JP5442130B2 - Laser processing method - Google Patents

Description

  The present invention relates to a laser processing method.

  A printed wiring board having a structure in which at least three layers of a copper foil, a resin layer, and a copper foil are laminated is irradiated with a UV laser to process the surface copper foil (first conductor layer) and then There is a technique for performing blind hole processing in which the resin layer (insulating layer) in the above is further processed until the lower copper foil (second conductor layer) is exposed.

Patent Document 1 discloses that a conductive layer, an insulating layer containing glass fibers, and a glass-containing substrate (printed wiring substrate) on which a conductive layer is laminated in order are operated with a UV laser beam in a circumferential direction to wind the conductive layer on the surface. After processing, a hole is processed in the insulating layer with a CO ₂ laser through the window, and the residual film at the bottom of the hole is removed with UV laser light. Thereby, according to patent document 1, the chemical desmear process (conditioning, water washing, boiling, cooling, water washing, swelling, water washing, oxidation desmear, water washing, neutralization, water washing, drying for removing the film | membrane which remained in the hole bottom And the like) can be made unnecessary.

JP 2002-118344 A

  In Patent Document 1, it is assumed that the surface conductor layer is processed by circumferential processing (trepanning processing) when drilling a printed wiring board.

  On the other hand, in Patent Document 1, there is no description about the process of irradiating the same portion of the surface conductor layer with a pulse laser multiple times (punching process of the surface conductor layer). Furthermore, Patent Document 1 does not describe how to perform stable drilling when punching a printed wiring board (workpiece) by punching a conductor layer on the surface.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a laser processing method capable of performing stable drilling when drilling a workpiece.

  In order to solve the above-described problems and achieve the object, a laser processing method according to one aspect of the present invention includes a workpiece in which an insulating layer is sandwiched between a first conductor layer and a second conductor layer. A laser processing method for drilling a workpiece with a pulse laser, wherein the same portion of the first conductor layer is irradiated with a pulse laser multiple times to form a first hole penetrating the first conductor layer And a second step of irradiating a portion of the insulating layer exposed by the first hole with a pulsed laser a plurality of times, corresponding to the first hole and penetrating the insulating layer. And a second step of forming a hole, wherein the first step irradiates the same portion a plurality of times with a pulse laser generated at an oscillation frequency of 3 kHz to 15 kHz.

  According to the present invention, in the first step, since the punching process for forming the first hole penetrating the first conductor layer can be stably performed, in the second step, the first hole is formed in the first hole. Accordingly, it is easy to form the second hole penetrating the insulating layer. That is, when drilling a workpiece, stable drilling can be performed.

FIG. 1 is a diagram illustrating a laser processing method according to the first embodiment. FIG. 2 is a diagram showing a workpiece in the first embodiment. FIG. 3 is a diagram showing a relationship between processing conditions and workability in copper foil removal processing. FIG. 4 is a diagram showing the relationship between processing conditions and workability in resin removal processing. FIG. 5 is a diagram illustrating a processing example to which the first embodiment is applied. FIG. 6 is a diagram illustrating another processing example to which the first embodiment is applied. FIG. 7 is a diagram illustrating a laser processing method according to the second embodiment. FIG. 8 is a diagram illustrating a laser processing method according to a comparative example.

  Embodiments of a laser processing method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
A laser processing method according to the first embodiment will be described with reference to FIG. 1A to 1D are process cross-sectional views illustrating the laser processing method according to the first embodiment.

  In the step shown in FIG. 1A, a workpiece 10 is prepared. For example, as shown in FIG. 2A, the workpiece 10 includes a resin layer (insulating layer) 13 between a copper foil (first conductor layer) 11 and a copper foil (second conductor layer) 12. Is a printed wiring board having a three-layer structure in which is sandwiched. The resin layer 13 contains, for example, an epoxy resin or a polyimide resin as a main component.

  In the step shown in FIG. 1B, the same portion 11e in the copper foil 11 is irradiated with a UV pulse laser a plurality of times (ie, punching is performed). Specifically, a UV pulse laser is generated by an oscillator (not shown).

Here, when the oscillation frequency is F [kHz] and the energy density is E [J / mm ² ], 3 ≦ F ≦ 15 in the FE plane (see FIG. 3) Formula 1
0.05 ≦ E ≦ 0.30 Expression 2
A UV pulse laser is generated by an oscillator (not shown) so as to satisfy the above. A region satisfying Equations 1 and 2 is a region PR1 surrounded by a one-dot chain line shown in FIG.

  In the region on the left side of the region PR1 shown in FIG. 3 (0 <F <3), since the heat radiation period between the pulses of the UV pulse laser is too long, the heat for processing the copper foil 11 is insufficient, and the copper foil 11 is processed. It becomes difficult to do. In the region on the right side of the region PR1 shown in FIG. 3 (15 <F), the UV pulse laser of the Nth pulse (N: an integer of 2 or more) is scattered by the irradiation of the UV pulse laser of the (N-1) th pulse. Since it tends to be absorbed or scattered by the sputtering of the copper foil and not efficiently irradiate the copper foil 11, it becomes difficult to process the copper foil 11. In the lower region (E <0.05) of the region PR1 shown in FIG. 3, the energy in each pulse of the UV pulse laser tends to be smaller than the energy (for example, thermal energy) required for processing the copper foil 11. It becomes difficult to process the copper foil 11. In the upper region (0.30 <E) of the region PR1 shown in FIG. 3, the copper foil 11 and the copper foil 12 tend to be peeled off due to excessive evaporation pressure due to overheating of the resin layer 13 below the copper foil 11. Therefore, the quality of the printed wiring board (workpiece) after processing may be deteriorated.

  Further, in the region above the region PR1 shown in FIG. 3 (0.30 <E), the energy density of the UV pulse laser is excessive with respect to the resin, and the resin layer 13 is aggravated (excessive removal). May occur. In this case, there is a possibility that the machining dimension is greatly deviated from the design dimension and the machining quality is deteriorated. Further, it is difficult to selectively process the copper foil 11 by controlling the number of pulses, and the copper foil 12 under the resin layer 13 may be removed along with the resin layer 13 and the blind hole may not be processed. In order to selectively process the copper foil 11 and to reliably process the blind hole, it is necessary to allow for a sufficient energy density and number of pulses in consideration of the thickness variation of the copper foil 11. Also from this point, it is preferable that E ≦ 0.30.

  From the oscillator, a UV pulse laser is emitted at a pulse frequency corresponding to the oscillation frequency (F) satisfying Equation 1. That is, the lower the oscillation frequency, the smaller the pulse frequency of the UV pulse laser emitted from the oscillator. The UV pulse laser emitted from the oscillator is irradiated to the same portion 11e in the copper foil 11 a plurality of times (for example, five times). That is, the 5-pulse UV pulse lasers L <b> 1 to L <b> 5 emitted from the oscillator are sequentially irradiated to the same portion 11 e in the copper foil 11. As a result, a hole (first hole) 11a is formed (see FIG. 1D). The hole 11a is a hole formed by removing the portion 11e in the copper foil 11, and penetrates the copper foil 11i.

  In the step shown in FIG. 1 (c), a portion (the same portion) 13e exposed through the hole 11a in the resin layer 13 is irradiated with a UV pulse laser a plurality of times (that is, punching is performed). Specifically, a UV pulse laser is generated by an oscillator (not shown).

Here, when the oscillation frequency is F [kHz] and the energy density is E [J / mm ² ], 15 <F in the FE plane (see FIG. 3) 15
E <0.05 Formula 4
A UV pulse laser is generated by an oscillator (not shown) so as to satisfy the above. The region satisfying Equation 3 and Equation 4 is a region PR3 surrounded by a broken line shown in FIGS. The region PR3 corresponds to a processing condition in which the copper foil 12 is not removed as shown in FIG. 3, and corresponds to a processing condition in which the resin layer 13 can be removed as shown in FIG. That is, the region PR3 corresponds to a processing condition in which the resin layer 13 can be selectively removed without removing the copper foil 12.

  From the oscillator, a UV pulse laser is emitted at a pulse frequency corresponding to the oscillation frequency satisfying Equation 3. That is, as the oscillation frequency increases, the pulse frequency of the UV pulse laser emitted from the oscillator also increases. The UV pulse laser emitted from the oscillator is irradiated to the portion 13e exposed through the hole 11a in the resin layer 13 a plurality of times (for example, five times). That is, the five pulsed UV pulse lasers L11 to L15 emitted from the oscillator are sequentially irradiated to the portion 13e exposed through the hole 11a in the resin layer 13. Thereby, as shown in FIG.1 (d), while forming the hole (2nd hole) 13a, after the location 12e which should be exposed by the hole 13a in the copper foil 12 is exposed, it is not removed. Remain. The hole 13a is a hole formed by removing the portion 13e exposed from the hole 11a in the resin layer 13, and has a shape and a dimension corresponding to the hole 11a. Further, the hole 13a penetrates the resin layer 13i.

  In this way, as shown in FIG. 1 (d), a blind hole BH1 is formed which includes the hole 11a and the hole 13a and whose hole bottom is closed by the copper foil 12.

  Next, a processing example to which the laser processing method according to the first embodiment is applied will be described with reference to FIG.

  In the step shown in FIG. 5 (a), a copper foil 112 having a thickness of t5 μm, a resin layer 113 having a thickness of t10 μm, and a copper foil 111 having a thickness of t5 μm are sequentially stacked as the workpiece 110 to be processed with the blind hole BH100. A printed wiring board was prepared.

  In the step shown in FIG. 5B, the same portion 111e in the copper foil 111 was irradiated with UV pulse laser five times (5 pulses). Specifically, processing was performed by generating UV pulse lasers L101 to L105 with an oscillator (not shown) under the following processing conditions.

Energy density: 0.07 J / mm ²
Oscillation frequency: 15 kHz
Irradiation area: φ50 μm = 1196 μm ²
Number of pulses: 5
This processing condition satisfied the above-described Expression 1 and Expression 2, and the copper foil 111 could be processed stably. As a result, a hole 111a having a diameter R100 = 50 μm was formed. The hole 111a passes through the copper foil 111i.

  In the step shown in FIG. 5C, the portion 113e exposed by the hole 111a in the resin layer 113 was irradiated with UV pulse laser 10 times (10 pulses). Specifically, processing was performed by generating UV pulse lasers L111 to L120 with an oscillator (not shown) under the following processing conditions.

Energy density: 0.02 J / mm ²
Oscillation frequency: 45kHz
Irradiation area: φ50 μm = 1196 μm ²
Number of pulses: 10
This processing condition satisfied the above-described Expression 3 and Expression 4, and it was possible to stably process the resin layer 113 without removing the copper foil 112. As a result, a hole 113a having a diameter R100 = 50 μm was formed. The hole 113a penetrates the resin layer 113i.

  In this way, as shown in FIG. 5 (d), a blind hole BH100 made up of the hole 111a and the hole 113a and having the hole bottom closed by the copper foil 112 was formed. Similarly, when 100 blind holes were machined in the printed wiring board (workpiece 110), the same blind holes as the hole BH100 could be stably machined in all 100 locations.

  Next, another processing example to which the laser processing method according to the first embodiment is applied will be described with reference to FIG.

  In the process shown in FIG. 6A, as the workpiece 210 to be machined in the blind hole BH200, a copper foil 212 having a thickness t5 μm, a resin layer 213 having a thickness t20 μm, and a copper foil 211 having a thickness t5 μm are sequentially laminated. A printed wiring board was prepared.

  In the step shown in FIG. 6B, the same portion 211e in the copper foil 211 was irradiated with UV pulse laser five times (5 pulses). Specifically, processing was performed by generating UV pulse lasers L201 to L205 with an oscillator (not shown) under the following processing conditions.

Energy density: 0.10 J / mm ²
Oscillation frequency: 15 kHz
Irradiation area: φ50 μm = 1196 μm ²
Number of pulses: 5
This processing condition satisfied the above formulas 1 and 2, and the copper foil 211 could be processed stably. As a result, a hole 211a having a diameter R200 = 50 μm was formed. The hole 211a passes through the copper foil 211i.

  In the step shown in FIG. 6C, the portion 213e exposed through the hole 211a in the resin layer 213 was irradiated with UV pulse laser 15 times (15 pulses). Specifically, processing was performed by generating UV pulse lasers L211 to L225 with an oscillator (not shown) under the following processing conditions.

Energy density: 0.03 J / mm ²
Oscillation frequency: 30 kHz
Irradiation area: φ50 μm = 1196 μm ²
Number of pulses: 15
This processing condition satisfied the above-described Expression 3 and Expression 4, and it was possible to stably process the resin layer 213 without removing the copper foil 212. As a result, a hole 213a having a diameter R200 = 50 μm was formed. The hole 213a passes through the resin layer 213i.

  In this way, as shown in FIG. 6D, a blind hole BH200 including the hole 211a and the hole 213a and having the hole bottom closed by the copper foil 212 was formed. Similarly, when 100 blind holes were machined in the printed wiring board (workpiece 210), the same blind holes as the hole BH200 could be stably machined in all 100 locations.

  Next, an example of processing by the laser processing method according to the comparative example will be described with reference to FIG.

  In the process shown in FIG. 8A, a copper foil 912 having a thickness of t5 μm, a resin layer 913 having a thickness of t10 μm, and a copper foil 911 having a thickness of t5 μm are sequentially stacked as a workpiece 910 whose blind hole is to be processed. A printed wiring board was prepared.

  In the step shown in FIG. 8B, the same portion 911e in the copper foil 911 was irradiated with UV pulse laser five times (5 pulses). Specifically, processing was performed by generating UV pulse lasers L901 to L905 under the following processing conditions by an oscillator (not shown).

Energy density: 0.04 J / mm ²
Oscillation frequency: 25kHz
Irradiation area: φ50 μm = 1196 μm ²
Number of pulses: 5
This processing condition did not satisfy the above-described Expression 1 and Expression 2, and a shallow hole 911a having a depth not penetrating the copper foil 911i was formed.

  In the process shown in FIG. 8C, the hole 911a was irradiated with UV pulse laser 10 times (10 pulses). Specifically, processing was performed by generating UV pulse lasers L911 to L920 with an oscillator (not shown) under the following processing conditions.

Energy density: 0.02 J / mm ²
Oscillation frequency: 45 kHz
Irradiation area: φ50 μm = 1196 μm ²
Number of pulses: 10
This processing condition satisfies Expression 3 and Expression 4 above, but does not satisfy Expression 1 and Expression 2, and a shallow hole 911a that does not penetrate through the copper foil 911i remains.

  In this manner, as shown in FIG. 8D, the shallow hole 911a having a depth not penetrating the copper foil 911i was formed, but the hole penetrating the copper foil 911i could not be formed.

Next, in order to clarify the effect by Embodiment 1, the result of having conducted the experiment is demonstrated using FIG.3 and FIG.4. FIG. 3 is a diagram showing the relationship between the energy density E [J / mm ² ] and the oscillation frequency F [kHz] and the workability in the copper foil removing process. FIG. 4 is a diagram showing the relationship between the energy density E [J / mm ² ] and the oscillation frequency F [kHz] and processability in the resin removal process.

  As shown in FIG. 3, the present inventor has actually used conditions, that is, E = 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.10. F = 2.0, 3.0, 4.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45. For all combinations with 0, processing was carried out by irradiating 5 pulses of UV pulse laser to 100 locations on the copper foil of the printed wiring board.

  As a result, in FIG. 3, the case where the copper foil could not be removed even at one place (that is, a hole penetrating the copper foil could not be formed) is indicated by x, and the copper foil can be removed at all 100 places. (If the hole penetrating the copper foil was formed), the variation in the hole diameter was indicated by Δ, and the copper foil could be removed at all 100 locations. A case where the variation is less than a predetermined value is indicated by ◯.

  For example, in FIG. 3, the processing conditions (F, E) = (15, 0.07) used in the processing example of FIG. 5 to which the first embodiment is applied are indicated by ◯. The processing conditions (F, E) = (15, 0.10) used in the processing example of FIG. 6 to which the first embodiment is applied are indicated by ◯. On the other hand, the processing conditions (F, E) = (25, 0.04) used in the processing example of FIG. 8 according to the comparative example are indicated by x.

  From these results, the present inventor has derived that the region PR1 surrounded by the alternate long and short dash line shown in FIG. 3 is a region corresponding to preferable processing conditions in the copper foil removal processing.

  In addition, as shown in FIG. 4, the inventor has actually used conditions, that is, E = 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0. .10 and F = 3.0, 4.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0 With respect to all the combinations, a process of irradiating 100 pulses on the exposed resin layer of the printed wiring board subjected to the process shown in FIG.

  As a result, in FIG. 3, the case where the resin layer could not be removed even at one place (that is, a hole penetrating the resin layer could not be formed) is indicated by x, and the resin layer can be removed at all 100 places. The case where there was (that is, a hole penetrating the resin layer was formed) is indicated by ◯.

  For example, in FIG. 4, the processing conditions (F, E) = (45, 0.02) used in the processing example of FIG. 5 to which the first embodiment is applied are indicated by ◯. The processing conditions (F, E) = (30, 0.03) used in the processing example of FIG. 6 to which the first embodiment is applied are indicated by ◯. The processing conditions (F, E) = (45, 0.02) used in the processing example of FIG. 8 according to the comparative example are also indicated by ◯.

  From these results, the present inventor confirmed that the resin removal processing was possible under any actual use conditions as shown in FIG.

  Here, suppose a case in which, in the step shown in FIG. 1B, the same location 11e in the copper foil 11 is irradiated a plurality of times with a UV pulse laser generated at an oscillation frequency of less than 3 kHz. In this case, the Nth pulse (N: integer greater than or equal to 2) UV pulse laser tends not to be able to use the effect of heat storage in the copper foil 11 due to the irradiation of the (N-1) th pulse UV pulse laser (pulse frequency Is low, so heat is dissipated). Therefore, the UV pulse laser of the Nth pulse needs a lot of energy because it is necessary to remove the copper foil 11 by the heat generated by the irradiation of the UV pulse laser of the Nth pulse without using the effect of heat storage. . That is, since the heat radiation period between each pulse of the UV pulse laser is too long, the thermal energy necessary for processing the copper foil 11 is insufficient, and it becomes difficult to process the copper foil 11.

  Alternatively, suppose that in the step shown in FIG. 1B, the same location 11e in the copper foil 11 is irradiated a plurality of times with a UV pulse laser generated at an oscillation frequency higher than 15 kHz. In this case, the UV pulse laser of the Nth pulse (N: integer greater than or equal to 2) is absorbed or scattered by the sputter of the copper foil scattered by the irradiation of the UV pulse laser of the (N-1) th pulse. There is a tendency that the foil 11 is not irradiated.

  For example, as shown in FIG. 8, at least a part of the second pulse UV pulse laser L902 is absorbed or scattered by the spatters SP1 to SP7 of the copper foil scattered by the irradiation of the first pulse UV pulse laser L901. At least a part of the pulse laser L903 of the third pulse is absorbed or scattered by the spatters SP11 to SP15 of the copper foil scattered by the irradiation of the UV pulse laser L902 of the second pulse. As a result, it becomes difficult to process the hole penetrating the copper foil 911 (copper foil 11).

  On the other hand, in the first embodiment, in the process shown in FIG. 1B, the UV pulse laser generated at an oscillation frequency of 3 kHz or more and 15 kHz or less is irradiated to the same portion 11e in the copper foil 11 a plurality of times. Thereby, since the punching process which forms the hole 11a which penetrates the copper foil 11 can be performed stably (refer FIG. 3), it corresponds to the hole 11a in the process shown in FIG. It is also easy to stably form the hole 13 a penetrating the hole 13. That is, when drilling the workpiece 10 (that is, when processing the blind hole BH1 including the hole 11a and the hole 13a), stable drilling can be performed.

Alternatively, suppose that a pulse laser generated at an energy density smaller than 0.05 J / mm ² is irradiated to the same portion 11e in the copper foil 11 a plurality of times in the step shown in FIG. In this case, the energy in each pulse of the UV pulse laser tends to be smaller than the energy required for processing the copper foil 11 (for example, thermal energy), making it difficult to process the copper foil 11.

On the other hand, in the first embodiment, in the step shown in FIG. 1B, the same spot 11e in the copper foil 11 is irradiated a plurality of times with a pulse laser generated at an energy density of 0.05 J / mm ² or more. Thereby, since the energy in each pulse of the UV pulse laser easily becomes larger than the energy (for example, thermal energy) necessary for processing the copper foil 11, the copper foil 11 can be easily processed.

  Alternatively, suppose that in the step shown in FIG. 1C, the same location 11e in the copper foil 11 is irradiated a plurality of times with a UV pulse laser generated at an oscillation frequency of 15 kHz or less. In this case, for example, if the processing conditions belong to the region PR1, the portion 13e exposed by the hole 11a in the resin layer 13 is removed, and then the portion 12e to be exposed by the hole 13a in the copper foil 12 is further removed. There is a possibility that. Thereby, it becomes difficult to form a blind hole in which the hole bottom is closed with the copper foil 12.

  On the other hand, in the first embodiment, in the step shown in FIG. 1C, a UV pulse laser generated at an oscillation frequency higher than 15 kHz is irradiated to the same portion 11e in the copper foil 11 a plurality of times. Thereby, the hole 13a corresponding to the hole 11a and penetrating the resin layer 13 can be stably formed so that the portion 12e to be exposed by the hole 13a in the copper foil 12 remains. That is, it becomes easy to form the blind hole BH1 in which the hole bottom is closed with the copper foil 12.

Alternatively, suppose that a UV pulse laser generated at an energy density of 0.05 J / mm ² or more is irradiated to the same location 11e in the copper foil 11 a plurality of times in the step shown in FIG. In this case, for example, if the processing conditions belong to the region PR1, the portion 13e exposed by the hole 11a in the resin layer 13 is removed, and then the portion 12e to be exposed by the hole 13a in the copper foil 12 is further removed. There is a possibility that. Thereby, it becomes difficult to form a blind hole in which the hole bottom is closed with the copper foil 12.

On the other hand, in the first embodiment, in the step shown in FIG. 1C, a UV pulse laser generated at an energy density smaller than 0.05 J / mm ² is irradiated to the same portion 11e in the copper foil 11 a plurality of times. . Thereby, the hole 13a corresponding to the hole 11a and penetrating the resin layer 13 can be stably formed so that the portion 12e to be exposed by the hole 13a in the copper foil 12 remains. That is, it becomes easy to form the blind hole BH1 in which the hole bottom is closed with the copper foil 12.

In the step shown in FIG. 1B, 4 ≦ F ≦ 15 in the FE plane (see FIG. 3).
A UV pulse laser may be generated by an oscillator (not shown) so as to satisfy the above. A region satisfying Equations 5 and 2 is a region PR2 surrounded by a two-dot chain line shown in FIG. As shown in FIG. 3, the region PR2 includes the processing conditions indicated by ◯ without including the processing conditions indicated by x and the processing conditions indicated by triangles. Thereby, since the dispersion | variation in the diameter of the processed hole in copper foil can be stored in less than predetermined value, the processing quality in a drilling process can be improved further.

  Moreover, it replaces with the to-be-processed object 10, and the to-be-processed object 20 shown in FIG.2 (b) may be processed. The workpiece 20 is a printed wiring board having a multilayer structure in which copper foils and resin layers are alternately laminated a plurality of times. For example, the copper foil 27, the resin layer 26, the copper foil 25, the resin layer 24, and copper A foil (second conductor layer) 12, a resin layer (insulating layer) 13, and a copper foil (first conductor layer) 11 are laminated in this order.

Embodiment 2. FIG.
Next, the laser processing method concerning Embodiment 2 is demonstrated using FIG. 7A to 7D are process cross-sectional views illustrating the laser processing method according to the second embodiment. Below, it demonstrates focusing on a different point from Embodiment 1. FIG.

  In the step shown in FIG. 7A and the step shown in FIG. 7B, the same processing as the step shown in FIG. 1A and the step shown in FIG.

  In the step shown in FIG. 7C, the processing conditions that satisfy Formulas 1 and 2 are used instead of the processing conditions that satisfy Formulas 3 and 4. That is, a UV pulse laser is generated by an oscillator (not shown) so as to satisfy Equations 1 and 2 on the FE plane (see FIG. 3). A region satisfying Equations 1 and 2 is a region PR1 surrounded by a one-dot chain line shown in FIGS. The region PR1 corresponds to the processing conditions for removing the copper foil 12 as shown in FIG. 3, and corresponds to the processing conditions for removing the resin layer 13 as shown in FIG. That is, the region PR1 corresponds to a processing condition in which the resin layer 13 can be removed and the copper foil 12 can be removed.

  The UV pulse laser emitted from the oscillator is irradiated to the portion 13e exposed through the hole 11a in the resin layer 13 a plurality of times (for example, five times). That is, the five pulsed UV pulse lasers L311 to L315 emitted from the oscillator are sequentially irradiated onto the portion 13e exposed through the hole 11a in the resin layer 13. Thereby, as shown in FIG. 7 (d), a hole (second hole) 13a is formed, and a portion 12e to be exposed by the hole 13a in the copper foil 12 is removed to form the hole 12a. . The hole 13a corresponds to the hole 11a and is a hole that penetrates the resin layer 13i. The hole 12a corresponds to the hole 11a and the hole 13a and is a hole that penetrates the copper foil 12i.

  In this way, as shown in FIG. 7 (d), a through hole TH300 that includes the hole 11a, the hole 13a, and the hole 12a and penetrates the workpiece 10 (printed wiring board) is formed.

  As described above, also in the second embodiment, in the step shown in FIG. 7B, the UV pulse laser generated at the oscillation frequency of 3 kHz or more and 15 kHz or less is irradiated to the same portion 11e in the copper foil 11 a plurality of times. Thereby, since the punching process which forms the hole 11a which penetrates the copper foil 11 can be performed stably (refer FIG. 3), it corresponds to the hole 11a in the process shown in FIG.7 (c), and the resin layer It is also easy to stably form the hole 13a penetrating 13 and the hole 12a corresponding to the hole 13a and penetrating the copper foil 12. That is, when drilling the workpiece 10 (that is, processing the through hole TH300 including the hole 11a, the hole 13a, and the hole 12a), stable drilling can be performed.

  As described above, the laser processing method according to the present invention is suitable for punching a conductor layer on the surface of a printed wiring board.

DESCRIPTION OF SYMBOLS 10 Workpiece 11, 11i Copper foil 11a Hole 12, 12i Copper foil 13, 13i Resin layer 13a Hole 20 Workpiece 24 Resin layer 25 Copper foil 26 Resin layer 27 Copper foil 110 Workpiece 111, 111i Copper foil 111a Hole 112 Copper foil 113, 113i Resin layer 113a Hole 210 Work piece 211, 211i Copper foil 211a Hole 212 Copper foil 213, 213i Resin layer 213a Hole 910 Work piece 911, 911i Copper foil 911a Hole 912 Copper foil 913 Resin layer BH1 Stop Hole BH100 Blind hole BH200 Blind hole L1 to L15 UV pulse laser L101 to L120 UV pulse laser L201 to L225 UV pulse laser L311 to L315 UV pulse laser L901 to L915 UV pulse laser PR1 area PR2 area PR3 Pass TH300 through hole

Claims (5)

A laser processing method for performing drilling with a pulse laser in a workpiece in which an insulating layer is sandwiched between a first conductor layer and a second conductor layer,
A first step of forming a first hole penetrating the first conductor layer by irradiating the same portion of the first conductor layer with a pulse laser a plurality of times;
A portion of the insulating layer exposed by the first hole is irradiated with a pulse laser a plurality of times to form a second hole corresponding to the first hole and penetrating the insulating layer. Process,
With
In the first step, the laser processing method is characterized in that a pulse laser generated at an oscillation frequency of 4 kHz or more and 15 kHz or less is irradiated to the same portion a plurality of times. ^2. The laser processing method according to claim 1, wherein in the first step, the same spot is irradiated a plurality of times with a pulse laser generated at an energy density of 0.05 J / mm ² or more.   In the first step, 0.05 J / mm ² 0.30 J / mm or more ² Irradiate the same location multiple times with a pulsed laser generated at the following energy density
The laser processing method according to claim 1. In the second step, a pulse laser generated at an oscillation frequency greater than 15 kHz is exposed through the first hole so that a portion to be exposed through the second hole in the second conductor layer remains. The laser processing method according to claim 1, wherein the irradiated portion is irradiated a plurality of times. In the second step, a pulse laser generated at an energy density of less than 0.05 J / mm ² is used so that a portion to be exposed by the second hole in the second conductor layer remains. The laser processing method according to claim 4, wherein the portion exposed by the hole is irradiated a plurality of times.

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