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Grain Growth As a Method of Improving Life of Pb-5wt%sn Solder

IP.com Disclosure Number: IPCOM000062005D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Agarwala, BN: AUTHOR

Abstract

It is well known that at temperatures below half of the melting point of a metal or an alloy, atoms diffuse much faster along grain boundaries compared to the diffusion via lattice. Retarding grain boundary diffusion can potentially improve the reliability of Pb-5Wt%Sn solder joints. This may be accomplished by a reduction of the available grain boundary paths for atom transport.

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Grain Growth As a Method of Improving Life of Pb-5wt%sn Solder

It is well known that at temperatures below half of the melting point of a metal or an alloy, atoms diffuse much faster along grain boundaries compared to the diffusion via lattice. Retarding grain boundary diffusion can potentially improve the reliability of Pb-5Wt%Sn solder joints. This may be accomplished by a reduction of the available grain boundary paths for atom transport.

The number of grain boundary paths can be reduced by allowing the grains to grow large during annealing at an appropria temperature range. The annealing should be carried out at temperatures above 100OEC, since for Pb- 5Wt%Sn alloy a complete solubility for Sn occurs at 100OEC. For temperatures below 100OEC, the grain growth rate would be slow because of low diffusivity and low grain boundary mobility in the presence of beta phase precipitates at grain boundaries. For the reliability improvement of the solder joints, the annealing should be carried ou the temperature range of 100-300OEC for a few hours.

Disclosed anonymously.

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