JP4017899B2 - Laser processing method and laser processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing method and a laser processing apparatus for irradiating a processing target having a coating layer with a laser beam to make a hole in the coating layer.
[0002]
[Prior art]
A method is known in which a pulse laser beam in the ultraviolet wavelength region is focused on a coating layer formed on a base member to make a hole. If the pulse energy of the laser beam is set to such a size that the covering layer is ablated and the underlying member is not ablated, a through-hole can be formed in the covering layer with little damage to the underlying member.
[0003]
[Problems to be solved by the invention]
However, if a hole with a large area is to be drilled by ablation processing, a pulse laser beam of about 100 shots is required even if a hole with a diameter of about 50 μm is formed in a resin coating layer with a thickness of 50 μm, which requires a long time for processing. It was.
[0004]
An object of the present invention is to provide a laser processing method and a laser processing apparatus capable of effectively drilling holes in a coating layer of a processing object in a short time.
[0005]
[Means for Solving the Problems]
According to one aspect of the present invention, a base member having a surface layer portion made of a first material, and a coating formed on a part of the surface of the base member with a second material different from the first material A step of preparing an object to be processed including a layer and an adhesive layer in close contact with at least a part of the surface of the coating layer; and transmitting through the adhesive layer and the coating layer and reflecting on the surface of the base member; A step of causing a laser beam having a property of peeling the coating layer from the base member to enter the object to be processed from the surface of the adhesive layer and peeling a part of the coating layer from the base member; and There is provided a laser processing method including a step of removing a peeled portion of the coating layer separated from the coating layer and peeled off from the base member from the workpiece together with the adhesive layer.
[0006]
According to the laser processing method, it is possible to make a large-area hole in a short time while preventing scattering of the peeled portion of the coating layer peeled from the base member.
Further, according to the laser processing method, the coating layer peeled off from the base member can be efficiently removed.
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1A is a schematic diagram of a laser processing apparatus used in the laser processing method according to the first embodiment of the present invention. The laser light source 1 emits a pulse laser beam. A workpiece 4 is held on the movable surface of the XY stage 3. The emitted pulsed laser beam is converged by the plano-convex lens 2 and is incident on the surface of the workpiece 4 held on the XY stage 3.
[0008]
The laser light source 1 includes an Nd: YLF laser oscillator and a nonlinear optical element, and can generate a fundamental wave (wavelength 1047 nm) or a second harmonic (wavelength 523 nm). Here, the fundamental wave is emitted with a pulse width of 15 ns and a pulse energy of 180 μJ.
[0009]
As shown in FIG. 1B, the cross-sectional shape of the beam may be shaped with a mask 5. Alternatively, the movable surface of the XY stage 3 may be arranged horizontally, and the laser beam may be reflected vertically downward by the reflection mirror 6. Further, processing can be performed in the chamber 7. When the chamber 7 is used, processing in a vacuum or under pressure can be performed.
[0010]
FIG. 2A is a cross-sectional view of a multilayer printed circuit board processed by the laser processing method according to the first embodiment of the present invention.
Support material (reinforcing material), for example, a support substrate 13 made of an epoxy resin reinforced with glass fiber, a metal layer 12 which is a base member made of a metal material, for example, copper, a dielectric material, for example, a resin made of an epoxy resin The covering layer 11 is laminated from the bottom in this order. An adhesive layer 10 formed by being in close contact with the surface of the resin coating layer 11 and applying, for example, a vinyl acetate resin-based water-soluble adhesive is laminated. The thickness of the resin coating layer 11 is, for example, 50 μm.
[0011]
Examples of the dielectric material of the resin coating layer 11 include epoxy resin, polyimide resin, phenol resin, PTFE (polytetrafluoroethylene), BT resin (trademark) , BCB (benzocyclobutene), and the like.
[0012]
Examples of the metal material of the metal layer 12 include copper, aluminum, gold, silver, palladium, nickel, titanium, tungsten, platinum, and molybdenum.
The support substrate 13 is formed of a dielectric material reinforced with a support material (reinforcing material) such as glass fiber, alumina fiber, aramid fiber, Kepler or the like.
[0013]
The adhesive layer 10 includes a water-soluble adhesive based on vinyl acetate resin, a water-soluble adhesive based on latex, a transparent adhesive based on an epoxy resin, a transparent adhesive based on an acrylic resin, a transparent adhesive based on a polyester resin, and the like. It can be obtained by applying or sticking an adhesive tape such as a cellophane tape on the surface of the resin coating layer 11.
[0014]
A fundamental wave of an Nd: YLF laser is incident from the upper surface of the adhesive layer 10. The beam is transmitted through the adhesive layer 10 and the resin coating layer 11 with almost no absorption, and has a property of being mostly reflected by the surface of the metal layer 12. The laser beam causes a high pressure state at the interface between the resin coating layer 11 and the metal layer 12, and the pressure induces peeling of the resin coating layer 11 from the metal layer 12. This phenomenon is called a “lifting phenomenon”, and a process performed using the “lifting phenomenon” is called a “lifting process”. One of the differences from the conventional ablation process is that the peeled resin coating layer 11 remains as a small lump.
[0015]
When the adhesive layer 10 does not exist, the peeled small blob of the resin coating layer 11 jumps out into the air. The speed of the fastest thing reaches 300m / s.
The adhesive layer 10 suppresses scattering of a small lump. That is, the resin coating layer 11 at the position where the beam is reflected is peeled off from the metal layer 12, but the peeled blob is covered with the adhesive layer 10, so that it is prevented from jumping into the air.
[0016]
FIG. 2B is a cross-sectional view of the multilayer printed circuit board after one shot of the pulsed laser beam is irradiated onto the multilayer printed circuit board of FIG. The resin coating layer 11 has a crack 14. The crack 14 occurs along a virtual closed curve defined on the interface between the resin coating layer 11 and the metal layer 12, extends in the thickness direction of the resin coating layer 11, and is formed on the upper surface of the resin coating layer 11. A defined virtual closed curve is reached. The peeled portion 11a in the vicinity of the incident point of the laser beam in the resin coating layer 11 is peeled off from the metal layer 12, but is covered with the adhesive layer 10 and remains in the substrate.
[0017]
Subsequently, the adhesive layer 10 is mechanically peeled off, for example. At this time, the peeled portion 11 a of the resin coating layer 11 peeled from the metal layer 12 and bonded to the adhesive layer 10 is also separated from the multilayer printed board together with the adhesive layer 10. Thus, holes can be formed in the resin coating layer 11. For example, when the bottom shape is circular, the diameter of the hole is 100 μm or more. Lifting processing enables drilling large areas with fewer shots than ablation processing. Processing time is also shortened.
[0018]
By using the multilayer printed board on which the adhesive layer 10 is formed, scattering of the peeling portion 11a of the resin coating layer 11 can be suppressed. Thereby, damage to the optical system for condensing the laser beam can be prevented. In addition, when processing is performed in a vacuum or under pressure using the chamber, it is possible to prevent problems (for example, adverse effects on processing quality) caused by the scattered peeled portion 11a accumulating in the chamber. Moreover, when the scattered peeling portion 11a accumulates in the chamber, it is necessary to open the chamber and remove the peeling portion 11a, but the removal work can be omitted. Furthermore, the peeling part of the resin coating layer 11 can also be effectively separated from the multilayer printed board. This will be described below.
[0019]
FIG. 2C is a cross-sectional view of the multilayer printed board after one shot of the pulsed laser beam is applied to the multilayer printed board of FIG. The crack 14 is generated along a virtual closed curve defined on the interface between the resin coating layer 11 and the metal layer 12 and extends in the thickness direction of the resin coating layer 11, but reaches the upper surface thereof. Not done. In addition, the resin coating layer 11 is peeled from the metal layer 12 inside the virtual closed curve. For this reason, the non-separation peeling part 11b is formed inside the crack 14. The non-separated peeling portion 11b remains on the metal layer 12 without being separated from the multilayer printed board.
[0020]
The adhesive layer 10 is peeled off from the resin coating layer 11. The crack 14 extends to the upper surface of the resin coating layer 11 due to the peeling force, and the non-separation peeling portion 11b is separated from the multilayer printed board together with the adhesive layer 10. As a result, the same hole as that shown in FIG. In addition, it is preferable that the crack 14 generated after the pulse laser beam irradiation reaches the very upper surface of the resin coating layer 11.
[0021]
Further, when the adhesive layer 10 is peeled off, not only the non-separated peeled portion 11b but also dust on the surface of the resin coating layer 11 and scattered matters attached around the formed hole can be removed.
[0022]
Furthermore, since the peeled part of the resin coating layer 11 peeled from the metal layer 12 can be collected, it is also an excellent method when using the peeled part.
In addition, after peeling off the contact bonding layer 10, the resin coating layer 11 in which the hole was formed is hardened, and using as a type | mold is also considered.
[0023]
Next, a second embodiment of the present invention will be described with reference to FIGS. 3 (A), 3 (B) and FIG.
FIG. 3A shows a schematic diagram of a laser processing apparatus used in the laser processing method according to the second embodiment. The laser light source 20 emits a pulse laser beam. A workpiece 26 is held on the movable surface of the XY stage 25. The emitted pulsed laser beam passes through a mask 21 that shapes the cross-sectional shape of the beam, is converged by a plano-convex lens 22, is reflected by a reflection mirror 23, and is incident on the surface of a workpiece 26.
[0024]
The laser light source 20 is the same as that shown in FIG. Here, the fundamental wave of the Nd: YLF laser is emitted with a pulse width of 15 ns and a pulse energy of 180 μJ.
[0025]
FIG. 4 is a sectional view of a multilayer printed circuit board processed by the laser processing method according to the second embodiment. The difference from the one shown in FIG. 2A is that the adhesive layer 10 is not formed.
[0026]
First, for example, a vinyl acetate resin-based water-soluble adhesive is sprayed on the surface of the resin coating layer 11 of the multilayer printed board shown in FIG. This is performed by a water-soluble adhesive sprayer 24 using, for example, a quantitative pump in a region different from the region where the laser beam can be incident. The multilayer printed circuit board sprayed with the vinyl acetate resin-based water-soluble adhesive is moved in the direction of the arrow 30 by the XY stage 25 and conveyed to the laser beam incident area. During this time, the vinyl acetate resin-based water-soluble adhesive is solidified, and an adhesive layer is formed on the surface of the resin coating layer 11. That is, a printed multilayer board as shown in FIG. 2A is arranged in a laser beam incident region. The formed adhesive layer transmits the fundamental wave (wavelength 1047 nm) of the Nd: YLF laser and hardly absorbs it.
[0027]
The fundamental wave (wavelength 1047 nm) of the Nd: YLF laser is incident from the upper surface of the adhesive layer formed on the surface of the resin coating layer 11. The laser beam peels off the resin coating layer 11 at the incident position from the metal layer 12 due to the lifting phenomenon, but does not jump out of the substrate because of the adhesive layer.
[0028]
Subsequently, the printed multilayer board is moved little by little by the XY stage 25, and a laser beam is irradiated to another position on the board. When the beam has been irradiated to a predetermined position, the adhesive layer is peeled off. At this time, the resin coating layer 11 peeled from the metal layer 12 is separated from the multilayer printed board.
[0029]
The laser processing apparatus shown in FIG. 3A is characterized by including an apparatus for forming an adhesive layer. The effect of forming the adhesive layer on the surface of the resin coating layer 11 is the same as that described in the first embodiment.
[0030]
FIG. 3B is a schematic diagram of a laser processing apparatus using a galvano scanner 27 instead of the reflection mirror 23 of the laser processing apparatus shown in FIG. Other configurations are the same as those of the laser processing apparatus in FIG. The galvano scanner 27 includes a pair of swingable reflecting mirrors, and scans the laser beam in a two-dimensional direction at high speed.
[0031]
By the operation of the galvano scanner 27, the incident position of the laser beam moves on the surface of the multilayer printed board, and peeling portions are formed one after another on the resin coating layer 11. However, it is blocked by the adhesive layer and does not jump out of the substrate. When the processing in the area that can be scanned by the galvano scanner 27 is completed, the multilayer printed board is moved by the XY stage 25, and the other areas are processed. By repeating the scanning by the galvano scanner 27 and the movement of the multilayer printed board by the XY stage 25, peeling portions due to the lifting phenomenon are formed on all the processed parts on the multilayer printed board. When the beam has been irradiated to a predetermined position, the adhesive layer is peeled off. At this time, the peeled portion of the resin coating layer 11 peeled from the metal layer 12 is separated from the multilayer printed board.
[0032]
In this way, the high-speed beam scanning optical system can be used to speed up the work.
In the first and second embodiments, the fundamental wave (wavelength 1047 nm) of the Nd: YLF laser was used as the laser beam irradiated onto the multilayer printed board. However, the same lifting process can be performed using a laser beam having a wavelength of 500 to 600 nm, a pulse width of 10 to 30 ns, and a pulse energy of 50 μJ / pulse or more. Even if a laser beam having a wavelength of 800 to 3000 nm is used, the same lifting process can be performed.
[0033]
As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0034]
【The invention's effect】
As described above, according to the present invention, a hole having a large area can be formed in the coating layer in a short time while preventing the peeling portion of the coating layer peeled off from the base member from scattering. Furthermore, the coating layer peeled off from the base member can be efficiently removed.
[Brief description of the drawings]
FIGS. 1A and 1B are schematic views of a laser processing apparatus used in a laser processing method according to a first embodiment of the present invention.
FIGS. 2A to 2C are cross-sectional views of a multilayer printed circuit board processed by the laser processing method according to the first embodiment.
FIGS. 3A and 3B are schematic views of a laser processing apparatus used in the laser processing method according to the second embodiment. FIGS.
FIG. 4 is a cross-sectional view of a multilayer printed circuit board processed by a laser processing method according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light source 2 Plano-convex lens 3 XY stage 4 Work object 5 Mask 6 Reflection mirror 7 Chamber 10 Adhesive layer 11 Resin coating layer 11a Peeling part 11b Non-separation peeling part 12 Metal layer 13 Support substrate 14 Crack 20 Laser light source 21 Mask 22 Flat Convex lens 23 Reflective mirror 24 Water-soluble adhesive sprayer 25 XY stage 26 Work object 27 Galvano scanner 30 Arrow

Claims (3)

A base member having a surface layer portion made of a first material; a coating layer formed of a second material different from the first material on a part of the surface of the base member; and at least a surface of the coating layer Preparing an object to be processed including an adhesive layer that is in close contact with a portion;
A laser beam transmitted through the adhesive layer and the coating layer, reflected by the surface of the base member, and peeling off the coating layer at the reflection position from the base member is incident on the workpiece from the surface of the adhesive layer. And a step of peeling a part of the coating layer from the base member;
A step of separating the adhesive layer from the coating layer and removing a peeled portion of the coating layer peeled off from the base member from the workpiece together with the adhesive layer.   The laser beam is a pulse laser beam having a wavelength of 500 to 600 nm, a pulse width of 10 to 30 ns, a pulse energy of 50 μJ / pulse or more, or a pulse laser beam having a wavelength of 800 to 3000 nm. 2. The laser processing method according to 1.   The laser processing method according to claim 1, wherein the step of preparing the object to be processed includes a step of forming the adhesive layer by applying an adhesive to the surface of the coating layer.

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