NIST program on Pb-free solder

Carol Handwerker

National Institute of Standards and Technology

Gaithersburg MD

Abstract:

Since 1994, NIST has served major roles in the NCMS Lead-Free Solder Project (1994-1997), the NCMS High Temperature Fatigue Resistant Solder Project (1998-2001), and the NEMI Pb-Free Assembly Project (1999-present) to identify and move Pb-free solders into practice. NIST's contributions have involved research on the critical parameters for selecting a lead-free solder to replace lead-tin eutectic. This includes the thermodynamics of Sn-based systems, melting and solidification behavior of lead-free solders, wetting and solderability, mechanical properties, and failure analysis. In addition, the NEMI Lead-free Task Force and NIST have worked together to respond to data and modeling needs for lead-free solders as identified through a NIST-NEMI-NSF-TMS workshop by:

· Identifying the most important lead-free solder data for the microelectronics community;

· Developing “ a guide to recommended practices” for measuring the mechanical, thermal, electrical and wetting properties of lead-free solders. This document is being distributed to all interested parties through the NEMI and NIST websites and through NIST in hard copy form;

· Gathering into a single database existing physical and mechanical property data that have been developed by researchers around the world[;

· Critically reviewing existing materials property data for the most important alloys for use in finite element analyses; and

· Providing a list of literature references on alloys, processing, reliability, environmental issues, and components for assisting in the implementation of lead-free solders.

NIST research and critical data evaluation for reliability will be discussed.