JP2018177573A - Method for manufacturing insulating substrate having hole and method for forming hole in insulating substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an insulating substrate having a hole, capable of significantly suppressing cracks.SOLUTION: The method for manufacturing an insulating substrate having a hole using an ultrashort pulse laser comprises the steps of: (1) emitting the pulse of a first ultrashort pulse laser called as a main pulse toward a hole formation target position of the insulating substrate; and (2) emitting the pulse of a second ultrashort pulse laser called as a first sub-pulse toward the hole formation target position within 1 ns after starting the step (1). The first sub-pulse has an intensity smaller than that of the main pulse.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a method of manufacturing an insulating substrate having a hole, and a method of forming a hole in the insulating substrate.

  There is widely known a method of forming holes in an insulating substrate by irradiating the insulating substrate such as a glass substrate with a laser. Recently, it has been proposed to use an "ultrashort pulse laser" as a hole processing laser.

  The ultrashort pulse laser means a pulse laser having a pulse width of 100 psec (picosecond) or less.

  It has been reported that when such an ultrashort pulse laser is used, holes can be formed by a so-called ablation process without substantially damaging the insulating substrate.

Akinori Otsu et al., "Influence of stress wave on crack formation in drilling of glass by ultrashort pulse laser," Proceedings of 2017 Spring Conference, Spring Conference, p. 453-454

  However, when the present inventors actually perform hole processing on a glass substrate using an ultrashort pulse laser, a crack such as a fish bone may occur around the hole, a so-called "fish bone crack" I noticed that (Non-Patent Document 1).

  Such cracks may reduce the pore quality, and it is desirable to suppress them as much as possible.

  The present invention has been made in view of such a background, and the present invention provides a method of manufacturing a holed insulating substrate capable of significantly suppressing cracks such as fish bones. To aim. Another object of the present invention is to provide a method of forming a hole in an insulating substrate which can significantly suppress a crack such as a fish bone.

In the present invention, a method of manufacturing an insulating substrate having holes using an ultrashort pulse laser,
(1) emitting a pulse of a first ultrashort pulse laser, which is referred to as a main pulse, toward a hole formation target position of the insulating substrate;
(2) A step of emitting a pulse of a second ultra-short pulse laser called a first sub-pulse toward the hole formation target position within 1 nsec after starting the step (1); ,
Have
A method is provided, characterized in that the first sub-pulse is smaller in intensity than the main pulse.

Further, in the present invention, a method of forming holes in an insulating substrate using an ultrashort pulse laser,
(1) emitting a pulse of a first ultrashort pulse laser, which is referred to as a main pulse, toward a hole formation target position of the insulating substrate;
(2) A step of emitting a pulse of a second ultra-short pulse laser called a first sub-pulse toward the hole formation target position within 1 nsec after starting the step (1); ,
Have
A method is provided, characterized in that the first sub-pulse is smaller in intensity than the main pulse.

  According to the present invention, it is possible to provide a method of manufacturing a holed insulating substrate capable of significantly suppressing cracks such as fish bones. Further, the present invention can provide a method of forming holes in an insulating substrate which can significantly suppress cracks such as fish bones.

It is the figure which showed the simulation result of the stress distribution which generate | occur | produces in a glass substrate at the time of a super-short pulse laser being irradiated to a glass substrate. FIG. 7 schematically shows a temporal relationship between main pulses and sub-pulses emitted toward the irradiated position of the insulating substrate according to an embodiment of the present invention. FIG. 7 schematically shows a temporal relationship between a main pulse emitted toward an irradiated position of the insulating substrate and a plurality of sub-pulses according to another embodiment of the present invention. FIG. 5 schematically shows a flow of a method of manufacturing an insulating substrate having holes according to an embodiment of the present invention. It is the figure which showed typically an example of the form (A) of the main pulse of a main laser, and the form (BD) of the subpulse of a sublaser. It is the figure which showed typically a mode when the main pulse (A) and the 1st sub pulse (B) are repeatedly emitted with a fixed period. It is sectional drawing which showed typically the form of the insulated substrate used by simulation. It is the graph which showed the stress change curve at the time of irradiating only a main laser to an insulating substrate. It is the graph which showed the stress change curve at the time of irradiating a main laser and a sub laser to an insulating substrate. It is the figure which showed the stress distribution in the front-end | tip part of a hole after 70 psec progress, after irradiating a main laser to an insulated substrate.

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

(About the mechanism of crack occurrence)
As described above, when the hole processing by the ultrashort pulse laser is performed on the insulating substrate, a crack such as a fish bone may occur around the hole.

  In order to cope with such problems, the inventors of the present invention have conducted intensive studies on the causes of cracks. As a result, the inventors of the present invention have found that the crack is likely to be caused by a shock wave generated in the insulating substrate during laser irradiation.

  Hereinafter, the generation mechanism of the crack will be described with reference to FIG.

  In FIG. 1, the simulation result of the stress distribution which generate | occur | produces in a glass substrate at the time of an ultra-short pulse laser being irradiated to a glass substrate is shown. The cross section of the glass substrate which has a substantially hemispherical recessed part (hole) is expanded and shown by FIG. In FIG. 1, a portion with strong black indicates that a compressive stress is generated, and a portion with strong white indicates that a tensile stress is generated.

  FIG. 1 (a) shows a stress distribution 1 psec after the holes in the glass substrate are irradiated with the ultrashort pulse laser. FIG. 1 (b) shows the stress distribution 160 psec after the holes of the glass substrate were irradiated with the ultrashort pulse laser. FIGS. 1 (c) and 1 (d) show stress distributions after 1 nsec and 4 nsec, respectively, after irradiating the holes of the glass substrate with the ultrashort pulse laser. FIG. 1 (e) shows an enlarged view of the tip of the hole in FIG. 1 (b).

  It can be seen from FIGS. 1 (b) and 1 (e) that compressive stress (black part) is generated around the hole 160 psec after irradiation with the ultrashort pulse laser. Further, it can be seen that a tensile stress area (white portion) is present immediately above the compressive stress area. Furthermore, it can be seen from FIG. 1 (c) and FIG. 1 (d) that the tensile stress existing region radially propagates to the inside of the glass substrate with time.

  Thus, it can be seen that a significant stress distribution is generated at the irradiation position of the ultrashort pulse laser within a short time on the order of picoseconds (psec) to nanoseconds (nsec) due to the shock wave.

  Here, in general, it is known that tensile stress is likely to cause a crack. Accordingly, from the results of FIG. 1, it is considered that, even when the insulating substrate is irradiated with the ultrashort pulse laser, this tensile stress is a starting point, cracks are generated around the hole, and this radially propagates.

  The inventors of the present invention have carried out intensive studies on crack prevention measures based on such a crack generation mechanism. As a result, the inventors of the present invention have found that the crack can be prevented or suppressed by taking measures to reduce the tensile stress generated around the hole due to the shock wave as described above, and came to the present invention.

That is, in one embodiment of the present invention:
A method of manufacturing an insulating substrate having holes using an ultrashort pulse laser, comprising:
(1) emitting a pulse of a first ultrashort pulse laser, which is referred to as a main pulse, toward a hole formation target position of the insulating substrate;
(2) A step of emitting a pulse of a second ultra-short pulse laser called a first sub-pulse toward the hole formation target position within 1 nsec after starting the step (1); ,
Have
A method is provided, characterized in that the first sub-pulse is smaller in intensity than the main pulse.

Also, in one embodiment of the present invention,
A method of forming a hole in an insulating substrate using an ultrashort pulse laser,
(1) emitting a pulse of a first ultrashort pulse laser, which is referred to as a main pulse, toward a hole formation target position of the insulating substrate;
(2) A step of emitting a pulse of a second ultra-short pulse laser called a first sub-pulse toward the hole formation target position within 1 nsec after starting the step (1); ,
Have
A method is provided, characterized in that the first sub-pulse is smaller in intensity than the main pulse.

  As described above, when the insulating substrate is irradiated with the ultrashort pulse laser, a tensile stress corresponding to the compressive stress is generated at the irradiated position within a short time of n sec or less. This tensile stress can be a cause of cracking.

  On the other hand, in the method according to one embodiment of the present invention, the second ultrashort pulse laser is emitted at a predetermined timing after the first ultrashort pulse laser is emitted.

  The second ultrashort pulse laser generates a compressive stress at the irradiation position by the second ultrashort pulse laser before or simultaneously with the generation of a tensile stress at the irradiation position by the first ultrashort pulse laser It is emitted at such timing.

  In this case, the tensile stress that can be generated by the first ultrashort pulse laser can be offset or reduced by the compressive stress generated by the second ultrashort pulse laser.

  This feature will be described in more detail below with reference to FIG.

  In the following description, the first ultrashort pulse laser is also referred to as "main laser", and the second ultrashort pulse laser is also referred to as "(first) sub-laser". The main laser is a laser intended for hole processing by ablation, and the sub-laser is a laser intended to reduce tensile stress that can be generated by the main laser. However, irradiation with the sub laser may cause hole processing by ablation.

  FIG. 2 schematically shows the temporal relationship between the main laser and the sub laser emitted toward the irradiated position of the insulating substrate. In FIG. 2, the horizontal axis is time t, and the vertical axis is pulse intensity I.

As shown in FIG. 2, the main laser, as pulse 110 of intensity I _1, and is emitted toward the irradiated position. Hereinafter, the pulse 110 is referred to as a main pulse 110.

Intensity I ₁ of the main pulse 110, when the main pulse 110 is irradiated on the insulating substrate, the energy density exceeds the threshold of ablation of the insulating substrate is selected so as to obtain.

  As described above, when the sub-laser irradiation process is not performed after the main laser irradiation, the main laser generates a large tensile stress at the irradiated position of the insulating substrate, which increases the possibility of the generation of a crack.

  However, in one embodiment according to the present invention, as shown in FIG. 2, after emission of the main pulse 110 of the main laser, the pulse 120 of the sub laser is emitted at a predetermined timing toward the irradiated position. Hereinafter, the pulse 120 is referred to as a sub-pulse 120.

  In this case, the tensile stress (hereinafter referred to as “first tensile stress”) that may be generated by irradiation of the main laser is offset or reduced by the compressive stress (hereinafter referred to as “second compressive stress”) generated by irradiation of the sublaser. can do.

Here, the emission start time of the main pulse 110 of the main laser is t _1s , and the emission completion time is t _1e . Further, the time at which the intensity I of the main pulse 110 of the main laser is maximum is taken as t _{1 p} . In the usual case, t _{1 p} = (t _1s + t _1e ) / 2.

Similarly, let the emission start time of the sub-pulse 120 of the sub-laser be t _{2 s,} and let the emission completion time be t _{2 e} . Further, the time at which the intensity I of the sub-pulse 120 of the sub-laser becomes maximum is t 2 _p . In the usual case, t _{2 p} = (t _2s + t _2e ) / 2.

Thus, when each time is defined, the timing at which the sub-pulse 120 of the sub-laser 120 is emitted is adjusted such that the time difference Δt represented by Δt = t _{2 s} −t _{1 s} becomes 1 nsec or less. That is, the sub pulse 120 of the sub laser is emitted within 1 nsec after the main pulse 110 of the main laser is emitted.

  The time difference Δt is preferably in the range of 10 psec to 100 psec.

  By adjusting the time difference Δt in this manner, the second compressive stress can be applied to the irradiated position by the sub laser before or simultaneously with the generation of the first tensile stress at the irradiated position of the insulating substrate due to the irradiation of the main laser. Can be generated. Further, this makes it possible to offset or reduce the first tensile stress by the second compressive stress, and as a result, it is possible to significantly suppress the problem of the occurrence of a crack around the hole.

In the example shown in FIG. 2, t 1 _e <t _{2 s,} that is, the main pulse 110 of the main laser and the sub pulse 120 of the sub laser do not mutually temporally overlap. However, this is merely an example, and at least a portion of the main pulse 110 of the main laser and the sub pulse 120 of the sub laser may overlap in time. For example, t 1 _e > t _{2 s} may be used. Further, t 1 _e > t _{2 e} may be _satisfied .

  By the way, also by the irradiation of the sub-laser, a tensile stress (hereinafter, referred to as “second tensile stress”) paired with the second compressive stress can be generated at the irradiated position. The second tensile stress may cause a crack.

Accordingly, in one embodiment of the present invention, as shown in FIG. 2, the intensity I ₂ of the sub-pulses 120 Sabureza is chosen to be less than the intensity I ₁ of the main pulse 110 of the main laser. For example, the intensity _{I 2} of the sub-pulses 120 Sabureza is 80% or less of the intensity _{I 1} of the main pulse 110 of the main laser.

  In this case, the second tensile stress that can be generated in the insulating substrate by the irradiation of the sub-laser can be smaller than the first tensile stress. Therefore, the possibility of the occurrence of a crack due to the irradiation of the sub laser can be significantly suppressed.

Intensity _{I 2} of the sub-pulses 120 Sabureza is preferably at least 5% of the intensity _{I 1} of the main pulse 110 of the main laser. In particular, the intensity I ₂ of the sub-pulses 120 Sabureza is preferably larger than the energy density exceeding processing threshold of the insulating substrate.

In addition, in irradiation of a single sub pulse as shown in FIG. 2, it may be difficult to adjust the reduction effect of the 1st tensile stress which may arise by irradiation of a main laser with high precision. For example, a the intensity I ₂ sub-pulses 120 Sabureza becomes too small, to sufficiently reduce the first tension stress is difficult. Alternatively, if the intensity I ₂ of the sub-laser sub-pulse 120 becomes too large, although the first tensile stress can be offset by the second compressive stress, the irradiation of the sub-laser leaves a large second tensile stress there is a possibility.

  In such a case, multiple sub-pulses may be used.

  Hereinafter, with reference to FIG. 3, an aspect using such a plurality of sub-pulses will be described.

  FIG. 3 schematically shows the temporal relationship between the main laser and the plurality of sub-lasers emitted toward the irradiated position of the insulating substrate. In FIG. 3, the horizontal axis is time t, and the vertical axis is pulse intensity I.

  As shown in FIG. 3, in this example, three sub-pulses 220, 230, 240 are used. That is, after the main pulse 210 of the main laser is emitted, the first sub pulse 220, the second sub pulse 230, and the third sub pulse 240 are sequentially emitted.

  The sublasers emitting the respective subpulses 220 to 240 may be the same ultrashort pulse laser or different ultrashort pulse lasers.

The first sub-pulse 220 has a strength _{I 2,} the second sub-pulse 230 has a strength _{I 3,} the third sub-pulse 240 has an intensity _{I 4.}

As shown in FIG. 3, the intensity I ₂ is preferably greater than the intensity I ₃ . The intensity _{I 3} is preferably larger than the intensity _{I 4.} That is, when using a plurality of sub-pulses, it is generally preferred that the sub-pulses have a smaller intensity than the immediately preceding one.

For example, the intensity _{I 4} is 80% or less of the intensity _{I 3,} the intensity _{I 3} may be 80% or less of the intensity _{I 2.}

  With such a strength relationship, when a plurality of sub-pulses 220 to 240 are sequentially emitted, the tensile stress that can be generated at the irradiated position by the irradiation of the immediately preceding sub-pulse can be reduced by the compressive stress generated by the next sub-pulse irradiation. .

Also in this case, the time between the main pulse 210 of the main laser and the first sub pulse 220 of the sub laser is adjusted to be 1 nsec or less. That is, assuming that the emission start time of the main pulse 210 of the main laser is t _1s, and the emission start time of the first subpulse 220 of the sublaser is t _2s , the time difference Δt represented by t _2s -t _1s is ₁ nsec or less Adjusted to be

Similarly, assuming that the emission start time of the second sub-pulse 230 is t _{3 s} and the emission start time of the third sub-pulse 240 is t _{4 s} , the interval between the emission start times of adjacent sub-pulses is 1 nsec or less Adjusted to That is, the time differences Δt _a represented by t _{3 s} −t _{2 s} and the time differences Δt _b represented by t _{4 s} −t _{3 s} are both adjusted to 1 nsec or less.

  Thus, in the method of emitting a plurality of sub-pulses 220 to 240 subsequently to the main pulse 210 of the main laser, it is possible to more accurately reduce the respective tensile stress which may be generated by the irradiation of the main laser and the sub-laser. Become.

  The number of sub-pulses of the sub-laser following the main pulse 210 of the main laser is not particularly limited, and the number of sub-pulses may be, for example, two, four, five, six, seven or eight .

Method of manufacturing an insulating substrate having a hole according to an embodiment of the present invention
Next, with reference to FIG. 4, a method of manufacturing an insulating substrate having holes according to an embodiment of the present invention (hereinafter, referred to as “first method”) will be described.

  FIG. 4 schematically shows the flow of the first method.

As shown in FIG. 4, the first method is
(1) A step of emitting a main pulse toward a hole formation target position of the insulating substrate (step S110);
(2) A step (step S120) of emitting a sub-pulse toward the hole formation target position within 1 nsec after starting the step (1);
(3) repeating the steps (1) and (2) a predetermined number of times (step S130);
Have.

  Each step will be described below.

(Step S110)
First, an insulating substrate for processing is prepared.

  The material of the insulating substrate is not particularly limited. The insulating substrate may be, for example, a glass substrate or a ceramic substrate.

  The shape of the insulating substrate is not particularly limited. The insulating substrate may be rectangular or circular. Also, the dimensions of the insulating substrate are not particularly limited. The insulating substrate may have a thickness of, for example, 0.1 mm or more.

  Next, a first ultrashort pulse laser is irradiated to the target hole formation position of the insulating substrate.

  As described above, the ultrashort pulse laser means a pulse laser having a pulse width of 100 psec or less of the emitted pulse. The pulse width is preferably in the range of several fsec (femtoseconds) to several psec.

  The first ultra-short pulse laser is irradiated to form holes in the insulating substrate by an ablation processing method. As mentioned above, the first ultra-short pulse laser is also referred to as "main laser". The pulse of the first ultrashort pulse laser is also referred to as "main pulse".

  FIG. 5A shows an example of the form of the main pulse of the main laser. The horizontal axis is time t, and the vertical axis is pulse intensity I.

As shown in FIG. 5A, the emission start time of the main pulse 310 is t _1s , and the emission completion time is t _1e . Further, the time for obtaining the maximum intensity of the main pulse 310 is t _{1 p} .

Intensity I ₁ of the main pulse 310, the irradiation of the main pulse 310, the hole formation target position, energy density exceeds the threshold of ablation of the insulating substrate is selected so as to obtain.

(Step S120)
Next, a second ultra-short pulse laser is irradiated to the position of the insulating substrate where the main pulse is irradiated, that is, the hole formation target position.

  The second ultra-short pulse laser is irradiated to reduce the first tensile stress that may be generated at the target hole formation position by the irradiation of the main laser in step S110. That is, the second tensile stress generated when the second ultra-short pulse laser is irradiated to the hole formation target position cancels or reduces the first tensile stress which may be generated by the irradiation of the main laser.

  As mentioned above, the second ultra-short pulse laser is also referred to as "first sub-laser". Also, the pulse of the second ultrashort pulse laser is also referred to as "first sub-pulse".

  FIG. 5B shows an example of the form of the first sub-pulse of the first sub-laser. The horizontal axis is time t, and the vertical axis is pulse intensity I. FIG. 5 (B) is shown such that the horizontal axis coincides with the time axis in FIG. 5 (A).

As shown in FIG. 5B, the emission start time of the first sub-pulse 320 is t _{2 s} , and the emission completion time is t _{2 e} . Also, the time for obtaining the maximum intensity of the first sub-pulse 320 is t 2 _p .

The intensity I ₂ of the first sub-pulse 320 is selected to be smaller than the intensity I ₁ of the main pulse 310. For example, the intensity _{I 2} of the first sub-pulse 320 is 80% or less of the strength _{I 1} of the main pulse 310, is preferably 50% or less.

Intensity I ₂ of the first sub-pulse 320, the irradiation of the first sub-pulse 320, the hole formation target position, preferably the energy density which exceeds the threshold of ablation of the insulating substrate is selected so as to obtain.

Here, the time difference Δt between the emission start time t _{1 s} of the main pulse 310 and the emission start time t _{2 s} of the first sub-pulse 320 is 1 nsec or less. The time difference Δt is preferably in the range of 10 psec to 100 psec.

  Thus, when the time difference Δt is adjusted, the second pulse is generated by the corresponding first sub-pulse 320 before or simultaneously with the generation of the first tensile stress at the target hole formation position of the insulating substrate at the time of irradiation of the main pulse 310. Compressive stress can be generated. In addition, this makes it possible to offset or reduce the first tensile stress by the second compressive stress, and as a result, it is possible to significantly suppress the problem of the occurrence of a crack around the hole.

  Here, as described above, in the case of irradiation of only the first sub pulse 320, it may be difficult to adjust with high accuracy the reduction effect of the first tensile stress that may occur due to the irradiation of the main laser.

  In such a case, multiple sub-pulses may be used.

  Hereinafter, with reference to FIGS. 5C and 5D, an example in which a plurality of sub-pulses are used will be described.

  FIG. 5C shows an example of the form of the second sub-pulse. Further, FIG. 5D shows an example of the form of the third sub-pulse. The horizontal axis is time t, and the vertical axis is pulse intensity I.

  5 (C) and 5 (D) are shown such that the horizontal axis coincides with the time axis in FIGS. 5 (A) and 5 (B).

  As shown in FIG. 5C, subsequently to the first sub-pulse 320, a second sub-pulse 330 is emitted from the third ultra-short pulse laser (second sub-laser).

The emission start time of the second sub-pulse 330 is t _{3 s} , and the emission completion time is t 3 _e . The time up to the intensity _{I 3} of the third sub-pulse 330 is _obtained, a _{t 3p.}

  Further, as shown in FIG. 5D, subsequently to the second sub-pulse 330, the third sub-pulse 340 is emitted from the fourth ultra-short pulse laser (third sub-laser).

The emission start time of the third sub-pulse 340 is t _{4 s} , and the emission completion time is t 4 _e . Also, the time for obtaining the maximum intensity I ₄ of the third sub-pulse 340 is t _{4 p} .

Here, the emission start time _{t 2s} of the first sub-pulse 320, the time difference Delta] t ₂ between the emission start time _{t 3s} of the second sub-pulse 330 is less 1 nsec. The time difference Δt ₂ is preferably in the range of 10 psec to 100 psec.

Similarly, the emission start time _{t 3s} of the second sub-pulse 330, the time difference Delta] t ₃ between the extraction start time _{t 4s} of the third sub-pulse 340 is less 1 nsec. The time difference Δt ₃ is preferably in the range of 10 psec to 100 psec.

Also, the intensity I ₃ of the second sub pulse 330 is selected to be smaller than the intensity I ₂ of the first sub pulse 320. For example, the intensity _{I 3} of the second sub-pulse 330 is 80% or less of the intensity _{I 2} of the first sub-pulse 320, is preferably 50% or less.

Similarly, the intensity I ₄ of the third sub-pulse 340 is selected to be smaller than the intensity I ₃ of the second sub-pulse 330. For example, the intensity _{I 4} of the third sub-pulse 340 is 80% or less of the intensity _{I 3} of the second sub-pulse 330, is preferably 50% or less.

The intensity I ₄ of the third sub-pulse 340, the irradiation of the third sub-pulse 340, the hole forming target location is preferably selected so that the energy density is obtained exceeding a threshold of ablation of the insulating substrate .

  Thus, when the plurality of sub-pulses 320 to 340 are used, it is possible to adjust the reduction amount of the tensile stress which may occur in the insulating substrate with higher accuracy.

  The sub lasers emitting the sub pulses 320 to 340 may be the same or different. For example, the first sub-laser may be identical to the second sub-laser or the third sub-laser, and the second sub-laser may be identical to the third sub-laser.

(Step S130)
Next, if necessary, the aforementioned steps S110 and S120 are repeated a predetermined number of times.

  Thereby, even when the depth of the holes is large, it is possible to form a hole of a predetermined depth.

  Step S130 may be implemented by repeatedly emitting the main pulse 310 of the main laser and the first sub-pulse 320 of the first sub-laser at a constant cycle. If necessary, further second sub-pulses 330 and third sub-pulses 340 may be emitted repeatedly.

  FIG. 6 schematically shows a timing chart when the main pulse 310 and the first sub-pulse 320 are repeatedly emitted at a constant cycle.

As shown in FIG. 6 (A), the main pulse 310 is repeatedly emitted by the period _{T 1.} Note that FIG. 6A shows a first main pulse 310 and a second main pulse 310. However, after the second main pulse 310, one or more main pulses may be repeatedly emitted.

As described above, the emission start time, emission completion time, and time for obtaining the maximum intensity of the first main pulse 310 are t _1s , t _1e and t _1p , respectively.

In addition, the emission start time of the second main pulse 310 is q _{1 s} , and the emission completion time is q 1 _e . The time for which the maximum intensity of the second main pulse 310 is obtained is q _{1 p} .

Period _{T 1} of the main pulse 310 is preferably normally 1msec or less. The period _{T 1,} the interval of time up pulse intensity _{I 1} between the main pulse 310 adjacent obtained, i.e. defined as _q 1p _{-t 1p.} The periods of the other pulses are similarly determined.

On the other hand, as shown in FIG. 6 (B), the first sub-pulse 320 is repeatedly emitted by the period _{T 2.} The first sub-pulse 320 and the second sub-pulse 320 are shown in FIG. 6 (B). However, one or more sub-pulses may be repeatedly emitted after the second sub-pulse 320.

As described above, the emission start time, the emission completion time, and the time to obtain the maximum intensity of the first sub-pulse 320 are t _2s , t _2e and t _2p , respectively.

Further, the emission start time of the second sub pulse 320 is q _{2 s} , and the emission completion time is q _{2 e} . Also, the time for obtaining the maximum intensity of the second sub pulse 320 is q 2 _p .

The period T _{2 of the} sub pulse 320 is equal to the period T ₁ of the main pulse 310 in the normal case.

Incidentally, the emission start time of the second main pulse 310 _{q 1s,} the time difference Δq between the exit start time _{q 2s} of the second sub-pulse 320 is less 1 nsec. The time differences Δt and Δq are preferably in the range of 10 psec to 100 psec.

  When the time differences Δt and Δq are adjusted in this manner, the corresponding first sub-pulse is applied before or simultaneously with the generation of the first tensile stress at the target hole formation position of the insulating substrate at each irradiation of the main pulse. As a result, the second compressive stress can be generated. In addition, this makes it possible to offset or reduce the first tensile stress by the second compressive stress, and as a result, it is possible to significantly suppress the problem of the occurrence of a crack around the hole.

  Through the above-described steps, an insulating substrate having holes can be obtained. The holes to be formed may be through holes or non-through holes. The diameter of the holes is not particularly limited, but may be, for example, in the range of 1 μm to 500 μm.

  Note that step S130 does not necessarily have to be performed, and may be omitted. That is, in the first manufacturing method, the number of emission of the main pulse 310 and the number of emission of the first sub-pulse 320 (further, the second sub-pulse 330 and the third sub-pulse 340) may be one each. .

  The configuration and features of the present invention have been described above by the embodiments of the present invention. However, the present invention is not limited to these embodiments, and it is obvious to those skilled in the art that various modifications can be assumed.

  For example, in the above description, the features of the present invention have been described assuming a method for manufacturing an insulating substrate having holes. However, the present invention can also be applied to a method of forming holes in an insulating substrate.

  In the present application, the “hole” is not necessarily limited to the form having the substantially circular opening, and the “hole” may include a hole having the substantially rectangular or substantially polygonal opening.

  Hereinafter, examples of the present invention will be described.

  The stress distribution produced when the insulating substrate was irradiated with the ultrashort pulse laser was evaluated by simulation analysis according to the first method described above. The sub-pulses were assumed to be of one type (ie, only the first sub-pulse), and the main pulse and the sub-pulse were emitted once each.

  The parameter values shown in Table 1 below were adopted as preconditions for the simulation.

In FIG. 7, the cross-sectional form of the insulated substrate used by simulation is shown.

  As shown in FIG. 7, this insulating substrate 400 has a substantially hemispherical hole 410 on the surface. The diameter of the hole 410 is 20 μm, and the depth is 10 μm. Assuming the insulating substrate 400 of such a form, the stress change occurring at the tip end 412 of the hole 410 was calculated.

  For the simulation, calculation was performed using an axisymmetric element model using a general analysis program ABAQUS (manufactured by Dassault Systèmes).

  For comparison, calculation was also performed on the stress change when the sub laser is not used, that is, when only the main pulse of the main laser is irradiated once.

  FIG. 8 shows a stress change curve 480 when the insulating substrate 400 is irradiated with only the main laser. In FIG. 8, the horizontal axis is time t, and the vertical axis is stress.

  It can be seen from FIG. 8 that compressive stress is generated in the hole 410 of the insulating substrate 400 immediately after the main laser irradiation (time 0). This compressive stress increases with time and reaches a maximum after about 10 psec. Thereafter, the compressive stress starts to decrease, and after about 30 psec, the compressive stress disappears. As time passes further, tensile stress starts to develop, and the tensile stress shows a maximum value of 20.4 GPa after about 48 psec.

  When such a stress change occurs at the tip end portion 412 of the hole 410 of the insulating substrate 400, a crack is generated around the hole 410 when the tensile stress exceeds the fracture stress threshold of the insulating substrate 400.

  On the other hand, FIG. 9 shows a stress change curve 490 when the sub laser is irradiated 38 psec after the start of the main laser irradiation. In FIG. 9, the stress change curve 480 of FIG. 8 described above is shown in an overlapping manner for comparison.

  It can be seen from FIG. 9 that the maximum value of the tensile stress is significantly reduced when the sub-laser is used (stress change curve 490) compared to the stress change curve 480 when the sub-laser is not used. That is, the maximum value of the tensile stress is about 10.7 GPa, which is about 48% lower than the maximum value of the tensile stress shown in FIG.

  FIG. 10 shows a stress distribution at the tip portion 412 of the hole 410 after 70 psec has elapsed since the insulating substrate 400 was irradiated with the main laser. FIG. 10A shows a stress distribution when the sub laser is not used, and FIG. 10B shows a stress distribution when the sub laser is used.

  From FIG. 10A, it can be seen that a tensile stress area (white portion) exists immediately below the hole 410 when the sub laser is not used. On the other hand, in FIG. 10 (B), no remarkable tensile stress region is observed at the same place.

  As described above, it was confirmed that the tensile stress that can be generated in the insulating substrate 400 can be significantly suppressed by irradiating the sub-laser at a predetermined timing after the irradiation of the main laser.

110 main pulse 120 sub pulse 210 main pulse 220 first sub pulse 230 second sub pulse 240 third sub pulse 310 main pulse 320 first sub pulse 330 second sub pulse 340 third sub pulse 400 insulating substrate 410 hole 412 tip 480 Stress change curve 490 Stress change curve

Claims (9)

A method of manufacturing an insulating substrate having holes using an ultrashort pulse laser, comprising:
(1) emitting a pulse of a first ultrashort pulse laser, which is referred to as a main pulse, toward a hole formation target position of the insulating substrate;
(2) A step of emitting a pulse of a second ultra-short pulse laser called a first sub-pulse toward the hole formation target position within 1 nsec after starting the step (1); ,
Have
The method according to claim 1, wherein the first sub-pulse is smaller in intensity than the main pulse.   The method according to claim 1, wherein the first sub-pulse is irradiated to the target hole formation position with an energy density exceeding an ablation processing threshold of the insulating substrate.   The method according to claim 1, wherein the first sub-pulse is irradiated to the target hole formation position at an intensity of 80% or less of the intensity of the main pulse. The step (2) includes the step of further emitting a plurality of sub-pulses after the emission of the first sub-pulse,
4. A method according to any one of the preceding claims, wherein each sub-pulse has a smaller intensity than the immediately preceding sub-pulse.   The method according to any one of claims 1 to 4, wherein the pulse width of the main pulse is 100 psec or less.   The method according to any one of claims 1 to 5, wherein the pulse width of each sub-pulse is 100 psec or less. Further, after the step (2),
(3) repeating the steps (1) and (2);
The method according to any one of claims 1 to 6, comprising   The method according to claim 7, wherein the step (3) is started within 1 msec after the step (1) is started. A method of forming a hole in an insulating substrate using an ultrashort pulse laser,
(1) emitting a pulse of a first ultrashort pulse laser, which is referred to as a main pulse, toward a hole formation target position of the insulating substrate;
(2) A step of emitting a pulse of a second ultra-short pulse laser called a first sub-pulse toward the hole formation target position within 1 nsec after starting the step (1); ,
Have
The method according to claim 1, wherein the first sub-pulse is smaller in intensity than the main pulse.