METHOD AND APPARATUS FOR APPLYING A PROTECTIVE OVER-COATING TO A BALL-GRID-ARRAY (BGA) STRUCTURE

摘要

A vacuum-application and coating apparatus (27) for applying a protective coating (17) to at least one ball-grid-array assembly is provided. The apparatus comprises an upper plate (29) having at least one injection port (37) forming the upper chamber wall, and a lower plate (31) having at least one vacuum port (35) forming the lower chamber wall of the vacuum-application and coating apparatus when assembled. A compliant layer of material is provided on the chamber-side surface of the upper plate and a sealing mechanism (33) for enabling a vacuum seal is also provided. At least one ball-grid-array assembly is placed on the chamber surface of the lower plate during assembly of the vacuum-application and coating apparatus, which forms a vacuum chamber. The ball-grid-array assemblies held in the chamber are protected from receiving any coating on the upper portions of connected solder balls during processing by virtue of intimate contact between the solder balls and the compliant layer of material. In other aspects methods are provided for adding a protective coating (17) to ball-grid-array assemblies (14) and subsequently providing opening for access to the die pads (11). In another aspect a process is provided for completely encapsulating balls (15), then exposing a portion and applying a new grid array.