AB29_Luxeon K2 Assembly Info 3_14_07.qxp

Application Brief AB29
LUXEON® K2 Power LEDs
Assembly and Handling Information
Table of Contents
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Introduction
This application brief covers the recommended handling procedures
®
Pick and Place . . . . . . . . . . . . . . . .2
for LUXEON K2 Power Light Emitting Diodes (LEDs). Specifications
Lens Handling . . . . . . . . . . . . . . . .2
and procedures are also included for the proper surface mounting of
Lens Cleaning . . . . . . . . . . . . . . . . .3
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these emitters on printed circuit boards (PCBs).
The LUXEON K2 emitters have a silicone lens, which offers enhanced
optical properties and improved reliability. However, silicone is a softer
Pad Layout . . . . . . . . . . . . . . . . . . .3
Stencil Thickness and Coverage . . .4
Reflow Profile . . . . . . . . . . . . . . . . .5
Electrical Slug Isolation . . . . . . . . . .5
Board Placement Tolerance . . . . . .8
handling imperative to avoid damage to the emitters.
JEDEC Moisture Sensitivity Level . .9
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material and prone to attracting dust. These properties make proper
Pick and Place
Automated pickandplace equipment provides the best placement of LUXEON K2 emitters. For LUXEON K2 pick and place,
Philips Lumileds is recommending pickup from the lens but only under the guidelines below.
· The collet surface is the same profile as the LUXEON K2 lens
· The nozzle will suck up the LUXEON K2 unit from the tape while the tip of the collet is 0.2mm above the lens
· The pressure required to lift the LUXEON K2 is between 70 to 75Kpa
· The nozzle will purge the unit 0.15mm from the board surface with a pressure of 515Kpa
· The 0.15mm distance corresponds to the recommended thickness of the stencil
· Employ an active aligner with a camera that can adjust for any skew
Figure 1 shows an example of a pickandplace nozzle suitable for use with LUXEON K2 emitters.
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R = 2.00
2.80
3.5
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R = 2.85
0.40
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Figure 1. Pickandplace collet.
Lens Handling
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When utilizing a pickandplace machine, the collet must not place excessive pressure on the lens of the LED. Ensure the inner
surface of the collect is clean; the collet's dimensions are correct; and the correct pressure is applied.
Similar restrictions exist for manual handling. The LEDs should only be picked up by making contact with the sides of the LED
body; the hand tool should not put any pressure on the lens. Do not puncture or push the lens. Figures 2 and 3 illustrate correct
and incorrect handling.
Figure 2. Correct handling of LUXEON K2 emitters.
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
Figure 3. Incorrect handling do not grip the lens.
2
Lens Cleaning
Each LUXEON K2 emitter has a silicone lens. There are many benefits to the silicone lens in terms of optical properties and
improved reliability; however, silicone is a softer material and prone to attract dust. While a minimal amount of dust and debris on
the LED will not cause significant reductions in illumination, steps should be taken to keep the emitter free of dust. These include
keeping the LUXEON K2 Power LEDs in the manufacturer's package prior to assembly and storing assemblies in an enclosed
area after installing the emitters.
In the event that an emitter requires cleaning, use isopropyl alcohol to gently remove dirt from the lens. Do not use other solvents
as they may adversely react with the LED assembly.
Pad Layout
Users may be interested in creating a layout pad suitable for LUXEON K2 and LUXEON I, III, and V LED placement. This section
shows a comparison of the footprint of a LUXEON I, III or V LED on a LUXEON K2 pad layout.
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The pad layouts for LUXEON K2 and LUXEON I, III or V LEDs are shown in Figure 4 and 5. Figure 4 is the recommended pad
layout to achieve the most accurate reflow result for LUXEON K2 LEDs. Figure 5 is the recommended pad for LUXEON I, III,
and V LEDs.
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Figure 6 shows the resulting placement if a LUXEON I, III or V device is placed on the LUXEON K2 pad layout. As indicated, the
LUXEON I, III or V leads will hang beyond the LUXEON K2 pads. To compensate for the overhang, users can extend the
LUXEON K2 pads to match the size of the pads for the other LUXEON LEDs.
Figure 7 shows the LUXEON K2 footprint on the LUXEON I, III or V pad layout. The unconnected LUXEON K2 lead pins are
shown floating, with no pads. To achieve higher reflow accuracy, users can add two pads for the unconnected LUXEON K2
lead pins.
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Philips Lumileds only recommends populating LUXEON K2 and LUXEON I, III, and V LEDs on the pads indicated in Figures 4
and 5 respectively.
Figure 4. Recommended pad layout for LUXEON K2 devices.
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
Figure 5. Recommended pad layout for LUXEON I, III, and V devices.
3
Pad Layout, Continued
Figure 7. LUXEON K2 footprint on a LUXEON I, III or V pad layout.
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Figure 6. Standard LUXEON footprint on LUXEON K2 pad layout.
Stencil Thickness and Coverage
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The coverage on the pad and thickness of the stencil affect reflow accuracy. A thickness of 0.15mm and 100percent stencil
coverage are recommended for the LUXEON K2 emitters (see Figure 8). This configuration minimizes the voiding of the solder.
Figure 8. Stencil coverage (shown in red).
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
4
Reflow Profile
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LUXEON K2 emitters are compatible with surface mount technology and leadfree reflow. This greatly simplifies the manufac
turing process by eliminating the need for adhesives and epoxies. The robustness of the emitters is evident in that LUXEON K2
LEDs can be reflowed three times without degrading performance. The reflow solder profile is compatible with JEDEC 020c (see
Figure 9). The profile feature points are shown in Table 1, where all temperature points refer to the top side of the package,
measured on the body surface of the package.
JEDEC 020c
Figure 9. JEDEC 020c reflow solder profile.
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Table 1. JEDEC 020c profile feature points.
Lead Free Assembly
3°C / second max
Preheat Temperature Min ( Tsmin)
150°C
Preheat Temperature Max ( Tsmax)
200°C
Preheat Time ( tsmin to tsmax)
60 180 seconds
Temperature ( TL )
217°C
Time Maintained Above Temperature ( TL )
60 150 seconds
Peak / Classification Temperature ( TP )
260°C
Time Within 5°C of Actual Peak Temperature ( TP )
20 40 seconds
RampDown Rate
6°C / second max
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Profile Feature
Average RampUp Rate ( Tsmax to Tp )
Electrical Slug Isolation
Similar to the LUXEON I, III, and V, the slug of the LUXEON K2 must be electrically isolated from the anode, cathode, and other
slugs. This requirement stems from the basic internal construction of InGaN LUXEON K2 devices (see Figure 10).
The InGaN LED is placed onto a silicon submount consisting of zener diodes. The zener diodes, which provide ESD protection
to the LED, are connected to the slug and LED as shown in Figure 11. If the slug were not electrically isolated but connected to
the anode, cathode, or other LED slugs, the zeners could shunt the current away from the LED.
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
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Electrical Slug Isolation, Continued
Figure 10. Basic construction of the InGaN LED.
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Anode
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Slug
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Cathode
Figure 11. Zener diode connection to slug and LED.
Figure 12. Basic construction of the LUXEON K2 AlInGaP LED.
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
6
Electrical Slug Isolation, Continued
Consider a situation where three InGaN LEDs are connected in series with an electrically common slug. This schematic is shown
in Figure 13.
Heat Sink
Figure 13. Three InGaN LEDs in series with the slug on the same potential.
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This configuration shorts the inner four zeners so that only the two outer zeners will protect the LEDs. The breakdown of one
zener set can occur at levels as low as 7V. If the zeners break down, current will pass through the zeners and not the LEDs. This
situation is shown in Figure 14.
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⊕ Bias
x
x
x
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Heat Sink
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Figure 14. Result of electrically common heatslugs for InGaN LEDs.
The same situation can be considered for an AlInGaP LED where the slug is electrically connected to the anode. The effects of
connecting three AlInGaP LEDs in series with an electrically common heatslug are shown in Figure 15. This situation will render
two LEDs nonactive.
⊕ Bias
Heat Sink
Figure 15. Result of electrically common heatslugs for LUXEON K2 AlInGaP LEDs.
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
7
Board Placement Tolerance
For many PCB designs, accurate placement of the LUXEON K2 is critical. To meet accuracy requirements, the center of the
LUXEON K2 emitter must be correctly determined in respect to the center of the hexagonal pad. This can be accomplished
using the following procedure (see Figure 16):
1. Locate the two "bite" marks on the LUXEON K2 emitter package.
2. Find the center of the circle formed from the "bite" marks.
3. Draw a line connecting the centers of the two circles.
4. The midpoint of the line is the center of the LED.
5. Record the coordinates of this point (x1, y1).
The
1.
2.
3.
center of the LUXEON K2 hexagonal pad is found as follows (see Figure 17):
Draw a circle that touches the six hexagonal points of the pad.
The center point of this circle is the center of the hexagonal pad
Record this point (x2, y2).
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The offset between the LED center and the center of the hexagonal pad is (x1x2) and (y1y2). Philips Lumileds utilized the OGP
Smart Scope for this exercise. Any scope or shadowgraph that is capable of finding and storing the centers of circles may be
used for this measurement.
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Figure 16. Finding the center of the LED.
Figure 17. Finding the center of the pad.
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
8
JEDEC Moisture Sensitivity Level
LUXEON K2 Power LEDs are shipped in vacuumpacked airtight containers. Breaking this vacuum allows the introduction of
moisture into the LED, and can potentially result in damage to the package during assembly. During soldering or reflow, the
moisture will expand as the temperature rises, causing the package to crack.
JEDEC has defined eight levels for moisture sensitivity, as shown in Table 2.
The LUXEON K2 emitter offers superior performance with a Moisture Sensitivity Level of 2a and a floor life of four weeks before
any bake out is required. For emitters that exceed the shelf life, the bake out condition is 67 days at 40°C, as shown in Table 3.
Table 2. JEDEC Moisture Sensitivity Levels.
Soak Requirements
Floor Life
Standard
Time
Conditions
(hours)
Time
Conditions
1
Unlimited
≤ 30°C /
85% RH
168
+ 5/0
2
1 year
≤ 30°C /
60% RH
168
+ 5/0
2a
4 weeks
≤ 30°C /
60% RH
6962
+ 5/0
3
168 hours
≤ 30°C /
60% RH
1922
+ 5/0
4
72 hours
≤ 30°C /
60% RH
5
48 hours
≤ 30°C /
60% RH
5a
24 hours
≤ 30°C /
60% RH
6
Time on
Label (TOL)
85°C /
85% RH
85°C /
60% RH
120
+1/0
60°C /
60% RH
30°C /
60% RH
40
+1/0
60°C /
60% RH
962
+ 2/0
30°C /
60% RH
20
+0.5/0
60°C /
60% RH
722
+ 2/0
30°C /
60% RH
15
+0.5/0
60°C /
60% RH
482
+ 2/0
30°C /
60% RH
10
+0.5/0
60°C /
60% RH
TOL
30°C /
60% RH
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30°C /
60% RH
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≤ 30°C /
60% RH
Accelerated Environment
Time
Conditions
(hours)
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Level
LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
9
JEDEC Moisture Sensitivity Level, Continued
Table 3. JEDEC Bake Out Specifications.
Bake at 125°C
Bake at 90°C
≤ 5% RH
Saturated
@
30°C
85% RH
At Limit of
Floor Life
+72 hr @
30°C
60% RH
Saturated
@]
30°C
85% RH
At Limit of
Floor Life
+72 hr @
30°C
60% RH
≤ 1.4 mm
2a
3
4
5
5a
5 hours
9 hours
11 hours
12 hours
16 hours
3 hours
7 hours
7 hours
7 hours
10 hours
17
33
37
41
54
hours
hours
hours
hours
hours
11
23
23
24
24
≤ 2.0 mm
2a
3
4
5
5a
21
27
34
40
48
hours
hours
hours
hours
hours
16
17
20
25
40
hours
hours
hours
hours
hours
3
4
5
6
8
days
days
days
days
days
2
2
3
4
6
≤ 4.5 mm
2a
3
4
5
5a
48
48
48
48
48
hours
hours
hours
hours
hours
48
48
48
48
48
hours
hours
hours
hours
hours
10
10
10
10
10
days
days
days
days
days
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LUXEON K2 Assembly & Handling Information Application Brief AB29 (3/07)
Saturated
@
30°C
85% RH
At Limit of
Floor Life
+72 hr @]
30°C
60% RH
hours
hours
hours
hours
hours
8 days
13 days
15 days
17 days
22 days
5 days
9 days
9 days
10 days
10 days
days
days
days
days
days
29
37
47
57
79
days
days
days
days
days
22
23
28
35
56
days
days
days
days
days
7 days
8 days
10 days
10 days
10 days
79
79
79
79
79
days
days
days
days
days
67
67
67
67
67
days
days
days
days
days
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Level
Package Body
Thickness
Bake at 40°C
≤ 5% RH
10
Company Information
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LUXEON® is developed, manufactured and marketed by
Philips Lumileds Lighting Company. Philips Lumileds is a worldclass
supplier of Light Emitting Diodes (LEDs) producing billions of LEDs
annually. Philips Lumileds is a fully integrated supplier, producing core
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LED material in all three base colors (Red, Green, Blue) and White.
Philips Lumileds has R&D centers in San Jose, California and in
Philips Lumileds may make process or
materials changes affecting the perform
ance or other characteristics of our
products. These products supplied after
such changes will continue to meet
published specifications, but may not
be identical to products supplied as
samples or under prior orders.
The Netherlands and production capabilities in San Jose and Penang,
Malaysia. Founded in 1999, Philips Lumileds is the highflux LED
co
technology leader and is dedicated to bridging the gap between
solidstate LED technology and the lighting world. Philips Lumileds
technology, LEDs and systems are enabling new applications and
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markets in the lighting world.
www.luxeon.com
www.lumiledsfuture.com
For technical assistance or the
location of your nearest sales
office contact any of the
following:
North America:
+1 888 589 3662 or
askluxeon@futureelectronics.com
Europe:
00 800 443 88 873 or
luxeon.europe@futureelectronics.com
©2007 Philips Lumileds Lighting Company. All rights reserved. Product specifications are subject to
change without notice. Luxeon is a registered trademark of the Philips Lumileds Lighting Company in
the United States and other countries.
Asia:
800 5864 5337 or
lumileds.asia@futureelectronics.com