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Via-hole formation process on copper-polyimide sheets was investigated for thin film multilayer wiring substrate. Excimer laser ablation (KrF/wavelength: 248nm) using with conf ormal copper masking method was applied to making small via-holes of 30•`80ƒÊm diameter on polyimide sheets with 25•`100ƒÊm thick. Alcohol washing and oxygen plasma treatment were found to be effective for eliminating residue of laser ablation. The electrical connection of the via-hole by electroless copper plating was confirmed, and the electrical resistance was 2.5•` 0.8mƒ¶ close to theoretical value.
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Watanabe et al. (1994) studied this question.
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