Characterisation of tin–copper intermetallic growth in electrodeposited tin coatings using electrochemical oxidation techniques

Abstract

In the present investigations electrochemical oxidation has allowed for the removal of tin from coated copper substrates permitting scanning electron microscopy to be employed to assess intermetallic compound distribution and morphology. It was shown that the initial growth of intermetallic compound was not uniform, with its distribution dependent upon the grain structure of the copper substrate, and the grain orientation and distribution within the tin coating. After a period of further nucleation and coarsening, the intermetallic compound forms an almost complete layer along the interface. It is thought this uniform layer of intermetallic compound, formed soon after deposition, may be responsible for this specific electrodeposited tin system having a low whiskering propensity.

Keywords:

• Intermetallic compound
• Tin electroplate
• Copper
• Cu₆Sn₅
• Tin whisker

Acknowledgments

The authors would like to thank the Loughborough University Graduate School Centenary Scholarship, the WHISKERMIT project (funded by the IeMRC/EPSRC) based at Loughborough University for support of this research. Dr Trevor Pearson from MacDermid plc. is acknowledged for the provision of the Tinmac additive solution used throughout these trials.