Patent ID: 9420706
Filing Date: 2016-08-16
CPC Classification: H01B,H05K,Y10T

Claim Text:
1. A multilayer printed wiring board manufactured by a method, the multilayer printed wiring board comprising: a first patterned board, a second patterned board, and a pre-preg between the first and second patterned boards, each one of the first and second patterned boards having a copper layer portion, the pre-preg having a hole filled with conductive paste, wherein the conductive paste comprises: a resin component, which includes 100 parts by weight of an acrylate resin monomer and an epoxy resin pre-polymer; a metal powder, which includes a first and a second metal, which together provide 200 to 2200 parts by weight to the conductive paste; a curing agent, which provides 0.5 to 40 parts by weight to the conductive paste, the curing agent including a phenolic curing agent providing 0.3 to 35 parts by weight to the conductive paste; and a flux which provides 0.3 to 80 parts by weight to the conductive paste; and wherein said first metal has a melting point of less than or equal to 180° C., said first metal being indium or a first alloy of at least two types of metal from a group of metals consisting of tin, lead, bismuth, and indium; wherein said second metal has a melting point of at least 800° C., said second metal consisting of either one or both of: a metal from the group of metals consisting of gold, silver, copper; and a second alloy of at least two types of metals from the group of metals consisting of gold, silver, copper; and wherein the method of manufacturing comprises: forming the hole through the pre-preg by drilling by laser beam machining, filling the hole with said conductive paste, arranging the copper layer portion of the first patterned board at one side of the pre-preg into contact with the conductive paste and pressing the first patterned board relative to the pre-preg, arranging the copper layer portion of the second patterned board at an other side of the pre-preg into contact with the conductive paste and pressing the second patterned board relative to the pre-preg, and wherein in the conductive paste at least a surface layer of the first metal powder is melted whereby the first and second metals are alloyed, the pre-preg has a ratio of A divided by B of at least 10 before being subjected to preheating, where A is a storage modulus at an inflection point where the storage modulus changes from increasing to decreasing and B is a storage modulus at an inflection point where the storage modulus changes from decreasing to increasing in a temperature profile rising from 60° C. to 200° C., and preheating the pre-preg before the drilling to reduce the ratio of A divided by B to below 10.