| 摘要 |
PROBLEM TO BE SOLVED: To enable simple and efficient formation obtaining an excellent contact bump shape, by forming trenches for preventing a warped board which is caused by forcible insertion of metal balls, on the board surface in the vicinity of the metal balls. SOLUTION: Trenches 23 are formed on the surface of a board 11 which is in the vicinity of metal balls 22. In this case, the trenches 23 are made oval and formed on both sides of the respective metal balls 22, penetrating the board 11. The trenches 23 prevent deformation and warp of the board 11 which are to be caused by forcible insertion of the metal balls 22. Especially when many wiring patterns 12 are arranged and the many metal balls 22 are forcibly inserted, the deformation becomes large, and the whole part of the board 11 warps or waves. Hence since there is possibility that excellent contact condition between the respective metal balls 22 constituting contact bumps and corresponding wiring patterns may not be obtained, the trenches 23 are arranged for preventing the above troubles. Therefore, an excellent contact bump shape and a certain contact state can be obtained. preventing the above troubles. Therefore, an excellent contact bump shape and a certain contact state can be obtained.
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