Method for making multi-layer circuit boards
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United States of America Patent
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Jan 19, 1999
Issued Date -
N/A
app pub date -
Sep 6, 1995
filing date -
Jul 19, 1991
priority date (Note) -
Expired
status (Latency Note)
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Abstract
The present invention relates to a bond enhancement process for promoting strong, stable adhesive bonds between surfaces of copper foil and adjacent resin impregnated substrates or superimposed metallic sublayers. According to the process of the invention, a black oxide-coated copper surface is treated with an aqueous reducing solution containing sodium metabisulfite and sodium sulfide to convert the black oxide coating to a roughened metallic copper coating. The roughened metallic copper-coated surface is then passivated and laminated to a resin impregnated substrate. The bond enhancement process is especially useful in multilayer printed circuit fabrication and in the treatment of copper circuit lines and areas which are disconnected from each other, that is, which do not have electrically conductive continuity. Inner-layer laminates prepared according to the process of the invention are not susceptible to pink-ring formation, exhibit excellent resistance to chemical attack at drilled holes and sheared edges and are stable under thermal and mechanical stresses.
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