A board housing case, comprising:
- a circuit board hermetically sealed and housed in a case including a base made of a metal and a cover made of a resin or a metal;
- a heat generating component being a surface-mount component mounted on a front surface of the circuit board, the front surface being opposed to an inner surface of the cover;
- and
- a heat transfer base portion formed on an inner surface of the base, the inner surface being opposed to a back surface of the circuit board,
- wherein heat generated from the heat generating component is transferred and radiated to the base via the circuit board and the heat transfer base portion,
- wherein the circuit board includes:
- solder resist films on a front side and a back side, the solder resist films being provided on signal patterns on a front side and a back side;
- a front-surface electroconductive pattern to which a heat transfer block of the heat generating component is to be soldered;
- and
- a back-surface electroconductive pattern connected to the front-surface electroconductive pattern through plated holes so as to transfer heat,
- wherein an insulating sheet having a thickness dimension two or more times larger than a thickness dimension of each of the solder resist films is provided in a gap between the back-surface electroconductive pattern without the solder resist film and the heat transfer base portion,
- wherein a base-side hold portion and a cover-side hold portion are formed at positions along at least a pair of opposed sides of the base and at least a pair of opposed sides of the cover, respectively, and the base-side hold portion and the cover-side hold portion are integrated and fixed by a plurality of fastening elements configured to allow the base-side hold portion and the cover-side hold portion to be brought into pressure contact with and hold the circuit board in a sandwiched manner at positions along at least a pair of opposed sides of the circuit board,
- wherein a height difference dimension G0 between a hold surface of the base-side hold portion and an upper surface of the heat transfer base portion before start of fastening of the base and the cover with the plurality of fastening elements is smaller than a minimum dimension of a thickness dimension T0 of the insulating sheet,
- wherein, when the circuit board is mounted under a state in which the insulating sheet is placed on the upper surface of the heat transfer base portion, a residual gap of T0−G0>0 obtained by subtracting the height difference dimension G0 from the thickness dimension T0 is formed between the back surface of the circuit board and the base-side hold portion,
- wherein a plurality of protruding portions are formed on the inner surface of the cover, and an elastic body to be brought into abutment against the circuit board is provided to a distal end surface of each of the protruding portions,
- wherein, when the cover is placed on an upper surface of the circuit board, the elastic bodies are first brought into abutment against the front surface of the circuit board,
- wherein, when tightening of the fastening elements is subsequently started, compression of the elastic bodies starts, and curvature deformation of the circuit board and the compression of the elastic bodies progress along with an operation of tightening the fastening elements, and
- wherein a height dimension of each of the protruding portions and a thickness dimension of each of the elastic bodies are determined so that, at time of completion of the tightening of the fastening elements, the circuit board is in pressure contact with and sandwiched between the base-side hold portion and the cover-side hold portion, and the elastic bodies remain in a compressed state between the distal end surfaces of the protruding portions and the front surface of the circuit board.