Failure Analysis (FA) Introduction

(1)

Failure Mode

(

(2)

Failure Mode

Reliability Stress

Reliability Geberal Condition Temperature Humidity Electrical Others

Precondition Baking/L3/Reflowing V V -

-Reflowing (SMT) JEDEC 240oC/3X V - - Shock

TCT -65oC/+150oc/15min V - - Shock TST -65oC/+150oc/15min V - - Shock PCT +121oC/100%RH/2ATM V V - -HL-SLT +150oC V - - Time LT-SLT -65oC V - - Time TH Storage 85oC/85%RH V V - Time THB 85oC/85%RH/Vcc V V V -HAST +130oC/85%RH/Vcc V V V Accleeracted Stress

(3)

Failure Mode

Typical Preconditioning Defect Mode

• Moisture distribution • Weak point

(4)

Failure Mode

Preconditioning

Failure found

- Precondition L3 found 1st _{open fail}

- FS/SS = 11/135 (8%)

- LQFP 100L 18M SSDRAM

Advanced EFA

- Open failed on some corner pins - Die-surface corner delamination

Advanced PFA

1st bonding lifted by preconditioning stress

Root cause confirm

- Modify die-attached epoxy - Modify die-pad structure

(Scanning Electrical Microscope)

(5)

Failure Mode

Preconditioning

Failure found

- Precondition L3 found 1st _{open fail}

- FS/SS > 5%

- TSOPII 44L DRAM

Advanced EFA

- Open failed on random pins - Die-surface delamination

Advanced PFA

Ball-neck broken by die surface delamination

Root cause confirm

Surface Element Non-uniform (Wafer Process)

Delamination layer (SAT C-SCAN) (1) (2) (3) (4) (C, N, O, Si) (C, N, O, Si) _{(C, N, O, Si)} (C, O, Si)

(6)

Failure Mode

Typical TCT/TST Defect Mode

• Stress

• Weak point (expansion/shrinkage)

Die surface delamination to cause EMC lifted, ball-neck broken

(7)

Failure Mode

(Scanning Electric Microscope)

TCT

Advanced PFA

Wedge bond broken but still connected

Root cause confirm

Material changed

- Change molding compound to provide

Failure found

- TCT 500C open fail - FS/SS=4/100 - SOJ 40L 4M DRAM

Advanced EFA

- Open can be recovered and not stable while testing

(8)

Failure Mode

(Scanning Electric Microscope)

TCT

Advanced PFA

Wedge bond broken to lift

Root cause confirm

Process:

- Waiting time from W/S->M/D control - Enhance W/B parameter

Material

- Change molding compound

- Cleaning Lead-frame before W/B

Failure found

- TCT 1000C open fail - FS/SS=1/45 - QFP 100L

Advanced EFA

(9)

Failure Mode

Failed block

Improvement:

Change to long-tape LOC tape to balance force

Before improved

Modified (Long-type)

(MOSAID Memory Tester)

After improved (Optical Microscope, 500X)

TCT

Failure found

- TCT 1000C function fail - FS/SS=1/200 - TSOPII 54L 64M SDRAM +150oC hot air -65oC cold air

Advanced EFA

Only corner special block failed

Advanced PFA

Passivation damaged under LOC tape

Root cause confirm

(10)

Failure Mode

TCT

+150oC hot air -65oC cold air

Advanced EFA

To identify substrate opened by probing substrate plating line and solder ball

Advanced PFA

Substrate crack is found by DPA and SEM

Root cause confirm

Supplier improve chip Substrate (BT laminate) ball epoxy Open

Crack is found by SEM

after top-side DPA made Open Cu line crack

Poor quality substrate that can’t been stressed after temperature cycling tests, crack is found and through Cu-line to cause opened.

Failure found

- TCT 1000C open fail

- FS/SS=3/45

(11)

Failure Mode

TCT

Advanced PFA

Lead broken near to bump

Root cause confirm

- Inner lead dimension modify - Material/Structure limit

Failure found

- FS/SS=40/200

- LCD Driver IC, TCP package

- Inner Lead Bonding Process (TAB) - Can pass 30C/130C

- TCT condition: -65o_C/+150o_C/30min

Advanced EFA

- Open located on wide side - Recovery after time aging

(12)

Failure Mode

TCT

Advanced PFA

Solder crack on package side

Root cause confirm

Modify PCB solder ball opening

Failure found

- FS/SS=2/10 (2%)

- 256M SDRAM SODIMM module - Solder ball connected

- Condition: -20o_C/+90o_C/30min

Advanced EFA

- Open located on random packages - Contact recovery (press package)

(13)

Failure Mode

TST

+150o_C hot liq. -65oC cold liq.

Advanced EFA

Advanced RA

After TST 200C, about 50% all open

Root cause confirm

Change tape design, and all pass

Failure found

- Customer find after SMT process - TCP package

- fixed pin open V1

V2

(14)

Failure Mode

Typical Moisture (PCT, THB, HAST) Defect Mode

• Stress

• Weak point

- Die surface delamination to cause EMC lifted, ball-neck broken

- Al-pad corrosion

(15)

Failure Mode

PCT

Failure found

- PCT 240H open fail - FS/SS=1/45 - PLCC 32L Flash

Advanced EFA

- Open failed around corner special pins - Serious die surface delamination

Advanced PFA

Ball lightly lifted around corner pins

Root cause confirm

Change molding compound

(Scanning Acoustic Tomograph)

(16)

Failure Mode

PCT

Failure found

- PCT 216H open fail - FS/SS=1/45 - mBGA 48B (Substrate)

Advanced EFA

- Open failed - Die-surface delamination

Advanced PFA

1st bonding lifted from device pad

Root cause confirm

chip

Substrate (BT laminate) ball

(17)

Failure Mode

PCT

Failure found

- PCT 96H open fail - FS/SS=3/45 - mBGA 48B (Substrate)

Advanced EFA

- Open failed around corner special pins - Substrate surface delamination

Advanced PFA

2nd Bonding finger lifted from substrate

Root cause confirm

- Change substrate solder resistance

chip

Substrate (BT laminate) ball

(18)

Failure Mode

Failed Pin:LCASB Normal Pin -3.2m (Curve Tracer)

For Normal Pin: Vcc=5.5V, VI=0~5.5V, Leakage Current≅0 For Failed Pin: Vcc=5.5V, VI=0V, Leakage Current= -3.2mA

Hot-spot

( Liquid Crystal Microscope) (Scanning Electrical Microscope)

PCT

Failure found

- PCT 240H leakage failed - FS/SS=1/45 - TSOPII 40L 4M DRAM

Advanced EFA

Leakage failed on Pin 31 (LCAS)

Advanced PFA

Hot-spot is found around failed pin

Root cause confirm

(19)

Failure Mode

THB

Failure found

- THB 500H Open/Leakage failed - FS/SS=7/32 - SOJ 40L 4M DRAM

Advanced EFA

- Open/leakage failed on random pins - Serious die surface delamination

Advanced PFA

Ball lightly lifted around failed pins

Root cause confirm

Reliability ovens over-stressed

(Scanning Electrical Microscope) THB passed THB failed

(20)

Failure Mode

Typical HT/LT-SLT Defect Mode

••••

IMC Layer Crack (Au-Ball Lift)

(21)

Failure Mode

Un-predicting Reliability Failure Mode – Ion Migration

Copper Migration

Solder Migration

Temperature-Humidity-Voltage/Bias

(22)

Failure Mode

Un-predicting Reliability Failure Mode – Tin Whisker

EIA JESD22-A12, May, 2005

“Measuring Whisker Growth on Tin and Tin Alloy… “

(23)

Failure Mode

Process Step Failure Mechanism Failure Mode Detect R. Test

Implantation - Junction leakage due to crystal defects Degradation of BV HTOL, LTOL - Implantation effects (Isolation & Channel) Leakage or Short ESD, EOS - Hot carrier effect

Oxidation - Silk bulk defect - thin oxide Short curcuit HTOL - Particle contamination Si surface Increase in Leakage ESD, EOS & on oxide layer

- Dielectric breakdown

Photolithography - Photoresist particle defect & pinholes Open curcuit HTOL, LTOL - Photoresist contamination Increase in Leakage THB

- Masking problem

Wire bonding - Ball missing & intermetallic Open curcuit TCT, TST, PCT

- Compound, bonding problem Intermitant open THB

- Pad contamination Leakage Resistance

- Over bonding condition - Underlayer cracking

- Loop & wire sagging problem

Package - Corrosion due to bulk or lead-to-EMC Open TCT, TST, PCT

gap moisture pentetration Surface leakage THB

- Poor material solderability

(refer to: Samsung/quality assurance/reliability)