Investigation on the development of intermetallic phases in electrodeposited lead-free solder Au/Sn based stacks

Transcription

1 Investigation on the development of intermetallic phases in electrodeposited lead-free solder / based stacks Io Mizushima and Peter Torben Tang IPU, Denmark

2 outlooks 1. Introduction 2. Experimental procedure 3. Results Diffusion couple test Soldering test 4. Summary

3 High temperature solder Product by B Component produced by A sold to B Soldering by A Soldering by B at 220 C

4 Candidates of high temperature soldering material ( C) S.No Ternary Compositions S.No Ternary Compositions Sb Zn Sb Ge Ge-0.02Bi Ag Sb-0.20Bi Si Ge-0.10In Ag Sb-0.22In Ge In Ge-0.05Sb Zn 18. Bi-0.16Sb-0.04In

5 - phase diagram Reasonable melting point

6 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

7 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

8 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

9 Phase development as a function of annealing time 50 / -0.03/ -0.03Zn/ thickness (µm) thickness (µm) ζ -0.1 ζ annealing time (hour) annealing time (hour) annealing time (hour) thickness(µm) ζ -0.1 Fastest diffusion! ζ

10 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 () 4 Spectrum Spot 1 Spot 2 Spot 3 Spot 4 Spot Spectrum Spot 1 Spot 2 Spot 3 Spot 4 Spot 5 Spot 6 -Zn Zn Gold diffuse into layer even further from the interface

11 After aging / min /-0, hour 2 2

12 Possibility for producing high melting soldering material As deposit 10 min aging 1 hour aging Melting point 227 C Melting point 252 C Melting point 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

13 New soldering process min annealing 1 hour annealing kg 330 C, 10min 2kg 2kg Flux Flux

14 Soldering test at 330 degree for 10 min on stacks on stacks NG as deposit 10min aged 1 hour aged

15 Soldering at 330 degree for 10min of on stacks on stacks on stacks () 2 () 2 2 2() as deposit () 10min aged 2 1 hour aged

16 Soldering at 330 degree for 10 min of as deposited Ni//-0.03 Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum

17 Soldering at 330 degree for 10 min of 10min annealed Ni//-0.03 Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum Spectrum

18 Diffusion of gold, tin and copper upon soldering

19 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.