Abstract: Because of the influences of such factors as machining tolerance etc., the contact thermal resistance between chip and cold plate can't be controlled effectively. The method of installing a cold plate on the chip surface can't meet the cooling requirements to high power BGA chip. In this paper, a so called "PISTON" thermal conduction module which fully considers these factors is introduced. By thermal performance calculation and test, it is shown that this structure can meet the chip's cooling requirements to sealed avionics.