THE CHALLENGE AND SOLUTION ON HETEROGENEOUS INTEGRATION ASSEMBLY
Indium Corp / Jason Chou
19-Sep-2019
• IC device technology nodes move toward 3-5nm, we are now at the limit of Moore’s law
• Advanced package enablers for greater functionality integration but induce some challenge:
– Warpage induced open failure
– Flux residue and Cleaning issues
– Dendrite and reliability issues on fine-pitch Cu-trace packages
– 1st pass yields and flux residue on BGA BM applications
– 1-step OSP BGA BM applications
– Printing, wetting, and cleaning capabilities for ultra-fine-pitch solder paste
The Challenge and Solution on Heterogeneous Integration Assembly
• Package size became larger
• Number of I/O increase but pitch is decrease
• Die thickness thinner and Substrate more complicate
• 3D Stack die and PoP application
• Less flux dipping amount on the bump / Cu-pillar
10/21/2019
Flip Chip Package Challenge
• Halogen-free
• Designed for dipping applications
• Excellent solderability on various metallizations
• Low voiding
• Uniform dipping performance over extended period
• Cleanable with DI water only
• Room temperature storage up to 10 months
WS-446-HF Flip Chip Flux
Property Value Test Method
Typical Viscosity 19kcps (5mins) Brookfield HB DVII ± CP (5rpm)
Typical Acid Number 91mg KOH/g Titration
Typical Tack Strength 240g J-STD-005 (IPC-TM-650 2.4.44)
Shelf Life 0-30oC for
10 months
Viscosity change/microscope examination
WS-446-HF Flip Chip Flux
• Good wetting, reduce open joints
• High tackiness to hold die in place, reduce die tilt
• Eliminate dendrite issue
• Good clean ability
WS-446-HF Flip Chip Flux
Wetting Test Method
1. Print flux onto metallized
surface
2. Place spheres onto flux
deposit
3. Reflow (air or N2 [typical])
4. Measure reflowed height
deposit
5. Calculate spread ratio
(wetting)
Tack Test method
• Equipment
– Texture Technologies TA.XT2
• Parameters
– Ambient Conditions
–Humidity: 50% ± 3%
–Room Temperature: 21.5°C ± 2°C
Reduce Open Joint
• Good wetting
• Good tack to hold FC die in place even though there is warpage issue
• Cleaning test to find the best flux for Flip Chip process
FC Flux Clean Capability Study
print 7 dot of flux on silicon wafer Hot plate baking
RT DIW to see the solubility
• Flip chip face some challenge in cleaning for big die and small gap package
• The clean capability WS-446HF is best @ RT DIW
FC Flux Clean Capability Test
Flux residue
Competit
or-1
Competi
tor-2
• WS-446HF has better yield performance
– Better wetting power and higher 1st pass yield
– Stable viscosity / tackiness vs time
– Better chemistry to remove the
OSP (1-step OSP process)
– Better cleaning under Room Temperature DIW
WS-446HF Has Better Performance
WS-446-HF shows good cleaning efficiency on OSP substrate base on FIB and SIMS analysis result
Cu OSP Study
Fresh Cu OSP Substrate Cu OSP Substrate after WS-446-HF Flux Clean
Product quality check item -Voids
Inner void check result (X-ray) X-ray check solder ball inner void area pre-SMT < 15%
WS-446FH 1-step is slightly better than PoR 2-step process
New flux type and 1 step BM maximum solder ball inner void 2.3%<15%
De-solder confirmation was pass no found Cu exposure.
Conclusion
Flux type BM step S/S Void
rate% Max. void X-ray Fail map Remark
Competitor
(POR)
Pre-clean +
BM
1F
(160IC)
9ea
5.63% 3.0% Pass
Indium
WS446HF 1 step BM
1F
(160IC)
7ea
4.38% 2.3% Pass
Indium WS446-HF de-solder
confirmation normal
X-ray check result
3.2HF Solder Paste Customers
• SiP WF/PA.. Module:
– 3.2HF/SAC305/T6
– 3.2HF/SAC305/T5
• SiP GPS module:
– 3.2HF/SAC387/T4.5
• SSD and Memory Card:
– 3.2HF/SAC305/T4
3.2HF Pb-Free Water-Soluble Solder Paste
• Features
– Exceptional printing
– Long stencil life
– Good response-to-pause
– Wide reflow profile window
– Outstanding slump resistance
– Excellent wetting capability
– Superior fine pitch soldering ability
– Low voiding
– Halogen-free
Test Result
• Flux Type (per J-STD-004A) ORH0
• Halide Content 0.00%
• SIR Pass
• Wetting test Pass
• Electromigration Pass
Typical Tackiness 50g
• Slump Test Pass
• Solder Ball Test Pass
J-STD-004* (IPC-TM-650)
J-STD-005* (IPC-TM-650)
Viscosity Test
• Typical Solder Paste Viscosity is using Malcom (10rpm) test condition. The
viscosity show stable for different thawing time
Spread factor test
• The wetting test (spread factor) is to determine the ability of a solder paste to
wet an oxidized copper surface and to qualitatively examine the amount of
spatter of the solder paste during reflow. The wetting test results show stable
as below table.
• Powder Sizes – Type 3
– Type 4
• Stencil – 4,5 mil thickness
– Laser-cut, e-formed
• Aperture Pattern – SMD and NSMD Pads
– Wide Variety of Area Ratios such as: • A.R. = 0.80 [16 mil circle (C16)]
• A.R. = 0.60 [12 mil circle (C12)]
• A.R. = 0.50 [10 mil circle (C10)]
• RtP Testing – Zero Hr; One Hr; Two Hr; Four Hr
Indium 3.2HF Printing: Critical to High Yields
Target: No outliers above 0.6 AR; No defect on first print after pause
• WS-446HF Flip Chip and BGA BM
–Good clean capability in RT DIW
–No Cu dendrite defect
– Better in wetting and warpage performance
• 3.2HF Water soluble paste
– Long stencil life and good printing performance
– Eliminate tombstone and poor wetting defect
–Good cleaning performance
10/21/2019
HIA Summary
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