JPH08243771A - Method and device for perforating printed circuit board by pulse laser beam - Google Patents

Abstract

PURPOSE: To provide a method and device by which perforation of a through- hole, slit or component hole, etc., of a printed circuit board are performed in a short time, easily, accurately, surely and finely. CONSTITUTION: Perforation is performed by the use of a pulse laser beam with a wavelength of 9.0-11.0μm. It is performed by the use of a machining device consisting of a laser generator 1, laser beam coaxial observation device 15, XY table for machining 13, gas blower 43 and dust sucking machine. An object to be worked may also be irradiated with a laser beam by using a galvano- mirror. In that case, a laser beam observation device may be used in place of or in combination with the laser beam coaxial observation device 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wiring for making through holes, slits, component holes, etc. of printed wiring boards by using pulsed laser light having a wavelength of 9.0 to 11.0 .mu.m. The present invention relates to a drilling method and a machining device for efficiently machining a plate.

[0002]

2. Description of the Related Art Printed wiring boards are used for industrial electronic equipment such as electronic calculators, electronic exchanges, office automation equipment, communication equipment, electronic equipment, electric measuring instruments, televisions, radios, tape recorders, audio equipment, VTRs and other consumer products. Widely used in electronic devices for home use. Recently, portable communication devices, cameras, watches,
It is becoming popular for compact devices such as calculators. As described above, recently, there is a strong demand for miniaturization, high-density mounting, and high performance of electronic devices. Based on this, thinning of conductor patterns, reduction of diameter of through holes, reduction of diameters of lands and pads, and wiring board Flexibility, multi-layering, and fineness are rapidly advancing.

Further, as the material used for the wiring board, in addition to conventional materials such as epoxy resin, phenol resin, acrylic resin, etc., materials such as polyimide film and polyester film which are excellent in flexibility are also used in view of higher performance. Therefore, materials such as fluorine resin, polyphenylene oxide, polysulfone, and polyetherimide have been developed and used.

Generally, a printed wiring board has a structure in which a patterned copper foil is adhered onto an insulating laminated board or a base film, and an insulating material such as a film is laminated on it if necessary. Further, in order to cope with the recent trend toward higher density, smaller size, and finer structure, this structure is often a double or triple structure.
Then, through holes, slits, or component holes are provided in places where plating or soldering is required or where components are mounted.

Conventionally, a chemical method or a mechanical method, that is, a drill is used to form a hole such as a through hole, a slit, or a component hole. In addition, an insulator (film or the like) to be laminated on the conductor has a method in which holes are preliminarily formed in necessary places before laminating, and after laminating, lamination is performed. The punching of the film or the like is similarly performed by using a drill or punching.

However, recent miniaturization of electronic equipment,
Due to strong demands for high-density mounting and high performance, thin conductor patterns, smaller holes such as through holes, slits, component holes, smaller lands, pads, etc., and flexible and multilayer wiring boards However, conventional drilling methods have reached their limits. In the conventional drilling, the minimum hole diameter is about 1 mm, and there is a limit to reducing the diameter. Further, in the case of a drill, it is not possible to make a hole in the inner corner R of which is 0.5 mm or less. Further, a slit-shaped hole, a square hole, an irregularly shaped hole, etc. cannot be formed. In the case of a slit-shaped hole, the round shape of the drill remains as jagged. Also, when laminating a film or the like with pre-drilled holes, the holes drilled in the film or the like and the positions of the holes required on the copper foil of the wiring board do not exactly match, and the problem of misalignment always occurs. is there.

As a method for avoiding the above problems, the use of laser light has been proposed and partially implemented. The characteristics of the perforation processing by laser light are that the diameter of the hole can be reduced, the shape of the hole can be something other than circular, and the film or the like to be laminated can be laminated without pre-perforating. There is a possibility that the punching process can be performed after laminating, that is, the problem of positioning when laminating is solved.

Of the laser beams, the excimer laser has attracted attention. When excimer laser light is used, it is possible to form a smaller through hole in an area having a width of tens of μm or a radius of tens of μm. However, this excimer laser beam has a drawback that the apparatus itself is expensive and the processing time is long, and the running cost is high.

A printed wiring board is manufactured by
There are various forms depending on specifications and purposes. When a printed wiring board having these various forms is processed by excimer laser light, the excimer laser light can be used to punch holes in a portion made of polyimide, but for example, in a portion made of another resin such as a fluorine-based resin. Drilling is not possible. The limitation of the processing material and the high processing cost combine with the reason that the excimer laser is not widely used even though the processing method using the laser beam is considered to be an effective method.

[0010]

[Problems to be Solved by the Invention] Effective punching of a printed wiring board in response to the trend toward thinning / miniaturization, high density and high performance of equipment, and further to the trend toward finer patterns. As a method, it is a problem to be solved by the present invention to provide an effective method and apparatus using a laser beam.

[0011]

Means for Solving the Problems As a method for efficiently making holes in a required portion of a printed wiring board having different materials, designs, film thicknesses, etc., the present inventor uses a specific laser beam to pass through very efficiently. The present invention has been completed, paying attention to the fact that holes, slits, component holes and the like can be drilled.

That is, when the through hole, the slit or the component hole of the printed wiring board is drilled,
The present invention relates to a method for punching a printed wiring board, which uses pulsed laser light having a wavelength of 0 to 11.0 μm, and a processing apparatus therefor.

The processing device is a laser oscillator that oscillates a pulsed laser light having a wavelength of 9.0 to 11.0 μm, a laser light coaxial observation device for accurately irradiating the processing light on a workpiece with laser light, and a laser processing device. A device including an XY table and a dust removing device, a laser oscillator that oscillates a pulsed laser beam having a wavelength of 9.0 to 11.0 μm, and a laser for accurately irradiating the laser beam to a processing position of a workpiece. It is a device including an optical coaxial observation device and / or a laser light observation device, an XY table for laser processing, a galvanometer mirror, and a dust removal device.

Originally, the energy density of the laser light, the irradiation direction of the laser light, the irradiation time of the laser light, etc. can be electrically controlled, and the laser light is fixed by combining an optical system such as a mask module and an expander. It is possible to arbitrarily set the irradiation shape of the laser light within the area. Further, since the laser light is non-contact and the processing process is a dry process, it has a feature that it is easy to handle as compared with a chemical method or a mechanical method. The processing by this point laser light is suitable for industrial implementation.

However, the excimer laser beam, which is attracting attention in the drilling process, can be processed with high accuracy for materials such as polyimide, polysulfone, and polyethylene naphthalate by using a KrF type having a wavelength of 0.248 μm. is there. However, the film removal depth per pulse during processing is as shallow as about 0.2 μm, and therefore a considerable amount of pulses are required for processing and the processing time becomes long. Further, as described above, the device is expensive and the running cost is high, which is not suitable for efficient industrial production. Further, the excimer laser light having a wavelength of 0.248 μm has a restriction that it cannot be processed because the laser light is not absorbed by the fluororesin.

On the other hand, the pulsed laser light having a wavelength of 9.0 to 11.0 μm is efficiently absorbed by all the above materials, so that the film can be easily removed and the removal depth per pulse is large. It is as large as 20 to 50 μm and has excellent processing ability. Therefore, in the present invention, pulsed laser light having a wavelength of 9.0 to 11.0 μm is used.

The laser oscillator has a characteristic of pulse oscillation in principle, but a continuous wave type has been widely used because of the desire to use continuous laser light. . On the other hand, some pumps do not realize continuous waves due to their excitation mechanism. In this case, the intensity of the oscillated laser light is high and the pulsed laser light has high brightness.

In the present invention, it is 9.0 to 11.0 μm.
A pulsed laser beam with a wavelength is used. Specific examples of the laser light used include high-intensity pulsed laser light having a wavelength of 9.3 μm and pulsed carbon dioxide laser light. The high-intensity pulsed laser light with a wavelength of 9.3 μm here is a laser light obtained from a laser oscillator (trade name “impact laser”) manufactured by Sumitomo Heavy Industries, Ltd., for example. The laser light oscillated from this “impact laser” is pulsed laser light and high-intensity laser light with high oscillation intensity.

Normally, when carbon dioxide gas is excited, it is 9.0-1.
Laser light having a spread of 1.0 μm can be obtained. Among them, laser light having a wavelength of 10.6 μm is efficiently oscillated. The wavelength of the laser light to be resonated can be selected within the range of 9.0 to 11.0 μm by changing the coating material of the front mirror and the rear mirror of the laser light oscillator. Further, by changing the oscillation mode from continuous wave to intermittent wave, pulsed laser light can be obtained. When a continuous wave of carbon dioxide gas laser light is used, the work piece melts, or the work piece partially burns and cannot be used for drilling. Drilling has become possible.

By using pulsed laser light having a wavelength of 9.0 to 11.0 μm, it became possible for the first time to use laser light effectively and practically for drilling a printed wiring board. Of. According to the present invention, it becomes possible to perform the drilling of the printed wiring board in a short time and more accurately than in the conventional case.
The economic value of the present invention is extremely high.

Next, in order to perform fine processing, that is, precise processing, it is necessary to precisely irradiate the position to be processed of the object to be processed with laser light. A mechanism for efficiently performing this positioning is required. Flexible printed wiring board is O
It is often used for components such as A-equipment and consumer electric appliances, and it is desired that the cost can be suppressed, the yield be good, and the mass production be possible. In a flexible printed wiring board, the thickness of the insulator such as a film is several μm to several tens of μm, so it is necessary to irradiate several pulses for drilling with a pulse laser beam of 9.0 to 11.0 μm wavelength. It will be good.
Irradiation time of 0.1 seconds or less is sufficient for laser light oscillation of several pulses. From this, it is earnestly desired to perform the drilling process without spending extra time for positioning. When performing positioning by the offset method, it takes 0.5 to 1 second just to move and return the processing table, which impairs mass productivity.

In order to perform this positioning efficiently, the invention "coaxial observation device in laser processing" described in Japanese Patent Application No. 6-282839 filed separately by the present applicant can be used. By using this coaxial observation device, the target position of the work piece and the center of the laser beam can be adjusted to several tens to
Since it has the advantage that it can be magnified and observed several hundreds of times, it has an excellent effect on fine processing of printed wiring boards.

The coaxial observing device referred to here is provided in a processing device which guides laser light from a laser oscillator to a workpiece and performs processing, and in laser processing for observing the irradiation position of the laser light on the workpiece. A coaxial observation and control device,
The visible laser light is sent to the object to be processed coaxially with the optical path axis of the laser light, the reflected light of the visible laser light is captured by a CCD camera, the captured image is displayed on a monitor, and image processing is performed by a computer. It is a device that adjusts the processing XY table via the NC control device so that the irradiation position of the laser light coincides with the target position.

When processing with laser light, the method of irradiating the laser light at a predetermined position by moving the XY table on which the object to be processed is placed without changing the position of the laser light is adopted. Alternatively, instead of moving the XY table, there is also a method of operating the galvanometer mirror to sequentially change the place where the laser light is irradiated. This is a method also called a galvano scan system.

There are two galvanometer mirrors, each of which is X.
It is configured so that it can rotate around the axis and the Y axis. Each mirror is a motor that rotates based on commands from a computer. The galvanometer mirror rotates and the desired position is irradiated with laser light to perform the target boring process. When using a galvanometer mirror, it is not necessary to utilize the above-mentioned laser light coaxial observation device. A normal laser light observation device may be used. That is, an arbitrary position on the XY table is designated, the position is observed using a CCD camera, the computer calculates the deviation between the observation result and the designated position, and the XY table is moved so that the deviation becomes zero. At the very least, positioning is performed. However,
The range that can be covered by the galvano mirror is limited, so X
It is preferably used in combination with the Y table.

[0026]

The present invention will be described with reference to FIGS. The laser oscillator 1 is an oscillator that oscillates pulsed laser light having a wavelength of 9.0 to 11.0 μm. Laser oscillator 1
The laser light 3 oscillated from the laser beam 3 passes through the mask 5, the total reflection mirror 7, and the processing lens group 9 and the processing XY table 13
An image is formed on the workpiece to be processed, that is, the printed wiring board 11, and the punching process is performed. A ring light 27 that illuminates the object to be processed is installed in the processing lens group 9. If necessary, place a galvanometer mirror 4 in front of the processing lens group.
5, 47 are provided.

On the other hand, the coaxial observation device 15 is used to perform the positioning accurately. Visible laser light is oscillated from a visible light laser oscillator (using a semiconductor laser or a He-Ne laser) 17, passes through a total reflection mirror 21, a semi-transmission mirror 23, and a beam compiler 25, and then is processed like the laser light 3. 11 is imaged. The beam compiler 25 functions as a filter that reflects visible light and transmits pulsed laser light having a wavelength of 9.0 to 11.0 μm.

The beam compiler 25 uses the surface image of the work piece illuminated by the ring light 27 and illuminated by the visible laser light set at the center of the laser light path as reflected light.
It is taken into the CCD camera 29 via the. The CCD camera 29 is connected to a monitor 35 and a computer 37 for image processing.

The computer 37 plays a role of image-processing the surface state of the workpiece to be taken in, detecting a deviation between the laser light irradiation position and the target position, and issuing a correction signal. The correction signal from the computer 37 is transmitted to the NC control device 39. The NC control device 39 sets the machining XY table 13 based on the correction signal from the computer 37.
By moving in the X direction and / or the Y direction, the position of the workpiece is adjusted to the target position.

The Galvano mirrors 45 and 47 are provided in two sets so that they can rotate about the X axis and the Y axis, respectively. Each of the mirrors is rotated by a motor based on a command from a galvanometer mirror controller 49 having a computer. In determining the irradiation position of the laser light, it is not always necessary to use the laser light coaxial observation device, and the image captured by the laser light observation device, that is, the CCD camera 29 is processed by a computer to drive the XY table 13 by the NC control device 39. You can also choose to do so. Of course, the laser light coaxial observation device may be used, or the laser light coaxial observation device may be used together.

In the laser beam processing, dust such as soot or dust is generated, and in order to remove it, for example, a gas blowing machine and a dust collecting suction machine are required. First, an assist gas is sprayed to remove dust and the like. The gas is supplied from the gas generator 41 and is sprayed from the spraying machine 43 toward the workpiece. A suction device for sucking dust is generally installed in the laser beam processing machine. The gas blowing is provided in addition to the suction device (not shown) for removing dust, soot generated during processing,
It removes dust. The gas used here may be air, but an inert gas such as nitrogen, argon or helium is preferably used. As the gas generator, it is convenient to use a compressed gas (including air) or a cylinder.

In this way, the insulator (film or the like) of the object to be processed is removed to form through holes, slits or component holes, and then plating or bump-up processing is performed to finish the printed wiring board. Of.

[0033]

EXAMPLES The following examples are carried out by the apparatus shown in FIG. 1 except that Example 3 was carried out by using the apparatus shown in FIG.

[0034]

Example 1 A flexible printed wiring board in which a copper wiring pattern was arranged on a polyimide and covered with a polyimide layer having a thickness of 30 μm was applied to a flexible printed wiring board at 60 W, 150 Hz, 9.3.
A high-intensity pulsed laser light having a wavelength of μm was irradiated.
The polyimide layer was removed and the holes reached the copper pattern layer in about 3 pulses, that is, in the irradiation time of about 0.03 seconds. Note that 9.
The high-intensity pulsed laser light with a wavelength of 3 μm was generated using a product name “Impact Laser” manufactured by Sumitomo Heavy Industries, Ltd.

[0035]

Comparative Example 1 For comparison, when the same flexible printed wiring board as in Example 1 was irradiated with 60 W, 200 Hz excimer laser light (wavelength 0.248 μm), the hole required 150 pulses, and It took 75 seconds.

[0036]

Example 2 A copper wiring pattern was arranged on a polyimide film, and a flexible printed wiring board having a size of 400 × 300 mm covered with a polyimide layer having a thickness of 30 μm was provided with 200 holes (through holes). In order to open, high-intensity pulsed laser light having a wavelength of 9.3 μm of 60 W and 150 Hz was irradiated. The required irradiation time was 3 minutes or less. The high-intensity pulsed laser light having a wavelength of 9.3 μm was generated using a product name “Impact Laser” manufactured by Sumitomo Heavy Industries, Ltd.

[0037]

Comparative Example 2 On the other hand, irradiation with 60 W, 200 Hz excimer laser light (wavelength: 0.248 μm) in this case required irradiation time of 15 minutes. Comparison between Example 2 and Comparative Example 2 reveals that through-hole processing can be efficiently performed by using a high-intensity pulsed laser light having a wavelength of 9.3 μm.

[0038]

[Example 3] A flexible printed wiring board having a copper wiring pattern on Teflon and a Teflon layer having a thickness of 75 µm formed on the copper wiring pattern was applied to a flexible printed circuit board having a thickness of 60 µW and 150 Hz, and a high-intensity pulse laser of 9.3 µm at 150 Hz as in Example 1. It was irradiated with light. The time required to expose the copper wire pattern, that is, for drilling, is 1
0 pulse was about 0.07 seconds. The high-intensity pulsed laser light having a wavelength of 9.3 μm was generated using a product name “Impact Laser” manufactured by Sumitomo Heavy Industries, Ltd.

[0039]

Comparative Example 3 A flexible printed wiring board having a copper wiring pattern on the same Teflon as in Example 3 and having a Teflon layer having a thickness of 75 μm thereon is placed on a 60 W, 200 Hz excimer laser beam (wavelength 0.248 μm). When it was irradiated with, the Teflon could not be processed at all, holes were not formed, and the copper wire pattern could not be exposed. Comparing with Example 3, it can be seen that the high-intensity pulsed laser light with a wavelength of 9.3 μm does not have a restriction on the material of the object to be processed and can efficiently perform through-hole processing.

[0040]

[Example 4] A flexible printed wiring board, in which a copper wiring pattern was arranged on polyimide and covered with a polyimide layer having a thickness of 30 µm, had a main wavelength of 10.6 µm, an energy density of 8.0 mJ / P, and a pulse width. One pulse of pulsed carbon dioxide laser light of 450 μs was irradiated. As a result, the polyimide layer was removed and the holes reached the copper pattern layer.

[0041]

Fifth Embodiment A pulsed carbon dioxide laser beam having an energy density of 8.5 mJ / P and a pulse width of 450 μs is applied to a flexible printed wiring board having a copper wiring pattern on polyimide and a Teflon layer having a thickness of 25 μm formed thereon. It was pulsed. As a result, it was confirmed that holes were formed in the Teflon layer and the holes reached the copper wire portion. In addition, when the carbon dioxide laser light which oscillates a continuous wave is irradiated, the phenomenon that the workpiece is melted or burned in some cases was observed.

[0042]

[Comparative Example 4] A copper wiring pattern was arranged on the same polyimide as in Example 5, and a flexible printed wiring board having a Teflon layer having a thickness of 25 µm thereon was irradiated with excimer laser light (wavelength 0.248 µm). , Teflon could not be processed at all, holes were not formed, and the copper wire pattern could not be exposed. As compared with the fifth embodiment, it is understood that the pulsed carbon dioxide laser light has no restriction on the material of the object to be processed and can efficiently perform through-hole processing.

[0043]

EFFECTS OF THE INVENTION By using a pulsed laser beam having a wavelength of 9.0 to 11.0 μm, the punching process of the printed wiring board is not restricted by the material of the wiring board and can be performed in a short time.
It can be done easily, accurately and finely. This drilling is performed by using a processing device including an oscillator for pulsed laser light with a wavelength of 9.0 to 11.0 μm, a laser light coaxial observation device, a processing XY table, a gas spraying machine, and a dust collecting suction machine. , Can be implemented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a device of the present invention.

FIG. 2 is a block diagram showing another embodiment of the device of the present invention.

[Explanation of symbols]

 1 Laser Oscillator 3 Laser Light 5 Mask 7 and 21 Total Reflection Mirror 9 Lens Group 11 Workpiece 13 XY Table for Processing 15 Laser Optical Coaxial Observation Device 17 Visible Laser Oscillator 19 Invisible Laser Light 23 Semi-Transparent Mirror 25 Beam Compiler 27 Ring Light 29 CCD camera 31 Reflected light 33 Visible laser light 35 Monitor 37 Computer 39 NC control device 41 Gas generator 43 Gas blowing machine 45, 47 Galvanomirror 49 Galvanomirror control device 51 Laser light observation device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H05K 3/00 H05K 3/00 N

Claims (3)

[Claims] 1. When making a hole such as a through hole, a slit or a component hole of a printed wiring board, 9.0 to 1 is used.
A method for punching a printed wiring board, which comprises using pulsed laser light having a wavelength of 1.0 μm. 2. A laser oscillator that oscillates a pulsed laser beam having a wavelength of 9.0 to 11.0 μm, a laser beam coaxial observation device for accurately irradiating the laser beam to a processing position of a workpiece, an XY table for laser processing. , A device for removing dust, etc., for forming through holes, slits, component holes, etc. of a printed wiring board. 3. A laser oscillator that oscillates a pulsed laser beam having a wavelength of 9.0 to 11.0 μm, a laser beam coaxial observation device and / or a laser beam observation device for accurately irradiating the laser beam to a processing position of a workpiece. A drilling device for a through hole, a slit, a component hole, or the like of a printed wiring board, which comprises a device, an XY table for laser processing, a galvano mirror, and a device for removing dust and the like.