Images of Failures in Microelectronics Packaging and Assembly Ed Hare, Ph.D./SEM Lab, Inc. IMAPS NW - Feb. 11th 2004 Redmond, WA http://www.semlab.com 1
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Inner Layer Separation Between laminate copper and electroless copper Found Ca & S residues at failed interface http://www.semlab.com 3
Inner Layer Separation QC coupon mount from PWB fabricator lines of demarcation Missed during routine QC examination http://www.semlab.com 4
What is this? http://www.semlab.com 5
Microvia This is a poorly fabricated microvia There is little or no copper plating connecting to the layer-2 2 pad http://www.semlab.com 6
Microvia This is a good microvia There is uniform copper plating connecting to the layer-2 2 pad http://www.semlab.com 7
What is this? http://www.semlab.com 8
Drill Breakout The inner layer lands probably should have been larger diameter in this design This condition fails Class 3 criteria in IPC- A-600 (min. annular ring 0.001 in) http://www.semlab.com 9
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EOS Failure All four Vcc wire bonds are fused open There is no damage on the die Excessive current failure likely due to latch-up http://www.semlab.com 11
EOS Failure Vcc wire bond is fused open Fusing current of 1-1 mil gold wire is ~ 0.75 amps http://www.semlab.com 12
EOS Failure A short segment of metallization was fused open Likely caused by a voltage transient http://www.semlab.com 13
EOS Failure A short segment of metallization was fused open Likely caused by a voltage transient http://www.semlab.com 14
EOS Failure A short segment of metallization was fused open Likely caused by a voltage transient or ESD http://www.semlab.com 15
EOS Failure Gross electrical overstress damage http://www.semlab.com 16
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Bond Pad Corrosion Contributing causes * moisture * pop-corn damage * internal delam * P contamination http://www.semlab.com 18
Bond Pad Corrosion How to avoid * MSD control Use CSAM imaging and F/A to diagnose http://www.semlab.com 19
Bond Pad Corrosion Trace of P P due to molding compound or residual from IC fab http://www.semlab.com 20
Bond Pad Corrosion Bright spots are Ti-W barrier layer where Al is missing http://www.semlab.com 21
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Dendritic Growth on IC Die Silver and copper dendrites For all the same reasons as bond pad corrosion http://www.semlab.com 23
Dendritic Growth on IC Die or most of the same reasons as bond pad corrosion - moisture - ionic contamination - bias - internal delam http://www.semlab.com 24
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Bond Wire Sweep Bond wires are swept by the injection molding compound http://www.semlab.com 26
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Gold Embrittlement This is gold-embrittled eutectic Sn-Pb solder AuSn4 & AuSn2 platelets dispersed throughout the microstructure http://www.semlab.com 28
Gold Embrittlement Theory the gold- embrittlement caused voiding! AuSn4 & AuSn2 platelets trap volatiles http://www.semlab.com 29
Gold Embrittlement Theory the gold- embrittlement caused voiding! AuSn4 & AuSn2 platelets trap volatiles http://www.semlab.com 30
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BGA Mechanical Damage Probably tool damage Most extreme cases had missing balls http://www.semlab.com 32
BGA Mechanical Damage Corner has a missing ball http://www.semlab.com 33
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BGA Solder Joint Failure BGA solder joint failed at the BGA substrate Entrapped material includes flux and mask constituents Probably flux and mask are chemically incompatible http://www.semlab.com 35
BGA Solder Joint Failure This is a different example Entrapped material likely debris from plastic trays http://www.semlab.com 36
BGA Solder Joint Failure This is the fracture surface at the BGA substrate (different location) IPC specifications allow up to 25% http://www.semlab.com 37
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ENIG Black Pad Syndrome Brittle fracture at the solder/pwb pad interface More specifically between the Ni3Sn4 IMC layer and the P-P rich EN http://www.semlab.com 39
ENIG Black Pad Syndrome Very fine line brittle fracture at the solder/pwb pad interface http://www.semlab.com 40
ENIG Black Pad Syndrome Very thin (~ 0.25 micron) P-rich P EN layer in contact with the Ni3Sn4 IMC layer http://www.semlab.com 41
ENIG Black Pad Syndrome 2 nd example Very thin (~ 0.25 micron) P-rich P EN layer in contact with the Ni3Sn4 IMC layer http://www.semlab.com 42
ENIG Black Pad Syndrome ~ 18 wt% P at the fracture surface versus 7 9 wt% P for EN bulk http://www.semlab.com 43
ENIG Black Pad Syndrome IG spiking Hyper-etching etching of EN in IG bath http://www.semlab.com 44
ENIG Black Pad Syndrome 2 nd example IG spiking Hyper-etching etching of EN in IG bath http://www.semlab.com 45
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Failed SMD Inductor Discoloration of magnet wire Open circuited coil http://www.semlab.com 47
Failed SMD Inductor Encapsulant voids around magnet wire Magnet wire cross- section reduced due to corrosion http://www.semlab.com 48
Failed SMD Inductor Corrosion due to Cl & Br from activated flux that wicked into the coil http://www.semlab.com 49
Failed SMD Inductor Corrosion due to Cl & Br from activated flux that wicked into the coil http://www.semlab.com 50
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Failed Resistor Network Joint Classic thermal fatigue failure Voids may be a contributing factor http://www.semlab.com 52
Failed Resistor Network Joints Classic thermal fatigue failure Thermal expansion mismatch too large Failed after ~ 5 years of service http://www.semlab.com 53
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MLCC Knit Line Failure MLCC manufacturing defect Crack propagates and crosses plates causing electromigration short http://www.semlab.com 55
MLCC Knit Line Failure Delamination between plate and dielectric http://www.semlab.com 56
MLCC Dielectric Voids Void bridges plates and creates electromigration path http://www.semlab.com 57
MLCC Dielectric Voids Another example of MLCC dielectric voids http://www.semlab.com 58
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TSOP Electromigration Failure Electrical leakage failures No Clean Flux, but likely activated flux used in touch up http://www.semlab.com 60
TSOP Electromigration Failure Pb dendrites grow between signals and short them out Never mix No-Clean flux and activated flux http://www.semlab.com 61
TSOP Electromigration Failure Its even growing across the mold flash up by the package body! http://www.semlab.com 62
TSOP Electromigration Failure There is nothing quite like a pretty picture of a Pb-dendrite http://www.semlab.com 63
CONCLUSIONS Dendrites? Go ahead, make my day Bond pad corrosion? Bring it on! Black pad syndrome? Not a HASL Ed Hare, Ph.D./SEM Lab, Inc. http://www.semlab.com 64