PURPOSE: To increase the connection strength between a heat radiation board and a threaded part and enhance thermal diffusion properties by forming a threaded hole on a radiation board and screwing a fins mounting stud into the threaded hole.

CONSTITUTION: A threaded hole 11 is formed on a radiation board 1. The threaded hole 11 is penetrated from the top 10 to the bottom 12 of the radiation board. A stud 2 comprises a threaded part 1 and a base 22 and its upper part 211 is screwed into the threaded hole 11 from the bottom 12 of the radiation board 1 so that both may be fixedly threaded. The threaded stud 2 whose base 2 faces the outside of the bottom 12 of the radiation board 12 while an upper part 211 of the threaded part 21 extends upward from the top 10 of the radiation board. Fins 3 comprise a fin main body 30, a leg 31, and a threaded part 32 installed to the leg 31. The leg 31 of the fins 3 is threaded into the stud 2 vertically installed to the radiation board 1. This construction increases the connection strength between the radiation board and the threaded part and enhances the thermal diffusion properties.