SEDL / STP / STP646-EB / STP27314S

Metallic Barriers for Protection of Contacts in Electronic Circuits from Atmospheric Corrosion

Marx, DR
Graduate student, professor, and professor and chairman, Pennsylvania State University, Pa

Bitler, WR
Graduate student, professor, and professor and chairman, Pennsylvania State University, Pa

Pickering, HW
Graduate student, professor, and professor and chairman, Pennsylvania State University, Pa

Pages: 10    Published: Jan 1978

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Abstract

The effectiveness of a variety of 1 to 2-μm-thick barriers in preventing the interdiffusion of copper substrates with gold overplates was investigated. These studies were carried out at both elevated (400 and 500°C) and low temperatures (100 and 175°C). In the high temperature range, of the materials studied, only the cobalt and cobalt-5 weight percent phosphorous were found to be effective barriers. Their effectiveness was comparable to that of the nickel-8 weight percent phosphorous barrier reported by Turn.

The low temperature results were anomalous in that the specimens annealed at 100°C show greater penetration than those annealed at 175°C. It is proposed that this temperature effect is related to the concurrent recrystallization of the gold overplate taking place to a larger degree during the higher temperature diffusion anneal. Thus, at the lower temperature the high density of grain boundaries characteristic of asplated structures is better preserved and leads to a larger overall (grain-boundary) diffusive flux.