Method of encapsulating a substrate-based package assembly without causing mold flash

A method for encapsulating a substrate-based package assembly including a substrate having a front surface and a back surface, at least one semiconductor chip mounted over the front surface of the substrate, and an electrically-insulative layer formed over the back surface of the substrate, the method comprising the steps of:

• (1) preparing a molding tool having a predefined cavity;
• (2) forming a stepped cutaway portion along the edge of the electrically-insulative layer, which is dimensioned to a predetermined height and a predetermined width;
• (3) fixing the substrate-based package assembly in the cavity of the molding tool, with the stepped cutaway portion defining a constricted flow passage between the substrate and the solid part of the molding tool;
• and
• (4) injecting an encapsulation material into the cavity of the molding tool for the purpose of molding an encapsulation body for encapsulating the substrate-based package assembly, wherein the flow of the encapsulation material within the constricted flow passage is retarded in speed and increased in viscosity.

A method for encapsulating a substrate-based package assembly including a substrate having a front surface and a back surface, an electrically-insulative layer formed over the front surface of the substrate, and at least one semiconductor chip mounted over the electrically-insulative layer, the method comprising the steps of:

• (1) preparing a molding tool having a predefined cavity;
• (2) forming a grooved cutaway portion in the electrically-insulative layer along a seam line between the electrically-insulative layer and the solid pan of the molding tool that would exist between the electrically-insulative layer and the solid part of rim molding tool when the substrate-based package assembly is fixed in position in the molding tool, the grooved cutaway portion being dimensioned to a predetermined height and a predetermined width;
• (3) fixing the substrate-based package assembly in the cavity of the molding tool, with the grooved cutaway portion defining a constricted flow passage between the substrate and the solid part of the molding tool;
• and
• (4) injecting an encapsulation material into the cavity of the molding tool for the purpose of molding an encapsulation body for encapsulating the substrate-based package assembly, wherein the flow of the encapsulation material within the constricted flow passage is retarded in speed and increased in viscosity.