This is a hot topic in the last IPC-Expo and many recent
interconnect/packaging conferences.
BUM in Japan and SBU(for sequential build-up) in US are all microvia
technologies which can be accomplished by laser, photovia or plasma etch.
In US, IBM, Continental-Florida and Merix have commercial SBU processes in
production.
For more details on this subject, see PC Fab. magazine(March issue).

Ivan Ho
Ciba Specialty Chemicals
508-779-6060

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