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

Soldering Materials to Enable Heterogeneous Integration and Assembly (HIA)

• 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)

Wetting Comparison

BAD

GOOD

Tack Test method

• Equipment

– Texture Technologies TA.XT2

• Parameters

– Ambient Conditions

–Humidity: 50% ± 3%

–Room Temperature: 21.5°C ± 2°C

Comparative Tack as a Function of Time

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

Soldering Materials to Enable Heterogeneous Integration and Assembly (HIA)

• 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

• No flux residue by using room temperature DIW clean

WS-446HF Clean Capability

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

Soldering Materials to Enable Heterogeneous Integration and Assembly (HIA)

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

Indium 3.2HF Printing Performance

• 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

Thank you!