Patent ID: 7394663

Claim:
An electronic component built-in module, comprising: a pair of opposed circuit substrates, in each of which a wiring pattern is formed on an insulating base material containing a resin; an insulating layer that is placed between the pair of circuit substrates and contains an inorganic filler and a resin composition containing a thermosetting resin; at least one electronic component that is embedded in the insulating layer; and an inner via that is provided in the insulating layer so as to make an electrical connection between wiring patterns provided on different circuit substrates, wherein a glass transition temperature Tg1 of the resin composition contained in the insulating layer and a glass transition temperature Tg2 of the resin of the insulating base material included in each of the circuit substrates satisfy a relationship Tg1>Tg2, wherein a difference between the glass transition temperature Tg1 and the glass transition temperature Tg2 is at least 10° C., and wherein a rate of increase in amount of thermal expansion in a thickness direction of the insulating layer at a temperature from Tg2 to Tg1 is smaller than a rate of increase in amount of thermal expansion in a thickness direction of the insulating layer at a temperature higher than Tg1.