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Abstract

An improved method of manufacturing fully additive or partly-additive printed wiring boards by electrolessly depositing copper on an insulating substratum and the walls of plated-through holes, wherein the copper deposit has increased resistance to failure due to thermal stress or thermal cycling. The electroless copper plating bath contains a copper compound, ethylenediaminetetraacetic acid as a complexing agent for copper, a reducing agent capable of reducing the copper compound to metallic copper and addition agents selected from inorganic germanium and silicate compounds and combined with a polyethylene glycol. The pH of the electroless copper bath is monitored and maintained between 11.2 and 12.0 to reduce the trace iron codeposited with the copper and improve the resistance to plated-through hole failure in thermal cycling. The addition of vanadium to the electroless copper bath increases the smoothness of the deposited copper and further increases the number of thermal cycles before failure.

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First Claim