 

(%)

Void volume 

fraction 

(%)

GC3 2.5 1.9 1.7 2.1

GC6 3.6 10.9 1.1 5.3

GC7 3.1 1.2 0.6 1.8

GC8 0.1 0.8 0.6 0.5

GC10 0.9 10.5 2.9 4.2

Average void volume 

fraction

2.0 5.1 1.4 2.8

Standard deviation 1.5 5.2 1.0 1.9

The void volume fraction data for eutectic, rosin flux cored samples formed in reduced gravity are 

shown in Table 15. As with the 60% tin-40% lead solder joint results shown in Table 13, the eutectic joint 

samples had a wide range of void volume fractions in all three joint regions, as well as for the joints as a 

whole. The eutectic solder joints showed less void formation in the soldered fillet and annular regions, but 
NASA/TM—2012-217119 26

somewhat more void formation in the flowed fillet, than the 60% tin-40% lead joints. Overall, the eutectic 

solder showed less void formation.

Due to time constraints, the SoRGE team was unable to obtain normal gravity samples using the 

eutectic solder with a rosin flux core. The team decided to use samples produced in normal gravity with 

this solder and flux combination from previous work (Ref. 4), and use this data as a basis of comparison.

The previous tests produced two analyzed solder joints, and report a “total voiding” measure by summing 

the void area in each image describing the entire joint, and dividing by the sum of the total area in each 

image. This is similar, but not equal, to the integration method used for the SoRGE data, and will provide 

a relative comparison for the results. The “total voiding” for these earlier samples are 0.2 and 0.6 percent, 

and are significantly smaller than the void volume fractions seen in this work.

The data included in Table 16 shows the void volume fraction for joints formed in reduced gravity 

using 60% lead-40% tin solder with an external liquid flux, used in previous work (Ref. 4) as a method 

for reducing internal voids. As with the other solder and flux combinations formed in reduced gravity, the 

majority of voids are found in the annular region of the joint in most of these cases, with a high degree of 

variability in void volume fraction from joint to joint, both in the three sub-sections of the joint as well as 

in the whole joint. The average void volume fraction for the whole joint is smaller for these cases using 

external flux than the other cases using a flux cored solder.

The results from forming solder joints in normal gravity using 60% tin-40% lead solder with an 

external liquid flux are shown in Table 17. These results show a large reduction in void formation in all 

three regions of the joint, as well as for the joint overall, compared to all other results. These normal 

gravity results show that most of the voids formed in the annular region, and that the soldered fillet 

developed more internal voids than the flowed fillet, in most cases. As with the other cases, the results 

have a large standard deviation and therefore large variability in void formation from joint to joint.

4.0 Discussion and Recommendations

A key finding of the SoRGE SDTO is the capability of crew members to perform soldering 

operations, and potentially electronics repair operations, in the reduced gravity, closed environment of a 

space vehicle or habitat. As the data in Table 2 through Table 7 show, the astronaut was able to form 

solder joints that pass NASA standards with all the solder and flux types, though all the solder operations 

generated fewer passing joints than expected. The results of interviews and inspections provide some 

reasons for these results. The astronaut did not receive training prior to the mission, and did not have any 

previous experience to use as a reference. While the astronaut stated, and the video record shows, that the 

written procedures and training video were helpful, some additional training and experience prior to 

launch would have provided a better foundation for performing the soldering work. Many of the 

difficulties seen in the video record and in the inspection of the circuit boards point to a lack of practice 

and instruction prior to the SoRGE operations, not to difficulties inherent to operating in reduced gravity.

Practice boards and other “on the job” training would also have been helpful, allowing the astronaut to 

gain experience prior to performing the soldering work. The astronaut also commented that contact with a 

ground support team would have been helpful, to provide pointers or answer questions as problems arose, 

or feedback based on previous work for techniques to try or to reinforce good practices.

Another area where the astronaut encountered difficulty was in the tools available. The SoRGE team 

did not expect the damaged soldering iron tip in the U.S. Soldering Kit, and while the tip was able to melt 

solder and form useful joints, it is not known how this damaged tip affected the crew’s performance. A 

second difficulty mentioned by the crew was visibility. This difficulty manifested in two ways. First, the 

soft sides of the MWA Containment Area were difficult to see through, due to many wrinkles in the soft 

sides of the Containment Area due to unpacking, packing, and storing in a confined space. This left only a 

small view port for direct viewing access into the Containment Area. A second problem was 

magnification. While the Containment Area required a larger distance between the crew and the joint on 

the circuit board than normally found in work in normal gravity, the joint size itself is small enough to 

warrant some magnification, if only to improve the comfort of the person performing the work. One 
NASA/TM—2012-217119 27

technique developed by the crew which alleviated both the visibility and magnification problems was to 

use the viewfinder screen on the video camera as a magnification aid, and to use this screen to see the 

soldering process in real time.

Another issue affecting the joint inspection results is the solder and flux combinations used. As the 

comments from the crew and the results presented in Table 2 through Table 7 show, it was more difficult 

to form solder joints using the solid solder wire with external liquid flux than with flux cored solder. Use 

of liquid flux is more difficult because once activated, by heating the joint area with the soldering iron, 

the flux will lose effectiveness with additional time and heat, making the application of solder critical.

Another difficulty is the liquid flux may not wet all the areas where solder must wet and flow to form a 

joint, such as into or through a through-hole or onto the plating on the flowed fillet side of the circuit 

board. Flux cored solder wires do not experience this problem, because the flux is mixed with the liquid 

solder and flows with the solder, preparing the surface as it flows.

One reason to use an external liquid flux, despite the difficulties found soldering with this material, is 

a reduction in void formation. As the data in Table 13 through Table 17show, the use of an external liquid 

flux lead to the smallest values of void volume fraction compared to other solder and flux combinations in 

reduced and normal gravity. The amount of voids present in a joint decreased when using a eutectic, flux 

cored solder compared to the 60% tin-40% lead cored solder case in reduced gravity. The void volume 

fraction was further reduced for joints with the solid 60% tin-40% lead solder with an external liquid flux.

While these average void volume fraction data are encouraging, it should be noted that, from joint to 

joint, the void volume fraction varies quite a bit, and the performance of the person soldering, for 

inexperienced and experienced technicians (or crew members), can affect the presence of voids within a 

solder joint.

The results of the joint analysis also point out some gravitational effects on the formation of solder 

joints. First, the amount of voiding in the joints, measured by the void volume fraction, decreased for 

joints formed in normal gravity compared to those formed in reduced gravity with the same solder and 

flux combination. The SoRGE team has two hypotheses for this result. First, the crew may exhibit 

differences in soldering technique from reduced to normal gravity, and the improved techniques help 

alleviate void formation. Examination of the soldering techniques used during the flight by the crew, as 

well as after the flight during the production of ground samples, does not reveal any substantive 

differences in soldering technique, in terms of iron placement, amount of time the iron tip is in contact 

with the joint area, or amount or rate of solder wire fed into the joint. Since the crew did not show 

improved soldering techniques between normal and reduced gravity, there must be another explanation 

for the increase in voids. This second hypothesis is a gravitational effect where buoyancy in normal 

gravity forces the trapped gas bubbles within the still-liquid solder joint to escape during heating, but the 

absence of this force in reduced gravity likely helps to trap the gas bubbles within the solder and leads to 

an increase in void formation.

The void volume fraction results for the three sections of a solder joint supports the hypothesis that 

buoyancy, or the absence of it, affects the formation and presence of void defects in the solder joint. In the 

case of 60% tin-40% lead solders, with either a flux cored wire or solid wire with external liquid flux, the 

void volume fraction decreased in the through-hole section of the joint when comparing normal gravity 

results to reduced gravity results. Further, the ratio of void volume fraction of the soldered fillet to the 

through-hole region increased in normal gravity cases compared to reduced gravity cases. This trend can 

be seen in many, though not all, of the graphs of slice void fraction to joint position, found in the 

Appendix. This trend seems to indicate that the gas bubbles evolved within the liquid solder while 

forming the joint are escaping by travelling upward through the joint from the through-hole region, and 

perhaps the flowed fillet, up to the soldered fillet and escaping to the atmosphere when performing work 

in normal gravity. (Recall that the gravity vector, in normal gravity operations, points down from the 

soldered fillet to the flowed fillet.) This difference in void distribution with respect to gravity seems to 

indicate a buoyancy effect, but more analysis and testing is required to understand the role of buoyancy 

and other forces, such as surface tension, within a molten solder joint in various gravitational

environments.
NASA/TM—2012-217119 28

Future work, specifically for the SoRGE program, is to complete work on the remaining six kits (two 

for each solder and flux type) on the ISS. Increasing the amount of data available will help improve the 

statistical validity of these results, and provide a measure of the differences between operators. The future 

work will also provide an opportunity to work with a new soldering iron tip, as the current tip may have 

been damaged prior to the SoRGE work. Future operations may provide an opportunity for training the 

crew in soldering prior to launch, which will make the operations easier for the crew and return a larger 

number of solder joints. Finally, future experiments beyond SoRGE should explore the feasibility and 

improvements required for performing other electronics repair tasks, including removing conformal 

coating, removing and replacing other types and sizes of components, repairing damage to a circuit board, 

and other tasks that simulate repairs a future crew may face.

4.1 Recommendations

As the results of this work show, it is feasible to perform soldering in reduced gravity, which is a key 

step in performing electronics repairs during a space mission. Enabling an electronics repair capability

will help alleviate launch mass and spares storage issues, as the ability to perform repairs allows mission 

planners to stock components, parts, circuit boards, and tools rather than full sized replacement ORUs. A 

repair capability also provides flexibility for crew members and ground support teams to recover from 

unexpected failures, or to take advantage of unexpected opportunities if they arise. NASA should perform 

future studies and planning to enable a repair capability, some of which have been highlighted in SoRGE.

Based on the results of the SoRGE testing performed to date, NASA should provide crews with a 

eutectic, flux cored solder wire for general electronics repairs in future missions. The eutectic solder wire 

used here was easy to work with, compared to the solid solder wire with external liquid flux, returning 

many solder joints that passed the NASA standards (Ref. 6) as well as joints that did not pass but were 

functional. Joints formed with the eutectic solder wire generally presented fewer internal voids than those 

formed with the 60% tin-40% lead flux cored solder as well. While specific applications may require 

more extensive void mitigation, and therefore other solder, flux, and solder techniques, a flux cored 

eutectic solder wire presents a compromise between void formation and ease of use appropriate for most 

repair tasks. Additionally, NASA should determine what repairs call for additional void mitigation 

techniques and materials, such as the use of solid solder wire and external liquid flux. In industry the 

amount of acceptable voiding depends on the function and criticality of the overall product, and each 

manufacturer must decide this on their own, with very few “rules of thumb” to guide the decision.

To make an electronics repair capability a success, NASA should increase the training available to 

crew members. This can include increased training prior to the mission, with refresher courses to maintain 

and improve skills with structured practice. NASA may also consider selecting a crew member with 

experience in working with and repairing electronics to lead this effort during a mission, while still 

providing other crew members additional training. The SoRGE work has shown that a training video is 

very useful for the crew, and ground support teams should provide training videos for expected activities 

and have the capability to produce and transmit new ones as the need arises. The crew should also have 

access to practice materials—circuit boards and components—during a mission both to maintain

competence as well as to practice a repair prior to performing it. An additional aspect of this training is 

determining the criteria for acceptable and unacceptable repair outcomes in terms of inspections and 

testing. While NASA has standards in place (Ref. 6, for example) they reflect work performed in wellequipped manufacturing and laboratory settings which may not be available to a crew performing a repair 

in a space vehicle. The existing standards and tests also include circumstances applicable for the original 

unit, but not for the repaired item. For example, manufacturers must test circuit boards and electronic 

assemblies to survive launch stresses and vibrations. A repair to that unit on the ISS may not require such 

testing; it is already in orbit, and will never experience launch stresses.

NASA should also pursue an improvement to the tools available to the crew for performing 

electronics repairs. These include small tools, such as tweezers and cutters and other electronics hand 

tools, for grasping and manipulating small components. The crew should also have access to a better 
NASA/TM—2012-217119 29

soldering tool. This includes a soldering wand with temperature control and hotter operating 

temperatures, which will improve the range of components that may be worked on, alleviate heat loss 

through the circuit card conducting layers and heat sinks, and make the soldering tasks easier for the 

crew. The electronics repair tool kit should also include a wide variety of soldering iron tips. The 

soldering iron tips are designed for removing and replacing components of specific size and shape, from 

resistors to chips, and make these work tasks easier for the crew. The Containment Area should also be 

redesigned, improving the visibility of the work within the area, and perhaps making the area smaller and 

easier to work within, as the astronaut performing SoRGE work suggested. The crew should also have 

access to magnification aids, such as magnifying visors of different powers, a microscope mounted on a 

swivel or mounting arm in the Containment Area and MWA, and/or video magnification improving the 

method used by the crew during SoRGE operations. These tools, particularly the magnification 

improvements, will not only aid in the removal and replacement of electronics parts, but will also prove 

useful in other repair or operational tasks.

An area of electronics repair not included in the SoRGE work is the diagnosis and testing of 

electronics. These steps are necessary to isolate a fault, not only to find the components requiring 

replacement but to trace the failure to a root cause, allowing the crew and ground support teams to 

alleviate that risk and help prevent future failures. Additionally, the testing of a circuit after a repair must 

occur to ensure that the repair was successful, that no additional damage occurred during the repair, and 

that the circuit will function and not cause further damage when returned to service. While these aspects 

are outside the scope of SoRGE, they are necessary parts to enabling an electronics repair capability.

More details regarding a concept for diagnostics and test capabilities aboard a space vehicle proposed by 

the CLEAR team can be found in other work (Ref. 9).

While SoRGE is one of the first steps to providing an electronics repair capability, it does show that 

these repairs are feasible, and with further work NASA missions to the ISS and beyond can benefit from 

this repair capability.
NASA/TM—2012-217119 30
NASA/TM—2012-217119 31

Appendix A.—Tables of Board Visual Inspection Results

TABLE 18.—INSPECTION RESULTS FROM 60% TIN-40%LEAD, 

ROSIN FLUX CORED SOLDER IN REDUCED GRAVITY, 

BOARD A, SOLDERED FILLET

Joint 

number

Pass/fail Notes

1 Fail Insufficient solder, poor wetting, void

2 Fail Insufficient solder, poor wetting, void

3 Fail Very little solder on lead only

4 Fail No solder

5 Pass

6 Fail Very little solder on lead only, spike

7 Pass

8 Fail Very little solder on lead only, spike

9 Pass (-) Solder drag

10 Pass

11 Fail Solder on lead only

12 Pass (-) Wetting on pad

13 Pass

14 Pass

15 Fail Very little solder on lead only

16 Pass

17 Pass (-) Pit

18 Pass

19 Fail Solder on lead only, spike

20 Fail Poor wetting, drag

21 Fail Poor wetting, void

22 Fail Very little solder on lead only

23 Pass

24 Pass

25 Pass

26 Fail Poor wetting, void

27 Fail Very little solder on pad

28 Pass

29 Pass (-)

30 Pass

31 Fail Very little solder on lead only, spike

32 Fail Little solder on lead only, spike
NASA/TM—2012-217119 32

TABLE 19.—INSPECTION RESULTS FROM 60% TIN-40%LEAD, 

ROSIN FLUX CORED SOLDER IN REDUCED GRAVITY, 

BOARD A, FLOWED FILLET

Joint 

number

Pass/fail Notes

1 Fail No fillet, poor wetting in through hole

2 Fail No fillet, no solder in through hole

3 Fail No fillet, no solder in through hole

4 Fail No fillet, no solder in through hole

5 Fail No fillet, no solder in through hole

6 Fail No fillet, no solder in through hole

7 Fail No fillet, poor wetting in through hole

8 Fail No fillet, no solder in through hole

9 Fail No fillet, no solder in through hole

10 Fail No fillet, poor wetting in through hole

11 Fail No fillet, no solder in through hole

12 Pass

13 Pass

14 Pass

15 Fail No fillet, no solder in through hole

16 Fail No fillet, poor wetting in through hole

17 Fail No fillet, poor wetting in through hole

18 Fail No fillet, poor wetting in through hole

19 Fail No fillet, no solder in through hole

20 Fail No fillet, poor wetting in through hole

21 Fail No fillet, poor wetting in through hole

22 Fail No fillet, no solder in through hole

23 Fail No fillet, poor wetting in through hole

24 Fail No fillet, poor wetting in through hole

25 Pass

26 Fail No fillet, poor wetting in through hole

27 Fail No fillet, no solder in through hole

28 Pass

29 Pass

30 Pass

31 Fail No fillet, no solder in through hole

32 Fail No fillet, no solder in through hole
NASA/TM—2012-217119 33

TABLE 20.—INSPECTION RESULTS FROM 60% TIN-40%LEAD, 

ROSIN FLUX CORED SOLDER IN REDUCED GRAVITY, 

BOARD B, SOLDERED FILLET

Joint 

number

Pass/fail Notes

1 Fail Excessive solder

2 Pass Burnt flux

3 Fail Excessive solder

4 Fail Spike

5 Pass

6 Pass

7 Pass

8 Pass (-) Little spikes

9 Pass (-) Borderline excessive solder, solder drag

10 Pass

11 Pass

12 Pass

13 Pass

14 Pass (-) Spike

15 Fail Big spike, drag

16 Fail Big spike, drag

17 Fail Spike

18 Pass (-) Borderline excessive solder

19 Pass

20 Fail Poor wetting, void, spike

21 Pass

22 Fail Solder on lead only, spike

23 Pass (-) Spike

24 Fail Big spike

25 Pass Borderline excessive solder

26 Fail Spike

27 Fail Spike

28 Fail Excessive solder, spike

29 Pass

30 Pass

31 Fail Solder on lead only, spike, burnt flux

32 Fail Spike
NASA/TM—2012-217119 34

TABLE 21.—INSPECTION RESULTS FROM 60% TIN-40%LEAD, 

ROSIN FLUX CORED SOLDER IN REDUCED GRAVITY, 

BOARD B, FLOWED FILLET

Joint 

number

Pass/fail Notes

1 Pass

2 Fail No fillet, poor wetting in through hole and lead

3 Pass

4 Pass (-)

5 Fail Partial fillet, poor wetting in through hole and lead

6 Pass

7 Fail No fillet

8 Pass

9 Pass

10 Fail Partial fillet, poor wetting in through hole and lead

11 Fail No fillet

12 Fail Reflow line of solder on periphery of pad

13 Pass

14 Fail No fillet

15 Pass

16 Pass

17 Pass

18 Fail No fillet

19 Fail Partial fillet, poor wetting in through hole and lead

20 Fail No fillet, poor wetting in through hole and lead

21 Pass

22 Fail No fillet, no solder in through hole

23 Fail No fillet

24 Pass

25 Fail No fillet, no solder in through hole

26 Pass

27 Pass

28 Pass

29 Pass

30 Fail No fillet

31 Fail No fillet, no solder in through hole

32 Fail No fillet
NASA/TM—2012-217119 35

TABLE 22.—INSPECTION RESULTS FROM EUTECTIC, 

ROSIN FLUX CORED SOLDER IN REDUCED 

GRAVITY, BOARD E, SOLDERED FILLET

Joint 

number

Pass/fail Notes

1 Pass (-) Little spike

2 Fail Spike

3 Pass

4 Fail Spike

5 Fail Spike

6 Fail Spike

7 Fail Spike

8 Fail Spike, excessive solder

9 Fail Spike

10 Fail Spike

11 Fail Spike

12 Fail Spike

13 Fail Spike

14 Fail Spike

15 Fail Spike

16 Fail Solder on lead only, spike

17 Fail Solder on lead only, spike

18 Fail Spike

19 Fail Solder on lead only, spike

20 Fail Spike

21 Fail Spike

22 Fail No solder, flux only

23 Pass

24 Fail Very little solder on pad only

25 Pass

26 Pass

27 Pass

28 Pass

29 Fail Spike

30 Pass (-) Little spike

31 Fail Spike

32 Fail Solder on lead only, spike
NASA/TM—2012-217119 36

TABLE 23.—INSPECTION RESULTS FROM EUTECTIC, 

ROSIN FLUX CORED SOLDER IN REDUCED 

GRAVITY, BOARD E, FLOWED FILLET

Joint 

number

Pass/fail Notes

1 Pass No Notes

2 Fail No fillet

3 Pass (?) No fillet, may be absolute minimum (after cleaning)

4 Pass

5 Pass

6 Pass

7 Pass

8 Pass

9 Fail No fillet, no solder in plated through hole

10 Fail No fillet, poor wetting in through hold and lead

11 Pass

12 Fail No fillet, poor wetting in through hole and lead

13 Fail No fillet, may be absolute minimum

14 Fail No fillet, poor wetting in through hole and lead

15 Pass

16 Fail No fillet, no solder in through hole

17 Fail No fillet, no solder in through hole

18 Fail No fillet, no solder in through hole

19 Fail No fillet, no solder in through hole

20 Fail No fillet, poor wetting in through hole and lead

21 Pass (?) May be OK (minimum) (cleaning)

22 Fail No fillet, no solder in through hole

23 Pass (?) May be OK (minimum) (cleaning)

24 Fail No fillet, no solder in through hole

25 Pass (?) May be OK (minimum) (cleaning)

26 Pass

27 Pass

28 Fail No fillet, poor wetting through hole and lead

29 Fail No fillet, poor wetting through hole and lead

30 Pass

31 Pass - Wetting on pad

32 Fail No fillet, no solder in through hole and lead
NASA/TM—2012-217119 37

TABLE 24.—INSPECTION RESULTS FROM EUTECTIC, 

ROSIN FLUX CORED SOLDER IN REDUCED 

GRAVITY, BOARD F, SOLDERED FILLET

Joint 

number

Pass/fail Notes

1 Pass (-) Solder drag

2 Fail Very little solder on lead only, no fillet

3 Pass (-) Small spike

4 Pass

5 Fail Very little solder on lead only with spike, no fillet

6 Pass

7 Fail Spike

8 Pass

9 Pass

10 Pass (-) Spike

11 Pass

12 Pass

13 Pass

14 Pass (-) Spike

15 Fail Very little solder on lead only with spike, no fillet

16 Fail Very little solder on lead only with spike, no fillet

17 Fail Solder ball on lead only, no fillet

18 Fail Solder on lead only, large spike

19 Pass (-) Small spike

20 Pass

21 Fail Poor wetting in hole, no fillet, large spike

22 Pass

23 Pass

24 Fail Solder on lead only, large spike, no fillet

25 Pass

26 Fail Solder on lead only, no fillet, small spike

27 Pass (-)

28 Pass

29 Pass

30 Pass

31 Pass

32 Pass
NASA/TM—2012-217119 38

TABLE 25.—INSPECTION RESULTS FROM EUTECTIC, 

ROSIN FLUX CORED SOLDER IN REDUCED 

GRAVITY, BOARD F, FLOWED FILLET

Joint 

number

Pass/fail Notes

1 Fail Poor wetting, void

2 Fail No fillet, no solder in through hole

3 Fail Blowhole

4 Fail Poor wetting

5 Fail No fillet, no solder in through hole

6 Pass

7 Fail No fillet, poor wetting in through hole

8 Pass

9 Pass

10 Pass

11 Pass

12 Pass

13 Pass

14 Pass

15 Fail No fillet, no solder in through hole

16 Fail No fillet, no solder in through hole

17 Fail No fillet, no solder in through hole

18 Fail No fillet, no solder in through hole

19 Pass

20 Pass

21 Fail No fillet, no solder in through hole

22 Pass (-) Poor wetting, void

23 Pass (-) Re-heat line

24 Fail No fillet, no solder in through hole

25 Pass (-) Poor wetting, void

26 Fail No fillet, no solder in through hole

27 Pass

28 Pass

29 Pass

30 Fail Poor wetting, void

31 Pass

32 Pass
NASA/TM—2012-217119 39

TABLE 26.—INSPECTION RESULTS FROM 60% TIN-40%LEAD SOLDER, 

EXTERNAL LIQUID ROSIN FLUX IN REDUCED 

GRAVITY, BOARD J, SOLDERED FILLET

Joint 

number

Pass/fail Notes

1 Fail Very little solder on lead only

2 Fail Excessive solder, excessive heat, spike

3 Fail Poor wetting

4 Fail Big spike, excessive solder

5 Fail Giant spike, excessive solder

6 Fail Very little solder on lead only, spike

7 Fail Poor wetting, void

8 Fail Little solder on lead only, spike

9 Fail Poor wetting, little spike

10 Fail Excessive solder, overheated, big spike

11 Fail Excessive solder, overheated, big spike

12 Fail Excessive solder, overheated, medium spike

13 Fail Excessive solder, overheated, big spike

14 Fail Solder drag

15 Fail Excessive solder, overheated, small spike

16 Fail Poor wetting, overheated, big spike

17 Fail Excessive solder, overheated, big spike

18 Fail Excessive solder, overheated, medium spike

19 Fail Excessive solder, overheated, small spike

20 Fail Excessive solder, overheated, small spike

21 Fail Solder on lead only, overheated, large spike

22 Fail Overheated, solder drag

23 Fail Poor wetting, overheated, medium spike

24 Fail Excessive solder, overheated, medium spike

25 Fail Excessive solder, overheated, large spike

26 Fail Overheated, small spike

27 Pass (-) Solder drag

28 Fail Solder spike

29 Pass (-) Excessive solder, overheated, drag

30 Fail Excessive solder, overheated, large spike

31 Fail Excessive solder, overheated, large spike

32 Fail Excessive solder, large spike, poor wetting
NASA/TM—2012-217119 40

TABLE 27.—INSPECTION RESULTS FROM 60% TIN-40%LEAD SOLDER, 

EXTERNAL LIQUID ROSIN FLUX IN REDUCED 

GRAVITY, BOARD J, FLOWED FILLET

Joint 

number

Pass/fail Notes

1 Fail No fillet, poor wetting in through hole and lead

2 Pass

3 Fail No fillet, poor wetting in through hole and lead

4 Fail No fillet, poor wetting in through hole and lead

5 Fail No fillet, poor wetting in through hole and lead

6 Fail No fillet

7 Fail No fillet, poor wetting in through hole

8 Fail No fillet, poor wetting in through hole

9 Fail Insufficient solder, poor wetting

10 Pass

11 Pass

12 Pass

13 Fail No fillet, poor wetting in through hole and lead

14 Fail No fillet, poor wetting in through hole and lead

15 Pass

16 Fail No fillet, poor wetting in through hole and lead

17 Fail Insufficient solder, poor wetting

18 Pass

19 Pass

20 Pass

21 Fail No fillet

22 Pass

23 Fail No fillet

24 Fail No fillet, poor wetting in through hole

25 Pass

26 Pass

27 Fail Insufficient solder, poor wetting

28 Pass

29 Pass

30 Pass

31 Pass

32 Fail Insufficient solder, poor wetting
NASA/TM—2012-217119 41

TABLE 28.—INSPECTION RESULTS FROM 60% TIN-40%LEAD SOLDER, 

EXTERNAL LIQUID ROSIN FLUX IN REDUCED 

GRAVITY, BOARD K, SOLDERED FILLET.

Joint 

number

Pass/fail Notes

1 Fail Over heated, excessive solder, spike

2 Fail Over heated, excessive solder, spike

3 Fail Solder on lead only, spike

4 Fail Solder on lead only, spike, overheated

5 Fail Overheated, drag

6 Fail Over heated, poor wetting, excessive solder, spike

7 Fail Over heated, poor wetting, spike

8 Fail Poor wetting, spike, solder bridge between lead and pad

9 Fail Over heated, excessive solder, spike

10 Fail Solder on lead only, spike

11 Fail Overheated, poor wetting, spike

12 Fail Solder on lead only, overheated, spike

13 Fail Overheated, spike

14 Fail Overheated, spike

15 Fail Solder on lead only, spike

16 Fail Solder on lead only, large spike

17 Fail Overheated, excessive solder, spike

18 Fail Poor wetting on lead and pad, insufficient solder, spike

19 Fail Solder on lead only, spike

20 Fail Overheated, drag and spike

21 Fail Solder on lead only, spike

22 Fail Overheated, excessive solder, drag

23 Pass

24 Fail Very little solder on tip of lead only

25 Pass

26 Fail Poor wetting on pad, spike

27 Fail Overheated, spike, excessive solder

28 Fail Solder on lead only, spike

29 Fail Very little solder on lead only, spike

30 Fail Spike

31 Fail Solder on lead only, spike

32 Fail Solder on lead only, spike
NASA/TM—2012-217119 42

TABLE 29.—INSPECTION RESULTS FROM 60% TIN-40%LEAD SOLDER, 

EXTERNAL LIQUID ROSIN FLUX IN REDUCED 

GRAVITY, BOARD K, FLOWED FILLET

Joint 

number

Pass/fail Notes

1 Fail No fillet, poor wetting in through hole and lead

2 Pass

3 Fail No fillet, no solder in through hole

4 Fail No fillet, no solder in through hole

5 Fail Partial fillet, poor wetting of pad, lead

6 Fail No fillet, poor wetting in through hole and lead

7 Pass

8 Fail No fillet, no solder in through hole

9 Pass

10 Fail No fillet, no solder in through hole

11 Fail Partial fillet, poor wetting on pad and lead

12 Fail No fillet, no solder in through hole

13 Fail No fillet, poor wetting in through hole and lead

14 Pass

15 Fail No fillet, no solder in through hole

16 Fail No fillet, no solder in through hole

17 Pass

18 Fail No fillet, no solder in through hole

19 Fail No fillet, no solder in through hole

20 Fail Partial fillet, poor wetting on pad

21 Fail No fillet, no solder in through hole

22 Pass

23 Pass

24 Fail No fillet, no solder in through hole

25 Pass

26 Fail No fillet, poor wetting on lead

27 Fail No fillet, poor wetting on lead

28 Fail No fillet, no solder in through hole

29 Fail No fillet, no solder in through hole

30 Fail Partial fillet, poor wetting on pad and lead

31 Fail No fillet, no solder in through hole

32 Fail No fillet, no solder in through hole
NASA/TM—2012-217119 43

Appendix B.—Graphs of Void Fraction Distribution

Position Along Joint (mm)

Figure 25.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (A13).

Position Along Joint (mm)

Figure 26.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (A14).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Soldered Fillet Void Volume 

Fraction = 1.3%

Annular Region Void 

Volume Fraction = 

39.5%

Flowed Fillet Void Volume Fraction = 

4.4%

Void Volume Fraction = 15.5%

Plating Plating Plating

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Soldered Fillet Void Volume 

Fraction = 15.1 %

Annular Region Void 

Volume Fraction = 45.2 

%

Flowed Fillet Void Volume Fraction = 

16.1%

Void Volume Fraction = 23.8%
NASA/TM—2012-217119 44

Position Along Joint (mm)

Figure 27.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (A29).

Position Along Joint (mm)

Figure 28.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (A30).

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Area (mm2)

 

Plating Plating

Soldered Fillet Void 

Volume = 0.1 mm3

Annular Region Void 

Volume = 0.9 mm3

Flowed Fillet Void Volume = 0.2 mm3

Total Joint Void Volume = 1.2 mm3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 12.6%

Soldered Fillet Void Volume 

Fraction = 2.4%

Annular Region Void Volume Fraction = 19.6% Flowed Fillet Void Volume 

Fraction = 12.4%
NASA/TM—2012-217119 45

Position Along Joint (mm)

Figure 29.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (B6).

Position Along Joint (mm)

Figure 30.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (B8).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Void Volume Fraction = 4.8%

Soldered Fillet Void Volume 

Fraction = 3.0%

Annular Region Void Volume Fraction = 9.2% Flowed Fillet Void Volume 

Fraction = 1.8%

Plating Plating

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 9.4%

Soldered Fillet Void Volume Fraction = 

3.8%

Annular RegionVoid Volume Fraction = 

21.7%

Flowed Fillet Void Volume 

Fraction = 8.4%
NASA/TM—2012-217119 46

Position Along Joint (mm)

Figure 31.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (B13).

Position Along Joint (mm)

Figure 32.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (B21).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 12.8%

Soldered Fillet Void Volume Fraction 

= 3.3%

Annular Region Void Volume Fraction = 

29.9% Flowed Fillet Void Volume 

Fraction = 3.2%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 4.7%

Soldered Fillet Void Volume 

Fraction = 2.3%

Annular Region Void Volume Fraction = 8.8 % Flowed Fillet Void Volume Fraction = 

2.8%
NASA/TM—2012-217119 47

Position Along Joint (mm)

Figure 33.—Slice Void Fraction for a 60% tin-40% lead flux cored, reduced gravity, solder joint (B29).

Position Along Joint (mm)

Figure 34.—Slice Void Fraction for a 60% tin-40% lead flux cored, normal gravity, solder joint (GA1).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 11.0%

Soldered Fillet Void Volume 

Fraction = 4.0%

Annular Region Void Volume Fraction = 21.5%

Flowed Fillet Void 

Volume Fraction = 

5.2%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 11.0%

Soldered Fillet 

Void Volume 

Fraction = 

1.8%

Annular Region Void Volume Fraction = 18.4% Flowed Fillet Void Volume Fraction = 4.1%
NASA/TM—2012-217119 48

Position Along Joint (mm)

Figure 35.—Slice Void Fraction for a 60% tin-40% lead flux cored, normal gravity, solder joint (GA4).

Position Along Joint (mm)

Figure 36.—Slice Void Fraction for a 60% tin-40% lead flux cored, normal gravity, solder joint (GA5).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 11.4%

Soldered Fillet 

Void Volume 

Fraction = 15.3%

Annular Region Void Volume Fraction = 10.2% Flowed Fillet Void 

Volume Fraction = 

13.4%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 8.1%

Soldered Fillet 

Void Volume 

Fraction = 7.2%

Annular Region Void Volume Fraction = 12.5% Flowed Fillet Void Volume 

Fraction = 0.7%
NASA/TM—2012-217119 49

Position Along Joint (mm)

Figure 37.—Slice Void Fraction for a 60% tin-40% lead flux cored, normal gravity, solder joint (GA6).

Position Along Joint (mm)

Figure 38.—Slice Void Fraction for a 60% tin-40% lead flux cored, normal gravity, solder joint (GA7).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 5.2%

Soldered Fillet 

Void Volume 

Fraction = 7.9%

Annular Region Void Volume Fraction = 5.9% Flowed Fillet Void Volume Fraction = 3.4%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 3.3%

Soldered Fillet Void 

Volume Fraction = 

3.7%

Annular Region Void Volume Fraction = 5.0% Flowed Fillet Void Volume 

Fraction = 0.7%
NASA/TM—2012-217119 50

Position Along Joint (mm)

Figure 39.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (E26).

Position Along Joint (mm)

Figure 40.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (F6).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 6.6%

Soldered Fillet Void 

Volume Fraction = 

3.6%

Annular Region Void Volume Fraction = 8.8% Flowed Fillet Void Volume Fraction = 7.1%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 12.9%

Soldered Fillet Void Volume 

Fraction = 2.7%

Annular Region Void Volume Fraction = 

28.9%

Flowed Fillet Void Volume 

Fraction = 6.7%
NASA/TM—2012-217119 51

Position Along Joint (mm)

Figure 41.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (F9).

Position Along Joint (mm)

Figure 42.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (F11).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 9.4%

Soldered Fillet Void 

Volume Fraction = 

4.7%

Annular Region Void Volume Fraction = 11.5% Flowed Fillet Void Volume 

Fraction = 9.9%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 17.1%

Soldered Fillet 

Void Volume 

Fraction = 4.2%

Annular Region Void Volume Fraction = 26.5%

Flowed Fillet Void Volume Fraction =

7.7%
NASA/TM—2012-217119 52

Position Along Joint (mm)

Figure 43.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (F13).

Position Along Joint (mm)

Figure 44.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (F31).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Volume Void Fraction = 4.3%

Soldered Fillet Void 

Volume Fraction = 

0.8%

Annular Region Void Volume Fraction = 7.4% Flowed Fillet Void Volume Fraction = 

3.2%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 13.2%

Soldered Fillet Void Volume 

Fraction = 9.5%

Annular Region Void Volume Fraction = 10.2% Flowed Fillet Void Volume Fraction = 

19.7%
NASA/TM—2012-217119 53

Position Along Joint (mm)

Figure 45.—Slice Void Fraction for a eutectic lead flux cored, reduced gravity, solder joint (F32).

Position Along Joint (mm)

Figure 46.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (J19).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 4.4%

Soldered Fillet Void Volume 

Fraction = 1.2%

Annular Region Fillet Void Volume 

Fraction = 13.8%

Flowed Fillet Void Volume Fraction = 1.3%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 10.9%

Soldered Fillet Void Volume Fraction = 

3.8 % Annular Region Void Volume Fraction = 26.5 %

Flowed Fillet Void Volume 

Fraction = 7.3 %
NASA/TM—2012-217119 54

Position Along Joint (mm)

Figure 47.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (J20).

Position Along Joint (mm)

Figure 48.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (J22).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 1.7%

Soldered Fillet Void Volume 

Fraction = 1.0 %

Annular Region Void Volume Fraction = 3.2 % Flowed Fillet Void Volume 

Fraction = 1.0 %

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 4.0% 

Soldered Fillet Void Volume Fraction = 1.4% Annular Region Void Volume Fraction = 9.3% Flowed Fillet 

Void Volume 

Fraction = 2.5%
NASA/TM—2012-217119 55

Position Along Joint (mm)

Figure 49.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (J28).

Position Along Joint (mm)

Figure 50.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (J29).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 4.9%

Soldered Fillet Void 

Volume Fraction = 1.9%

Annular Region Void Volume Fraction = 10.7% Flowed Fillet Void Volume Fraction 

= 2.2%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 11.3%

Soldered Fillet Void Volume 

Fraction = 12.1%

Annular Region Void Volume Fraction = 17.5% Flowed Fillet Void Volume 

Fraction = 3.8%
NASA/TM—2012-217119 56

Position Along Joint (mm)

Figure 51.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (K7).

Position Along Joint (mm)

Figure 52.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (K14).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 4.9%

Soldered Fillet Void 

Volume Fraction = 3.5%

Annular Region Void Volume Fraction = 8.0 % Flowed Fillet Void Volume 

Fraction = 3.5%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating Total Volume Fraction = 10.7%

Soldered Fillet Void 

Volume Fraction = 4.0% Annular Region Void Volume Fraction = 18.1%

Flowed Fillet Void Volume Fraction = 

12.4%
NASA/TM—2012-217119 57

Distance Along Joint (mm)

Figure 53.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (K22).

Distance Along Soldered Joint (mm)

Figure 54.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (K23).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Volume Void Fraction = 9.4% 

Soldered Fillet Void Volume Fraction = 6.4%

AnnularRegion Void Volume Fraction = 21.9% Flowed Fillet Void 

Volume Fraction = 

3.3%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Volume Void 

Fraction = 9.1%

Plating Plating

Soldered Fillet Void 

Volume Fraction = 8.2%

Annular Region Void Volume Fraction = 13.5% Flowed Fillet Void Volume 

Fraction = 6.1%
NASA/TM—2012-217119 58

Position Along Joint (mm)

Figure 55.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, reduced gravity, solder joint (K25).

Position Along Joint (mm)

Figure 56.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, normal gravity, solder joint (GC3).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Soldered Fillet Void Volume 

Fraction = 0.9%

Annular Region Void Volume Fraction = 7.4% Flowed Fillet Void Volume Fraction 

= 6.4%

Void Volume Fraction = 4.5%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 2.1%

Soldered Fillet Void Volume 

Fraction = 2.5 %

Annular Region Void Volume Fraction = 1.9 % Flowed Fillet Void Volume Fraction 

= 1.7 %
NASA/TM—2012-217119 59

Position Along Joint (mm)

Figure 57.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, normal gravity, solder joint (GC6).

Position Along Joint (mm)

Figure 58.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, normal gravity, solder joint (GC7).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 5.3%

Soldered Fillet Void 

Volume Fraction = 3.6 % Annular Region Void Volume Fraction = 10.9 %

Flowed Fillet Void Volume Fraction 

= 1.1 %

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 1.8%

Soldered Fillet Void Volume 

Fraction = 3.1 %

Annular Region Void Volume Fraction = 1.2 % Flowed Fillet Void Volume 

Fraction = 0.6 %
NASA/TM—2012-217119 60

Position Along Joint (mm)

Figure 59.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, normal gravity, solder joint (GC8).

Position Along Joint (mm)

Figure 60.—Slice Void Fraction for a 60% tin-40% lead, external liquid flux, normal gravity, solder joint (GC10).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 0.5%

Soldered Fillet Void 

Fraction = 0.1 %

Annular Region Void Volume Fraction = 0.8 % Flowed Fillet Void Volume 

Fraction = 0.6 %

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2 2.5 3 3.5 4

Slice Void Fraction

 

Plating Plating

Void Volume Fraction = 4.2%

Soldered Fillet Void Volume 

Fraction = 0.9 %

Annular Region Void Volume Fraction = 10.5 % Flowed Fillet Void Volume Fraction = 2.9 %
NASA/TM—2012-217119 61

References

1. Experimental Investigation of Solder Joint Defect Formation and Mitigation in Reduced Gravity 

Environments. Watson, J.K., Struk, P.M., Pettegrew, R.D., and Downs, R.S. 2007, AIAA Journal of 

Spacecraft and Rockets, pp. 174-182.

2. Yaniec, John S. and Del Rosso, Dominic. JSC Reduced Gravity Program Users Guide. 2005. NASA 

AOD 33899 Rev APCN 1.

3. NASA. OSO Consolidated Tool Page. OB5 Logistics and Maintenance Office, NASA Johnson Space 

Center. [Online] http://mod.jsc.nasa.gov/dx/dx43/Databases/Consolidated_Tool_Page/ToolIndex.html.

4. Imaging and Analysis of Void Defects in Solder Joints Formed in Reduced Gravity Using HighResolution Computed Tomography. Easton, J.W., Struk, P.M., Rotella, A. Reno, NV: AIAA 

Aerospace Sciences Meeting and Exhibit, 2008. AIAA-2008-0824.

5. Rasband, W.S. ImageJ. [Online] U.S. National Institutes of Health, 1997-2009. 

http://rsb.info.nih,gov/ij/.

6. NASA. Soldered Electrical Connections. NASA Technical Standard NASA-STD-8739.3. 1997.

7. YXLON International. YXLON.CT Basics. [Online] http://www.yxlon.com/ct_en/index.html.

8. Chapra, Steven C. and Canale, Raymond P. Numerical Methods For Engineers. New York : McGrawHill, Inc., 1988.

9. Approach to In Situ Component Level Electronics Assembly Repair (CLEAR) for Constellation. 

Oeftering, Richard and Struk, Peter. Pasadena, CA : AIAA, 2009. AIAA-2009-6472.
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4. TITLE AND SUBTITLE

Soldering in a Reduced Gravity Environment (SoRGE) 

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6. AUTHOR(S)

Easton, John, W.; Struk, Peter, M. 

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WBS 431767.04.01.03 

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

Future long-duration human exploration missions will be challenged by constraints on mass and volume allocations available for spare parts. Addressing this challenge will be 

critical to the success of these missions. As a result, it is necessary to consider new approaches to spacecraft maintenance and repair that reduce the need for large replacement 

components. Currently, crew members on the International Space Station (ISS) recover from faults by removing and replacing, using backup systems, or living without the 

function of Orbital Replacement Units (ORUs). These ORUs are returned to a depot where the root cause of the failure is determined and the ORU is repaired. The crew has 

some limited repair capability with the Modulation/DeModulation (MDM) ORU, where circuit cards are removed and replace in faulty units. The next step to reducing the size 

of the items being replaced would be to implement component-level repair. This mode of repair has been implemented by the U.S. Navy in an operational environment and is 

now part of their standard approach for maintenance. It is appropriate to consider whether this approach can be adapted for future spaceflight operations. To this end, the 

Soldering in a Reduced Gravity Environment (SoRGE) experiment studied the effect of gravity on the formation of solder joints on electronic circuit boards. This document 

describes the SoRGE experiment, the analysis methods, and results to date. This document will also contain comments from the crew regarding their experience conducting the 

SoRGE experiment as well as recommendations for future improvements. Finally, this document will discuss the plans for the SoRGE samples which remain on ISS. 

15. SUBJECT TERMS

Soldering; Space maintenance; Astronaut training; Circuit boards; Microgravity; International Space Station; Solders; Space missions 

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