FLIP-CHIP ASSEMBLEY WITH THIN UNDERFILL AND THICK SOLDER MASK

摘要

The invention provides a method for attaching a flip chip (210) to an electrical substrate (240) such as a printed wiring board. A bumped flip chip is provided, the flip chip including an active surface and a plurality of connective bumps (220) extending from the active surface, each connective bump including a side region. A thin layer of an underfill material (230) is applied to the active surface of the flip chip and to a portion of the side regions of the connective bumps. The flip chip is positioned on the electrical substrate, the electrical substrate including a thick layer of a solder mask (250) disposed on the electrical substrate. The flip chip is heated to electrically connect the flip chip to the electrical substrate, wherein the underfill material and the solder mask combine to form a stress-relief layer when the flip chip is electrically connected to the electrical substrate.