Failure Analysis (FA) Introduction (III - Reliability ) Tung-Bao Lu 1 of 23
Reliability Stress Stress Reliability Geberal Condition Temperature Humidity Electrical Others Precondition Baking/L3/Reflowing V V - - Reflowing (SMT) JEDEC 240 o C/3X V - - Shock TCT -65 o C/+150 o c/15min V - - Shock TST -65 o C/+150 o c/15min V - - Shock PCT +121 o C/100%RH/2ATM V V - - HL-SLT +150oC V - - Time LT-SLT -65 o C V - - Time TH Storage 85 o C/85%RH V V - Time THB 85 o C/85%RH/Vcc V V V - HAST +130 o C/85%RH/Vcc V V V Accleeracted Tung-Bao Lu 2 of 23
Typical Preconditioning Defect Mode Moisture distribution Weak point Die surface Delaimintion Die crack Package crack Tung-Bao Lu 3 of 23
Preconditioning - Precondition L3 found 1 st open fail - FS/SS = 11/135 (8%) - LQFP 100L 18M SSDRAM - Open failed on some corner pins - Die-surface corner delamination - Modify die-attached epoxy - Modify die-pad structure 1 st bonding lifted by preconditioning stress (slot) (Scanning Electrical Microscope) Tung-Bao Lu 4 of 23
Preconditioning - Precondition L3 found 1 st open fail - FS/SS > 5% - TSOPII 44L DRAM - Open failed on random pins - Die-surface delamination Delamination layer (SAT C-SCAN) Surface Element Non-uniform (Wafer Process) Ball-neck broken by die surface delamination (C, N, O, Si) (1) (4) (C, N, O, Si) (C, N, O, Si) (2) (3) (C, O, Si) (Scanning Electrical Microscope) Tung-Bao Lu 5 of 23
Typical TCT/TST Defect Mode Stress Die surface delamination to cause EMC lifted, ball-neck broken TCT TST Weak point (expansion/shrinkage) Tung-Bao Lu 6 of 23
TCT - TCT 500C open fail - FS/SS=4/100 - SOJ 40L 4M DRAM - Open can be recovered and not stable while testing - SAT shows normal, no delamination Material changed - Change molding compound to provide Wedge bond broken but still connected (Scanning Electric Microscope) Tung-Bao Lu 7 of 23
TCT - TCT 1000C open fail - FS/SS=1/45 - QFP 100L - One pin open, 2 nd finger find delamination Process: - Waiting time from W/S->M/D control - Enhance W/B parameter Material - Change molding compound - Cleaning Lead-frame before W/B Wedge bond broken to lift (Scanning Electric Microscope) Tung-Bao Lu 8 of 23
TCT - TCT 1000C function fail - FS/SS=1/200 - TSOPII 54L 64M SDRAM Only corner special block failed -65 o C cold air +150 o C hot air (MOSAID Memory Tester) Failed block LOC taped damaged (Bonding process) Passivation damaged under LOC tape Improvement: Change to long-tape LOC tape to balance force Before improved After improved Modified (Long-type) (Optical Microscope, 500X) Tung-Bao Lu 9 of 23
TCT - TCT 1000C open fail - FS/SS=3/45 - minibga 8x10 48B To identify substrate opened by probing substrate plating line and solder ball -65 o C cold air +150 o C hot air Substrate (BT laminate) chip epoxy ball Open Supplier improve Substrate crack is found by DPA and SEM Poor quality substrate that can t been stressed after temperature cycling tests, crack is found and through Cu-line to cause opened. Crack is found by SEM after top-side DPA made Open Cu line crack Tung-Bao Lu 10 of 23
TCT - TCT 300C open fail - FS/SS=40/200 - LCD Driver IC, TCP package - Inner Lead Bonding Process (TAB) - Can pass 30C/130C - TCT condition: -65 o C/+150 o C/30min - Open located on wide side - Recovery after time aging - Inner lead dimension modify - Material/Structure limit Lead broken near to bump Tung-Bao Lu 11 of 23
TCT - TCT 1000C open fail - FS/SS=2/10 (2%) - 256M SDRAM SODIMM module - Solder ball connected - Condition: -20 o C/+90 o C/30min - Open located on random packages - Contact recovery (press package) Modify PCB solder ball opening Solder crack on package side Tung-Bao Lu 12 of 23
TST - Customer find after SMT process - TCP package - fixed pin open V1 Change tape design, and all pass Advanced RA After TST 200C, about 50% all open V2 Previous Design Revised Design -65 o C cold liq. +150 o C hot liq. Tung-Bao Lu 13 of 23
Typical Moisture (PCT, THB, HAST) Defect Mode Stress - Die surface delamination to cause EMC lifted, ball-neck broken - Al-pad corrosion Weak point - Metal migration Tung-Bao Lu 14 of 23
PCT - PCT 240H open fail - FS/SS=1/45 - PLCC 32L Flash - Open failed around corner special pins - Serious die surface delamination Change molding compound (Scanning Acoustic Tomograph) Ball lightly lifted around corner pins (Scanning Electrical Microscope) Tung-Bao Lu 15 of 23
PCT - PCT 216H open fail - FS/SS=1/45 - mbga 48B (Substrate) - Open failed - Die-surface delamination chip Substrate (BT laminate) epoxy ball - Change molding compound (Scanning Acoustic Tomograph) 1 st bonding lifted from device pad (Scanning Electrical Microscope) Tung-Bao Lu 16 of 23
PCT - PCT 96H open fail - FS/SS=3/45 - mbga 48B (Substrate) - Open failed around corner special pins - Substrate surface delamination chip Substrate (BT laminate) epoxy ball - Change molding compound - Change substrate solder resistance (Scanning Acoustic Tomograph) 2 nd Bonding finger lifted from substrate (Scanning Electrical Microscope) Tung-Bao Lu 17 of 23
PCT - PCT 240H leakage failed - FS/SS=1/45 - TSOPII 40L 4M DRAM Leakage failed on Pin 31 (LCAS) Normal Pin (Curve Tracer) - 3.2m Failed Pin:LCASB Gate oxide damaged (Wafer Process) 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 is found around failed pin Hot-spot (Scanning Electrical Microscope) ( Liquid Crystal Microscope) Tung-Bao Lu 18 of 23
THB - THB 500H Open/Leakage failed - FS/SS=7/32 - SOJ 40L 4M DRAM - Open/leakage failed on random pins - Serious die surface delamination THB passed THB failed (Scanning Acoustic Tomograph) Reliability ovens over-stressed Ball lightly lifted around failed pins (Scanning Electrical Microscope) Tung-Bao Lu 19 of 23
Typical HT/LT-SLT Defect Mode IMC Layer Crack (Au-Ball Lift) Kirkendall Void Tung-Bao Lu 20 of 23
Un-predicting Reliability Ion Migration Copper Migration Temperature-Humidity-Voltage/Bias Solder Migration Evaluation: Tandem pattern + Dew Cycling Test Tung-Bao Lu 21 of 23
Un-predicting Reliability Tin Whisker EIA JESD22-A12, May, 2005 Measuring Whisker Growth on Tin and Tin Alloy This document is not qualification standard!!! Tung-Bao Lu 22 of 23
Reliability and Failure Mechanism Process Step Failure Mechanism 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) Tung-Bao Lu 23 of 23