Abstract: A process for forming a multilayer printed wiring board comprising integrally laminating a plurality of insulating circuit boards having circuits formed on insulating substrates and interlaminar insulating layers sandwiched between adjacent insulating circuit boards, and forming via holes for making electrical connection between two or more layers of circuits. Where the difference between the glass transition point of an interlaminar insulating layer and that of the adjoining insulating substrate is not greater than 60.degree. C., proof against exfoliation due to heat history of the board and high reliability of insulation and through-hole connection is achieved. The interlaminar insulating layers desirably are B-staged and have a B-stage resin flow of less than 1%.

Abstract: A multilayer printed wiring board comprising a plurality of interlaminar insulating layers, a plurality of insulating circuit boards having circuits formed on the insulating substrates, and via holes for making electrical connection between two or more layers of circuits, wherein the difference between the glass transition point of an interlaminar insulating layer and that of the adjoining insulating substrate is not greater than 60.degree. C., is proof against exfoliation due to heat history of the board and has high reliability of insulation and through-hole connection.