JP2002178181A - Method, workpiece and mask for laser machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining method that facilitates control of a machining shape without greatly changing the specifications of a laser beam machine. SOLUTION: The relation of a laser beam LB absorption coefficient, which has two material layers 11a, 11b constituting a green sheet 11, is set as the first material layer 11a layer than the second material layer 11b. As a result, a diameter can be miniaturized for the part corresponding to the second material layer 11b of a through hole SH, also, energy transmission to the first material layer 11a is restricted by the second material layer 11b, thereby enabling miniaturization of a diameter and suppression of damage to be contrived for the part to which the first material layer 11a of the through hole SH corresponds. Consequently, the through hole SH having a minute diameter and a high aspect ratio can be formed on the green sheet 11 in a suitable depth and with a high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method for performing predetermined processing by irradiating a workpiece with a laser beam,
The present invention relates to a workpiece for laser processing and a mask for laser processing.

[0002]

2. Description of the Related Art As a method for performing micro-machining such as drilling and grooving on a workpiece, a Y-wave capable of emitting a fundamental wave or a harmonic wave is used.
A laser processing method using a laser oscillator such as an AG laser or a CO ₂ laser is generally used. Processing of the workpiece is performed by irradiating the laser beam emitted from the laser device to the workpiece via an appropriate optical system, and the irradiation shape of the laser beam on the workpiece is included in the optical system. It is defined by the objective lens and mask to be used.

[0003]

FIG. 1 shows a through hole for interconnecting a coil conductor layer in a ceramic green sheet (hereinafter simply referred to as a green sheet) used in manufacturing a multilayer chip inductor. The method of forming by laser processing will be described. In the figure, reference numeral 1 denotes a green sheet, 2 denotes a carrier film for supporting the green sheet 1, and LB denotes a laser beam.

Green sheet 1 on carrier film 2
When the laser light LB is irradiated toward the green sheet 1, the green sheet 1 is heated and disappears by the energy of the laser light LB, and a through hole SH is formed. Through hole S
The shape of H is generally an inverted truncated cone due to energy attenuation, but the aspect ratio of the through hole SH varies depending on the extinction coefficient (absorption rate) of the laser beam LB of the green sheet 1.

In order to use the irradiation energy of the laser beam LB with high efficiency, a green sheet 1 having a large absorption coefficient may be used.
When using is used, the diameter of the through hole SH becomes large, the aspect ratio is greatly reduced, and the inner surface of the through hole SH is easily damaged. Therefore, it is difficult to form the through hole SH having a small diameter at a narrow pitch. There is. Conversely, in order to form the through hole SH having a high aspect ratio, a green sheet 1 having a small extinction coefficient may be used, but the intended through hole SH cannot be formed unless the irradiation energy of the laser beam LB is increased. Therefore, there is a problem that a laser processing machine having a high output specification is required and running cost is increased.

The above-mentioned inconsistency is caused not only when a green sheet is subjected to other processing such as grooving, but also when a hole is formed in a workpiece other than the green sheet using a laser beam.
This can also occur when performing processing such as grooving.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose of laser processing capable of easily controlling a processing shape without greatly changing the specifications of a laser processing machine. An object of the present invention is to provide a method, a workpiece for laser processing, and a mask for laser processing.

[0008]

In order to achieve the above object, a first laser processing method according to the present invention is characterized in that a plurality of material layers having different laser light absorption coefficients are laminated in the order of the absorption coefficient. The present invention is characterized in that a prepared processed portion is prepared, and a predetermined process is performed on the processed portion by irradiating a laser beam toward a material layer having the smallest absorption coefficient of the processed portion.

According to the first laser processing method, when a laser beam is applied to a portion to be processed, energy is transferred to the material layer having a large absorption coefficient by the material layer having a small absorption coefficient constituting the portion to be processed. Thus, the shape of the processing performed on the processing target portion can be controlled.

In a second laser processing method according to the present invention, a mask formed by laminating a plurality of material layers having different absorption coefficients of laser light in the order of the absorption coefficient is prepared. The material layer with the largest extinction coefficient is placed so as to face the workpiece, and the mask is pierced by irradiating laser light toward the material layer with the smallest extinction coefficient at the same time as the laser light is applied through this perforation. It is characterized in that predetermined processing is performed on the workpiece by irradiating the workpiece.

According to the second laser processing method, when a mask is irradiated with a laser beam, energy transmission to the material layer near the workpiece is restricted by the material layer having a small absorption coefficient constituting the mask. And the energy transfer to the workpiece can be limited by the mask,
Thus, it is possible to control the shape of the processing performed on the workpiece.

On the other hand, the workpiece for laser processing according to the present invention comprises at least a workpiece to be formed by laminating a plurality of material layers having different absorption coefficients of laser light in order of the absorption coefficient. Is its feature. According to the workpiece for laser processing, the first laser processing method can be accurately performed.

On the other hand, the mask for laser processing according to the present invention is characterized in that a plurality of material layers having different absorption coefficients of laser light are laminated in the order of the absorption coefficient. According to the laser processing mask, the second laser processing method can be accurately performed.

The above and other objects, structural features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIGS. 2 (A) to 2 (C) show a laser processing for forming a through hole in a ceramic green sheet used in manufacturing a multilayer chip inductor. 1 shows a first embodiment to which the invention is applied. In the figure, reference numeral 11 denotes a ceramic green sheet (hereinafter simply referred to as a green sheet) used for manufacturing a multilayer chip inductor, 12 denotes a carrier film made of PET or the like for supporting the green sheet 11, and LB denotes Y.
The laser light emitted from a laser oscillator such as an AG laser or a CO ₂ laser to the green sheet 11 via an optical system.

The green sheet 11 includes a first material layer 11a and a second material layer 11b as shown in FIG.
This green sheet 11 forms a first material layer 11a by applying a slurry for the first material layer to a predetermined thickness on the carrier film 12 by a method such as a doctor blade method, and forms the first material layer 11a by the same method. To form a second material layer 11b by applying a slurry for the second material layer to a predetermined thickness, or a method in which the separately formed material layers 11a and 11b are overlaid on the carrier film 12. I have.

The extinction coefficient (absorption rate) of the laser beam LB of the two material layers 11a and 11b constituting the green sheet 11 is such that the first material layer 11a> the second material layer 11
b is set. Also, the thickness d1 of the first material layer 11a is preferably set to d1 ≧ 1 / (extinction coefficient × 10), and similarly, the second material layer 11b
Is preferably d2 ≧ 1 / (extinction coefficient × 10).
Is set to The two material layers 11a and 11b
Can be arbitrarily changed and set by adding a extinction coefficient adjusting material such as a dye or carbon powder to each slurry, in addition to changing the components of the slurry for forming each and the mixing ratio thereof. .

When the through holes SH for interconnecting the coil conductor layers CL are formed in the green sheet 11, a laser beam LB is applied to the second material layer 11b of the green sheet 11 as shown in FIG. Irradiation is repeated for the required number of through holes. As a result, the second material layer 11b and the first material layer 11a are heated by the energy of the laser beam LB and disappear to form a through hole SH.

As described above, the extinction coefficient of the laser beam LB of the two material layers 11a and 11b is lower than that of the second material layer 1a.
Since 1b <the first material layer 11a is set,
The diameter of the portion of the through hole SH corresponding to the second material layer 11b does not increase so much. Also, the first material layer 11a
Is larger than the extinction coefficient of the second material layer 11b, but since the energy transfer to the first material layer 11a is limited by the second material layer 11b, the first material layer 11a of the through hole SH corresponds. The diameter of the portion is the first material layer 11
As in the case of directly irradiating the laser beam LB to a, the damage that may occur on the inner surface of the same portion is suppressed.

That is, the through hole SH formed in the green sheet 11 by the irradiation of the laser beam LB has a shape close to an inverted truncated cone due to energy attenuation, but has a high aspect ratio close to a vertically long cylindrical shape. In addition, high quality with little damage to the inner surface is obtained. Note that the above-mentioned operation is performed by setting the thickness d1 of the first material layer 11a and the thickness d2 of the second material layer 11b constituting the green sheet 11 to d1 ≧ 1 / (extinction coefficient × 10) and d2 ≧
By setting 1 / (extinction coefficient × 10),
It can be obtained more accurately.

On the green sheet 11 after the through holes SH are formed, as shown in FIG. 2C, a conductor layer CL for a coil having a predetermined shape is formed by a technique such as screen printing using a conductor paste as a material. You. Since the coil conductor layer CL is formed so that a part thereof overlaps the through hole SH, the through hole SH is filled with the conductor paste simultaneously with the paste printing.

The green sheet 11 after the formation of the coil conductor layer CL is peeled off from the carrier film 12 and sequentially laminated in such a manner as to be sandwiched between the through holes and the green sheet on which the coil conductor layer is not formed. And crimped. The green sheet 1
The conductor layer CL for the coil existing between the through holes SH is a through hole SH.
They are connected to each other through a conductor portion filled therein to form a coil. Incidentally, the laminated body after lamination / compression bonding is cut into parts dimensions and then fired, and external electrodes are formed on the surface of the fired chip.

According to the laser processing method described above, the two material layers 11a and 11b constituting the green sheet 11 are formed.
The relationship between the absorption coefficient of the laser beam LB of the first material layer 1
By setting 1a> second material layer 11b, the diameter of the portion of through hole SH corresponding to second material layer 11b can be miniaturized, and energy transfer to first material layer 11a can be performed by the second material layer 11b. By limiting with the material layer 11b, the diameter of the portion of the through hole SH corresponding to the first material layer 11a can be miniaturized and the damage can be suppressed, whereby the green sheet 11 has a small diameter of 50 μm or less, and Through holes SH having a high aspect ratio can be formed at an appropriate depth and with high quality.

That is, a green sheet 11 is prepared by laminating two material layers 11a and 11b having different absorption coefficients of the laser beam LB in the order of the absorption coefficient, and a second material layer having the smallest absorption coefficient is prepared. By irradiating the laser beam LB toward 11b, the shape including the diameter and the depth of the through hole SH formed in the green sheet 11 can be easily controlled without largely changing the specifications of the laser processing machine. be able to. In other words, the two material layers 11a and 11b having different absorption coefficients of the laser beam LB.
By merely preparing a green sheet 11 formed by laminating in the order of the magnitude of the light absorption coefficient, the same effect can be obtained by appropriately executing the laser processing method.

In the above description, the green sheet has a two-layer structure, but the same effect can be obtained by forming a green sheet by stacking three or more material layers in the order of the absorption coefficient. Can be obtained.

In the above description, a method of forming a through hole in a green sheet used in manufacturing a multilayer chip inductor has been exemplified. When processing, of course, green sheets used when manufacturing other types of multilayer electronic components such as multilayer LC filters and multilayer inductor arrays, and workpieces other than green sheets having a similar layer structure, That is, all of the workpieces are subjected to processing such as drilling and grooving on a workpiece configured by stacking a plurality of material layers having different laser light absorption coefficients in the order of the absorption coefficient. The same operation and effect can be obtained.

[Second Embodiment] FIGS. 3A to 3C
Shows a second embodiment in which the present invention is applied to laser processing for forming via holes for conductor columns on a circuit board having a multilayer structure. Reference numeral 21 in the figure denotes a circuit board having a multilayer structure, L
B is a laser beam applied to the circuit board 21 from a laser oscillator such as a YAG laser or a CO ₂ laser via an optical system.

As shown in FIG. 3A, the circuit board 21 includes a first material layer 21a, a second material layer 21b, and a third material layer 21c.
And a fourth material layer 21d, and the first material layer 21a
A conductor layer IP made of a metal such as copper is provided thereon. The circuit board 21 is formed by coating a resin material for a first material layer on a base at a predetermined thickness to form a first material layer 21a.
The first material layer 21a is coated with a resin material for a second material layer at a predetermined thickness to form a second material layer 21b.
Is formed on the second material layer 21b, and a resin material for a third material layer is coated on the second material layer 21b at a predetermined thickness to form a third material layer 21c.
Is formed, and a resin material for a fourth material layer is coated on the third material layer 21c at a predetermined thickness to form a fourth material layer 21d.
Or a method of forming each material layer 21 separately.
It is created by a method of superimposing and joining a to 21d.

Further, among the four material layers 21a to 21d constituting the circuit board 21, the extinction coefficient (absorption rate) of the laser beam LB of the three material layers 21b to 21d excluding the first material layer 21a is as follows. 2 material layer 21b> third material layer 21c
> And the fourth material layer 21d. The thickness d1 of the second material layer 21b is preferably d.
1 ≧ 1 / (extinction coefficient × 10), and similarly, the thickness d2 of the third material layer 21c is preferably d2 ≧ 1.
/ (Extinction coefficient × 10), and the thickness d3 of the fourth material layer 21d is preferably set to d3 ≧ 1 / (extinction coefficient × 10). The extinction coefficients of the three material layers 21b to 21d change the types of resin materials for forming the respective layers and the mixing ratio thereof, and add an extinction coefficient adjusting material such as a dye or carbon powder to each resin material. Can be changed and set arbitrarily. To give a specific example, the second
The material layer 21b is made of an epoxy resin containing a dye,
The third material layer 21c is made of a polyimide resin or an epoxy resin, and the fourth material layer 21d is made of a fluorine resin, a mixed resin of a fluorine resin and a polyimide resin, or an epoxy resin containing a SiO ₂ filler. Incidentally, the first material layer 21a is made of an epoxy resin.

When the via hole VH reaching the conductor layer IP on the first material layer 21a is formed in the circuit board 21, the laser beam LB is applied to the fourth material layer of the circuit board 21 as shown in FIG. Irradiation is repeated toward the 21d by the required number of via holes. Thereby, the fourth material layer 21d, the third material layer 21c, and the second material layer 21b are heated and lost by the energy of the laser beam LB, and the via holes VH are formed.

As described above, the three material layers 21b to 21b-2
The extinction coefficient of the laser beam LB of 1d is equal to the fourth material layer 21.
Since d <third material layer 21c <second material layer 21b, the fourth material layer 21d of via hole VH is set.
However, the diameter of the corresponding part does not become so large. Also,
Although the extinction coefficient of the third material layer 21c is larger than the extinction coefficient of the fourth material layer 21d, the energy transfer to the third material layer 21c is restricted by the fourth material layer 21d. The diameter of the portion corresponding to the layer 21c does not increase as in the case of directly irradiating the laser beam LB to the third material layer 21c, and damage that may occur on the inner surface of the portion is suppressed. Further, the extinction coefficient of the second material layer 21b is larger than the extinction coefficient of the third material layer 21c.
Since the energy transfer to the material layer 21b is restricted by the third material layer 21c, the diameter of the portion of the via hole VH to which the second material layer 21b corresponds corresponds to the case where the laser beam LB is directly applied to the second material layer 21b. Not so big,
Damage that can occur on the inner surface of the portion is also suppressed.

That is, the via hole VH formed in the circuit board 21 by the irradiation of the laser beam LB has a shape close to an inverted truncated cone because of energy attenuation.
It has a high aspect ratio close to a vertically long columnar shape, and has high quality with little damage to the inner surface. still,
The above operation is achieved by setting the thickness d1 of the second material layer 21b, the thickness d2 of the third material layer 21c, and the thickness d3 of the fourth material layer 21d, which constitute a part of the circuit board 21, to d1 ≧ 1 / (extinction coefficient × 10), d2 ≧ 1 / (extinction coefficient × 10), d3 ≧
By setting 1 / (extinction coefficient × 10),
It can be obtained more accurately.

After the via holes VH are formed, the conductor columns CC made of a metal such as copper are formed in the via holes VH by plating as shown in FIG. 2C.

Electronic components are mounted on the circuit board 21 after the formation of the conductor columns CC so as to be connected to the exposed ends of the conductor columns CC. The external terminals of the mounted component are electrically connected to the conductor layer IP in the circuit board 21 via the conductor columns CC.

According to the laser processing method described above, of the four material layers 21a to 21d constituting the circuit board 21,
The relationship between the extinction coefficients of the laser beams LB of the three material layers 21b to 21d excluding the first material layer 21a is described in the second material layer 21.
By setting b> third material layer 21c> and fourth material layer 21d, the diameter of the portion of via hole VH corresponding to fourth material layer 21d can be reduced, and
Energy is transferred to the third material layer 21c by the fourth material layer 21c.
d, and the energy transfer to the second material layer 21b is limited by the third material layer 21c, so that the diameter of the via hole VH is small at the portion corresponding to the third material layer 21c and the second material layer 21b. And the damage can be suppressed.
Via holes VH having the following minute diameter and a high aspect ratio can be formed at an appropriate depth reaching the conductor layer IP and with high quality.

That is, three material layers 21b having different absorption coefficients of the laser beam LB are formed on the first material layer 21a serving as a base.
The circuit board 21 is prepared by laminating layers 21 to 21d in order of the absorption coefficient, and irradiating the laser beam LB toward the fourth material layer 11b having the smallest absorption coefficient to obtain the specifications of the laser processing machine. Without drastically changing
The shape including the diameter and depth of the via hole VH formed in the circuit board 21 can be easily controlled. In other words, a circuit board 2 configured by laminating three material layers 21b to 21d having different absorption coefficients of the laser beam LB on the first material layer 21a serving as a base in the order of the absorption coefficient.
The same effect can be obtained by simply preparing the laser processing method 1 in advance and performing the laser processing method appropriately.

In the above description, the circuit board has a four-layer structure and three of the material layers are laminated in the order of the light absorption coefficient. The via holes may be formed in the two material layers by laminating in order of the magnitude of the light absorption coefficient. Of course, the four material layers constituting the circuit board may be laminated in the order of the absorption coefficient to form a via hole penetrating the four material layers. In addition, 4
Although the one having a layer structure is shown, the above-described laser processing method can be applied to a circuit board having a layer structure of five or more or three or less. Furthermore, although each of the material layers forming the circuit board is formed of resin, the same operation and effect as described above can be obtained even if each of the material layers is ceramics after firing.

In the above description, a method for forming via holes for conductor columns in a circuit board having a multilayer structure has been exemplified. However, the above-described laser processing method performs other processing such as grooving on the circuit board. Needless to say, the workpiece other than the circuit board having the same layer structure, that is, a part or all of the workpiece is formed by a plurality of material layers having different absorption coefficients of laser light having different absorption coefficients. The present invention can also be applied to the case of performing processing such as drilling and grooving on a workpiece formed by laminating in order, and the same operation and effect can be obtained.

[Third Embodiment] FIGS. 4A to 4C
Shows a third embodiment in which the present invention is applied to laser processing for forming a via hole for a conductor column in a resin layer of a circuit board. In the figure, reference numeral 31 denotes a circuit board, 32 denotes a resin layer formed on the circuit board 31, 33 denotes a mask, and LB denotes YA.
This is laser light emitted from a laser oscillator such as a G laser or a CO ₂ laser to the mask 33 via an optical system.

The circuit board 31 is made of a resin, ceramics, or the like, and a conductor layer CP made of a metal such as copper is provided on the surface thereof. The resin layer 32 is made of a resin having excellent heat resistance, such as a polyimide resin or a polyamideimide resin, and has a conductor layer C
A predetermined thickness is formed on the surface of the circuit board 31 so as to cover P.

As shown in FIG. 4A, the mask 33 includes a first material layer 33a, a second material layer 33b, and a third material layer 33c made of resin. This mask 33 has a first
The resin material for the material layer is coated with a predetermined thickness to make the first
A material layer 33a is formed, and a second layer is formed on the first material layer 33a.
The second layer is formed by coating the resin material for the material layer with a predetermined thickness.
A material layer 33b is formed, and a third layer is formed on the second material layer 33b.
The third step is to coat the resin material for the material layer with a predetermined thickness.
It is formed by a method of forming the material layer 33c or a method of overlapping and joining the separately formed material layers 33a to 33c.

The extinction coefficient (absorbance) of the laser beam LB of the three material layers 33a to 33c constituting the mask 33 is as follows: the first material layer 33a> the second material layer 33b> the third material layer 33b.
It is set so as to have the relationship of the material layer 33c. The thickness d1 of the first material layer 33a is preferably d1 ≧ 1.
/ (Extinction coefficient × 10), and likewise, the second
The thickness d2 of the material layer 33b is preferably set to d2 ≧ 1 / (extinction coefficient × 10), and the thickness d3 of the third material layer 33c is set.
Is preferably set to d3 ≧ 1 / (extinction coefficient × 10). The extinction coefficients of the three material layers 33a to 33a change the type of resin material for forming each of them and the mixing ratio thereof, and add an extinction coefficient adjusting material such as a dye or carbon powder to each resin material. Can be changed and set arbitrarily. As a specific example, the first material layer 3
3a is made of an epoxy resin containing a fluorescent dye,
The material layer 33b is made of a polyimide resin or an epoxy resin, and the third material layer 33c is made of a fluorine resin, a mixed resin of a fluorine resin and a polyimide resin, or an epoxy resin containing a SiO ₂ filler.

When a via hole VH reaching the conductor layer CP is formed in the resin layer 32 of the circuit board 31, as shown in FIG. 4B, first, a mask 33 is formed by using a first material layer 33a as a resin layer. 32 so as to be in contact with the upper surface,
Then, the laser beam LB is repeatedly irradiated from above each conductor layer CP toward the third material layer 33c of the mask 33 by the required number of via holes.

Thus, the third material layer 33 of the mask 33
c, the second material layer 33b, and the first material layer 33a are heated by the energy of the laser beam LB and disappear to form a through hole SH. At the same time, the resin layer 32 is irradiated with the laser beam LB through the through hole SH. The resin layer 32 is heated by the energy of the laser beam LB and disappears to form a via hole VH. Although not shown, a ring-shaped groove is formed around the via hole VH as necessary to prevent a crack or the like from occurring at the connection portion due to a difference in thermal expansion between the resin layer 32 and the mounted component. Is done.

The mask 3 constituting the mask 33 as described above
The absorption coefficient of the laser beam LB of the three material layers 33a to 33c is set to satisfy the relationship of the third material layer 33c <the second material layer 33b <the first material layer 33a.
The diameter of the portion corresponding to the third material layer 33c of H does not become so large. Further, the extinction coefficient of the second material layer 33b of the mask 33 is larger than the extinction coefficient of the third material layer 33c, but the energy transmission to the second material layer 33b is limited by the third material layer 33c. The diameter of the portion corresponding to the SH second material layer 33 b is the second material layer 33.
b does not increase as in the case of directly irradiating the laser beam LB. Further, although the extinction coefficient of the first material layer 33a of the mask 33 is larger than the extinction coefficient of the second material layer 33b,
Energy transfer to the first material layer 33a is
Therefore, the diameter of the portion of the through hole SH corresponding to the first material layer 33a does not increase as in the case where the first material layer 33a is directly irradiated with the laser beam LB.

On the other hand, since the energy transfer to the resin layer 32 of the circuit board 31 is restricted by the upper mask 33, the diameter of the via hole VH is large as in the case where the resin layer 32 is directly irradiated with the laser beam LB. In addition, damage that may occur on the inner surface of via hole VH is also suppressed.

That is, the via hole VH formed in the resin layer 32 of the circuit board 31 through the mask 33 by the irradiation of the laser beam LB has a shape close to an inverted truncated cone because of energy attenuation, but has a vertically long cylindrical shape. It has a high aspect ratio close to that of, and has high quality with less inner surface damage. The above-mentioned operation is performed by setting the thickness d1 of the first material layer 33a, the thickness d2 of the second material layer 33b, and the thickness d3 of the third material layer 33c constituting the mask 33 to d1 ≧ 1 / (extinction coefficient × 10). , D2 ≧ 1 / (extinction coefficient × 10) and d3 ≧ 1 / (extinction coefficient × 10), it is possible to obtain more accurately.

After the formation of the via holes VH, the mask 33 is removed from the resin layer 32 of the circuit board 31, and as shown in FIG. 4C, a metal such as copper is formed in the via holes VH by plating. A conductor column CC is formed.

On the resin layer 32 of the circuit board 31 after the formation of the conductor column CC, an IC chip or the like is connected to the exposed end of the conductor column CC as shown by a virtual line in FIG. The electronic component 34 is mounted via a ball CB made of a bonding material such as solder. The external terminals of the electronic component 34 are electrically connected to the conductor layer CP of the circuit board 31 via the balls CB and the conductor columns CC.

According to the above-described laser processing method, the relationship between the absorption coefficient of the laser beam LB of the three material layers 33a to 33c constituting the mask 33 is determined by the first material layer 33a> the second material layer 33a.
By setting the material layer 33b> and the third material layer 33c, the diameter of the portion of the through hole SH corresponding to the third material layer 33c can be reduced, and the energy can be transmitted to the second material layer 33b. Is limited by the third material layer 33c, and the energy transfer to the first material layer 33a is limited by the second material layer 33b, so that the second material layer 33b and the first material layer 33a of the through hole SH correspond to each other. It is possible to reduce the diameter of the portion and suppress damage.

Further, by limiting the energy transfer to the resin layer 32 of the circuit board 31 by the upper mask 33, the resin layer 32 of the circuit board 31 has a small diameter of 30 μm or less and a high aspect ratio. The via hole VH is formed at an appropriate depth to reach each conductor layer CP, and
It can be formed with high quality. In addition, the mask 33 prevents the cross-sectional shape of the via hole VH from becoming elliptical due to the aberration of the objective lens of the laser beam machine. It can be formed on the resin layer 32 of the circuit board 31.

That is, a mask 33 is prepared by laminating three material layers 33a to 33c having different absorption coefficients of the laser beam LB in the order of the absorption coefficient.
3 is disposed such that the first material layer 33a having the largest extinction coefficient faces the resin layer 32 of the circuit board 31, and the laser beam LB is irradiated toward the third material layer 33c of the mask 33 having the smallest extinction coefficient. By doing so, the circuit board 31 can be used without significantly changing the specifications of the laser processing machine.
The shape including the diameter and depth of the via hole VH formed in the resin layer 32 can be easily controlled. In other words, the laser processing method can be properly performed only by preparing a mask 33 formed by laminating three material layers 33a to 33c having different absorption coefficients of the laser beam LB in the order of the absorption coefficient. And the same effect can be obtained.

In the above description, a mask having a three-layer structure is shown as a mask. However, the same effect can be obtained by forming a mask by laminating four or more or two or less material layers in the order of the absorption coefficient. The effect can be obtained. Further, although each of the material layers constituting the mask is formed of resin, the same operation and effect can be obtained even if each of the material layers is ceramics after firing. Further, in order to facilitate handling of the mask, a protective film made of PET or the like may be attached to both surfaces of the mask, and this film may be peeled off when the mask is used.

In the above description, a method of forming a via hole for a conductor column in a resin layer on a circuit board has been exemplified. However, the above-described laser processing method has a single-layer or multi-layer structure made of resin, ceramics, or the like. Not only when forming a via hole of a predetermined depth in a circuit board, forming a via hole penetrating the board, or performing other processing such as grooving or marking on the board. The present invention can also be applied to a case where a process is performed such as drilling, grooving, marking, or the like, for example, a case where a hole is drilled in an inkjet nozzle or the like, and the same operation and effect can be obtained.

Fourth Embodiment FIGS. 5A to 5C
Shows a fourth embodiment in which the present invention is applied to laser processing for forming via holes for conductor columns having different depths on a circuit board having a multilayer structure. In the figure, reference numeral 41 denotes a circuit board having a multilayer structure, 42 denotes a mask, and LB denotes a YAG laser or CO.
₂ is a laser beam emitted from a laser oscillator such as a laser to the mask 42 via an optical system.

The circuit board 41 is made of resin, ceramics, or the like, and has a first layer 41a and a first layer 41 as shown in FIG.
and a third layer 41c provided on the second layer 41b. Also, the circuit board 4
A first conductor layer IP1 made of a metal such as copper is provided on one first layer 41a, and a second conductor layer IP2 made of a metal such as copper is provided on the second layer 41b.

As shown in FIG. 5A, the mask 42 has a first material layer 42a, a second material layer 42b, and a third material layer 42c made of resin. As can be seen from the drawing, the first material layer 42a of the mask 42 is provided corresponding to only the second conductor layer IP2 of the circuit board 41, and the first conductor layer Ia of the mask 42 is provided.
The portion corresponding to P1 is the second material layer 42b and the third material layer 4
2c. The mask 42 is formed by coating a resin material for a first material layer on a base to a predetermined thickness to form a first material layer 42a.
a is coated with a resin material for a second material layer to a predetermined thickness to form a second material layer 42b.
b, a resin material for a third material layer is coated with a predetermined thickness to form a third material layer 42c, or each of the separately formed material layers 42a to 42c is formed by overlapping and joining. ing.

The extinction coefficient (absorption rate) of the laser beam LB of the three material layers 42a to 42c constituting the mask 42 is as follows: the first material layer 42a> the second material layer 42b> the third material layer 42b.
It is set so as to have the relationship of the material layer 42c. The thickness d1 of the first material layer 42a is preferably d1 ≧ 1.
/ (Extinction coefficient × 10), and likewise, the second
The thickness d2 of each of the thin portion and the thick portion of the material layer 42b
Is preferably set to d2 ≧ 1 / (extinction coefficient × 10), and the thickness d3 of the third material layer 42c is preferably set to d3 ≧ 1.
/ (Extinction coefficient × 10). The extinction coefficients of the three material layers 42a to 42a change the types of resin materials for forming each of them and the mixing ratio thereof, and add an extinction coefficient adjusting material such as a dye or carbon powder to each resin material. Can be changed and set arbitrarily.
As a specific example, the first material layer 42a is made of an epoxy resin containing a fluorescent dye, the second material layer 42b is made of a polyimide resin or an epoxy resin, and the third material layer 42a is made of a polyimide resin or an epoxy resin.
c is made of a fluorine resin, a mixed resin of a fluorine resin and a polyimide resin, or an epoxy resin containing a SiO ₂ filler.

When the via hole VH1 reaching the first conductor layer CP1 and the via hole VH2 reaching the second conductor layer CP2 are formed in the circuit board 41, first, as shown in FIG. The layer 42a is the second conductor layer IP
2 and the mask 42 is arranged so as to be in contact with the upper surface of the circuit board 41 so that the second material layer 42b is located above the first conductor layer IP1. Mask 42 from above layers IP1 and IP2
The third material layer 42c is repeatedly irradiated for the required number of via holes.

Thus, the third material layer 42c and the second material layer 4 of the mask 42 are formed above the first conductor layer IP1.
2b is heated by the energy of the laser beam LB and disappears to form the first through hole SH1,
The second layer 41b and the third layer 41c of the circuit board 41 are irradiated with the laser beam LB through the first through hole SH1, and the energy of the laser beam LB causes the second layer 4b to be irradiated.
1b and the third layer 41c are heated and disappear, and the first via hole VH1 is formed.

On the upper side of the second conductor layer IP2, the third material layer 42c and the second material layer 42b of the mask 42 are formed.
And the first material layer 42a is heated by the energy of the laser beam LB and disappears to form the second through hole SH2. At the same time, the laser beam LB is applied to the third layer 41c of the circuit board 41 through the second through hole SH2. The third layer 4 is irradiated with the energy of the laser beam LB.
1c is heated and disappears to form a second via hole VH2.

As described above, 3 constituting the mask 42
Since the absorption coefficient of the laser beam LB of the three material layers 42a to 42c is set to satisfy the relationship of the third material layer 42c <the second material layer 42b <the first material layer 42a, the third material of the first through hole SH1 is set. The diameter of the portion corresponding to the layer 42c does not increase so much. Also, the second material layer 4 of the mask 42
Although the extinction coefficient of the second material layer 42b is larger than the extinction coefficient of the third material layer 42c, the energy transmission to the second material layer 42b is restricted by the third material layer 42c, and therefore, the second material layer 42b of the first through hole SH1 is limited. The diameter of the corresponding part is the second
It does not increase as in the case where the material layer 42b is directly irradiated with the laser beam LB.

In addition, the diameter of the portion of the second through hole SH2 corresponding to the third material layer 42c does not become so large from the above relationship of the light absorption coefficient. Although the extinction coefficient of the second material layer 42b of the mask 42 is larger than the extinction coefficient of the third material layer 42c, the energy transfer to the second material layer 42b is restricted by the third material layer 42c, and thus the first The diameter of the portion of the through hole SH1 corresponding to the second material layer 42b does not increase as in the case where the second material layer 42b is directly irradiated with the laser beam LB. Further, the first of the mask 42
Although the extinction coefficient of the material layer 42a is larger than the extinction coefficient of the second material layer 42b, since the energy transfer to the first material layer 42a is restricted by the second material layer 42b, the first material of the second through hole SH2 is The diameter of the portion corresponding to the layer 42a does not increase as in the case where the first material layer 42a is directly irradiated with the laser beam LB.

On the other hand, since the energy transfer to the circuit board 41 is restricted by the mask 42 on the upper side thereof, the diameter of the first via hole VH1 on the first conductor layer IP1 is directly transmitted to the second layer 41b and the third layer 41c. Unlike the case of irradiating the laser beam LB, the first via hole VH1 does not become large.
Damage that can occur on the inner surface of the substrate is also suppressed. In addition, the diameter of the second via hole VH2 on the second conductor layer IP2 does not become large as in the case where the laser light LB is directly applied to the third layer 41c, and the damage that may occur on the inner surface of the second via hole VH2 is suppressed. Is done.

That is, the first via hole VH1 and the second via hole VH2 formed on the circuit board 41 through the mask 42 by the irradiation of the laser beam LB have a shape close to an inverted truncated cone because of energy attenuation. This results in a high aspect ratio close to that of a vertically long columnar shape, and a high quality with little damage to the inner surface. The above operation is performed by setting the thickness d1 of the first material layer 42a constituting the mask 42, the thickness d2 of the thin and thick portions of the second material layer 42b, and the thickness d3 of the third material layer 42c to d1 ≧ 1. By setting / (extinction coefficient × 10), d2 ≧ 1 / (extinction coefficient × 10), and d3 ≧ 1 / (extinction coefficient × 10), it is possible to obtain more accurately.

After the formation of the two via holes VH1 and VH2, the mask 42 is removed from the circuit board 41, and as shown in FIG. 5C, a metal such as copper is placed in the first via hole VH1 by plating. Is formed, and a second conductor column CC2 made of a metal such as copper is formed in the second via hole VH2.

On the circuit board 41 after the two conductor columns CC1 and CC2 are formed, single or plural electronic components are mounted so as to be connected to the exposed ends of the conductor columns CC1 and CC2. The external terminals of the mounted components are electrically connected to the first conductor layer IP1 in the circuit board 41 via the first conductor column CC1, and are electrically connected to the first conductor layer IP2 in the circuit board 41 via the second conductor column CC2.

According to the above-described laser processing method, the relationship between the absorption coefficient of the laser beam LB of the three material layers 42a to 42c constituting the mask 42 is determined by comparing the first material layer 42a> the second material layer 42a.
By setting the material layer 42b> and the third material layer 42c, the diameter of the portion of the first through hole SH1 corresponding to the third material layer 42c can be reduced, and the thickness of the second material layer 42b can be reduced. Energy transfer to third material layer 42c
By the first through hole SH1
The diameter of the portion corresponding to the second material layer 33b can be reduced and the damage can be suppressed. On the other hand, the diameter of the portion of the second through hole SH2 corresponding to the third material layer 42c can be reduced, and the energy transfer to the second material layer 42b is restricted by the third material layer 42c. By limiting the energy transfer to the first material layer 42a by the second material layer 42b, the diameter of the portion of the second through hole SH2 corresponding to the second material layer 42b and the first material layer 42a can be reduced in size and the damage can be suppressed. Can be planned.

By limiting the energy transfer to the upper portion of the first conductor layer IP1 of the circuit board 41 by the mask 42 on the upper side thereof, the minute portion of 30 μm or less is formed on the upper portion of the first conductor layer IP1 of the circuit board 41. The first via hole VH1 having a large diameter and a high aspect ratio can be formed at an appropriate depth reaching the first conductor layer IP1 and with high quality, and the second conductor layer IP2 of the circuit board 41 can be formed. The second via hole VH2 having a small diameter of 30 μm or less and having a high aspect ratio can be formed at an appropriate depth reaching the second conductor layer IP2 and in high quality on the upper portion of the substrate. In addition, the first via hole VH1 and the second via hole VH1 are affected by the aberration of the objective lens of the laser beam machine.
The mask 42 prevents the cross section of the via hole VH2 from becoming elliptical, and the via holes VH1 and VH2 having a cross section of a true circle or a shape close to this can be formed on the circuit board 41.

That is, a mask 42 is prepared by laminating three material layers 42a to 42c having different absorption coefficients of the laser beam LB in the order of the absorption coefficient.
2 is the second material layer 42b having the largest extinction coefficient or the first material layer 42b.
The material layer 42a is disposed so as to face the circuit board 41,
Then, by irradiating the laser light LB toward the third material layer 42c having the smallest light absorption coefficient of the mask 42, without greatly changing the specifications of the laser processing machine,
Via holes VH1 and VH formed in circuit board 41
Control of the shape including the diameter and depth of No. 2 can be easily performed. In other words, the laser processing method described above can be properly performed only by preparing a mask 42 formed by laminating three material layers 42a to 42c having different absorption coefficients of the laser beam LB in the order of the absorption coefficient. And the same effect can be obtained.

In the above description, a mask having a three-layer structure (partially a two-layer structure) is shown as a mask, but four or more or two or less material layers are laminated in the order of the absorption coefficient. A similar effect can be obtained even if a mask is formed. Further, although each of the material layers constituting the mask is formed of resin, the same operation and effect can be obtained even if each of the material layers is ceramics after firing. Furthermore, in order to facilitate handling of the mask, a protective film made of PET or the like is attached to both sides of the mask,
This film may be peeled off when using a mask.

Further, in the above description, a method of forming two via holes for conductor columns having different depths on a circuit board having a multilayer structure has been described as an example. The above via holes can be formed in the circuit board. In addition, the aforementioned laser processing method,
When forming an appropriate number of via holes of a predetermined depth in a single-layer circuit board, or performing other processing such as grooving or marking on the board, as well as drilling holes in workpieces other than the circuit board, The present invention can be widely applied to the case of performing processing such as grooving and marking, and the same operation and effect can be obtained.

[0073]

As described in detail above, according to the present invention,
In the case of performing various types of processing using laser light, it is possible to easily control the processing shape.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional method of forming a through hole in a green sheet by laser processing.

FIG. 2 is a diagram showing a first embodiment in which the present invention is applied to laser processing for forming a through hole in a ceramic green sheet used when manufacturing a multilayer chip inductor.

FIG. 3 is a diagram showing a second embodiment in which the present invention is applied to laser processing for forming via holes for conductor columns on a circuit board having a multilayer structure.

FIG. 4 is a diagram showing a third embodiment in which the present invention is applied to laser processing for forming a via hole for a conductor column in a resin layer of a circuit board.

FIG. 5 is a view showing a fourth embodiment in which the present invention is applied to laser processing for forming via holes for conductor columns having different depths on a circuit board having a multilayer structure.

[Explanation of symbols]

LB: laser beam, 11: green sheet, 11a: first material layer, 11b: second material layer, SH: through hole,
21 circuit board, 21a first material layer, 21b second material layer, 21c third material layer, 21d fourth material layer, IP
... conductor layer, VH ... via hole, CC ... conductor column, 3
DESCRIPTION OF SYMBOLS 1 ... Circuit board, 32 ... Resin layer, CP ... Conductive layer, 33 ... Mask, 31a ... 1st material layer, 31b ... 2nd material layer, 31
c: third material layer, VH: via hole, CC: conductor column, 41: circuit board, IP1, IP2: conductor layer, 42:
Mask, 41a: first material layer, 41b: second material layer, 4
1c: third material layer, VH1, VH2: via hole, C
C1, CC2 ... conductor columns.

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Hiroshi Takahashi 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. F-term (reference) 4E068 AF01 CF04 DA11 DA14 DB10 DB12

Claims (14)

[Claims] An object to be processed is prepared by laminating a plurality of material layers having different absorption coefficients of laser light in the order of magnitude of the absorption coefficient. A predetermined processing is performed on a portion to be processed by irradiating a laser beam toward the laser processing method. 2. The laser processing method according to claim 1, wherein each of the material layers constituting the portion to be processed is made of unfired or fired ceramics. 3. The laser processing method according to claim 1, wherein each of the material layers constituting the portion to be processed is made of resin. 4. The laser processing method according to claim 1, wherein the portion to be processed constitutes at least a part of a circuit board. 5. A workpiece for laser processing, comprising at least a workpiece to be formed by laminating a plurality of material layers having different absorption coefficients of laser light in the order of magnitude of the absorption coefficient. 6. The workpiece for laser processing according to claim 5, wherein each of the material layers constituting the workpiece is made of unfired or fired ceramics. 7. The workpiece for laser processing according to claim 5, wherein each material layer constituting the workpiece is made of resin. 8. The workpiece for laser processing according to claim 5, wherein the workpiece is a circuit board. 9. A mask is prepared by laminating a plurality of material layers having different absorption coefficients of laser light in the order of magnitude of the absorption coefficient, and the material layer having the largest absorption coefficient is defined as the work piece. The mask is pierced by irradiating a laser beam toward the material layer with the smallest extinction coefficient of the mask, and simultaneously irradiating the workpiece with the laser beam through the perforation. Performing a predetermined processing on the laser processing method. 10. The laser processing method according to claim 9, wherein each material layer constituting the mask is made of unfired or fired ceramics. 11. The laser processing method according to claim 9, wherein each material layer forming the mask is made of a resin. 12. A mask for laser processing, wherein a plurality of material layers having different absorption coefficients of laser light are laminated in the order of the absorption coefficient. 13. The laser processing mask according to claim 12, wherein each material layer constituting the mask is made of unfired or fired ceramics. 14. The laser processing mask according to claim 12, wherein each material layer forming the mask is made of resin.