Megumu Nagasawa

The resin molded chip size package (MCSP)

The resin molded chip size package (MCSP), consisting of a polyimide/Cu film carrier with metal bumps, has been developed. The CSP having area-array type electrodes connected with the printed circuit board has been developed by many semiconductor companies. We have developed a resin molded CSP. The encapsulant used for this application has also been developed; it is unlike the conventional liquid type or transfer mold type. The molding method is also new and has been indigenously developed. Two new molding methods were designed: 1) the resin-mold and the connection between the semiconductor-chip and the carrier tape with the metal bumps were simultaneously carried out using the newly developed thermo-adhesive polyimide coated on the carrier tape before the connection; 2) this approach involved laminating the sheet on the semiconductor-chip with the new polyimide adhesive. The encapsulation and the reliability of MCSP were investigated and found to be excellent (resistance to corrosion, heat and stress), equal or superior to that of the conventional surface-mounted devices.

Inner lead bonding for a resin molded chip size package

The present study investigated methods for bonding between semiconductor bonding pads and the metal bumps of a film carrier developed for use in chip-size packages (CSP). The structure of the film carrier is that of a copper circuit bearing a layer of insulating polyimide (PI) on both sides and connecting on one side with the exposed bumps, which in turn connect with the bonding pads. The bumps either have a copper core with a gold surface, or are all gold. In the first stage of the experiment, in which basic data were gathered, the ability of the bumps to bond via gang-bonding with the aluminum of the silicon chip was tested, using bumps with gold-plating of different thicknesses to give exposed heights of 10, 30 and 50 /spl mu/m. Bump height is a decisive factor in the peeling strength of the bonding site; satisfactory results were not achieved with low bumps of 10 /spl mu/m height. In the second stage, a method was sought which would help minimize production cost by ensuring successful bonding even with bumps of only 10 /spl mu/m height. The three following methods were tested and found effective: (1) inserting a convex frame immediately beneath the film carrier on the side opposite the bumps; (2) using a film carrier containing a layer of thermoplastic material immediately beneath the bumps; and (3) undertaking scrubbing during the initial bonding phase.