Plastic ball grid array ruggedization

Abstract

A method and product which provides a thin metal or ceramic plate to the top of a plastic grid array (PGA) as a stiffener to maintain its flatness over temperature during a column attach process, and the columns are used for attachment to circuit boards or other circuit devices. These may be constructed in this manner initially or may be retrofitted plastic ball grid arrays from which the solder balls are removed and, the stiffener is attached to the top, and the solder columns have been added to replace the solder balls. The stiffener is a bonded thin metal or ceramic plate attached to the top of the PGA to maintain its flatness over temperature during the column attach process. An aluminum plate bonded to the top of a PGA results in a significant reduction in warping during a temperature cycle. This allows attachment of solder columns to the PBGA. The high melt solder columns are attached to an area array pattern on the PBGA substrate. This array is typically either a solid or perimeter grid. It is critical that the ends of the solder columns opposite the ends attached to the substrate align precisely with the matching grid of solder pads on the printed wiring board. The purpose of the stiffening plate is to maintain the flatness of the PBGA during the process of attaching the columns to the substrate as well as attaching the component to the printed wiring board such that the columns maintain their alignment over this temperature range.