Investigators: Carol A. Handwerker, Ursula R. Kattner, William J. Boettinger, John R. Manning, Frank Gayle, Maureen Williams, Leonard Smith and Jonice Adams

Technical Description:

Scientists from NIST working with a broad-based industrial consortium organized through the National Center for Manufacturing Sciences (NCMS) are devising critical tests and providing materials property data to evaluate Pb-free solder alloys with respect to a wide range of manufacturing, performance, and environmental standards.

NIST and NCMS have a multi-year CRADA describing NIST participation in this $8M research and development program, which is supported almost entirely by in-kind contributions from each of its members. In addition to NIST, members include AT&T, Rockwell, Texas Instruments, Ford, GM-Hughes, GM-Delco, Motorola, MicroFab Technologies, United Technologies Research Center, Rensselaer Polytechnic Institute, and Sandia National Laboratories. NIST contributions to this industry-led program have included phase diagram determinations, materials fabrication, and test development for manufacturing performance and mechanical failure assessments.

Technical Objectives:

• Develop critical materials property test methods and data for alloy development.

• Determine range of alloy compositions consistent with manufacturing requirements for multi-element solders through calculation and experimental determination of phase diagrams.

• Identify new alloys for evaluation based on phase diagram and mechanical failure data.

• Fabricate candidate solder alloys for testing by consortium members.

• Develop models of solder wetting and spreading.

Anticipated Outcome:

• New lead-free solder alloys identified that conform to specific manufacturing, performance and environmental standards.

• Lead-free alloys developed by consortium will be available for use by industry in order to avoid environmental problems and their performance established before legislation passed that restricts lead use.

• Guidelines for alloy testing established for development of solder alloys that eliminate expensive and time-consuming manufacturing and reliability trials.

• Recommended test methods will be applied to the design of other classes of lead-free alloys with longer fatigue life.

Accomplishments for FY 1995:

• Measured melting point/freezing ranges in special candidate alloys produced at NIST to identify promising lead-free solders.

• Established validity of linearised equations for melting/freezing ranges for solders containing up to eight elements.

• Identified composition limits in ternary and quaternary alloys that meet melting/freezing range requirements.

• Established quantification method for mechanical failure testing and performed related failure analyses.

• Fabricated solder alloys for assembly of test circuit boards.

Impacts and Technical Highlights:

• An extensive analysis of multicomponent phase diagrams has been performed to determine which Pb-free candidate alloy systems have acceptable melting ranges required for manufacturing.

• Solidification experiments were used to determine non-equilibrium phase formation in the solder during cooling from the liquid state.

• NIST has been asked to provide guidance on test methods and thermodynamic/phase diagram data in a new NCMS consortium for the development of fatigue-resistant solder alloys for high reliability, automotive applications.

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Last modified: Mon Jan 06 09:46:15 1997 Metallurgy Webmeister