Laser processing apparatus and method

Abstract: In a laser processing apparatus wherein laser beams (2a, 2b) are respectively focused and irradiated by focusing devices (6a, 6b) onto work (7) being processed, thereby performing laser processing in processing areas (B) within predetermined ranges on the work (7), an adjustment member (10) is provided for automatically adjusting the interval (C) between the center points of the focusing devices (6a, 6b) in correspondence with the size of the entire processing area (A) on the work (7) being processed.

Description: The present invention relates to a laser processing apparatus and method for using laser beams in laser machining processes such as processes for opening holes in work being processed such as electronic circuit boards. One example of a laser processing apparatus of this type which is similar to that disclosed in EP-A-0884128 is diagrammed in Fig. 4, and configured so that, minute holes are perforated in work being processed such as a board 7 by laser beam irradiation. With this laser processing apparatus, a laser beam 2 is output from a laser oscillator 1, reflected by a reflecting mirror 3a to change its direction, and then branched into two directions by a beam splitting device 9. The branched laser beams 2a and 2b are guided, respectively, by reflecting mirrors 3b and 3c and by reflecting mirrors 3d to 3f toward galvanometers 4 and 5 equipped with galvano-mirrors with axes in the P and Q dimensions, after which the laser beams 2a and 2b have their directions of irradiation changed by the sweep of the galvanometers 4 and 5, are input to f lenses 6a and 6b, respectively, and focused. Then the laser beams 2a and 2b are irradiated and scanned in the X and Y directions in a processing area B within predetermined ranges on the board 7 that is positioned by an XY table 8. The XY table is then moved, and the next processing areas are laser-processed. In laser processing methods that use the laser processing apparatus described above, however, when processing is performed to open holes in the board 7 by the laser beams 2c focussed by the f lenses 6a and 6b, due to the necessity of realizing roundness in the holes, the processing areas B are limited to approximately 50 nun or so in the X and Y dimensions, respectively, by the effective diameters of the f lenses 6a and 6b. The dimensions of the board 7 are such that the sides measure 200 to 500 mm or so, which is roughly the same over the entire processing area A. Accordingly, if the dimensions of the board 7 are 500 nm in the X dimension and 350 mm in the Y dimension, for example, a matrix of 70 processing areas B is necessary in order to process the entire processing area A. The dimensions of the board 7 are various, however, and, if the interval between the two f lenses 6a and 6b is constant, there will be cases where even though processing with one f lens is finished the processing with the other f lens will not be finished. In such cases it is necessary to continue processing with the other f lens for a considerable time, to the detriment of processing efficiency. It is also necessary to implement measures so that the one f lens laser beam is not being irradiated onto the board 7 while processing is in progress with the other f lens, and energy is lost during that time due to the wasted laser irradiation. Thereupon, an object of the present invention is to provide a laser processing apparatus and method that resolves such problems as those described in the foregoing, wherewith changes in the dimensions of the work being processed can be coped with, and laser processing can be performed efficiently and with high productivity. EP-A-0479965 discloses a laser printing apparatus with only a single movable head containing focussing lenses which includes means to provide a constant path length for the laser irrespective of the portion of the movable head. In order to achieve the object stated above, the present invention provides a laser processing apparatus comprising: a laser oscillator for outputting a laser beam; a beam splitting device for branching the laser beam output from the laser oscillator into a plurality of laser beams; a plurality of scanning devices for guiding the branched laser beams to processing positions in areas of a work being processed; a plurality of focusing devices for focusing and irradiating the branched laser beams onto said areas of work being processed, thereby performing laser processing with the branched laser beams in processing areas on said work being processed; and, an XY table for carrying thereon the work being processed and for moving said work relative to said plurality of focusing devices during laser processing to move from one area being processed to the next in succession, respectively; characterised in that the apparatus also includes an adjustment member for automatically adjusting the interval between center points of said plurality of focusing devices in correspondence with size of the entire area to be processed on said work being processed before said work is processed and for maintaining said interval throughout the processing of that said work and light path length adjustment means for adjusting light path lengths so that lengths of light paths from the point where said laser beam is branched by said beam splitting device, through the plurality of scanning devices to the focus points where said laser beams are focused by said plurality of focusing devices are identical. As based on the present invention, when the board or other work being processed is moved relative to the focusing devices and the processing areas are sequentially processed, the points in time when the laser processing in all of the focusing devices is finished are made to coincide by automatically adjusting the interval between the center points of the focusing devices in correspondence with the size of the entire processing area of the work being processed. Hence it is possible to eliminate the wasted work time and wasted laser irradiation resulting from the non-coincidence of laser process finishing times that has been a problem in the prior art, and to perform laser processing efficiently and with high productivity. By providing light path length adjustment member, the non-coincidence in light path length arising in conjunction with adjusting the interval between the center points of the focusing devices can be corrected, and the focused state of the laser beams can be maintained the same, wherefore simultaneous processing can be performed precisely on the work being processed. In order to achieve the object stated above, the present invention also provides a laser processing method wherein: a laser processing method comprising the steps of: outputting a laser beam from a laser oscillator; branching said laser beam into two laser beams; guiding said two laser beams by respective scanning devices onto processing areas on the work to be processed; focusing and irradiating said two laser beams respectively by the two focusing devices, thereby performing laser processing with said two laser beams in two processing areas; and, positioning said work to be processed relative to two focusing devices on an X-Y table; characterised in that as an initial step the two focussing devices are positioned with respect to one another with an interval between their centre points of half the total length in the X direction of the entire area (A) of the work to be processed, in that the light path length is adjusted so that the lengths of the light paths from the point where said laser beam is branched, through the plurality of scanning devices to the focus points where said laser beams are focussed by said plurality of focussing device area identical; in that the relative location of the focussing devices and the length of the light paths are maintained constant through the processing of the entire area (A) of the work is moved during the processing step. As based on the present invention, using two laser beams, the interval between the center points of the two focusing devices can be automatically adjusted, and laser processing can be performed efficiently and with high productivity. A preferred embodiment of the present invention will be hereinafter described with reference to the accompanying drawings, in which: Fig. 1 is a perspective view representing the configuration of a laser processing apparatus used in a laser processing method in an embodiment; Fig. 2 is a simplified diagram for describing the movement when the entire processing area is being laser-processed in the first embodiment; Fig. 3 is a perspective view representing the configuration of a laser processing apparatus used in a laser processing method an second embodiment of the present invention; and Fig. 4 is a perspective view representing the configuration of a laser processing apparatus used in a conventional laser processing method. The embodiments of Fig 1 and 2 are not covered by the claims and are not embodiments of the invention but they are examples of background art which are useful for understanding the invention. A first embodiment is described below with reference to Fig. 1 and Fig. 2. Fig. 1 shows the configuration of a laser processing apparatus used in the laser processing method according to the first embodiment. A laser beam 2 output from a laser oscillator 1 has its direction changed by a reflecting mirror 3a and is then branched into two laser beams 2a and 2b by a beam splitting device 9. The branched laser beams 2a and 2b, respectively, are guided by reflecting mirrors 3b and 3c and reflecting mirrors 3d to 3f and are input to f lenses (focusing devices) 6a and 6b from galvanomirrors 4a and 5a provided in galvanometers (scanning devices) 4 and 5 which make the laser beams 2a and 2b scan in the X and Y axes. After being focused by the f lenses 6a and 6b, the laser beams 2a and 2b are directed to a processing area B within predetermined ranges on a board (work being processed) 7 that is positioned by an XY table 8, and hole opening processing is performed. The laser irradiation units configured by the galvanometers 4 and 5 and the f lenses 6a and 6b are divided into two sets. The laser irradiation unit I comprising the f lens 6a is made stationary, while the laser irradiation unit II comprising the f lens 6b can be adjustably moved for the purpose of positioning. To the laser irradiation unit II is attached a table (adjustment member) 10. The f lens 6b can be moved to the optimal processing position by automatically adjusting the interval C between the center points of the f lenses 6a and 6b in correspondence with the dimensions (entire processing area A) of the board 7. Accordingly, the points in time where laser processing is finished in the two f lenses 6a and 6b can be made to coincide, and the wasted work time and wasted laser irradiation caused by non-coincidence of laser process finishing times can be eliminated. The laser processing method of the first embodiment is described next. First, the table 10 is moved and positioned so that the interval C between the center points in the X dimension of the f lenses 6a and 6b becomes 1/2 of the total length in the X dimension of the entire processing area A on the board 7. If, for example, the length in the X dimension of the entire processing area A on the board 7 is assumed to be 500 mm, then the interval C between the center points in the X dimension of the f lenses 6a and 6b is set to C = 500 mm/2 = 250 mm. Next, the board 7 is positioned to the predetermined position by the XY table 8, and the laser beam 2c is guided to the processing position on the board 7 by the galvano-mirrors 4a and 5a comprised in the galvanometers 4 and 5. The laser beam 2 is focused and directed by the f lenses 6a and 6b, and hole opening processing can be done sequentially, in each of the predetermined ranges of the respective processing areas B and B on the board 7 by the laser irradiating units I and II. The hole opening process using the laser beam 2c described above is described in detail with reference to Fig. 2. In this illustratory embodiment, the entire processing area A is divided into processing areas B in a 4 x 10 40-element matrix. By automatically adjusting the interval C between the center points of the f lenses 6a and 6b of the laser irradiating units I and II, respectively, as indicated by the broken-line arrows in Fig. 2, with the laser irradiating unit I, processing is performed sequentially, starting from 1-1 (point S), moving to 1-2, 1-3, 1-4, 2-4, 2-3, etc., and terminating at 5-4 (point E). With the other laser irradiating unit II, processing is performed, starting from 6-1 (point S'), moving to 6-2, 6-3, 6-4, 7-4, 7-3, etc., and terminating at 10-4 (point E'). By automatically adjusting the interval C between the center points of the f lenses 6a and 6b so that it is 1/2 the overall length of the entire processing area A in the X dimension, as described in the foregoing, any timing wherewith processing cannot be done by either one of the laser irradiating units I or II is eliminated, and processing data are not wasted, wherefore laser processing can be performed efficiently and with high productivity. Fig. 3 shows the configuration of a laser processing apparatus used in a laser processing method according to an embodiment of the present invention. In the first embodiment, there are cases where, in conjunction with adjusting the interval C between the center points by moving the table 10, the light path length of the laser beam 2b of the laser irradiating unit II will be different than the light path length of the laser beam 2a of the laser irradiating unit I. In order to correct this, the configuration is made such in this embodiment that, by moving a table (light path length adjustment member) 11 on which the reflecting mirrors 3e and 3f are carried, the light path length of the laser beam 2b can be automatically adjusted. In Fig. 3, as in the illustratory embodiment according to Fig 1-2, the laser beam 2 output from the laser oscillator 1 is branched into two beams by the beam splitter 9 and guided to two sets of laser irradiating units, I and II, which comprise galvanometers 4 and 5 and f lenses 6a and 6b. The lengths of the light paths for the double-branched laser beams 2a and 2b from the point of branching until they arrive at the focus points (processing points) on the board 7 formed by the f lenses 6a and 6b of the laser irradiating units I and II are varied by the relative motion of the laser irradiating unit II. With this embodiment aspect, however, it becomes possible to adjust those light path lengths by moving a table 11 that carries the reflecting mirrors 3e and 3f. In other words, the laser irradiating unit II can be positioned by adjustably moving the table 11 so that the light path length resulting when the laser beam 2a branched by the beam splitter 9 and directed toward the laser irradiating unit I is reflected by the reflecting mirrors 3b and 3c and input to the galvano-mirror 4a, and the light path length resulting when the laser beam 2b branched by the beam splitter 9 passes through the reflecting mirror 3d and is then reflected by the reflecting mirrors 3e and 3f carried on the table 11 and input to the galvano-mirror 4a, become identical distances. When, for example, the pitch of the laser irradiating units I and II is moved by exactly the distance D, the amount of movement in the table 11 becomes D/2 (not shown). Thus, by causing the light path distances from the branching point of the laser beam 2 branched by the beam splitter 9 to the focus points at the laser irradiating units I and II to coincide, the focused state of the branched laser beams 2a and 2b can be kept identical. As a result, laser processing can be performed precisely on the board 7. According to the present invention, as described in the accompanying claims, the interval between focusing means is automatically adjusted in correspondence with the size of the entire processing area on the board or other work being processed, wherefore wasted process time can be eliminated, and such laser processing as hole opening processing can be performed efficiently, precisely, and with high productivity.

Claims: A laser processing apparatus comprising: a laser oscillator (1) for outputting a laser beam (2); a beam splitting device (9) for branching the laser beam (2) output from the laser oscillator into a plurality of laser beams (2a,2b); a plurality of scanning devices (4,5) for guiding the branched laser beams (2a,2b) to processing positions in areas (B) of a work (7) being processed; a plurality of focusing devices (6a,6b) for focusing and irradiating the branched laser beams (2a,2b) onto said areas (B) of work (7) being processed, thereby performing laser processing with the branched laser beams in processing areas (B) on said work (7) being processed; and, an XY table (8) for carrying thereon the work (7) being processed and for moving said work (7) relative to said plurality of focusing devices (6a,6b) during laser processing to move from one area (B) being processed to the next in succession, respectively; characterised in that the apparatus also includes an adjustment member (10) for automatically adjusting the interval between center points of said plurality of focusing devices (6a,6b) in correspondence with size of the entire area (A) to be processed on said work (7) being processed before said work (7) is processed and for maintaining said interval throughout the processing of that said work (7) and light path length adjustment means (11) for adjusting light path lengths so that lengths of light paths (2a, 2b) from the point where said laser beam (2) is branched by said beam splitting device (9), through the plurality of scanning devices (4,5) to the focus points where said laser beams (2a,2b) are focused by said plurality of focusing devices (6a,6b) are identical. A laser processing method comprising the steps of: outputting a laser beam (2) from a laser oscillator (1); branching said laser beam (2) into two laser beams (2a, 2b) ; guiding said two laser beams (2a,2b) by respective scanning devices (4,5) onto processing areas (B) on the work (7) to be processed; focusing and irradiating said two laser beams (2a,2b) respectively by the two focusing devices (6a,6b), thereby performing laser processing with said two laser beams in two processing areas (B); and, positioning said work (7) to be processed relative to two focusing devices (6a,6b) on an X-Y table (8); characterised in that as an initial step the two focussing devices (6a,6b) are positioned with respect to one another with an interval between their centre points of half the total length in the X direction of the entire area (A) of the work (7) to be processed, in that the light path length is adjusted so that the lengths of the light paths (2a,2b) from the point where said laser beam (2) is branched, through the plurality of scanning devices (4,5) to the focus points where said laser beams (2a,2b) are focussed by said plurality of focussing device (6a, 6b) area identical; in that the relative location of the focussing devices (6a,6b) and the length of the light paths (2a,2b) are maintained constant through the processing of the entire area (A) of the work (7) is moved during the processing step. A method according to claim 2, wherein the work (7) to be processed is moved by the X-Y table (8) during laser processing to process sequentially all of the processing areas (B) and so process the entire area (A) of the work (7).

Inventors: KASAI KENJI, MUNEYUKI KEN, NAKAI IZURU, YUKI HARUHIKO, KASAI, KENJI, MUNEYUKI, KEN, NAKAI, IZURU, YUKI, HARUHIKO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 2000
Main classification: B23K26
IPC codes: B23K26, B23K101, H05K3