Patent ID: 6451625
Filing Date: 2002-09-17
Classification: H01L

Abstract:
A method for fabricating a FCBGA package, comprising the steps of:(1) preparing a substrate having a front surface and a back surface; the substrate being formed with a vent hole at a predefined location, the vent hole having an entrance in the front surface and an exit in the back surface of the substrate; (2) forming a plurality of solder-ball pads over the back surface of the substrate; (3) forming a solder mask over the back surface of the substrate; wherein the solder mask is predefined with an array of pad openings to expose the solder-ball pads and a mold-buffering opening aligned to the vent hole; and wherein the mold-buffering opening is dimensioned to be greater in width than the inside diameter of the vent hole; (4) mounting a flip chip over the front surface of the substrate; wherein a flip-chip undergap is left between the flip chip and the substrate; and (5) performing a molding process to form an encapsulation body through the injection of a encapsulation material to encapsulate the flip chip; wherein the vent hole allows the air in the flip-chip undergap to escape to the outside atmosphere, thereby allowing the encapsulation material to infiltrate unresistingly into the flip-chip undergap and form a molded-underfill layer; and wherein as the encapsulation material flows to the exit of the vent hole, the encapsulation material is contained with the solder mask's mold-buffering opening.