Application Note

Design Considerations for Direct Mountable Chip

Light Emitting Diode

LEDs (NxSxExxA) for High-Density Applications

Table of contents
1. Overview ............................................................................................................. 2
2. NxSxExxA LED Structure and Concerns about High-Density Mounting ......... 2
3. Considerations for the mounting pitch and configuration between each LED ... 3
4. Recommendations for PCBs used with NxSxExxA ........................................... 4
5. Optical Evaluation for High-Density Modules Mounted with the LEDs ........... 5
6. Thermal Design to Prevent a Reduction in Luminous Flux ............................... 10
7. Evaluations for Examples of High-Density Modules ......................................... 15
8. How to Protect the LEDs from ESD Damage: Protection Devices .................... 17
9. Summary ............................................................................................................. 17

The Nichia part numbers NxSxExxA, NCSxE17A, and NVSxE21A within this document are
merely Nichia’s part numbers for those Nichia products and are not related nor bear resemblance
to any other company’s product that might bear a trademark.

This document contains tentative information, Nichia may change the contents without notice.
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Application Note
1. Overview
As a result of growing trends to reduce the size and increase the light energy of LED-based
luminaries, the demand for compact, high luminous flux and high efficiency LEDs has been
increasing. Since Nichia’s NxSxExxA LEDs are smaller in size than other LEDs that produce thesame amount of light energy, they are more suitable for high-density applications that require highbrightness and high luminous flux. This document provides information on how the opticalcharacteristics of the luminaire are affected when NxSxExxA LEDs are being used in a high-density
application and what issues arise when heat is concentrated on the areas between the LEDs, as wellas Nichia’s evaluation results on these issues.

NxSxExxA LEDs have a compact package and a structure that maximizes the luminous efficacy of
the LED. The LED does not use a primary substrate (e.g. lead frame, etc.) for the electricalconnection, so the face-down LED die is designed to be able to be soldered directly onto a secondary
substrate. For the appearance of NxSxExxA LEDs, see Figure 1, and for the overview of the LED
structure, see Figure 2.

LED ChipElectrodeFigure 1. NxSxExxA Appearance

Figure 2. Internal Structure of NxSxExxA Series

In order to be able to meet variations in demand for the performance and/or design of the chosen
application the NxSxExxA series has two options for the size (i.e. 2.1 x 2.1mm = NVSxE21A and1.7 x 1.7mm = NCSxE17A). For more information about the dimensions, see Figure 3 and Figure
4 below.

1.7

0.27～0.35

0.86

2- 0.86

0.2

1.7Light Emitting Diode2. NxSxExxA LED Structure and Concerns about High-Density
Mounting

Anode
Cathode
2- 0.33

Figure 3. Outline Dimensions of NCSxE17A
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Application Note
2.1

0.27～0.35

1.26

2- 1.262.1

0.2

Cathode Anode2- 0.53

Figure 4. Outline Dimensions of NVSxE21A

Light Emitting DiodeThe following are major issues and concerns when designing a high-density module:
1) How large of a mounting pitch is needed for the LEDs?
2) What material is suitable for the assembly board?
3) How will the mounting pitch affect the luminous flux of the luminaire?
4) How will the mounting pitch affect the directivity/color uniformity of both the LEDs andluminaire?
5) What is the relationship between the mounting pitch and multi-shadow issues?
6) How will the mounting pitch affect the surface that is illuminated by the luminaire?
7) In order to prevent a reduction in luminous flux, what is the best way to manage the thermal
issues for high-density mounting?

3. Considerations for the mounting pitch and configuration between
each LED
3.1 Mounting Pitch between each LED for a High-Density Module
When determining the mounting pitch between each LED for a high-density module, it isimportant to consider the precision of the pick-and-place machine, dimensional tolerances of the
package, and tolerances between the package and electrodes. The necessary mounting pitch
between each LED is shown in Equation 1.
√0.12 (Pick − and − Place Machine) + 0.052 (Package) + 0.052 (Package and Electrode)= 0.122mm(One Side) → 0.244mm ≒ 0.3mm
Equation 1. Required Mounting Pitch between each LED
The answer when solving Equation 1 is approximately 0.3 mm. The potential for the poor alignmentof the packages must also be considered, resulting in the recommended minimum mounting pitch
between each LED as 0.4 mm.
When soldering the LEDs onto a PCB with a small mounting pitch, consider the following andensure that there are no issues: 1) the clearance between the electrodes of the LED is very narrowand it requires higher precision in placing the LEDs and/or manufacturing the PCBs, 2) the LEDs
may not self-align due to the size/shape of the LED electrodes.
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Application Note
For more details about how to mount the LEDs, see Application Note: Assembly Techniques forpart number NCSxE17A/NVSxE21A.
3.2 Configuration Examples for High-Density Mounting for NVSxE21A
Table 1 below illustrates some examples of high-density mounting configurations when soldering
NVSxE21A LEDs with a pitch of 0.4 mm.
Table 1. High-Density Configuration Examples for NVSxE21A LEDs
9.6

9.6

Light Emitting Diode

φ3.0

Number of LEDs
Emission Area
DiameterLuminous Flux

0.4

9.6

2.5

9.7

2.5

9.6

2.5

4.6

2.1

Configuration

2.5

0.4

0.4

0.4

7.1

4.6

2.1

TA=25℃

φ6.5

φ9.8

φ10.7

φ13.6

1

4

8

12

16

φ3.0mm

φ6.5mm

φ9.8mm

φ10.7mm

φ13.6mm(300lm)(1200lm)(2400lm)(3600lm)(4800lm)

As the above examples show, the LEDs have great flexibility in configuration and engineering
design due to the compact size of the package. By changing just the LED configuration, it is possible
to achieve any desired LED emission area diameter; this will allow the LEDs to be used for various
luminaire designs.

4. Recommendations for PCBs used with NxSxExxA
4.1 Recommendations for the PCB Materials
When soldering the LEDs to a PCB with a small mounting pitch, the LEDs may be exposed to heatgenerated by surrounding LEDs and become hot. Due to this heat concentration, the luminous fluxof the LEDs may decrease, the lifetime may become shorter, and the solder resist of the PCB may
discolor; to avoid this, it is important to choose an appropriate PCB material for the chosen
application.
If a PCB with low thermal dissipation (e.g. CEM-x and FR-x PCBs) is used for NxSxExxA LEDs,
the concentrated heat may not be dissipated sufficiently; Nichia recommends using PCBs with highthermal dissipation (e.g. MCPCBs).
4.2 Recommendations for the Land Patterns
There are two types of land patterns for a PCB solder mask, Non-Solder Mask Defined (NSMD)
and Solder Mask Defined (SMD). Since NxSxExxA LEDs require precision for both picking andplacing, NSMD pads are recommended. For more details, see Application Note: AssemblyTechniques for part number NCSxE17A/NVSxE21A.

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Application Note
5. Optical Evaluation for High-Density Modules Mounted with theLEDs
To verify the optical characteristics of a module with a high density of the LEDs (i.e. lightinterference, directivity/chromaticity, multi-shadow, and illuminated surface), Nichia performed anevaluation of NCSxE17A (5000K/R8000). For this evaluation, 12 LEDs were mounted on a 25 mm
x 25 mm PCB for mounting pitches ranging from 0.2mm up to 1.9mm.
5.1 High-Density Modules that were used for the Evaluation
Table 2 shows the LED configurations and Table 3 shows the board specifications for the PCBs thatwere used in the evaluation.

Light Emitting Diode

Table 2. LED Configurations
LED Clearance
Emission Area
Diameter

0.2 mm

0.4 mm

0.9 mm

1.4 mm

1.9 mm

φ8.2 mm

φ8.9 mm

φ10.4 mm

φ12.0 mm

φ13.6 mm

Configuration

Table 3. Specifications of the PCBs used
Outline dimensions (mm)

25×25
LED
Copper
Solder resist
Insulating layer
Base metal

Structure

Land Pattern

Thickness

(μm)

35

(Copper)

Thermal conductivity(W/mK)

400

Solder Resist

-

-

White

Insulating

Thickness

(μm)

120

layer

Thermal conductivity(W/mK)

Material-

Thickness

(μm)

1.0

2.0

1.0

Thermal conductivity(W/mK)

218

218

400

Base metal

2.1

11.1
Al6063

2.7
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Application Note
5.2 Effect of the Mounting Pitch on the Luminous Flux

Figure 5. How the light scatters whenthe mounting pitch is sufficient

Figure 6. How the light is blocked/absorbed
when the mounting pitch is insufficient

As shown in Figure 5, if the mounting pitch is sufficient, the light from each LED may be lessaffected by the adjacent LEDs. On the other hand, as shown in Figure 6, if the mounting pitch is
insufficient, some of the light may be blocked/absorbed and it may cause the overall luminous fluxof the module to decrease.
As a result of the above information, there could be a concern when the LEDs are used in a highdensity module; Nichia performed an evaluation by using different mounting pitches between 0.2
to 1.9 mm to determine if this concern occurs with these pitches. Table 4 and Figure 7 below show
the results of this evaluation. As shown in this table and figure, these mounting pitches do not affectthe luminous flux at the module level.
Table 4. Relative Luminous Flux vs. Mounting Pitch
LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

Measurement condition

AL (t=1.0mm)

0.99

1.00

1.00

1.00

1.00

: IFP=350mA, TA=25℃

AL (t=2.0mm)

0.99

1.00

1.00

0.99

1.00

Cu (t=1.0mm)

0.99

1.00

1.00

1.00

1.00

1.10

Relative Luminous Flux (a.u)

Light Emitting DiodeIf LEDs are mounted to a module with a narrow pitch, the light from these LEDs may be affectedby the adjacent LEDs (e.g. blocked, absorbed, etc.) and it may cause the luminous flux to decreaseat the module level. Figure 5 and Figure 6 illustrate how the difference in mounting pitch can affect
how the light scatters, or are blocked/absorbed.

1.05

1.00

0.95

0.90
AL (t=1.0mm)
0.85

AL (t=2.0mm)
Cu (t=1.0mm)

0.80

0.0

0.5

1.0

1.5

2.0

LED Clearanc (mm)Figure 7. Relative Luminous Flux vs. Mounting Pitch
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Application Note
5.3 Directivity Comparison for Directivity and Color Uniformity
Nichia performed an evaluation to compare the directivity and color
uniformity between discrete LEDs and high-density modules. Figure 8
and Figure 9 below show the comparison results.

0° Direction

90° Direction

As shown in the below figures, there is not a noticeable difference
between the discrete LEDs and the high-density modules for either
the directivity or color uniformity.
Directivity (90°direction)
Measurement Condition: IFP=700mA, TA=25℃

Directivity (0°direction)
Measurement Condition: IFP=700mA, TA=25℃
1.2

1.2
0.2mm
0.4mm
0.9mm
1.4mm
1.9mm
Discrete

Relative Intensity (a.u.)

Relative Intensity (a.u.)

0.8

1.0

0.6

0.4

0.8

0.6

0.4

0.2

0.2

0.0

0.0
-90

-60

-30

0

30

60

-90

90

-60

-30

0

30

60

90

Radiant Angle (°)

Radiant Angle (°)

Figure 8. Directivity Comparison
90°Direction

0°Direction
Color Uniformity (x coordinate)
Measurement Condition : IFP=700mA, TA=25℃
0.10

0.10

0.2mm
0.4mm
0.9mm
1.4mm
1.9mm
Discrete

0.08

0.06

⊿x

0.06

⊿x

Color Uniformity (x coordinate)
Measurement Condition : IFP=700mA, TA=25℃
0.2mm
0.4mm
0.9mm
1.4mm
1.9mm
Discrete

0.08

0.04

0.04

0.02

0.02

0.00

0.00

-0.02

-0.02
-90

-60

-30

0

30

60

90

-90

-60

Color Uniformity (y coordinate)
Measurement Condition : IFP=700mA, TA=25℃
0.10

30

0.10

60

90

0.2mm
0.4mm
0.9mm
1.4mm
1.9mm
Discrete

0.08

0.06

⊿y

0.06

0

Color Uniformity (y coordinate)
Measurement Condition : IFP=700mA, TA=25℃

0.2mm
0.4mm
0.9mm
1.4mm
1.9mm
Discrete

0.08

-30

Radiant Angle （°）

Radiant Angle （°）⊿yLight Emitting Diode

1.0

0.2mm
0.4mm
0.9mm
1.4mm
1.9mm
Discrete

0.04

0.04

0.02

0.02

0.00

0.00
-0.02

-0.02
-90

-60

-30

0

30

60

90

-90

-60

Radiant Angle （°）

-30

0

30

60

90

Radiant Angle （°）

Figure 9. Color Uniformity Comparison
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Application Note
5.4 Design Considerations to Improve the Multi-Shadow EffectNichia performed an evaluation to discover what the multi-shadow would look like when both the
LED light source and screen are fixed and an object is moved. In this evaluation, high-density
modules mounted with the LEDs with different mounting pitches were used as the light source; thelight source and screen were fixed in one position and an object was moved to change the distance
between the light source/screen and this object. Figure 10 below shows the evaluation settings andTable 5 shows the results.

Light Emitting DiodeAs shown in Table 5, Nichia confirmed that the narrower the mounting pitch was, the more
improved the multi-shadow effect became; the farther the object is, the more distinct the shadow
became.

Light
SourceDistance to
ObjectObjectScreenDistance to Screen (0.5m)

Figure 10. Multi-Shadow Evaluation Method
Table 5. Multi-Shadow Evaluation Results
LED Clearance (mm)

0.2

0.4

IF=50mA, Distance to Screen=0.5m
0.9

1.4

1.9

0.1

0.2
Distance to Object
(m)
0.3

0.4

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Application Note
5.5 Confirmation of the Illuminated Surfaces
Nichia confirmed the differences among the illuminated surfaces in regards to mounting pitch
between each LED. The method used for this confirmation is the same as the multi-shadow
evaluation method shown in Figure 9 except the object is excluded. The results of the illuminatedsurface confirmations are shown in Table 6. If the LEDs are mounted with a small mounting pitch,
regardless of whether a diffuser lens and/or reflector are used, there is no difference in either theilluminated surface or how the light appears when viewed from the side.
Table 6. Results obtained by illuminating the screen and viewing the light source from the side
IF=50mA, Distance to Screen=0.5m

Light Emitting Diode

LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

Configuration(Luminaire)
Installed witha lens andScreenreflector

surface(Luminaire)

illuminatedInstalled withby the lighta reflector

source fromonly

the front
LED Only

Modules when viewed fromthe sideDifference when viewed by

No variation in color. No difference in the illuminated surface due to the difference inthe human eye

mounting pitch between LEDs.

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Application Note
6. Thermal Design to Prevent a Reduction in Luminous Flux
If the LEDs are used in a high density module, heat from each LED may concentrate in certain
areas of the module and it may cause the luminous flux to decrease. This section discusses the effectof the heat concentration on the luminous flux and how to reduce the heat concentration to avoid apossible decrease in luminous flux.

Light Emitting Diode

In order to prevent heat that is generated by LEDs from concentrating on a module, using the LEDs
under appropriate conditions/environments are important. To determine those conditions/environments, Nichia conducted an evaluation by using different mounting pitches and PCBs withdifferent thermal resistance values. In this evaluation, Nichia used:- 12W module operated at IF=350mA (1W/LED) with a thermal resistance of 2.0°C/W- 24W module operated at IF=700mA (1W/LED) with a thermal resistance of 0.5°C/W- Grease with a thermal conductivity of 0.84W/m·K

For the dimensions and appearance of the above heat sinks, see Figure 11 and Figure 12.

Figure 11. Heat sink with a Thermal
Resistance of 2.0°C/W(100 x 143 x 30 mm)

Figure 12. Heat sink with a
Thermal Resistance of 0.5°C/W(150 x 294 x 90 mm)

6.1 Evaluation of 12W Modules:
the relationship between the mounting pitch and the reduction in luminous flux
Nichia measured temperatures of 12W modules after operating them for 1 hour. Tables 7 to 9 and
Figure 13 show the measurement results.
Table 7. Heat Dissipation Evaluation Results (Aluminum board, thickness=1.0mm)
0.2

0.4

0.9

1.4

1.9

LED Surface Temperature TT (℃)

65.5

63.3

61.2

57.4

51.6

PCB Temperature TB (℃)

37.3

36.6

35.5

35.9

35.1

Thermal Resistance RθTB (℃/W)

27

25

24

20

16

LED Clearance (mm)Heat Distribution

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Application Note
Table 8. Heat Dissipation Evaluation Results (Aluminum board, thickness=2.0mm)
LED Clearance (mm)

0.2

0.

0.9

1.4

1.9

LED Surface Temperature TT (℃)

53.6

53.6

54.3

50.1

50.1

PCB Temperature TB (℃)

34.1

34.4

34.8

34.8

34.3

Thermal Resistance RθTB (℃/W)

19

18

19

15

15

Heat Distribution

Table 9. Heat Dissipation Evaluation Results (Copper board, thickness=1.0mm)
0.2

0.4

0.9

1.4

1.9

LED Surface Temperature TT (℃)

66.8

59.4

56.1

51.7

49.6

PCB Temperature TB (℃)

32.8

33.4

33.2

33.7

35.1

Thermal Resistance RθTB (℃/W)

32

25

22

17

14

Heat Distribution

105
AL (t=1.0mm)

LED Surface Temperature(℃)

Light Emitting Diode

LED Clearance (mm)95

AL (t=2.0mm)

85

Cu (t=1.0mm)

75
65
55
45
35
25
0.0

0.5

1.0

1.5

2.0

LED Clearance (mm)Figure 13. Junction Temperature vs. Mounting Pitch by type of PCB
If the mounting pitch is not appropriate, it can cause heat from the LEDs to concentrate in certain
areas. This can be avoided by using a heat sink with a good thermal resistance. To verify the
relationship between the mounting pitch, material of the PCB, and the luminous flux reduction,
Nichia performed an evaluation. Tables 10 to 12 and Figure 14 below show the evaluation results.
Table 10. Mounting Pitch vs. Reduction in Luminous Flux (Aluminum board, Thickness=1.0mm)
LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

Luminous

Lighting time 1.5sec

1702

1717

1719

1718

1722

Flux (lm)Lighting time 1hr

1589

1610

1621

1624

1629

Loss (%)

9.5

6.6

6.2

5.7

5.5

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Application Note
Table 11. Mounting Pitch vs. Reduction in Luminous Flux (Aluminum board, Thickness=2.0mm)
LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

Luminous

Lighting time 1.5sec

1722

1737

1733

1721

1731

Flux (lm)Lighting time 1hr

1633

1641

1642

1636

1646

Loss (%)

9.5

9.5

5.2

5.5

5.3

Table 12. Mounting Pitch vs. Reduction in Luminous Flux (Copper board, Thickness=1.0mm)
0.2

0.4

0.9

1.4

1.9

Luminous

Lighting time 1.5sec

1710

1718

1729

1722

1722

Flux (lm)Lighting time 1hr

1594

1618

1631

1632

1631

Loss (%)

9.5

6.8

5.8

5.7

5.2

1.10

Relative Luminous Flux [a.u.]Light Emitting Diode

LED Clearance (mm)

1.05
1.00
0.95
0.90
AL (t=1.0mm)
AL (t=2.0mm)

0.85

Cu (t=1.0mm)
0.80

0.0

0.5

1.0

1.5

2.0

LED Clearance [mm]Figure 14. Relative Luminous Flux vs. Mounting Pitch by type of PCB
If the mounting pitch is not appropriate, it can cause heat from the LEDs to concentrate in certain
areas and the luminous flux to decrease. This can be avoided by using PCBs with good thermal
dissipation.
6.2 Evaluation of 24W Modules:
the relationship between the mounting pitch and the reduction in luminous flux
Nichia measured temperatures of 24W modules after operating them for 1 hour. Tables 13 to 15 andFigure 15 show the measurement results.
Table 13. Heat Dissipation Evaluation Results (Aluminum board, Thickness=1.0mm)
0.2

0.4

0.9

1.4

1.9

LED Surface Temperature TT (℃)

100.5

93.1

91.8

81.7

80.7

PCB Temperature TB (℃)

37.3

37.2

37.0

37.3

37.3

Thermal Resistance RθTB (℃/W)

30

27

26

21

21

LED Clearance (mm)Heat Distribution

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Application Note
Table 14. Heat Dissipation Evaluation Results (Aluminum board, Thickness=2.0mm)
LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

LED Surface Temperature TT (℃)

74.4

66.7

68.5

61.9

56.3

PCB Temperature TB (℃)

25.5

25.4

25.7

25.9

25.9

Thermal Resistance RθTB (℃/W)

23

20

20

17

14

Heat Distribution

Table 15. Heat Dissipation Evaluation Results (Copper board, Thickness=1.0mm)
0.2

0.4

0.9

1.4

1.9

LED Surface Temperature TT (℃)

96.4

85.5

77.3

74.4

66.9

PCB Temperature TB (℃)

30.5

30.5

29.9

30.7

30.3

Thermal Resistance RθTB (℃/W)

31

26

23

21

17

Heat Distribution145
AL (t=1.0mm)
AL (t=2.0mm)

125

LED Surface Temperature(℃)

Light Emitting Diode

LED Clearance (mm)Cu (t=1.0mm)
105
85
65
45
25

0.0

0.5

1.0

1.5

2.0

LED Clearance (mm)Figure 15. Junction Temperature vs. Mounting Pitch by type of PCB
If a high current is applied to high-density modules mounted with the LEDs, a rapid increase injunction temperature may be observed. To avoid the increase in junction temperature, it is importantto select both a PCB with good heat dissipation and appropriate mounting pitch. Nichia evaluated
PCBs of different materials (e.g. aluminum and copper) and thicknesses (e.g. 1.0mm and 2.0mm)
to determine how these PCBs affect the reduction in luminous flux. Tables 16 to 18 and Figure 16
show the results of this evaluation.

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Application Note
Table 16. Mounting Pitch vs. Reduction in Luminous Flux (Aluminum board, Thickness=1.0mm)
LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

Luminous

Lighting time 1.5sec

3054

3047

3070

3072

3081

Flux (lm)Lighting time 1hr

2763

2810

2855

2872

2888

Loss (%)

9.5

7.8

7.0

6.5

6.3

Table 17. Mounting Pitch vs. Reduction in Luminous Flux (Aluminum board, Thickness=2.0mm)
0.2

0.4

0.9

1.4

1.9

Luminous

Lighting time 1.5sec

3089

3104

3102

3070

3093

Flux (lm)Lighting time 1hr

2902

2927

2926

2917

2931

Loss (%)

9.5

6.0

5.7

5.7

5.0

Table 18. Mounting Pitch vs. Reduction in Luminous Flux (Copper board, Thickness=1.0mm)
LED Clearance (mm)

0.2

0.4

0.9

1.4

1.9

Luminous

Lighting time 1.5sec

3070

3065

3095

3084

3086

Flux (lm)Lighting time 1hr

2773

2849

2889

2895

2899

Loss (%)

9.5

9.7

7.0

6.6

6.1

1.10

Relative Luminous Flux (a.u.)Light Emitting Diode

LED Clearance (mm)

1.05

1.00
0.95
0.90
AL (t=1.0mm)

AL (t=2.0mm)

0.85

Cu (t=1.0mm)
0.80

0.0

0.5

1.0

1.5

2.0

LED Clearance (mm)Figure 16. Relative Luminous Flux vs. Mounting Pitch by type of PCB
If a high current is applied to the LEDs that are mounted with a narrow pitch, even if operated underconditions/environments where the heat is sufficiently dissipated, it may cause the luminous flux
to decrease significantly. In order to maintain a sufficient luminous flux, it is important to selectboth an appropriate PCB and mounting pitch.
* The junction temperatures or TJ in this section were determined by measuring the package
surfaces, instead of the dice, with a thermal imaging camera. If a thermal imaging camera is usedin temperature measurement for the chosen application, ensure that a thermocouple is used in themeasurement along with the thermal imaging camera to ensure that these temperatures are
consistent.

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Application Note
7. Evaluations for Examples of High-Density Modules
This section provides some examples of high-density modules to illustrate the issues discussed in
the previous sections and includes the evaluation results of these modules. The modules were
designed to achieve 700lm with a diameter of φ20mm and is operated at 500W at TJ=85°C. For thedetails of these modules, see Table 19 below.
Table 19. Specifications for the Example Test Modules
Package dimension: 1.7mm, Color temperature: 4000K, Ra>70
18.5
0.4

18.5

2.1

2.1

LED Configuration

16.4

Light Emitting Diode

0.4

18.5

φ20

φ20

Mounting Pitch

0.4 mmNumber of LEDs

60pcs

63pcs

Target Luminous Flux 7000lm

Conditions(operated at 50W, TJ=85°C)

Luminous Flux

(lm)

7003

7020

Forward Current

(mA)

295

280

Watts

(W)

50.3

50.0

Luminous Efficacy(lm/W)

139

141

Figure 17 below shows the appearance and specifications of the heat sink that was used for themodules to dissipate heat.

TA = 25°C
Heat sink: 0.33°C/W
Grease: 9.0W/m·K
PCB
Material: Copper (Cu)
PCB thickness: 1.5 mm
Insulating Layer thickness: 120μ m (3W/m·K)
Land Pattern (Copper) thickness: 35μm

Figure 17. Heat sink used for the Evaluation

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Application Note
Nichia measured the characteristics of the test modules as they were mounted on the heat sink. For
the measurement results, see Table 20 below.
Table 20. Measurement Results of the Test Modules
Package dimension: 1.7mm, Color temperature: 4000K, Ra>70

Light Emitting Diode

LED Configuration

Mounting Pitch

0.4 mmNumber of LEDs

60pcs

63pcs

Conditions

IF=295mA

IF=280mA(Forward Current (IF),Calculated

Measured Value

Emission Duration)

Value

1.5sec1hr

Value

1.5sec1hr

Luminous Flux (lm)

7003

7723

7502

7020

7759

7560

Watts (W)

50.3

51.6

50.2

50.0

51.2

49.8

Luminous Efficacy (lm/W)

139

150

149

141

152

152

Junction Temperature TJ (℃)

85

-

-

85

-

-

Calculated

Measured Value

Table 21 below shows thermal images that illustrate how the heat is distributed over the surfaces ofthe modules. Based on these images, when a current that flows through a LED is smaller, heatbecomes less concentrated.
Table 21. Distribution of heat on the test module surfaces
Package dimension: 1.7mm, Color temperature: 4000K, Ra>70
Mounting Pitch

0.4 mmNumber of LEDs

60pcs

63pcs

Conditions

IF=295mA

IF=280mA

PCB Temperature TB (℃)

58.6

55.2

LED Surface Temperature TT (℃)

68.8

65.2

Thermal Resistance RθTB (℃/W)

12.2

12.6

Heat Distribution

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Application Note
8. How to Protect the LEDs from ESD Damage: Protection Devices
Since NxSxExxA LEDs do not have internal protection devices, to protect the LEDs from ESD
damage it is recommended to use the LEDs with a protection device on a module. Nichia has
performed two kinds of electrostatic discharge (ESD) tests (i.e. HBM and MM) on both modules
mounted with the LEDs and a protection device and modules mounted with the LEDs without aprotection device and verified that if a protection device is not used in the module, even a low
voltage may be able to damage the LEDs and/or cause them not to illuminate. Table 22 and Table
23 below show the test results.

Light Emitting Diode*These results do not guarantee the reliability or performance of the LEDs. Ensure that an
appropriate protection device is selected and/or necessary tests are performed for the chosen
application.
Table 22. ESD Tests (HBM) HBM, 1.5kΩ, 100pF, 1 pulse, alternately positive or negative
Protection device (i.e. ZD)
With ZD
Without ZD

Direction of IF

Maximum voltage (kV)Results

Positive

10

Pass

Negative

10

Pass

Positive

10

Pass

Negative

1.7

Fail

Table 23. ESD Tests (MM)Protection device (i.e. ZD)

MM, 0Ω, 200pF, 1 pulse, alternately positive or negative

Direction of IF
Positive

With ZD
Negative
Positive
Without ZD
Negative

Maximum voltage (kV)Results

4

Pass

4

Pass

4

Pass

4

Pass

1.1

Fail

1.4

Fail

1.2

Fail

1.5

Fail

9. Summary
As the previous sections have discussed, Nichia has confirmed that for the NxSxExxA LEDs
1) the mounting pitch does not have an effect on the optical characteristics of the modules,
2) if the mounting pitch is smaller, more heat can concentrate in certain areas on the modulesurface; it can cause a further reduction in luminous flux at the module level,3) if the LEDs are used in conditions/environments where heat is sufficiently dissipated, as
verified by the examples of high density modules in Section 7, the heat concentration in certain
areas of the module can be reduced and the reduction in luminous flux can be improved at themodule level.
When designing a high-density module that uses NxSxExxA LEDs, give sufficient consideration to
the issues discussed in this application note and perform further evaluation to determine thespecifications/design of the chosen application (e.g. mounting pitch, thermal design of the module,etc.).
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Application Note

Light Emitting Diode

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.
 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
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 The content of this application note may be changed without any prior or subsequent notice.
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