SMTA International Conference Proceedings

Novel Mid-Temperature Alloy for Enabling Solder Processing Temperature Hierarchy in SMT Assembly

Authors: Sathish Kumar, Nicholas Herrick, Ranjit Pandher, Morgana Ribas, Amit Patel, Gyan Dutt, Ravi Bhatkal
Company: Alpha Assembly Solutions, a MacDermid Performance Solutions Business
Date Published: 9/17/2017   Conference: SMTA International

Abstract: Establishing a solder processing temperature hierarchy with traditional tin/silver/copper (SAC) as the level 1 alloy has been a major challenge in SMT applications. The lower temperature options have been plagued with low operating temperature window (too low melting temperature) and poor mechanical strength of the material.

In this study we present process and reliability data for a new off-eutectic alloy with melting point range (192- 203°C). This alloy has the potential to fill a key gap in the alloy choices for Level 2 applications for LED, computer, server, and telecommunications applications. This solder alloy, being significantly different from the conventional lead-free solders, necessitates a completely different flux chemistry. Solder material properties and the solder paste processing through SMT assembly is discussed in detail. The alloy reliability (drop-shock and thermal cycling) was benchmarked against traditional Pb-free solders currently in the market.

Apart from traditional SMT assembly, alloy functional performance in LED applications was also investigated. Detailed results of thermo-mechanical reliability tests of the solder as well as the impact of flux chemistry on the LED performance over time are presented.

Key Words: 

Pb-free Solders, Solder Hierarchy, LED, Die attach, SMT.

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