Investigation on the development of intermetallic phases in electrodeposited lead-free solder / based stacks Io Mizushima and Peter Torben Tang IPU, Denmark
outlooks 1. Introduction 2. Experimental procedure 3. Results Diffusion couple test Soldering test 4. Summary
High temperature solder Product by B Component produced by A sold to B Soldering by A Soldering by B at 220 C
Candidates of high temperature soldering material (270-350 C) S.No Ternary Compositions S.No Ternary Compositions 1. -0.25-0.20Sb 10. -0.31-0.01 2. -0.36-0.08Zn 11. -0.35-0.21Sb 3. -0.33-0.02Ge 12. -0.26Ge-0.02Bi 4. -0.30-0.08Ag 13. -0.26Sb-0.20Bi 5. -0.29-0.08 14. -0.13-0.10Si 6. -0.18Ge-0.10In 15. -0.32-0.01Ag 7. -0.16Sb-0.22In 16. -0.15Ge-0.12 8. -0.30-0.24In 17. -0.24Ge-0.05Sb 9. -0.28-0.01Zn 18. Bi-0.16Sb-0.04In
- phase diagram Reasonable melting point
Process for production of based ternary alloy Alloy plating --X Ni High cost Unstable electrolyte Plating of multilayers and annealing / /-0,03 -X --X /-0,03Zn Ni Aging at 200 C Ni
Experimental procedure Electroplating of Ni, and -X on 30mm * 30mm copper plate (thickness measurement : X-ray) -X Ni plate 10 µm 20 µm 2 µm 500 µm tting with cutting machine As deposit 1hour 24hours r12hours Annealing at 200 C for several time lengthes 10 min 2hours 6hours moulding in epoxy, Mechanical polishing of cross-section Optical microscopy SEM/EDS
Cross-section of annealed stacked layers As deposited 200 C 2 hours 200 C 24 hours 4 2-0,1 Ni Ni Ni As deposited 200 C 2 hours 200 C 24 hours 2-0,03-0,1, -0,1, Ni Ni Ni As deposited 200 C 2 hours 200 C 24 hours -0,03Zn 2 4-0,1-0,1 Ni Ni Ni
Phase development as a function of annealing time 50 / -0.03/ -0.03Zn/ 50 50 40 40 40 thickness (µm) 30 20 10 0 4 4 4 thickness (µm) 30 30 2 2 2 20 20 ζ -0.1 ζ -0.1 10 10 0 0 0 6 12 18 24 0 6 12 18 24 0 6 12 18 24 annealing time (hour) annealing time (hour) annealing time (hour) thickness(µm) ζ -0.1 Fastest diffusion! ζ -0.1 2 4
Gold diffusion in system of -X on before aging / -0.03/ -0.03Zn/ 4() 2 Spectrum Spot 1 Spot 2 Spot 3 Spot 4 Spot 5 Spot 6 100.00 100.00 69.13 65.62 49.70 30.87 34.38 50.30 100.00 4() 4 Spectrum Spot 1 Spot 2 Spot 3 Spot 4 Spot 5 3.85 18.14 3.06 100.00 93.54 72.84 73.09 2.60 9.02 23.85 100.00 Spectrum Spot 1 Spot 2 Spot 3 Spot 4 Spot 5 Spot 6 -Zn Zn 2.96 7.85 100.00 97.04 100.00 78.78 46.97 Gold diffuse into layer even further from the interface 21.22 45.17 100.00
After aging / 4 2 4 10 min /-0,03 4 2 1 hour 2 2
Possibility for producing high melting soldering material As deposit 10 min aging 1 hour aging 4 2-0.03 2 Melting point 227 C Melting point 252 C Melting point 311-350 C? Not enough to tolerate temperature of 280 C... However, anyway it may become tolerant due to transformation from 4 to 2 during soldering Reasonable However, probably it cannot work for soldering at 330 C
New soldering process -0.03 10 min annealing 1 hour annealing 4 2 2 2kg 330 C, 10min 2kg 2kg Flux Flux
Soldering test at 330 degree for 10 min on stacks -0.03 on stacks NG as deposit 10min aged 1 hour aged
Soldering at 330 degree for 10min of on stacks on stacks 4 2 4 2 4 2 2 2 2-0.03 on stacks () 2 () 2 2 2() as deposit () 10min aged 2 1 hour aged
Soldering at 330 degree for 10 min of as deposited Ni//-0.03 Spectrum Spectrum 1 100.0 Spectrum 2 3.9 96.1 Spectrum 3 50.3 49.7 Spectrum 4 5.8 62.1 32.2 Spectrum 5 18.1 62.3 19.6 Spectrum 6 0.4 65.4 34.2 Spectrum 7 49.1 50.9 Spectrum 8 5.4 94.6 Spectrum 9 100.0
Soldering at 330 degree for 10 min of 10min annealed Ni//-0.03 Spectrum Spectrum 1 100.0 Spectrum 2 6.2 93.8 Spectrum 3 49.0 51.0 Spectrum 4 64.4 35.6 Spectrum 5 21.8 50.8 27.4 Spectrum 6 49.8 50.2 Spectrum 7 11.5 88.5 Spectrum 8 100.0 Spectrum 9 10.4 49.8 39.8 Spectrum 10 65.9 34.1 Spectrum 11 28.4 49.8 21.8
Diffusion of gold, tin and copper upon soldering -0.03-0.03
Summary For / electrodeposited stacks a small amount of copper in the layer makes thermal diffusion of both gold and tin faster, and contributes to thermal transformation to intermetallic phases with high melting point (>300 C) upon soldering at 330 C for 10 minutes. Therefore electroplating stacking - alloy containing a small amount of copper and gold could be suggested as an alternative electroplating process for fabrication of high-temperature soldering material.