Application Note

Light Emitting DiodeLED Pitch and Heat
Dissipation Performance

Table of contents
1. Objective .................................................................. 2
2. Materials and Procedures .................................. 2
3. LED Part No............................................................. 3
4. Measurement Results of Junction
Temperature at Each Pitch ................................. 3
5. Conclusion .............................................................. 6

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Application Note
1. Objective

Light Emitting Diode

Multiple LEDs are generally mounted on a board for the desired light output, as panel lightand illumination for facilities.
Operating a single LED generates high heat; all the more heat is generated when multiple
LEDs are mounted on a board, leading to the decrease in their lifetimes. This is because
the junction temperature (TJ) increases in each LED by mutual interaction.
Minimizing TJ equates to better thermal management, allowing for a longer lifetime.
Therefore, LEDs must be mounted with the optimal pitch among them.
This document shows the optimal pitch between LEDs by demonstrating someconfigurations.

2. Materials and ProceduresFirst, we prepared and used the PCBs as follows (Table 1 and 2).
Table 1. Circuit Board (FR-4)
Surface

Reverse Side
Board: FR-4 (Copper foil on both surfaces)
Board Thickness: 1.6mm
Copper Foil Thickness: 35µm
Reverse Side: Covered with copper foil

Table 2. Circuit Board (Aluminum)
Surface

Reverse Side
Board: Aluminum (Copper foil on one
surface)
Board Thickness: 1.0mm
Copper Foil Thickness: 35µm
Insulating Layer Thickness: 120µm

Second, we prepared the four configurations with LEDs (3 x 3 pcs.) at different pitches; 10,20, 30, and 40 mm.
Table 3. Pitch Pattern
10mm Pitch

20mm Pitch

30mm Pitch

40mm Pitch

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Application Note
Then, the LEDs on each PCB were operated for 15 minutes. Finally, we measured TJ of theLED at the center (cf. Table 4).
Table 4. LED at the Center

3. LED Part No.
Part No.
NVSxx19B

Part No.
NS9x383

Part No.
NF2x757AR-V1

Part No.
NS2x757A-V1

Part No.
NS2x157AR

4. Measurement Results of Junction Temperature at Each Pitch
4.1 Part No. NVSxx19B
Figure 1 shows the TJ measurement results at 1.0W (IF=350 mA) and 2.0W (IF=650 mA) withthe specified pitches. When FR-4 is used, the junction temperature is less affected by thepitch at more than 20 mm at 1.0W, and at more than 30 mm at 2.0W. On the other hand,when the aluminum board is used, the junction temperature is less affected by the pitchat more than 20 mm.
Part No. NVSxx19B Pitch of LED vs TJ

250

TA=25°CFR-4：2.0W
FR-4: 2.0W(If=650mA)(IF=650mA)
FR-4：1.0W
FR-4: 1.0W(If=350mA)(IF=350mA)
AL：2.0W
AL: 2.0W(If=650mA)(IF=650mA)

200

TJ [°C]Light Emitting DiodeWe demonstrated the configurations by using the five models below:

AL：1.0W
AL: 1.0W(If=350mA)(IF=350mA)

150

100

50

00102030

Pitch of LED [mm]4050

Figure 1. Junction Temperature at Each Pitch (Part No. NVSxx19B)
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Application Note
4.2 Part No. NS9x383
Figure 2 shows the TJ measurement results at 0.6W (IF=200 mA) and 1.0W (IF=350 mA) withthe specified pitches. When FR-4 is used, the junction temperature has less interaction at
more than 20 mm both at 0.6W and 1.0W. On the other hand, when the aluminum board
is used, the junction temperature is less affected even by the pitch at 10 mm, enabling
LEDs to be mounted by the narrow pitch.
Part No. NS9x383 Pitch of LED vs TJ

150

TA=25°C
FR-4:
1.0W(If=350mA)(IF=350mA)
FR-4：1.0W
FR-4:0.6W(If=200mA)(IF=200mA)
FR-4：0.6W
AL:1.0W(If=350mA)(IF=350mA)
AL：1.0W
AL：0.6W
AL:0.6W(If=200mA)(IF=200mA)

125

TJ [°C]

7550
2500102030

Pitch of LED [mm]4050

Figure 2. Junction Temperature at Each Pitch (Part No. NS9x383)
4.3 Part No. NF2x757AR-V1
Figure 3 shows the TJ measurement results at 0.6W (IF=100 mA) and 0.9W (IF=150 mA) withthe specified pitches. When FR-4 is used, the junction temperature has less interaction atmore than 20 mm both at 0.6W and 0.9W. On the other hand, when the aluminum board
is used, the junction temperature is less affected even by the pitch at 10 mm, enabling
LEDs to be mounted by the narrow pitch.
Part No. NF2x757AR-V1 Pitch of LED vs TJ

175

TA=25°C
FR-4：0.9W(If=150mA)
FR-4: 0.9W
(IF=150mA)
FR-4：0.6W(If=100mA)
FR-4: 0.6W
(IF=100mA)

150

AL：0.9W
AL: 0.9W(If=150mA)(IF=150mA)
AL：0.6W
AL: 0.6W(If=100mA)(IF=100mA)

125

TJ [°C]Light Emitting Diode10010075502500102030Pitch of LED [mm]4050

Figure 3. Junction Temperature at Each Pitch (Part No. NF2x757AR-V1)
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Application Note
4.4 Part No. NS2x757A-V1
Figure 4 shows the TJ measurement results at 0.2W (IF=65 mA) and 0.45W (IF=150 mA) withthe specified pitches. When FR-4 is used, the junction temperature has less interaction at
more than 10 mm at 0.2W and at more than 20 mm at 0.45W. On the other hand, when
the aluminum board is used, the junction temperature is less affected even by the pitch at
10 mm , enabling LEDs to be mounted by the narrow pitch.
TA=25°C

Part No. NS2x757A-V1 Pitch of LED vs TJ

100

FR-4：0.45W
FR-4: 0.45W(If=150mA)(IF=150mA)
FR-4：0.2W
FR-4: 0.2W(If=65mA)(IF=65mA)
AL：0.45W
AL: 0.45W(If=150mA)(IF=150mA)

TJ [°C]

AL：0.2W
AL: 0.2W(If=65mA)(IF=65mA)

50

2500102030

Pitch of LED [mm]4050

Figure 4. Junction Temperature at Each Pitch (Part No. NF2x757A-V1)
4.5 Part No. NS2x157AR
Figure 5 shows the TJ measurement results at 0.2W (IF=40 mA) and 0.4W (IF=75 mA) withthe specified pitches. When FR-4 is used, the junction temperature has less interaction at
more than 10 mm at 0.2W and at more than 20 mm at 0.4W. On the other hand, when thealuminum board is used, the junction temperature is less affected even by the pitch at 10mm, enabling LEDs to be mounted by the narrow pitch.
TA=25°C

Part No. NS2x157AR Pitch of LED vs TJ

125

FR-4: 0.4W(If=75mA)(IF=75mA)
FR-4：0.4W
FR-4: 0.2W(If=40mA)(IF=40mA)
FR-4：0.2W
AL：0.4W
AL: 0.4W(If=75mA)(IF=75mA)100

AL：0.2W
AL: 0.2W(If=40mA)(IF=40mA)

75

TJ [°C]Light Emitting Diode

7550

2500102030

Pitch of LED [mm]4050

Figure 5. Junction Temperature at Each Pitch (Part No. NS2x157AR)This document contains tentative information, Nichia may change the contents without notice.
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Application Note
5. Conclusion

Light Emitting DiodeAs shown in the measurement data, the optimal pitch and TJ depend on the output current(W). Therefore, the optimal pitch between LEDs needs to be designed at every output
current (W).
To achieve high quality performance, it is necessary to package LEDs based on theverification results of the optimal pitch and TJ.
Please use this document as reference, since the measurement data varies depending on
LED model and usage conditions/environment at customer sites.

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Application Note

Light Emitting DiodeDisclaimer
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