Thermal conductance at Sn-0.5mass%Al solder alloy/substrate interface as a factor for tailoring cellular/dendritic growth

Author(s)

Oliveira, Ricardo ; Cruz, Clarissa ; Barros, Andre ; Bertelli, Felipe ; Spinelli, Jose Eduardo ; Garcia, Amauri ; Cheung, Noe

• Document type: Journal article
• Source: JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY; v. 147, n. 8, p. 14-pg., 2021-06-20.

Abstract

The use of Al for replacing high-cost alloying metals, like Ag, Bi, and Cu, as the second major element in Sn-based alloys, arises as a promising alternative for the development of low-cost Pb-free solder alloys. To date, however, the interfacial characteristics of Sn-Al solder joints in electronic substrates remain barely explored. Thus, the present study focuses on an understanding of the mechanisms affecting the heat transfer efficiency between a Sn-Al eutectic alloy and two types of substrates, establishing correlations with the microstructure evolution. Results of solidification experiments coupled with mathematical modeling demonstrate an interfacial thermal conductance between the Ni substrate and the Sn-0.5mass%Al alloy higher than that observed for the Sn-Al/Cu couple. Furthermore, Al-rich intermetallics are shown to occur at the interfacial reaction layers for both tested conditions. While dendritic and dendritic/cellular morphologies predominate in the solidification of the Sn-Al eutectic alloy in a Cu substrate, the better heat extraction through the Ni substrate induces the growth of refined high-cooling rate cells. Then, growth laws relating the length scale of the Sn-matrix, represented by cellular or primary dendritic spacings, to solidification thermal parameters such as cooling rate and growth rate are proposed. (AU)

• FAPESP's process: 17/15158-0 - Characterization of microstructure and properties in the evaluation of alloys for thermal interface contact
• Grantee: Amauri Garcia
• Support Opportunities: Regular Research Grants