Method for calculating thermal resistance of heat radiating route from surface packaging type element

Abstract

Abstract PURPOSE:To recognize an exact heat radiation state by covering the case of a surface packaging type element with a heat insulating cover having a known thermal resistance, measuring the temps. at prescribed points and calculating the thermal resistances of respective heat radiating circuits in the absent state of the heat insulating cover. CONSTITUTION:The heat radiation circuits are modeled and the 1st heat radiating route L1 and the 2nd heat radiating route L2 are considered. The thermal resistance between a junction 5 and a case surface 3a is designated an Rth1, the thermal resistance between the surface 3a and air 6 as Rth2 and the thermal resistance from the junction 5 to the air 6 through a printed circuit board 4 as Rth3. The model in which the surface packaging element is covered by the heat insulating cover 10 having the known thermal resistance Rth2' is then considered. The temp. Tj at the junction 5, the surface temp. Tc of the case 3 and the ambient temp. Ta of the case 3 in the absent state of the cover 10 are measured and thereafter, the cover 10 is put on the element and the temps. Tj', Tc', Ta' are measured. The thermal resistances Rth1, Rth2, Rth3 are then calculated. The heat radiation state from the element 2 is, therefore, exactly recognized and the reliability in the design and production is improved.

Inventors

• 👤 Yukio Sato

Bibliographic Details