| 摘要 |
PURPOSE:To let a solder flow smoothly into a through hole and to prevent the solder in the through hole from dripping after a board has been lifted up by a method wherein the diameter of the through hole, the dimension of width from an opening edge of the through hole to an outer periphery edge of a through-hole land and the dimension of a gap between this outer periphery edge and an edge of a solder resist are set within their prescribed limits respectively. CONSTITUTION:Even when a solder flows into through holes 2a when the lower part of a board 1 has been immersed in a solder bath, the diameter l1 of the through holes is set to 0.6mm or lower when the board is pulled up. Thereby, the solder is held in a state that it has been filled into the through holes 2a by an action of a capillary phenomenon or the like. In addition, a width dimension l2 from an opening edge of the through holes 2a to an outer periphery edge of a through-hole land 3 is set to 0.2mm or higher. Thereby, it is promoted that the solder flows in by a wet state of the solder with reference to the through-hole land 3; the solder can be filled surely into the through holes 2a. In addition, when the dimension of l3 of a gap between an outer periphery edge of the through-hole land 3 and an edge of a solder resist 4 is set to 0.2mm or higher, it is possible to prevent that the solder resist 4 obstructs an inflow of the solder. |
