Images of Failures in Microelectronics Packaging and Assembly

Transcription

1 Images of Failures in Microelectronics Packaging and Assembly Ed Hare, Ph.D./SEM Lab, Inc. IMAPS NW - Feb. 11th 2004 Redmond, WA 1

2 What is this? 2

3 Inner Layer Separation Between laminate copper and electroless copper Found Ca & S residues at failed interface 3

4 Inner Layer Separation QC coupon mount from PWB fabricator lines of demarcation Missed during routine QC examination 4

5 What is this? 5

6 Microvia This is a poorly fabricated microvia There is little or no copper plating connecting to the layer-2 2 pad 6

7 Microvia This is a good microvia There is uniform copper plating connecting to the layer-2 2 pad 7

8 What is this? 8

9 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 in) 9

10 What is this? 10

11 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 11

12 EOS Failure Vcc wire bond is fused open Fusing current of 1-1 mil gold wire is ~ 0.75 amps 12

13 EOS Failure A short segment of metallization was fused open Likely caused by a voltage transient 13

14 EOS Failure A short segment of metallization was fused open Likely caused by a voltage transient 14

15 EOS Failure A short segment of metallization was fused open Likely caused by a voltage transient or ESD 15

16 EOS Failure Gross electrical overstress damage 16

17 What is this? 17

18 Bond Pad Corrosion Contributing causes * moisture * pop-corn damage * internal delam * P contamination 18

19 Bond Pad Corrosion How to avoid * MSD control Use CSAM imaging and F/A to diagnose 19

20 Bond Pad Corrosion Trace of P P due to molding compound or residual from IC fab 20

21 Bond Pad Corrosion Bright spots are Ti-W barrier layer where Al is missing 21

22 What is this? 22

23 Dendritic Growth on IC Die Silver and copper dendrites For all the same reasons as bond pad corrosion 23

24 Dendritic Growth on IC Die or most of the same reasons as bond pad corrosion - moisture - ionic contamination - bias - internal delam 24

25 What is this? 25

26 Bond Wire Sweep Bond wires are swept by the injection molding compound 26

27 What is this? 27

28 Gold Embrittlement This is gold-embrittled eutectic Sn-Pb solder AuSn4 & AuSn2 platelets dispersed throughout the microstructure 28

29 Gold Embrittlement Theory the gold- embrittlement caused voiding! AuSn4 & AuSn2 platelets trap volatiles 29

30 Gold Embrittlement Theory the gold- embrittlement caused voiding! AuSn4 & AuSn2 platelets trap volatiles 30

31 What is this? 31

32 BGA Mechanical Damage Probably tool damage Most extreme cases had missing balls 32

33 BGA Mechanical Damage Corner has a missing ball 33

34 What is this? 34

35 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 35

36 BGA Solder Joint Failure This is a different example Entrapped material likely debris from plastic trays 36

37 BGA Solder Joint Failure This is the fracture surface at the BGA substrate (different location) IPC specifications allow up to 25% 37

38 What is this? 38

39 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 39

40 ENIG Black Pad Syndrome Very fine line brittle fracture at the solder/pwb pad interface 40

41 ENIG Black Pad Syndrome Very thin (~ 0.25 micron) P-rich P EN layer in contact with the Ni3Sn4 IMC layer 41

42 ENIG Black Pad Syndrome 2 nd example Very thin (~ 0.25 micron) P-rich P EN layer in contact with the Ni3Sn4 IMC layer 42

43 ENIG Black Pad Syndrome ~ 18 wt% P at the fracture surface versus 7 9 wt% P for EN bulk 43

44 ENIG Black Pad Syndrome IG spiking Hyper-etching etching of EN in IG bath 44

45 ENIG Black Pad Syndrome 2 nd example IG spiking Hyper-etching etching of EN in IG bath 45

46 What is this? 46

47 Failed SMD Inductor Discoloration of magnet wire Open circuited coil 47

48 Failed SMD Inductor Encapsulant voids around magnet wire Magnet wire cross- section reduced due to corrosion 48

49 Failed SMD Inductor Corrosion due to Cl & Br from activated flux that wicked into the coil 49

50 Failed SMD Inductor Corrosion due to Cl & Br from activated flux that wicked into the coil 50

51 What is this? 51

52 Failed Resistor Network Joint Classic thermal fatigue failure Voids may be a contributing factor 52

53 Failed Resistor Network Joints Classic thermal fatigue failure Thermal expansion mismatch too large Failed after ~ 5 years of service 53

54 What is this? 54

55 MLCC Knit Line Failure MLCC manufacturing defect Crack propagates and crosses plates causing electromigration short 55

56 MLCC Knit Line Failure Delamination between plate and dielectric 56

57 MLCC Dielectric Voids Void bridges plates and creates electromigration path 57

58 MLCC Dielectric Voids Another example of MLCC dielectric voids 58

59 What is this? 59

60 TSOP Electromigration Failure Electrical leakage failures No Clean Flux, but likely activated flux used in touch up 60

61 TSOP Electromigration Failure Pb dendrites grow between signals and short them out Never mix No-Clean flux and activated flux 61

62 TSOP Electromigration Failure Its even growing across the mold flash up by the package body! 62

63 TSOP Electromigration Failure There is nothing quite like a pretty picture of a Pb-dendrite 63

64 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. 64