Thin film laminated multilayer wiring board for multichip modules

A high density multilayer wiring board was developed, using thin film laminating technology. The fundamental features of the fabrication process are laminating the high heat resistant polymer film with an adhesive layer, forming via holes by plasma etching and filling them up by electroless copper metallization. The heat resistant adhesive layer consists of polyimide as the matrix and bismaleimide as the melting constituent. Heat resistance of more than 10 min. at 330°C can be achieved. The via holes of φ=25 μm are formed by a conformal mask method using plasma etching. This paper describes the fundamental technologies for the fabrication process particularly focusing on electroless copper plating