JP2005118831A - Laser beam machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the aperture ratio of the inner peripheral surface of perforating subjected to irradiation with a laser. <P>SOLUTION: The laser beam machine 10 consists of a laser oscillator 12, reflecting mirrors 14, 16 and 18 which reflect the laser beam 13 emitted from the laser oscillator 12, an imaging lens 19, a light quantity adjusting unit 20 which is disposed between the reflecting mirror 16 and the reflecting mirror 18, an X-Y stage 22 which moves a work 21 to be worked in an X-Y direction, and a controller 23 which controls the light quantity adjusting unit 20. The light quantity adjusting unit 20 consists of a rotary mask 24 which is disposed to exist in the optical path of the laser beam 13, a supporting mechanism 26 which exchangeably supports the rotary mask 24 and a motor 28 which rotationally drives the rotary mask 24. The light quantity adjusting unit 20 limits the light quantity of the laser beam 13 by rotating the rotary mask 24, thereby controlling a light intensity distribution (a beam profile) to an arbitrary level. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser beam machine, and in particular, to improve the aperture ratio (ratio of hole inlet to hole outlet) of a hole processed when processing a minute hole (via hole processing) on a substrate to be processed (workpiece). The present invention relates to a laser beam machine configured as described above.

  In recent years, in response to the demand for higher density of printed wiring boards accompanying downsizing of electronic devices and higher density mounting, development of multilayer printed wiring boards in which a plurality of printed wiring boards are laminated has been promoted. In such a multilayer printed wiring board, as a method of electrically connecting conductive layers (copper foils) between printed wiring boards stacked one above the other, an insulating layer of the printed wiring board (usually polyimide, epoxy resin, etc.) In this polymer, a hole called a via hole reaching the lower conductive layer is formed, and a conductive plating is applied to the inside of the hole.

As a processing machine for forming such a via hole, a laser processing machine is used. For example, a pulsed laser beam is used in a CO ₂ gas laser oscillator.

A pulsed laser beam emitted from a CO ₂ gas laser oscillator as a laser generation source is incident on a laser beam amount stepless adjustment mechanism, the amount of light is adjusted, and is focused on a workpiece processing point by an imaging lens. The laser beam amount stepless adjustment mechanism includes a diaphragm mechanism and a stepping motor that drives the diaphragm mechanism. Based on a principle similar to that of a camera diaphragm mechanism, the laser beam quantity stepless adjustment mechanism controls a part of the laser beam to cut out the incident laser. The amount of light is adjusted (see, for example, Patent Document 1).

  Further, the laser beam from the laser beam amount stepless adjustment mechanism is irradiated onto the workpiece via a uniform optical system (incident condensing lens, kaleidoreflector). In the uniform optical system, the incident condensing lens makes the light incident on the kaleidoreflector, and the kaleidoreflector uses the multiple reflection inside thereof to make the energy intensity distribution of the laser beam uniform. As a control technique for controlling the light intensity distribution (beam profile) of the laser beam, for example, there is a homogenizer.

  Then, the laser beam whose energy intensity distribution is made uniform by the uniform optical system is shaken by a scanning system using a galvano scanner, and is irradiated onto a substrate to be processed (work) on an XY stage.

The substrate to be processed is provided with a mask for shaping the cross-sectional shape of the laser beam. A mask having a hole having the same shape as the processed shape is placed on the green sheet, and the laser beam passes through the mask. The desired hole diameter is formed.
JP-A-10-323788

  However, in the laser processing machine using the mask image method as described above, when the light intensity distribution of the laser beam is Gaussian (hanging), the light intensity distribution (beam profile) at the axis of the laser beam is the most. Even if the laser beam diameter is regulated by the hole diameter of the fixed mask, the light intensity distribution near the axis of the laser beam that has passed through the fixed mask is the strongest. Since there is no change, the inner circumference of the hole processed (via hole processing) becomes tapered, and there is a problem that there is a limit in improving the aperture ratio of the hole processing.

  Then, an object of this invention is to provide the laser processing machine which solved the said subject.

The invention according to claim 1 is a laser having a laser oscillator, a light amount adjusting means for adjusting a light amount of a laser beam from the laser oscillator, and an optical system for guiding the laser beam from the light amount adjusting means to a processing position of a workpiece. In the processing machine,
The light quantity adjusting means is provided with light quantity control means for controlling the light quantity so as to control the intensity distribution of the laser beam applied to the workpiece in an arbitrary pattern.

  According to a second aspect of the present invention, the light amount control means includes an opening that is rotatably provided so that an optical axis of the laser beam is a center of rotation, and is formed so as to pass a part of the laser beam. A rotating mask and a rotation driving means for rotating the rotating mask are provided, and the intensity distribution of the laser beam applied to the workpiece is controlled by the rotation of the rotating mask.

  The invention according to claim 3 is characterized in that the rotary mask is formed such that an opening area of the opening is set to an arbitrary size.

  According to a fourth aspect of the present invention, the rotary mask is formed so that the opening has an arbitrary shape.

  The invention according to claim 5 is characterized in that the rotary mask has openings composed of a plurality of holes or a plurality of slits, and the number of the plurality of holes or the plurality of slits is arbitrarily set.

  According to a sixth aspect of the present invention, the light quantity control means has a storage portion in which the rotary mask is stored in a replaceable manner, and an arbitrary rotary mask is selected from a plurality of rotary masks formed with different openings. It is selectively attached to the storage part.

  According to the first aspect of the present invention, the light intensity distribution (beam profile) of the laser beam irradiated onto the workpiece is controlled by controlling the light amount so as to control the intensity distribution of the laser beam irradiated onto the workpiece into an arbitrary pattern. ) Can be controlled to be uniform, and the aperture ratio of the inner peripheral surface of the hole processed by laser irradiation can be improved.

  According to the second aspect of the present invention, the rotation of the rotary mask having an opening formed so as to allow a part of the laser beam to pass is rotated so that the optical axis of the laser beam becomes the center of rotation. The amount of light can be controlled so that the intensity distribution is uniform, and the aperture ratio of the inner peripheral surface of the hole processed by laser irradiation can be improved.

  According to the invention described in claim 3, since the opening area of the opening is set to an arbitrary size, the amount of light is controlled so that the light intensity distribution of the laser beam becomes uniform according to the size of the opening area of the rotary mask. It is possible to improve the aperture ratio of the inner peripheral surface of the hole processed by laser irradiation.

  According to the fourth aspect of the invention, since the shape of the opening is set to an arbitrary size, the amount of light is controlled so that the light intensity distribution of the laser beam becomes uniform according to the size of the opening area of the rotary mask. It is possible to improve the aperture ratio of the inner peripheral surface of the hole processed by laser irradiation.

  According to the fifth aspect of the present invention, since the arrangement number of the plurality of holes or the plurality of slits is arbitrarily provided in the rotating mask, the distribution pattern of the plurality of holes or the plurality of slits provided in the rotating mask is selected. The amount of light can be controlled so that the light intensity distribution of the laser beam becomes uniform, and the aperture ratio of the inner peripheral surface of the hole processing irradiated with the laser can be improved.

  According to the invention described in claim 6, in order to selectively mount an arbitrary rotating mask among a plurality of rotating masks formed in patterns with different openings, laser irradiation is performed using a rotating mask according to processing conditions. The aperture ratio of the inner peripheral surface of the drilled hole can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a laser beam machine according to the present invention.
As shown in FIG. 1, the laser processing machine 10 includes a laser oscillator 12, reflection mirrors 14, 16, and 18 that reflect a laser beam 13 emitted from the laser oscillator 12, an imaging lens 19, and a reflection mirror 16. A light amount adjustment unit 20 provided between the reflection mirror 18, an XY stage 22 that moves a workpiece substrate (workpiece) 21 irradiated with reflected light from the reflection mirror 18 in the XY direction, and a light amount adjustment unit 20. It is comprised from the control apparatus 23 to control.

  The light quantity adjustment unit 20 includes a rotary mask 24 as a light quantity control unit provided so as to be positioned in the optical path of the laser beam 13, a support mechanism 26 that supports the rotary mask 24 in a rotatable and replaceable manner, and the rotary mask 24. And a motor (rotation drive means) 28 for rotationally driving the motor. The light intensity adjustment unit 20 limits the light intensity by rotating the rotary mask 24 as will be described later so that the light intensity distribution of the laser beam 13 is changed from a Gaussian shape (a hanging shape) to a rectangular shape. The distribution is made uniform by the beam diameter. The motor 28 is controlled in rotation speed by the controller 23 and is driven to rotate in synchronization with the laser beam emitted from the laser oscillator 12.

  The rotational speed of the rotary mask 24 is set according to conditions such as the frequency and output of the laser beam, and is controlled to an arbitrary rotational speed by a control signal from the control device 23.

  The rotating mask 24 adjusts the light amount of the laser beam while rotating. As will be described later, the light amount of the laser beam can be changed to an arbitrary value due to the difference in the opening area and the opening pattern. Therefore, a plurality of rotating masks 24 having different opening areas and opening patterns are prepared in advance, and an arbitrary rotating mask 24 is selected according to the processing conditions and mounted on the light amount adjustment unit 20. Thereby, it becomes possible to adjust the light quantity of a laser beam to arbitrary values.

FIG. 2 is a front view of the light quantity adjustment unit 20 as seen from the axial direction. FIG. 3 is a front view for explaining an operation of opening the opening / closing door 40 of the light amount adjustment unit 20 and replacing the rotary mask 24.
As shown in FIG. 2, the rotary mask 24 has a disk 32 fixed to an end face of a frame 30 formed in a ring shape. A minute light amount controller 34 is provided at the center of rotation of the disk 32. The light quantity control unit 34 has a diameter smaller than the beam diameter of the laser beam 13. For example, an arbitrary pattern described later is etched on a copper plate disk 32.

  In the support mechanism 26, four guide rollers 38a to 38d are provided at intervals of 90 degrees on the inner periphery of a cylindrical housing (housing portion) 36. The rotary mask 24 is restricted in its axial position by fitting the outer periphery of the frame 30 into the annular groove 39 of the guide rollers 38a to 38d, and its radial position is also restricted. Thereby, the light quantity control unit 34 provided at the rotation center of the rotary mask 24 is rotatably held in the optical path of the laser beam 13.

  An opening / closing door 40 that is opened and closed when the rotary mask 24 is replaced is provided on the outer periphery of the housing 36. The open / close door 40 is rotatably supported at one end 40 a serving as a pivot point by a hinge 42, and the other end 40 b is fastened by a buckle 44 provided on the outer periphery of the housing 36.

  Further, a guide roller 38 a is rotatably supported on the inner periphery of the opening / closing door 40, and a handle 46 is provided on the outer periphery of the opening / closing door 40. Accordingly, when the buckle 44 is removed, the handle 46 is gripped and the opening / closing door 40 is opened, the guide roller 38a is separated from the rotary mask 24 and the rotary mask 24 can be replaced as shown in FIG. In the rotating mask 24, the holding force with respect to the frame 30 is released when the guide roller 38a out of the four guide rollers 38a to 38d is separated, and the restraining force in the radial direction is removed.

  Thus, the rotary mask 24 stored in the housing 36 can be pulled out from the guide rollers 38b to 38d, and another rotary mask 24 can be inserted.

  A motor 28 that rotationally drives the guide roller 38 c is provided on the inner periphery of the housing 36. The rotational driving force of the motor 28 is transmitted to the rotary mask 24 through the guide roller 38c.

Here, the configuration of the light quantity control unit 34 will be described.
FIG. 4 is an enlarged front view showing the light quantity control unit 34.

As shown in FIG. 4, the light quantity control unit 34 etched into the copper plate radiates the leaf-shaped light shielding units 48 (48 _{1 to} 48 ₈ ) radially inside the circular part 50 having a diameter smaller than the beam diameter of the laser beam 13. For example, eight-leaf light-shielding portions 48 (48 _{1 to} 48 ₈ ) are provided at intervals of 45 degrees. Between the light shielding portions 48 (48 _{1 to} 48 ₈ ), triangular openings 52 (52 _{1 to} 52 ₈ ) having two sides recessed in an arc shape are formed. Since the light quantity control unit 34 is held so that the center of rotation coincides with the center of the laser beam 13, the inner diameter of the circular portion 50 becomes the mask diameter.

The opening 52 ₍₅₂ 1 to 52 ₈₎ formed between the 8 leaf shielding portion 48 ₍₄₈ 1 to 48 ₈₎ has a smaller opening width of the center side, formed so that the opening width increases as the outer peripheral side Has been. Therefore, the amount of light of the laser beam 13 that passes through the openings 52 (52 _{1 to} 52 ₈ ) increases in the limit amount toward the center side and decreases toward the outer peripheral side.

In the present embodiment, the case where the eight light shielding portions 48 are arranged radially is illustrated, but the number of the light shielding portions 48 is not limited to this, and an arbitrary number of eight or more may be selected according to the processing conditions. You may set so that it may arrange. Furthermore, the opening area of the openings 52 (52 _{1 to} 52 ₈ ) is formed to be set to an arbitrary size. Moreover, the shape of the opening 52 (52 _{1 to} 52 ₈ ) is formed to be set to an arbitrary shape (curve).

FIG. 5 is a graph showing the light intensity distribution of the laser beam 13.
As shown in FIG. 5, the light intensity distribution (beam profile) of the laser beam 13 is a Gaussian-like (hanging-like) Gaussian distribution (normal distribution) as shown by the graph I. In the process in which the laser beam 13 passes through the light amount control unit 34, the low-level region outside the mask diameter is cut by the circular portion 50.

FIG. 6 is a graph showing the light intensity distribution that has passed through the rotating light quantity control unit 34.
As shown in FIG. 6, the light intensity distribution (beam profile) that has passed through the rotating light amount control unit 34 is centered by the light shielding unit 48 (48 _{1 to} 48 ₈ ) as shown in the graph II. The low-level region outside the mask diameter is cut by the circular portion 50 to be rectangular. In addition, since the eight light shielding portions 48 (48 _{1 to} 48 ₈ ) are provided radially from the center, the central portion of the beam has substantially the same light intensity in the radial direction, that is, the light intensity distribution (beam (Profile) is controlled to be uniform.

  As a result, when drilling holes in the substrate to be processed (work), the inner peripheral surface of the hole processed by the laser beam that has passed through the light quantity control unit 34 is not tapered, and an almost vertical inner peripheral surface penetrates. Thus, the aperture ratio of the processed holes can be improved. Therefore, for example, when drilling a circuit board, the conductive pattern formed on the substrate is prevented from being damaged, and more precise hole processing can be performed with high accuracy.

FIG. 7 is an enlarged front view showing another embodiment of the light quantity control unit.
As shown in FIG. 7, the light quantity control unit 60 includes a plurality of small holes 62 (62 _{1 to} 62 _n ) formed in a circular shape and a light shielding unit 64 excluding the plurality of small holes 62 (62 _{1 to} 62 _n ). It consists of and. The plurality of small holes 62 (62 _{1 to} 62 _n ) are provided inside the mask diameter. The plurality of small holes 62 (62 _{1 to} 62 _n ) are openings through which the laser beam passes, and the light shielding unit 64 restricts the passage of light and adjusts the amount of light. In FIG. 7, but an enlarged part of the light quantity control unit 60 are shown a small hole 62 ₍₆₂ 1 ~62 _n), the light quantity control unit 60 small hole 62 ₍₆₂ 1 ~62 _n) is It is provided all around.

Further, in the light quantity control unit 60, the number of small holes 62 (62 _{1 to} 62 _n ) arranged varies depending on the radial regions 66a to 66c, and the number of small holes 62 in the central region 66a is small. The interval between the holes 62 is large. The number of small holes 62 in the region 64b is larger than that in the region 66a, and the interval between the small holes 62 is smaller than that in the region 66a. Further, the number of small holes 62 in the region 66c is larger than that in the region 64b, and the interval between the small holes 62 is smaller than that in the region 66b.

As described above, the plurality of small holes 62 (62 _{1 to} 62 _n ) are provided such that the number of small holes 62 is smaller toward the center of the light quantity control unit 60 and the small holes 62 are denser toward the outer peripheral side of the light quantity control unit 60. ing. Therefore, the area of the light shielding unit 64 is larger toward the center of the light amount control unit 60, and the area of the light shielding unit 64 is smaller toward the outer peripheral side of the light amount control unit 60.

In the present embodiment, the case where a plurality of small holes 62 (62 _{1 to} 62 _n ) are provided has been described. However, the shape of the small holes 62 is not limited to a circle, and is, for example, a long hole shape. It is also possible to provide a plurality of slit holes (not shown) and arbitrarily set the number and arrangement pattern of the plurality of slit holes.

FIG. 8 is a graph showing the light intensity distribution that has passed through the rotating light quantity control unit 60.
As shown in FIG. 8, in the light intensity distribution (beam profile) that has passed through the rotating light quantity control unit 60, the center part of the beam is cut by the light shielding unit 64 and the circular part 50 as shown in the graph III. As a result, the low level region outside the mask diameter is cut into an inverted U shape. Further, since the small holes 62 are smaller toward the center of the light quantity control unit 60, the central portion of the beam has substantially the same light intensity in the radial direction, that is, the light intensity distribution (beam profile) is made uniform. Be controlled.

  As a result, when drilling holes in the substrate to be processed (work), the inner peripheral surface of the hole processed by the laser beam that has passed through the light quantity control unit 60 is not tapered, and an almost vertical inner peripheral surface penetrates. Thus, the aperture ratio of the processed holes can be improved. Therefore, for example, when drilling a circuit board, the conductive pattern formed on the substrate is prevented from being damaged, and more precise hole processing can be performed with high accuracy.

FIG. 9 is an enlarged front view showing another embodiment of the light quantity control unit.
As shown in FIG. 9, the light quantity control unit 70 includes a plurality of small holes 72, 74, 76 having different hole diameters and a light shielding unit 78 excluding the plurality of small holes 72, 74, 76. The plurality of small holes 72, 74, and 76 are provided inside the mask diameter. The plurality of small holes 72, 74, and 76 are openings through which the laser beam passes, and the light shielding portion 78 restricts the passage of light and adjusts the amount of light. In FIG. 9, a part of the light quantity control unit 70 is enlarged to show a plurality of small holes 72, 74, 76. Is provided.

  In the light quantity control unit 70, the number of small holes 72, 74, and 76 varies depending on the radial regions 78 a to 78 c, the number of small holes 72 in the central region 80 a is small, and the small holes 62 are provided. Has the smallest hole diameter. The number of small holes 74 in the region 80 b is larger than that in the region 80 a, and the hole diameter of the small holes 74 is larger than that of the small holes 72. Further, the number of small holes 76 in the region 78 c is larger than that in the region 80 b, and the hole diameter of the small holes 76 is larger than that of the small holes 74.

  The light amount of the laser beam passing through the rotating light amount control unit 70 is controlled so that the light intensity distribution (beam profile) is made uniform as in the second embodiment.

  The opening of the light quantity control unit is not limited to the opening shape and arrangement pattern as in the light quantity control units 34, 60, and 70 of the above-described embodiment, and other shapes and other arrangement patterns may be used. .

It is a block diagram which shows one Example of the laser processing machine which becomes this invention. It is the front view which looked at the light quantity adjustment unit 20 from the axial direction. 6 is a front view for explaining an operation of opening the opening / closing door 40 of the light amount adjustment unit 20 and replacing the rotary mask 24. FIG. It is a front view which expands and shows the light quantity control part. 3 is a graph showing a light intensity distribution of a laser beam 13; It is a graph which shows the light intensity distribution which passed the rotating light quantity control part. It is a front view which expands and shows another Example of a light quantity control part. It is a graph which shows the light intensity distribution which passed the light quantity control part 60 to rotate. It is a front view which expands and shows the other Example of the light quantity control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Laser processing machine 12 Laser oscillator 13 Laser beam 20 Light quantity adjustment unit 21 Substrate 23 Control device 24 Rotating mask 26 Support mechanism 28 Motor 30 Frame 32 Disk 34, 60, 70 Light quantity control part 36 Housing 38a-38d Guide roller 40 Opening and closing door 48 ₍₄₈ 1 to 48 _8), 64 light-shielding part ₅₂ (52 1 _{to 52} 8) opening _{62 (62 1 ~62 n),} 72,74,76 ostium 66 a to 66 c, 80 a - 80 c region

Claims (6)

A laser oscillator;
A light amount adjusting means for adjusting a light amount of a laser beam from the laser oscillator;
In a laser processing machine having an optical system for guiding a laser beam from the light amount adjusting means to a processing position of a workpiece,
A laser processing machine, wherein the light quantity adjusting means is provided with a light quantity control means for controlling a light quantity so as to control an intensity distribution of a laser beam applied to the workpiece into an arbitrary pattern. The light amount control means includes
A rotary mask that is rotatably provided so that an optical axis of the laser beam is a rotation center, and has an opening formed so as to pass a part of the laser beam;
Rotation driving means for rotating the rotation mask;
With
2. The laser beam machine according to claim 1, wherein an intensity distribution of a laser beam irradiated to the workpiece is controlled by rotation of the rotary mask.   The laser processing machine according to claim 2, wherein the rotary mask is formed so that an opening area of the opening is set to an arbitrary size.   The laser processing machine according to claim 2, wherein the rotary mask is formed so that the opening has an arbitrary shape. The rotating mask has an opening composed of a plurality of holes or a plurality of slits,
The laser processing machine according to claim 2, wherein the number of the plurality of holes or the plurality of slits is arbitrarily set. The light amount control means includes
A storage portion for storing the rotating mask in a replaceable manner;
6. The laser processing machine according to claim 1, wherein an arbitrary rotary mask is selectively attached to the storage portion from among a plurality of rotary masks formed in different patterns in the openings.

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