| 摘要 |
PROBLEM TO BE SOLVED: To prevent fatigue failure of solder from to stresses that occur in a bump due to the difference between thermal expansion coefficients of a board and a semiconductor element in a board structure where the semiconductor element is connected via the solder bump 2. SOLUTION: The semiconductor element 1 is mounted on the board 3 via the solder bump 2. An opening part 4 is provided at a position right under the semiconductor element 1 on the substrate 3. Thermal expansion quantity of the substrate 3 can be restrained by this opening part 4, and thus stress to the solder bump 2 can be made small. The opening part 4 may be a circular, oval, or rectangular shaped hole, and one or more holes can also be provided. Furthermore, the opening part 4 can be provided by using the same step as other step of forming a through-hole in the substrate 3.
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