Application Note

Light Emitting Diode

LED Mounting Process Techniques

Table of Contents
1. Overview ........................................................... 2
2. Applicable LED part/series numbers ................ 2
3. Solder Printing Process ..................................... 3
4. LED Placement ................................................. 7
5. Reflow Soldering ............................................ 13
6. Verification of LED Mounting Performance... 17
7. Other Considerations....................................... 18
8. Summary ......................................................... 20

This document contains tentative information, Nichia may change the contents without notice.

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Application Note
1. Overview
When manufacturing a luminaire using LEDs, the LED mounting technique is a critical aspect.
Regardless of how good the LEDs' characteristics may be, improper mounting methods/conditions
may significantly affect the LED's characteristics, and in some cases cause the LEDs not toilluminate.
This application note covers the importance of how the mounting process is performed anddiscusses precautions that customers should take into consideration for each stage of the mounting
process.

Light Emitting Diode

2. Applicable LED part/series numbers
The contents described in this application note apply to the LEDs shown in Table 1, Nichia's LEDs
for general lighting.
Table 1. Nichia LEDs for General Lighting
Category

NICHIA
757
SeriesPart Number 1

Package Appearance(One example) (mm)NFSW757H-V1
NF2W757H-F1
NFSW757H

3×3×0.80

NF2W757GR-V4
NF2W757GR-V3P7
NF2W757GR-V3
NF2W757G-V3F1
NFSW757G-V3
NF2x757GR-V1U4
NF2x757GR-V1
NFSW757G-P5V1
NFSx757G-P5
NF2x757G-F1
NFSx757G

3×3×0.65

NE2B757G
NF2E757GR
NE2G757G
NFSY757G
NE2R757G-P6

3×3×0.65

NF2W757G-MT

3×3×0.75

Category

NICHIA
119/219
Seriesetc.

Part Number 1

Package Appearance(One example) (mm)

NVSW119F-V1
NVSW219F-V1
NVSW119F
NVSW219F
NVSW119D
NVSW219D

3.5×3.5×2.3

NVSx119C
NVSx219C

3.5×3.5×2

NCSC119B-V1
NCSC219B-V1
NCSB119B-V1
NCSB219B-V1
NCSE119B-V1
NCSE219B-V1
NCSG119B-V1
NCSG219B-V1
NCSA119B-V1
NCSA219B-V1
NCSR119B-V1
NCSR219B-V1
NVSA119B-V1
NVSA219B-V1
etc.

3.5×3.5×2

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Light Emitting Diode

Application Note
Package Appearance(One example) (mm)Category

Part Number 1

NICHIA
229
Series

NWSx229A
etc.

4×4×2.3

NICHIA309/319
Series

NVSW309B
NVSW319B
etc.

3.5×3.5×2.35

NICHIA
385
SeriesNF2W385AR-V2
etc.

NICHIA
585
SeriesPackage Appearance(One example) (mm)Category

Part Number 1

NICHIA
B35
Series

NV4WB35AR
NV4WB35AM
etc.

3.65×3.65×0.73
3.65×3.65×0.76

6.5×5.8×0.8

4×3.6×2.05

NICHIA
481/484
486/488
SeriesNFMW488AR-V1
NFMW481AR
NFMW484AR
NFMW486AR
NFMW488ARetc.

NF3W585AR-V1
NF2W585AR-P8
NF3W585AR
NF2W585AR
etc.

4×3.6×2.05

NICHIA
E11
SeriesNFSWE11A
etc.

1.1×1.1×0.27
1.1×1.1×0.30
1.1×1.1×0.35

NCSxE17A

NICHIA
519
Series

1.7×1.7×0.27
1.7×1.7×0.30
1.7×1.7×0.35

NVSW519A
etc.

3.5×3.5×2.35

NICHIA
144
Series

NV4x144AR
NV4x144AM
etc.

1.7×1.7×0.35

5×5×3.15

NCSCE17A
NCSBE17A
NCSGE17ANCSAE17A
NCSRE17A
etc.

NICHIA
149
Series

NV9W149AM
etc.

7×7×3.1

NVSxE21A
etc.

2.1×2.1×0.27
2.1×2.1×0.30
2.1×2.1×0.35

NICHIA
E17
SeriesNICHIA
E21
SeriesNote:
1
x = W (White) or L (Warm White)

3. Solder Printing ProcessThis section covers the first part of the LED mounting processes, the solder printing process forthe solder paste. The other two parts of the process are the LED placement and reflow soldering.
Solder printing refers to applying the solder paste to the soldering pad pattern on the PCB.
In this process, it is necessary to set the optimum soldering pad pattern and metal solder stencil
aperture, prepare the solder paste, and adjust the printing conditions in order to obtain optimalsolder printing conditions.
3.1 Recommended soldering pad pattern and metal solder stencil aperture
Nichia performed tests for mounting Nichia LEDs and provides customers with the recommended
dimensions for the soldering pad pattern and metal solder stencil aperture. Refer to the "Soldering"
section of the part specifications for these recommended dimensions. An example of these
diagrams is shown in Figure 1 below for reference.

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Light Emitting Diode

Figure 1. Recommended soldering pad pattern and recommended metal solder stencil aperture(example: part number NFSW757H-V1 Specification)

3.2 Adjusting the metal solder stencil aperture
Depending on the customer's mounting conditions/equipment, it may not be possible to use
Nichia's recommended metal solder stencil aperture. In that case, customers will need to adjust themetal solder stencil aperture and perform mounting tests until the best design with that equipment
can be verified.
For example, if after mounting it was confirmedthat the part floated, the metal solder stencil
aperture would need to be adjusted. Figure 2
shows an example.

（Unit: mm）

Figure 2. Example metal solder stencil aperture asa countermeasure against part floating
3.3 Solder Printing Conditions
In the solder printing process, it is important to print solder paste in the correct position on the
PCB and with the correct amount and shape. To do this efficiently, it is necessary to prepare thesolder paste and adjust the printing conditions as described below.
3.3.1 Preparing the Solder Paste
In most cases, solder paste stored in a refrigerator is not able to be used immediately. It isnecessary to stir before use. The purpose of stirring the solder is to evenly distribute the solder
particles and flux that may have become uneven while the solder was stored in the refrigerator. If
the solder paste is uneven, it will not be possible to obtain good rollability.
Note that if the stirring time is too long, the solder temperature will rise, and the flux will
deteriorate. Additionally, in order to avoid moisture absorption of the solder paste due tocondensation, open the container after it has returned to room temperature.
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Light Emitting Diode3.3.2 Adjusting the Printing Conditions
In order to print the solder paste at the proper position on the PCB, the metal solder stencil
aperture and PCB recognition data must be entered and set in the printing machine, and analignment test must be performed.
Adjust the squeegee conditions and the solder stencil separation conditions to print with thecorrect amount and shape. The speed, pressing pressure and angle of the squeegee affect theamount and condition of the solder paste filling the metal solder stencil aperture. Additionally, thespeed of the separation and the distance affects how smoothly the stencil separates from the solder
paste as it is removed. These are also affected by the thickness of the metal solder stencil, theaperture pattern, and the surface roughness of the aperture wall.
In order to prevent the occurrence of solder bridges, etc. and maintain optimal printing conditions,adjust the cleaning method, conditions, and frequency of the metal solder stencil.
For reference, Table 2 on the following page shows an example of print condition settings for
Panasonic screen printer SPG. The printing conditions change depending on the type ofequipment, the length and rigidity of the squeegee, etc.
Table 2. Example of printing condition settings (Reference: Panasonic screen printer SPG)
Setting

Print Setting Items

Details

Conditions

The machine has a setting for either "Single"
Action Mode

Single(one-way printing) or "Double" (two-way
printing)

Printing Speed
Pressing Pressure

F➝R

50mm/sSqueegee travel speed (front➝back)R➝F

50mm/sSqueegee travel speed (back➝front)

F➝R

30.0×0.01N

R➝F

30.0×0.01N(Per Squeegee 1mm)

Printing

Downward Speed

7.0mm/s

Conditions

Force that the squeegee applies to the metal
solder stencil (front➝back)Force that the squeegee applies to the metal
solder stencil (back➝front)
Speed of separation required for stability
Gap between metal solder stencil and PCB,

Clearance-0.20mmtypically "-0.3" to "-0.1" to improveadhesion

Lift

The board separation distance required for a

Advanced

Downward

Settings

Stroke3.0mm

stable solder paste release:
Consider deflection of metal solder stencil
and extension of solder

Squeegee Material

2

Plastic

Select either metal, urethane, or plastic

Squeegee Length

370.0mm

Length of the squeegee

Squeegee Angle

60°

The angle of the squeegeeThis document contains tentative information, Nichia may change the contents without notice.

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Application Note
Operation
1 round trip
Cleaning

Light Emitting Diode2 round trips

Interval

Process

Speed

Method 3

SuctionEvery 5Going

80mm/sDry

ON

SheetsReturning(Frequency)

Operation: OFF

Going

80mm/sDry

ON

Every 20

Returning

80mm/sDry

OFF

SheetsGoing

40mm/sWet

OFF

Returning

80mm/s

Dry

OFF

Note:
2
Squeegee material: The materials for the squeegee are metal, urethane, and plastic. Select thesqueegee suitable for the chosen application according to the following.
Metal squeegee: The material is hard, and it is easy to adjust the amount of solder uniformly;
however, the metal solder stencil is easily damaged, and the life is short.
Urethane squeegee: Although the life of the metal mask is extended because the material is soft,the squeegee bends if the aperture size is large, the amount of solder is reduced (not uniform) inareas where the squeegee bends.
Plastic squeegee: It has the good properties of the metal and urethane options; however, regularreplacement is necessary due to the occurrence of normal wear.
3

Method of cleaning the metal solder stencil:
Dry: Removal of solder particles and flux attached to openings and back of metal solder stencil.
Wet: Removal of thin film of residual flux on the back of the metal mask (which causes solder
particles to adhere more easily).
3.4 Visual inspection after solder printing
Nichia recommends performing a visual inspection after solder printing to confirm that the solder
paste can be stably printed in the proper position and in the proper amount and shape.
Figure 3 shows an example of a visual inspection. Perform an image analysis to check theposition, amount, and shape of the solder.

Figure 3. Example of the data for a visual inspection after solder printing(Reference: CKD VP6000M-V)
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4. LED Placement
This section covers the second part of the LED mounting processes, the LED placement. LED
placement refers to mounting the LED on a soldering pad pattern to which solder paste has been
applied.
In this process, it is necessary to set the optimum nozzle shape and suction method and adjust thesuction and mounting conditions in order to obtain optimal conditions for LED placement. During
this process, care must be taken to avoid applying any excessive force to the light emitting surface
or the lens part of the LED. Excessive force may affect the reliability and optical characteristics.

Light Emitting Diode

4.1 Recommended Nozzle Shape
Nichia performed tests to provide customers with a recommended nozzle configuration. Refer tothe "Soldering" section of the specifications which may contain a diagram like the one shown in
Figure 4.
For products that do not have the recommended nozzle shape described in the specification,
contact Nichia directly to discuss this further.

Figure 4. Recommended nozzle shape (example: part number NVSW119F-V1 Specification)
For nozzle shapes for LEDs with an integrated lens, when designing or choosing the nozzle shape,
having the inner surfaces with C or R corners enables a smoother operation for the suction pick-up
and reduces the possibility of pick-up errors.

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Light Emitting Diode4.2 Nozzle Suction Method
Nichia determines the ideal nozzle shape and suction method that is optimal according to the shape
and weight of each Nichia LED and takes this into consideration when preparing the embossed
carrier tape.
There are two major methods for LED suction during mounting:
One method is to stop the suction nozzle on the top surface or the middle surface of the embossed
carrier tape and suck the LED (i.e. vacuum suction). The other is a method in which a suction
nozzle is inserted into the embossed carrier tape until it reaches the LED as close as possible (i.e.
normal suction).
① Vacuum suction: By suctioning air from the height at which the nozzle does not contact theLED, the only load that may be applied to the lens is the suction pressure at the time ofsuction.
② Normal suction: Where vacuum suction is not possible or difficult, stable suction is madepossible by bringing the nozzle closer to the LED and then applying suction.

NozzleLED

Embossedcarrier tape
Suction from the top of theembossed carrier tape

Suction from the middle ofthe embossed carrier tapeFigure 5. Vacuum suction

Insert the nozzle inside of the embossed
carrier tape and then apply suction

Figure 6. Normal suction

Refer to the drawing shown in Figure 7 in the "Recommended nozzle height" section of theassembly precaution application note for each LED part number for the LED suction method andnozzle suction/insertion position.
For products that do not have the recommended suction/insertion height described in theapplication notes, contact Nichia directly to discuss this further.

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Light Emitting Diode

Figure 7. Recommended nozzle height (example: part number NFxW585AR
Assembly Precaution application note)
If the pick point of the nozzle is too high,- it may cause insufficient suction power leading to picking errors (e.g. the nozzle's failure to
pick/lift the LED into the air, incorrect picking causing the LED to tilt when in the air).
If the pick point of the nozzle is too low,
- it may cause issues (e.g. causing the embossed carrier tape to shake, causing the tape pocket todeform) leading to picking failure and/or damage to the LED.
4.3 Optimizing the Nozzle Suction Force
Adjust the nozzle suction force to the optimal condition. In a non-optimized state, depending on
the shape and material of the LED, it may not be picked up, or the LED may adhere to the nozzle
during the mounting process.
For LEDs with an integrated lens, air leaks may occur between the nozzle and the LED, which
may cause the LED to not be picked up properly. If this occurs, adjust the nozzle to a more
appropriate suction by increasing the nozzle suction force and/or reducing the nozzle innerdiameter to reduce the potential for air leaks. When reducing the inner diameter of the nozzle,
ensure that the clearance takes into consideration the dimensional tolerances to ensure there is nocontact with the LED lens.
NozzleWhere air leaks occur(The gap between the nozzle tip and the LED)

NozzleLED

LED

Air LeakFigure 8. Air leak at the time of LED suction (example: part number NV9W149AM)
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4.4 Tape Feeder Types

Light Emitting Diode

Nichia recommends the use of a motorized tape feeder with a low feed vibration. For example, in
air-type tape feeders, where the feed vibration is larger than that of motorized tape feeders, suction
failure may occur (e.g. LEDs move within emboss carrier tape, or a tilted suction.)

Figure 9. Tape feeder with large vibration

Figure 10. Tape feeder with small vibration

4.5 Feeding Speed of the Tape Feeder
The feed speed of the tape feeder needs to be adjusted to the optimum speed according to theshape of the mounted LED. For example, a simple square-shaped LED can be picked-up andplaced at a high speed; however if it is an LED with an integrated lens, it will be difficult to pickup and place at that same high speed. Since LEDs with integrated lenses tend to have a high centerof gravity, if the feed rate is too high, suction failure is likely to occur due to rolling or tilting of
the LED due to vibration.

Figure 11. Tape feeder feed rate (fast)

Figure 12. Tape feeder feed rate (slow)

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Light Emitting Diode

Additionally, since the LED lens is a resin material, it is tacky and the LED lens may stick to theembossed carrier top cover tape; if the tape feeder speed is too high, the suction occurs before theLED peels off from the top cover tape, which causes suction failure.

Figure 13. When the tape feeder feed rate is fast and the LED sticks to top cover tapeFigure 14. When the tape feeder feed rate is slow and the LED sticks to top cover tape

4.6 Peeling Position of the Top Cover TapeAs mentioned previously, depending on the type of pick-and-place machine used and the shape of
the LED, the LED may move within the embossed carrier tape. When this occurs, if the top covertape peels off early before suction, extra space is created above the top of the LED. This extra
space makes it easy for the LED when affected by vibration to move up and down, leading totilting of the LED.
As a countermeasure, make adjustments to the tape feeder to ensure the top cover tape is peeled
off immediately before suction. This regulates the vertical movement of the LED and reduces thetilting of the LED.

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Light Emitting Diode

Figure 15. Removing the top cover tape in the normal position

Figure 16. Removing the top cover tape just before suction

4.7 Nozzle placement pressure when placing the LED
When placing the LEDs on the PCB, pay attention to the amount of nozzle placement pressure
against the PCB surface. If the placement depth of the nozzle is insufficient, the LEDs may float or
shift after reflow. If the placement depth is too much, the LEDs will be over stressed and solder
balls may occur. Nichia recommends a placement depth of 0.2 mm.
As shown in Fig. 17, the relationship between the placement depth and the placement speed
determines the size of the nozzle's placement pressure on the LED. A large placement pressure
leads to LED defects (e.g. package cracks, disconnections, etc.). If the placement pressure of thenozzle is within 3N, there should be no problem with the LEDs. However, the PCB could warp
and/or other factors may affect the placement pressure. Perform a verification test using the actual
process and placement conditions to ensure that the LEDs do not have a defect after placement. If
there is a problem with the LEDs due to the placement pressure of the nozzle, takecountermeasures to reduce the placement speed.
For LEDs with an integrated lens, avoid applying any nozzle placement pressure to the lens.
Excessive pressure on the lens may cause scratches, chipping, peeling, deformation of the LED,
internal disconnections, and/or reliability issues.

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Application Note
25

(N)
Placement
Pressure (N)Placement Pressure

25

Placementpressure
must notexceed 3N

Placement Depth 0.6mm

Placement Depth 0.6mm
PlacementDepth
Depth0.4mm
0.4mm
Placement

PlacementDepth
Depth0.2mm
0.2mm
Placement

0

0

20
20 40
40 60
60 8080 100
100
Placement
PlacementSpeed
Speed (%)(%)

Press 0.2mm

Light Emitting Diode

Figure 17. Placement pressure due to placement depth

Figure 18. Nozzle Placement Depth

5. Reflow Soldering
This section covers the third part of the LED mounting processes, the reflow soldering. Reflow is
the process of placing the components that have been mounted on the solder paste into a hightemperature reflow oven to melt and bond the solder.
In this process, it is necessary to set the optimum reflow conditions in order to obtain a goodsolder joint condition.
5.1 Recommended Reflow Conditions
Nichia performed mounting tests to provide customers with recommendations for the reflow
soldering conditions (i.e. reflow profile). Refer to the “Soldering” section of the specifications
which details the reflow soldering conditions like the one shown in Figure 19.

Figure 19. Recommended Reflow Soldering Condition(example: part number NFSW757H-V1 Specification)
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5.2 Details of the Reflow Soldering Profile
The reflow soldering profile has three zones: Pre-heat, Reflow, and Cooling. The following shows
the role of each zone.
Pre-heat zone:
The flux contained in the solder isactivated to remove the oxide film on the
PCB surface.

Light Emitting Diode

Reflow zone:
The heat melts the solder to form an alloy.
Cooling zone:
The alloy is completed by the coolingtemperatures.

Figure 20. Example of a Reflow Profile
5.3 Adjusting the Reflow Soldering Profile
The following describes how to adjust the reflow profile. Refer to Figure 21.
① Pre-heating speed (Reference: 1 to 5℃/sec)
When it is large: Solder balls are created 4, possibility of voids increases 5② Pre-heat temperature
If it is high: The solder wettability declines 6③ Pre-heat time
If it is long: The solder wettability declines④ Reflow heating speed (Reference: 1 to 5℃/sec)
If it is small: The solder wettability declines 6
When it is large: Solder balls are created 4, possibility of voids increases 5⑤ Reflow peak temperature
If it is too low: The solder wettability declines, possibility of voids increases 5
If it is too high: Solder balls are created 4, the solder wettability declines⑥ Reflow time
If it is short: possibility of voids increases 5⑦ Cooling speed (Reference: 1.5 to 2℃/sec)
If it is large: The cause of component damage due to thermal shock
If it is small: The cause of the decrease in solder joint strength and positional deviations⑧ Cooling temperature
When the temperature at the time of PCB discharge is high: Warpage occurs within the PCBThis document contains tentative information, Nichia may change the contents without notice.

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Note:
4
If solder balls are created, it will lead to a cause of a short circuit and insulation failure.
5

An increase in voids leads to a decrease in bonding reliability and heat dissipation.

6

If the solder wettability decreases, the bonding area decreases, which leads to the decrease inbonding reliability.
Temperture⑤④

Light Emitting Diode

②

①

⑥
⑦

③

⑧
Time

Figure 21. Description of where the reflow conditions are adjusted

5.4 The differences between an air reflow atmosphere and a nitrogen reflow atmosphere
Nichia recommends nitrogen reflow atmosphere, and the specifications contain the following
statement.
During reflow soldering, the heat and atmosphere in the reflow oven may cause the opticalcharacteristics to degrade. In particular, reflow soldering performed with an air atmosphere may
have a greater negative effect on the optical characteristics than if a nitrogen atmosphere is used;
Nichia recommends using a nitrogen reflow atmosphere.
5.4.1 Pros of a nitrogen reflow atmosphere
Optical degradation due to reflow is mainly caused by discoloration of the package resin.
Discoloration of package resin is caused by deterioration and oxidation of resin by heat of reflow.
By using nitrogen reflow, discoloration of the resin due to oxidation is suppressed, and thedecrease in luminous flux is improved accordingly.
Nitrogen reflow also has the advantage of preventing solder oxidation, leading to improved solder
wettability.

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5.4.2 Nitrogen reflow concentration settings
In order to obtain the improvement effect by nitrogen reflow, it is necessary to increase thenitrogen concentration to about 500 ppm of oxygen concentration.
5.4.3 The luminous flux reduction rate for an air reflow atmosphere
For LEDs with ceramic packages, the luminous flux loss is approx. 1% even in an air reflow
atmosphere. Also, as shown in Figure 22, some resin packaged LEDs are not affected as muchdepending on the material and the conditions of the air reflow atmosphere.

IF=65mA, TA=25℃, Sample size: 25pcs (Avg.)

120
100
Relative Optical Power (%)

Light Emitting Diode

Part No. NF2W757G-F1
Reflow Soldering (Atmospheric Air) 260℃ for 10sec.

80
60
40
20
0
0

1
Reflow Passing Frequency

2

Figure 22. Luminous flux reduction rate confirmation data in air reflow(example: part number NF2W757G-F1)

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6. Verification of LED Mounting Performance
After completing necessary adjustments for the mounting process, conduct inspections/tests tocheck if there are any abnormalities in the soldering conditions or LEDs. Table 3 shows anexample of items to verify.
Table 3: Example of inspection/tests to verify the mounting processes
Item to verify

Verification Checklist

Probable cause(s) when there is an abnormality/failure

Are there any scratches,
chips, or

The nozzle placement pressure is large.

peeling/delamination?
Is the LED unevenly

Light Emitting Diodesoldered to the PCB? Or
only soldered on one side?
1

Visual Inspection(Visual, Image)

Are there any solder balls?
Is there a good solder fillet
shape?
Is there any floating, tilting,misalignment. Does thesolder not fully cover thesolder pad?

Insufficient amount of solder, improper soldering padpattern, improper metal solder stencil aperture.
Excessive amount of solder, improper reflow profile.
Insufficient amount of solder, improper soldering padpattern, improper metal solder stencil aperture, improper
reflow profile.
Insufficient amount of solder, improper soldering padpattern, improper metal solder stencil aperture, improper
reflow profile.
Open circuit due to insufficient amount of solder. Short

2

Lighting
Inspection

Is there an emission failure?

circuit due to excessive amount of solder (e.g. a solder
bridge). Disconnection due to excessive nozzle placement
pressure. (Identify the cause using the X-ray examination)

3

4

X-ray Inspection
Shear Strength
Test

Are there any voids?

Improper reflow profile.

Are there any solder balls?

Excessive amount of solder, improper reflow profile.

Is there sufficient resistanceto shearing stress?

Insufficient amount of solder, improper soldering padpattern, improper metal solder stencil aperture, improper
reflow profile.

After confirming with inspections/tests that there are no abnormalities/failures, the verified
mounting processes can begin to be used for the chosen application.
Since the mounting status changes due to slight differences in setting conditions, as well as
differences in the solder paste, PCB, and mounting equipment/parts, etc.: always check and control
the soldering status after mounting. By using an automatic solder visual inspection system (i.e. onethat can provide an image where it is easy to judge if the image is good or if there is a defect), it ispossible to improve the efficiency of work and reduce the dependence on the operator's skill
compared to visual inspection.

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Even if customers apply Nichia’s recommended conditions, the mounting processes may not be
successful. It is best for customers to understand the trends for the processes chosen for theapplications, accumulate actual test data, and be able to respond daily to any necessarychanges/adjustments to the processes.

7. Other Considerations
This section describes the notes and other details regarding the jigs and operations related tomounting LEDs.

Light Emitting Diode7.1 Cautions about the transfer board
When using a transfer board for machine mounting, the PCB is placed on the transfer board(transfer jig) to move throughout the mounting process; however, if the transfer board is warped,
mounting defects will occur. In addition, even if there is no warpage in the transfer board in theearly stages of production, warpage may occur if the same transfer board is used for the reflow
process a few dozen times. It is recommended to make sure that warping does not occur bypassing the material that would be used for the transfer board through the reflow process a few
dozen times before using it during actual production use. For reference, materials typically used
for transfer boards include Bakelite, glass epoxy, etc.

Figure 23: Transfer board appearance
7.2 Precautions for handling the mounted PCB
The most common failures for LEDs are wire breakage and package cracks due to external
stress/pressure applied to the LED. Special care should be taken when handling the LED after
mounting it on the PCB.
Customers should take careful note of the following examples of situations that cause thesefailures:- Stress/pressure is applied to the PCBs when bending or twisting occurs during the PCB
separation process.
- Stress/pressure is applied to the LED when LED-mounted PCBs are stacked on top of each other.
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7.3 Cautions for the lighting inspection of the mounted PCB
As mentioned in section 7.2, there are many cases for LED failure (i.e. overcurrent or reverse
current which can often occur during the lighting inspection after the mounting process,during/after product assembly, etc.).
Customers should take careful note of the following examples of situations that cause thesefailures:

Light Emitting Diode- When a test voltage is applied to the PCB during the lighting inspection, a large current
exceeding the maximum rating temporarily flows through the LED due to the inrush current. (SeeFigure 24)- When a test voltage is applied to the circuit of the PCB (hot-wire connection) by a probe while
the power is on (i.e. during lighting inspection), a large current exceeding the maximum ratingflows through the LED.
- The reverse current from the power supply during the lighting inspection will cause the Zener
diode to short circuit and cause the LED not to illuminate.
Current

Peak Current
Inrush Current
Steady Current

Time

Figure 24. Example of an inrush current waveform

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8. Summary

Light Emitting DiodeAs detailed within this application note, the mounting process for LEDs has many details that need
to be verified or noted for each process stage: solder printing, LED placement, reflow soldering.
Achieving optimal mounting conditions is a very important factor in producing good LED
lighting. Customers should refer to the contents covered in this application note and establish
conditions and methods suitable for the mounting process for the chosen application.
In this application note, Nichia has provided an example of how to adjust the basic mounting
processes and how to handle mounting defects; however, the method described here may not be
the best solution. Depending on the specific product or mounting equipment that is being used it
may be optimal to adjust the mounting processes according to instructions/methods detailed by the
product/equipment which may be different than those described here. Nichia will continue toaccumulate data on LED mounting technology and provide useful feedback to customers on this
topic. If any other issues other than those described in this application note should occur during themounting process for the chosen application, customers should contact Nichia to discuss thedetails.
The designations within this document to indicate a certain LED series are merely used to make iteasier to grasp the product specifications at a glance for the Nichia part numbers listed in Table 1:
Nichia LEDs for General Lighting. These series numbers, along with Nichia’s part numbers in
Table 1, are not related nor bear resemblance to any other company’s product that might bear a
trademark.

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Disclaimer
This application note is a controlled document of Nichia Corporation (Nichia) published to provide
technical information/data for reference purposes only. By using this application note, the user
agrees to the following:・ This application note has been prepared solely for reference on the subject matters incorporated
within it and Nichia makes no guarantee that customers will see the same results for their chosen
application.

Light Emitting Diode・ The information/data contained herein are only typical examples of performances and/or
applications for the product. Nichia does not provide any guarantees or grant any license underor immunity from any intellectual property rights or other rights held by Nichia or third parties.
・ Nichia makes no representation or warranty, express or implied, as to the accuracy, completenessor usefulness of any information contained herein. In addition, Nichia shall not be liable for any
damages or losses arising out of exploiting, using, or downloading or otherwise this document,or any other acts associated with this document.
・ The content of this application note may be changed without any prior or subsequent notice.
・ Copyrights and all other rights regarding the content of this document are reserved by Nichia or
the right holders who have permitted Nichia to use the content. Without prior written consent of
Nichia, republication, reproduction, and/or redistribution of the content of this document in any
form or by any means, whether in whole or in part, including modifications or derivative works
hereof, is strictly prohibited.

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NICHIA CORPORATION
http://www.nichia.co.jp

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