Laser processing apparatus for performing desired processing on a workpiece

A laser processing apparatus comprising:

• a chuck table having a holding surface defined by an X-axis direction and a Y-axis direction and configured to hold a workpiece;
• a laser beam irradiating unit configured to irradiate the workpiece held on the chuck table with a pulsed laser beam;
• and
• a controller,
• the laser beam irradiating unit including
• a laser oscillator configured to emit the pulsed laser beam, and
• a condenser configured to condense the pulsed laser beam emitted by the laser oscillator onto the workpiece held on the chuck table,
• the controller including
• a processing trajectory storage section configured to store X-coordinates and Y-coordinates of processing trajectories to be formed on the workpiece held on the chuck table,
• a thickness storage section configured to store a thickness of the workpiece,
• a limit processing depth storage section configured to store a spot diameter of the pulsed laser beam and a limit value of a processing depth,
• a pass number storage section configured to store a predetermined number of passes of the pulsed laser beam reaching the limit value of the processing depth,
• an overlap rate storage section configured to store an overlap rate of spots,
• a selecting section configured to select a product region and a non-product region,
• a processing width calculating section configured to calculate a processing width by multiplying, by the spot diameter, a value obtained by dividing the thickness stored in the thickness storage section by the limit value stored in the limit processing depth storage section, and
• a pass number calculating section configured to calculate a calculated number of passes of the pulsed laser beam to be applied to a section in the processing width by multiplying the value obtained by dividing the thickness stored in the thickness storage section by the limit value stored in the limit processing depth storage section by the predetermined number of passes stored in the pass number storage section, and multiplying a result of the multiplication by a calculated number of spots determined from the spot diameter of the pulsed laser beam, the overlap rate of the spots, the overlap rate being stored in the overlap rate storage section, and the processing width calculated by the processing width calculating section, and
• wherein the controller is configured to perform desired processing on the workpiece held on the chuck table by irradiating the processing width calculated by the processing width calculating section in the non-product region selected by the selecting section on a basis of the X-coordinates and the Y-coordinates stored in the processing trajectory storage section with the pulsed laser beam in the calculated number of passes calculated by the pass number calculating section.