Preprint Article Version 1 This version is not peer-reviewed

Improved Reliability and Mechanical Performance of Sn58Bi Solder Alloys

Version 1 : Received: 9 April 2019 / Approved: 11 April 2019 / Online: 11 April 2019 (08:52:43 CEST)

How to cite: Ren, G.; Collins, M.N. Improved Reliability and Mechanical Performance of Sn58Bi Solder Alloys. Preprints 2019, 2019040136 (doi: 10.20944/preprints201904.0136.v1). Ren, G.; Collins, M.N. Improved Reliability and Mechanical Performance of Sn58Bi Solder Alloys. Preprints 2019, 2019040136 (doi: 10.20944/preprints201904.0136.v1).

Abstract

Abstract: Microstructural and mechanical properties of the eutectic Sn58Bi and micro-alloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag micro-alloy, the tensile strength was improved and this is attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility is slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag micro-alloyed Sn58Bi solder joints produced utilising a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results reveal that micro-alloyed Sn57.6Bi0.4Ag has a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn-Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure.

Subject Areas

Sn58Bi; Ag; micro-alloy; mechanical; reliability

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