Patent ID: 8071882

Claim:
A metal base circuit board having an insulating layer and a conductive circuit or metal foil alternately laminated, characterized in that the thickness of the conductive circuit or metal foil is from 5 Î¼m to 450 Î¼m, the insulating layer is made of a cured product of a resin composition comprising an inorganic filler and a thermosetting resin, and the thickness of the insulating layer is from 9 Î¼m to 300 Î¼m, wherein the insulating layer is a cured product of a resin composition comprising from 25 to 60 vol % of the thermosetting resin and the rest being the inorganic filler having a sodium ion concentration of at most 500 ppm and comprising spherical coarse particles having the maximum particle size of at most 75 um and an average particle size of from 5 to 40 Î¼m and spherical fine particles having an average particle size of from 0.3 to 3.0 Î¼m.