| 摘要 |
PROBLEM TO BE SOLVED: To effectively prevent a printed wiring board from warpage during reflow by making a dummy board thicker than the main board thereby enhancing the strength of the wiring board itself. SOLUTION: A build-up board 1 comprises a main board 2 and a dummy board 3 contiguous to the end thereof. A split line 4 is provided between the main board 2 and the dummy board 3 and a conductor pattern, e.g. lands for mounting a part, is formed on the main board 2. The dummy board 3 is cut off from the main board 2 along the split line 4 after reflow soldering, for example, and the main board 2 is used as a product. In the build-up board 1, the dummy board 3 has a larger number of layers than the main board 2. More specifically, a multilayer reinforcing part 8 sufficient for providing a desired strength of board is formed excessively on the surface of the dummy board 3 as compared with the main board 2. The dummy board 3 is thicker than the main board 2 by the amount corresponding to the multilayer reinforcing part 8. |
