Lumileds AB142 Assembly and handling information Datasheet

ILLUMINATION
Matrix Platform
LUXEON XF-3535L
Assembly and handling information
Introduction
This application brief addresses the recommended assembly and handling
procedures for the LUXEON XF-3535L family of flex strips. LUXEON XF-3535L is a
family of fully integrated solutions optimized for lighting applications requiring linear
arrays that can easily fit into any luminaire housing form factor. The overall solution
delivers optimized performance in combination with the quality of light needed
for distributed light source applications. Proper assembly, handling, and thermal
management, as outlined in this application brief, ensure high optical output and
reliability of these integrated solutions.
Scope
The assembly and handling guidelines in this Application Brief apply to the following
LUXEON XF-3535L products:
L235-xxyyAHLxByAC0
L235-xxyyAMLF5WAD0
L235-xxyyAULM5JAI0
x and y refer to variables as defined in the product nomenclature section of the
datasheet. In the remainder of this document the term “LUXEON XF-3535L” or “flex
strip” refers to any of the products listed above.
RoHS
COMPLIANT
AB142 Matrix Platform LUXEON XF-3535L Application Brief ©2015 Lumileds Holding B.V. All rights reserved.
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1. Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Handling Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Electrical Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1 Parallel Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Series Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3 Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.4 Allowable Series / Parallel Configurations per Class 2 Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Electrical Isolation and Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
5. Manual Assembly and Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 Surface Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3 Mounting Strip to Surface or Heatsink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4 Soldering Wires to the Flex Strip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5 Rework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.6 Rework – Removing the Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.7 ESD Measures During Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Thermal Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7. Thermal Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. Mounting the Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
About Lumileds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
2
1. Product Description
LUXEON XF-3535L features LUXEON 3535L LEDs, flexible substrate, electrical connections, and backside adhesive for easy
attachment to a heat sink. LUXEON XF-3535L comes in four main configurations.
• A 600mm length x 10mm wide strip with 36 LEDs at 16.67mm LED pitch
• A 300mm length x 10mm wide strip with 36 LEDs at 8.0mm LED pitch
• A 525mm length x 5.25mm wide strip with 56 LEDs at 8.45mm LED pitch
• A 1150mm length x 5.25mm wide strip with 108 LEDs at 10.0mm LED pitch
The 525mm and 1150mm strips come with IDC connectors at each end. 600mm and 300mm strips are available with two
IDC connectors at one end or without connectors and tin contacts only.
The polyimide-based copper-clad laminate Flex substrate has very good bending stability. The absolute minimum bending
diameter is 5cm. A smaller diameter is possible, but then the product should not be flattened. Strips should not be bent at
solder joints (where strips are daisy chained).
A high reflectivity white silicone coating is applied to the strip providing an initial reflectivity ~90 %.
2. Handling Precautions
The LUXEON XF-3535L is designed to maximize light output and reliability. However, improper handling of the strips may
damage the Flex and affect the overall performance and reliability. In order to minimize the risk of damage to the LUXEON
XF-3535L during handling, it should only be picked up via the foil and bending with a radius of less than 5cm on the flex
should be avoided as it may cause damage.
Although in general bending the LUXEON XF-3535L by less than 5cm should be avoided during handling, the strip can
withstand greater bending when mounted. For example the LUXEON XF-3535L can be folded or bent at right angles.
Caution: this must only be done midway (± 2mm) between the LEDs and only once. Folding the strip more than once will
cause the strip to fail (see Figure 1 and Figure 2). I.e. once folded it should not be flattened again.
Figure 1. Fold/bend at dotted lines only.
2.1 Cleaning
LUXEON XF-3535L emitters should not be exposed to dust and debris. Dust and debris may cause a decrease in optical
output. In the event that a LUXEON XF-3535L emitter(s) require cleaning, first try a gentle swabbing using a lint-free swab.
If needed Isopropyl alcohol (IPA) can be used to gently remove dirt from the top of the LED. Do not use other solvents as
they may adversely react with the LED assembly.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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Figure 2. Example of one-off Bend and Fold.
3. Electrical Connection
Care must be taken to correctly identify the positive and negative connection points on the ends of the flex.
± marks are printed on the flex as shown in Figure 3.
Figure 3. Identifying +/- connection.
3.1 Parallel Connection
Two or more 600mm strips could be wired in the configuration shown in Figure 4. In this case, we have 12 x 6 LED cells in
parallel so the driver should be capable of supplying 18V at a nominal current of 1.2A. For a full list of allowable parallel/
series configurations, refer to Table 1.
Figure 4. Parallel connection.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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When making parallel connections of multiple flex strips, the total forward voltage remains constant, but the current has to
be multiplied by the number of strips. Care has to be taken to distribute the current evenly over the strips. Daisy chaining
will force the combined current to go through the thin Flex circuits and will cause voltage drops over longer lengths (i.e. if 2
or more strips daisy chained). The light output of the LEDs may drop depending on the electrical distance to the driver.
Figure 5. Caution: This configuration is possible but not recommended.
Figure 5 is possible, but could lead to LOP non uniformity along the length of the 2 LED strips. In general, the wiring in
Figure 4 is electrically equivalent and requires fewer wires.
Another alternate method is to power in/out at the middle of (in between) the 2 strips. If more strips are needed and if
optimal uniformity needs to be maintained along the length of the strips, then multiple input/output power nodes and
wires can be added.
3.2 Series Connection
When making a series connection, the required driver current remains the same, but the forward voltage has to be
multiplied by the numbers of Flex strips in series. Care has to be taken that higher voltages may require different
protection than low voltages. Please refer to local jurisdictional requirements.
Two Flex strips can be wired in the following configuration. For example in Figure 6 cells from one strip are in series with
the cells from the other strips.
Figure 6. Series connection.
The driver for Figure 6, should be capable of supplying 36V (2x 18V) at a nominal current of 600mA.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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3.3 Drivers
A suitable driver for use with the previous configuration is shown in Figure 7.
Figure 7. Lumileds Xitanium LD-R 30W 700mA (suitable for indoor use)
With this driver the LED current will be 700mA / 6 =116.7mA with a max total forward voltage of 2x 18.6V=37.2V. Thus the
total max power output of the driver will be 0.7Ax37.2V= 26W.
For other compatible drivers visit the online Design Tools at: lumileds.com/designtools
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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3.4 Allowable Series / Parallel Configurations per Class 2 Driver
Table 1. Allowable Series / Parallel Configurations per Class 2 driver
LUXEON XF
Product
Number
of Series
LEDs per
LED String
Number
of
Parallel
LED
Strings
per L2
Strip
Current
per LED
string (A)
Max
Voltage
per LED
string (V)
Number
of
Parallel
L2 Strips
Needed
Number
of Serial
L2 Strips
Needed
Total
Current
Required*
(A)
Total
Voltage
Required
(V)
Total
Power
Required
(W)
6
6
0.1
18.6
1
1
0.6
18.6
11
6
6
0.1
18.6
2
1
1.2
18.6
22
6
6
0.1
18.6
3
1
1.8
18.6
33
6
6
0.1
18.6
4
1
2.4
18.6
45
6
6
0.1
18.6
5
1
3
18.6
56
6
6
0.1
18.6
6
1
3.6
18.6
67
6
6
0.1
18.6
7
1
4.2
18.6
78
6
6
0.1
18.6
8
1
4.8
18.6
89
6
6
0.1
18.6
9
1
5.4
18.6
100
6
6
0.1
18.6
1
2
0.6
37.2
22
6
6
0.1
18.6
2
2
1.2
37.2
45
6
6
0.1
18.6
3
2
1.8
37.2
67
6
6
0.1
18.6
4
2
2.4
37.2
89
6
6
0.1
18.6
1
3
0.6
55.8
33
6
6
0.1
18.6
2
3
1.2
55.8
67
6
6
0.1
18.6
3
3
1.8
55.8
100
6
6
0.2
19.8
1
1
1.2
19.8
24
6
6
0.2
19.8
2
1
2.4
19.8
48
6
6
0.2
19.8
3
1
3.6
19.8
71
6
6
0.2
19.8
4
1
4.8
19.8
95
6
6
0.2
19.8
1
2
1.2
39.6
48
6
6
0.2
19.8
2
2
2.4
39.6
95
6
6
0.2
19.8
1
3
1.2
59.4
71
7
8
0.1
21.7
1
1
0.8
21.7
17
7
8
0.1
21.7
2
1
1.6
21.7
35
7
8
0.1
21.7
3
1
2.4
21.7
52
7
8
0.1
21.7
4
1
3.2
21.7
69
7
8
0.1
21.7
5
1
4
21.7
87
7
8
0.1
21.7
1
2
0.8
43.4
35
7
8
0.1
21.7
2
2
1.6
43.4
69
7
8
0.2
23.1
1
1
1.6
23.1
37
7
8
0.2
23.1
2
1
3.2
23.1
74
7
8
0.2
23.1
1
2
1.6
46.2
74
12
9
0.1
37.2
1
1
0.9
37.2
33
12
9
0.1
37.2
2
1
1.8
37.2
67
12
9
0.1
37.2
3
1
2.7
37.2
100
12
9
0.2
37.2
1
1
1.8
37.2
67
LUXEON XF-3535L
300 & 600mm
LUXEON XF-3535L
525mm
LUXEON XF-3535L
1150mm
Notes for Table 1:
1. These are operational boundaries per Class 2 Driver.
2. Each configuration can be duplicated with additional Class 2 drivers.
3. Vf drops can cause light output loss in series/parallel configurations.
4. *Orange cells are above AWG24 wire gauge max current rating. IDC connectors are designed for AWG24.
Higher rated wire gauge should be soldered to contact pads if required.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
7
4. Electrical Isolation and Safety
Most jurisdictions around the world impose some basic safety requirements on electrical appliances. For the US this is
covered by UL standards (UL 8750). Within the EU, equipment must conform to the Low Voltage Directive (LVD) 2006/95/
EC. The LVD ensures that electrical equipment within certain voltage limits provides a high level of protection. The Directive
covers electrical equipment with a voltage between 50 and 1000 V for alternating current and between 75 and 1500 V
for direct current. It should be noted that these voltage ratings refer to the voltage of the electrical input or output, not
to voltages that may appear inside the equipment. For most electrical equipment, the health aspects of emissions of
Electromagnetic Fields are also under the domain of the Low Voltage Directive.
It is also recommended that care should be taken to provide sufficient isolation at the strip ends when mounted to
metal parts.
5. Manual Assembly and Mounting
To securely apply LUXEON XF-3535L onto a substrate, follow these general steps:
• (optional) Cut the strip to the desired length
• Note: Only 300mm and 600mm strips are cuttable (in 100mm increments)
• Clean the mounting surface
• Apply the strip
• Solder the strip
• (if needed) Rework
These steps are detailed in the following slides.
5.1 Cutting
The LUXEON XF-3535L can be trimmed to the desired length by cutting with sharp scissors at the cell boundaries, see
Figure 8. If a large number of strips are to cut ceramic scissors could be considered.
Do not cut the strip at the reflective foil as this will render the strip unusable.
Figure 8. Indication where to cut.
5.2 Surface Cleaning
Use a new lint-free swab and IPA to clean the mounting surface (heat sink) and let it dry.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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5.3 Mounting Strip to Surface or Heatsink
The LUXEON XF-3535L is supplied with a high performance 3M adhesive tape. This tape has high bond and sheer strength
on materials with a high surface energy. These materials include glass, stainless steel, aluminium and high surface energy
plastics (e.g. ABS and PC). The recommended methods for mounting a strip is by using a wallpaper seam roller, e.g. from
Perfax: http://www.wallpaperwebstore.com/perfax-naadroller
Figure 9. Roller to apply the Flex strip.
It is recommended the roller is made from non-porous foam modulus so it can be easily cleaned, and thus avoiding
damaging the strip or the LEDs. The strip can also be mounted without a roller by applying pressure to the strip with the
hands; do not press on the LEDs directly as this may damage the LEDs. If so desired, ESD-safe polyester clean-room gloves
can be used.
To ensure desired alignment of the strip, mark the mount points for the end of the strip. This can be done with removable
tape as shown in Figure 10.
Figure 10. Mark surface with alignment strips.
Remove a few centimeters of the liner from the LUXEON XF-3535L strip and carefully place using the alignment strips as
reference. Take care the other end of the strip is properly aligned with the marker. Once part of the strip is fixed to the
surface, it is difficult to adjust.
Figure 11. Remove 3-4cm of the protective foil and fix one end of the strip.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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When the one side of the strip is fixed, remove most of the liner. Leave just enough liner to hold the strip at the end
without getting glue on the fingers. Ensure the strip remains straight preventing the strip from accidentally gluing itself to
the surface and avoid kinking the strip at the mount point.
Figure 12. Remove almost all of the protective foil and align the end, but do not place.
Keep the strip stretched tight to the second marker without touching the surface with the glue (Figure 12: Remove almost
all of the protective foil and align the end, but do not place). Apply the roller with steady pressure at the starting (glued)
end and run smoothly towards the far end maintaining alignment as the tool travels. (Figure 13)
Figure 13. Using the roller to fix the strip.
When the roller is near the end, the remainder of the liner can be removed.
Figure 14. Finished.
It may happen that small pockets of air are trapped below the strip. This can be visible as a small bump. In general, this
does not impact the long-term performance of the LUXEON XF-3535L.
The adhesion of the PSA to the mounting surface will reach 90% of its peak strength after 1 day. Heat and pressure can be
used to accelerate the curing cycle. For example, good adhesion has been achieved by storing LUXEON XF-3535L for one
hour at 80°C. Results may vary with different heat sink materials. Lumileds recommends that customers always perform
their own testing.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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5.4 Soldering Wires to the Flex Strip
Wires can be soldered before or after fixing the strip to the surface. The following process is suggested.
Pre-requisites:
• Grounded soldering iron, capable of reaching 350°C
• Stranded copper wire of 24 AWG or larger
• SAC305 solder wire
Prepare the electrical wires:
• Cut the wires to size.
• Strip a few millimetres of insulating material from the ends of the wires.
• Pre-tin the wires with a small amount of solder.
Prepare the LUXEON XF-3535L flex strip:
• Clean the electrical pads of the LUXEON XF-3535L flex strip with a lint-free swab and isopropyl alcohol to remove any
debris or particles.
Solder the pre-tinned wires to the pre-tinned electrical pads:
• Place the pre-tinned LUXEON XF-3535L flex strip on a thermally insulating surface
Figure 15. Solder points.
• Place the pre-tinned wire on the pre-tinned electrical pad.
• Place the tip of the soldering iron on the electrical pad and allow the solder to reflow around the wire. Do not place the
soldering iron on the electrical pad for more than 3 seconds to prevent any damage to the LUXEON XF-3535L flex strip.
If a solder joint cannot be established within this time, allow the LUXEON XF-3535L flex strip to cool before reapplying
the heat.
• Remove the soldering iron and allow the solder joint to cool.
5.5 Rework
If a flex strip was not placed correctly, it should be removed promptly. The longer it remains in place, the stronger the
bond. After 3 minutes it cannot be re-glued. It is recommended that if the flex needs to be removed it should be done
within 1 minute of application.
Note: the angle between the surface and the strip being pulled should not exceed 20 degrees, see Figure 16. Carefully
inspect the flex for damage, especially the copper traces right next to the LEDs. These are stressed the most during
removal. If in doubt, replace the flex.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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Figure 16. Removal of strip from surface.
In case the strip has been in place too long, the LUXEON XF-3535L flex strip may be very hard to remove without causing
damage to the flex or the luminaire. The strip should not be re-used in that case. Removal could be done in various ways:
Cutting:
Cutting the bondline is effective on small assemblies. This can be done with a sharp cutting tool or a fine tooth saw or a
textured wire, using liquid soap as a lubricant.
High Frequency Shock:
Small parts can be cooled to below -40°C where the 3M Tape will become rigid. A sharp impact focused near the bondline,
should fracture the adhesive. Once the part is warmed up to room temperature, the residual adhesive can be removed.
5.6 Rework – Removing the Adhesive
The residual adhesive can be removed using several methods:
Using the Stripe Off Wheel (3M part number 07498: Figure 17) is a special rubber disk which mounts onto a standard 3/8”
electric drill.
Figure 17. Stripe off wheel.
When the rotating disk is brought in contact with the adhesive residue, it lifts the adhesive from the surface. When used
properly the wheel does not damage painted surfaces. It helps to remove the bulk of the adhesive residue with a razor
scrapper or knife before using the wheel. This operation can be followed by using a cleaning wipe to remove debris.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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Abrading:
If surface damage is not an issue, residual adhesive can be removed with a porous abrasive disk or wheel. A detackifying
agent such as detergent/water solution or dry talc may be used to facilitate removal and help prevent clogging of the
abrasive. Low speeds are generally more effective than high speeds for removal to prevent excessive heat buildup. Once
the adhesive is lifted off the surface, a cleaning wipe can be used to remove the debris.
Solvents:
The adhesive residue can be wet with a solvent then covered with a plastic film and allowed to soak for 5-15 minutes. Once
the adhesive is softened use a scrapper to remove the adhesive. The Solvents to use include:
• 3MTM Citrus Base Cleaner
• MEK (Methyl-Ethyl-Ketone)
• Other commercial adhesive removers
Note: Follow all manufacture’s safety precautions when using solvents. These cleaning recommendations may not be
compliant with the requirements of certain Air Quality Management jurisdictions – Consult applicable rules before use.
If in doubt follow the guide ‘3M VHBTM Tape – Disassembly of VHB Tape bonded materials and removal of residue
adhesive’ Technical Bulletin
5.7 ESD Measures During Mounting
ESD precautions should be followed during mounting/assembling of the LUXEON XF-3535L flex strip onto a product.
Production Environment:
The LUXEON XF-3535L flex strip requires ESD measures in a production environment where values can exceed the values
shown in the ESD specifications table below. An ESD-safe production environment comprises of, among other things,
a grounded floor, work tables as well as other attributes. ESD-safe clothing and grounding of workers should also be
considered. (Figure 18)
Servicing and Installing Luminaires:
When servicing luminaires on site, grounding of the service field engineer should be considered
Figure 18. ESD measures.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
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6. Thermal Considerations
The LUXEON XF-3535L is provided with a copper layer that spreads the heat of the LEDs across the strip. This heatspreading function allows the LUXEON XF-3535L to be used without a large heat-sink. This allows flexibility in choosing
a housing and heat sink. For some applications, this built-in heat sink is sufficient. See Figure 19 for an indication of the
generated heat when the LUXEON XF-3535L flex strip hangs freely in an office environment at room temperature.
Figure 19. Free hanging Flex strip with
zoomed in thermal image.
Figure 20. Flex cells mounted on a tube with
alu tape: center 2.5cm, bottom 5cm wide.
When needed, an easy way of increasing the heat dissipation of the LUXEON XF-3535L flex strip is the use of aluminium
tape; see Figure 20. Since the tape is reflective, the thermal image shows the temperature of the aluminium tape
incorrectly: the area marked by the yellow circles does show the correct temperature of the tape (by using a small piece of
Kapton tape). From Figure 20 it is clear that the temperature of the LUXEON XF-3535L flex strip is lower when mounted on
aluminium tape. The advantage of using aluminium tape is that it adapts to the shape of the surface on which the strip is
mounted. Care should be taken that the adhesive used with the aluminium tape is temperature resistant.
Other more traditional heat sinks, or thin metal plates made of steel or aluminium are also possible.
7. Thermal Verification
Given the length of the LUXEON XF-3535L flex strip and the various methods by which it could be applied in a product,
there could be a significant temperature differences between different parts of the strip. It is recommended that to ensure
the maximum junction temperature of the LEDs is not exceeded the following procedure is followed:
Determine the hottest LED in the product.
A thermocouple or alternatively a contactless infra-red camera could be used.
Use a thermocouple on the hottest LED to measure the temperature of the LED solder pad (Ts).
Using this measured Ts, calculate the junction temperature (Tj ) of the LED using the following formula Tj = Ts +
Rθj-s x P, where Rθj-s = is specified in product datasheet and P is the electrical power applied to the LED in Watts.
Verify Tj thus obtained is below the maximum junction temperature allowed for the LUXEON 3535L emitter;
i.e. Tj must be below 125°C.If Tj is above 125°C, an additional heat-sink is needed.
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
14
8. Mounting the Thermocouple
Before mounting the thermocouple first determine the location of the hottest LED with the LUXEON XF-3535L mounted in
the application. Attach all fixtures (e.g. heat sink, lens and any cover) to closely simulate the actual application environment,
and use a drive current that corresponds to normal operating conditions. The preferred mounting method for the
thermocouple is to glue it to the solder pad. Soldering is also possible, but this carries a risk of either overheating the LED
or overheating the adhesive of the LUXEON XF-3535L.
Figure 21. Location of sensor pad.
The location of the sensor pad is right next to the cathode of the LUXEON emitter on the Flex strip, as shown in Figure
21. To ensure accurate readings, the thermocouple must make direct contact with the copper of the foil onto which the
LUXEON emitter pads are soldered, i.e. any solder mask or other masking layer must be first removed before mounting the
thermocouple onto the sensor pad of the LED.
RoHS
COMPLIANT
AB142 Matrix Platform LUXEON XF-3535L Application Brief 20150827 ©2015 Lumileds Holding B.V. All rights reserved.
15
About Lumileds
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quality and reliability.
For 100 years, Lumileds commitment to innovation has
helped customers pioneer breakthrough products in the
automotive, consumer and illumination markets.
Lumileds is shaping the future of light with our LEDs and
automotive lamps, and helping our customers illuminate
how people see the world around them.
To learn more about our portfolio of light engines, visit
lumileds.com.
©2015 Lumileds Holding B.V. All rights reserved.
LUXEON is a registered trademark of the Lumileds Holding B.V.
in the United States and other countries.
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AB142 Matrix Platform LUXEON XF-3535L
Application Brief 20150827
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