SMTA International Conference Proceedings

Low Temperature Alloy Development For Electronics Assembly – Part II

Authors: Morgana Ribas, Ph.D., Sujatha Chegudi, Anil Kumar, Sutapa Mukherjee, Siuli Sarkar, Ph.D.; Ranjit Pandher, Ph.D., Rahul Raut, and Bawa Singh, Ph.D.
Company: Alpha, an Alent plc Company
Date Published: 10/13/2013   Conference: SMTA International

Abstract: In this paper, we present details of a very systematic study undertaken for the development of low temperature, leadfree eutectic alloy. Approaches used in alloy development, test methodologies and results are discussed here. Alloy properties targeted for improvements included: Strength, ductility, microstructure stability, thermal cycling and drop shock resistance. At the same time, desirable attributes such as alloy spread and melting temperature are maintained close to the eutectic Sn-Bi.

This paper summarizes basic alloy properties, including mechanical, thermal and electrical properties, and paste attributes of a set of new Sn-Bi-X alloys, in which X is a micro-additive. Further, comprehensive reliability studies were undertaken for these new low temperature alloys. Thermal Cycling was performed from -40°C to 80°C with a 30 minute dwell time. Drop Shock studies were also under taken as per the JEDEC JESD22-B111 standard. Improvements obtained are compared to standard Sn-Bi systems and discussed here. Overall, Sn-Bi-X alloys present significant enhancements in metallurgical properties, soldering properties for SMT assembly, and in thermal and mechanical reliability

Key Words: 

Lead-free, solder alloy, low-temperature alloy, solder joint strength, thermal cycling, reliability.

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