Application Note

Light Emitting Diode

Thermal Design Considerations for
the Nichia NFMW48xAR Series LEDs

Table of contents
1. Overview ....................................................................... 2
2. Structure and key features of the NFMW48xAR Series
LEDs ............................................................................. 2
3. Recommended soldering pad pattern and metal solder
stencil aperture .............................................................. 44. Materials for PCBs ........................................................ 5
5. Thermal evaluation of the light source modules ........... 8
6. Summary ..................................................................... 12

The Nichia part numbers NFMW481AR, NFMW484AR, NFMW486AR, NFMW488AR, andNFMW48xAR 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
Thermal design is very important for LEDs since it determines the optical and electricalcharacteristics (e.g. luminous flux, forward voltage, etc.) of the LEDs and it even affects the lifetimeof the LEDs. When performing a thermal evaluation, customers must check how high the junction
temperature of the LED will be when the LED is operated in the conditions/environments in which
the LED will actually be used.

Light Emitting Diode

Nichia's NFMW48xAR series LEDs have a high luminous flux density with a smaller light emitting
surface (LES) and a low thermal resistance. This series is also available in four different light output
options while keeping the same package size, this allows the series to be used for various
applications. The NFMW48xAR series can produce a higher luminous flux than typical LEDs thatare operated at 1-3W; the thermal design needs to be appropriate for the chosen application.
This application note provides cautions/suggestions for the thermal design of the chosen application
using the NFMW48xAR series LEDs showing the evaluation results to ensure that the required
luminous flux for the chosen application is obtained.

2. Structure and key features of the NFMW48xAR Series LEDs
The NFMW48xAR Series LEDs have an outline dimension of 6.5mm×5.8mm×0.8mm withmultiple chips mounted on the lead frame. Table 1 shows the detailed information of each LED.
Table 1. The NFMW48xAR Series LED
Characteristics

1
2

Unit

NFMW481AR NFMW484AR NFMW486AR NFMW488AR

Number of Chips
Forward Current1

mA

7
200

10
200

12
200

14
200

Forward Voltage
Power Consumption

V
W

22.9
4.58

32.8
6.56

39.3
7.86

45.9
9.18

Luminous Flux2
Maximum Junction
Temperature
Thermal Resistance (max)

lm

(640)

(900)

(1060)(1240)

℃

135

135

135

135

℃/W

3.8

3.4

3.1

2.8

The absolute maximum rating forward current of the LEDs is 250mA.
The luminous flux values are typical values of the LEDs at a color temperature of 5000K andcolor rendering index of R8000. For further information, refer to the specifications.

This document contains tentative information, Nichia may change the contents without notice.
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Application Note
* 本製品はRoHS指令に適合しております。
This product complies with RoHS Directive.
* 括弧で囲まれた寸法は参考値です。
* 本製品はRoHS指令に適合しております。
* 本製品はRoHS指令に適合しております。
The dimension(s) in parentheses are for reference purposes.
This
product
complies
with
RoHS
Directive.
This
product
complies
with
RoHS
Directive.
* 括弧で囲まれた寸法は参考値です。
* 括弧で囲まれた寸法は参考値です。
dimension(s)in parentheses
reference
purposes.
TheThedimension(s)in parentheses
areareforforreference
purposes.

管理番号 No.

NFMW481AR
STS-DA7-1055(単位
Unit:±0.2mm
Unit: mm, 公差 Tolerance:
NFMW481AR
NFMW481AR
The NFMW48xAR Series LEDs are designed to have a large cathode electrode (単位in orderto dissipate
STS-DA7-1055
管理番号
管理番号
No.No.STS-DA7-10559
the heat efficiently and have a low thermal resistance. Figure 1 shows the outline dimensions of the
(単位
Unit:
mm
(単位
Unit:
mm)
(単位
Unit:
mm,
公差
Tolerance:
±0.2
(単位
Unit:
mm,
公差
Tolerance:
±0.2)
LEDs.
光学的中心位置
Location of the optical center(Unit: mm)

CathodeMark
Cathode
Mark

5.8

(5.6)

0.25
(0.8)

(4.8)
(5.6)
5.8
(4.8)
(4.8)
6.5
(5.6)
(5.6)

0.25
0.25
(0.8)
(0.8)

5.85.8
6.56.5

質量
電極材質
電極材質
WeightElectrodes
Materials
Electrodes
Materials

質量
質量
WeightWeight

Anode
Anode

2.03
2.03

耐熱性ポリマーHeat-Resistant Polymer
内容
Description
内容
Description
シリコーン樹脂
耐熱性ポリマー
耐熱性ポリマー（拡散剤+蛍光体入り）
Heat-Resistant
PolymerHeat-Resistant
Silicone Polymer
Resin(with シリコーン樹脂
diffuserand phosphor)
シリコーン樹脂

4.77

2.65

CathodeCathodeパッケージ材質
Package Materials
項目
Item
項目
Item

封止樹脂材質
封止樹脂材質
電極材質
Encapsulating
Resin
Encapsulating
Resin
Electrodes
Materials
Materials
Materials

Anode

2.03

内容 Description

封止樹脂材質パッケージ材質
パッケージ材質
Encapsulating
Resin
Package
Materials
Package
Materials
Materials

3.7
Cathode

項目 Item

3.7
3.7
4.77
4.77

Light Emitting Diode

Cathode Mark

(5.6)
5.8
5.8

3.7

3.7
3.7
(4.8)
(4.8)
(5.6)

(4.8)

光学的中心位置
光学的中心位置
Locationof theopticalcenterLocationof theopticalcenter（拡散剤+蛍光体入り）（拡散剤+蛍光体入り）
銅合金+銀メッキ
Silicone
ResinAlloy
SiliconeResin
Ag-plated
Copper(with
diffuserphosphor)(withdiffuserandandphosphor)
0.077g(TYP)
銅合金+銀メッキ
銅合金+銀メッキ
Ag-plated
CopperAlloy
Ag-plated
CopperAlloy

0.077g(TYP)
0.077g(TYP)

2.65
2.65

Figure 1. Outline dimensions of the NFMW48xAR Series LEDs (excerpted from the specification)
K

A

K K

A A
保護素子
Protection Device

保護素子
保護素子
Protection
DeviceProtection
DeviceThis document contains tentative information, Nichia may change the contents without notice.
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Application Note
3. Recommended soldering pad pattern and metal solder stencil
aperture
Figure 2 shows a recommended soldering pad pattern and metal solder stencil aperture for the
NFMW48xAR Series LEDs.

Light Emitting Diode

0.95
0.3

1.55
2.75

2.03
2.65

(Unit: mm)

1.45
0.8

2.3
3.35
3.6
4.15

2.78
4.1
4.78

Anode

3.74

Cathode

7.1
2.06

5.9
6.7
7.15

⋯ Outlines of the LED package and the electrodes■ Recommended soldering pad pattern■ Recommended metal solder stencil aperture▩ Prohibited area for the copper layer

Figure 2. Recommended soldering pad pattern and metal solder stencil aperture for the
NFMW48xAR Series LEDs
Precautions:
The electrodes of the NFMW48xAR series LEDs have a complicated shape; depending on thewiring pattern, the anode and cathode may contact each other resulting in a short circuit. There mustnot be any copper layer in the prohibited area shown in Figure 2.
To improve the heat dissipation performance and transfer the heat more efficiently to the PCB,
Solder Mask Defined (SMD) is recommended for the soldering pad pattern. If SMD is used, it must
be verified that the solder resist can be applied on the PCB precisely as designed.
Figure 3 shows an example of the wiring patten.

Do not have any copper layer
in the prohibited area.

Figure 3. An example of the wiring patternThis document contains tentative information, Nichia may change the contents without notice.
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Application Note
4. Materials for PCBs
4.1 Materials for PCBs

Light Emitting DiodeIn general, glass epoxy substrates (hereinafter referred to as “FR4 substrate”), glass composite
substrates with high heat dissipation (hereinafter referred to as “CEM3 substrate”), and aluminum
substrates are widely used as PCBs to attach the LEDs. The material of the PCB (i.e. glass epoxy,glass composite, aluminum, etc.) should be selected based on the specifications of the LED being
used, the forward current that will be applied to the LED, and the required heat dissipation
performance for the chosen luminaire.
If Nichia’s NFMW48xAR Series LEDs are intended to be used to emit a high luminous flux, analuminum substrate may often be selected for better heat dissipation. However, if they are used toemit a low luminous flux, an FR4 substrate or a CEM3 substrate with a high thermal conductivity
can be used.
To determine how the heat dissipation performance varies depending on the material of the PCB,
Nichia performed evaluations using the NFMW488AR LEDs; the NFMW488AR LEDs emit thehighest luminous flux among the other LEDs in the series. Refer to Section 4.2 for the evaluation
results.
4.2 Heat dissipation performance of each PCB material
4.2.1 The test PCBs
Nichia performed a thermal evaluation with different PCBs (i.e. different materials and different
outline dimensions) to determine how the heat dissipation of the NFMW488AR LEDs varies. Table
2 shows the outline dimensions of the test PCBs and Table 3 shows the materials of the test PCBs.
Table 2. Outline dimensions of the test PCBs
Item

A

B

C

D

E

12mm×15mm

20mm×20mm

25mm×25mm

30mm×30mm

35mm×35mm

180mm2400mm2625mm2900mm21225mm2

Picture of the
Appearance

Outline Dimensionsof the PCB
Area of the PCB

Table 3. Materials of the test PCBs
Item
Thermal Conductivity
Thickness of the Copper Layer
Thickness of the PCB
3
4

Unit
W/m∙K
μm
mm

FR4 Substrate3
0.4
35
1.0

CEM3 Substrate3
1.5
35
1.0

Aluminum Substrate
2.14
35
1.1

For the FR4 and CEM3 substrates, non-plated through hole, double-sided PCBs were used.
The thermal conductivity for the aluminum substrates was the thermal conductivity of theinsulating layer. The thickness of the insulating layer was 120μm.
This document contains tentative information, Nichia may change the contents without notice.
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Application Note
In this thermal evaluation, Nichia attached each test PCB to a heatsink and measured thetemperature of the solder joint after the saturation temperature had been reached. The LED andother test materials used are shown below. See Figure 4 for a picture of a test PCB attached to aheatsink.
・ LED:
the NFMW488A LED with the color
temperature of 2700K and the color renderingindex of R8000. Forward current: IF=200mA・ Thermal grease:
SCH-30 manufactured by Sunhayato Corp.
Thermal conductivity: 0.84W/m∙K・ Heatsink:
Figure 4. Test PCB attached to a heatsink
100mm (L)×100mm (W)×10mm (H).
Thermal resistance: 3.0℃/W. Weight: 0.2kg
4.2.3 Results of the thermal evaluation
The evaluation results show that the junction temperature (TJ) of the LED significantly varied
depending on the PCB material. When the forward current (IF) was 200mA, the TJ of the LED
attached to the aluminum substrate was the lowest. For the CEM3 and FR4 substrates, the TJ
exceeded the absolute maximum rating TJ.
Regarding the relationship between the TJ and the size of the PCBs, it was confirmed that the sizeof the PCBs did not affect the heat dissipation much for the aluminum substrate. For the FR4
substrate, the heat dissipation performance was greatly reduced when the size of the PCBs was ≺400mm2. See Figure 5 for the detailed results.
275
Junction Temperature (℃)

Light Emitting Diode4.2.2 Evaluation conditions

Junction temperature: 135℃
225
175
125

FR4:IF=200mA
FR4:
IF=200mA75

CEM3:IF=200mA
CEM3:IF=200mA
Aluminium:IF=200mA
Aluminum:
IF=200mA

25
0

200

400

600 800 1000 1200 1400
PCB size (mm2)Figure 5. Evaluation results per PCB material
To calculate the TJ, the following equation was used:
TJ = TS + RθJS∙W
TJ=Junction Temperature (℃), TS=Temperature of Solder Joint (℃)
RθJS=Thermal Resistance from Chip to Solder Joint (℃/W)
W=Input Power (W)This document contains tentative information, Nichia may change the contents without notice.
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Application Note
4.3 Heat dissipation of the FR4 and CEM3 substrates
This thermal evaluation was performed using the FR4 and CEM3 substrates with different forward
currents (IF) applied to the LED since the absolute maximum rating TJ was exceeded with the FR4
and CEM3 substrates in the evaluation described in section 4.2. Except for the IF, all the conditionsof this evaluation were the same as in the evaluation in section 4.2. See Figures 6 and 7 for the
results.
150

FR4基板
6.1W
FR4: IIf=150mA
F=150mA, 6.1W

Junction temperature: 135℃

FR4基板
5.1W 5.1W
FR4: IIf=125mA
F=125mA,
FR4基板
4.0W 4.0W
FR4: IIf=100mA
F=100mA,

Junction Temperature (℃)

FR4基板
3.0W3.0W
FR4: IIf=75mA
F=75mA,

FR4基板
1.9W1.9W
FR4: IIf=50mA
F=50mA,
FR4基板
0.9W0.9W
FR4: IIf=25mA
F=25mA,

100

75

50

25
0

200

400

600
800
PCB size (mm2)

1000

1200

1400

Figure 6. Results of the evaluation using the FR4 substrate150

CEM3基板
8.4W 8.4W
CEM3: IIf=200mA
F=200mA,

Junction temperature: 135℃

CEM3基板
6.2W 6.2W
CEM3: IIf=150mA
F=150mA,

CEM3基板
4.0W 4.0W
CEM3: IIf=100mA
F=100mA,

125

Junction Temperature (℃)

Light Emitting Diode

125

100

75

50

25
0

200

400

600
800
PCB size (mm2)

1000

1200

1400

Figure 7. Results of the evaluation using the CEM3 substrate
The evaluation results show that the TJ was below the absolute maximum rating (i.e. 135°C) whenthe IF was ≤100mA for the FR4 substrate and when the IF was ≤150mA for the CEM3 substrate.
Although the TJ will vary depending on the heat dissipation performance of the chosen luminaire,the evaluation results indicate that the FR4 and CEM3 substrate can be used when the LED is
operated at a low enough IF.
This document contains tentative information, Nichia may change the contents without notice.
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Application Note
5. Thermal evaluation of the light source modules
5.1 Test light source modules and evaluation conditions
In section 4, Nichia describes the thermal evaluations performed with the PCBs that have one LED
attached on each of them; in this section, Nichia describes the thermal evaluations performed with
PCBs that have multiple LEDs attached on each of them (i.e. the light source module). Table 4
provides the detailed information of the light source modules used for the evaluation.
Table 4. Test light source modules

Light Emitting Diode

Item

Details

Test Light Source
Module

20mmP
25mmP

Outline Dimensionsof the Substrate
LEDs Used and the
Number of AttachedLEDs
LED Pitch5
Circuit Configuration
Thermal Grease
Heatsink

119mm (L)×136mm (W)The NFMW488AR LEDs with the color temperature of 5000K and the color
rendering index of R70, 20 LEDs
20mm (H), 25mm (W)
10 arrays connected in parallel, each with 2 LEDs connected in series
SCH-301 manufactured by Sunhayato Corp. Thermal conductivity:
0.84W/m∙K
250mm (L)×200mm (W)×40mm (H). Thermal resistance: 0.45℃/W.
Weight: 2.4kg. Material: Aluminum

5

The LEDs were aligned in a manner where each LED had an area larger than 400mm2 to dissipate
the heat, taking the evaluation result described in section 4 (i.e. the relationship between the size ofthe substrate and heat dissipation performance) into consideration.
This document contains tentative information, Nichia may change the contents without notice.
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Application Note
Table 5 provides the detailed information of the substrates used for the evaluation.
Table 5. Test substrates
Item
ThermalConductivity
Thickness of the
Copper Layer
Thickness of the
Substrate

CEM3 Substrate

Aluminum Substrate
2.1 (Thickness of the insulating
layer: 120μm)

W/m∙K

1.5

μm

35 (Non-through hole
double-sided substrate)

35

mm

1.0

1.1

-

R-1586(H) manufactured by
Panasonic Corporation

NRA-8 manufactured by NIPPONRIKA KOGYOSHO CO., LTD.

5.2 Results of the thermal evaluation
In this thermal evaluation, the forward current (IF) of 50-100mA was applied to each LED attached
on a CEM3 substrate and the forward current (IF) of 100-200mA was applied to each LED attached
on an aluminum substrate. See Figure 8 and Table 6 for the results.

150
Junction temperature: 135℃
CEM3基板ジャンクション温度
TJ of CEM3
substrate

125
Junction Temperature (℃)

Light Emitting DiodeP/N and
Manufacturer

Unit

アルミ基板
ジャンクション温度
TJ of aluminum
substrate

100

75

50

25
0

50
100
150
200
Forward Current per LED (mA)

250

Figure 8. Results of the evaluation using the test light sourceThis document contains tentative information, Nichia may change the contents without notice.
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Application Note
Table 6. Optical characteristics of the test light source modules and the evaluation results
CEM3 Substrate

Aluminum Substrate

Forward Current (IF) (mA/LED)
Operating Current of the Module (mA)

50
500

75
750

100
1000

100
1000

150
1500

200
2000

Operating Voltage of the Module (V)Power Dissipation (W)

77.4
38.7

78.7
59.0

79.9
79.7

80.6
80.6

82.9
124.4

84.8
169.6

Luminous Flux (lm)Luminous Efficacy (lm/W)

6746
174.3

9555
161.9

11887
149.1

12608
156.4

17148
137.9

20365
120.1

Temperature of the Solder Joint (℃)6
Junction Temperature (℃)7

46.6
52.0

58.1
66.3

71.2
82.4

56.4
67.7

81.5
98.9

94.0
117.7

Ambient Temperature (℃)

24.6

24.8

24.9

25.0

25.3

25.4

Light Emitting Diode6

The temperatures of the solder joint were measured using a thermocouple after the saturation
temperature had been reached.
7
The junction temperatures (TJ) were calculated using the thermal resistance of the LED:
RθJS=2.8°C/W
Figure 8 shows that the junction temperatures (TJ) were lower with the aluminum substrate thanwith the CEM3 substrate, the same result as obtained in the evaluations described in section 4.
Table 6 shows that the luminous efficacy of the LED at the same forward current (IF) was higher
with the aluminum substrate than with the CEM3 substrate.
In section 5.3, Nichia provides the evaluation results using a thermal imaging camera and thedetailed information of the CEM3 and the aluminum substrates.

This document contains tentative information, Nichia may change the contents without notice.
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Application Note
5.3 Comparing light source module characteristics between a CEM3 substrate and analuminum substrate.
Table 7. Comparison of the light source modules between a CEM3 and an aluminum substrate
CEM3 Substrate

Aluminum Substrate

Forward Current 100mA

Forward Current 100mA

Light Emitting Diode

Image of theTemperature
Distribution
Taken with a
ThermalImaging
CameraHeat
Dissipation

Solder Crack

DielectricStrength

・Suitable for low luminous flux applications
・The heat generated from the LEDs isdissipated radially. However, the temperature
distribution on the surface of the substrate isuneven.
・Poor heat transference to the heatsink(i.e. large difference in temperature between
the heatsink and substrate).
・Thermal grease is necessary when attaching
the substrate to a heatsink for a better heatdissipation performance.
・The temperatures of some of the LEDs arehigher because the substrate is not attachedto the heatsink appropriately under those
LEDs (i.e. the adhesion strength between theheatsink and substrate is lower).
・Since the NFMW48xAR LEDs are a resin
package, the difference in the coefficient ofthermal expansion between the LED and thesubstrate is small and the occurrence ofsolder cracks is low.
・The coefficient of thermal expansion of thesubstrate: 19-23×10-6
・The withstand voltage performance can beincreased by having an enough creepage
distance.

・Suitable for high luminous flux applications
・The heat generated from the LEDs isdissipated evenly across the substrate.
・Good heat transference to the heatsink(i.e. small difference in temperature between
the heatsink and substrate).
・The temperatures of some of the LEDs arehigher because the substrate is not attachedto the heatsink appropriately under thoseLEDs; however, this is still a better result
than with the CEM3 substrate.

・Since the NFMW48xAR LEDs are a resin
package, the difference in the coefficient ofthermal expansion between the LED and thesubstrate is small and the occurrence ofsolder cracks is low.
・The coefficient of thermal expansion of thesubstrate: 24×10-6
・The dielectric strength depends on the
dielectric strength of the insulating layer. The
withstand voltage performance is not high.
• The maximum allowable operating voltagethat can be applied is limited; if the circuit
voltage will be ≥100V, ensure that thedielectric strength of the insulating layer has
no issues.

This document contains tentative information, Nichia may change the contents without notice.
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Application Note
5.4 Circuit design considerations for the light source modules• Nichia recommends that each LED is operated at a constant current.
• The circuit must be designed to ensure that the Absolute Maximum Ratings are not exceeded foreach LED.
• In the case of operating at a constant voltage, Circuit B is recommended. If Circuit A is used, it
may cause the currents flowing through the LEDs to vary due to the variation in the forward
voltage characteristics of the LEDs on the circuit.

(A)

(B)

...

...

Light Emitting DiodeIn this evaluation, the junction temperatures (TJ) of some of the LEDs attached to the light source
modules became higher. It was because the LEDs were connected in parallel with each other andthe forward current flow to each one varied. In this circuit configuration, a current over the absolute
maximum rating may be applied to some LEDs affecting the reliability performance of the product.
When designing the circuit configuration of the LEDs for the chosen application, ensure that therequirements/recommendations below are taken into consideration:

For any questions regarding the design of the light source modules using the LEDs (e.g. forward
voltage distribution of the LED, LED ranks, etc.), contact a local Nichia sales representative.

6. Summary
The NFMW48xAR series LEDs have high heat dissipation to enable them to be used for various
applications. When designing the light source module with the LEDs, select the substrate that issuitable for the required heat dissipation performance for the chosen application by considering theresults of the thermal evaluations described herein. In addition to the temperature measurementswith a thermocouple, evaluating the temperature distribution using a thermal imaging camera isalso useful.
This application note has provided cautions/suggestions for the thermal design of the chosen
application using the NFMW48xAR series LEDs showing the evaluation results. However, theresults are examples for reference purposes only and may be different depending on the LED partnumber and/or the chosen operating conditions/environment. Sufficient verification must be done
prior to use to ensure there are no issues for the chosen application.

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

491 Oka, Kaminaka-Cho, Anan-Shi,
TOKUSHIMA 774-8601, JAPAN
Phone: +81-884-22-2311 Fax: +81-884-21-0148

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

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