| 摘要 |
PROBLEM TO BE SOLVED: To increase reliability in of interlayer electrical connections. SOLUTION: A metal conductor 14 made of copper is filled in a via hole 13 of a one-face printed wiring board 30, and its front end part is coated with a diffused metal layer 16 composed of tin to a thickness of 10 to 20μm. Adhesives 40 are coated on the entire face of a side of this diffused metal layer 16, and a copper foil 12 is etched on a face on the reverse side to form a conductor circuit 18. The front end of the metal conductor 14 of this one-face printed wiring board 30 is pressed to conductor circuits 51, 52 of a core substrate 50 and the conductor circuit 18 of the one-face printed wiring board 30 on the side of an internal layer to be hot-pressed. The heating temperatures are set to fusing point (230 deg.C) of tin or lower, for example 180 deg.C to 230 deg.C, and a relatively high pressure is made to act. Then, copper atoms are diffused gradually into tin, to form an alloy layer on an interface. |
