Assembly of LEDs - ASM Assembly Systems

Transcription

Assembly of LEDs
productronica 2011
ASM Siplace Inhouse Show
Kurt-Jürgen Lang (Applications Engineering)
Agenda
1. LED Construction / Package Variety
2. Process Flow / Solder Pad and PCB Design
3. Solder Paste Printing
4. Pick&Place / Nozzle Design
5. Reflow Soldering
6. Binning / White LEDs / RGB LEDs
7. Applications
8. Specifics
9. Outlook / Additional Information
Assembly of LEDs | 15.11.2011 | Page 2
OSRAM Opto Semiconductors – productronica 2011-11-10-E.ppt | Date: 15.11.2011 | OS LED AE B | LKJ
Definitions
LED Chip/Die
Thinfilm
LED Package
Technology
LED Luminaire
InGaAlP
red / yellow
InGaN
blue / green
white
LED Construction
High Power LED Package
Ceramic based Package
Leadframe based package
OSLON
Golden DRAGON
Lens
Die
ESD Diode
Wire Bond
Ceramic
Metallization
LED Package Technology
OSRAM OSTAR
wer
o
P
h
g
: Hi
Trend
OSLON
DRAGON
Advanced Power
TOPLED
Power TOPLED
TOPLED
PointLED
Trend
Mini TOPLED
: Mini
m um
Chipled
size
Micro
SIDELED
SmartLED
FIREFLY
Standard SMT Process Flow
Process Flow
SMD LED
Solder Paste
Stencil Print
Pick & Place
Components
Standard SMT Equipment
Reflow
Soldering
Solder Pad Design
Parameter for solder pad design
•
•
•
optimized positioning – self-centering - (no turning, no tilting) of component after reflow
good heat distribution
avoid solder failures (shorts, tombstoning, …)
Beispiel OSLON LED
foot print /
solder land
Thermal Management
In order to distribute the heat
over the PCB the Copper
area should be maximized in
the Layout
Solder Pad Design
Self-centering or self alignment
For optimization of LED positioning the self-centering effect during reflow can be used
NSMD Non Solder Mask Defined or HalfSMD or copper
defined layout is recommended
Solid area is copper / solder pad
Self-centering effect at
symmetric LEDs
LED will be aligned centric on
the pad because of symmetrical
wetting forces
Hatched area is solder resist
example
Power TOPLED
no Cu lines under the component to avoid
that package body hit the ground
With the self-centering or self alignment effect it is possible to get a position accuracy to a reverence
point (Fiducial Mark) of <± 0,1mm for symmetric components.
Solder Paste Printing
Failure distribution SMT process
The application of solder paste has a significant
influence on the solder quality, it causes
around 60 - 70% of all failures in the SMT
assembly process flow
6%
15%
15%
pick & place
64%
reflow
solder paste printing
other
Source: C.H. Mangin
Requirements for a proper solder printing
• Exact positioning (alignment of solder deposit to
pad/lands)
• accurate geometry, defined edges
• Exact deposit volume, no doggy ears
• No smearing or solder lump
Stencil Design
• The printed solder volume deposit is determined of the stencil opening (aperture)
and the thickness of the stencil.
• The solder-joint thickness (standoff height) of SMT LEDs should be typically
between 45 µm to 75 µm.
• Stencil thickness used in SMT industry varies from 100µm to 150µm (0,004in to
0,006in) range, with typically OSRAM Opto Semiconductors use and
recommend 120µm for SMT LEDs.
The actual used stencil thickness depends on
the other SMD components on the PCB.
tilted Golden DRAGON caused from
excessive solder
Example Golden DRAGON
Aperture Design / SPI Solder Paste Inspection
Solder Paste
Stencil design: Example for OSRAM
OSTAR Compact
Electrical Pads: Anode/Cathode
Reduction afloat 50µm – 100µm
compared to solder land
Solder Pad / Land
Heat Spreader / Thermal Pad
Reduction of 30% - 40% compared
to solder land
3D-SPI
Anode Pad
For process evaluation /
control and failure
prevention it is recommended for all LEDs with
exposed heat spreader
(thermal pad) like Golden DRAGON, OSLON,
OSRAM OSTAR SMT/Compact, to check
regularly (SPI) the solder paste volume under
the heat spreader.
Thermal Pad or
Heat Spreader
electrically isolated
Cathode Pad
proper solder paste print
Voiding / Stencil Aperture
Voiding
• Voids have a significant influence on the second board
reliability
• Voids in solder joints tighten the problem of local
unbalanced spread of electricity and heat -> hot spots
Because of an optimized aperture-design for all large area
solder lands (heat spreader) the voiding can be minimized. A
design with smaller multiple openings in the stencil enables
an out-gassing of the volatile solder paste/flux materials
during the reflow soldering.
Voids
X-ray Image OSLON LED
Max. Void area
In industry standards like IPC-A-610 D or J-STD-001D (which refer only to surface mount area
array components like BGA, CSP, …) the amount of voids (verified by the x-ray pattern)
should be less than 25%.
Whereas in internal studies and simulations OSRAM Opto Semiconductors determined a
maximum up to 30% of voids in the thermal pad which have only a minor effect on the thermal
resistance. The limit of the acceptable voiding can vary for each application and depends on
the power dissipation and the total thermal performance of the system, affected by the used
PCB materials.
Handling and Storage
Wrong Storage and Handling
In general, the use of all types of sharp objects should be avoided in order to prevent damage of silicon
encapsulate, lens, or the glass cap, since this can lead to a optical degradation or complete failure of the
component.
For manual assembly and placement the
use of so-called vacuum tweezers is
recommended.
For correct handling
pick the LED only on
the ceramic base
Incorrect,
don’t touch the lens!
PCBs or assemblies containig LEDs should not be
stacked in a way that force is applied to the LED, or
should not handled dirctly on the LED.
incorrect
Generrally, all LED assemblys should return to room temperature after soldering, before
subsequent handling, or next process step.
Pick & Place
Pipette / Nozzle / Pick-up Tool
When processing in automatic pick & place machines care should be taken to:
• appropriate Pipette / Nozzle / Pick-up Tool
• conform process parameters like placement force (max. 2N)
For additional detailed information see App. Note:
Recommended Pick & Place Tools (Nozzles) for LEDs of OSRAM Opto Semiconductors
Example: Nozzle recommendation
Pipette / Nozzle / Pick-up Tool Design
Considerations for Vacuum-Nozzle design
• Package Type / Geometry
- Plastic housing with reflector (pick-up collar)
- Ceramic substrate / LED-die / Silicon casting
- Flat casting
- Lens
• Casting / Lens material
- Resin
- Plastic (PC, Epoxy, …)
- Silicone (different hardness, sticky)
• Avoid air-leakage
• Tape pocket (Dimension)
• Nozzle material / Manufacturing / Cost
- plastic, metal, ceramic, …
- abrasion
Customized LED nozzle
Examples
TOPLED Compact (5630)
Lead frame based reflector package with planar resin
Adopted Nozzle geometry prevents
Damage (crack, scratches, …) of casting area
Brocken bond wire
LED sticks on Nozzle
Examples
Ceramic substrate with molded silicon lens, different lens geometries
Adopted Nozzle geometry,
No damage of primary optics (lens) and bone wire
No sticking (silicone lens; tackiness, different hardness)
No tilted pick-up
OSLON Familie
Examples
White SMD reflector package with clear silicone lens
Adopted Nozzle geometry
No damage of primary optics (crack, scratches, …)
With flattened sides smooth step in tape pocket
Golden DRAGON oval Plus
Marking of Cathode
• Marking only on top side
• Marking on top / bottom side
perfect !
No perfect !
Why is it important ?
Bowl-Feeder Assembly
• Use of Bowl-Feeder need unique cathode marking and recognition
• Vision-System can recognize the wrong position and do an automatic
failure correction
Reflow Soldering
Basics
• In mass production Convection Reflow Soldering
(with forced air or nitrogen convection) is the most
common reflow method. For superior solder joint
connectivity results it is recommend soldering under
standard nitrogen atmosphere
• Basis and reference point for reflow soldering is the
JEDEC standard J-STD 020D.01
OSRAM 12 Zone confection reflow oven
• Because of different board designs use different number and types of
components, solder pastes, reflow ovens, and circuit board materials and
designs, no single temperature profile works for all possible combinations.
• OSRAM OS recommends to follow the recommended soldering profile provided
by the solder paste manufacturer, and do a further optimization according the
needs of the actual used board.
For additional deatailled informations
see App. Notes:
Further Details on lead free reflow soldering of LEDs
Measuring of the Temperature Profile during the Reflow Solder Process
Reflow Profile for lead free soldering
300,00
250,00
TP 245°C
240°C
tP
pD
200,00
t
2°
C
/s
/s
3°C
tS
Ra
m
p
Up
Flux Activation
Temp.
150,00
n
ow
Temp T [°C]
m
Ra
Melting Temp. of
Solder
217°C
100,00
50,00
25°C
Preheat
Flux Activation
0,00
0
50
100
Cooling
Reflow
150
time t [sec]
200
250
300
Reflow profile data sheet recommendation
Pb-Free (SnAgCu) Assembly
Profile Feature
Recommendation
Max. Ratings
Ramp-Up Rate to Preheat *)
25°C to 150°C
2°C/sec
3°C/sec
Time tS from TSmin to TSmax
(150°C-200°C)
100s
min. 60sec max. 120sec
Ramp-Up Rate to Peak *)
180°C to P L
2°C/sec
3°C/sec
Liquidus Temperature TL
217°C
Time tL above TL
80sec
max. 100sec
Peak Temperature TP
245°C
max. 260°C
max. 250°C
Time tP within 5°C of the specified peak
temperature TP – 5K
20sec
Ramp-Down Rate *)
TP to 100°C
3°C/sec
Time 25 °C to Peak temperature
Notes:
(power / TOPLED w lens)
min. 10sec max. 30sec
profile measuring
6°C/sec maximum
4°C/sec maximum
(power / TOPLED w lens)
max. 8 min.
All temperatures refer to the center of the package, measured on the top of the component
*) slope calculation ∆T/∆t: ∆t max. 5sec; fulfillment for the whole T-range
For superior solder joint connectivity results we recommend soldering under standard
nitrogen atmosphere
Assembly of different brightness groups of LEDs
In production all LEDs are sorted in different groups/categories/Bins; grouping parameters:
– Brightness
– Forward voltage
– Wavelength (chromatic LEDs) /
Color Coordinate (white point)
To get homogenous illumination of the dashboard, each
different brightness group need a specific resistor
12 or more combinations,
high variety of assembly
BOMs
Solution: intelligent
assembly software
White LEDs
Principe to generate white light
• The chip produces blue light, the epoxy
surrounding the chip is mixed with a
phosphor converter material (yellow).
• This combination of colors (blue and
yellow) makes the white light.
• Color coordinates cx,cy (WP white point)
can be adjusted by mixing ration of blue
and yellow
• Use of multi phosphor fine tuning of wp
Different method’s for white LED light
Color Rendering Index
RGB LEDs
Single-Chip-LEDs
typ. ratio for white
(cx=0,3 / cy=0,3)
R ≈ 28%
G ≈ 64%
B ≈ 8%
Multi-Chip-LEDs
Additively mix of three primary colors (RGB) to produce a uniform color
Depending on the intensity of the individual primary colors, the resulting mixed color can be specified
Typically an additional green LED to form a RGGB cluster is used to drive the LEDs optimized
conditions, and to minimize effects related to color shifting, aging and brightness reduction
for optimum color homogeneity, it is
recommended that the individual colored
LEDs be organized in a compact cluster
arrangement
LED Key Markets
Automotive
Forward Lighting
Consumer
Safety
Mobile
General Lighting
Industry
Video Walls
TV / Monitors
White Goods
Streetlighting
Shoplighting
LCD BLU Back Light Unit
Edge Light or Light guide BLU
Basic Construction
• LEDs arranged in series as a light bar
• Light of LEDs couples in at the edges of a light guide
plate
• The light is guided over total reflection's in the light
guide to the top-emitting-area
• Uniform distribution of light is achieved by special
microstructures (microlenses, Vshaped grooves) or
dispersion points on the surface of the planar
lightguide.
• Because of LED radiation characteristic, a particular distance (mixing area) has to
be maintained where the light from the single LEDs is mixed get a homogenous
illumination
mixing area
OSRAM OS Champ Combination
How to handle and use the production variation?
CIE x-y color diagram
White LEDs come in
slightly varying
color and
brightness
- white point / color
- forward voltage Vf
- wavelength
- brightness (flux)
1
0.9
low
high
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-5
-4
-3
-2
-1
0
1
2
3
4
5
Production distribution
low-high combination dstrb
OSRAM OS Champ Kombination
⇒Idea of CHAMP: Use more than one bin
for one BLU/TV/Monitor:
Bin-Combinations
High/Low, od. A/B od. black/white Position
EDGE BLU
Bin1 (low)
Bin2 (high)
Use SW Tools;
⇒Based on simulation and calculation define bin combinations which will allow OS to use 100% of
production distribution and still meet customer requirements
Specifics
BLU Assembly
• Assembly of BLU pcb bar (light bar)
15 …
27 … 65 inch … 85
Increasing LCD size require pcb length
up to 800mm
Assembly of High/Low –Binning or specific
RGB combination;
no change of reels within one pcb-panel
-> machine is checking if there are enough
LEDs on the reel for the next entire panel,
intelligent material management
Use the same bin combination number
when setup a new reel -> Barcode Scan
of each new reel
~ 100 LEDs for 46”
H
L
H
L
H
L
H
L
H
L
z. B. Bin-combination #125
H
Specifics
IMS Boards
• Assembly of heavy MCPCBs or IMS boards
To ensure optimal operation of High Power LEDs within the specified max. ratings, the total
thermal resistance of the system should be as low as feasible. For this reason the PCB design,
construction and material is crucial for an optimized thermal design
IMS (Insulated Metal Substrate)
Base Plate
Al or Cu
Source: Assetronics
Use of heavy MCPCBs needs
adopted conveyer units
Specifics
COB + SMD on same Board / Light tubes
• Chip on Board + standard SMD components
More often the Light Engine and the driver electronic is integrated on the same pcb
+
=
Die-Bonding + SMD assembly within same machine
• Retrofit LED- light tube
Assembly of LED-Light Tubes up to 1200mm -> increase long board option,
many small LED packages to get same radiation characteristic as fluorescent lamp;
also as CoB technology
Cleaning
Cleaning of LEDs
• Gernerally, lint-free swaps and isopropyl alcohol, IPA can be used for cleaning.
• If other cleansing solutions/materials and industrial cleaning
process are used it is recommended to test beforehand their
suitability
• Ultrasonic cleaning of LEDs is generally not
recommended.
• OSRAM OS recommends to use low-residue or no-clean
solder paste, which supersede PCB cleaning for flux residue
removal after soldering.
Source: Fa. ZESTRON
• For all components with glass cap (OSRAM OSTAR SMT/Compact, …) it is highly
recommended to design the application such that condensation and collected moisture on the
light source are prevented. Since the OSTAR involves an open component, the module should
be protected against damaging environmental influences – whether liquid or gaseous – such as
water spray, for example
For additional detailed information see App. Note:
Cleaning of LEDs
Outlook
LED with 2D (Datamatrix) Code
The 2D code will be scanned during pick & place
Unique forward / backward traceability
Outlook
OLED Organic LED
Principe
ORBEOS
1st serial OLED-Light source
Features:
•New opportunities in luminaire design
•Available with diffuse or reflective surface, with round or square design
•Aesthetic, ultra-flat and glare-free area light source
•High-quality warm-white light with CRI 80
•Instant on/off
ORBEOS OLED
Round glass substrate,
80mm light emitting area,
optical efficiency 25lm/W,
thickness 2.1mm,
weight 24g
Outlook
OLED Production
Pilot production line for OLED, ORBEOS
In future OLED production is expected as a low-cost Reel to
Reel printing process
Application Notes OSRAM OS web page
Where you can find information’s
on Processing and Handling
Thank you for your interest!
Name:
Kurt-Jürgen Lang
Department: Applications Engineering, OS LED AE B
Adress:
Leibnitzstr. 4, 93055 Regensburg
Mobil:
mailto:
+49 160 70 86 008
[email protected]

Assembly of LEDs - ASM Assembly Systems

Transcription

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