Electric heating – Metal heating – By arc
Patent
1995-12-06
1998-06-09
Walberg, Teresa J.
Electric heating
Metal heating
By arc
21912172, 21912176, 21912183, B23K 2602
Patent
active
057638535
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a laser processing apparatus and a laser processing method by which a workpiece can be processed in the desired processed positions at high speed, as well as a dam bar processing method using the laser processing apparatus.
BACKGROUND ART
Pulse-like laser beams are utilized as one processing method to perform cutting, punching, welding, etc. in manufacturing processes ranging over a variety of fields including, e.g., mechanical, electronic, and semiconductor apparatus. Arrangements of a conventional laser processing apparatus will briefly be described below.
A conventional laser processing apparatus includes a laser oscillator comprising a laser head, a laser power supply, etc., a processing optical system, an XY-table mounting a workpiece thereon and being movable in a horizontal plane (XY-plane), a controller for controlling the movement of the XY-table and the oscillation of the laser oscillator in an automatic or manual manner, and so on.
In the laser power supply, a supplied AC current is converted into a DC current in accordance with a voltage value commanded from the controller, and is supplied to a capacitor. Electric charges accumulated in the capacitor are then discharged to an excitation lamp of the laser head in accordance with the predetermined on/off timing (pulse width and pulse frequency). In response to the discharge, a pulse-like laser beam is oscillated from the laser head.
The laser head incorporates a beam shutter which is opened and closed to switch the pulse-like laser beam on/off to thereby control irradiation of the laser beam to the workpiece. Specifically, when the workpiece is to be processed, the beam shutter is opened and, when the workpiece is not to be processed, the beam shutter is closed. The time during which the beam shutter is operated to open and close is on the order of 100 to 300 msec.
Let assume the case in which dam bars of an IC package, for example, are removed (cut off) by using the laser processing apparatus described above. Dam bars are positioned to interconnect pins (leads) of a lead frame for use with an IC package, and serves to not only dam a resin applied for integral sealing of the IC package by resin molding, but also reinforce the pins of the lead frame. The dam bars are removed after the integral sealing of the IC package by resin molding. The processing steps of removing the dam bars by utilizing a pulse-like laser beam will be described below in connection with the case that one dam bar in some point has been removed (cut off) and another dam bar in a next point is now removed. toward the next point by the XY-table. (1).
By repeating the above processing steps from (1) to (5), the dam bars in four sides of the IC package are removed successively. At this time, the operation of the XY-table to move and stop and the operation of the beam shutter to open and close are implemented in accordance with programs stored in the controller beforehand. Also, during the above steps, the laser beam is continuously oscillated in the form of pulses at all times, or oscillated in synchronism with the opening of the beam shutter.
Additionally, the prior art relating to a laser processing apparatus or a laser processing method suitable for the above case of removing dam bars is described in, e.g., JP, A, 56-9090 or JP, A, 4-41092. In the method described in the former JP, A, 56-9090, a laser beam is evenly irradiated to a workpiece by oscillating the laser beam in accordance with change in the processing speed (i.e., the moving speed of an XY-table). In the apparatus described in the latter JP, A, 4-41092, the on/off timing and the irradiation timing of a laser beam are controlled in accordance with results of comparison between information about a plurality of processed positions stored beforehand and amounts of movement of an XY-table.
DISCLOSURE OF THE INVENTION
Since dam bars of usual IC packages are dimensioned to have a width of about 0.1 to 0.3 mm and a thickness of about 0.15 mm, each dam bar can suffici
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Miyanagi Naoki
Nagano Yoshinari
Okumura Shinya
Sakurai Shigeyuki
Shimomura Yoshiaki
Hitachi Construction Machinery Co. Ltd.
Mills Gregory L.
Walberg Teresa J.
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