High-Reliability Lead-Free Solders for Automotive Electronics

Abstract

<div class="section abstract"><div class="htmlview paragraph">Requirements for high-reliability lead-free solder alloys in automotive electronics are becoming more challenging as assembly designs require increased powder densities and miniaturization in combination with harsh operating conditions. Thermal cycling performance has been the primary factor for deciding on the suitability of a solder alloy for such applications. Solder joint reliability under thermal and mechanical stresses depends on the solder, packages, PCB, and assembly, including global and local CTE mismatch.</div><div class="htmlview paragraph">Automotive electronic assemblies for critical applications commonly require operational temperatures around 150<sup>o</sup>C, while soldering temperatures need to be as low as possible (<250<sup>o</sup>C). To resolve performance gaps in Sn-Ag-Cu solders for such applications, alloying additives can be used for: i) lowering the melting temperature, ii) improving creep properties, and iii) improving fatigue life. This is exemplified here by comparing a high reliability alloy, commonly known as “Innolot” and SAC305. This work reviews some of the aspects related to such board level accelerated reliability tests and discusses these experimental results in terms of alloy composition, microstructure, and mechanical properties.</div></div>