Patent ID: 7151228

Claim:
A multilayer printed wiring board comprising: a plurality of laminating double-sided circuit boards; and a plurality of sheets of prepreg for interlayer connection, said plurality of sheets and said plurality of laminating double-sided circuit boards alternately located one on another to form a laminated structure, wherein each of the double-sided circuit boards comprises: an insulated substrate 50 to 100 μm in thickness comprising a via-hole 30 to 250 μm in diameter filled with a via-hole conductor, the substrate having two sides, each side comprising a circuit, one of said circuits comprising a metal layer comprising a first pad therein having a through-hole and filled with electro-conductive material, and the other of said circuits comprising a metal layer having a thickness ranging from 5 to 18 μm and having therein a second pad not having a through-hole, wherein: said via-hole conductor comprises metal applied by electrolytic plating that fills said through-hole; said circuits on both sides of said insulated substrate are connected by the via-hole conductor, the first pad on one of said laminating double-sided circuit boards and the second pad on another one of said laminating double-sided circuit boards are connected by one of said sheets of prepreg for interlayer connection, the sheet of prepreg for interlayer connection comprises a through-hole filled with electro-conductive material, and said first and second pads are on either side of the through-hole and are electrically connected with one another by the electro-conductive material in the through-holes, said through-hole in each of said sheets of prepreg has a diameter larger than that of a via-hole in each of said laminating double-sided circuit boards, and the diameter of said through-hole ranges from 50 to 500 μm.