JP3175006B2 - Laser processing apparatus and processing method - 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 processing apparatus and a processing method for piercing a substrate by irradiating a substrate with a pulsed laser beam from a laser oscillator.

[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, multilayer printed wiring boards in which a plurality of printed wiring boards are stacked have recently been provided. . In such a multilayer printed wiring board, it is necessary to electrically connect conductive layers (copper foils) between printed wiring boards stacked one above another. In such a connection, a hole called a via hole that reaches a lower conductive layer is formed in an insulating layer (usually, a polymer such as polyimide or epoxy resin) of a printed wiring board, and conductive plating is performed inside the hole. This is achieved by:

In order to form such a via hole, a laser has recently been used. A laser processing apparatus using a laser generates, for example, a pulsed laser beam with a CO ₂ gas laser oscillator and guides the pulsed laser beam to a mask for shaping the cross-sectional shape of the laser beam. The laser beam formed by the mask is incident on a scanning system called a galvano scanner, and is irradiated on a printed wiring board as a substrate to be processed through an fθ lens. As shown in FIG. 7, the galvano scanner includes a first galvanometer mirror 71 for oscillating the laser beam in the X-axis direction, and a second galvanometer for oscillating the laser beam from the first galvanometer mirror 71 in the Y-axis direction. And two galvanometer mirrors 72.

[0004]

By the way, the galvano scanner is controlled based on a predetermined processing pattern, and oscillates a laser beam within a scanning range (for example, a square area having a side of several tens of cm). The holes are drilled one by one by positioning and irradiating the position. Therefore, the processing area on the substrate to be processed is determined by the scanning range of the galvano scanner. Further, the speed of drilling is limited mainly by the response speed of the galvanomirror, so there is a limit.

Accordingly, an object of the present invention is to provide a laser processing apparatus and a processing method capable of improving the speed of drilling.
Is to provide a law .

[0006]

SUMMARY OF THE INVENTION The present invention, in the laser processing apparatus Les Zabimu from a laser oscillator is irradiated to the processing substrate performs drilling, continuously variable light intensity steplessly light amount of the laser beam An adjustment mechanism is provided, and after the light amount stepless adjustment mechanism, a callide reflector is further provided.
The substrate to be processed is provided with a laser beam from the kaleid reflector.
Hole pattern for drilling multiple holes in the irradiation area of the laser beam
By irradiating a laser beam through a mask having a processing pattern such that a plurality of holes can be formed at the same time ,
The body forms a hollow space between them, and the hollow space
It is characterized by being assembled so as to have a predetermined sectional shape .

[0007] The laser processing apparatus also includes
The cross-sectional shape of the laser beam from the
Providing a reduction projection optical system for projecting light onto the mask;
Is formed with a plurality of holes having a desired hole diameter and pitch.
Contact mask or conformal mask
And features.

According to the present invention, there is also provided a laser oscillator.
Drilling by irradiating the substrate with the laser beam
A laser processing method, comprising:
The beam, the light amount of the laser beam is continuously variable
The light enters the light intensity stepless adjustment mechanism, and the light intensity stepless adjustment mechanism
These laser beams are further incident on a callide reflector, and
The laser beam from the kaleid reflector is adjusted to the desired hole diameter and
Contact mask in which a plurality of holes having latches are formed
Or, reduce the projection onto a conformal mask to
Multiple holes in the laser beam irradiation area
The work substrate is illuminated so that a hole pattern for drilling is included.
To drill multiple holes at the same time.
A laser processing method is provided.

[0009]

[0010]

[0011]

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a laser processing apparatus according to the present invention. In FIG. 1, here, TEA (Transverse
ly Excited Atmospheric pr
essure) CO ₂ gas laser oscillator (hereinafter referred to as laser oscillator) is used. The pulsed laser beam emitted from the laser oscillator 10 enters the laser light stepless adjustment mechanism 13 via the first and second reflecting mirrors 11 and 12. The laser light stepless adjustment mechanism 13 includes a stop mechanism and a stepping motor for driving the stop mechanism, and adjusts the amount of incident laser light based on the principle of a stop mechanism of a camera. That is, the laser beam incident on the laser light amount stepless adjustment mechanism 13 usually has a cross section of 11 mm.
It is a rectangle having a size of about mm × 9 mm. The laser light amount stepless adjustment mechanism 13 cuts out the laser beam having a rectangular cross section mechanically partially. The energy of the cut laser beam is variable in relation to the cut area, and this value is variable in relation to the rotation amount of the stepping motor.

The laser beam from the laser light stepless adjustment mechanism 13 enters the uniform optical system 20. Uniform optical system 2
Numeral 0 includes an incident condenser lens 21 having a focal length f1 and a callide reflecting mirror 22. Although the structure of the uniform optical system 20 will be described later, a laser having a single-mode or multi-mode intensity distribution is made incident on the kalide reflecting mirror 22 by the incident condenser lens 21, and the inside of the This is for making the energy intensity distribution of the laser beam uniform using multiple reflection. The laser beam that has exited the uniform optical system 20 is reduced and projected by the imaging lenses 14 and 15 having the focal lengths f2 and f3, is shaken by the above-described scanning system 16 using a galvano scanner, and is XY.
The light is applied to the substrate 17 on the stage 30.

Here, as described above, the scanning system 16
A first galvanomirror 16-1 for causing the laser beam to oscillate in the X-axis direction with respect to a processing area of the processing target substrate 17 on the XY stage 30, that is, a scanning area;
The laser beam from the first galvanomirror 16-1 is changed to Y
Second galvanometer mirror 16-2 for swinging in the axial direction
And The XY stage 30 is movable in the X-axis direction and the Y-axis direction. When the processing of one processing area of the processing target substrate 17 is completed, the next processing of the processing target substrate 17 is performed in the scanning area by the scanning system 16. The processed substrate 17 is moved so that the region is located.

Referring to FIG. 2, the callide reflector 22 will be described. The callide reflector 22 includes four rods 22-1 to 22-4 each having a rectangular cross section made of oxygen-free copper,
They are combined so that a hollow portion 22-5 is formed between them. These are assembled with bolts 22-6. In particular, the hollow portion 22-5 serving as a passage for the laser beam
Has a square cross-sectional shape and is mirror-finished so that its inner surface becomes a reflecting mirror.

According to such a kalide reflecting mirror 22,
The incident laser beam is multiply reflected in the hollow portion 22-5, and as a result, the energy intensity distribution of the laser beam is made uniform. The uniformity of the energy intensity distribution depends on the size of the cross-sectional shape of the incident laser beam,
, The size of the cross-sectional shape of the hollow portion 22-5, and the total length of the hollow portion 22-5. Hollow part 22-
As the total length of 5 is longer, the number of multiple reflections increases, and the uniformity improves. In this embodiment, the total length of the hollow portion 22-5 is set to a length at which multiple reflections are performed at least three times.
Since the loss increases as the number of multiple reflections increases, the length is preferably such that reflection is performed about several times.

[0017] As a material for Callide reflector 22, in the case of CO ₂ laser oscillator, in addition to beryllium free copper are considered. On the other hand, when a YAG laser oscillator or an excimer laser oscillator is used, a glass material such as quartz can be used.

By using such a uniform optical system 20, the energy intensity distribution of the laser in the laser beam irradiation area is made uniform, and in the case of drilling a printed wiring board, the laser light intensity stepless adjustment mechanism 13 is used. Along with the adjustment of the beam energy, a laser beam having a uniform energy intensity distribution can be irradiated. This is effective in the following points. That is, a conductive layer made of copper foil is usually formed on the lower surface of the printed wiring board. In the conventional laser processing apparatus, the energy intensity distribution of the laser beam in the laser irradiation area is a Gaussian distribution, and the energy is larger toward the center of the laser beam. As a result, there is a problem that the conductive layer is easily damaged in addition to making holes in the printed wiring board. On the other hand, according to this embodiment, the energy of the laser beam in the laser irradiation area is adjusted and the energy intensity distribution is uniform, so that the conductive layer is not damaged.

In the laser processing apparatus of this embodiment, the maximum spread angle of the laser beam from the laser
mrad and the focal length f1 of the incident condenser lens 21 is 120 mm, the spot size of the laser beam condensed at the entrance of the kaleid reflector 22 has a maximum diameter of 1 mm.
20 × 5 = 600 μm. For this reason, the size of the cross-sectional shape of the hollow portion 22-5 of the callide reflector 22 is 900
μm × 4500 μm. The uniformized image of the laser beam at the exit end of the kalide reflecting mirror 22 is 900 μm
It becomes a rectangle having a size of × 4500 μm. The size of the image on the laser beam irradiation area, that is, the size on the processing surface is reduced to 1/3.
The ratio of the focal lengths f2 and f3 of the imaging lenses 14 and 15 is set to 3: 1 in order to project the image at a reduced size. In this embodiment, the focal length f2 is 600 mm, and the focal length f3 is 2
The distance was set to 00 mm, and the distance from the exit end of the callide reflecting mirror 22 to the imaging lens 14 was set to 600 mm.

As a result, the spot size of the laser beam on the processing surface is 300 μm × 1500 μm, and the energy intensity distribution is uniform.

The present invention is characterized in that a plurality of holes can be formed at once by using a laser beam having a uniform energy intensity distribution and having a larger spot size than the conventional one. This will be described below.

Referring to FIG. 3, a case where a green sheet is punched will be described. In recent years, with the increase in density and integration of electronic components, the size and pitch of holes required for a green sheet have been reduced. Hole size is 100μm in diameter, pitch is 600μ on short pitch side
m, a green sheet having a long pitch side of 1200 μm and a short pitch side having a maximum width of 150 mm is provided. Of course, this is only an example, and the short pitch side is 800 μm or 100 μm depending on the type (product) of the green sheet.
0 μm, long pitch side is 1600 μm or 2000
μm.

In the present embodiment, a contact mask method is adopted for drilling the green sheet as described above. this is,
As shown in FIG. 4, a contact mask 200 having a desired hole diameter and pitch is set on the green sheet 100,
By irradiating the laser beam having the above-mentioned spot size through the contact mask 200, the required hole diameter and pitch are realized. 101 is a conductive layer.

As shown in FIG. 5, when drilling a green sheet as shown in FIG. 3 with the spot size described with reference to FIG. 1, that is, a laser beam of 300 μm × 1500 μm, three holes are drilled at a time. You can see what can be done.

As a contact mask, a material that reflects laser light well and has good thermal conductivity, for example, beryllium copper or oxygen-free copper was used, and necessary through holes were formed by etching.

The above description is an example in which three holes are processed at one time. However, even with a green sheet as shown in FIG. It is possible to provide a laser processing apparatus for simultaneously processing more than one hole.

The present invention can be applied not only to the contact mask system but also to a conformal mask system as shown in FIG. In the conformal mask method, a printed wiring board 110, which is a substrate to be processed, and a mask 210 are integrated in advance. 111 is a conductive layer. Therefore, by dividing the irradiation area on the mask 210 into areas corresponding to the spot size of the laser beam and sequentially irradiating the laser beam to each area with a galvano scan, the size and pitch of the holes are not constant. Even in this case, a plurality of holes that fall within the spot size of the laser beam can be simultaneously processed.

In the above description, the drilling is performed by one shot of the laser beam. However, in the conventional drilling, the drilling is usually performed in 2 to 4 shots. It goes without saying that it can be applied. Further, the laser oscillator is not limited to the TEA-CO ₂ laser oscillator, and any laser oscillator such as an excimer laser oscillator and a YAG laser oscillator can be used.

[0029]

As described above, the laser processing apparatus according to the present invention can perform a plurality of holes at the same time, so that the processing speed is dramatically improved. In addition, since the adjustment of laser energy and the intensity distribution in the laser beam irradiation region can be made uniform, it is particularly suitable for drilling a printed wiring board on which a conductive layer of copper foil is formed. That is, drilling can be performed without damaging the conductive layer.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic configuration of a laser processing apparatus according to the present invention.

FIG. 2 is a front view for explaining the structure of a carbide reflector in the uniform optical system shown in FIG. 1;

FIG. 3 shows an example of a substrate to be processed used in the present invention.
It is the figure which showed the example of arrangement | positioning of the hole formed there in the case of a green sheet.

FIG. 4 is a cross-sectional view for explaining drilling by a contact mask method to which the present invention is applied.

5 is a diagram for explaining the relationship between the size of a laser beam obtained by the present invention on a processing surface and the holes shown in FIG. 3;

FIG. 6 is a cross-sectional view for explaining drilling by a conformal mask method to which the present invention is applied.

FIG. 7 is a diagram showing a schematic configuration of a galvano scanner.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 laser oscillator 11, 12 reflecting mirror 13 laser light stepless adjustment mechanism 14, 15 imaging lens 16 scanning system 16-1, 16-2 first and second galvano mirrors 17 substrate to be processed 20 uniform optical system 21 for incidence Condenser lens 22 Callide reflector 30 XY stage

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI // H01S 3/00 H01S 3/00 B (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 26/00- 26/18 H05K 3/00 H05K 3/46 H01S 3/00

Claims (3)

(57) [Claims] 1. A laser processing apparatus Les Zabimu from a laser oscillator is irradiated to the processing substrate performs drilling, the laser beam continuously variable light intensity stepless adjusting mechanism the quantity provided for, the amount Mu After the step adjustment mechanism, add a callide reflector.
The substrate to be processed is provided with a laser from the carbide reflector.
Hole pattern for a plurality of drilling the irradiation area of the beam including
By irradiating a laser beam through a mask having a processing pattern such that a plurality of holes can be made at the same time , furthermore, the above-mentioned carbide reflector has a plurality of rod-like members.
A hollow portion is formed between the hollow portions, and the hollow portion has a predetermined sectional shape.
A laser processing apparatus characterized in that the laser processing apparatus is assembled so as to have: 2. A laser processing apparatus according to claim 1, wherein a sectional shape of a laser beam from said carbide reflector is changed.
Projection optical system for reducing and projecting the image on the mask
And the mask has a hole having a desired hole diameter and pitch.
A contact mask or a plurality of
A laser processing apparatus characterized by being a mask . 3. A laser beam from a laser oscillator is applied.
Laser processing method for drilling by irradiating
There are, the laser beam from the laser oscillator, the Rezabi
Light intensity of the beam is incident on the continuously variable light intensity adjustment mechanism
Then, the laser beam from the light amount stepless adjustment mechanism is further
Incident on the reflector , and the laser beam from the reflector is adjusted to a desired hole diameter.
Contact mass in which a plurality of holes having a pitch are formed
To a color or conformal mask.
Multiple holes in the irradiation area of the laser beam from the mirror
In order to include a hole pattern for drilling,
Simultaneous drilling of multiple holes by irradiation
A laser processing method characterized by the above-mentioned.