Heat dissipation fin structure and cooling structure for electric substrate using the same

A heat dissipation fin structure, comprising:

• a fin base plate having a first surface thermally connected with a heat source;
• and
• a plurality of plate-shaped fins provided on a second surface of the fin base plate, wherein
• the fins configure a plurality of flow passages through which cooling air that enters from an inlet passes when the cooling air flows in a flow direction toward an outlet,
• an upstream end portion of at least one of the fins on an inlet side of the at least one of the fins is arranged in an intermediate part of a first flow passage that is formed between a pair of the fins that are adjacent to the at least one of the fins,
• the first flow passage is divided by the at least one of the fins into two or more flow passages in a width direction of the first flow passage,
• an interval in the width direction between the pair of fins is wider on an outlet side of the first flow passage than on an inlet side of the first flow passage, and
• a sectional area of the first flow passage immediately upstream of the upstream end portion of the at least one fin is the same as a sum of sectional areas of the two or more flow passages immediately downstream of the upstream end portion of the at least one fin, wherein
• a projecting portion is formed on the second surface of the fin base plate at a position inside the first flow passage, and
• the interval in the width direction between the pair of fins that forms the first flow passage increases simultaneously with an increase in a projecting amount of an end portion of the projecting portion from the fin base plate along a section of the first flow passage as the section extends in the flow direction of the cooling air.