Patent ID: 7919856

Claim:
A package mounted module comprising: a package board on a topside surface of which a semiconductor chip is mounted; a motherboard onto a topside surface of which an underside surface of the package board is solder-bonded; and a first stiffener disposed on an underside surface of the motherboard in a position to interpose the motherboard between the first stiffener and the package board and fixed to the motherboard with fastening components, wherein the first stiffener has one layer that is farther from the motherboard than an other layer thereof in contact with the underside surface of the motherboard and that has a thermal expansion coefficient larger than that of the other layer, the first stiffener has an area larger than an area of the package board and is fixed to the motherboard, at a plurality of positions with the fastening components, in a region excluding a portion where the first stiffener overlaps the motherboard and outside the package board when the package board, the motherboard and the first stiffener are stacked and viewed, and the first stiffener has a bimetal structure formed of a first member that is the other layer in contact with the underside surface of the motherboard and a second member that is the one layer directly in contact with one surface of the first member farther from the motherboard than the other surface thereof and having a thermal expansion coefficient larger than that of the first member.