PURPOSE: To enable to maintain the small temperature difference necessary for transmission of generated heat stream flux at all times as well as to enable to maintain a heating element at low temperature at all times by a method wherein two or more types of microscopic surface structures having different ebullition heat transfer properties are provided respectively on the regions having different surfaces of a pole-like protrusion attached to the heating element.
CONSTITUTION: A pole-like protrusion 10 is attached to the integrated circuit chip 2 mounted on a wiring substrate 1, and the assembly consisting of the chips and the protrusion is dipped into a non-conductive liquid. On the surface of the protrusion 10, a fin 11 is provided on the region located in the vicinity of the base of the protrusion, and a porous face structure 12, consisting of under-surface hollows 13 and 15 and a number of apertures 14 which link the hollows and the outside regions, is provided on the region located in the vicinity of the tip of the protrusion. As the above-mentioned different surface structures are provided on the regions adjoining each other, the temperature of the heating element is not raised by the operation of the fin surface even when the heat stream flux on the surface of the protrusion exceeds the burn-out heat stream flux of the porous-face structure, and the temperature of the heating element can be suppressed more easily than when a fin surface only is provided by the function of the porous face structure.
NAKAJIMA TADAKATSU
HIRASAWA SHIGEKI
