JPH11342490A - Desmear device for laser piercing equipment, and desmear method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a desmear device for removing a residue component of a via hole without a wet process. SOLUTION: This invention relates to a desmear device for removing a residue component left in a via hole formed on a metallic film of a work 17 by means of a laser piercing equipment. This desmear device comprises a laser light generator 1 for generating a laser light having a predetermined wavelength required for removing the residue component, a polygon mirror 2 for scanning the generated laser light across overall length of the work width direction, and a stage 3 for moving the work in a direction perpendicular to the scanning direction of the laser light at right angle.

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 via holes in a printed wiring board, particularly a multilayer printed wiring board using a laser beam. The present invention relates to a desmear apparatus and a desmear method for removing.

[0002]

2. Description of the Related Art In response to the demand for higher density of printed wiring boards in accordance with the miniaturization and high-density mounting of electronic devices, recently, multilayer printed wiring boards in which a plurality of printed wiring boards are stacked have appeared. In such a multilayer printed wiring board, it is necessary to electrically connect conductive layers (copper boards) between printed wiring 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 wiring 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 even if the same laser beam is irradiated 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 a laser drilling machine.

[0010]

According to the present invention, there is provided a laser drilling machine which irradiates a resin layer formed on a metal film on a work with a laser beam from a laser oscillator to form a residue remaining in a via hole formed on the metal film. A desmear device for removing a component, a laser light generating device for generating a laser beam having a predetermined wavelength necessary for removing the residual component, and A scanning means for scanning over the entire length in the width direction, and a moving means for moving the work in a direction perpendicular to the scanning direction of the laser beam.

It is preferable that the scanning means is a polygon mirror.

The laser light generator has a wavelength of 19.
A gas laser oscillator or a solid-state laser oscillator in a range from 2 (nm) to 650 (nm) is included.

In particular, YA is used as the solid-state laser oscillator.
It is preferable to use one that extracts and outputs a second harmonic having a wavelength of 532 (nm) from pulsed laser light from a G or YLF laser oscillator.

When the desmearing apparatus is incorporated in the laser drilling apparatus, the laser drilling apparatus has an XY stage for mounting the workpiece and moving the workpiece in the X-axis direction and the Y-axis direction. The X-
The Y stage can be used also as the moving means.

A desmear method according to the present invention is a desmear method for removing a residual component remaining in a via hole formed by irradiating a resin layer formed on a metal film in a work with a laser beam from a laser oscillator. Desmearing is performed by irradiating laser light having a wavelength of 192 (nm) to 650 (nm).

[0016]

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. 2, 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 a 90 ° angle 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 the 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.

Referring to FIG. 3, 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, drilling is performed by irradiating 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.
Although the area is m square, the size of the work 17 is about 50 (cm) × 60 (cm) as described later. For this reason, an area determined by the scanning range of the XY scanner 14 is set in the work 17 in a matrix as a processing area. 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 built in or combined with the laser drilling apparatus as described above, but is not particularly limited by the type of laser oscillator.

A preferred embodiment of the present invention will be described with reference to FIG. First, a laser drilling device and a separate type desmear device will be described. This desmear apparatus is for removing a residual component remaining in a via hole of the work 17 formed by the laser drilling apparatus described with reference to FIG. 2, and is a predetermined method required for removing the residual component. A laser light generator 1 for generating laser light having a wavelength, a polygon mirror 2 for scanning the generated laser light over the entire length of the work 17 in the width direction, and a direction perpendicular to the laser light scanning direction; That is, it has a stage 3 for moving in a direction perpendicular to the plane of the drawing. In addition, folding mirrors 4 and 5 are arranged to guide the laser light generated by the laser light generating device 1 to the polygon mirror 2, and a mask 6 for defining the beam diameter of the laser light is arranged. Are not the gist of the present invention and can be arbitrarily changed.

The laser light generator 1 has a wavelength of 192.
Either a gas laser oscillator or a solid-state laser oscillator in a range from (nm) to 650 (nm) may be used. For example, a solid-state laser oscillator that extracts and outputs a second harmonic having a wavelength of 532 (nm) from pulsed laser light from a YAG or YLF laser oscillator is suitable. This is because, as a result of experiments, it has been confirmed that laser light of this wavelength has the highest desmear effect. More specifically, the wavelength is 300 (nm) to 5
It is preferably 50 (nm), and the laser oscillator may be a Q-switched YAG or YLF laser, an Ar, Cu vapor laser, or the like. The energy density on the irradiation surface may be about 0.05 to 1 J / cm ² . Of course, the laser beam used in the present embodiment does not affect the resin layer other than the via holes.

As described above, the laser beam for desmear removal is scanned by the polygon mirror 2 over the entire length of the work 17 in the width direction.
By moving the workpiece 17 in a direction perpendicular to the scanning direction, the laser beam for desmear removal can be apparently applied to the entire surface of the workpiece 17. For this purpose, the moving speed of the stage 3 is set to be lower than the scanning speed of the polygon mirror 2. In addition,
In many cases, a servo motor or a step motor is used as a drive source of the stage 3.
Can be moved stepwise each time one scan by the polygon mirror 2 is completed. In any case, the laser beam for desmear removal is applied to the work 17.
By irradiating the entire surface of the via hole, residual components remaining at the bottom of the via hole can be efficiently removed. In addition, the polygon mirror 2 can normally scan in a range of several tens of cm, and can sufficiently cope with the size of the work 17 described above.

Next, a case where the desmear apparatus according to the present invention is incorporated in a laser drilling apparatus as described with reference to FIG. 2 will be described. As described in FIG. 2, the laser drilling apparatus includes the XY stage 16 on which the work 17 is mounted and moved in the X-axis direction and the Y-axis direction.
When incorporated in such a laser drilling apparatus, for example, the polygon mirror 2 is arranged on the left side of the processing lens 15 shown in FIG. The XY stage 16 can be used in place of the stage 3 described with reference to FIG.

By incorporating the work 1 in this manner, the work 1
7 is completed, the X-Y is scanned while the polygon mirror 2 scans the laser beam for desmear.
By moving the stage 16 in a direction perpendicular to the scanning of the polygon mirror 2, that is, in one of the X-axis direction and the Y-axis direction, it is possible to irradiate the entire surface of the work 17 with a laser beam for desmear removal.

In order to reduce the time required for the desmear processing, a method of making the boring processing and the desmear processing in parallel may be adopted. That is, the optical system for drilling including the XY scanner 14 and the processing lens 15 and the polygon mirror 2 are arranged adjacent to each other, and the drilling for a certain processing area is completed, and the optical system for drilling is completed. Is moved to the next processing area, the area immediately after the processing is scanned by the laser beam for desmearing. Polygon mirror 2
Scan range may be about several cm. Of course, it is also possible to irradiate a laser beam for desmearing immediately after drilling, and to perform desmearing almost simultaneously, instead of in parallel for each processing region.

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. The present invention can also be applied to a laser processing apparatus using a multi-axis galvano scanner as described above.

[0027]

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, and in this case, space can be saved.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of an example of a laser drilling apparatus to which the present invention is combined.

FIG. 3 is a diagram illustrating a configuration of an XY scanner illustrated in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light generator 2 Polygon mirror 3 Stage 4, 5 Folding mirror 6, 13 Mask 10 Laser oscillator 11 Reflection mirror 14 XY scanner 14-1, 14-2 Galvano mirror 15 Processing lens 16 XY stage 17 Work

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 3/46 H05K 3/46 X

Claims (6)

[Claims] 1. A desmear apparatus for removing a residual component remaining in a via hole formed by irradiating a resin layer formed on a metal film on a workpiece with a laser beam from a laser oscillator in a laser drilling apparatus. And
A laser light generator for generating a laser light having a predetermined wavelength necessary for removing the residual component, a scanning unit for scanning the generated laser light over the entire length in the width direction of the work, and Moving means for moving the work in a direction perpendicular to the scanning direction of the laser beam, the desmearing device for a laser drilling device. 2. The desmear device according to claim 1, wherein
A desmear device for a laser drilling device, wherein the scanning means is a polygon mirror. 3. The desmear device according to claim 1, wherein
The laser light generator has a wavelength of 192 (nm) to 65
A desmear device for a laser drilling device, comprising a gas laser oscillator or a solid-state laser oscillator in a range up to 0 (nm). 4. The desmear device according to claim 3, wherein
As the solid-state laser oscillator, a wavelength of 532 (n) is obtained from pulsed laser light from a YAG or YLF laser oscillator.
A desmearing device for a laser drilling device, characterized in that a device for extracting and outputting the second harmonic of m) is used. 5. The desmear device according to claim 1, wherein
The desmear apparatus is incorporated in the laser drilling apparatus, and the laser drilling apparatus includes an XY stage for mounting the workpiece and moving the workpiece in the X-axis direction and the Y-axis direction. -A desmear device for a laser drilling device, wherein a Y stage is also used as the moving means. 6. A desmear method for removing a residual component remaining in a via hole formed by irradiating a resin layer formed on a metal film in a work with a laser beam from a laser oscillator, wherein the wavelength is 192. (Nm) to 650
A desmear method comprising irradiating a laser beam in a range up to (nm) to perform desmear.