Pulsed laser beam machining method and apparatus for machining a wiring board at multiple locations

Abstract

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 μs and with energy density of about 20 J/cm 2 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.

1 - 22 . (canceled)  
   
   
       23 . A laser beam machining method, for performing machining operations on a wiring board made of a composite material of organic and inorganic materials by use of a laser beam, the method comprising the step of: 
 at a time of pulse irradiation with the laser beam while sequentially positioning a spot of the laser beam at target positions on the wiring board in synchronization with a pulse frequency of the laser beam, providing a time interval of 15 ms or more between successive pulsed laser beams, having a pulse frequency of 67 Hz or more and a beam irradiation time ranging from 10 to 200 μs, for irradiation of the respective target position irrespective of the pulse frequency by irradiating another target position with a pulsed laser beam outputted for the time interval therebetween.    
   
   
       24 . A laser beam machining apparatus, for performing machining operations on a wiring board made of a composite material of organic and inorganic materials by use of a laser beam radiated from a laser oscillator, the apparatus comprising; 
 optical means for changing a direction of the laser beam and moving the laser beam on the wiring board while sequentially positioning a spot of the laser beam at target positions on the wiring board, and    control means for synchronous control between a pulse oscillating operation of the laser oscillator and an operation of the optical means, and for control of the optical means such that a time interval is set to 15 ms or more between successive pulsed laser beams, having a pulse frequency of 67 Hz or more and a beam irradiation time ranging from 10 to 200 μs, for irradiation of the target positions irrespective of a pulse frequency of the laser oscillator.