Failure Analysis (FA) Introduction (IC ) Tung-Bao Lu 1 of 29
Structure of conventional package gold wire leadframe chip EMC die-pad Failure Classification Physical Failure (Structure) - Popcorn - Delamination - Crack (Package/Die) Electrical Failure (Connection) - Open - Short - Leakage - Function In-Process Failure (Production) - Front-end (before molding) - Back-end (After molding) - Testing (FT/Burn-in) Reliability Failure (Qualification) - Temperature - Humidity - Pressure - Voltage Tung-Bao Lu 2 of 29
Popcorn ( 爆 裂 ) Failure Mechanism (1) Moisture absorption (L-1: 85oC/85%RH) (L-3: 30 o C/60%RH) (2) Moisture vaporization during heating (Reflow, 235 o C/10s) popcorn (3) Vapor force separating (delamination) leadframe Chip (4) Popcorn forming (package crack) (collapsed void) crack die-pad Tung-Bao Lu 3 of 29
TQFP package (bottom popcorn) FBGA package (top popcorn) Tung-Bao Lu 4 of 29
Delamination ( 離 裂 ) (1) Die surface (EMC/chip) (2) Leadframe (EMC/leadframe) gold wire leadframe chip EMC (4) Pad bottom (pad/emc) die-pad (3) Die Attach (chip/pad) crack crack Tung-Bao Lu 5 of 29
Crack ( 破 裂 ) EMC Crack ( 膠 體 破 裂 ) Die Crack ( 晶 片 破 裂 ) crack gold wire leadframe chip EMC die-pad crack Tung-Bao Lu 6 of 29
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CON Package Assembly Flow TCP Package Lapping Lapping Dicing Bondability Dicing Die attach Leadframe ILB TAB tape Wire bond Potting & Cure Resin Molding Compound Marking Ink Marking Ink Testing Dejunk/Trim M/V Plating Solder anode Defect punch Forming Packing/Ship Reel/Spacer Testing Packing /Ship Tube/Tray Tung-Bao Lu 8 of 29
Wiring Bondability (TSOP/BGA) Shift bonding (short/leakage, W/B) Ball lifted (open, W/B) Ball over-bonding (short, W/B) Tung-Bao Lu 9 of 29
Wiring Bondability (TSOP/BGA) Ball neck broken (W/B) Ball neck crack (W/B) Heel broken (open, W/B) Heel broken (open, W/B) Tung-Bao Lu 10 of 29
Inner Lead Bondability (TCP/COF) No bonding (open, ILB) Poor bonding (open, ILB) Thin bump (open, ILB) Thin lead (open, ILB) Tung-Bao Lu 11 of 29
Inner Lead Bondability (TCP/COF) Alloy bubble (short, ILB ) IL shifted (short, ILB) Metal bridged (short, ILB) Bump crush (short, ILB) Tung-Bao Lu 12 of 29
Bondability (Bonding Force) (function -> Leakage -> Short) Normal bondability After crating testing KNO3 solution etching Remove gold-ball bonding Inspect Al-pad damaged SiO2 layer is damaged Tung-Bao Lu 13 of 29
X-RAY Inspection (NDT) 2nd Bonding Broken Tung-Bao Lu 14 of 29
Open Failure Inner wire neck broken Chip damaged to impact the wire Pin- 1 Foreign insulator stuck on lead Pad contamination by Auger Spectrum 4000 2000 Counts 600 400 200 0-200 -400-600 DQ2 DQ13 DQ15 TiN Ti DQ2 DQ13 DQ15 Energy Counts 0-2000 Ti TiN F 2000 1000 DQ2 DQ13 DQ15 Si Au -4000 C O 500 Counts 0 Si -1000-2000 Al -3000 Energy 1200 Al Kinetic Energy (kev) 1600 Al F Tung-Bao Lu 15 of 29
Open Failure TSOPII 54L LOC (in-process open failed) PLCC 32L (Reflowing open failed) pin29 (X-Ray Microscope) (Optical Microscope, 40X) (SAT C-SCAN, die surface) Au-wire 2nd bond lifted 2nd-bonding lifted Lead-frame Open bonding is not easily detected by XRM However, after EMC decapsulation, 2nd bonding lifted is exposed by optical microscope (SEM, 300X) Open bonding is not easily detected by XRM bonding lifted is exposed by SEM Tung-Bao Lu 16 of 29
Open Failure Bending Test Vibration Test Output Y41 + - Open position Tape Output Y41 TFT Panel DC test open (Fail) ACF area SEM found concave and micro-crack (1800x) SEM observed output lead broken (2000x) Tung-Bao Lu 17 of 29
Open Failure TCP Product Inner Lead Bonding Broken TCP Product Resin Cause Broken TCP Product Inner Lead Peeling Tung-Bao Lu 18 of 29
Short Failure Over-compressed bonding Split epoxy between leadframe Shifted bonding Chip circuit burn out Tung-Bao Lu 19 of 29
Short Failure Wire lay on substrate finger to short After PCT tests, solder growth Sn whisker to connect two pins Unloading from PCB, solder bridged Tung-Bao Lu 20 of 29
Short Failure (Tin Whisker) (Compressive Stress) (Jay A. Brusse) Tung-Bao Lu 21 of 29
Short Failure Sn over-plating to lead short on tape Needle-like Sn grow to short while bonding Chip scratched to cause circuit short Au pad bubble to short while bonding Tung-Bao Lu 22 of 29
Leakage Failure IC Circuit burn-out Die crack Top Temperature = 35.0 0 C Corner die crack Corner Chipping Tung-Bao Lu 23 of 29
Function Failure Assembled Related Machine/Man Damaged Corner chipping Chip surface scratch Side chipping Tung-Bao Lu 24 of 29
Function Failure Assembled Related Environment (Particle Damaged) Particle damaged (~20um) Particle damaged (~10um) Tung-Bao Lu 25 of 29
ESD Cases of Driver ICs D-company, EOS/ESD wiring burn-out to short H-company, internal burn-out to short, ESD under pad ( 靜 電 防 護 元 件 ~ 保 險 絲 ) Tung-Bao Lu 26 of 29
Difference between ESD and EOS ESD = ElectroStatic Discharge Appearance of damage (tendency) Process of failure (ESD) The location of damage is very small and cannot be identified by visually examining the semiconductor chip Electric charge damages the IC chip of semiconductor device when it discharges through the device (EOS) EOS = Electrical Over Stress If the energy of EOS is large of damage, such as breaks in wiring on the chip due to melting, discoloration, and burning of the package, can be recognized. If the energy is small, it is difficult to distinguish damage caused by EOS from that caused by ESD A semiconductor device is damaged by application of an overvoltage or overcurrent while the device is operating (while the characteristics of the device are being used by the user) Cause of failure Discharge due to contact of a charged body with the pins of a semiconductor device or discharge of an electric charge that takes place in the device itself because of friction or other causes Generation of Latch-up, surge due to turning power on or off and measuring instruments on or off., shortcircuit of the load, solder chips, and patterns shortcircuit by metallic foreign objects. Photograph of chip Source: NEC information (1997, Guide to prevent damage for semiconductor devices by electrostatic discharge (ESD)) Tung-Bao Lu 27 of 29
Major Mode of Damages by ESD (1) Damage to oxide film (2) Junction destruction (3) Melting of wiring film (Gate oxide failed) (Junction Breakdown) (Wiring burn-out) - Thermal destruction - ESD (fine Al wiring is melted) EOS (coarse Al wiring) - Thin is easy - Gate film is only 10nm - Thin is easy - Reverse bias - Current concentration - Shallow is easy IC design trend: 1. Gate film is thinner 2. Junction is shallower 3. Al wiring is thinner => On-chip protection internal ESD protection Source: NEC information (1997, Guide to prevent damage for semiconductor devices by electrostatic discharge (ESD)) Tung-Bao Lu 28 of 29
Structure/Property Material Process Tung-Bao Lu 29 of 29