RESEARCH PRESSURE INSTRUMENTATION

FOR

NASA SPACE SHUTTLE MAIN ENGINE

NASA CONTRACT NO. NAS8-34769

MODIFICATION NO. 7

MONTHLY REPORT

GEORGE C. MARSHALL SPACE FLIGHT CENTER

MARSHALL SPACE FLIGHT CENTER, ALABAMA 35812

June 1985

Prepared By:

P.J. ANDERSON, PROGRAM MANAGER

P. NUSSBAUM, TECHNICAL DIRECTOR

G. GUSTAFSON, DEPUTY TECHNICAL DIRECTOR

HONEYWELL INC.

SOLID STATE ELECTRONICS DIVISION

12001 STATE HIGHWAY 55

PLYMOUTH, MN 55441
HONEYWELL INC.

SOLID STATE ELECTRONICS DIVISION

CONTRACT NO. NAS8-34769

RESEARCH OF PRESSURE INSTRUMENTATION FOR NASA SPACE SHUTTLE MAIN ENGINE

Monthly R & D Progress June 1985 Report No. 21

A. Technical Progress and Plans

- See attachment 'A1

B. Schedule

- See attachment 'B1

C. Status of Funds

Total Baseline Plan

Total Funded

LBM

$407,350

$407,350

Cost Incurred to 6/2/85 $312,119

Inception to Date Plan $323,555*

Estimate at Completion $1,062,518**

D. Estimated percent of physical completion: 29% ***

E. At the present time the comparison of the cumulative costs to the percent

of physical completion does reveal a significant variance requiring explanation.

* Per replan baseline strategy.

** Per 2/7/85 cost-to-complete proposal

o Total funding to-date: $407,350

o Cost-To-Complete Recommendation: $655.168

$1,062,518

*** % of estimate at complete
ATTACHMENT 'A1

RESEARCH PRESSURE INSTRUMENTATION

FOR

NASA SPACE SHUTTLE MAIN ENGINE

HONEYWELL, INC.

1.0 Introduction and Objective

The first phase of this contract (Tasks A and B) resulted in a highly

successful demonstration in April 1983 at the MSFC of Honeywell's breadboard feasibility model of a silicon Piezoresistive Pressure Transducer

suitable for SSME applications.

The purpose of Modification No. 5 of this contract is to expand the scope

of work (Task C) of this research study effort to develop pressure instrumentation for the SSME. The objective of this contract (Task C) is to

direct Honeywell's Solid State Electronics Division's (SSED) extensive

experience and expertise in solid state sensor technology to develop prototype pressure transducers which are targeted to meet the SSME performance design goals and to fabricate, test and deliver a total of 10 prototype units.

SSED's basic approach is to effectively utilize the many advantages of

silicon piezoresistive strain sensing technology to achieve the objectives

of advanced state-of-the-art pressure sensors in terms of reliability,

accuracy and ease of manufacture. More specifically, integration of multiple functions on a single chip is the key attribute of this technology

which will be exploited during this research study.

The objectives of this research study will be accomplished by completing

the following major tasks:

1. Transducer Package Concept and Materials Study

Three transducer design concepts will be generated and analyzed

for the SSME application and materials/processes will be defined

for the research prototype transducer design.

2. Silicon Resistor Characterization at Cryogenic Temperatures

The temperature and stress properties of a matrix of ion implanted piezoresistors will be characterized over the temperature range of -320°F to +250°F.

3. Experimental Chip Mounting Characterization

The mechanical integrity of chip mounting concepts will be evaluated over temperature, pressure and vibration.
PAGE TViO

4. Frequency Response Optimization

This task is a paper study which will specify and analyze an

acoustic environment for which transducer frequency response can

be determined and optimized.

5. Prototype Transducer Design, Fabrication, and Test

This major task will use the results generated in Tasks 1

through 4 above to design and develop a research prototype

pressure transducer for the SSME application and will culminate

in the delivery of 10 transducers, 5 each for the ranges of 0 to

600 psia, and 0 to 3500 psia. This task is subdivided into the

following five areas:

- Feasibility Evaluation of Transducer Concept

- Prototype Transducer Design

- Prototype Transducer Fabrication and Test

- Prototype Qualification

- Prototype Delivery.

6. Reports

Honeywell will submit monthly progress reports during the period

of the contract; a final report will be provided at the completion of the contract.

The format of this report will be to discuss the work performed

for this reporting period and the plans for the next reporting

period for each of the major tasks outlined above.

2.0 Work Performed and Plans

2.1 Transducer Package Concept and Materials Study.

This task was completed per plan during January 1984.

2.2 Silicon Resistor Characterization at Cryogenic Temperatures.

This task was completed in May 1984.
PAGE THREE

2.3 Experimental Chip Mounting Characterization

A. Work Performed in June

Revisions were made to the Task 3000 and V-ring stress modeling

reports (These reports are attached to the NASA copy of this

monthly. Attachment C.). The final conclusions to the V-ring stress

modeling are as stated in the April Monthly report. These are that

stresses in the silicon sensor due to the V-ring compression seal are

cause for concern with respect to the capability to calibrate and the

effect of moving the sensor capsule from a calibration housing to a

final housing. Consequently, close attention will be paid to an

experiment planned for the upcoming feasibility sensor build under

which capsules will be moved between housings and the impact on the

(null) reading observed. If this experiment indicates that large,

nonrepeatable stresses cause major null shifts when the capsules are

moved, then the alternative approach of calibrating in a subassembly

of the deliverable housing will be pursued further.

B. Plans for July

The plans are as follows:

- Close this task.

2.4 Frequency Response Optimization

This task was completed per plan in February 1984.

2.5 Temperature Sensor Network Concept Study

This task was deleted when the contract was negotiated.

2.6 Deliverable Transducer Design, Fabrication, and Test.

2.6.1 Fe^g'ihmtY Fyfllufltion of Transducer Concepts

2.6.1.1 Lead Length Reduction

Based on the results reported in January, we do not

expect that we will have to implement this task.
PAGE FOUR

2.6.1.2 Seal Ring Development Phase 1

A. Work Performed In June

Twenty X-750 vented Orings have been ordered from

Fluorcarbon. Our literature search and NASA

Report 202, "Marshall Material Search and Display

System" indicates that A-286 would be less

susceptible to hydrogen embrittlement than X-750.

A quote is being obtained for A-286 V-rings.

B. Plans for July

Order A-286 V-rings.

2.6.1.3 Sea,], Ping Development Pass II

This task will not be opened until test results

indicate there is an issue with the current V-Ring

design/finish which is expected to be resolved by

using one of the designs noted in Section 2.6.1.2.

2.6.1.4 Hermetic Feedthrough Development' P?f?S I

A. Work Performed In June „

The first phase of this task is complete. The

approach followed to process hermetic electrical

feedthroughs yielded hermetic joints. However,

electrical leakage between feedthrough pins was

experienced. The following soldering fixturing

and process methodologies are complete.

1. Cleaning procedures

2. Metallizing procedures

3. Soldering procedures

4. Alignment procedures

Further refinements to the process are planned for

the second phase of the Hermetic Feedthrough

Development. (See Paragraph 2.6.1.5)
PAGE FIVE

2.6.1.5 Hermetic Feedthrouah Development P?gf? II

A. Work performed in June

Failure analysis of assemblies exhibiting

unacceptable current leakage between adjacent

terminal was completed. Cross-sectioning methods

were used. These results indicated the electrical

leakage was due to solder bridging between pins

and not just flux entrapment. It was also

determined that there was very good wetting of the

terminal board metallization by the solder with

filleting at both the top and bottom of the

chamfer. There were also some round voids in the

solder joints that were probably caused by flux

entrapment. These findings indicate that better

alignment of the terminal boards, more space

between the metallized pads, and fluxless

soldering should all be evaluated in Pass II.

Attachment D shows the new metallization pattern

that will increase the space between pads by

approximately 10 mils.

B. Plans for July

Complete Pass II for evaluating the following:

o Improve Alignment Fixturing

o Increase Space Between Feedthrough

Metallization

o Evaluate Fluxless Soldering Using Both

Pb-Ag-Sn and Au-Ge solder,

o Evaluate Thicker Metallization

2.6.1.6 Additional Cryogenic Data

A. Current Status

Test runs on both moderately-doped PN diodes and

500 f\. /O chrome silicon thin film resistors have

been completed. The chrome silicon resistors show

predictable performance over the range of -253°C

(LH2) to +125°C and will be satisfactory for

utilization in a compensation circuit covering

this temperature range.

The PN diodes showed an unexpected, nonlinear

increase in resistivity below -196°C (LN2) •

 A

determination is being made of the impact of this

change on the output error of the sensors at

temperatures between -253°C and -196°C should this

type of diode be used in a compensation circuit.
PAGE SIX

Schottky diodes (metal-semiconductor) were also

evaluated as a possible alternative to the PN

diodes. However, these diodes also showed a

nonlinear resistivity increase at temperatures

below -196°C. Attachment E shows plots of the

characteristic curve over temperature for circuit

compensation resistors and Diodes.

B. Plans For July

The sensor compensation circuit design will be

started. Analysis of the output error caused by

the nonlinear resistivity change of standard PN

diodes will also be started, computer aided tools

will be used for this analysis.

A literature search of diode performance at

cryogenic temperatures will be completed. Pending

the results of the diode literature search,

circuit modeling, and further discussions with

NASA relative to the scope of the contract,

evaluation of other 1C circuit components to

replace the diodes may be initiated.

2.6.1.7 Error Source Anfl]ys, j,g

A. Work Performed in June:

Test samples have been tested over the pressure

range of 0 to 5000 psi and a temperature range of

-70 to 100°C. The SSME feasibility sensor chips

mounted in conventional pressure sensor packages

are performing as expected over these ranges of

temperature and pressure with respect to zero

shift, linearity, and mechanical and thermal

hysteresis. Testing has been completed over the

cryogenic temperature range (-250 to 100°C). Some

zero shifts and sensitivity shifts were observed

after low temperature (-250°C) testing. Closer

evaluation of these characteristics will be

completed during the Feasibility Transducer

Fabrication and Test Task (See Paragraph

2.6.1.10). Sensitivity is approximately 1.5x

higher than expected. Preliminary findings

suggest the additional sensitivity is due to a

thinner actual diaphragm and additional

piezoresistive contribution due to the implanted

leadouts used to access the sensing resistors.
PAGE SEVEN

B. Plans For July

Corrplete data analysis and compile the results.

This data base above will be used as a resource

during the Feasibility Transducer Fabrication and

Testing Task to analyze output errors in the

Feasibility Transducers relative to standard

packaging techniques. The data will also be used

for preliminary circuit design work (see Paragraph

2.6.3.1)

2.6.1.8 Reference Pressure Process Development Pass I

A. Work Performed in June

All the required piece parts for the process

development have been ordered. The vacuum system

is nearly complete and the machining of the

holding/heating fixture has begun. Attachment F

shows the sketch of the vacuum pumping station.

B. Plans For July

Complete the build of the vacuum pumping station

and the soldering fixture and begin the reference

pressure process development.

2.6.1.9 Reference Pressure Process Development P$?ff II

This task will not be opened until such time as the

results of "Pass I" indicate a second pass is required

to achieve the desired reference vacuum conditions.

2.6.1.10 Feasibility Transducer Fflfrcic^tion

 and Test

A. Work performed in June

Approximately 20 sets of silicon nitride

terminal boards have been polished and are being

metallized.

The low temperature and high pressure test

fixtures have been prepared for the feasibility

test sequence

B. Plans For July

Continue the assembly of the feasibility

test capsules and begin temperature/pressure

testing of the first feasibility pressure sensors.
PAGE EIGHT

2.6.2.1 Preliminary Design Review

This task is scheduled to begin later in the Program,

i.e., November 1985.

2.6.2.2 Critical Design Review

This task is scheduled to begin later in the Program,

i.e., December 1985.

The "Final Design Review" (F.D.R.) was downscoped

during a discussion with T. Marshall (MSFC Contract

Monitor). (Re: Telecon, P.J. Anderson, T. Marshall

and P. Nussbaum, 6/25/85) The conclusion of that

Telecon was that real scope of this task is better

described as "Final Design Approval" rather than

another review because NASA technical inputs will be

provided at the "Critical Design Review".

Furthermore, we agreed that this approval could be

accomplished by an advanced submittal of the design

package that is followed by a Telecon and/or a

meeting between T. Marshall, P.J. Anderson and P.

Nussbaum. This agreement allows about $17K of the

budget to be reallocated to cover the currently

planned scope of the second pass of the Hermetic

Feedthrough Development. (Re: Paragraph 2.6.1.5)

2.6.3.1 Circuit/Chip Design and Processing

A. Work performed in June.

Using the test results from the Additional

Cryogenic Data and Error Source Analysis Tasks,

work was started to set up models for the

computer modeling of the compensation circuit

design.

B. Plans for July.

Evaluation of the output error expected due to

the nonlinear resistivity change of the standard

PN diodes will be started. The evaluation of

alternative sensor compensation schemes over the

full temperature and pressure range will also be

started.
PAGE NINE.

2.6.3.2 Transducer F?frr, j^-fltion Parts and Tooling

A. Work Performed in June.

Several phone conversations were held in June

with Deutsch Electronic Components Division, G &

H Technology, and Tom Marshall (MSFC Contract

Monitor) concerning the electrical connectors

for the deliverable build.

Since the beginning of this program, we have

been advised by NASA that we should use

Rocketdyne connector RES1231-ECO5N for our

deliverable transducers and that Deutsch was the

vendor of this connector. Deutsch said that

they do make this connector and said it was

their part number 77014-10-5PN. However, their

print references Rocketdyne connector

"RES1231-A1005* (1)". Because of this

discrepancy in print numbers we have asked

Deutsch to confirm which connector they are

currently supplying to Rocketdyne. We have not

yet received a reply from Deutsch to date.

Deutsch also said that this connector could not

withstand 20,000 psi and was only good to - 65°C

and not -423°F.

All this information was sent to NASA (% Tom

Marshall) in the form of a letter. (See

Attachment G) Using this information, Tom has

gone back to his connector people and learned

that what he needs is a 10,000 psi cryogenic

connector Rocketdyne part number RES1232-C1005N

made by G & H Technology.

G & H advised us they do make this connector but

that it will take them 6 to 8 weeks to make a

cost and schedule estimate on our needs of 46

male and 8 female connectors. They did give us

a verbal engineering estimate of $400 to $500

for the male and $900 to $1000 for the female

connectors, respectively, with delivery in

approximately 30 weeks. They said that they

agreed to send us prints immediately of these

two parts. Upon receipt of these drawings, we

will send them to Tom Marshall for confirmation

that they are the ones required for our

transducer.

The impact of this situation is that we will

incurr unplanned cost and schedule variances.

Using cost estimates we previously received from

Deutsch, we have budgeted only $12.1 K for 46
PAGE TEN

male and 8 female connectors. The estimate from

G & H for the same number of connectors is

$28.3K. This represents a cost impact of

$16.2K.

These schedule impact of procuring the G & H

connector is estimated to be about 16 weeks.

At this time, the indications are that NASA

wants us to procure the G & H connector.

Honeywell recommends that the G & H connector be

procured in view of the reported moisture

problems with the Deutsch connector after

exposure to cryogenic temperatures.

B. Plans for July

o Obtain prints from both G&H and Deutsch

for male and female connectors

o Obtain cost and schedule quotes from both

G&H and Deutsch for male and female

connectors.

o Determine if we can accelerate the

delivery schedule or if we can obtain

these connectors elsewhere (Honeywell

SSAvD, etc.).

2.7 Miscellaneous

2.7.1 Vibration Requirements

Re: 1. NASA Contract No. NAS8 34769, 8/26/82

Exhibit 'A1, Section B.I

2. Honeywell's Technical Proposal, 7/12/83,

Sections 2.3 (Pages 2-5 to 2-7), 2.6.1.2 (Pages

2-15 to 2-18), 2.6.1.4 (Page 2-36 and 2-37).
PAGE ELEVEN

3. Working session at NASA/MSEC, 9/26/84

Attendees:

P.J. Anderson Honeywell Inc.

P. Golley NASA/MSPC

H. Burke NASA/MSFC

B. white NASA/MSFC

C. Kirby NASA/MSFC

4. September Monthly Report, Section 2.7.1.

5. Working Session at NASA/MSFC, 11/20/84

Attendees: P.J. Anderson, Honeywell Inc.

T. Marshall, NASA/MSFC

C. Kirby, NASA/MSPC

B. White, NASA/MSFC

During a November working session (Reference 5), Honeywell

proposed a "half-sine pulse" shock test method to satisfy

NASA's TSRS requirement as described in Reference 4. The

details of Honeywell's proposal were outlined in Attachment

'F1 of our November monthly report. T. Marshall, et al

accepted the Honeywell proposal for the shock testing and

evaluation of the Experimental Transducer.

2.7.2 Test Plans: Experimental Transducer

Re: 1. Attachment 'F', August Monthly Report

Working Session at NASA/MSFC 11/20/84

Attendees: P.J. Anderson, Honeywell, Inc.

T. Marshall, NASA/MSFC

B. White, NASA/MSFC

With the shock testing issue resolved as noted in Section

2.7.1, T. Marshall, et al accepted Honeywell's test plan as

detailed in Reference 1 except the sinusoidal vibration portions of that plan are to be replaced with the "half sinepulse" test detailed in attachment 'F1 of our November monthly

report. Honeywell's test plans have been rewritten to reflect

these agreements. See Attachment 'C1 of our January monthly

report.
PAGE TWELVE

2.7.3 Replan Effort

We have completed a replan of this program using the current

design approach to achieve the original contract scope of

work. A Cost-to-Complete proposal was completed and delivered

to NASA's Procurement Office in February 1985. (The cover

letter date was 2/7/85.)

Our Cost-to-Complete proposal was reviewed with Mr. R.J.

Richmond (Designate for Mr. S.J. Morea, Program Manager,

Advanced High Pressure Oxygen-Hydrogen Propulsion Program),

Mr. A.L. Worlund (Program Manager, Test Bed Engine Program)

and our contract monitor, Mr. T. Marshall, et al. Handouts of

our presentation were left with the NASA attendees and are

therefore not included in this report. Copies are available

upon request.

3.0 Schedule -See Attachment 'B'

This schedule reflects the results our replan effort and was included in

our Cost-to-Complete Proposal (Folder 1: Technical Proposal).

Our current status to this schedule is that we have incurred about a 4-6

week schedule slip. The primary contributors to this slip are slower than

planned progress on the Hermetic Feedthrough Task and the need to execute

a second pass to achieve the desired results with an acceptable confidence

level.

As discussed in paragraph 2.6.3.2, the pending decision to the G & H

connectors will impact the completion of the Feasibility Transducer build

by about 16 weeks.

It is not clear at this time to what extent these schedule slips can be

recovered. We however, will be exporing what can be done to minimize this

impact of these schedule slips.
RESEARCH PRESSURE INSTRUMENTATION FOR NASA SPACE SHUTTLE MAIN ENGINE

SCHEDULE

Date: 2/85

Rev: 1

Page: 1 of 2'

TASKS

2

4 Cvn Thin IfctaanMnn fK***^* **4 »»» 1 Mh fYMflt

•4 txp (*nip WNintiny i*nir*cicri*ivion |juuuj

2.6.1 Feasibility Evaluation of Transducer Concepts

2

£ 1 1 1 A*J< 1 AMAfrH D*w4ia^fr IAA 1 ICTl ) •o.t.i Leao Lentjin KCQUCI i on \ JAM j

2.6.1.2 Sea! Ring Develoownt Phase I (3300)

2

c | \ CA*I ft<MM ** « *• MtA*A II f?13nt

.o.i.j a0ai mnj ueveiopweni rnase 11 iJj«v)

2.6.1.4 Herawtlc Feed Through Developwitt Pass I (63)0)

2 C | e lfe»MAfr 4«» f— J TK^Aciflh

 K * *• DA** If 1 £9 Ifl I .0.1 .9 nenNvic reeo inrouyn ueveiopMeni rass 1 1 |Ocui )

2.6.1.6 Additional Cryo Data (6230)

2.6.1.7 Error Source Analysis (6230)

2.6.1.8 Reference Pressure Process DevelopMnt Pass 1 (6240)

2 £ \ A DA^ Ai^An^A DI*ACCH^A Df fw*A*i*j I^BM^! AA^^M^ D***< 1 1 f 4k9fift t •o . i . v ice i erence r ressure rroces* ueve • opnem rass 1 1 \ ocsu j

2.6.1.10 Feasibility Transducer Fabrication A Test (6390)

2.6.2 Deliverable Transducer Design

2.6.2.1 Preliminary Design Review (6400)

2.6.2.2 Critical Design Review (6500)

2.6.2.3 Final Design Review (6600)

1

1

4(14

4( 1U

t

"

\

-

*•

4

l

t

•

H

\

^^^

n

1

-

*

-

-

14

)

i,

ta

•

*

r-

_

Ub

1

I

RM^^

H

w

K

J1

1

f

1

1

I

•••^•H

H

r

<1

__

1

J

1

1

•1

1

«

1

iyHfe

^1

1

4t

1

New Baseline Program Schedule per 2/85 Cost-to-Complete Proposal
RESEARCH PRESSURE INSTRUMENTATION FOR NASA SPACE SHUTTLE MAIN ENGINE

SCHEDULE

Date: 2/85

Rev: 1

Page: 2 of 2

TASKS

2.6.3 Deliverable Transducer Fabrication and Test

. 2.6.3.1 Circuit/Chip Design « Processing (669) )

• 2.6.3.2 Transducer Fabrication Parts/Tooling (6700)

2.6.3.3 Transducer Calibration Development Pass I (6740, 6790)

2.6.3.4 Transducer Calibration Development Pass II (6763)

2.6.3.5 Transducer Fabrication (6780)

2.6.3.6 Transducer Calibration (6800)

2.6.3.7 Transducer Performance Testing (6850)

2.6.4 Transducer qualification Testing (6900)

2.6.5 Transducer Delivery (6960)

2.7 Reports (7000)

2.7.1 Monthly Program Reports

2.7.2 Final Report

Preliminary Design Review

Critical Design Review

Final Design Review

19H4

•»*4Q

'

1985

1Q

•

PL

2Q I 3Q

••

41 l l wn

i

•

X

i

X X

1

40

1

-

X

X

1

I

X

X

1986

10

1

1

1

y

\

A

h

1

1-

1

1

I^^MV

/

1

30

1

I

1

X

1

If

X X

4Q

X

1

1

|

1

I"

X

1

1t

^— ;

\

X

»

1

New Baseline Program Schedule per 2/85 Cost-to-Conplete Proposal
ATTACHMENT C

FINAL REPORT: EXPERIMENTAL CHIP MOUNTING

CHARACTERIZATION
HONEYWEL L Interoffice Correspondence

SSED - 85-03-2328

Date: July 12, 1985

Subject: Research of Pressure Instrumentation for NASA

Final Report - Experimental Chip Mounting Characterization

To: P. Nussbaum MN14-3B35 From: D. Wamstad/J.Shea

G.Gustafson

Organization: SSED

cc: P.Anderson MN14-4C40 HED: MN14

Library (2) MN14-4B50 MS: 3B35

Telephone: 541-2091/2413/2628

Key Words: Cryogenic Pressure Sensor

High Pressure Sensor

TE Bonding

Silicon Nitride

Metal Seal Ring

Abstract

The mechanical integrity of a silicon chip mounting concept to be

used in the fabrication of a Space Shuttle Main Engine pressure

transducer is demonstrated. The design, fabrication, and testing of

test hardware as well as the chip mounting capsule and housing is

described.

TASK

The objective of this task was to experimentally determine the

mechanical integrity of a pressure sensor chip mounting concept to

be used in the fabrication of a Space Shuttle Main Engine pressure

transducer.

The objective of this task was accomplished. The mechanical

integrity of the pressure sensor mounting concept for the SSME

application selected in Task 2.1 was demonstrated. Mechanical

models were built and tested and successfully passed the SSME

requirements for hermeticity, temperature, pressure and vibration.

Finite element stress modeling of the v-ring seal on sensor chip

performance showed that the stresses are cause for concern.

Consequently, close attention will be paid to the experiment planned

for the upcoming feasibility sensor build under which capsules will

be moved between housings and the impact on the null reading will be

observed. The results of this V-ring stress modeling subtask are

attached as an addendum to this report.
TASK DESCRIPTION; The following sub-tasks supporting the overall task

objective

were completed:

o 2.3.1 - Define Experimental Processing and Evaluation Testing

o 2.3.2 - Design Experimental Hardware

o 2.3.3 - Design and Build Test Hardware

o 2.3.4 - Develop Assembly Processes

o 2.3.5 - Prepare Mechanical Silicon Test Chips

o 2.3.6 - Build Experimental Hardware

o 2.3.7 - Assemble Experimental Hardware

o 2.3.8 - Low Temperature Shock Testing

o 2.3.9 - Room Temperature Pressure and Vibration Testing

2.3.1 SOB-TASK SUMMARY - Define Experimental Processing and, Evaluation Testing

The pressure transducer silicon chip mount design is extremly important.

Sensor performance, in terms of accuracy, repeatability and stability , is

dependent on its interface with the transducer package and pressure media. To

determine the pressure capability and the extent that sensor performance is

dependent on this interface, two experimental concepts were built, tested and

evaluated. The experimental processing and evauation testing were of the two

concepts instrumental in the concept selection for Task 2.1. These were

Concept 1, "Steel Tube Direct Chip Mount (Low Expansion Nickel Iron)" and

Concept 5, "Silicon to Silicon Nitride Matched Compression Seals" and are shown

in Figures 1, 2, 3 and 4.
FIGURE 1

CONCEPT 1: STEEL TUBE DIRECT CHIP MOUNT

(LOW EXPANSION NICKEL IRON)

1. SILICON SENSOR CHIP MITH BONDING AREA * TALI ZED (HETALIZATIONSPUTTERED TITANIUM-PLATINUH-GOLD OR OTHER HETALIZATION)

2. HIGH STRENGTH SOLDER PREFORM (GOLD-TIN. GOLD-GERMAN It* OR OTHER HIGH

STRENGTH MATERIAL)

3. LOW EXPANSION NICKEL IRON-ALLOY 36 OR SIMILAR MATERIAL (HETALIZATIONSPUTTERED TITANIUM-PLATINUM-GOLD OR OTHER NETALIZATION)
FIGURE 2

CONCEPT 1: SSME PRESSURE SENSOR PACKAGE - STEEL

TUBE DIRECT CHIP MOUNT (LOW EXPANSION

NICKEL IRON)

1, STEEL TUBE DIRECT CHIP MOUNT (LOW EXPANSION NICKEL IRON)

2, HEADER - CERAMIC TO PROVIDE ELECTRICAL LEADOUTS AND BONDING AREA FOR

COVER GLASS AND STAINLESS STEEL BASE,

3, COVER - GLASS-TO ALLOW LASER TRIMMING OF THE SILICON SENSOR CHIP

' COMPENSATING NETWORK AND PROVIDE A HERMETIC SEAL BETWEEN THE COVER

GLASS AND CERAMIC,

4, STAINLESS STEEL LOAD BEARING PLATE

5, STEEL SEAL TO PROVIDE SILICON DIE PRESSURE RUPTURE PROTECTION

6, STAINLESS STEEL BASE

7, STAINLESS STEEL COVER
CONCEPT 5: SILICON TO SILICON NITRIDE HATCHED

COMPRESSION SEALS

FIGURE 3

1. SILICON SENSOR CHIP WITH BONDING AREA ON CIRCUIT SIDE.

2. SILICON NITRIDE MATERIAL TO PROVIDE HERMETICALLY SEALED ELECTRICAL

CONDUCTOR PADS FROM SILICON SENSOR CHIP TO LEAD WIRES.

3. SILICON NITRIDE MATERIAL TO PROVIDE HERMETICALLY SEALED ELECTRICAL

CONDUCTOR PADS WITH ELECTRICAL ISOLATION AREAS.

1. SOLDER BOND TO PROVIDE HFRMFTIC SEAL BETWEEN THE TWO (2) SILICON

NITRIDE PARTS.

5. COVLR -GLASS--TOALLOW LASER TRIMfllNG OF THE SILICON SENSOR CHIP

COMPENSATING NETWORK AND PROVIDE A HERMETIC SEAL BETWEEN THE COVER

GLASS AND SILICON NITRIDE.
FIGURE 4

CONCEPT 5: SSME PRESSURE SENSOR PACKAGE - SILICON-TO-SILICON

NITRIDE MATCHED COMPRESSION SEALS

SILItON-TO-SILICON NITRIDE MATCHED COMPRESSION SEALS - CONCEPT

ALUMINUM WIRE COMPRESSION HERMETIC SEAL

ALUMINUM WIRE COMPRESSION HERMETIC SEAL

STAINLESS STEEL BASE

STAINLESS STEEL HOUSING
1. Concept 1 Evaluation, "Steel Tube Direct Chip Mount (Low Expansion Nickel

Iron)"

- Evaluation Test Sample: The chip tube mount configuration is

shown in Figure 1 and consisted of the following:

o Silicon Sensor Chip

- Backside (Cavity side) metallized with sputtered Ti/Pt/Au

o Solder Preform

- Au/Ge

- Preform: ANNULUS .050 ID

.100 O.D.

.001" Thick

o Low Expansion Nickel/Iron Tube

- Alloy 36 (36% Ni - Fe Alloy)

- Tube ends metallized with sputtered Ti/Pt/Au

- Bond Area: ANNULUS .045: ID

.125" O.D.

- Evaluation Testing Results: Limited overpressure of the chip

mounting Concept 1 was completed. The testing consisted of

overpressuring the assembly, with the pressure applied to the

backside of the die through the Invar tube pressure port.

Pressure was applied up to 10,000 psi in increments of 1000 psi

for 10 minutes at each pressure. The device failed at 10000 psi

after the pressure was applied for approximately 5 minutes.

Further development of the bond between silicon die and the low

expansion Nickel/Iron tube would be required to insure concept

feasibility.

Failure Analysis results based on the small area bonded, support

the conclusion that a 20,000 psi burst pressure can be obtained.

Despite this performance, there is a concern relative to this

concept, namely, the silicon-steel joint is under tension rather

than compression. Clearly, this situation would require an

extremely strong joint in order to meet the high pressure/low

temperature requirements for this application.

2. Concept 5 evaluation, "Silicon to Silicon Nitride Matched Compression

Seals" - The iirpact of compressive loading on the sensor null (offset) for

a structure similar to Concept 5 was experimentally evaluated. This

testing simulated the application of a compressive load applied to the

outer edge of the silicon nitride terminal boards, and demonstrated its

effect on sensor performance for pressure loading up to 20,000 psi. Based

on the results of this testing, along with a two-dimensional finite element

stress analysis, instrumental in redesign of the original Conept 5 to

minimize mounting stress transmission was preformed. This design change

involved adding an Invar interface, with controlled surface flatness,

between the silicon nitride and stainless steel, adding a surface flatness
requirement to the silicon nitride parts and adding a metal compressive C-Ring

between the silicon nitride and stainless steel (see Figure 5). This change

will uniformly distribute the structural compressive load over the required

transducer pressure and temperature range.

The pressure transducer silicon chip mount design utilizes materials with

closely matched coefficients of expansion; silicon, silicon nitride, pyrex and

Invar. This match will minimize the thermal stresses over the large

temperature differential of 682 degrees F required for the SSME application.

To insure package survivability at high pressure and cryogenic temperatures the

design maintains the transducer seals in compression.

- Evaluation Test Sample: The impact of compressive loading on the sensor

null was experimentally evaluated using an in-house developed sensor

device. This sensor chip was mounted to a thin glass washer which is in

turn mounted to a ceramic "chip carrier" type package. The effect of

compressive loads up to 20,000 psi and over temperature were measured.

Force was applied to the sensor by a piston and weight arrangement. The

force was converted to correspond to a pressure reading through a

fulcrum. Weights from the dead weight tester were utilized.

- Evaluation Testing Results: Testing was completed to simulate the

compressive pressure loading impact on transducer performance. The

purpose of this testing was to determine the strain transmitted to the

silicon chip by the impact of compressive loads applied to the outer

edge of the silicon nitride. The key findings of this testing are:

- Compressive loading can result in substantial stress transmission to

the sensor chip

- The stresses transmitted to the sensor are strongly dependent on the

method of clamping in the test fixture.

- The stress transmitted to the sensor is strongly dependent upon the

condition (flatness) of the mating surfaces between the test samples

and the test fixture.

- Changes in the piezoresistors ranged between 0-2% when close

attention was paid to the aforementioned conditions.

Based on the results of this experimental testing, the original

transducer package design concept was changed to minimize stress

transmission to the sensor chip by either pressure or temperature. This

design change will uniformly distribute the structural compressive load

over the required transducer pressure and temperature range, (see

Figure 5)
Od

^

CJ3

0)

(0
Two dimensional, finite element stress analysis was completed for the

test sensor used for compressive loading experiments and for Concept 5.

The key findings were:

- Both the test sensor and Concept 5 respond similarly under

conpressive loading. The stress level differences agreed within a

range of 1.0 - 1.6.

- The agreement between the experimental and predicted, 2-D,

behavior of the test sample are quite different. A 3-D stress

model is required to account for the mounting effects noted

earlier. It is not planned to do a 3-D analysis of the IPT test

sample because of the cost involved. However, a 3-D analysis of

the final configuration of Concept 5 will be made.

2.3.2 SDB—TASK SUMMARY — Design Experimental Hflr^^rS

o Experimental Transducer Package Design - The SSME Transducer Package Design

is documented in Figure 3 and Figure 4. This encompasses an absolute

silicon pressure sensor chip with laser trimmable circuit electronics

mounted to a silicon nitride backplate and terminal board. The chip mount

vacuum reference of the absolute transducer is established through the

hermetic seals of the silicon, silicon nitride and the pyrex cover glass.

The sensor chip mount is housed is a cannon package with electrical

interface and pressure port provision.

o Experimental Transducer Silicon Chip Mount Design - The pressure transducer

silicon chip mount design is extremely important. Sensor performance, in

terms of accuracy, repeatability and stability, is dependent on its

interface with the transducer package and pressure media. There are four

basic SSME requirements which dictate the pressure sensor chip mount

design. These are:

1. Pressure Media Interface - The high pressure (9.5K psi), cryogenic

temperature (-320 degrees F) and pressure media (LCK, LH2, gaseous

helium, nitrogen, oxygen, hydrogen, air and water vapor) require the

active circuit side of the pressure sensor chip be separated from the

pressure media. This is accomplished by applying the pressure to the

backside of the pressure sensor chip.

2. High Pressure/Low Temperature - The combined high pressure and low

cryogenic temperature requirements dictate that the pressure media be

applied directly to the chip.

3. Active Laser Trimming - Active laser trimming of on-chip thin film

resistor networks to calibrate sensor performance is normally completed

after sensor packaging. This is done to eliminate the packaging and

assembly process effects on transducer calibration. This dictates that

the trimmable network be visible after packaging and further impacts the

pressure sensor chip mounting.

10
4. Absolute Sensor - The absolute sensor requirement provides an additional

challenge. The materials and processes utilized in the construction of

the pressure transducer influence the sensor vacuum integrity.

Materials were selected based on their diffusion and outgasing

characteristics, high herroeticity capability and temperature pressure

compatibility.

o Transducer Hardware Design - The design was completed for the following

transducer piece parts:

- Stainless Steel Housing

- Stainless Steel Base

- Silicon Nitride Terminal Boards 1 and 2

- Pyrex Cover Glass for laser trimming

- Invar Mounting Plate

- "V" - Ring Seal

- Pyrex Washer for bond between silicon and silicon nitride

2.3.3 SGB-/EASK SUMMARY - Design and Build Ttest Hardware

The design and build of test hardware was completed for the following:

o Compressive Load Testing - Test fixturing was designed and fabricated to

test the impact of compressive loading on the sensor null when force was

applied through a special package to the sensor chip.

o Vibration Testing - This fixture was completed and provided for transient

shock testing.

o High Pressure Testing and Leak Testing - The design and build of this

fixture provided both functions of high pressure testing and hermetic leak

testing in a single fixture. This fixture utilized a metal V-Ring to

provide the high pressure and hermetic interface between the sensor housing

and the fixture.

2.3.4 SDB-TASK SUMMARY - Develop Assembly Processes

The SSME Pressure Transducer Design goals, due to the combined effects of

cryogenic temperature, high pressure, vibration and absolute pressure sensing

are extremely challenging, This impacts the design, materials section and

assembly processing. The basic SSME design goals are summarized in Table 1.

11
Table 1 Summary of SSME Pressure Transducer Design Goals

CONDITION

Transducer

Configuration

Pressure Changes

Pressure Rating

Pressure Media

Temperature Range

Vibration

Acoustic Frequency

Response

Full Scale Output

Thermal Zero Shift

Electrical - To -

Pressure Calibration

- Same external configuration as RC7001

- 0 to 600 psia

- 0 to 3500 psia

- 0 to 9500 psia

- 1.5 x F.S. (No permanent null or

calibration change)

- 2.5 x F.S. or 20K psi Maximum

(No permanent damage)

- Liquid/Gaseous Hydrogen

- Liquid/Gaseous Oxygen

- Helium

- Nitrogen

- -200°C to + 120°C (Goal of - 253°C)

- 0 to 2000 Hz; 400 g's (With superimposed

random and steady-state vibration

- Dynamic Design Goal of 300 Hz Minimum

30 ± 0.3mV at 10 VDC Excitation

± 0.005% F.S./Degree

±0.1% F.S. at 80% F.S. Correlation

points at Ambient Temperature

12
The transducer design approach implements the NASA requirement for direct

mounting of the pressure transducer to the SSME. This requires the pressure

sensing element to be in direct contact with the high pressure cryogenic

pressure media. It also requires, based on the state of the

hydrogen/oxygen/nitrogen pressure media, that the silicon integrated circuits

not be in direct contact with the pressure media. The assembly process

development is summarized as follows:

- Process Development for Joining the Silicon Die to the Silicon Nitride

Terminal Board: Three approaches were tried.

1. TE bond of the silicon chip directly to the silicon nitride

terminal board - Tried but not successful (see below).

2. TE Bond of the silicon chip to a glass layer deposited on the

silicon nitride - Approximately 4000A of glass was sputtered on to

the silicon nitride. Tried but not successful (see below).

3. TE Bond to Join the Sensor Chip to a Pyrex Washer - Of the three,

only this one has a reasonable probability of being successful.

This approach uses TE bonding to join the sensor chip to a pyrex

washer and a solder bond to join the sensor/pyrex assembly to the

silicon nitride. The solder bond is at the pyrex-silicon nitride

interface. Some of the key features of these joints are as

follows: (see figure 6)

o TE bond (silicon to pyrex): Requires optically flat

surfaces

o Interface metallization (pyrex-silicon nitride: Ti/Pt/Au or

Ti-W/Ni/Au both surfaces

o Solder: Au/Ge or Lead/Tin/Silver

The integrity of these joints was evaluated using the following

temperature shock testing profile:

o Liquid Nitrogen - (-200°C) to 100°C: Five times

o Liquid Helium - (-255°C) to 25°C: Three times

The test evaluations showed no damage to the joints and after

temperature shock the joints were hermetic.

The silicon/pyrex washer/silicon nitride structure was modeled

using finite element methods to determine the impact of solder

creep on sensor performance. This analysis shows that changes in

stress due to solder creep can be transmitted to the sensor chip.

However, this effect can be minimized by using a solder that has a

high resistance to creep. Because of the high strength properties

of the Au/Ge solder, it is expected it will have a high resistance

to creep. This may , however, require some critical experiments

to verify the magnitude of this effect.

13
o

LU

cs:

O

0.

o

(A

•o

CO

0)

"S

§

eo c

O £ <8 00 CD [I

§ 1 1

ill

£ £ £

i I i

^ CM eo

0

<5

| «

?S — O E

i_ 3

S

I

 ^ 1

I I

in <o

i

us

I

(A

.t!

3

2

O

o

'C

m

I

eo

14
The difficulty with the other two approaches for joining silicon

to silicon nitride was that with or without a sputter-deposited

pyrex film on the silicon nitride, the required optical flatness

could not be achieved. The next result was that TE bond could not

be made.

- Process Development for Joining the Silicon Nitride Terminal Boards

Together - Considerable difficulty was encountered in developing the

hermetic seals between the two silicon nitride terminal boards and the

pyrex washer. New process development was required for the following:

o Silicon nitride metalization

o Delineation of the metal pattern

o Defining and obtaining the required silicon nitride surface finish

o Development fixtures for soldering and leak checking

o Process variable determination (fluxless hermetic joint)

o Failure analysis techniques

In successfully achieving the high degree of hermeticity required for an

absolute sensor numerous process and material factors were isolated

which effect hermiticity of the silicon nitride joint. The leak rate

requirement of 1 x 10-1^cc per second helium equivalent maximum is

extremely stringent. The following is a summary of the process

development.

o Silicon nitride metalization - One of the key factors required to

achieve the hermetic seals between the silicon nitride terminal

boards and the pyrex washer was to change the metalization from

Ti-Pt-Au to Ti/W-Ni-Au. This change also permits the metalization

pattern required for the hermetic seal area and electrical

feed-throughs to be delineated by standard photoresist methods and

etching.

o Delineation of the metal pattern - Two basic processes and the

required tooling were developed for delineating the metal pattern;

abrasive blast and shadow-masking during metalization sputtering.

Delineating the pattern by standard photoresist methods and

etching will be utilized in the follow-on tasks.

o Silicon nitride surface finish - an essential key factor in

achieving the silicon nitride hermetic seals was the determination

that leaks in the seal area were caused by minute scratches and

machining marks. A lapping process was developed to remove the

scratches.

2.3.5 SDB TASK SCTMARY - Prepare Mechanical Silicon Test Chips

The fabrication of nonfunctional "sensor" chips (Silicon chips without

piezoresistor circuits) was completed in support of the assembly process

development activity. The chips were made from three 3.0 inch diameter by

0.100 inch thick wafers. These were lapped to 0.035 inch thick and then cut

into 0.225 inch square silicon chips.

15
2.3.6 SOBTASK — Design and Build Test

•The fabrication of the transducer piece part hardware was completed and

itemized as follows:

- Stainless Steel Housing and Base: Parts were machined from 304L

stainless steel

- Silicon Nitride Terminal Boards:

o Parts were fabricated by Ceradyne Santa Ana, Califiornia

o Parts were metalized by sputtering with two different

metalization systems; Titaniun/Platinum/Gold and

TitaniunHTungsten/Nickel/Gold

- Invar Mounting Plate: Parts were machined from Invar (Alloy 36)

- Pyrex Cover Glass and Pyrex Washer: Parts were fabricated by Rogers

Custom Optics, Minneapolis, Minnesota

- Metal "V and C" Rings": Parts were purchased from Advancced

Products, North Haven, Connecticut

2.3.7 SUB TASK SGMMARY - Assemble Experimental

The procedure used in the assembly of the experimental hardware was as follows:

A. Capsule Assemble

1. The pyrex washer was TE bonded to the top side of the sensor chip.

2. The chip/washer subassembly was sputter metallized on the pyrex

side with Ti/tt-Ni-Au.

3. The silicon nitride terminal boards were sputter metallized with

Ti/W-Ni-Au.

4. The terminal boards and the chip/washer subassembly were soldered

together using Au-Ge solder.

5. This capsule assembly was He leak checked and determined to be

hermetic.

6. Both one and two mil diameter gold wires were ball-bonded between

the sensor chip pads and the metallized pads on the terminal

board.

B. Wiring and Potting of Housing

1. Thirty gauge Teflon insulated copper wire was used to make

electrical connection between the eight connector pins and the

housing.

2. These wires were soldered to the connector pins and silver epoxy

bonded to the housing.

3. Four of the eight wires were coated at each end with Dow Corning

RTV prior to potting.

4. The housings were potted with Emerson & Cuming epoxy.

C. Housing Assembly

1. The Invar back-nip plate was placed into the housing sensor cavity.

2. The sensor capsule was placed on top of the back-up plate.

3. A metal V-ring seal was placed on top of the sensor capsule.

4. The stainless steel base was then screwed into the housing.

16
2.3.8 LOW TEMPERATORE SBQCK

One of the methods used to determine the mechanical strength of the chip

mounting concept was a thermal shock test. This test was performed on both the

capsule subassembly immediately after solder sealing and on completed

mechanical transducer models. The procedure for testing the capsule

subassembly was as follows:

1. Helium Leak Check

2. Immerse in Liquid Nitrogen (60 sec.)

3. Place in 110°C oven (5 min.)

4. Helium Leak Check

All capsules that were hermetic after solder sealing remained hermetic after

this single shock test.

The completed transducers were also thermal shock tested. This test was

performed on the device following high pressure and mechanical shock testing.

(The complete test plan for the pressure, mechanical shock and thermal shock

testing is described in Appendix I.) The temperature shock testing was

performed as follows:

I. Test

A. Immerse complete transducer in liquid nitrogen (10 minutes)

B. Iirmediately place in an oven at 110°C (20 minutes)

C. Repeat steps A and B two more times

II. Evaluation

A. Helium leak check

B. Disassemble

C. Helium leak check capsule subassembly

E. Electrical continually check

Three capsules that passed the high pressure and mechanical shock testing were

thermal shock tested according to this plan. The first unit remained hermetic

after thermal shock. The capsule in this device was made with Au-Ge solder and

had a small crack in the pyrex washer after mechanical shock testing. This

crack did not get any worse during thermal shock and the capsule remained

hermetic. This device had no wire bonds. One of the potted wires in the upper

portion of the housing had a large increase in resistance after thermal

shocking. This was one of the wires that was coated with RTV prior to

potting. The exact cause of this resistance increase should become apparent

when the potting is removed from the housing during Feasibility Fabrication and

Test portion of this program.

The next unit to be tested was made with Pb-Ag-Sn solder and it remained

hermetic after thermal shocking. This unit had four wire bonds and none were

affected by the shock testing. The seven good potted wires all passed the

continuity test. (One potted wire failed the continuity test before

temperature shock.)

17
The final unit to be tested was made with Au-Ge solder, had eleven wire bonds,

and had a cracked pyrex washer that had to be sealed with epoxy to make it

hermetic prior to pressure and mechanical shock testing. This device was

hermetic prior to thermal shock testing but leaked following the test. When

visually examined, several small cracks could be seen in the epoxy. There were

no wire bond failures and again there was no change in resistivity of the

potted wires.

2.3.9 ROOM TEMPERATURE PREfiSDRE AND VIBRATION TESTING

As the design concept evolved, there was considerable concern that the long

lead lengths of the wire connections from the chip to the terminal board would

be a cause of failure when the transducers were vibrated. To determine if this

was a problem, two sensor capsules were assembled using both one and two mil

diameter gold wire and were vibration tested on our VTS 100-C vibration table.

Both devices were tested in two axes (parallel and perpendicular to the plane

of the die). The vibration conditions were:

o 40g's: 1000Hz to 2500Hz: 1 octave/min.: 30 rain, total

o 40g's: 2500Hz to 3500Hz: 1 octave/min.: 30 min. total

o 40g's: 3500Hz to 4800Hz: 1 octave/min.: 30 min. total

No wires failed but the wires were too small to see if there was any resonant

frequency. This test indicates that there should be no problems with these

wires passing the NASA SSME vibration requirements since 4800 Hz is

significantly above the spec maximum of 2000 Hz.

The original plan was to do some limited vibration testing on fully assembled

transducers to determine mechanical integrity. The amplitudes of the

sinusoidal sweeps were to be as follows:

Frequency Amplitude

150 to 200 Hz 130g peak

200 to 3000 Hz 150g peak

170 Hz 120g peak

2000 Hz 400g peak

However, before the testing began, it was determined that this testing was more

severe than required and that a Transient Shock Response Spectrum (TSBS) test

was a more appropriate test procedure. It was then determined that Honeywell

had only a limited capability to perform the required testing and analysis to

assess the performance of our pressure transducer to the TSRS requirement. It

was concluded that we could use a "Half-Sine Pulse" shock test to match very

closely with the TSRS requirement. Our experience from previous TSRS work has

shown that the actual TSRS results obtained with the half-sine pulse test match

the predicted response to within about +3 db to +6 db.

18
The half-sine pulse test method used to evaluate the pressure transducer was as

follows:

o One axis; two directions where the axis is that which is orthogonal to

the surface (i.e., diaphragm) of the sensor chips

o One axis; one direction where this axis is orthogonal to the one

described above

o One axis; one direction where this axis is othogonal to both described

above

o Parameters of the Half-Sine Pulse

- 250 g's

- 1.0 millisecond

o Output data: Oscilloscope photograph of acceleration vs. time

This test was performed on the device following high pressure testing. (The

complete test plan for the pressure, mechanical shock and thermal shock testing

is described in Appendix I.)

Three transducer assemblies were mechanically shock tested (three capsules in

two different housings). All three devices passed the test. They were

hermetic before and after testing and the wire bonds and potted wires did not

fail. One of the capsules had a small crack in the pyrex washer along one edge

of the chip, extending to the outside diameter of the washer. Despite this

crack the capsule remained hermetic.

Prior to the mechanical shock testing all three assemblies were high pressure

tested using the following procedure:

I. Helium Leak Check

A. At atmospheric pressure

B. At 1500 psi pressure

II. Pressure Test (Helium Gas)

A. Apply 3500 pel

B. Helium leak check at atmospheric pressure

C. Apply 6000 psi

D. Helium leak check at atmospheric pressure

E. Apply 10,000 psi

F. Helium leak check at atmospheric pressure

III. Evaluation

A. Continuity test

B. Dissassemble

C. Visual inspection

D. Helium leak check capsule

All three devices passed this high pressure test without any failures.
ATTACHMENT I.

EXPERIMENTAL PRESSURE TRANSDUCER TEST PLAN

I. Objective! To determine the mechanical integrity of the sensor

mounting assembled within the transducer package over

temperature, pressure and mechanical shock.

H. Test Device; An electrically non-functional version of Honeywell's

current design approach

III.

IV.

A. Physical Condition — Visual

B. Hermeticity of Joints and Seals — Helium Leak Check

C. Continuity of "Dummy" Electrical Leads — Visual and Continuity Check

A. Sample Sized = 2 Units (Three capsules in two housings were tested)

B. Baseline Continuity Check

C. Baseline Leak Check

1. At Atmospheric Pressure

2. At 1500 psi of Helium Pressure

D. Baseline Pressure Test

1. Test Gas: Helium

2. Apply 3500 psi

3. Leak Check At Atmospheric Pressure

4. Apply 6000 psi

5. Leak Check At Atmospheric Pressure

6. Apply 10,000 psi

7. Leak Check At Atmospheric Pressure

E. Evaluation

1. Disassemble First Unit

2. Continuity Check

3. Visually Inspect And Note Results

4. Leak Check Atmospheric Pressure

F. Decision

1. Pending Results From E. Above, Repeat Steps B-E

.2JL
ATTACHMENT I (CONTINUED)

G. Sample Preparation For Next Test

1. Reassemble Test Device(s)

2. Leak Check At 1500 psi Of Helium

H. Mechanical Shock Testing — Part I

1. Sample Size: 2 Units

2. Transient Shock Spectrum

a. One Axis; two directions where the axis is that which is

orthogonal to the surface (i.e., diaphragm) of the sensor chips

b. One axis; one direction where this axis is orthogonal to the

one described above

c. One axis; one direction where this axis is orthogonal to the

two described above

d. Parameters of the Half-Sine Pulse

- 250 g's

- 1.0 millisecond

e. Output data: Oscilloscope photograph of acceleration vs. time

I. Evaluation

1. Leak Check At 1500 psi Helium

2. Disassemble

3. Continuity Check

4. Visual Inspection And Note Results

J. Sample Preparation For Next Test

1. Reassemble

2. Leak Check (Hermeticity Not Required, Just Note Leak Rate)

K. Mechanical Shock — Part II

1. Sample Size - 2 Units

2. Transient Shock Spectrum

a. One axis; two directions where the axis is that which is

orthogonal to the surface (i.e., diaphragm) of the sensor chips

b. One axis; one direction where this axis is orthogonal to the

one described above

c. One axis; one direction where this axis is orthogonal to the

two described above

d. Parameters of the Half-Sine Pulse

- 250 g's

- 1.0 millisecond

e. Output data; oscilloscope photograph of acceleration vs. time

21
ATTACHMENT I (CONCLUDED)

L. Evaluation

1. Leak Check At Atmospheric Pressure

2. Disassemble

3. Continuity Check

4. Visual Inspection And Note Results

M. Sample Preparation For Next Test

1. Leak Check Sensor Mount Subasseirbly

2. Reassemble

3. Continuity Check

N. Temperature Shock Testing

1. Immerse In LN2 For 10 Minutes

2. Immediately Place In An Oven At 110°C For 20 Minutes

3. Repeat A and B Sequence Two More Times In Succession

0. Evaluation

1. Leak Check At Atmospheric Pressure

2. Disassemble

3. Visual Inspection And Note Results

4. Leak Check Sensor Mount Subassembly

5. Continuity Check

P. End Of Testing/Evaluation Of Experimental Transducer Model

\

22
ADDENDUM

V-RING STRESS MODELING

G.E.G

6/17/85

Introduction

This report documents the results of "V-rlng Stress Modeling" a suDtask of

the Research of Pressure Instrumentation Program Task 3000 "Experimental

Chip Mounting Characterization". The objective of this task was to evaluate

the effect of the v-ring compression seal on the sensor chip performance

using a computer (finite element) modeling software called ANSYS. The

v-ring causes stress to the sensor chip when compressed between the silicon

nitride sensor capsule and the stainless steel plug (see Figure 1). The force

applied to the sensor capsule by the v-ring is *250 Ib/in. This force is

required in order to obtain the hermetic pressure seal.

The stresses in the sensor capsule created by the v-ring compression seal

must be nearly symmetric so that the offset or null value is not shifted over

a range that would be very difficult to trim out during calibration.

One example of an asymmetric loading of the v-ring would be if the silicon

nitride capsule and the stainless steel plug are not co-coplanar; the force

due to the v-ring compression seal would be greater on one side than the

other. Analysis of this condition will help to determine the calibration

procedure and packaging configuration required to successfully complete the

laser trim calibration. Capsule orientation may significantly affect the

sensor null (or offset) voltage. If so, the concept of calibrating the capsule in

one housing, then removing It and completing the packaging in a different

final housing may not be feasible.

Summary

Stresses at the high end of the ranges measured are cause for concern with

respect to the capability to calibrate and the effect of moving the capsule

from a calibration housing to a final housing. Nullshifts ranging from 0.2 to

2.9 milivolts and 0.04 to 0.5 mllivolts are expected for the 600 and 3500 psi

ranges respectively. Consequently, close attention will be paid to an

experiment planned for the upcoming feasibility sensor build under which

capsules will be moved between housings and the impact on the null reading

observed. If this experiment indicates that large, nonrepeatable stresses

A-l
will cause major null shifts when the capsules are moved, then the

alternative approach of calibrating in a subassembly of the deliverable

housing will be seriously persued. Calibrating a null shift range of * 0.5 mV is

feasible but calibrating a range as high as ± 2.9 mV may be difficult. Further

analysis of this issue will continue in the deliverable circuit design.

Nullshift values will also be measured during the feasibility sensor build. If

sufficient asymmetric loading exists in the feasibility units then calibration

in a subassembly of the final package will probably be the best approach.

Data Summary

Stresses in the silicon sensor due to the v-ring compression seal are

expected to cause a nullshift in the range of 0.13 to 0.3 mV. An extreme

maximum nullshift may be as high as 1.65mV. These results are based on a 12

mil thick diaphragm. The pressure ranges for the deliverable transducers are

600 and 3500 psi and the current design requires 9 mil and 22 mil diaphragm

thicknesses respectively. Stresses in the silicon sensor due to the v-ring

compression seal are expected to cause a nullshift of 0.2 to 0.5 milivolts

with an extreme maximum of 2.9 milivolts and 0.04 to 0.1 milivolts with an

extreme maximum of 0.5 milivolts for the 600 and 3500 psi ranges

respectively. Computer-simulation calculations were completed with the

following assumptions.

Model Assumptions : • 12 mil thick diaphragm with 65 mil radius

• Sensitivity Factor n^ is 4794 E-6 ir^/lb

• V-ring load of 2501bs/in with a superposition

asymmetric load of up to [125*Cos(e)l

• Bridge supply voltage 2.5 Volts.

• Extreme maximum nullshift is due to the difference

between radial and tangential stress components

equal to half their individual value (275 Ibs/in).

• Evaluate other diaphragm thicknesses with the

following formula: (t/r)2 * V^-^, = Constant

Diaphragm thickness t

Diaphragm radius r

Sensor nullshift mV
ANSYS Finite Flement Computer Modeling

Two modeling runs were completed evaluating a 12 mil thick diaphragm. The

first simulated a symmetric load and the second an asymmetric load caused

by the V-Ring compression seal. The layout of the packaging model is shown

in Figure 2 . One half of a cross section of the package is drawn and an

axisymmetric rotation is assumed by the model. Each of the various

materials in the package are identified and the material properties are input

to the model. The force applied by the v-ring is specified and an exaggerated

view of the deformation caused is shown in Figure 3 . The stress values

calculated for the circuit side of the sensor chip are analyzed and plotted as a

function of diaphragm radius (see Plots 1-5). The stress is computed in psi

relative to tangential and radial components of the stress field on the

diaphragm. These values of stress are used to calculate the signal output as a

function of device sensitivity, supply voltage, and radial and tangential

stress values.

signal ~

 n44/2 ^r ~ ^t' supplg

n^ Sensitivity factor for the Feasibility Sensor Chip.

~4.794E-6in2/lb

ar Radial stress component at sensing resistors.

at Tangential stress component at sensing resistors.

v

 ply Supply voltage to sensing bridge. (2.5 Volts is assumed)

Symmetric Load Case

Evaluating the 12 mil thick diaphragm model, the stress values for the

symmetric load case of 250 Ib/in yields about 550 psi stress for both radial

and tangential components at a 50 mil radius of the sensor diaphragm, the

radius at which the sensing resistors are located (see Plots 1 & 2). The

difference (ar - at) is about -22 psi. This small difference is due to the

symmetric nature of the model. The null shift expected is about:

v

«lgnal

 = <4

-

7

94 E-6 in2/lb) / 2 * (-221b/ in2 ) * 2.5 Volts

• -0.13mV

A-3
The stress levels of the radial and tangential components are much higher

than their difference. Higher actual deltas are to be expected since the

stresses are evaluated from a symmetric mathematical model. In reality the

packaging induced stresses will not be as symmetric. An extreme worst case

would be to assume the difference in ar - at to be 275 psi (50% of the

individual stress). In this case the null shift may be as high as 1.65mV.

Asymmetric Load Case

Using a 12 mil thick diaphragm model, the stress values for the asymmetric

load case have been evaluated as a superposition force function on the

symmetric case of 250 Ib/in. The model allows the force to be applied as an

F*Cos(9) function; where the force on the sensor capsule is a maximum (F) at

0* and a minimum (-F) at 180*. The values of F evaluated are 250, 125, and

50 Ib. The stress values are calculated by the model at 0', 45*, 90*, 135*,

180', 225*, 270", 315*, and 360*. Stress values at each angle and force F are

plotted as a function of sensor chip radius (see Plots 3, 4, & 5). The worst

case ar - at values found at 0* were used to evaluate nullshif t. Depending on

resistor orientation, nullshif t may be less. The resulting null shift expected

due to each force F*Cos(6) superimposed on the symmetric load case Is

tabulated below.

Worst case of

<or-ot>*

Model values

V **

s1«nel

12 mil thick

600 psi Units

V **

s1gna1

9 mil thick

3500 psi Units

VV **

s1gnal

22 mil thick

F*Cos(8)

50 Ibs 34 Ib/ in2- 0.2 mV 0.36 mV 0.06 mV

1251bs 521b/ln2 0.3 mV 0.53 mV 0.09 mV

250 Ibs 83 Ib/ in2 0.5nW 0.9 mV O.lSmV

**

* Sensing resistors are located at a 50 mil radius on the diaphragm.

Supply voltage across the bridge is assumed to be 2.5 Volts.

Underlined values are calculated based on the 12mil thick diaphragm 65mil

radius model :

(t/r)2 * M^qm} = Constant

Diaphragm thickness t

Diaphragm radius r

Sensor nullshif t mV V^ }

A-4
SSME Pressure Transducer

Package Concept

2 Mrtaiy.fUng

1 SMeonCNpMount

Figure 1

GEG

A-5
Drawing of AN5YS Model

SEf1

«.C3

1

EHJJXTf

I

U

1

1

X

4 A

14-3

A

eze

1

i

*

1

1

_, 1

A£AAAAAA£ > H A A A

V-RIH6 STRESS HOPELlEL 25) RUN TWO G.tUcIRr

3-' 7 ?•£•

PREP? LLEFEHT:-

SCftLINC-.

2V=1

BIST =.266

OH

Figure 2

GEG

A-6
Exaggerated View of the

Deformation Caused by the

V-Ring Seal

=•0

i

J

jj

S.C

ill -

n-r-r'

--I

-lNf- =

J

X

9H-

-|

"IJ• «I -^»^

1

1

— ^f TM" •

"7

i

i

_j

"7— TT]

•i

h—

I

.-

-

yt>£* V-RIHfc; STRESS- lOIttLiri 35) RUN TUO t.&USTftF OH

PHSY.'>

3^ 7.-&

8.5343

PQtTi

ftUTO CC&LING

Figure 3

GEG

A-7
i !

§ I § § S

A-8
1 o

A-9
t * ft S

A-10
e:

UJ

t, * fc 8

* <? *
O)

V)

f 9

A-12
ATTACHMENT D

NEW METALIZATION MASK

FOR TERMINAL BOARD #1
|

0«SH NO

-OQ\

HONEYWELL NO

2ZOO45G.I

0.59O±.001

0.4901.001

0.115 t.OOZ

o

i

ON ^ aE^p, FIELD

3C.i t

10 PIKC1

0.350±.OOZ

SEE DET^^V ^

an I

•tool

CODE

IOCNT

.OZO i .001

.020i.001R

IPLKCES*

DE1MV. K

TYP. OF 10 PIACES

UNRELEASED

NOT UMDER

ECO CONTROL

PART OH

IOENTIFTINC NO

NOMCNCLATUKE O

DESCRIPTION

JO*

(,-13-SS

Otv ENGftG MGMT

POOD ENtMG MGM1

HONEYWELL INC

SOLID 5t»It CLCCIKOKtCS CCNTt*

MINNEAPOLIS. MINNESOTA

-TERM\N/KL BOARD * \

CODE IOENT NO

34168

to / 1 ' Is""' \ <* \
ATTACHMENT E

CHARACTERISTIC OVER TEMPERATURE FOR

CIRCUIT COMPENSATION RESISTORS AND DIODES
u

U

a.

E

0)

(0

o

Q_

(U

a.

E

(0

LO

(

s n lE

A D 52

E-l
o

u

U

C

3 n l*A D 52 J-° X)

(S3

in (S3 in

t\j PJ —

apoiQ

E-2
<

D

-aoOoo

in

£

CM

oo00^en^ (M•oo

in

fM

E3
ATTACHMENT F

VACUUM PUMPING STATION SKETCHES
F-l Reference Pressure Vacuum Pumping Station

(Side View)
-

sors

fD

ft) OfD-sCD-sfDn>nc:c-oc. -atoO3

F2
ATTACHMENT G

LETTER TO NASA DOCUMENTING CONCERN

WITH DEUTSCH CONNECTOR NUMBER
Honeywell

June 28, 1985

Mr. Thomas Marshall

NASA

Marshall Space Flight Center

Huntsville, AL 35812

Dear Tom:

Enclosed are the connector prints we discussed in our recent phone

conversation. Our concern is that the print on Page 2 of the Amendment 1

to RC7001 references connectors RES1231-E1005N and RES1231-D1005N and the

print we received from Deutsch (77014-10-5PN) references RES131-A1005*(1).

We have asked Deutsch to confirm what connector they are currently

supplying to Rocketdyne but we have not yet received a reply from them.

We would like you to see if you can determine the current Rocketdyne

connector print number and if possible the corresponding Deutsch print

number. If Deutsch sends us a print number, we will send it to you for

confirmation that it is the one you need for your transducer.

We have two related questions for you that are related to the connector.

In our conversations with Deutsch, they said that the connector

77014-10-5PN will not withstand 20,000 PSI and it is not what they would

consider a cryogenic connector. The questions we have are:

1. Do you want or need a 20,000 PSI connector?

2. Do you want or need a cryogenic connector?

We are looking forward to hearing from you soon concerning these questions

we have about the connector.

Sincerely,

HONEYWELL, INC.

Uohit J. Shea s

Sensor Engineer

cc: P.J. Anderson, MN14-4C40

P. Nussbaum, MN14-3B35

P. Towne, MN14-4C45

jsnasaltr

HONEYWELL INC.. SOLID STATE ELECTRONICS DIVISION

120. T HIGHWAY 55. PLYMOUTH, MINNCG"'T-\ 55441, TELEPHONE 612/541-2300
PREPARED BY

j J. Berroteran

•

FSCM NO. 02602

Rockwell International Corporation

Rocketdyne Division

Canoga Park, California

SPECIFICATION

NUMBER A. ..•LENT 1

•001

TYPE

PROCUREMENT

DATE

28 July 1981

SUPERSEDES SPEC. DATED:

REV. LTR.

PACE 1 of 2

TRANSDUCER, PRESSURE - LOW LEVEL ANALOG OUTPUT

NOTE: THIS AMENDMENT FORMS A PART OF AND SHALL BE ATTACHED TO

SPECIFICATION RC7001, REVISION M, DATED 3 APRIL 1981.

Page 36, Figure 1A [DELETE THE EXISTING FIGURE AND REPLACE WITH

THE FIGURE 1A ATTACHED HERETO)

RELEASED

DOCUMENT

>•»* CMANf.f)
AMENDMENT 1

Page 2

NORTH AMf.RICAN ROCHWEli C<*in>«ATION

coot IMKI HO ana

— 3.500 MAX -

l.OOODIA

PERMANENTLY

MARK TO CORRESPOND

WITH FIG 4 WIRING(tYP)

2) IDENTIFICATION

\ ^ AREA j:

(EITHER A

SIDE! f=pT

SEALING SURfACE

BETWEEN INSIDE DIA

MACHINE SLOT IN AND 1.05 DIA

TYPE NO -30,-50,1-70 ONLY

I 3500 PSIA RANGE)

OPTIONAL PRESSURE

PORT CONFIGURATION

DIA 4 HOLES

EQUALLY SPACED

RANGE

MARKING AREA

LOCATE. MASTER KEYWAY 6F

CONNECTOR IN LINE WITH BODY

CENTER INE WITHIN ±4

DEGREES 2 PLACES

\

WITHIN .365 DIA MAX

5

RES1Z31-E1005N

RES1231-D1005N CONNECTOR

2 RhOD

OPTIONAL CONFIGURATION SUBJECT TO ROCKETDYKE APPROVAL,

/ \

0 FIGURE 1A

THREADED CONNECTOR CONFIGURATION)

Y> MARK EDGE Of FLANGE PER PARA 3.3.3.2 . (OPPOSITE SIDE OPTIONAL)

3. TOLERANCES: .XX - ± .03. . XXX - ± .010.

7) IDENTIFY PER PARA 3.3.3.1 WITHIN CONFINES OF SPACE LIMITATIONS.

T) THIS SURFACE TO BE FREE OF NICKS. SCRATCHES AND OT1CR

IMPERFECTIONS WHICH WOULD IMPAIR ITS SEALING FUNCTION.

|l! M 11 r-T " 1 '0
NORTH AMERICAN ROCKWELL CORPORATION

CODE IDENT. NO. 02602

NUMBER

RC7001

REVISIO N LETTER

[* M 1

PACE >8.

.DUAL BRIDGE PRESSURE SENSOR

THREADE D CONNECTOR

PRESS

BRIDGE

i 1

PRESS

BRIDGE

I 2

EXC

OUTPUT

- EXC

80% CHECKOUT

- OUTPUT

+ EXC

+ OUTPUT

~ EXC

_ 80% CHECKOUT

- OUTPUT

THREADE D

 r CONNECTOR* 2

FIGURE 2A
10-5 ARR

• •"> ", n 

- - ./ j u -

. 6875-2[t

4. FINISH:

SHELL-ELECTRO POLISH

CONTACTS -GOLD PLATED

MATERIAL:

SHELL- STAINLESS STEEL

CONTACTS - HIGH NICKEL IRON ALLOY

INSERTS - COMPRESSION GLASS AND RUBBER:

2. CONTACT IDENTIFICATION IS IN CONTRASTING COLOR TO

INSERTS.

•i i

NOTE: i. INSERTS ARE CONTINUOUS DIELECTRIC.
1 1

-.

• . n i o — >•

,':/C

c\

- - ., , __ ••-•••••• * • . • •

Nli,-/ '-^LL'XSc :--Ek :-:.•.). ,.

"oi,\f..t,i- !'•• :•'• ;• o :;'' s'jij

•3A'" •

I0-u-?o

1 1 /-''/ /r ^'/ J'-'

•~A^-(/

.275^.02 5

T

INEF-2A

C H K

P£

APP O

SiGNAT U RE i DAT E

SCAL E MOfxJE WT

RLCEPTACLE, CONNECTOR

THREADED COUPLING

WELD MOUNTING SPECIAL

HERMETIC DBA SERIES

REFERENCE ROCKETDYNE

ii KLS 1231- A10U'.>::G)

- ENVELOPE -

CP

MATL. 7 ,

i CODE ' •>

The Deutaoh Coznpan

ELECTRONIC COMPONENTS DWISIO:

t

Municipal Airport

Banning, Cdifoniia

B

owe

SIZ E

7701'4-10-5PN

COD E

11139

SHEE T 1 OF
Page Seven — to be inserted into the May Monthly Report
I

•X

PAGE SEVEN

2.7 Miscellaneous

2.7.1 Vibration Requirements

Re: 1. NASA Contract .No. NAS8 34769, 8/26/82

Exhibit 'A', Section B.I

2. Honeywell's Technical Proposal, 7/12/83,

Sections 2.3 (Pages 2-5 to 2-7), 2.6.1.2 (Pages

2-15 to 2-18), 2.6.1.4 (Page 2-36 and 2-37).

3. Working session at NASA/MSFC, 9/26/84

Attendees:

P.J. Anderson Honeywell Inc.

P. Golley NASA/MSFC

H. Burke NASA/MSFC

B. White NASA/MSFC

C. Kirby NASA/MSFC

4. September Monthly Report, Section 2.7.1.

5. Working Session at NASA/MSFC, 11/20/84

Attendees: P.J. Anderson, Honeywell Inc.

T. Marshall, NASA/MSFC

C. Kirby, NASA/MSFC

B. White, NASA/MSFC

During a November working session (Reference 5), Honeywell

proposed a "half-sine pulse" shock test method to satisfy

NASA's TSRS requirement as described in Reference 4. The

details of Honeywell's proposal were outlined in Attachment

•F1 of our November monthly report. T. Marshall, et al

accepted the Honeywell proposal for the shock testing and

evaluation of the Experimental Transducer.

2.7.2 Test Plans: Experimental Transducer

Re: 1. Attachment 'F1, August Monthly Report

Working Session at NASA/MSFC 11/20/84

Attendees: P.J. Anderson, Honeywell, Inc.

T. Marshall, NASA/MSFC

B. White, NASA/MSFC