Patent ID: 7135355

Claim:
A method of forming solder bumps for a flip chip on a wafer or substrate with semiconductor devices, the method comprises: a) using a lift-off process, a thin metal film, comprising a central square UBM layer and two rectangular reflowing enhancement layers at the opposite sides of the central square UBM layer, is deposited with a thickness; b) according to a volume of a solder bump to be formed on the central square UBM layer and the reflowing enhancement layers, designing and preparing a stencil mask with an opening pattern by a design rule; c) placing the stencil mask on the central square UBM layer and the reflowing enhancement layers by matching the opening pattern with the UBM layer and the reflowing enhancement layers, filling soldering paste into the opening pattern of the stencil mask; d) removing the stencil mask; and e) reflowing the soldering paste to form a ball-shaped solder bump under the surface tension of the molten soldering paste with the reflowing enhancement layers.