| 摘要 |
PROBLEM TO BE SOLVED: To make unnecessary any throuh hole for drawing out a wiring and any BVH in a printed wiring board, by removing the insulators present on its pads and forming therein recessed portions to expose to the external its pads, and by connecting directly solder balls or pins with its pads via the recessed portions. SOLUTION: Pads 12A, 12B, 12C (having the same sized circular shape) of a printed wiring board 10 are arranged in the form of a grid at an equal pitch. Then, to the shallow-inner-layer pad 12B and the deep-inner-layer pad 12C, through a mechanical counterboring by a milling or through a thermal-vaporization counterboring by a laser, respective recessed portions 14B, 14C are formed to expose the external inner- layer pads 12B, 12C. Hereupon, after making the recessed portions 14B, 14C cylindrical recessed portions having the same diameter value, the diameter value is selected to be larger than the maximum diameter value of the solder balls provided in ordinary BGA packages. After applying cream solders to the pads 12A, 12B, 12C, a BGA package is so mounted on the printed wiring board 10 that the heads of its solder balls are contacted directly with the correspondent pads 12A, 12B, 12C to solder the BGA package to the board 10 by their heatings through a reflow, etc. |
