WO2019146110A1

WO2019146110A1 - Laser processing method

Info

Publication number: WO2019146110A1
Application number: PCT/JP2018/002755
Authority: WO
Inventors: 幸利工藤
Original assignee: 三菱電機株式会社
Priority date: 2018-01-29
Filing date: 2018-01-29
Publication date: 2019-08-01
Also published as: KR20200093067A; KR102213648B1; TW201932221A; JP6451903B1; JPWO2019146110A1; TWI669180B; CN111629857A

Abstract

There is a problem in conventional laser processing methods in that when pulse laser light continuously irradiates an outer peripheral part, a large amount of heat accumulates in a single conformal mask and thus an insulating material is selectively decomposed and eliminated so that glass cloth protrusions may easily be produced. This laser processing method, designed to implement conformal processing in which a plurality of holes are formed, solves the problem stated above and has: a first processing step for radiating laser light 1 on a region defined on the inside or outside of a first mask 30a from among a plurality of conformal masks 30a - 30f provided in conformity with the number of holes; and processing steps, different from the first processing step, for radiating laser light 1 on the inside or outside of masks 30b - 30f, differing from the first mask 30a, from among the conformal masks 30a - 30f. A processing procedure in which the first processing step and the different processing steps are carried out is repeated multiple times and the laser light 1 irradiation position is varied each time said processing procedure is repeated, to complete the processing.

Description

Laser processing method

The present invention relates to a laser processing method for performing conformal processing.

In recent years, high density mounting is possible in electronic circuit formation processes such as automotive electronic devices that require connection reliability in cold and heat environments and vibration environments, so that a conventional drill can be used as a drilling method for circuit boards. Laser processing is an alternative to processing. The laser processing method has been conventionally adopted as a method of forming a conduction hole for carrying an interlayer electrical connection of a printed wiring board. The material of the circuit board newly adopted for the on-vehicle electronic device is characterized by using, as the insulating material, a composite material in which a resin is impregnated into a glass cloth having a high glass transition temperature.

On the other hand, to remove the insulating material, it is necessary to irradiate a laser beam with high intensity as the glass transition temperature is higher. The insulating layer thickness of the substrate used in the on-vehicle electronic device is generally 100 μm or more, and a CO 2 pulse laser with high light intensity is adopted as a light source in order to efficiently remove the insulating material in the through hole portion.

JP, 2011-110598, A (page 17 and figure 1)

Conventionally, a processing method in which a pulsed laser is sequentially and successively irradiated along the outer periphery of one conformal mask using a laser scanning device is used, but if the pulse laser is continuously irradiated to the outer peripheral portion, the conformal In the outer peripheral portion of the mask, the laser beam absorbing material which has been decomposed and removed in advance to form a plasma absorbs the laser beam to be irradiated following and is retained in place, and the heat storage amount inside the insulating material in the vicinity of retention. Will increase. When the heat storage amount is increased, the glass cloth inside the insulating material is not sufficiently cooled to below the glass transition temperature, and as a result, the glass cloth is not sufficiently decomposed and removed, and the glass cloth tends to be protruded. There is a problem that balls remain.

The present invention has been made to solve the above-described problems, and has an object of efficiently forming holes by suppressing the heat storage amount inside the insulating material.

The laser processing method according to the present invention is a laser processing method in which the number of holes to be formed is a plurality of conformal processings, which is a first mask constituting a plurality of conformal masks provided corresponding to the number of holes. Processing different from the first processing step of irradiating laser light to the region defined inside or outside and the first processing step of irradiating laser light to the inside or the outside of the mask different from the first mask constituting the conformal mask The process is repeated a plurality of times of processing steps for carrying out from the first processing step to the different processing steps, and the processing is completed while changing the position to which the laser light is applied every time the processing procedure is repeated a plurality of times.

According to the present invention, focusing on any conformal mask 1 hole, the laser beam to be irradiated subsequently is to a certain degree at a position different from the generation position of the laser light absorbing material which has been decomposed and removed in advance. Since it is irradiated after the lapse of time, the laser light absorbing material diffuses with the lapse of time, the heat storage amount to one conformal mask is suppressed, and the radiation interval sufficient for cooling the glass cloth inside the insulating material to the glass transition temperature or less. As a result, the glass cloth is sufficiently decomposed and removed, and the projection of the glass cloth does not occur, and the retention of the glass ball at the bottom of the hole can be suppressed, so that the hole can be formed efficiently. .

It is a block diagram of the laser processing apparatus which shows Example 1 of this invention. It is a figure of the irradiation position of the laser beam which shows Example 1 of this invention. It is sectional drawing cut | disconnected perpendicularly | vertically with respect to the surface of the workpiece which shows Example 1 of this invention. It is a figure of the laser beam irradiation order which shows Example 1 of this invention. It is a block diagram of the laser processing apparatus which shows Example 1 of this invention. It is a figure of the irradiation position of the laser beam which shows Example 2 of this invention. It is a figure of the irradiation position of the laser beam which shows Example 3 of this invention.

Example 1
FIG. 1 is a block diagram of a laser processing apparatus showing a first embodiment of the present invention. The laser processing apparatus shown in FIG. 1 comprises a laser oscillator 2 for generating a laser beam 1 which is a pulse, an energy adjusting device 3 for adjusting the energy of the laser beam 1 and an optical scanning device 4 for deflecting the irradiation direction of the laser beam 1. And an fθ lens 5 for condensing the laser light 1. The workpiece 6 is placed on the movable table 9 so that the surface of the workpiece 6 coincides with the focal plane 7 of the fθ lens 5 or the laser light 1 is irradiated out of focus. The reference numeral 6 is disposed on a plane 8 translated from the focal plane 7 toward the movable table 9. The control device 50 controls the laser operation of the laser oscillator and controls the light scanning device 4 and the moving table 9 in order to realize the processing method shown in the first embodiment of the present invention.

The energy adjustment device 3 adjusts the energy of the laser light 1 generated by the laser oscillator 2 to a value optimum for processing, and enters the light scanning device 4 that deflects the irradiation direction of the laser light 1. The light scanning device 4 controlled by the control device 50 deflects the irradiation direction of the laser light 1 corresponding to the laser light irradiation position calculated in advance. The laser beam 1 whose laser beam irradiation position is positioned by the light scanning device 4 is incident on the fθ lens 5 and is irradiated on the workpiece 6.

FIG. 2 shows the irradiation position of the laser light 1 on the base material 10 on which the three conformal masks 30a to 30c are formed, which is the workpiece 6. Referring to FIG. 2, taking the conformal mask 30a as an example, the surface of the substrate 10 is originally covered with the surface conductor layer 16, but the surface conductor layer on the inner side of the outer peripheral portion 11 of the conformal mask 30a. 16 is removed in advance in a separate process. An outer peripheral portion 12 having a similar shape to the outer peripheral portion 11 of the conformal mask 30a is defined on the inner side of the conformal mask 30a as a laser light irradiation point 13 with the center of gravity of the conformal mask 30a as a region. The laser beam irradiation points 13 are determined so as to equally divide the lengths. Alternatively, a radial equiangular line is extended from the center of gravity of the conformal mask 30a, and an outer peripheral portion 12 similar to the conformal mask 30a is defined as an area inside the conformal mask 30a, and an intersection point with the outer periphery of the outer peripheral portion 12 is determined. The irradiation point 13 may be used. When the conformal mask is circular, the center of gravity of the conformal mask is the center of the conformal mask.

In FIG. 2, an outer peripheral portion 12 having a similar shape to the outer peripheral portion 11 of the conformal mask 30a is defined on the inner side of the conformal mask 30a as a region starting from the center of gravity of the conformal mask 30a. Alternatively, the outer peripheral portion 12 having a similar shape to the conformal mask 30a may be defined as a region, and the enlargement / reduction ratio of the outer peripheral portion 12 having a similar shape to the conformal mask 30a may be a value suitable for processing.

FIG. 3 is a cross-sectional view of each of the conformal masks 30a to 30c in FIG. The base 10 is composed of a surface conductor layer 16, an insulating layer 17 and a back surface conductor layer 19. Inside the insulating layer 17, a glass cloth 18 which is a reinforcing material of the base material 10 is contained. Reference numeral 14 denotes a laser absorbing material generated by being decomposed and removed by the laser light 1.

FIG. 4 is a view showing the order of laser beam irradiation in the case where a plurality of conformal masks exist on a substrate. For one conformal mask, four or more positions where the laser light 1 is irradiated are determined in advance, and for example, positions where the eight laser light 1 is irradiated are determined for the conformal masks 30a to 30c. ing. In the N conformal masks, when there are M laser light irradiation points in each conformal mask, there are M × N processing steps, and the m th of the n th conformal masks The laser light irradiation position of is set to k (n, m). Here, 1 ≦ n ≦ N and 1 ≦ m ≦ M. For example, in FIG. 4, the number of conformal masks 30a to 30f is 6 (N = 6), and the number of laser beam irradiation points is 8 (M = 8). The processing conditions at the time of irradiating the laser light 1 to the laser light irradiation position k (n, m) are the same. In addition, in FIG. 4, the case where the pulse irradiation number of the laser beam 1 is 1 pulse is demonstrated.

In FIG. 4, there are a total of M × N, ie, 48 laser light irradiation positions k (n, m), 1 ≦ n ≦ 6, 1 ≦ m ≦ 8, and the laser light 1 is given in the following order: Irradiate.

In the first processing step, first, laser light 1 is applied to k (1, 1) of the conformal mask 30a, which is the first mask, for one pulse. Next, as a second processing step, the laser light 1 is irradiated with one pulse to k (2, 1) of the conformal mask 30b which is a second mask different from the first mask. Further, sequentially, as the third processing step, k (3, 1) of the conformal mask 30c which is the third mask different from the first mask as the third processing step; fourth, the fourth processing step different from the first mask; As k (4, 1) and 5th processing process of conformal mask 30d which is a mask, k (5, 1) and 6th processing process of conformal mask 30e which is the 5th mask different from the 1st mask, One pulse is irradiated to k (6, 1) of the conformal mask 30 f which is a sixth mask different from the first mask.

Whenever the laser beam 1 is irradiated to one conformal mask, the laser beam 1 is most irradiated from the position where the laser beam 1 has been irradiated, each time the processing procedure for performing a series of processing steps from the first processing step to the sixth processing step is repeated. The laser beam 1 is irradiated to the remote position and the non-irradiated position of the laser light 1. First, after irradiating 1 pulse to k (6, 1) of the

conformal mask

30 f, 1 pulse of the laser light 1 is irradiated to k (1, 2) of the conformal mask 30 a as a second processing procedure. Next, the laser light 1 is applied to k (2, 2) of the conformal mask 30b for one pulse. Further sequentially, the laser beam 1 is set to k (3, 2) of the conformal mask 30c, k (4, 2) of the conformal mask 30d, k (5, 2) of the conformal mask 30e, k (5) of the conformal mask 30f. Irradiate one pulse to 6, 2).

Next, as a third processing procedure, the laser light 1 is applied to k (1, 3) of the conformal mask 30 a for one pulse. Next, the laser light 1 is irradiated to k (2, 3) of the conformal mask 30b for one pulse. Further sequentially, the laser light 1 is k (3, 3) of the conformal mask 30c, k (4, 3) of the conformal mask 30d, k (5, 3) of the conformal mask 30e, k (conformal mask 30f Irradiate one pulse to 6, 3).

Next, as a fourth processing procedure, the laser light 1 is applied to k (1, 4) of the conformal mask 30 a for one pulse. Next, the laser light 1 is irradiated to k (2, 4) of the conformal mask 30 b for one pulse. Further sequentially, the laser light 1 is k (3, 4) of the conformal mask 30c, k (4, 4) of the conformal mask 30d, k (5, 4) of the conformal mask 30e, k (c of the conformal mask 30f Irradiate one pulse to 6, 4).

Next, as a fifth processing procedure, laser light 1 is applied to k (1, 5) of the conformal mask 30a for one pulse. Next, the laser light 1 is applied to k (2, 5) of the conformal mask 30b for one pulse. Further sequentially, the laser light 1 is k (3, 5) of the conformal mask 30c, k (4, 5) of the conformal mask 30d, k (5, 5) of the conformal mask 30e, k (conformal mask 30f Irradiate one pulse to 6, 5).

Next, as a sixth processing procedure, the laser light 1 is applied to k (1, 6) of the conformal mask 30 a for one pulse. Next, the laser light 1 is applied to k (2, 6) of the conformal mask 30b for one pulse. Further sequentially, the laser light 1 is k (3, 6) of the conformal mask 30c, k (4, 6) of the conformal mask 30d, k (5, 6) of the conformal mask 30e, k (c of the conformal mask 30f Irradiate one pulse to 6, 6).

Next, as a seventh processing procedure, the laser light 1 is applied to k (1, 7) of the conformal mask 30 a for one pulse. Next, the laser light 1 is applied to k (2, 7) of the conformal mask 30b for one pulse. Further sequentially, the laser light 1 is k (3, 7) of the conformal mask 30c, k (4, 7) of the conformal mask 30d, k (5, 7) of the conformal mask 30e, k (c of the conformal mask 30f Irradiate one pulse to 6, 7).

Finally, as an eighth processing procedure, laser light 1 is applied to k (1, 8) of the conformal mask 30a for one pulse. Next, the laser light 1 is applied to k (2, 8) of the conformal mask 30b for one pulse. Further sequentially, the laser light 1 is k (3, 8) of the conformal mask 30c, k (4, 8) of the conformal mask 30d, k (5, 8) of the conformal mask 30e, k (c of the conformal mask 30f 6. Apply 1 pulse to 6, 8) to complete the processing.

The processing steps in the general case where the number of conformal masks is N and the number of laser light irradiation points is in each conformal mask will be described next.

When the nth conformal mask that emits the laser beam 1 is not the last Nth conformal mask, the mth laser beam irradiation of the nth conformal mask (1 ≦ n <N) The point is irradiated with the laser light 1, that is, after the laser light irradiation position k (n, m) is irradiated with the laser light 1, the laser light irradiation point is sequentially repeated to the laser light irradiation position k (n + 1, m) The laser beam 1 is irradiated.

The case where the nth conformal mask for emitting the laser beam 1 is the last Nth conformal mask and the mth laser beam irradiation point is not the last Mth laser beam irradiation point Of the N-th conformal mask, the m-th laser light irradiation point is irradiated with the laser light 1, that is, after the laser light irradiation position k (N, m) is irradiated with the laser light 1, the laser light irradiation point Is returned to the first conformal mask, and moved to the laser light irradiation position k (1, m + 1) to irradiate the laser light 1. When moving from the laser light irradiation position k (N, m) to the laser light irradiation position k (1, m + 1), that is, the irradiation order in the same conformal mask is paired so as to minimize the influence of heat storage. It is desirable to select angular positions sequentially.

In the case where the nth conformal mask for emitting the laser beam 1 is the last Nth conformal mask and the mth laser beam irradiation point is the last Mth laser beam irradiation point The laser beam 1 is irradiated to the Mth laser beam irradiation point of the Nth conformal mask, that is, the laser beam 1 is irradiated to the laser beam irradiation position k (N, M), and then the processing is completed. Alternatively, after the laser light irradiation position k (N, M) is irradiated with the laser light 1, the laser light irradiation position k (1, 1) is returned again, and the same processing procedure is repeated multiple times to complete the processing.

When the number of irradiation pulses of the laser light 1 is one pulse as an example, after irradiating the laser light 1 of one pulse to the laser light irradiation position k (n, m) of an arbitrary conformal mask, The laser beam 1 is irradiated to laser beam irradiation positions k (n + 1, m) belonging to different conformal masks. Moreover, if attention is paid to a certain conformal mask, after the laser light 1 is irradiated to the laser light irradiation position k (n, m) belonging to the focused conformal mask, the next laser light 1 belongs to the same conformal mask The time interval until the laser beam irradiation position k (n, m + 1) is irradiated is a time interval during which the laser beam irradiation position belonging to the other N-1 conformal masks is irradiated while changing the position one pulse at a time Is the same as

The focused conformal mask is again irradiated with the laser light 1 after the time when one processing procedure is completed, but the laser light irradiation position is the laser light irradiation position irradiated in the previous processing procedure. Since the laser beam 1 is at a different position from that of the laser absorbing material 14 which is generated by decomposition and removal, the laser beam 1 is irradiated to a position different from the laser absorbing material 14 after a certain period of time. Therefore, the laser light absorbing material diffuses with the passage of time, the heat storage amount in one conformal mask is suppressed, and a sufficient irradiation interval can be secured until the glass cloth inside the insulating material is cooled to the glass transition temperature or less.

Also, in the past, the same conformal mask was irradiated with the laser beam 1, so that it was affected by the heat storage due to the presence of the laser absorbing material 14 generated by the irradiation of the laser beam 1 irradiated earlier. In 1, since the following laser beam 1 is irradiated to a position different from the laser absorbing material 14 generated after decomposition and removal after a certain period of time, the laser beam absorbing material diffuses with the passage of time, Attenuation of the intensity of the laser beam 1 to be irradiated in the subsequent line and change in the intensity distribution are less likely to occur, and a good hole can be formed.

The irradiation position of the laser beam 1 is deflected by the light scanning device 4 controlled by the control device 50, or parallel movement of the workpiece 6 by driving the moving table 9, or deflection and moving table 9 by the light scanning device 4. It is positioned by both of the drive of. If it is within the scanning range of the light scanning device 4, the irradiation position of the laser light 1 may be changed only by the scanning of the light scanning device 4 in a state where the movable table 9 is stationary.

The laser light irradiation positions k (n, m) which are at the same relative position with respect to the center of gravity of each conformal mask, that is, m are divided into groups, and light is irradiated to the laser light irradiation position group where m is the same Positioning is performed by irradiating the laser light 1 only by deflection by the scanning device 4, and in the case of irradiation to the laser light irradiation position group at the relative position where m is different, the movement table 9 is driven by the difference of the coordinates between the groups. By moving the work material 6 in parallel, relative displacement may be given to the laser light irradiation position between the groups.

As an alternative to moving the workpiece 6 in parallel by driving the moving table 9, as shown in FIG. 5, an optical scanning device 20 is additionally disposed at a position closer to the oscillator 2 than the installation position of the fθ lens 5, A relative displacement may be given to the laser beam irradiation position by 20.

In the first embodiment, the case where one pulse irradiation is performed to each position of the laser light irradiation position k (n, m) has been described, but even if a plurality of pulse numbers are continuously irradiated and the hole formation is advanced good.

In this way, focusing on any conformal mask, the laser beam to be irradiated following is at a position different from the generation position of the laser light absorbing material that has been decomposed and removed in advance, and after a certain amount of time has elapsed Because it is irradiated, the laser light absorbing material diffuses with the passage of time, the heat storage amount to one conformal mask is suppressed, and a sufficient irradiation interval is secured until the glass cloth inside the insulating material cools to the glass transition temperature or less. As a result, the glass cloth is sufficiently decomposed and removed, and the projection of the glass cloth does not occur, and the retention of the glass ball at the bottom of the hole can be suppressed, so that the hole can be formed efficiently.

Example 2
In the first embodiment, the laser beam irradiation point is defined based on the center of gravity of the conformal mask as one outer peripheral part of the conformal mask and the outer peripheral part of the conformal mask is determined. A plurality of outer peripheral portions similar in shape to the outer peripheral portion of the formal mask may be defined. When the conformal mask is circular, the center of gravity of the conformal mask is the center of the conformal mask.

FIG. 6 shows the irradiation position of the laser light 1 on the base material 10 on which two conformal masks 60a to 60b, which are the workpieces 6 showing the second embodiment of the present invention, are formed. In the second embodiment of the present invention, the conformal mask 60a will be described by way of example. An inner peripheral portion of the conformal mask 60a is similar to the outer peripheral portion 61 of the conformal mask 60a based on the center of gravity of the conformal mask 60a. 21 and the outer peripheral portion 22 are determined, and the laser beam irradiation point 62 is determined so as to equally divide the outer peripheral length of the outer peripheral portion 21 and the outer peripheral portion 22. In each of the N conformal masks, there are P laser light irradiation points for the outer peripheral portion 21 and Q laser light irradiation points for the outer peripheral portion 22 in each conformal mask. In this case, of the n-th conformal mask, the p-th laser beam irradiation position for irradiating the outer peripheral portion 21 is a (n, p), and the q-th laser light irradiation position for irradiating the outer peripheral portion 22 is Let b (n, q). Here, 1 ≦ n ≦ N, 1 ≦ p ≦ P, and 1 ≦ q ≦ Q.

Regarding the processing order, the laser light irradiation position a (n, p) for irradiating the outer peripheral portion 21 and the laser light irradiation position b (n, q) for irradiating the outer peripheral portion 22 are described in the first embodiment without distinction. The order may be determined in the same order as the laser light irradiation order. For one conformal mask, four or more positions where the laser light 1 is irradiated are determined in advance, and when one conformal mask is irradiated with the laser light 1 every time one processing procedure is completed, The laser light 1 is irradiated to the position farthest from the irradiated position and at the non-irradiated position of the laser light 1. The processing conditions at the time of irradiating the laser light 1 to the laser light irradiation positions a (n, p) and b (n, q) are all the same.

Example 3
In the second embodiment, the processing conditions for irradiating the laser light 1 to the laser light irradiation positions a (n, p) and b (n, q) are all the same, but as shown in FIG. And at least one of parameters such as the pulse width of the laser beam 1 to be irradiated, beam intensity, the number of shots, and the distance between the surface of the substrate 10 and the focal plane 7 of the fθ lens You may change the parameters.

Taking the conformal mask 60a as an example, the laser beam 1 precedes the outermost peripheral portion 21 of the outer peripheral portion similar to the outer peripheral portion of the conformal mask 60a from the center of gravity of the conformal mask 60a. Then, consider the case where the inner peripheral portion 22 is irradiated with the laser light 1. In the center of gravity of the conformal mask 60a, most of the resin and the glass cloth are removed by the laser beam 1 applied to the outer peripheral portion 21 in advance, so the outer peripheral portion precedes the inner peripheral portion 22. When the laser light 21 is irradiated under the same processing conditions as the laser light 1, the heat input may be excessive, and a melted portion may occur in the bottom surface conduction layer. Therefore, the laser beam 1 irradiated to the inner peripheral portion 22 can be formed with a low beam intensity to avoid melting and form a good hole.

When the thickness of the insulating layer 17 inside the conformal mask is as thick as, for example, 200 μm or more, the laser beam 1 is applied to the inner peripheral portion 22 in order to effectively remove the lower portion on the back surface conductor layer 19 side of the insulating layer 17. In the case of irradiation, the focal plane 7 of the fθ lens 5 is lowered or the workpiece 6 is raised so that the laser light 1 is condensed more at the lower portion of the insulating layer 17 on the back surface conductor layer 19 side, In the lower part on the back surface conductor layer 19 side of the insulating layer 17, it is possible to perform hole formation in which the area for removing the insulator is enlarged.

Reference Signs List 1 laser light 2 laser oscillator 3 energy adjustment device 4 20 light scanning device 5 fθ lens 6 work material 7 focal plane 8 parallel moved plane 9 moving table 10 base 11 12, 21, 22, 61 outer peripheral portion, 13 laser light irradiation point, 14 laser absorbing material, 16 surface conductor layer, 17 insulating layer, 18 glass cloth, 19 back surface conductor layer, 30a to 30f, 50 control device, 60a, 60b Conformal mask.

Claims

A laser processing method for performing a plurality of conformal processings in which the number of holes to be formed is a laser, in a region defined inside or outside of a first mask constituting a plurality of conformal masks provided corresponding to the number of holes A first processing step for irradiating light, and a processing step different from the first processing step for irradiating the laser light to the inside or the outside of the mask different from the first mask constituting the conformal mask And
The processing procedure for carrying out the first processing step to the different processing step is repeated a plurality of times, and the processing is completed while changing the position to which the laser light is applied every time the processing procedure is repeated a plurality of times. Laser processing method.
The laser processing method according to claim 1, wherein four or more positions where the laser light is irradiated to one of the conformal masks are determined in advance.
When irradiating the laser beam to one of the conformal masks every time the processing procedure is repeated a plurality of times, the laser beam is irradiated at the position farthest from the position where the laser light has been irradiated and at the unirradiated position of the laser light The laser processing method according to claim 2, further comprising:
4. The laser processing method according to claim 3, wherein the area has a shape similar to that of the conformal mask based on the center of gravity of the conformal mask, and the outer peripheral portion of the shape has the same shape.
5. The laser processing method according to claim 4, wherein the laser beam irradiation position is a position obtained by equally dividing the outer peripheral length of the outer peripheral portion into a plurality of portions.
4. The laser processing method according to claim 3, wherein a plurality of the regions are defined inside or outside the conformal mask.
The laser processing method according to any one of claims 1 to 6, wherein the laser light is pulsed light.
8. The laser processing method according to claim 7, wherein the number of pulsed lights is one pulse.