Biasing mold for integrated circuit chip assembly encapsulation

Abstract

This invention provides an improved apparatus and method for encapsulating the solder ball interconnections of an integrated circuit assembly which accommodates the use of high viscosity encapsulating materials and enables flush molding to be accomplished without substantially altering the exposed surface of the integrated circuit chip. In accordance with the preferred embodiment of this invention, an integrated circuit chip assembly including an integrated circuit chip mounted on a chip carrier or directly on a circuit board in a standoff relationship by solder ball connections is provided. A mold is placed over the integrated circuit chip. The mold of one embodiment has a compliant material disposed on the molding surface of the mold cavity. The mold also has at least one inlet hole for dispensing encapsulant into the mold, at least one opening for applying a vacuum to the mold and at least one vent. The mold is placed so that the compliant material is flush against the exposed surface of the integrated circuit chip. External pressure is applied to the mold to seal the mold to the surface of the substrate. A metered volume of encapsulant material is dispensed through the inlet into the space surrounding the integrated circuit chip and the space between the integrated circuit chip and the chip carrier or circuit board while a vacuum is applied to the mold to facilitate flow into the mold and around the solder ball interconnections. After the required amount of encapsulant material is dispensed, the material is cured to form a bond between the integrated circuit chip and the chip carrier or circuit board and reinforce the solder ball connections. In another embodiment of the mold of this invention, a bore hole extends through the mold and into the cavity. The bore hole is fitted with a push pin and a retractable spring support which together serve as a biasing mechanism during the molding process.