JP2004322157A - Working method for work and tacky adhesive sheet used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for subjecting works, such as, for example, various kinds of sheet materials, circuit boards, semiconductor wafers, glass substrates, ceramic substrates, metallic substrates, light emitting or light receiving element substrates for semiconductor lasers etc., MEMS substrates, semiconductor packages, cloth, leather, and paper, to working such as, for example, cutting and perforating. <P>SOLUTION: The method of working the works by using UV absorption abrasion of a laser includes (1) a process of sticking a tacky adhesive sheet of ≥50% in transmittance in an absorption region of a laser beam to a surface of the work opposite to the surface to be irradiated with the laser, (2) a process of working the work by irradiating the work with the laser, and (3) a process of peeling off the tacky adhesive sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes workpieces such as various sheet materials, circuit substrates, semiconductor wafers, glass substrates, ceramic substrates, metal substrates, light emitting or receiving element substrates such as semiconductor lasers, MEMS substrates, semiconductor packages, cloth, leather, and paper. The present invention relates to a method of processing such as cutting and drilling using a laser.
[0002]
[Prior art]
With the recent miniaturization of electrical and electronic equipment, the miniaturization of parts and high definition have progressed, and the outline processing of various materials has been required to have high precision and high accuracy with processing accuracy of ± 50 μm or less. ing. However, the conventional punching process such as press working has an accuracy of about ± 100 μm at the most, and is currently unable to meet such a requirement. Also, high-definition and high-precision are required for drilling various materials, and it has become impossible to perform drilling with conventional drills or dies.
[0003]
[Problems to be solved by the invention]
As a solution, laser processing methods have attracted attention. In particular, processing methods that use ultraviolet absorption of lasers, which have low thermal damage and are capable of high-definition processing, are precise external processing methods and fine processing methods. It is attracting attention as a drilling method. On the other hand, when a laser is used, a post-process called desmear for removing a decomposition product residue such as carbon generated during laser processing on the surface is essential.
In particular, the surface (laser emitting surface) of the workpiece that is in contact with the processing table firmly adheres to the surface of the processing table as well as the decomposition product of the processing table surface by laser irradiation. The adhesion strength of the deposit on the emission surface side becomes stronger in proportion to the power of the laser. If the laser power is increased, it will be difficult to remove the deposit in the subsequent process. There was a problem that throughput improvement was hindered or the reliability of the hole was lowered. In addition, if the entire circumference is machined all at once, the work piece will fall off after machining, which is difficult to handle and requires a method that leaves some unmachined parts during machining. It was.
[0004]
As a semiconductor wafer dicing method, a method of supporting and fixing a semiconductor wafer on a dicing sheet and dicing with a laser beam has been proposed (see Patent Document 1).
However, the laser beam used here is a YAG laser fundamental wave (wavelength 1.06 μm) or a ruby laser (694 nm) whose wavelength is in the infrared region. Therefore, the thermal damage of the edge portion is large, leading to a decrease in accuracy and reliability, and even if the light is collected, it can be collected only up to about 50 μm, so it is necessary to make a large margin. As a method for avoiding such a problem, a method using both a YAG fundamental wave and a water jet has also been proposed. According to this method, although thermal damage of the edge portion is reduced by the cooling effect of the water jet, Since the width of the cutting margin at the time of dicing is defined by the diameter of the water jet, there is a problem that there is a limit to dicing at a thin cutting margin.
[0005]
[Patent Document 1]
JP 2002-343747 A
[0006]
[Means for Solving the Problems]
The present invention has been made in view of such circumstances, and can process a workpiece with high accuracy and high speed, improve the reliability of the processed portion, and easily collect the workpiece after processing. It aims at providing the processing method which can be performed.
That is, the present invention is a method of processing a workpiece using ultraviolet absorption ablation of a laser,
(1) A step of attaching an adhesive sheet having a transmittance of 50% or more in the laser light absorption region to the surface opposite to the laser irradiation surface of the workpiece;
(2) A process of processing a workpiece by irradiating the workpiece with a laser;
(3) Step of peeling the adhesive sheet
It concerns on the processing method of the workpiece characterized by including.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The laser used in the present invention is required not to deteriorate the accuracy and appearance of the hole edge and the cut wall surface due to thermal damage during laser processing. For that purpose, it is important to use a laser that can be ablated by absorption of ultraviolet light, which is a non-thermal process that does not go through a thermal process, and that can focus and cut to a narrow width of 20 μm or less. The laser to be used is preferably one that can be ablated by ultraviolet absorption of 400 nm or less. Specifically, a laser having an oscillation wavelength of 400 nm or less, for example, a KrF excimer laser having an oscillation wavelength of 248 nm, a 308 nm XeCl excimer laser, a third harmonic of a 355 nm YAG laser, a fourth harmonic of 266 nm, or 400 nm or more. Titanium with a wavelength in the vicinity of 750 nm to 800 nm is capable of absorbing light in the ultraviolet region through a multiphoton absorption process and capable of cutting with a width of 20 μm or less by multiphoton absorption ablation. A laser having a pulse width of 1e-9 seconds (0.000000001 seconds) or less, such as a sapphire laser, is suitable.
[0008]
The workpiece to be processed in the present invention is not particularly limited as long as it can be processed by ultraviolet absorption ablation of the laser beam output by the laser. For example, various sheet materials, circuit boards, semiconductor wafers, glass Examples include a substrate, a ceramic substrate, a metal substrate, a light emitting or receiving element substrate such as a semiconductor laser, a MEMS (Micro Electro Mechanical System) substrate, a semiconductor package, cloth, leather, and paper.
Various sheet materials include, for example, polyimide resins, polyester resins, epoxy resins, urethane resins, polystyrene resins, polyethylene resins, polyamide resins, polycarbonate resins, silicone resins, fluorine resins, etc. Molecular film or non-woven fabric, those obtained by drawing or impregnating those resins with physical or optical functions, metal sheets such as copper, aluminum, stainless steel, or the above polymer sheets and / or metal sheets directly or The one laminated with an adhesive or the like is raised.
Examples of the circuit board include single-sided, double-sided or multilayer flexible printed boards, rigid boards made of glass epoxy, ceramic, metal core boards, etc., optical circuits formed on glass or polymers, or opto-electric hybrid circuit boards. .
[0009]
A specific pressure-sensitive adhesive sheet is bonded to the surface opposite to the laser irradiation surface of the workpiece thus prepared.
The pressure-sensitive adhesive sheet used in the present invention has a transmittance in a laser light absorption region of 50% or more, preferably 70% or more, and more preferably 90% or more. If the transmittance is less than 50%, the adhesive sheet is cut or punched by laser irradiation, and the residue of the decomposition product is firmly attached from the suction plate to the workpiece surface. There is a problem of falling.
[0010]
Such a pressure-sensitive adhesive sheet is obtained by providing a pressure-sensitive adhesive layer on a substrate, and examples of the substrate include, but are not limited to, plastic films and sheets such as polyester and olefin resin. Specifically, low density polyethylene, linear low density polyethylene, high density polyethylene, stretched polypropylene, non-stretched polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer Examples thereof include a sheet made of a polymer, an ethylene- (meth) acrylic acid ester copolymer, polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyimide, ionomer, or a fluororesin. The substrate sheet may be a single layer or a multilayer as long as it cannot be cut as a whole. Various shapes such as a film shape and a mesh shape can be selected.
The base material may not particularly have a cutting property with respect to a cutting means such as a cutter used for cutting the workpiece. The base material needs to be made of a material that can transmit a predetermined amount or more of energy rays, and the transmittance varies depending on the output of the laser beam and the spot irradiation time, but is usually 50% or more, preferably 85% or more. Good.
The thickness of the substrate can be appropriately selected within a range that does not impair the operability and workability in each step such as pasting of workpieces, cutting of workpieces, peeling of cut pieces, and recovery, but is usually 500 μm or less, Preferably it is about 3-300 micrometers, More preferably, it is about 5-250 micrometers. For the surface of the substrate, for example, conventional surface treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage bombardment exposure, ionizing radiation treatment are performed in order to improve adhesion and retention with adjacent layers such as an adsorption stage. A chemical or physical treatment such as a coating or a coating treatment with a primer (for example, an adhesive substance described later) may be applied.
[0011]
As the pressure-sensitive adhesive layer, an appropriate pressure-sensitive adhesive such as acrylic or rubber can be used.
Examples of the acrylic polymer include methyl group, ethyl group, purpyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, heptyl group, cyclohexyl group, 2 -30 or less carbon atoms such as ethylhexyl, octyl, isooctyl and nonyl, isononyl and decyl, isodecyl and undecyl, lauryl and tridecyl, tetradecyl and stearyl, octadecyl and dodecyl Examples thereof include polymers composed of one or more esters of acrylic acid or methacrylic acid having 4-18 linear or branched alkyl groups. Other monomers that may form the polymer include, for example, acrylic acid and methacrylic acid, carboxyethyl acrylate and carboxypentyl acrylate, itaconic acid and maleic acid, carboxyl group-containing monomers such as fumaric acid and crotonic acid, or Acid anhydride monomers such as maleic anhydride and itaconic anhydride, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and (meth) acrylic acid 6 -Hydroxyhexyl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate Sulfones such as monomers, styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalene sulfonic acid Examples include acid group-containing monomers and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.
[0012]
In addition, a polyfunctional monomer or the like can be used as a monomer component for copolymerization, if necessary, for the purpose of crosslinking the acrylic polymer. Examples of such monomers include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di ( (Meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol. Examples include tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate. As the polyfunctional monomer, one type or two or more types can be used, and the use amount thereof is preferably 30% by weight or less of the total monomers from the viewpoint of adhesive properties and the like. The acrylic polymer may have a photopolymerizable carbon-carbon double bond in the molecule.
The acrylic polymer can be prepared by applying an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method or a suspension polymerization method to a mixture of one or two or more component monomers.
[0013]
The pressure-sensitive adhesive layer preferably has a composition that suppresses the inclusion of a low-molecular-weight substance from the viewpoint of preventing contamination of the workpiece. From this point, an acrylic polymer having a number average molecular weight of 300,000 or more, especially 400,000 to 3,000,000 Since the main component is preferable, the pressure-sensitive adhesive can be of an appropriate crosslinking type by an internal crosslinking method, an external crosslinking method, or the like.
Examples of oligomers that can be used for the crosslinking type include urethane, (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) Examples thereof include acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and l, 4 monobutylene glycol di (meth) acrylate. Further, the blending amount of the oligomer is desirably 5 to 500 parts by weight with respect to 100 parts by weight of the main polymer, and particularly desirably 70 to 150 parts by weight. Examples of the photopolymerization initiator that may be blended in the radiation curable component monomer mixture in the case where a curing method using ultraviolet rays or the like is adopted include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2) Propyl) ketone, α-hydroxy-α, α-methylacetophenone, methoxyacetophenone, 2,2-dimethoxy-21-phenylacetophenone, 2,2-diethoxyacetophenone, 11-hydroxycyclohexyl phenylketone, 2-methyl-1- [4- Acetophenone compounds such as (methylthio) -phenylco-2-morpholinopropane-1, benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether and anisoin methyl ether, and 2-methyl-2-hydroxypropionic phenone Α-ketol compounds, ketal compounds such as benzyl dimethyl ketal, aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride, 1-phenone-1, l-propanediene-2- (o-ethoxycarbonyl) oxime Photoactive oxime compounds such as benzophenone and benzoylbenzoic acid, benzophenone compounds such as 3,3′-dimethyl-4-methoxybenzophenone, thioxanthone and 2-chlorothioxanthone, 2-methylthioxanthone and 2,4 Thioxanthone compounds such as dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone and 2,4-diisopropylthioxanthone, camphorquinone and halogenated ketones A Such as Le phosphino sulfoxide or acyl phosphine Honor bets and the like.
[0014]
The crosslink density of the pressure-sensitive adhesive layer is controlled by, for example, a suitable cross-linking agent such as a polyfunctional isocyanate compound, an epoxy compound, a melamine compound, a metal salt compound, a metal chelate compound, an amino resin compound, or a peroxide. It is possible to carry out by an appropriate method such as a method of crosslinking via a method or a method of mixing a low molecular compound having two or more carbon / carbon double bonds and crosslinking by irradiation with energy rays.
[0015]
The thickness of the pressure-sensitive adhesive layer can be appropriately selected as long as it does not peel from the workpiece and the target adherend, but is usually about 5 to 300 μm, preferably about 10 to 100 μm, more preferably about 20 to 50 μm. is there.
The adhesive strength of the pressure-sensitive adhesive layer is 20 N / 20 mm or less based on the adhesive strength (90-degree peel value, peeling speed 300 mm / min) at normal temperature (before laser irradiation) to SUS304, and in particular 0.001 to 10 N / 20 mm, particularly 0.01 to 8 N / 20 mm is preferable.
[0016]
In the processing method of the present invention, for example, in the case of cutting, the workpiece-adhesive obtained by bonding the workpiece 1 and the pressure-sensitive adhesive sheet 2 together by a known means such as a roll laminator or a press as shown in FIG. By condensing and irradiating a laser beam 3 output from a predetermined laser oscillator onto a workpiece with a lens on the sheet laminate, and moving the laser irradiation position along a predetermined processing line Perform cutting. As the laser beam moving means, a known laser processing method such as a galvano scan, an XY stage scan, or a mask imaging process is used. The laser processing conditions are not particularly limited as long as the workpiece can be completely cut, but in order to avoid cutting up to the pressure-sensitive adhesive sheet, it is within two times the conditions under which the workpiece is cut. It is preferable to do. In addition, the cutting margin can be made narrower by narrowing the beam diameter of the laser beam condensing part.
Beam diameter (μm)> 2 × (laser beam moving speed (μm / sec) / laser repetition frequency (Hz))
Is preferably satisfied.
[0017]
In the case of drilling, as shown in FIG. 2, the workpiece 1 and the adhesive sheet 2 are bonded to each other on a workpiece-adhesive sheet laminate obtained by bonding the workpiece 1 and the adhesive sheet 2 by a known means such as a roll laminator or a press. A laser beam 3 output from the laser oscillator is condensed and irradiated onto a workpiece by a lens to form a hole. The hole is formed by a known laser processing method such as galvano scan, XY stage scan, or punching by mask imaging. The laser processing condition may be determined as an optimum value based on the ablation threshold of the material to be processed. However, in order to avoid cutting to the adhesive sheet, the processing condition 2 in which a through-hole is formed in the workpiece is used. It is preferable to make it within the range.
[0018]
In addition, by laminating a sheet with good laser processability or an adhesive sheet on the laser incident side, or by blowing a gas such as helium, nitrogen, or oxygen to the laser processing part, the surface of the workpiece on the laser incident side It is further preferable that the residue can be easily removed.
[0019]
In the present invention, the pressure-sensitive adhesive sheet 2 is peeled after the processing is completed. The method of peeling is not limited, but it is important that no stress is applied so that the workpiece is permanently deformed during peeling. For example, it is preferable to use a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive strength is reduced by ultraviolet irradiation or heating, because it has both a holding power during processing and ease of peeling.
[0020]
Further, in the cutting of the semiconductor wafer, a workpiece 1-adhesive obtained by bonding a pressure-sensitive adhesive sheet to one surface of the semiconductor wafer as shown in FIG. 4 by a known method described in, for example, Japanese Patent Application Laid-Open No. 2002-343747. The laser beam 3 output from a predetermined laser oscillator is condensed and irradiated onto the workpiece 1 from the side where the adhesive sheet 2 is not pasted on the sheet 2 laminate, and its laser irradiation position Is cut along a predetermined processing line. As a laser beam moving means, a known laser processing method such as galvano scan, XY stage scan, mask, or imaging processing is used. In such cutting of a semiconductor wafer, a method of picking up using a push-up pin called a needle by a conventionally known device such as a die bonder after cutting into individual chips, or disclosed in Japanese Patent Laid-Open No. 2001-118862. Individual chips can be picked up by a known method such as a method. Therefore, the processing conditions for the semiconductor wafer are not particularly limited as long as the semiconductor wafer is cut and the entire adhesive sheet is not cut.
[0021]
【Example】
Next, examples of the present invention will be described in more detail.
Example 1
A UV-curable acrylic pressure-sensitive adhesive solution is applied onto a substrate composed of three layers of polyethylene / polypropylene / polyethylene with a thickness of 100 μm and dried to form a pressure-sensitive adhesive layer with a thickness of 20 μm. A sheet was obtained. The light transmittance (355 nm) of this base material was 80.0%.
The light transmittance was measured using MPS-2000 (manufactured by Shimadzu Corporation) as a measuring device, and the measurement range was 190 nm to 800 nm. The sample size was cut to an appropriate size, the substrate was measured from the side where the adhesive was applied and present, and the light transmittance of the adhesive sheet was measured from the adhesive side (the same applies hereinafter). .
The UV curable acrylic pressure-sensitive adhesive solution used was a weight average obtained by copolymerizing butyl acrylate, ethyl acrylate, 2-hydroxy acrylate, and acrylic acid at a weight ratio of 60/40/4/1. 100 parts by weight of an acrylic polymer having a molecular weight of 800,000, 90 parts by weight of dipentaerythritol monohydroxypentaacrylate as a photopolymerizable compound, and benzyldimethyl ketal (Irgacure 651) as a photopolymerization initiator 5 parts by weight, and these are uniformly dissolved in toluene as an organic solvent. The light transmittance (355 nm) of this adhesive sheet was 78.9%.
Even if the third harmonic of a YAG laser having a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz is condensed on the pressure-sensitive adhesive sheet by an fθ lens, and the laser beam is moved at a speed of 10 mm / second, the pressure-sensitive adhesive sheet It was not cut.
[0022]
The pressure-sensitive adhesive sheet is bonded to a 25 μm-thick polyimide film with a roll laminator, and the pressure-sensitive adhesive sheet bonding surface side is placed on the XY stage on which a stainless steel suction plate is placed, with a wavelength of 355 nm, an average output of 5 W, The third harmonic of a YAG laser with a repetition rate of 30 kHz is condensed on the surface of the polyimide film by an fθ lens to a diameter of 25 μm, and the galvano scanner scans the laser light at a speed of 20 mm / second to cut the polyimide film. went. At this time, it was confirmed that the polyimide film was cut but the adhesive sheet was not cut.
Then, when the adhesive sheet was peeled off and the periphery of the cut end face of the adhesive sheet bonding surface (laser emission surface) of the polyimide film was observed, no deposits due to the adsorption plate were observed.
[0023]
Comparative Example 1
In Example 1, except for sticking the adhesive sheet, through the same process, when the periphery of the cutting end surface on the laser emission surface side was observed, a large amount of decomposition product residue from the glass epoxy plate used as the adsorption plate It was attached.
Thereafter, removal of the residue was attempted by desmear treatment with an aqueous potassium permanganate solution, but the decomposition product residue was not completely removed. Furthermore, nickel was detected from the periphery, and it was confirmed that there was a residue from stainless steel.
[0024]
Comparative Example 2
An adhesive sheet was prepared in the same manner as in Example 1 except that a soft vinyl chloride film (thickness 70 μm) having a substrate transmittance of 35% was used. The light transmittance (355 nm) of this pressure-sensitive adhesive sheet was 34.4%.
When this adhesive sheet was irradiated with a laser under the same conditions as in Example 1, the adhesive sheet was cut.
In Example 1, when the same process was performed except using said adhesive sheet, not only a polyimide film but the adhesive sheet was cut | disconnected.
[0025]
Example 2
A UV curable acrylic pressure-sensitive adhesive solution was applied onto a substrate made of a polyethylene film having a thickness of 100 μm and dried to form a pressure-sensitive adhesive layer having a thickness of 30 μm, thereby obtaining a pressure-sensitive adhesive sheet. The light transmittance (355 nm) of this base material was 85.5%.
The UV curable acrylic pressure-sensitive adhesive solution used was a copolymer composition of 50 parts by weight of ethyl acrylate, 50 parts by weight of butyl acrylate, and 16 parts by weight of 2-hydroxyethyl acrylate in a toluene solution. Thus, an acrylic polymer having a weight average molecular weight of 500,000 is obtained, 20 parts by weight of 2-methacryloyloxyethyl isocyanate is added to 100 parts by weight of the copolymer, and a carbon-carbon double bond is added to the polymer molecule inner chain. (The length of the side chain at this time is 13 in terms of the number of atoms), and with respect to 100 parts by weight of this polymer, 1 part by weight of a polyisocyanate-based crosslinking agent (Coronate L) and α- Mix 3 parts by weight of hydroxyketone (Irgacure 184) and dissolve them uniformly in toluene as an organic solvent. It become one. The light transmittance (355 nm) of this pressure-sensitive adhesive sheet was 69.7%.
[0026]
On the other hand, a circuit is formed through a process of exposure, development and etching on a two-layer base material in which a copper layer having a thickness of 18 μm is formed on a polyimide film having a thickness of 25 μm, and an epoxy adhesive having a thickness of 15 μm is formed on the polyimide film having a thickness of 13 μm. The cover film having the layer formed thereon was bonded to prepare a flexible printed board. The flexible printed circuit board and the pressure-sensitive adhesive sheet are bonded together using a roll laminator, and the pressure-sensitive adhesive sheet bonding surface is placed on the XY stage on which an alumina ceramic suction plate is placed. The wavelength is 355 nm, the average output is 5 W, The third harmonic of a YAG laser having a repetition frequency of 30 kHz was condensed on the surface of the polyimide film by an fθ lens to a diameter of 25 μm, and was cut by scanning with a galvano scanner at a speed of 20 mm / second. At this time, it was confirmed that the flexible printed circuit board was cut but the adhesive sheet was not cut.
Then, when the adhesive sheet was peeled and the periphery part of the cut end surface of the adhesive sheet bonding surface (laser emission surface) of the flexible printed circuit board was observed, no deposit due to the suction plate was observed.
[0027]
Comparative Example 3
On the base material which consists of a 80-micrometer-thick polyethylene film, the acrylic adhesive solution was apply | coated and dried, and the adhesive sheet which formed the 10-micrometer-thick adhesive layer was created. The light transmittance (355 nm) of this base material was 83.6%.
The UV curable acrylic pressure-sensitive adhesive solution used was an acrylic having a weight average molecular weight of 800,000, which was obtained by copolymerizing methyl acrylate, 2-ethylhexyl, and acrylic acid at a weight ratio of 70/30/10. 100 parts by weight of a polymer, 100 parts by weight of dipentaerythritol monohydroxypentaacrylate as a photopolymerizable compound, and 5 parts by weight of α-aminoketone (Irgacure 369) as a photopolymerization initiator, These are uniformly dissolved in ethyl acetate as an organic solvent.
The light transmittance (355 nm) of this pressure-sensitive adhesive sheet was 49.6%.
When this adhesive sheet and a flexible printed circuit board were bonded together with a roll laminator and cut under the same conditions as in Example 2, not only the flexible printed circuit board but also the adhesive sheet had been cut. In addition, aluminum that was considered to be due to the suction plate was detected from the periphery of the cut surface.
[0028]
Example 3
On the base material which consists of a 80-micrometer-thick polyethylene film, the acrylic adhesive solution was apply | coated and dried, and the adhesive sheet which formed the 5-micrometer-thick adhesive layer was created. The light transmittance (355 nm) of this base material was 85.5%.
The acrylic pressure-sensitive adhesive solution is epoxy based on 100 parts by weight of an acrylic polymer having a polymerization average molecular weight of 1,000,000 obtained by polymerization of 2-ethylhexyl acrylate, N-acryloylmorpholine and acrylic acid at 70/30/3. 2 parts by weight of a cross-linking agent (Tetrad C, manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 2 parts by weight of an isocyanate-based cross-linking agent (Coronate L, manufactured by Nippon Polyurethane) are mixed uniformly in toluene as an organic solvent. It is.
The light transmittance (355 nm) of this adhesive sheet was 84.7%.
This pressure-sensitive adhesive sheet and a 18 μm-thick copper foil are bonded together, and the pressure-sensitive adhesive sheet bonding surface is placed on an XY stage on which a suction plate obtained by spraying zirconia on a stainless steel plate is placed. The third harmonic of a YAG laser having an output of 5 W and a repetition frequency of 30 kHz was condensed on a copper surface by an fθ lens to a diameter of 25 μm, and the laser beam was scanned at a speed of 10 mm / second by a galvano scanner to perform cutting processing. . At this time, it was confirmed that the copper foil was cut but the adhesive sheet was not cut.
Then, when the adhesive sheet was peeled off and the periphery of the cut end surface of the adhesive sheet bonding surface (laser emission surface) of the copper foil was observed, no deposits due to the adsorption plate were observed.
[0029]
Example 4
The pressure-sensitive adhesive sheet obtained in Example 1 was placed on an XY stage on which a glass epoxy resin adsorption plate was placed, and the third harmonic of a YAG laser having a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz was collected to a diameter of 20 μm by an fθ lens. Even when the light was scanned and the laser light was scanned by a galvano scanner, no opening was formed in the adhesive sheet.
[0030]
On an XY stage on which a pressure-sensitive adhesive sheet of Example 1 was bonded with a roll laminator on one side of a double-sided copper-clad substrate in which 9 μm copper foil was bonded to both sides of a 25 μm-thick polyimide film, and a glass epoxy resin adsorption plate was placed The surface of the adhesive sheet is placed on the surface of the suction plate, and the third harmonic (355 nm) of a YAG laser with a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz is applied to the surface of the double-sided copper-clad plate with an fθ lens. Then, a laser beam was scanned by a galvano scanner to form a through hole having a diameter of 100 μm. At this time, it was confirmed that the adhesive sheet did not penetrate. The drilling speed at this time was 300 holes / second.
Thereafter, the pressure-sensitive adhesive sheet was peeled off, and the periphery of the processed hole on the pressure-sensitive adhesive sheet bonding surface (laser emission surface) of the copper-coated double-sided plate was observed, and no deposit was observed.
[0031]
Comparative Example 4
In Example 4, when the periphery of the opening on the laser emission surface side is observed through exactly the same process except that an adhesive sheet is stuck, a large amount of decomposition product residue from the glass epoxy plate used as the adsorption plate adheres. Was.
Thereafter, removal of the residue was attempted by desmear treatment with an aqueous potassium permanganate solution, but the decomposition product residue was not completely removed.
[0032]
Comparative Example 5
When the pressure-sensitive adhesive sheet obtained in Comparative Example 2 was subjected to laser irradiation under the same conditions as in Example 4, an opening of 100 μmφ was formed in the pressure-sensitive adhesive sheet.
In Example 4, the same process was performed except that the pressure-sensitive adhesive sheet of Comparative Example 2 was used. Through holes were formed up to the pressure-sensitive adhesive sheet as well as the double-sided copper-clad plate. The decomposition product of was attached.
[0033]
Example 5
The pressure-sensitive adhesive sheet obtained in Example 2 was bonded to a polyimide film having a thickness of 50 μm. This sheet is fixed on a stainless steel adsorption stage with the adhesive sheet side as the stage side, and the third harmonic of a YAG laser having a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz is condensed on the polyimide film and incident. A through hole having a side opening diameter of 30 μm and an emission side (adhesive sheet bonding side) opening diameter of 20 μm was formed. At this time, the adhesive sheet was not opened.
Thereafter, the adhesive sheet was peeled off and the periphery of the opening was observed. As a result, the edge of the exit side opening was sharp, no deposits were observed, and desmear treatment in the subsequent process was unnecessary.
[0034]
Comparative Example 6
Except for the step of sticking an adhesive sheet in Example 5, the periphery of the laser-processed opening was observed after passing through the exact same process. As a result, the opening swelled due to the influence of heat and could not be put to practical use.
Further, when the periphery of the opening was analyzed after the desmear treatment, nickel was detected, and it was confirmed that the residue from the stainless steel remained after the post-treatment.
[0035]
Example 6
On the base material which consists of a 80-micrometer-thick polyethylene film, the acrylic adhesive solution was apply | coated and dried, and the adhesive sheet which formed the 10-micrometer-thick adhesive layer was created. The light transmittance (355 nm) of this base material was 81.9%.
The acrylic adhesive solution used was an acrylic polymer having a weight average molecular weight of 600,000 obtained by copolymerizing 2-ethylhexyl acrylate, methyl acrylate and acrylic acid in a weight ratio of 50/50/2. -To 100 parts by weight, 3.5 parts by weight of isocyanate-based crosslinking agent (Coronate L, manufactured by Nippon Urethane), 0.05 parts by weight of reaction catalyst (OL-1, manufactured by Tokyo Fine Chemical), plasticizer (dibutoxyethoxy adipate) Ethyl) 15 parts by weight are blended, and these are uniformly dissolved in toluene as an organic solvent. The light transmittance (355 nm) of this pressure-sensitive adhesive sheet was 74.1%.
The pressure-sensitive adhesive sheet thus obtained was bonded to a polycarbonate film having a thickness of 25 μm, fixed on the stage with the pressure-sensitive adhesive sheet face down, and irradiated with a third harmonic of a YAG laser having a wavelength of 355 nm and 15 kHz from the upper surface through a mask. An opening having a diameter of 25 μm was formed by a mask imaging method. At that time, the energy density of the laser beam on the workpiece was 600 mJ / cm 2. Then, when the adhesive sheet was peeled off and the peripheral part of the opening part on the laser emission side of the polycarbonate film was observed with a microscope, no deposit was observed.
[0036]
【The invention's effect】
As described above, when the present invention is used, it is possible to prevent the decomposition product residue during processing by laser, particularly the decomposition product residue from the stage for fixing the workpiece, greatly reducing the subsequent process of removing the adhesion material. In addition to being able to simplify the process, it is possible to contribute to reducing the environmental load, and it is possible to process the cut part and the opening part more sharply. Further, since the workpiece does not fall off after the processing is completed, handling becomes easy. Furthermore, since it is possible to avoid adhesion of decomposition products from the stage, it is possible to achieve an increase in throughput by increasing the power of the laser.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a processing method of the present invention.
FIG. 2 is a schematic view showing an example of a processing method of the present invention.
FIG. 3 is a cross-sectional view schematically showing a processing method of the present invention.
FIG. 4 is a schematic view showing an example of the processing method of the present invention.
[Explanation of symbols]
1 Workpiece
2 Adhesive sheet
3 Laser light

Claims (4)

A method of processing a workpiece using ultraviolet absorption ablation of a laser,
(1) A step of attaching an adhesive sheet having a transmittance of 50% or more in the laser light absorption region to the surface opposite to the laser irradiation surface of the workpiece;
(2) A process of processing a workpiece by irradiating the workpiece with a laser;
(3) A method for processing a workpiece, comprising a step of peeling the pressure-sensitive adhesive sheet. The workpiece is one of a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser or other light emitting or receiving element substrate, a MEMS substrate, a semiconductor package, cloth, leather, or paper. The processing method of the workpiece of Claim 1 characterized by these. 3. The processing method for a workpiece according to claim 1, wherein the processing is either cutting or drilling. It is an adhesive sheet used for the processing method of the to-be-processed object of Claims 1-3, Comprising: The adhesive sheet in the absorption area | region of this laser beam is 50% or more.

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