PURPOSE: To obtain a circuit module having high reliability capable of placing a large-sized thin semiconductor package by suppressing solder crack due to a thermal stress concentrated at a solder-connected part in a thermal cycle test.
CONSTITUTION: A plurality of leads 2 are extended from the side of a semiconductor package 1. Solder pads 5 are provided on both side surfaces of a printed circuit board 7. The ends of the leads 2 of the package 1 are connected to the pads 5 by solders 3, a plurality of the packages 1 are mounted on both side surfaces of the board 7 to constitute a circuit module. The board 7 has a glass transition temperature of 80-110°C, its linear expansion coefficient and Young's modulus are reduced in a high temperature range of a cycle test exceeding the transition temperature, and a thermal stress in the high temperature range of the thermal cycle test is absorbed by the deformation of the board 7.