Patent ID: 7805835

Claim:
A method for selectively processing surface tension of a solder mask layer on a circuit board before bonding a chip, comprising the steps of: forming a plurality of solder pads in a flip-chip area on said circuit board; preparing a solder mask layer on said circuit board to cover said flip-chip area and a non-flip-chip area outside said flip-chip area, said solder mask layer covering said plurality of solder pads in said flip-chip area; using a pressing plate having a saw tooth pattern to press said solder mask layer on said non-flip-chip area to transfer said saw tooth pattern onto said solder mask layer and form a rough surface on said solder mask layer in a part of said non-flip-chip area; removing a portion of said solder mask layer to expose said plurality of solder pads; and forming a plurality of tin balls on the exposed solder pads.