JP3338927B2 - Desmear apparatus and desmear method for laser drilling machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser drilling apparatus for forming a via hole in a printed circuit board, particularly a multilayer printed circuit board, using a laser beam. The present invention relates to a desmear apparatus and a desmear method for removing a residual residue component.

[0002]

2. Description of the Related Art In response to the demand for higher density of printed circuit boards in accordance with the miniaturization and high-density mounting of electronic devices, recently, multilayer printed circuit boards in which a plurality of printed circuit boards are stacked have appeared. In such a multilayer printed circuit board, it is necessary to electrically connect conductive layers (copper boards) between printed circuit boards stacked one above another. Such connection is made by a resin layer (polyimide,
This is realized by forming a hole called a via hole reaching the lower conductive layer in a polymer such as an epoxy resin) and plating the inside of the hole.

[0003] As a method of forming via holes, a mechanical fine drill was used before. However, with the reduction in the diameter of via holes accompanying the increase in density of printed circuit boards, recently, a laser drilling apparatus using laser light instead of a fine drill has been adopted.

[0004]

For example, a laser drilling apparatus for forming a via hole using a carbon dioxide gas laser or a YAG laser is well known, and has the advantage of being inexpensive and capable of high-speed processing. However, the via hole formed by such a laser drilling apparatus is thin on the bottom surface of the hole formed in the resin layer, that is, on a part or the entire surface of the conductive layer to be exposed (for polyimide or epoxy resin, There is a problem that a residual component (called smear) remains (thickness of 1 μm or less).

[0005] This residual component cannot be completely removed by further irradiating a laser beam thereafter. This is because even if the residual component is evaporated by further irradiating the laser beam, the surrounding resin elutes at this time (the conductive layer is often made of copper and the heat diffusion is fast), and the new residual component is removed. It is thought that it forms.

For this reason, conventionally, a wet process using a permanganate solution has been required after the laser processing in order to remove the residual components. This wet process has the following two purposes.

[0007] 1. 1. Removal of residual components on the conductive layer surface Roughening treatment of inner wall of via hole and conductive layer surface The above roughening treatment makes it easy to set conditions for the wet process, but it is difficult to set conditions for removing residual components. That is, in order to remove the residual components, a swelling-permanganate etching-reduction step is usually required, and the type of the liquid,
It is difficult to determine the conditions such as the concentration of permanganate, the liquid temperature, the permeation time, and the method of permeating the liquid into the via holes.

Accordingly, an object of the present invention is to provide a desmear apparatus capable of removing a residual component of a via hole without a wet process.

Another object of the present invention is to provide a desmear method suitable for the above desmear apparatus.

[0010]

According to the present invention, a resin layer formed on a metal film is irradiated with a laser beam from a laser oscillator in a laser drilling apparatus to form a via hole in the resin layer. A desmear device for removing residual components remaining in a via hole, a green light generating device for generating green light, and a linear beam generating unit for converting the generated green light into a linear beam light And scanning means for scanning the linear beam light over the area where the via hole is formed.

[0011] The laser processing apparatus performs a drilling operation for each processing region in a plurality of processing regions having a size sufficiently smaller than the predetermined size set on a mother plate having a predetermined size. The length of the linear beam light is set longer than one side of the processing region.

Further, the green light generating device may be a YAG
Wavelength 532 from pulsed laser light from laser oscillator
(Nm) is extracted and output.
The linear beam generating unit irradiates the linear beam light in a pulse shape.

Further, the irradiation energy of the linear beam light per pulse is 1 (mJ) or less.

Further, the invention is characterized in that the green light generating device and the linear beam generating unit are connected by an optical fiber.

Further, the scanning means can scan the base plate by oscillating the linear beam light.

Further, in the case where the laser drilling apparatus includes an XY stage for mounting the mother plate and moving the mother plate in the X-axis direction and the Y-axis direction, the XY stage is used for the scanning. It can be used as a means.

[0017] The scanning means is further characterized in that scanning is performed such that a part of scanning areas adjacent to each other overlaps.

The desmear method according to the present invention is directed to a desmear method for removing a residue component remaining in a via hole formed by irradiating a resin layer formed on a metal film with a laser beam. Is converted into a linear light beam, and then the linear light beam is scanned in an area where the via hole is formed, thereby performing desmearing.

In this desmearing method, at least one via hole is formed in each of a plurality of processing regions having a size sufficiently smaller than the predetermined size set in a mother plate having a predetermined size, The length of the linear light beam is set to be longer than one side of the processing region, and scanning of the linear light beam is performed so that a part of the scanning regions adjacent to each other overlap.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing a preferred embodiment of the present invention, a laser drilling apparatus to which a desmear apparatus according to the present invention is combined will be described with reference to FIGS. In FIG. 6, a pulsed laser beam generated by a laser oscillator 10 using a CO ₂ (carbon dioxide gas) laser is guided to a mask 13 at an angle of 90 ° by a reflection mirror 11. In the mask 13, the beam diameter of the laser beam is narrowed by passing through a hole that defines a via hole diameter, and the laser beam is guided to the XY scanner 14. The XY scanner 14 is for oscillating the laser light, and the oscillated laser light acts as a focusing lens and fθ
Work (printed wiring board) 17 placed on an XY stage 16 through a processing lens 15 also called a lens
Is irradiated. The XY stage 16 has a drive mechanism in the X-axis direction and a drive mechanism in the Y-axis direction.
The position can be adjusted by moving on the Y plane.

In FIG. 7, the XY scanner 14
This is a so-called galvano scanner formed by combining two galvanometer mirrors 14-1 and 14-2. That is, the two reflection mirrors are independently rotated according to the driving principle of the galvanometer, so that the laser light is
5, it is possible to continuously irradiate a plurality of desired positions of the work 17.

In the case of laser light from a CO ₂ laser, a hole is formed by irradiating a pulsed laser light per via hole several times (usually two to three times).
Usually, the scanning range of the XY scanner 14 is several c.
The area determined by this scanning range is set in the form of a matrix in the work 17 as a processing area, as will be described later. Then, the laser drilling device performs a plurality of drilling operations on the processing region, and when the drilling operation of a certain processing region is completed, moves to the next processing region and performs the drilling operation of the same pattern. The movement to the next processing area is usually performed by the XY stage 16.

The desmear apparatus according to the present invention is combined with the laser drilling apparatus as described above, but is not particularly limited by the type of the laser oscillator.

A preferred embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a desmear device according to the present embodiment is a green light generating device 1 for generating green light having a predetermined wavelength.
And a linear beam generating unit 2 for converting the generated green light into a linear light beam in cross section. Further, although not shown, a scanning mechanism for scanning a processing area in which the via hole is formed with a linear beam light is included.

The size, particularly the length, of the linear beam light generated by the linear beam generating unit 2 is set to be slightly longer than one side of the processing area, as shown in an example in FIG. The example of FIG. 2 is a case where the processing area is a square having a side of 5 cm, in which case the length is 60 mm and the width is 0.1 m.
m or more. As described above, the size of the linear beam light depends on the area of the processing region, but the length is about 30 to 60 m.
m, and the width is about 0.1 to 0.5 mm.

The green light generating device 1 uses a YAG laser oscillator to extract the second harmonic having a wavelength of 532 (nm) from the pulsed laser light therefrom and output the same. The linear beam generating unit 2
The linear beam light is irradiated in a pulse shape. The irradiation energy per pulse of the linear beam light is
When the content is 1 (mJ) or less, removal of the residual components, that is, desmearing becomes possible. This is because, as mentioned earlier, if the pulsed laser beam from the laser drilling machine is directly irradiated, the residual energy cannot be removed due to the high irradiation energy, but green light with a specific wavelength is used. By doing so, irradiation energy suitable for removing the residual component can be obtained. Of course, this green light does not affect the resin layer and the conductive layer.

In this embodiment, since the green light is visible light, the optical fiber 3 connects between the green light generator 1 and the linear beam generating unit 2.

An example of the linear beam generating unit 2 will be described with reference to FIG. Linear beam generation unit 2
Is a collimator lens 2 formed by combining a plurality of lenses.
1. Wedge prism 2 formed by combining a plurality of prisms
2. Includes a cylindrical lens 23 formed by a combination of a plurality of lenses. When the green light from the green light generating device 1 is condensed by the condensing lens 4 and introduced into the linear beam generating unit 2 via an optical fiber, the green light having a circular or rectangular cross-sectional area becomes linear in cross section. Is converted into a beam.

Next, a method of scanning a linear light beam with green light will be described with reference to FIG. In FIG. 4, a large number of processing regions 17-1 having the same area of several cm square are continuously set in a matrix on the work 17. As described above, the drilling by the laser drilling device is performed in the processing area 17-1 along the locus indicated by the broken arrow.
It is performed in order for each time.

In the first scanning method, when the drilling for all the processing areas is completed, the linear beam generating unit 2 is moved along the same locus as the drilling. This movement locus is shown by a solid line arrow in FIG. In particular, as described above, the length of the linear light beam B is set to the processing area 17-1.
Is set to be slightly longer than one side of the workpiece 17 in the step of scanning the linear beam light B from one end to the other end of the work 17 and the step of scanning while returning from the other end to one end. Scan so that the parts overlap. this is,
As shown in FIG. 2, the linear beam light B generated by the linear beam generating unit 2 is inevitably reduced in energy density at both ends thereof, so that it is necessary to reliably remove residue components. is there.

In the second scanning method, the linear beam generating unit 2 is fixed, and the workpiece 17 is moved on the XY stage 16 so that scanning can be performed with exactly the same locus as described with reference to FIG. it can. That is, the XY stage 16 can be commonly used as scanning means for the desmear apparatus.

It is necessary to adjust the irradiation energy depending on the type of the resin forming the via hole. In this case, the desmear process is performed by irradiating the same portion with the linear beam light B a plurality of times, similarly to the drilling process.
The adjustment of the irradiation energy can be performed by changing the generated pulse cycle when the linear light beam B is to be oscillated. On the other hand, when the XY stage 16 is used as a scanning means, it can be realized by changing the feed speed.

Further, if the linear beam light B is passed through the beam splitter so that only the high energy density region LB shown in FIG. 2 is extracted, the above-described overlapping scanning becomes unnecessary.

Although the time required for the desmearing process is about several seconds, in order to further reduce the time, a method in which the boring process and the desmearing process are performed in parallel may be adopted. That is, the optical system for drilling and the linear beam generating unit 2 are arranged adjacent to each other, and the drilling for one processing area is completed, and the optical system for drilling moves to the next processing area. At times, the area immediately after the processing is scanned by the linear light beam B. In this case, as shown in FIG. 5, in the last processing region 17-11 in one row, the linear light beam B is rotated by 90 degrees, and the processing region 17-
12, the linear light beam B needs to be rotated by 90 degrees.

The desmear apparatus described above is applicable to all laser drilling apparatuses which require removal of residual components, and is further disclosed in Japanese Patent Application No. 9-125422 proposed by the present inventors (Japanese Patent Application Laid-Open No. 10-58178) can be applied to a laser processing apparatus using a multi-axis galvano scanner.

[0036]

As described above, according to the present invention, it is possible to remove the residual component of the via hole without the conventional wet process in which the conditions are difficult to determine, and the time required for drilling is greatly reduced. can do.
Further, the desmear apparatus according to the present invention can be easily assembled to an existing laser drilling apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a preferred embodiment of a desmear apparatus according to the present invention.

FIG. 2 is a diagram for explaining characteristics of the size and energy density of a linear beam light generated by a linear beam generating unit in FIG. 1;

FIG. 3 is an internal configuration diagram for explaining an example of a linear beam generation unit shown in FIG.

FIG. 4 is a diagram for explaining a method of scanning a linear light beam on a processing area of a workpiece.

FIG. 5 is a diagram for explaining another example of a method of scanning a linear light beam on a processing region of a work.

FIG. 6 is a diagram showing a configuration of an example of a laser drilling apparatus to which the present invention is combined.

FIG. 7 is a diagram illustrating a configuration of the XY scanner illustrated in FIG. 6;

[Description of Signs] 1 Green light generating device 2 Linear beam generating unit 3 Optical fiber 10 Laser oscillator 11 Reflection mirror 13 Mask 14 XY scanner 14-1, 14-2 Galvano mirror 15 Processing lens 16 XY stage 17 work

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H05K 3/46 H05K 3/46 X // B23K 101: 42 B23K 101: 42

Claims (10)

(57) [Claims] A laser beam from a laser oscillator in a laser drilling device is applied to a resin layer formed on a metal film to form a via hole in the resin layer, and a residual component remaining in the via hole is removed. A desmear device for removing, a green light generating device for generating green light, a linear beam generating unit for converting the generated green light into a linear beam light, and the linear beam light Scanning means for scanning an area in which the via hole is formed, for a laser drilling apparatus. 2. The desmear device according to claim 1, wherein
The laser processing apparatus is for performing a drilling process for each of a plurality of processing regions having a size sufficiently smaller than the predetermined size set on a mother plate having a predetermined size for each processing region. A desmear apparatus for a laser drilling apparatus, wherein a length of the light beam is set to be longer than one side of the processing area. 3. The desmear device according to claim 2, wherein
The green light generator extracts and outputs a second harmonic having a wavelength of 532 (nm) from a pulsed laser beam from a YAG laser oscillator, and the linear beam generating unit includes the linear beam generator. A desmear apparatus for a laser drilling apparatus, which irradiates a pulsed light beam. 4. The desmear device according to claim 3, wherein
A desmear device for a laser drilling device, wherein the irradiation energy per pulse of the linear beam light is 1 (mJ) or less. 5. The desmear device according to claim 4, wherein
A desmear device for a laser drilling device, wherein the green light generating device and the linear beam generating unit are connected by an optical fiber. 6. The desmear device according to claim 2, wherein
A desmear apparatus for a laser drilling apparatus, wherein the scanning means scans the base plate by oscillating the linear beam light. 7. The desmear device according to claim 2, wherein
The laser drilling apparatus includes an XY stage for mounting the base plate and moving the mother plate in the X-axis direction and the Y-axis direction, and using the XY stage as the scanning unit. Desmear device for processing equipment. 8. The desmear device according to claim 2, wherein
A desmear apparatus for a laser drilling apparatus, wherein the scanning means performs scanning so that a part of a scanning area adjacent to each other overlaps. 9. A desmear method for removing a residue component remaining in a via hole formed by irradiating a resin layer formed on a metal film with a laser beam, wherein a green light beam having a linear cross section is used. A desmear method comprising: converting light into light; and performing desmearing by scanning the linear beam light in an area where the via hole is formed. 10. The desmear method according to claim 9, wherein at least one via is provided in each of a plurality of processing regions having a size sufficiently smaller than the predetermined size set on a mother plate having a predetermined size. A hole is formed, and the length of the linear beam light is set to be longer than one side of the processing region, and scanning of the linear beam light overlaps a part of the scanning regions adjacent to each other. And a desmear method.