| 摘要 |
In a laser beam machining method for a wiring board, a machined portion of the wiring board is irradiated with a pulsed laser beam for a beam irradiation time ranging from about 10 to 200 mus and with energy density of about 20 J/cm<SUP>2 </SUP>or more, thereby machining the wiring board, for example, drilling for a through-hole and a blind via hole, grooving, and cutting for an outside shape. The laser beam operates at a frequency of more than 67 Hz, and the spot of the laser beam is sequentially moved to different drilling positions for each pulse. After all of many drilling positions in the range of a scan vision are irradiated with the laser beam pulse by pulse, or after the elapse of a time of 15 ms or more from irradiation of the first drilling position, the laser spot is returned to the first drilling position. The spot is sequentially moved once again, and the movement is repeated several times. A pause of 15 ms or more is required between pulses directed to the same drilling position to avoid formation of a thick char layer and projection of glass cloth into the hole.
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