JP7098093B2 - Printed circuit board laser processing method and printed circuit board laser processing machine - Google Patents

Description

In the present invention, a blind hole (dead end hole ) connecting a surface copper layer (surface copper layer) and a lower copper layer (hole bottom copper layer) at a desired position on a build-up type printed circuit board (hereinafter, simply referred to as a hole). ) Or laser processing of a printed circuit board in which a double-sided substrate is processed from the front and back to form a through hole that is a through hole for connecting the copper layer on the front surface and the copper layer on the back surface ( copper layer on the back surface). The method and the laser processing machine of the printed circuit board.

The build-up type printed circuit board is configured by alternately laminating a copper layer which is a conductor and an insulating layer (hereinafter, simply referred to as "insulating layer") formed of a resin containing glass fiber or a filler. The copper layer is not only a copper layer having a thickness of 5 to 12 μm that has been surface-treated (called blackening treatment, browning treatment, etc.) for the purpose of enhancing laser absorption, but also a glossy surface that has not been surface-treated. .5 to 2 μm is also used. The thickness of the insulating layer is 20 to 200 μm. When drilling a hole with a carbon dioxide laser, a hole of 40 to 120 μm is used for interlayer connection to connect the copper layer on the surface and the copper layer on the lower layer by plating, and a hole of 40 to 120 μm is used as a reference hole when forming a circuit pattern. Holes of 120 to 250 μm are machined respectively. As for laser processing, there is a demand for processing results that facilitate the plating process, which is a subsequent process.

First, the configuration of a conventional laser machine will be described.
FIG. 9 is a configuration diagram of a conventional laser processing machine.
The laser oscillator 1 outputs a pulsed laser 2. The beam diameter adjusting device 100 arranged between the laser oscillator 1 and the plate 3 is a device for adjusting the energy density of the laser 2, and by changing the outer diameter of the laser 2 output from the laser oscillator 1. Adjust the energy density of the laser 2. That is, the energy of the laser 2 before and after the beam diameter adjusting device 100 does not change. Therefore, since the laser 2 emitted from the beam diameter adjusting device 100 can be regarded as the laser 2 output from the laser oscillator 1, the beam diameter adjusting device 100 and the laser oscillator 1 are collectively referred to as a laser output device 110. The beam diameter adjusting device 100 may not be used.
The plate 3 arranged between the laser output device 110 and the galvano mirror 5a is made of a material (for example, copper) that does not allow the laser 2 to pass through, and has an aperture (a window, in this case a circular shape) at a predetermined position. A plurality of through holes) 4 are formed so as to be selectable. The plate 3 is driven by a drive device (not shown) and positions the axis of the selected aperture 4 coaxially with the axis of the laser 2. The galvano device 5 is composed of a pair of galvano mirrors 5a and 5b, is rotatable around a rotation axis as shown by an arrow in the figure, and can position the reflecting surface at an arbitrary angle. The time required for positioning the galvano mirrors 5a and 5b is about 0.4 ms (2.5 kHz) on average. The fθ lens (condensing lens) 6 is held by a processing head (not shown). The galvano mirrors 5a and 5b and the fθ lens 6 constitute an optical axis positioning device that positions the optical axis of the laser 2 at a desired position on the printed substrate 7. The rotation angles of the galvano mirrors 5a and 5b and the fθ lens 6 The scan area (that is, the processed area) 8 determined by the diameter is about 50 mm × 50 mm in size. The printed circuit board 7 composed of the copper layer 7c, which is a work, and the insulating layer 7z is fixed to the XY table 9. The control device 10 controls the laser oscillator 1, the beam diameter adjusting device 100, the driving device of the plate 3, the galvano mirrors 5a and 5b, and the XY table 9 according to the input control program.

Next, the processing procedure of the conventional laser processing machine will be described.
FIG. 10 is a flowchart showing a processing procedure of a conventional laser processing machine.
The control device 10 reads the machining program, moves the XY table 9, and makes the first scan area 8 face the fθ lens 6 (procedure S10). Then, the aperture 4 corresponding to the hole diameter to be machined first in the scan area 8 is selected, the axis of the selected aperture 4 is positioned coaxially with the axis of the laser 2, and the beam diameter adjusting device 100 is used as necessary. The energy density of the laser 2 is changed (procedure S20). Then, first, holes (hereinafter referred to as windows) are made in all the copper layers 7c at the designated positions in the scan area 8 (procedure S50, procedure S60). That is, the outer diameter of the laser 2 output from the laser output device 110 is shaped by the aperture 4, and the axis of the laser 2 focused by the optical axis positioning device composed of the galvano mirrors 5a and 5b and the fθ lens 6 is positioned. Then, it is incident on the printed circuit board 7. The incident laser 2 evaporates the copper layer 7c to form a window. In this case, in order to prevent deterioration of the insulating layer 7z corresponding to the window, that is, the insulating layer 7z exposed on the surface due to the formation of the window (hereinafter referred to as “window portion insulating layer 7z”), the window is laser 2 It is formed by one irradiation (that is, one pulse irradiation). Further, since the temperature of the window portion insulating layer 7z immediately after the window is formed is high, when the insulating layer 7z is processed after the copper layer 7c is processed, the insulating layer below the copper layer 7c on the outer edge of the window is processed as described later. Gouged to 7z (The outer edge of the window insulating layer 7z expands to the lower part of the copper layer 7c on the outer edge of the window, and the copper layer 7c on the outer edge of the window is overhung with respect to the insulating layer 7z. There is a high possibility that (called) will occur and the inside of the hole will be in the shape of a beer barrel. Therefore, the raw holes remaining in the copper layer 7c in the scan region 8 are first machined.

When the processing of the window is completed, all the insulating layers 7z at the designated positions in the scan area 8, that is, the window portion insulating layer 7z are processed to complete the holes. Here, if the insulating layer 7z is processed with excessive energy, there is a high possibility that gouge occurs or the inside of the hole becomes a beer barrel shape. Therefore, it is decided to process one hole with a plurality of pulses having a pulse width of Pwz, and after irradiating one hole with one pulse of laser 2, the next hole is processed repeatedly to process the insulating layer 7z. To complete each hole. That is, first, the designated number of times N of irradiating the insulating layer 7z with the laser 2 is stored, and the number of times of irradiation i is set to i = 1 (procedure S80, procedure S90). Then, the laser 2 is irradiated one pulse at a time to all the window portion insulating layers 7z in the scan region 8 (procedure S100, procedure S110). Then, when the laser 2 is irradiated to all the window portion insulating layers 7z in the scan area 8, the number of irradiations i is set to i = i + 1, and then the specified number of times N and the number of irradiations i are compared (procedure S120, procedure). S130), if i ≦ N, the process of procedure S100 is performed, and if i> N, the process of procedure S500 is performed. In procedure S500, it is confirmed whether or not there are unprocessed holes having different diameters in the scan area 8, and if there are unprocessed holes, the operation of procedure S20 is performed. If there is no unprocessed hole, it is confirmed whether there is an unprocessed scan area 8 (procedure S510), and if there is an unprocessed scan area 8, the operation of step S10 is performed, and the unprocessed scan area is performed. If there is no 8, processing is finished.

Here, the characteristics of the case where the laser 2 is a carbon dioxide laser will be described.
FIG. 11 is a diagram illustrating the output of the laser oscillator 1, and the upper row is a high frequency pulse RF output activated by the control signal of the laser oscillator 1. The lower row is the output waveform of one pulse of the laser 2, the vertical axis represents the output level, and the horizontal axis represents the time. When the laser oscillator 1 is activated (time T0), a high frequency pulse RF is applied to the laser medium inside the laser oscillator 1 and energy charging is started. Then, when the energy is saturated, the laser 2 is oscillated (time T1). Immediately after oscillation, the output of the laser 2 rises sharply (time Tj), then falls once (time Td), and thereafter, the energy charge and the output emission are balanced, and the output increases. Even if the laser oscillator 1 is stopped, that is, the application of the high frequency pulse RF is stopped (time T2), the energy is continuously output while being attenuated, and becomes 0 at time T3. The pulse energy Ep of one pulse shown by diagonal lines in the figure is the total energy amount during the period from the time T1 which is the duration of one pulse to the time T3 when the output level becomes 0. The width Pw is controlled as a period from time T1 to time T2. That is, for example, when the pulse width Pw is 2 μs, the time T2 is the time when 5 μs has elapsed from the time T0. Here, the period from the time T0 to the time T1 varies depending on the pulse frequency (pulse period) and is about 3 μs ± 0.3 μs. The laser oscillation frequency of the laser oscillator 1 is about 5 kHz (pulse period 200 μs) at the maximum.

Next, a procedure for selecting the diameter of the aperture 4 will be described. Since the laser 2 is projected (condensed) with the aperture diameter reduced by the fθ lens 6, the output distribution of the laser 2 becomes a bell-shaped curve similar to the Gaussian distribution curve having the axis of the laser 2 as the axis of symmetry. Then, as described above, the copper layer 7c is evaporated by the irradiation of the laser 2 to form a window. Therefore, as the diameter of the aperture 4, a desired hole diameter, that is, a diameter having a size such that the window portion becomes the evaporation threshold value of copper is selected. Therefore, if the hole diameters to be machined are different, select apertures with different diameters. In this way, if the diameter of the laser 2 is set according to the diameter of the hole to be machined, it is not necessary to move the height of the fθ lens 6 constituting the optical axis positioning device in the vertical direction, and the machining accuracy is only improved. Not only that, workability is also improved. Several devices have been proposed as replacement devices for the aperture 4. (Patent Document 1)

FIG. 12 is a cross-sectional view of a hole shape processed by laser.
When the density of the glass fiber of the insulating layer is low and most of the laser 2 of the final pulse reflected by the copper layer 7c of the lower layer irradiates the inside of the hole, or when the hole to be formed is deep, the decomposed particles generated in the hole. As a result, the resin on the side surface of the hole is cut out, the diameter of the middle portion in the depth direction of the hole is wider than the diameter of the upper and lower parts, and the side surface of the hole may become a beer barrel-shaped hole as shown in FIG. When the hole becomes a beer barrel shape, as shown in Fig. (B), voids (the hole entrance is blocked during the plating process and the plating solution is trapped in the hole) are likely to occur in the hole during plating in the subsequent process. , Is the main cause of defective printed circuit boards.

Further, as shown in FIG. 3C, when a through hole is formed, if the hole shapes on the front and back surfaces are not uniformly symmetrical or the diameter of the hole intermediate portion varies (about ± 10 μm), one of the plated finished surfaces is formed. The surface of the surface is dented, and the other surface tends to be convex. Therefore, it is necessary to increase the plating thickness and finish the surface flat by a dedicated polishing process.

Further, as shown in FIG. 3D, not only the window portion insulating layer 7z but also the insulating material 7z under the copper layer 7c at the outer edge of the window is scooped out by heat, and a dent 11 is often formed. When the diameter Dk of the recess 11 is larger than the diameter D of the window by 15 μm or more, the copper layer 7c has an overhang of 7.5 um or more with respect to the hole formed in the insulator 7z. Voids are likely to occur. Further, when the diameter Dk of the recess 11 is larger than the diameter D of the window by 15 μm or more, separation (a state where there is an air layer between the copper layer 7c and the insulating layer 7z) occurs between the copper layer 7c and the insulating layer 7z. It may occur, or minute cracks (hereinafter, simply referred to as cracks) may occur in the thickness direction of the insulating layer 7z. If such a crack is generated in one or both of the adjacent holes, a short circuit is generated between the copper layer 7c and the other adjacent copper layer 7c due to plating of the peeled portion or the crack during plating in the subsequent process. Therefore, it is necessary to prevent the occurrence of such cracks. Therefore, although the designated number of times N becomes large , the energy of one pulse is often reduced to improve the quality of the inner surface of the machined hole.

Japanese Unexamined Patent Publication No. 2000-84692

In order to support high-density semiconductors mounted on the printed circuit board 7, laser processing of the printed circuit board is required to process holes having a shape that enables reliable plating. That is,
(1) Make the variation of the hole diameter formed in the window and the insulating layer 7z to ± 5% or less. (2) The hole formed in the insulating layer 7z is a truncated cone whose bottom diameter is 80% or more of the diameter of the top surface. (3) In addition to smoothing the inner surface of the hole by preventing the glass fiber from protruding to the inner surface of the hole.
(4) The gouge of the outer edge of the window insulating layer 7z (overhang of the copper layer 7c) should be 7.5 μm (diameter: window diameter + 15 μm) or less. (5) The copper layer 7c and the insulating layer 7z around the window There should be no peeling or cracks between them (6) Make the hole diameter smaller (7) Make the distance to the adjacent hole about twice the hole diameter (currently 3 to 4 times the hole diameter) ( 8) There is no damage to the bottom of the hole (9) When forming a through hole , it is required to reduce the variation in the diameter of the middle portion of the hole.
As described above, when the insulating layer 7z is processed with excessive energy at one time, gouging occurs or the inside of the hole becomes a beer barrel shape. Therefore, the above (1) to (3) have been solved to some extent by irradiating the laser 2 having a small pulse width Pwz, that is, a small pulse energy, a plurality of times for processing. However, when the pulse width Pwz is set to, for example, 1.5 μs, the time T1 varies by about ± 0.3 μs, so that energy may be insufficient and the diameter of the hole bottom may become smaller. When the pulse width Pwz is increased in order to avoid such a state, there is a high possibility that a gouge occurs or the inside of the hole becomes a beer barrel shape. Further, if the number of irradiations is increased without changing the pulse width Pwz, the time required for positioning the galvano mirrors 5a and 5b as described above is about 0.4 ms (frequency 2.5 kHz) on average, so the number of irradiations is 1. The machining time of one hole increased by 0.4 ms with each increase. Therefore, it has been required to further improve the hole quality and shorten the processing time. Further, improvements have been required for the above (4) to (9).

An object of the present invention is to provide a laser processing method for a printed circuit board and a laser processing machine for a printed circuit board, which can further improve the mounting density of the printed circuit board 7 and efficiently process holes having excellent quality.

In order to solve the above problem, the invention of claim 1 is a method of laser processing a printed substrate, in which the outer shape of a laser output from a laser output device is shaped by an aperture, and the laser is positioned by a galvano device and an Fθ lens. In the laser processing method of a printed substrate in which a hole is formed at a desired position of the printed substrate composed of a copper layer and an insulating layer, a through hole is formed in the copper layer by the laser shaped by the first aperture. After that, the diameter of the laser that contributes to the processing of the insulating layer was processed by the first aperture by using the second aperture having a diameter smaller than that of the first aperture and adjusting the pulse width. It is characterized in that the insulating layer is processed by shaping it to the diameter of the through hole .

Further, according to the second aspect of the present invention, in the method for processing a printed circuit board laser according to the claim, the outer shape of the laser output from the laser output device is shaped by an aperture, and the laser is positioned by a galvano device and an fθ lens. A hole is formed from one surface of the double-sided printed circuit board composed of a copper layer and an insulating layer to a substantially intermediate point in the thickness direction of the substrate, and the thickness direction of the substrate is formed from the other surface opposite to the one surface. In the laser processing method of a printed circuit board in which an X-shaped through hole (through hole) having a small hole diameter in the middle portion is formed by forming a hole up to a substantially intermediate point of the above, the inner surface of the formed through hole is formed. Is characterized by being finished with a laser whose outer shape is shaped by an aperture having a diameter smaller than the hole diameter of the aperture forming the through hole.

Further, the invention of claim 3 includes a laser output device, a plate provided with an aperture, a galvano device, and an fθ lens, and the outer diameter of the laser output from the laser output device is shaped by the aperture. In a laser processing machine for a printed substrate in which the shaped laser is positioned by the galvano device and the fθ lens to form a hole at a desired position on the printed substrate composed of a copper layer and an insulating layer, the diameters are different. A first plate having a plurality of apertures, a positioning device for the first plate that positions the axis of each aperture provided on the first plate coaxially with the axis of the laser, and each axis of the laser. The moving direction of m plates (where m is a positive integer) having n apertures parallel to the axis (where n is a positive integer) and the moving direction of each of the m plates of the laser. M plate positioning means for positioning the processing position for positioning the axis of the aperture provided in each direction perpendicular to the axis and coaxially with the axis of the laser, and the relief position where the plate does not interfere with the laser. The first plate positioning device and the control device for controlling the m plate positioning means are provided, and the first plate is provided with the laser output device and the galvano device in the axial direction of the laser. The m plates are arranged between the first plate in the axial direction of the laser and the galvano device, and the control device is the copper. When processing the layer, the axis of the designated aperture of the first plate is positioned coaxially with the axis of the laser, and all the other m plates are positioned in the retreat position, and the insulating layer is formed. When processing , the aperture used for processing the copper layer (hereinafter referred to as “first aperture”) is n × m with the axis kept coaxial with the axis of the laser. An aperture having a smaller diameter than the aperture used for processing one of the copper layers (hereinafter referred to as "second aperture") is positioned at the processing position, and the outer diameter is determined by the first aperture. It is characterized in that the shaped laser is supplied to the second aperture for processing .

The diameter of the laser 2 that processes the insulating layer 7z is set to a diameter smaller than or equal to the diameter of the laser 2 that processes the copper layer 7c, but the amount of the insulating layer 7z when making one hole can be larger than before, so one It is possible to reduce the number of laser irradiations when making holes. Further, as will be described later, since the pulse width Pw can be increased even at the same energy level, not only stable processing results can be obtained, but also the number of laser irradiations when drilling one hole is reduced. be able to. As a result, the variation in the hole diameter formed in the window and the insulating layer 7z should be ± 5% or less, the diameter of the bottom surface of the hole formed in the insulating layer 7z should be 80% or more of the hole diameter of the surface, and the glass fiber. It is possible to smooth the inner surface of the hole so that the glass does not protrude to the inner surface of the hole, the processing time can be shortened, and the thermal deformation of the printed circuit board is reduced, so that the processing accuracy is improved.

In addition, the gouge of the insulating layer 7z should be 7.5 μm or less, the peeling between the copper layer 7c and the insulating layer 7z around the window and the cracks of the insulating layer 7z should be reduced, and the hole diameter should be further reduced. Since it is possible to make the distance from the adjacent holes about twice the hole diameter, the mounting density of the printed circuit board can be increased.

Further, when forming a through hole , not only the diameter of the hole middle portion varies when the front and back hole shapes are not uniformly symmetrical, but also the hole middle when the front and back hole shapes are uniform symmetrical. Since the variation in the diameter of the portion can be reduced, the quality of the printed circuit board is improved.

Further, by providing a step of finishing the bottom surface of the bottomed hole, the hole diameter becomes uniform, so that the hole diameter can be further reduced.

Further, even when the hole diameter to be machined is small, it is possible to machine a hole having excellent quality by matching the diameter of the hole to be machined in the insulating layer 7z with the window diameter.

It is an whole view of the 1st laser processing machine for carrying out this invention. It is a flowchart which shows the processing procedure of the 1st laser processing machine which concerns on this invention. It is a figure explaining the process of processing using the pulse energy Ep. It is a figure which shows the spatial distribution of a pulse energy Ep. It is sectional drawing of the hole shape processed by a laser. It is an whole view of the 2nd laser processing machine for carrying out this invention. It is a flowchart which shows the processing procedure of the 2nd laser processing machine which concerns on this invention. It is a flowchart which shows the processing procedure of the 2nd hole bottom processing which concerns on this invention. It is a block diagram of the conventional laser processing machine. It is a flowchart which shows the processing procedure of the conventional laser processing machine. It is a figure explaining the output of a laser oscillator. It is sectional drawing of the hole shape processed by a laser.

FIG. 1 is an overall view of a first laser processing machine for carrying out the present invention, and the same reference numerals and the same reference numerals are given to those having the same functions as those of the conventional ones, and detailed description thereof will be omitted.
A large disk-shaped plate 20 made of copper having high reflectance is arranged between the laser output device 110 and the galvano mirror 5a. N apertures 41 to 4n having different diameters are arranged on the circumference of the radius r from the axis of rotation O of the large plate 20 so that holes having a diameter of 40 to 250 μm can be machined. The apertures 41 to 4n are arranged at equal intervals in the circumferential direction. Each axis of the apertures 41 to 4n and the axis O of rotation of the large plate 20 are parallel. The rotation axis O of the large plate 20 is positioned parallel to the axis of the laser 2 and at a position r. The large plate 20 is held by the large plate positioning device 21 so as to be rotatable and positionable in the rotational direction. The large plate positioning device 21 is connected to the control device 10.
Between the large plate 20 and the galvano mirror 5a, a plate 22A having the same number of apertures 4A1 to 4An as the apertures 41 to 4n provided on the large plate 20 is arranged in a direction perpendicular to the axis of the laser 2. The hole diameters of the apertures 4A1 to 4An are smaller than the hole diameters of the corresponding apertures 41 to 4n. The plate 22A is supported by a first linear motion device 23A that moves in a linear direction. The plate 22A is positioned at one moving end of the first linear motion device 23A at a position (operating position) where the axis of any of the apertures 4A1 to 4An is coaxial with the axis of the laser 2. Further, at the other moving end of the first linear motion device 23A, the plate 22A is positioned at a position (retract position) that does not interfere with the laser 2. The first linear motion device 23A is supported by a second linear motion device 24A whose moving direction is perpendicular to the moving direction of the first linear motion device 23A. The second linear motion device 24A positions any of the axes of the apertures 4A1 to 4An at the operating position coaxially with the axis of the laser 2. As a result, any one of the apertures 4A1 to 4An used for machining is positioned at the machining position. That is, the first linear motion device 23A and the second linear motion device 24A constitute a positioning device for apertures 4A1 to 4An. The first linear motion device 23A and the second linear motion device 24A are connected to the control device 10, respectively. Here, the operating speed of the linear motion device 23A is much higher than the operating speed of the large plate positioning device 21.

Next, the operation will be described.
FIG. 2 is a flowchart showing a processing procedure of the first laser processing machine according to the present invention.
The control device 10 reads the machining program, moves the XY table 9, and makes the first scan area 8 face the fθ lens 6 (procedure S10). Further, the aperture of the large plate 20 corresponding to the hole diameter to be machined first in the first scan area 8 (any one of the apertures 41 to 4n; hereinafter, the selected aperture is referred to as the aperture 4s). It is selected, the axis of the aperture is positioned coaxially with the axis of the laser 2, and the energy density of the beam 2 is changed by the beam diameter adjusting device 100 as necessary (procedure S20). Further, when the plate 22A is positioned at the operating position, the axis of the aperture (hereinafter, the selected aperture is referred to as the aperture 4As) used for processing the insulator in the apertures 4A1 to 4An is aligned with the axis of the laser 2. The second linear motion device 24A is operated, and the plate 22A is positioned at the shelter position (procedure S30). Then, a window is machined on all the copper layers 7c at the designated positions in the scan area 8 (procedure S50, procedure S60). That is, the outer diameter of the laser 2 output from the laser output device 110 is shaped by the aperture 4s, and the axis of the laser 2 is positioned and printed by the optical axis positioning device composed of the galvano mirrors 5a and 5b and the fθ lens 6. It is incident on the substrate 7. Here, as in the prior art, the window is formed by one irradiation of the laser 2 (that is, one pulse irradiation), and the copper layer 7c of the remaining holes in the scan region 8 is processed. When the processing of the copper layer 7c is completed, the plate 22A is positioned at the operating position, that is, the axis of the aperture 4As used for insulating material processing is aligned with the axis of the laser 2 (procedure S70), and the window in the scan area 8 is concerned. The partial insulating layer 7z is processed to complete the hole. That is, the designated number of times N of irradiating the laser 2 with the insulating layer 7z is stored, and the number of times of irradiation i is set to i = 1 (procedure S80, procedure S90). Then, the laser 2 is irradiated one pulse at a time to all the window portion insulating layers 7z in the scan region 8 (procedure S100, procedure S110). Then, when the laser 2 is irradiated to all the window portion insulating layers 7z in the scan area 8, the number of irradiations i is set to i = i + 1, and then the specified number of times N and the number of irradiations i are compared (procedure S120, procedure). S130), if i ≦ N, the process of procedure S100 is performed, and if i> N, the process of procedure S500 is performed. In procedure S500, it is confirmed whether or not there are unprocessed holes having different diameters in the scan area 8, and if there are unprocessed holes, the operation of procedure S20 is performed. If there is no unprocessed hole, it is confirmed whether there is an unprocessed scan area 8 (procedure S510), and if there is an unprocessed scan area 8, the operation of step S10 is performed, and the unprocessed scan area is performed. If there is no 8, processing is finished.

Next, in the case of processing a window having the same diameter as described in the prior art, the processing to which the present application is applied will be specifically described.
In the present application, when the diameter of the window is D, the diameter of the hole to be drilled in the insulator is smaller than D, for example, 0.7D. By doing so, the amount of the insulating material to be removed is 49% of the conventional one, that is, about 1/2. Therefore, for example, when the conventional processing is performed with 6 pulses, in the present application, the processing can be performed with 3 pulses of the same energy. .. In this case, since the processing is performed with the same energy as in the case of the conventional 6 pulse, the quality of the processed hole inner surface is not deteriorated.

Further, when the insulating layer 7z is machined, the diameter of the hole to be machined is smaller than the diameter of the window, so that the diameter of the recess 11 hardly expands and no gouge occurs.

The case where the diameter of the hole to be machined in the insulating layer is smaller than the diameter of the window has been described above. However, when the hole to be machined is a small diameter hole of, for example, 80 μm or less, the diameter of the hole to be machined in the insulating layer 7z is set to the window. If the diameter is smaller than the diameter, processing may become difficult. In such a case, the present inventor has noticed that the problem can be solved by adjusting the diameter of the hole to be machined in the insulating layer 7z to the diameter of the window , that is, making the diameter of the hole to be machined in the insulating layer 7z the same as the diameter of the window . .. Further, by finding a means for appropriately determining the processing conditions of the insulating layer 7z, which has been determined by trial and error in the past, it is possible to process holes having excellent quality and to set the processing conditions in a short time. Thought. Therefore, we conducted machining experiments under various conditions and examined what parameters should be used to summarize the data obtained in the experiments. As a result, the energy level k at which the insulator evaporates (hereinafter, simply referred to as Elgi level k), the energy level g at which the glass fibers constituting the insulating layer evaporate (hereinafter, simply referred to as Elgi level g), and the energy level at which copper evaporates. It was found that the machining results can be explained well by organizing the machining data based on j (hereinafter, simply referred to as Elgi level j). Then, it was confirmed that by matching the surface of the insulating layer 7z with the energy level g at which the glass fibers constituting the insulating layer 7z evaporate, almost no gouge occurs and the inside of the hole does not become a beer barrel shape. ..
Needless to say, the diameter of the hole to be machined in the insulating layer 7z may be smaller than the diameter of the window.

Hereinafter, the processing method according to the present invention based on the above findings will be described, including a review of the prior art.
FIG. 3 is a diagram for explaining the process of processing using pulse energy Ep, (a) and (b) are diagrams for explaining the case of the prior art, and (c) is a diagram for explaining the case of the present invention. Here, Dr in FIG. 1 is the focusing diameter of the aperture or aperture 4s of the plate 20 in FIG. 1, Drs is the focusing diameter of the aperture or aperture 4As of the selected plate 22A in FIG. 1, and D is the window diameter. Further, it is assumed that the K surface is the upper surface of the insulating layer 7z in contact with the lower surface of the conductor layer 7c, and the thickness of the insulating layer 7z is h. For ease of understanding, it is assumed that the insulating layer 7z is not affected by heat due to window formation and has a flat surface.

A. Typical processing example in the prior art The energy distribution curve Ldr is a curve showing the spatial distribution of the pulse energy Ep whose outer diameter is shaped by the aperture 4s, and the energy magnitude is in the height direction. E0 is the position of energy level 0.
In the case of an ideal machining example, the pulse width Pw is set so that the diameter of the energy level g of the energy distribution curve Ldr becomes the window diameter D on the K plane.
Here, let Δp be the energy level from the energy level g at the position of the radius Δr from the axis OL of the laser 2 in the energy distribution curve _Ldr . The radius Δr having a radius of _0.4D from the axis OL is referred to as “radius Δrm”, and the energy level Δp at the radius Δrm is referred to as “energy level Δpm”. From the assumption, Δp at Δr = D / 2 is 0.
By the first pulse, the surface layer portion of the insulating layer 7z is processed along the energy distribution curve Ldr, and the surface layer portion of the insulating layer 7z having a radius Δr is processed by Δp. The energy distribution curve Ldr of the second pulse is the same as that of the first pulse, but the surface layer portion of the insulating layer 7z at the position of the radius Δr has already been processed by Δp by the first pulse, so that it was processed by the first pulse. The surface of the insulating layer 7z is processed by Δp, that is, processed by 2Δp. Hereinafter, the machining proceeds by the specified number of pulses, and as the machining progresses, the side surface of the machined hole approaches perpendicular to the bottom surface. Then, the laser 2 is irradiated until the diameter of the hole bottom becomes 0.8D or more, that is, until n × Δpm ≧ h by the laser of the nth pulse. In the case of the figure, since 6Δpm is calculated to be larger than the thickness h (that is, it reaches the surface of the lower copper layer 7c), the processing is completed at the 6th pulse.
In this way, since the side surface of the hole does not exceed the energy level g, no gouge occurs and a hole having excellent quality can be machined, but the machining time becomes long.

B. An example of machining that fails when trying to shorten the machining time of the conventional technique (here, in order to shorten the machining time, the same workpiece as described in A is machined with 3 pulses).
Now, let p be the energy level for processing the insulating layer 7z by h / 3. In order to machine a hole having a hole bottom diameter of 0.8D or more with three pulses, the pulse width is determined so that the energy level of the energy distribution curve Ldr becomes the energy level (g + p) at the radius Δrm. In this case, the energy level at the outer edge of the window diameter D is smaller by the energy level Δq (δ when converted to the processing amount) than the energy level (g + p) at the radius Δrm.
With the above settings, the laser at the first pulse processes the laser to a depth of h / 3 from the surface, a depth of 2/3 h at the second pulse, and a desired bottom diameter at the third pulse at a radius of Δrm. Further, at the outer edge of the window diameter D, the first pulse is from the surface to the depth of (h / 3-δ), the second pulse is to the depth of (2h / 3-2δ), and the third pulse is to (h-3δ). It will be processed. The side surface of the hole from the K plane to (h-3δ) is perpendicular to the bottom surface. However, especially with the first pulse laser, the side surface of the hole is exposed to an energy level much higher than the energy level g, and as a result, the insulating layer 7z becomes overheated and evaporates, and the outer edge of the window is gouged. Also, since the bottom of the hole becomes deeper in the second pulse, it becomes difficult for the evaporated evaporation of the overheated insulating layer to escape from the hole, and the gouge expands, and the laser in the third pulse only makes the gouge even larger. Instead, the middle part of the hole becomes a beer barrel shape.
In this way, it is not possible to machine a hole with excellent quality simply by increasing the machining energy.

C. Processing example in the case of the present application The energy distribution curve Ldrs is a curve showing the spatial distribution of the pulse energy Ep whose outer diameter is shaped by the aperture 4As, and the energy magnitude is in the height direction. In the present application, as the energy distribution curve Ldrs, the pulse width is determined so that the energy level at the window end surface of the K plane is the energy level g and the energy level at the radius Δrm is the energy level (p + g).
With the laser of the first pulse, the laser is processed to a depth of 2/3 h from the surface to a depth of h / 3 at a radius of Δrm, and is processed to a desired bottom diameter at the third pulse. In addition, the side surface of the hole gradually approaches the vertical direction, but the side surface of the hole does not exceed the energy level g, so that no gouge occurs, a hole with excellent quality can be machined, and the machining time is shorter than before. It can be shortened (50% reduction in the case of conventional 6 pulses). The energy level in the radius Δrm is set to the energy level (p + g), but if the energy level is set to be equal to or higher than the energy level (p + g), the side surface of the hole can be made closer to the vertical surface.
Further, although the diameter of the hole to be machined in the insulating layer 7z is set to the window diameter D here, it goes without saying that the diameter of the hole to be machined in the insulating layer 7z can be made smaller than the window diameter D.
In each of the above examples A, B, and C, it was assumed that the insulating layer 7z was not affected by the heat generated by the window formation, but since the surface is actually dented, the number of irradiation pulses is slightly reduced. In many cases.

Next, the thermal effect near the window during processing will be described.
FIG. 4 is a diagram showing the spatial distribution of pulse energy Ep, in which the horizontal axis represents the diameter and the vertical axis represents the magnitude of energy. In the figure, E0 is the energy level of 0, the energy level indicated by Ez is the energy level k at which the insulator evaporates, the energy level indicated by Eg is the energy level g at which the glass fibers constituting the insulating layer evaporates, and AA is indicated. The energy level is the energy level j at which copper evaporates. Further, the energy distribution curve LD shown by the alternate long and short dash line shows the case where the focusing diameter of the aperture 4s is Dr, and the energy distribution curve Ld shown by the solid line shows the case where the focusing diameter of the aperture 4As is Drs. Here, in the energy distribution curve LD, the diameter at the energy level j where copper evaporates is D (that is, the window diameter), and in the energy distribution curve Ld, the diameter at the energy level g where the glass fibers of the insulating layer evaporate is D.
Here, the points where the energy distribution curve LD intersects at the energy level Ez are designated as points C and C, and the points where the energy distribution curve Ld intersects at the energy level Ez are designated as points Q and Q. Further, the position corresponding to the diameter D at the energy level Ez is defined as BB. Then, in the case of the energy distribution curve Ld, energy whose cross section is surrounded by a substantially triangular PBQ when viewed from the insulator is supplied to the outer periphery of the window. On the other hand, suppose that the pulse width Pw of the pulse width Pw (energy distribution curve is the energy distribution curve LD) adopted at the time of copper layer processing is reduced to make the energy distribution curve LDz whose energy distribution curve is the energy level g at the outer periphery of the window. As is clear from the figure, the amount of insulation removed by one pulse is small, so it is necessary to increase the number of pulses. Further, the energy distribution curve LDz intersects with the energy level Ez at points R and R, and the energy surrounded by the substantially triangular PBR whose cross section is larger than the substantially triangular PBQ when viewed from the insulator is supplied to the outer periphery of the window, so that it is affected by heat. Becomes larger. Further, as described with reference to FIG. 3, when the selected energy level is larger than the energy level g, gouging tends to occur and the inside of the hole tends to have a barrel shape.
Further, when the energy level k is adjusted to the diameter D of the window, the generation of the dent 11 can be suppressed, but the glass fiber tends to remain inside the machined hole, which is not practical.

Here, a specific method for confirming the energy level k and the energy level g of the "glass epoxy board" which is often used as a printed circuit board will be described.
The glass epoxy board is a printed circuit board in which a glass fiber cloth is impregnated with epoxy resin and heat-cured to form a plate-like FR4 as a base material, and a copper foil (copper layer) is attached to the base material. , The positional relationship between the glass fiber and the epoxy resin in the glass epoxy substrate is not uniform in the thickness direction. That is, depending on the position of the glass epoxy substrate, there are a place where the glass fiber is close to the surface (the layer of the epoxy resin is thin) and a place where the glass fiber is in the back (the layer of the epoxy resin is thick). Therefore, the copper layer on the surface is removed by etching, the portion where the epoxy resin layer is thick is irradiated with the laser 2, and the hole diameter is measured. The measured hole diameter corresponds to the diameter of the energy level k in this case. Further, the laser 2 is irradiated to a portion where the epoxy resin layer is thin, and the hole diameter is measured. The measured hole diameter corresponds to the diameter of the energy level g in this case. In this case, the diameter of the hole in which the glass fiber is processed into a circle at the outer edge of the hole is measured.
Needless to say, the diameter of the energy level j can be obtained by the window diameter.
The present inventor has, for example, in the case of a printed circuit board having a blackened copper layer having a thickness of 7 μm and a build-up layer having an insulating layer of 60 μm, the energy level g and the energy level j are about g = 5k and j = 11k, respectively. I confirmed that it was. Further, in the case of a printed circuit board having a copper layer having a thickness of 1.5 μm and a build-up layer having an insulating layer of 40 μm without surface treatment, the above cases are also between the energy level k, the energy level g, and the energy level j. It was confirmed that there is almost the same relationship as.

5A and 5B are cross-sectional views of a hole shape processed by a laser. FIG. 5A is a case where the insulating layer 7z is processed by an aperture 4s in which a copper layer 7c is processed as in the prior art, and FIG. 5B is a case where the insulating layer 7z is processed as in the present application. The case where the insulating layer 7z is processed by the aperture 4As whose diameter on the inlet side of the insulating layer 7z of the energy distribution curve is equal to the window diameter is shown.
As a result of the high-temperature decomposition product of the insulator directly under the copper layer 7c being prevented from being dissipated to the copper layer 7c by the energy of the first pulse supplied to the outer periphery of the window, as shown in FIG. In some cases, the recess 11 immediately below the copper layer 7c was enlarged to form a gouge connected to the recess 11. However, in the case of the technique of the present application, as described in FIG. 4, the area of the substantially triangular PBQ is much smaller than that of the substantially triangular PBC, and therefore, as shown in FIG. Does not occur. Further, since almost no gouging occurs, peeling or minute cracks do not occur between the copper layer 7c and the insulating layer 7z. Therefore, even if the diameter of the hole to be machined in the insulating layer is the same as the diameter of the window, the dent 11 generated on the lower side of the copper layer 7c does not become large. Further, since the PP cross section is the energy level g at which the glass fiber evaporates, not only the insulator but also the glass fiber does not remain in the hole.

Hereinafter, for reference, the results of actually processing the printed circuit board 7 having a copper layer having a blackened surface having a thickness of 7 μm and an insulating layer having a thickness of 60 μm will be described.
First, the copper layer 7c was processed by one pulse having a pulse width Pw of 5 μs (the pulse energy in this case is about 6 mJ) using an aperture 4s having a diameter of 3.4 mm to form a window having a diameter of 65 μm. Next, using an aperture 4As having a diameter of 2.6 mm and an energy level g having a diameter of 65 μm at the window edge, the pulse width Pw is 3 μs (the pulse energy in this case is about 2.5 mJ) by three pulses. The insulating layer 7z was processed. As a result, a uniform truncated cone-shaped hole having no dent 11 regardless of the height of the glass fiber density, an insulating layer diameter under the copper layer of about 75 μm (overhang of the copper layer 7c of 5 μm), and a hole bottom diameter of 60 μm or more was formed. It was confirmed that it could be processed.
Further, since the energy applied to the periphery of the window during the 7z processing of the insulating layer was reduced by about 60% as compared with the conventional case, there was almost no peeling or cracking between the copper layer and the insulating layer. In addition, since the deformation of the substrate during processing due to heat is reduced, it was possible to form a hole with no misalignment between the window and the bottom of the hole. Further, it was confirmed that as a result of obtaining a uniform truncated cone-shaped hole in the insulating layer 7z, it is possible to make the hole diameter pitch twice the hole diameter. Further, when the through holes are formed on the printed circuit board, the hole shapes on the front and back surfaces are uniformly symmetrical, and the variation in the diameter of the hole intermediate portion is small, so that the plated finished surface becomes uniform. As a result, the overhang of the copper layer 7c around the window due to half etching (removing the copper layer 7c a little more than half the thickness by etching) performed prior to the plating process is reduced to about 3 μm, and the copper layer 7c is reduced to about 3 μm. Since it is possible to omit the dedicated removal work of the overhang, it was confirmed that the plating work process can be simplified.

In the case of the prior art, after forming a window with one laser pulse having a pulse width of 5 μs using an aperture having a diameter of 3.4 mm, the diameter is equal to the window diameter with six laser pulses having a pulse width Pw of 1.5 μs. When a hole of 65 μm was formed in the insulating layer 7z, no dent 11 was generated in the portion where the glass fiber density was high, and a slight dent 11 was generated in the portion where the glass fiber density was low and the resin ratio was high. Was around 80 μm (overhang of the copper layer 7c 7.5 μm), which was a level close to that of the present application.
On the other hand, in the case of the prior art, after forming a window with one laser pulse having a pulse width of 5 μs using an aperture having a diameter of 3.4 mm, the pulse width Pw is 3 pulses with a pulse width of 3 μs and the diameter is 65 μm equal to the window diameter. When the holes were formed in the insulating layer 7z, dents 11 were generated in both the high and low glass fiber densities, and when the glass fiber densities were low, the diameter was about 95 μm (overhang 15 μm of the copper layer 7c). Moreover, the variation in shape became large. It was found that the overhang of the copper layer 7c became about 10 μm or more even after half-etching, and there was a possibility that the generation of voids increased in the plating process.

Next, the result of actually processing a printed circuit board having a copper layer having a thickness of 1.5 μm and an insulating layer having a thickness of 40 μm without surface treatment will be described.
Using an aperture with a diameter of 3.4 mm, a window with a diameter of 65 μm was formed with one laser pulse having a pulse width of 5 μs. Then, using an aperture with a diameter of 2.6 mm, the diameter of the insulating layer under the copper layer was about 75 μm (overhang 5 μm) without dents 11 regardless of the height of the glass fiber density by one laser pulse with a pulse width of Pw3 μs. It was confirmed that a uniform truncated cone-shaped hole having a hole bottom diameter of 60 μm or more could be machined. It was also found that the overhang of the copper layer 7c can be removed by flash etching (etching with an etching amount of 1 μm or less) in the plating step.

Next, the effect of shortening the processing time will be described.
As described above, the galvano mirror 5a and 5b positioning time is about 0.4 ms (2.5 kHz) on average. Therefore, if the processing of the insulating layer 7z is reduced from 6 pulses to 3 pulses, the galvano mirror 5a and 5b positioning time is halved. Therefore, for example, when the number of holes in one printed circuit board is 800,000, it is about 40%. The processing time can be shortened.

FIG. 6 is an overall view of the second laser processing machine for carrying out the present invention, and the same thing as that of FIG. 1 or the thing having the same function is designated by the same reference numeral, and detailed description thereof will be omitted.
Between the plate 22A and the galvano mirror 5a, a plate 22B having the same number of apertures 4B1 to 4Bn as the apertures 41 to 4n is arranged in the axial direction of the laser 2. The respective hole diameters of the apertures 4B1 to 4Bn are smaller than the respective hole diameters of the corresponding apertures 4A1 to 4An. The plate 22B is supported by a first linear motion device 23B having the same structure as the first linear motion device 23A. The plate 22B is positioned at one moving end of the first linear motion device 23B at a position (operating position) where any axis of the apertures 4B1 to 4Bn is coaxial with the axis of the laser 2. Further, at the other moving end of the first linear motion device 23B, the plate 22B is positioned at a position (retract position) that does not interfere with the laser 2.
The first linear motion device 23B is supported by a second linear motion device 24B having the same structure as the first linear motion device 24A. The second linear motion device 24B positions any axis of the apertures 4B1 to 4Bn at the operating position coaxially with the axis of the laser 2. The first linear motion device 23B and the second linear motion device 24B constitute a positioning device for apertures 4B1 to 4Bn. The first linear motion device 23B and the second linear motion device 24B are connected to the control device 10, respectively.

Next, the operation of the second laser processing machine for carrying out the present invention will be described.
FIG. 7 is a flowchart showing a processing procedure of the second laser processing apparatus according to the present invention. The same procedure as the processing procedure of the first laser processing apparatus will be described in a simplified manner.
The control device 10 reads the machining program, moves the XY table 9, and makes the first scan area 8 face the fθ lens 6 (procedure S10). Further, the aperture of the large plate 20 (any one of apertures 41 to 4n) corresponding to the hole diameter to be machined first in the first scan area 8 is selected, and the axis of the aperture is coaxial with the axis of the laser 2. Positioning (procedure S20). Further, when the plate 22A is positioned at the operating position, the second linear motion device 24A is operated so that the axis of the aperture used for processing the insulator in the apertures 4A1 to 4An coincides with the axis of the laser 2. The plate 22A is positioned at the retreat position (procedure S30). Further, when the plate 22B is positioned at the operating position, the second linear motion device 24B is operated so that the axis of the aperture used for processing the insulator in the apertures 4B1 to 4Bn coincides with the axis of the laser 2. The plate 22B is positioned at the retreat position (procedure S40). The diameter of the apertures 4B1 to 4Bn used for processing should be smaller than the diameter of the apertures 4A1 to 4An used for processing. Then, as in the prior art, the window is formed by the 1-pulse laser 2 and the copper layer 7c of the remaining holes in the scan region 8 is machined (procedure S50, procedure S60). When the processing of the copper layer 7c is completed, the plate 22A is positioned at the operating position, that is, the axis of one of the apertures 4A1 to 4An used for insulating material processing is aligned with the axis of the laser 2 (procedure S70). , The window portion insulating layer 7z in the scan area 8 is machined to complete the hole (procedure S80 to procedure S130). Then, when the processing of the window portion insulating layer 7z in the scan area 8 is completed, it is confirmed whether or not the hole bottom is processed (procedure S200), and if the hole bottom is not processed, the processing of procedure S500 is performed. When processing the hole bottom, the plate 22B is positioned at the operating position, that is, the axis of one of the apertures 4B1 to 4Bn selected in advance is aligned with the axis of the laser 2 (procedure S210). By irradiating all the hole bottoms in the scan area 8 that have been machined with the laser 2 one pulse at a time, the hole bottoms of the machined holes are additionally machined (procedures S220 and S230). Then, when the processing of the hole bottom in the scan area 8 is completed, it is confirmed whether or not there are unprocessed holes having different diameters in the scan area 8 (procedure S500), and if there is an unprocessed hole, the procedure is performed. Work on S20. If there is no unprocessed hole, it is confirmed whether there is an unprocessed scan area 8 (procedure S510), and if there is an unprocessed scan area 8, the operation of step S10 is performed, and the unprocessed scan area is performed. If there is no 8, processing is finished.
In this way, since the hole bottom is machined by the aperture 4Bn having a diameter smaller than that of the aperture 4An, the hole bottom diameter can be made more uniform.

This processing method is also effective in X-shaped through-hole processing in which the hole diameter of the intermediate portion is small. That is, first, a hole is machined from one side of the double-sided substrate to the intermediate portion, then the double-sided substrate is inverted, and a hole is machined from the other side to the intermediate portion. Finally, when the intermediate portion of the hole is machined by the procedures S210 to S230 , not only the variation in the hole diameter of the intermediate portion can be reduced, but also the quality of the hole wall surface of the intermediate portion can be improved.

In this embodiment, since the same number of apertures as the apertures of the large plate 20 are provided on each of the plates 22A and 22B, the apertures can be easily managed. In this embodiment, the apertures 4A1 to 4An of the plate 22A and the apertures 4B1 to 4Bn of the plate 22B are arranged in one row, but can be appropriately changed such as arranging them in two rows.

Further, in this embodiment, the first linear motion devices 23A and 24B are arranged in the axial direction of the laser 2, but they may be arranged around the axis of the laser 2.

Further, in the first and second embodiments, the apertures 4A1 to 4An and the apertures 4B1 to 4Bn have the same number as the apertures 41 to 4n, but when the hole diameter to be machined is 100 μm or more, plating is formed on the insulator 7z. Since it is easy to reach the bottom of the hole, for example, a hole of 210 μm or a hole of 190 μm may be machined with an aperture for 200 μm to reduce the number of apertures 4A1 to 4An or apertures 4B1 to 4Bn.

By the way, the surface of the copper layer below the insulating layer, that is, the copper layer exposed at the bottom of the hole, is roughened in order to increase the adhesion strength with the insulating layer (also referred to as peel strength and peel strength). Therefore, the absorption rate of the laser 2 is high, the energy level near the axis _OL is large (however, it is much smaller than the energy level j), and the surface may be melted. If the surface of the lower copper layer melts, the insulating layer on the back surface of the lower copper layer may deteriorate, so it is necessary to avoid melting the surface of the hole bottom copper layer.
FIG. 8 shows the second hole bottom treatment procedure in the case of treating the hole bottom, which is suitable when the thickness of the lower copper layer 7c is thin (particularly 7 to 9 μm), and is shown in FIGS. 1 and 6. It can be applied to any of the laser processing machines of the present application. Since the processing of the procedure S10 to the procedure S130 and the processing of the procedure S500 and the procedure S510 are the same as the flowcharts described with reference to FIGS. 2 and 7, the duplicate description will be omitted.
When the processing of the window portion insulating layer 7z in the scan area 8 is completed, it is confirmed whether or not the hole bottom is processed (procedure S200). If the hole bottom is not processed, the hole bottom is processed and the hole bottom is processed. When processing, the plate 22A and the plate 22B (only the plate 22A in the case of FIG. 1) are returned to the refuge position (procedure S300), and the laser is applied to the bottom of all the holes in the scan area 8 after processing. By irradiating 2 one pulse at a time, the bottom of the machined hole is additionally machined (procedure S310, procedure S320). Then, when the processing of the hole bottom in the scan area 8 is completed, it is confirmed whether or not there are unprocessed holes having different diameters in the scan area 8 (procedure S500), and if there is an unprocessed hole, the procedure is performed. Work on S20. If there is no unprocessed hole, it is confirmed whether there is an unprocessed scan area 8 (procedure S510), and if there is an unprocessed scan area 8, the operation of step S10 is performed, and the unprocessed scan area is performed. If there is no 8, processing is finished. In the case of this embodiment, since the aperture 4s in which the copper layer is processed is used as the aperture for processing the hole bottom, there is an advantage that the work of reducing the energy density becomes easy. In the procedure S310, it is effective to determine the energy distribution curve so that the hole bottom has the energy level g.

Here, the difference between the present invention and the technique of Patent Document 1 will be described.
Most of the hole diameters to be machined on the printed circuit board 7 are 40 μm to 250 μm. Then, for example, when drilling a hole of 50 μm, an aperture having a hole diameter of 2 mm is adopted, and when drilling a hole of 250 μm, an aperture having a hole diameter of 8 mm is adopted. In the case of the technique of Patent Document 1, even when a hole of 50 μm is machined, a laser having a diameter of 8 mm that has passed through the aperture having the maximum diameter is supplied to a plate having an aperture for drilling a hole of 50 μm. The cooling system for each plate needs to be large. On the other hand, in the present invention, the outer shape of the laser 2 for processing the copper layer 7c is limited by the large plate 20, and the insulating layer 7z is processed by the laser 2 having the limited outer shape, so that the insulating layer 7z is supplied to the plates 22A and 22B. Energy becomes smaller. As a result, the cooling device for cooling the plates 22A and 22B can be made smaller.

Further, in this embodiment, the case where the laser 2 is a carbon dioxide gas laser has been described, but other lasers may be used. Further, although the case where the copper layer is processed with one pulse has been described, the copper layer may be processed with a plurality of pulses having a small pulse width Pw (for example, picoseconds and femtoseconds).

1 laser oscillator 2 laser 2
4 Aperture 5 Galvano device 6 fθ lens 7 Printed circuit board 7c Copper layer of printed circuit board 7 7 Insulation layer of printed circuit board 7

Claims (3)

The outer shape of the laser output from the laser output device is shaped by the aperture, the laser is positioned by the galvano device and the Fθ lens , and a hole is formed at a desired position on the printed circuit board composed of the copper layer and the insulating layer. In the laser processing method of the printed circuit board
A through hole is formed in the copper layer by the laser shaped by the first aperture, and the through hole is formed.
After that, the diameter of the laser that contributes to the processing of the insulating layer is processed by the first aperture by using the second aperture having a diameter smaller than that of the first aperture and adjusting the pulse width. The insulating layer is processed by shaping it to the diameter of the through hole.
A laser processing method for printed circuit boards, which is characterized by this. The outer shape of the laser output from the laser output device is shaped by the aperture, the laser is positioned by the galvano device and the fθ lens, and the thickness direction of the board is from one side of the double-sided printed circuit board composed of the copper layer and the insulating layer. By forming a hole to a substantially intermediate point and forming a hole from the other surface opposite to the one surface to a substantially intermediate point in the thickness direction of the substrate, the hole diameter of the intermediate portion is small in the X shape. In the laser processing method of a printed circuit board in which a through hole is formed, the inner surface of the formed through hole is shaped by an aperture having a diameter smaller than the hole diameter of the aperture in which the through hole is formed. The laser processing method for a printed circuit board according to claim 1, wherein the finishing process is performed with a laser. A laser output device, a plate having an aperture, a galvano device, and an fθ lens are provided, and the outer diameter of the laser output from the laser output device is shaped by the aperture, and the shaped laser is referred to as the galvano device. In a printed circuit board laser processing machine positioned by the fθ lens so as to form a hole at a desired position on the printed circuit board composed of a copper layer and an insulating layer.
A first plate with multiple apertures of different diameters,
A positioning device for the first plate that positions the axis of each aperture provided on the first plate coaxially with the axis of the laser.
M plates (where m is a positive integer) with n apertures (where n is a positive integer), each axis parallel to the axis of the laser, and
The processing position where the moving direction of each of the m plates is perpendicular to the axis of the laser and the axis of the aperture provided in each is positioned coaxially with the axis of the laser, and the plate is the laser. It is provided with m plate positioning means for positioning at a retreat position that does not interfere with the first plate, and a control device for controlling the first plate positioning device and the m plate positioning means .
The first plate is arranged on the side closest to the laser output device between the laser output device and the galvano device in the axial direction of the laser, and the m plates are arranged in the axial direction of the laser. Placed between the first plate and the galvano device,
When processing the copper layer , the control device positions the axis of the designated aperture of the first plate coaxially with the axis of the laser, and all the other m plates are in the retreat position. Positioned to
When processing the insulating layer, the aperture used for processing the copper layer (hereinafter referred to as "first aperture") is n in a state where the axis is coaxial with the axis of the laser. An aperture having a diameter smaller than that used for processing one of the × m copper layers (hereinafter referred to as “second aperture”) is positioned at the processing position, and the first aperture is used. The laser with a shaped outer diameter is supplied to the second aperture for processing.
A laser processing machine for printed circuit boards, which is characterized by being used.

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