Improved adhesive performance through surface treatment

A surface mount tape ball grid array package uses flexible polyimide film that has been circuitized on both sides. To facilitate processing and handling, a picture frame metal stiffener is bonded to the film. The opening in the stiffener defines the location wherein an integrated chip is placed and interconnected to the flexible circuit with thermo-compression bonds or flip-chip solder balls. With the chip backside exposed, heat transfer is enhanced by adhesively bonding a metal heat spreader. This heat spreader is also bonded to the stiffener and appears as a cover plate on the package. The adhesive bond to the cover plate, above the chip, degraded during the high heat exposure of solder reflow and temperature stress testing. Adhesion was improved significantly by oxidizing and hydrating the nickel plated surface of the cover plate. A silane coupler was also applied to the cover plate and further improved adhesion reliability.