JP2012045567A - Laser beam machining method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining method and device surely machining an organic substance layer and an adhesive layer.SOLUTION: The laser beam machining method includes: the step of irradiating a flexible printed circuit board 300 in which the organic substance layer and a conductor layer are joined with the adhesive layer with a first pulse laser beam for removing the organic substance layer; and the step of irradiating a workpiece with a second pulse laser beam for removing the adhesive layer after removing the organic substance.

Description

  The present invention relates to a laser processing method and apparatus, and more particularly to a laser processing method and apparatus for processing an organic layer.

  Conventionally, a laser processing method and apparatus are disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-73760 (Patent Document 1).

JP 2008-73760 A

  In patent document 1, when the deposit | attachment which should be removed contains carbon, it aims at providing the deposit | attachment removal method which can remove a deposit | attachment cleanly from the workpiece surface. In order to achieve this object, the laser light output from the laser light source is reflected by the mirror, then condensed by the lens, and applied to the deposit.

  However, the conventional method of Patent Document 1 has a problem that organic substances cannot be removed sufficiently.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a laser processing method and apparatus capable of reliably removing organic substances.

  The laser processing method according to the present invention includes a step of irradiating a workpiece, in which an organic material layer and a conductor layer are bonded by an adhesive layer, with a first pulse laser for removing the organic material layer, and after removing the organic material. Irradiating the workpiece with a second pulse laser for removing the adhesive layer.

  In the laser processing method configured as described above, the first pulse laser suitable for removing the organic material layer and the second pulse laser suitable for removing the adhesive layer are irradiated, so that only the organic material layer is irradiated. The adhesive layer can be removed without fail.

Preferably, the first pulse laser is a carbon dioxide laser, and the second pulse laser is either a fiber laser, a YAG laser, or a YVO ₄ laser.

  Preferably, the second pulse laser is a laser wavelength-converted to a short wavelength by a nonlinear crystal.

  Preferably, the organic layer includes at least one selected from the group consisting of polyimide, polyethylene terephthalate, and liquid crystal polymer.

  The laser processing method according to any one of claims 1 to 4, wherein the workpiece is preferably a flexible printed circuit board or a flat cable.

  Preferably, the workpiece is drawn out from the roll shape and processed, and is wound in the roll shape after the processing.

Preferably, oxygen is supplied to the processing portion during processing with the first or second pulse laser.
A laser processing apparatus according to the present invention is a laser processing apparatus for performing the laser processing method described above, and removes an organic layer from a workpiece in which an organic layer and a conductor layer are bonded by an adhesive layer. And a laser source capable of irradiating the workpiece with a second pulse laser for removing the adhesive layer after removing the organic matter.

  The present invention can provide a laser processing method and apparatus capable of reliably removing the organic material layer and the adhesive layer.

It is a schematic diagram of the laser processing apparatus according to Embodiment 1 of this invention. It is sectional drawing of the flexible printed circuit board processed with the laser processing method according to Embodiment 1 of this invention. It is sectional drawing for demonstrating the process of removing organic substance in the laser processing method according to Embodiment 1 of this invention. It is sectional drawing for demonstrating the test | inspection process of a hole in the laser processing method according to Embodiment 1 of this invention. It is a graph which shows the relationship between the transmittance | permeability (vertical axis) and the wavelength (horizontal axis) in the visible and ultraviolet region of polyimide. It is a graph which shows the relationship between the absorption factor (vertical axis) and the wavelength (horizontal axis) in the visible and ultraviolet region of polyimide. It is a graph which shows the relationship between the absorption (vertical axis) and wave number (horizontal axis) in the infrared region of polyimide. Graph showing the relationship between transmittance (vertical axis) and wavelength (horizontal axis) in the visible and ultraviolet regions of PET (polyethylene terephthalate) and liquid crystal polymer used as an organic material layer in the processing method according to Embodiment 2 of the present invention It is. It is sectional drawing of the flat cable using PET resin as an organic substance layer. It is sectional drawing which shows the process of a flat cable using PET resin as an organic substance layer. 1 is a plan view of a hole formed according to the present invention. FIG. It is a graph which shows the relationship between absorption (vertical axis) and wave number (horizontal axis) in the infrared region of PET. It is a graph which shows the relationship between absorption (vertical axis) and wave number (horizontal axis) in the infrared region of a liquid crystal polymer.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In addition, the embodiments can be combined.

(Embodiment 1)
FIG. 1 is a schematic diagram of a laser processing apparatus having a processing section and a measurement section according to Embodiment 1 of the present invention. Referring to FIG. 1, laser processing apparatus 1 according to the first embodiment of the present invention includes a processing unit 100 that processes a resin, and a measurement unit 200 that measures the resin processed by processing unit 100. The processing unit 100 converges the processing laser source 110 that is a carbon dioxide laser source, the galvano scanner 120 for changing the direction of the laser beam 111 emitted from the processing laser source 110, and the laser beam reflected by the galvano scanner 120. And an Fθ lens 130 to be operated. The laser beam 112 collected by the Fθ lens 130 is irradiated on the surface of the flexible printed circuit board 300. The region irradiated with the laser beam 112 is a processing area 310, and the organic layer on the flexible printed board is removed.

  The processing laser source 110 can irradiate a plurality of types of pulse lasers. The plurality of lasers have an optimum wavelength for removing the organic material layer and the adhesive layer on the flexible printed circuit board.

  A measurement area 320 is provided adjacent to the processing area 310. In the measurement area 320, it is measured whether or not the part processed in the processing area 310 is processed correctly.

  In the processing area 310, it is possible to supply a gas for promoting processing to a processing location.

  The measurement unit 200 includes a residue measurement laser source 210. The laser light 211 emitted from the residue measurement laser source 210 is reflected by the galvano scanner 220 and the laser light passes through the condenser lens 230. The laser light transmitted through the condenser lens 230 is reflected by the surface of the flexible printed board 300 in the measurement area 320 and detected by the light receiving unit 240. The light receiving unit 240 can image the processing state in the processing area 310 by measuring the laser beam 213. Note that the measurement unit 200 is not necessarily provided.

  The processing laser source 110, the galvano scanners 120 and 220, the residue measurement laser source 210, and the light receiving unit 240 are connected to the control unit 400, respectively. The measured data or the intensity of the irradiated laser is sent by the control unit 400. In the control unit 400, the computer can determine whether or not the processing is appropriately performed based on the obtained data.

  FIG. 2 is a cross-sectional view of the flexible printed circuit board processed by the laser processing method according to Embodiment 1 of the present invention. With reference to FIG. 2, an opening 31 is formed in a laminated structure of conductive layer 10, organic layer 20, and conductive layer 30. The diameter of the opening 31 is D. The conductive layer 10 may be any conductive layer. For example, it may be a metal such as copper or aluminum, or may be a semiconductor such as silicon into which impurities are introduced.

  The organic layer 20 can employ various organic materials such as polyethylene terephthalate (PET), polyimide (PI), and liquid crystal polymer (LCP). The organic layer 20 is connected to the conductive layer 10 by the adhesive layer 20a.

  FIG. 3 is a cross-sectional view for explaining a step of removing organic substances in the laser processing method according to the first embodiment of the present invention. Referring to FIG. 3, holes 22 are formed in organic layer 20 by laser light 112. At this time, the laser beam 112 is irradiated with the laser beam 112 so as to expose the conductive layer 10.

The laser beam 112 is irradiated in two stages. First, the first pulse laser for removing the organic layer 20 is irradiated. This laser is a long-wavelength laser such as a carbon dioxide laser, and the organic layer can be efficiently removed. At this time, it cannot be said that the carbon dioxide laser has characteristics suitable for removing the adhesive layer 20a. As a result, after the carbon dioxide laser irradiation, the second pulse laser for removing the adhesive layer 20a is irradiated. The laser for removing the adhesive layer is either a fiber laser, a YAG laser, or a YVO ₄ laser. That is, the adhesive layer 20a tends to remain only with a single pulse laser. On the other hand, when processing with a single pulse laser having high absorption in both the organic material layer 20 and the adhesive layer 20a, a laser having a wavelength having absorption in the thin adhesive layer 20a is selected. It takes time to process 20. Therefore, efficient processing can be performed by processing the thick organic layer 20 and the thin adhesive layer 20a with pulse lasers of different wavelengths.

In general, the absorption of the organic layer 20 typified by resin is often high in a carbon dioxide laser. However, since the wavelength is long, the thin adhesive layer 20a often remains. Therefore, by removing the adhesive layer 20a by irradiation with a fiber laser having a wavelength of 1/10, YAG laser, or YVO ₄ laser, there is no resin residue and processing can be performed efficiently.

The fiber laser, YAG laser, or YVO ₄ laser is a laser having a short wavelength using a nonlinear crystal, so that the absorptance is further increased and the adhesive layer 20a can be efficiently irradiated and removed.

And as the organic substance layer 20, a polyimide resin, PET, or a liquid crystal polymer is used. When the organic layer 20 and the adhesive layer 20a are removed by pulse laser, it is preferable to use an oxygen assist gas. In this case, not only the removal effect (ablation) of the laser alone but also a chemical change of C + O ₂ → CO ₂ occurs, and the organic layer 20 and the adhesive layer 20a can be processed efficiently.

  FIG. 4 is a cross-sectional view for explaining the hole inspection step in the laser processing method according to the first embodiment of the present invention. Referring to FIG. 4, a laser beam 211 is irradiated from a residue measurement laser source 210. And the light-receiving part 240 detects the electromagnetic waves reflected from the bottom 22a of the hole 22. Based on the detection amount at this time, it is possible to detect how much the organic layer 20 remains on the bottom 22a. And the map of the residual amount of the organic substance layer 20 is created in the whole bottom 22a.

  FIG. 5 is a graph showing the relationship between transmittance (vertical axis) and wavelength (horizontal axis) in the visible and ultraviolet regions of polyimide. FIG. 6 is a graph showing the relationship between the absorption rate (vertical axis) and wavelength (horizontal axis) of visible and ultraviolet regions of polyimide. With reference to FIG. 5 and FIG. 6, the absorptance is related to the transmittance, and the equation of absorption rate = 1−transmittance is established.

  FIG. 7 is a graph showing the relationship between absorption (vertical axis) and wave number (horizontal axis) in the infrared region of polyimide. Referring to FIG. 7, it can be seen that absorption is increased at a specific wave number in any material constituting organic layer 20. This is an absorption caused by a chemical bond constituting the organic layer 20.

  That is, the laser processing method includes a step of preparing a flexible printed circuit board 300 as a workpiece including the organic material layer 20 and a step of processing the organic material layer 20 by irradiating the laser beam 112.

(Embodiment 2)
FIG. 8 shows the transmittance (vertical axis) and wavelength (horizontal axis) in the visible and ultraviolet regions of PET (polyethylene terephthalate) and liquid crystal polymer used as the organic material layer in the processing method according to the second embodiment of the present invention. It is a graph which shows a relationship.

  Referring to FIG. 8, the absorbance of PET and liquid crystal polymer increases in the range of about 200 to 450 nm. Therefore, if a laser having this wavelength is used as a laser source for processing, the absorption by the PET and the liquid crystal polymer constituting the organic material layer is increased and can be reliably removed. In addition, absorption in the ultraviolet and visible regions is not absorption based on a specific chemical bond constituting an organic substance, like absorption in the infrared region. Therefore, the sharp peak seen in infrared absorption is not found in the ultraviolet and visible regions.

In the following, the absorbance of each resin will be described.
In PET, an absorbance peak exists at a wave number of 1712 cm ⁻¹ . This peak is derived from the C═O bond of the ester. The wavelength of this peak is 5.84 μm. As a laser having such a wavelength, there is a Hamamatsu Photonics quantum cascade laser (wavelength 5.8 μm).

PET also has an absorbance peak at a wave number of 1240 cm ⁻¹ . This peak is derived from the C—O bond of the carbonyl group. The wavelength of this peak is 8.06 μm, and there is a semiconductor laser (PbS _1-x Se _x (wavelength 4-8.5 μm)) as a laser with such a wavelength.

PET also has an absorbance peak at a wave number of 1100 cm ⁻¹ . This peak is derived from the C—O bond of the carbonyl group. The wavelength of this peak is 9.09 μm, and there is a semiconductor laser (Pb _1-x Sn _x Te (wavelength 6.3-32 μm)) as a laser with such a wavelength.

  PET also has an absorbance peak at a wavelength of 300 nm in the visible region. As a laser having such a wavelength, there is a XeCl excimer laser (wavelength: 0.308 μm).

PI has an absorbance peak at a wave number of 1775 cm ⁻¹ in the infrared region. This peak is derived from the imide C═O bond. The wavelength of this peak is 5.63 μm, and there is a DBr chemical laser (wavelength 5.8-6.3 μm) as a laser with such a wavelength.

PI has an absorbance peak with a wave number of 1712 cm ⁻¹ . This peak is derived from the imide C═O bond. The wavelength of this peak is 5.84 μm, and there is a DBr chemical laser (wavelength 5.8-6.3 μm) as a laser with such a wavelength.

Polyimide has an absorbance peak at a wave number of 1400 cm ⁻¹ . This peak is derived from the methylene of the benzene rings on both sides. The wavelength of this peak is 7.14 μm, and there is a semiconductor laser (PbS _1-x Se _x (wavelength 4-8.5 μm)) as a laser with such a wavelength.

  In addition, polyimide has a peak of absorbance at a wavelength of 450 nm in the visible region, and an Ar ion laser (wavelength: 0.45 μm) exists as a laser having such a wavelength.

LCP has an absorbance peak with a wave number of 1730 cm ^{−1 in} the infrared region. This peak is derived from the C═O bond of the ester. The wavelength of this peak is 5.78 μm. As a laser having such a wavelength, a quantum cascade laser (wavelength 5.8 μm) or a semiconductor laser (PbS _1-x Se _x (wavelength 4-8.5 μm)) manufactured by Hamamatsu Photonics Co., Ltd. Exists.

LCP also has an absorbance peak with a wave number of 1300-1150 cm ⁻¹ . This peak is derived from the ester C—O bond. The wavelength of this peak is 7.69-8.70 μm, and there is a semiconductor laser (PbS _1-x Se _x (wavelength 4-8.5 μm)) as a laser with such a wavelength.

LPC has an absorbance peak with a wave number of 1650-1400 cm ⁻¹ . This peak is derived from the C = C bond of the benzene ring. The wavelength of this peak is 6.06-1.74 μm. As a laser having such a wavelength, there are a DBr chemical laser (wavelength 5.8-6.3 μm) and a semiconductor laser (PbS _1-x Se _x (wavelength 4-8.5 μm)).

  LPC has an absorbance peak at a wavelength of 400 nm, and there are a semiconductor laser (wavelength: 0.41 μm) and a Pb vapor laser (wavelength: 0.41 μm) as lasers having such a wavelength.

  By using these lasers for processing, absorption by the organic layer 20 can be enhanced.

(Embodiment 3)
FIG. 9 is a cross-sectional view of a flat cable using PET resin as the organic layer. FIG. 10 is a cross-sectional view showing a flat cable processing step using PET resin as the organic layer. FIG. 11 is a plan view of a hole formed in accordance with the present invention.
9 to 11, even a flat cable in which a conductive layer 29 is embedded in an organic material layer 20 is a processing target of the processing method and processing apparatus according to the present invention. Specifically, in the step of manufacturing the hole 22 in FIG. 10, the organic layer 20 and the adhesive layer 20a can be reliably removed by using the method and apparatus shown in FIG.

  As shown in FIG. 11, the conductive layer 29 is not exposed at the bottom of the hole 22 in the first region 1100 irradiated with only the carbon dioxide laser. This is presumably because the adhesive layer remains on the bottom of the hole 22. On the other hand, the conductive layer 29 is exposed on the bottom surface of the hole 22 in the portion irradiated with the fiber laser after being irradiated with the carbon dioxide laser. This is presumably because the adhesive layer was reliably removed by the fiber laser.

  FIG. 12 is a graph showing the relationship between absorption (vertical axis) and wave number (horizontal axis) in the infrared region of PET. FIG. 13 is a graph showing the relationship between absorption (vertical axis) and wave number (horizontal axis) in the infrared region of a liquid crystal polymer. Referring to FIGS. 12 and 13, it can be seen that the absorption is increased at a specific wave number. This is absorption by a specific chemical bond (functional group) constituting the organic substance. If such absorption exists, it is understood that the organic substance having the functional group remains. By irradiating a laser having a wave number with large absorption, the energy of the laser can be efficiently absorbed by the resin.

  As shown in FIG. 2, a copper plate (thickness: 18 μm), an adhesive layer 20a (thickness: 2-3 μm) made of a polyimide resin, a polyimide resin (thickness: 20 μm) constituting the organic layer 20, and an adhesive made of a polyimide resin. A flexible printed circuit board having a layer structure of a layer 20a (thickness: 2-3 μm) and a copper plate (thickness: 18 μm) was prepared.

  In this flexible printed circuit board, an opening 31 is formed in advance on one copper plate by photolithography and copper etching as shown in FIG.

  The flexible printed circuit board is drawn out from the rolled state and processed, and then stored in the rolled state.

Then, the organic layer 20 is removed by processing with a carbon dioxide gas laser, and then the adhesive layer 20a is removed with a pulse laser of a fiber laser, YAG laser, or YVO ₄ laser. This processed the flexible printed circuit board of the blind via structure from which the polyimide resin was removed. Here, the carbon dioxide laser has an output of 100 W and a pulse of about μ seconds. The carbon dioxide laser is controlled so that the galvano scanner 120 shown in FIG. The output of the fiber laser, YAG laser, or YVO ₄ laser after the carbon dioxide laser irradiation was 16 W. Oxygen is introduced at a flow rate of 10 dm ³ / min into the carbon dioxide laser irradiation area and the fiber laser, YAG laser, or YVO ₄ laser irradiation area. This makes it possible to reliably remove the resin residue.

PET resin (thickness 20 μm), PET resin adhesive layer (thickness 2-3 μm), copper wiring (thickness 18 μm), PET resin adhesive layer (thickness 2-3 μm), PET resin (thickness 20 μm) A flat cable (FIG. 9) having a layer structure was prepared. The PET resin and the PET resin adhesive layer on one side were removed by carbon dioxide laser irradiation and a pulse laser of a fiber laser, YAG laser, or YVO ₄ laser. (FIG. 10). Here, the carbon dioxide laser had an output of 100 W and a pulse of about 12 μs. The output of the fiber laser, YAG laser, or YVO ₄ laser pulse laser is processed by a carbon dioxide laser by linear scanning with the galvano scanner 120 shown in FIG. The YAG laser or YVO ₄ laser had an output of 16 W. Oxygen is introduced at a flow rate of 10 dm ³ / min into the carbon dioxide laser irradiation area and the fiber laser, YAG laser, or YVO ₄ laser irradiation area. This makes it possible to reliably remove the resin residue.

  The present invention can be used in the field of a laser processing apparatus capable of processing an organic material layer.

  DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 10,30 Conductive layer, 20 Organic substance layer, 21 Residue, 22 Hole, 22a Bottom, 31 Opening, 100 Process part, 110 Processing laser source, 111, 112, 211, 213 Laser beam, 120, 220 Galvano scanner, 130 lens, 200 measuring unit, 210 residue measuring laser source, 230 condensing lens, 240 light receiving unit, 300 flexible printed circuit board, 310 processing area, 320 measuring area, 400 control unit.

Claims (8)

Irradiating a workpiece in which an organic material layer and a conductor layer are bonded together by an adhesive layer with a first pulse laser for removing the organic material layer;
And a step of irradiating the workpiece with a second pulse laser for removing the adhesive layer after removing the organic matter. 2. The laser processing method according to claim 1, wherein the first pulse laser is a carbon dioxide laser, and the second pulse laser is any one of a fiber laser, a YAG laser, and a YVO ₄ laser.   The laser processing method according to claim 2, wherein the second pulse laser is a laser wavelength-converted to a short wavelength by a nonlinear crystal.   The laser processing method according to any one of claims 1 to 3, wherein the organic layer includes at least one selected from the group consisting of polyimide, polyethylene terephthalate, and liquid crystal polymer.   The laser processing method according to claim 1, wherein the workpiece is any one of a flexible printed circuit board and a flat cable.   6. The laser processing method according to claim 1, wherein the workpiece is drawn out of a roll shape and processed, and is wound in a roll shape after the processing.   The laser processing method according to any one of claims 1 to 6, wherein oxygen is supplied to a processing portion during processing by the first or second pulse laser. A laser apparatus for carrying out the laser processing method according to any one of claims 1 to 7,
In order to remove the adhesive layer on the workpiece after removing the organic substance, a first pulse laser for removing the organic substance layer on the workpiece in which the organic substance layer and the conductor layer are bonded by the adhesive layer And a laser source capable of irradiating the second pulse laser.