Patent ID: 7642468

Claim:
A multilayer wiring board comprising: a plurality of metal conductor pattern layers formed on base material made of a thermoplastic resin; a first metal containing at least copper, which has a melting point higher than the melting/bonding temperature of the base material; a second metal containing at least tin, which is capable of alloying with the conductor pattern and which has a melting point lower than the melting/bonding temperature of the base material; a binder resin with a melting temperature less than the melting/bonding temperature of the base material; an interlayer electrical connection in a via hole formed between two of the plurality of conductor pattern layers; and an intermediate layer formed on an outer wall of the interlayer electrical connection in the via hole, wherein, the first metal, second metal and binder resin are placed into the via hole formed in the base material, the second metal alloys with the surfaces of the conductor patterns facing the openings of the via and the first metal, and the interlayer electrical connection and an the intermediate layer are formed by applying heat and pressure to the multilayer wiring board while a liquefied second metal and a melted binder resin are phase separated from each other.