| 摘要 |
PROBLEM TO BE SOLVED: To enable forming of vias at the front and back and reduce the connecting pad length by providing outermost layer vias having a tapering angle coaxially to inner layer vias at the opposite side to connecting pads formed on an epoxy film with an inner layer conductor to allow the small- occupied area connecting pad length to be reduced. SOLUTION: A Cu foil epoxy film 5 is photo etched to form connect pads 3A, and Cu foils 1, 2, insulator 4 etc., are formed. For forming via-half-through- holes 6, 6A, 12, 14, a laterally excited atmospheric pressure CO2 laser beam is used, thus enabling very fine via processing giving the advantage to layer interconnection reliability and high-density forming. The process is made until reaching the connecting pads 3A. Roughening to activate is followed by a thick electroless Cu plating to form conductive connection holes (vias) 23, small- occupied-area outermost layer vias 19, 20 coaxial to inner layer vias 10A, 10B and land layer 22. |
