The plate thickness of the fin plates is preferably 0.3 mm or more. Because the stiffness of the fin plates is higher in this case, deformation, tilt, and the like of the fin plates during assembly or the like of the heat sink can be reliably avoided. On the other hand, to improve productivity, the plate thickness of the fin plates is preferably 1.5 mm or less. If the plate thickness of the fin plates is greater than 1.5 mm, then manufacture by press working will become difficult, and consequently there will be a risk that the productivity of the manufacturing process for the fin plates will decrease.

The plate width of the fin plates is not particularly limited and can be set appropriately in accordance with the design or particular application of the heat exchanger. If the heat sink is housed inside the jacket of the heat exchanger, then it is preferable that the fin plates are configured such that both end surfaces in the plate-width direction respectively make contact with the opposite inner-wall surfaces of the jacket. In this case, heat from the heat generating element mounted on the heat-generating-element mounting surface can be transmitted to every fin plate with good efficiency. As a result, the cooling performance of the heat exchanger can be further improved.

As was noted above, the degree of planarity (flatness) of the individual end surfaces in the plate-width direction is preferably 0.2 mm or less. In this case, both end surfaces (in the plate-width direction) of each fin plate can be easily brazed to the respective inner-wall surfaces of the jacket, and consequently heat from the heat generating element mounted on the heat-generating-element mounting surface can be transmitted to every fin plate with good efficiency. As a result, the cooling performance of the heat exchanger can be further improved.