JP2001244604A - Method of forming through-hole with carbon dioxide gas laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a through-hole to prevent contamination of the surface of copper foil of a copper clad plate on the occasion of forming the through-hole with the carbon dioxide gas laser. SOLUTION: In a method of forming a through-hole on a copper clad plate wherein an etching film or a liquid etching resist (a) is allocated on a copper foil (b) to which the copper foil surface process is executed to enable the formation of a through-hole with the carbon dioxide gas laser, after the film or resist is removed from the area (c) as the target mark, the copper foil of this area is removed by the etching to form a target mark (e), this target mark is read with a CCD camera (d) and an external layer and internal layer copper foils are removed to form a through-hole (f) and/or a blind via hole by direct radiation of the high output carbon dioxide gas laser to the film or resist, and the burs (h) generated on the rear surface of copper foil and copper foil of internal layer are removed by the etching process while maintaining the film or resit as it is. Thereby, in the manufacture of a high density printed circuit board, a through-hole and/or a blind via hole may be formed with direct radiation of carbon dioxide gas laser without any contamination of the copper foil of the surface layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a through hole and / or a blind via hole in a copper-clad laminate by a novel carbon dioxide gas laser, including a treatment of a copper foil burr generated in a hole. A printed wiring board using a copper-clad board with this small-diameter hole formed has a high-density small-diameter hole and a high-density small-sized printed wiring board with a fine pattern. Mainly used.

[0002]

2. Description of the Related Art Conventionally, in a high-density printed wiring board used for a semiconductor plastic package or the like, a through hole is formed by a mechanical drill. In recent years, the diameter of drills has become smaller and smaller, and the hole diameter has been reduced to 0.15 mmφ or less.When drilling such small holes, the drill diameter is small, so the drill bends, breaks, and the processing speed when drilling. It has disadvantages such as slowness, and has problems in productivity, reliability, and the like. The blind via hole has been formed by etching the copper foil at the position where the hole is to be drilled in advance and then using a low-energy carbon dioxide laser. Further, the target mark was formed at the same time as the etching. In this method, only a blind via hole can be formed by a carbon dioxide laser, and a through hole is separately formed by mechanical drilling or the like, so that the process is long and the work efficiency is poor.

[0003] As a method of forming a through-hole, holes of the same size are formed in advance on a copper foil on the front and back sides using a negative film by a predetermined method. There is a method of arranging those formed in the above and forming a hole penetrating the front and back with a carbon dioxide laser.
However, this method has disadvantages such as misalignment of the inner layer copper foil, gaps between the upper and lower land copper foils and the holes, poor connection, and inability to form front and back lands. In addition, there is a problem that the residue of copper foil, glass fiber, resin, and the like scattered upward when drilling holes by a carbon dioxide laser drops and adheres. Copper plating with the residue adhered has the problems that copper plating unevenness occurs and the connection reliability of holes is lacking.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for forming a hole in a copper clad board which solves the above problems.

[0005]

According to the present invention, there is provided a method of forming a through hole and / or a blind via hole in a copper clad plate by a carbon dioxide gas laser. After attaching an etching resist or liquid etching solder resist to the front and back surfaces of the copper clad board that has been subjected to the copper foil surface treatment, the film or resist is removed only at the target mark for laser drilling, and the copper foil in this part is removed. After removing the target mark by etching or exposing the target mark formed on the inner layer plate, read this target mark with a CCD camera to determine the position, and drilling copper foil directly from the film or resist A carbon dioxide laser beam of sufficient energy to form through holes and / or blind via holes And the copper scattered during drilling, glass, even if residue of such resins have fallen on the plate can be prevented adherence of the copper foil. Thereafter, the film or the resist is left as it is, and after removing the copper foil burrs generated in the holes by etching with a chemical solution, a hole is formed in the copper clad board where the film or the resist is peeled off. The copper-clad board perforated by the method of the present invention is used for manufacturing a printed wiring board.

[0006] The surface treatment of the copper foil is not particularly limited, as long as the hole processing can be performed by directly irradiating a carbon dioxide gas laser. Preferably, nickel treatment, nickel alloy treatment, metal oxide treatment, chemical solution treatment and the like can be used.

A circuit is formed on both sides by using a double-sided board obtained by plating up a copper-clad board after forming holes with copper plating.
Printed wiring board by the usual method. In order to make the front and back circuits fine, the copper foil of the front and back layers is 2 to 7 μm, preferably 3 to 5 μm.
It is preferable to use one of μm. In this case, it is possible to produce a high-density printed wiring board without any defect such as short circuit or cut pattern even when copper plating is performed. Furthermore, the processing speed was remarkably faster than that obtained by drilling, and a product having good productivity and excellent economic efficiency was obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for forming a hole in a copper-clad plate, which is free from contamination due to falling of a workpiece such as a copper foil, a glass fiber, a resin, etc. in a copper foil direct drilling process of a carbon dioxide laser. The present invention relates to an opening method and a post-processing method for removing copper foil burrs thereafter, and a printed wiring board is prepared using the method. First, in a copper-clad board including a multilayer board obtained by using a copper foil subjected to a copper foil surface treatment capable of forming holes by direct irradiation of a carbon dioxide gas laser, an etching film or a liquid etching solder resist is applied to the front and back surfaces of the copper-clad board. After attaching the film, remove the film or resist at the target mark and remove the copper foil by etching to form the target mark, or after exposing the target mark on the inner layer board, the target mark from above with a CCD camera After reading and determining the position, a carbon dioxide laser is irradiated directly from above the film or resist with a carbon dioxide laser having sufficient energy to process the copper foil to make through holes and / or blind via holes in the copper clad plate. . Thereafter, the copper foil burrs generated in the holes are dissolved and removed with an etching film or a chemical solution that does not dissolve the liquid solder resist, and then the film or the resist is removed, and a printed wiring board is formed by a generally known method.

In the present invention, there is no particular limitation on the surface treatment that can be perforated by directly irradiating a carbon dioxide gas laser onto the copper foil, and examples thereof include nickel treatment and nickel alloy treatment. There are nickel treatment, nickel plating, nickel vapor deposition, and the like. As the nickel alloy treatment, a known treatment such as a nickel-cobalt alloy can be used. In addition, metal oxide treatment such as black copper oxide treatment, and chemical treatment such as CZ treatment (MEC) may be used.

[0010]

[0011] The target mark (alignment mark) has a size that can be read by a CCD camera.
Preferably, it refers to a circular mark. This mark is read first, the dimension is corrected by a function programmed to automatically perform the dimension correction, and a hole is formed in a predetermined position by a laser. As a result, the dimension is automatically corrected so that the position of the hole is located at the designed position, no deviation occurs, and the occurrence of defects is eliminated. The shape of the hole is not particularly limited, but is preferably circular. Specifically, a method of drilling a hole to make this hole a target mark, a method of leaving a copper foil in a circular shape by etching, a method of exposing a resin surface by etching a copper foil in a circular shape and forming this as a target mark A generally known method such as a method for performing the method can be employed. In the case of a double-sided copper clad board, it is formed on the outer layer. In the case of a multilayer board, it is generally formed on an inner layer board, and even if there is shrinkage of the inner layer plate during multilayer molding,
Dimension correction can be automatically performed by reading with a CCD camera compared to the design. The formation position is formed at least at two corners, preferably at least three corners of the substrate.

An etching film is a resin film used for etching a copper foil.
Acrylate groups and carboxyl groups (-
(COOH) in the molecule. This film is heated, laminated and adhered to the surface of the copper-clad board, and a negative film is placed on this film so that the part where the copper foil is left transmits light, and ultraviolet light is irradiated from above. Thereafter, an alkaline developing solution (generally, a 1% by weight aqueous solution of sodium carbonate) is sprayed to dissolve and remove the portions not irradiated with light, and the copper foil is etched and removed. After piercing with a carbon dioxide laser, the etching film is dissolved and removed with an alkaline chemical (aqueous sodium hydroxide solution). Of course, generally known films such as an etching film containing other functional groups can be used.

[0013] A liquid etching solder resist is used for etching a copper foil by mixing a resin containing an acrylate group and a carboxyl group in a molecule with another liquid compound in the same manner as an etching film. It is a composition used for. This is applied on a copper-clad plate, irradiated with ultraviolet rays through a negative film, and the portions not irradiated with the ultraviolet rays are dissolved and removed with an alkaline developer, and then the copper foil is removed by etching. Of course, a generally known liquid etching solder resist other than this form can also be used.

In the present invention, at least one copper-clad board is used.
It is used to include a copper-clad board or a multilayer board having two or more copper layers, preferably two or more copper layers. As the copper-clad plate, a substrate-reinforced substrate, a film substrate, a resin alone having no reinforcing substrate, or the like can be used. However, from the viewpoint of dimensional shrinkage and the like, a glass cloth-based copper-clad plate is preferred. Also, when creating a high-density circuit, the surface copper foil is
It is better to use a thin one from the beginning. The thickness is not particularly limited, but it is preferable to use a copper foil of 2 to 7 μm, preferably 3 to 5 μm. In this case, a copper foil with a carrier such as aluminum or copper foil is used. Dissolve and remove a part of the surface copper foil from a copper-clad board in advance and 2 ~ 7μ
m can be used.

As the base material of the copper clad board, generally known organic and inorganic woven fabrics and nonwoven fabrics can be used. Specifically, examples of the inorganic fibers include fibers such as E, S, D, and M glass. Examples of the organic fibers include wholly aromatic polyamide, liquid crystal polyester, and polybenzazole. These may be mixed. Films such as a polyimide film can also be used.

As the resin of the thermosetting resin composition of the copper clad board used in the present invention, generally known thermosetting resins are used. Specifically, an epoxy resin, a polyfunctional cyanate ester resin, a polyfunctional maleimide-cyanate ester resin, a polyfunctional maleimide resin, an unsaturated group-containing polyphenylene ether resin, and the like, and one or more kinds Are used in combination. From the point of the through hole shape in processing by high output carbon dioxide laser irradiation,
A thermosetting resin composition having a glass transition temperature of 150 ° C. or higher is preferred, and a polyfunctional cyanate resin composition is preferred from the viewpoints of moisture resistance, migration resistance, electrical properties after moisture absorption, and the like.

The polyfunctional cyanate compound which is a preferred thermosetting resin component of the present invention is a compound having two or more cyanato groups in the molecule. Specific examples include 1,3- or 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene, 1,3-, 1,4-, 1,6-, 1,8-, 2 , 6- or 2,7-
Dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, 4,4-dicyanatobiphenyl, bis (4-dicyanatophenyl) methane, 2,2-bis (4-cyanatophenyl) propane, 2,2- Bis (3,5-dibromo-4-cyanatophenyl) propane, bis (4-cyanatophenyl) ether, bis (4-cyanatophenyl) thioether, bis (4-cyanatophenyl) sulfone, tris (4-cy (Anatophenyl) phosphite, tris (4-cyanatophenyl) phosphate, and cyanates obtained by reacting novolak with cyanogen halide.

In addition to these, Japanese Patent Publication Nos. 41-1928 and 43-1846
8, polyfunctional cyanate compounds described in JP-A-44-4791, JP-A-45-11712, JP-A-46-41112, JP-A-47-26853 and JP-A-51-63149 can also be used. Further, a prepolymer having a molecular weight of 400 to 6,000 and having a triazine ring formed by trimerization of a cyanato group of these polyfunctional cyanate compounds is used. This prepolymer is obtained by polymerizing the above-mentioned polyfunctional cyanate ester monomer with a catalyst such as an acid such as a mineral acid or a Lewis acid; a base such as a tertiary amine such as sodium alcoholate; or a salt such as sodium carbonate. It can be obtained by: The prepolymer also contains some unreacted monomers and is in the form of a mixture of the monomer and the prepolymer, and such a raw material is suitably used for the purpose of the present invention. Generally, it is used after being dissolved in a soluble organic solvent.

As the epoxy resin, a generally known epoxy resin can be used. Specifically, liquid or solid bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, alicyclic epoxy resin, butadiene, pentadiene, vinylcyclohexene, dicyclopentyl ether, etc. And polyglycidyl compounds obtained by reacting a polyol, a hydroxyl-containing silicone resin with an epohalohydrin, and the like. These may be used alone or in combination of two or more.

As the polyimide resin, generally known ones can be used. Specific examples include a reaction product of a polyfunctional maleimide and a polyamine, and a polyimide having a terminal triple bond described in JP-B-57-005406. These thermosetting resins may be used alone, but it is preferable to use them in an appropriate combination in consideration of the balance of properties.

Various additives can be added to the thermosetting resin composition of the present invention, if desired, as long as the inherent properties of the composition are not impaired. These additives include polymerizable double bond-containing monomers such as unsaturated polyesters and prepolymers thereof; polybutadiene, epoxidized butadiene, maleated butadiene, butadiene-
Low molecular weight liquid to high molecular weight elastic rubbers such as acrylonitrile copolymer, polychloroprene, butadiene-styrene copolymer, polyisoprene, butyl rubber, fluororubber, natural rubber; polyethylene, polypropylene, polybutene, poly-4-methyl Penten, polystyrene, AS
Resin, ABS resin, MBS resin, styrene-isoprene rubber,
Polyethylene-propylene copolymer, 4-fluoroethylene-
6-fluorinated ethylene copolymers; high molecular weight prepolymers or oligomers such as polycarbonate, polyphenylene ether, polysulfone, polyester, and polyphenylene sulfide; and polyurethane are exemplified and used as appropriate. In addition, other known organic and inorganic fillers,
Various additives such as dyes, pigments, thickeners, lubricants, defoamers, dispersants, leveling agents, photosensitizers, flame retardants, brighteners, polymerization inhibitors, and thixotropic agents may be used as desired. They are used in an appropriate combination. If necessary, the compound having a reactive group is appropriately blended with a curing agent and a catalyst. The copper-clad board used in the present invention can contain an insulating inorganic filler in the thermosetting resin composition. Especially for carbon dioxide laser drilling,
10 to 80% by weight, preferably 20 to 70% by weight is added in order to make the shape of the pores uniform. The kind of the insulating inorganic filler is not particularly limited. Specific examples include talc, calcined talc, aluminum hydroxide, magnesium hydroxide, kaolin, alumina, wollastonite, synthetic mica, and the like.
A mixture of two or more species is used.

The thermosetting resin composition itself is cured by heating, but if the curing rate is low, the workability and the economic efficiency are inferior. Therefore, a known thermosetting catalyst is used for the thermosetting resin used. Can be used. The amount used is 0.005 to 10 parts by weight, preferably 0.01 to 5 parts by weight, per 100 parts by weight of the thermosetting resin.

When a through-hole and / or a blind via hole is made by a carbon dioxide gas laser, the etching film or the liquid etching solder resist on the surface is left as it is, and a carbon dioxide laser preferably having an output of 10 to 60 mJ is applied from above. Direct irradiation, preferably 80-180 μm in diameter
Drill holes. In terms of preventing copper foil contamination of perforated copper and organic substances, by performing perforation while leaving the surface film or resist as it is, the scattered residue falls on the film or resist, effective for preventing copper foil contamination It is. The wavelength of the carbon dioxide laser is 9.3 to 10.6 μm. The energy is preferably 10 to 60 mJ, and a predetermined pulse is applied to form holes. In the case of drilling through holes and / or via holes, any of a method of irradiating holes with the same energy from the beginning to the end, and a method of piercing by increasing or decreasing the energy on the way may be used.

In drilling holes with the carbon dioxide laser of the present invention, burrs of the copper foil are generated around the holes. The method of etching and removing copper burrs generated in the holes is not particularly limited. For example, Japanese Patent Application Laid-Open Nos. 02-22887, 02-22896, and 02
-25089, 02-25090, 02-59337, 02-60189, 02-1
66789, 03-25995, 03-60183, 03-94491, 04-19
9592 and 04-263488, and a method of dissolving and removing a metal surface with a chemical (referred to as a SUEP method). The etching rate is generally 0.02 to 1.0 μm / sec. Further, when the copper foil burr of the inner layer is removed by etching, the etching is performed with the etching film and the etching resist of the surface layer as they are. After removing the copper foil burrs by etching, dissolving and removing the film or resist, a high-density printed wiring board is obtained. If the copper burrs of the holes are not removed, in the case of copper plating, particularly in the blind via holes, the copper plating of the burrs that overhang the holes may grow and close the holes, resulting in poor plating. .

A metal plate can be simply arranged on the back surface of the copper-clad plate to prevent the laser machine table from being damaged by the laser when the holes penetrate. It is preferable that the resin layer to which at least a part is adhered is adhered to the backside copper foil of the copper-clad multilayer board, and that the metal plate is peeled off after drilling the through holes.

In most cases, a resin layer having a heat of about 1 μm is left on the surface of the copper foil surface on the surface of the inner surface of the processed hole where the resin of the copper foil is adhered. This resin layer can be removed in advance by a generally known treatment such as a desmear treatment before etching. However, when the liquid does not reach the inside of the small-diameter hole, a residue of the resin layer remaining on the surface of the inner copper foil may be left behind, resulting in poor connection with copper plating. Therefore,
More preferably, the inside of the hole is first treated in a gas phase to completely remove the residual layer of the resin, and then the inside of the hole and the copper burrs on the front and back surfaces are removed by etching. In the case of a blind via hole, it is preferable to remove a resin residue at the bottom of the via hole by performing a gas phase treatment or a liquid phase treatment after removing the copper foil burr by etching. Of course, it is also possible to perform the gas phase treatment first and then remove the copper foil burrs. As the gas phase treatment, generally known treatments can be used, and examples thereof include a plasma treatment and a low-pressure ultraviolet treatment. As the plasma, low-temperature plasma in which molecules are partially excited by a high-frequency power source and ionized is used. For this, high-speed processing using ion bombardment and gentle processing using radical species are generally used, and reactive gases and inert gases are used as processing gases. As the reactive gas, oxygen is mainly used, and the surface is chemically treated. As the inert gas, an argon gas is mainly used. Using this argon gas or the like, physical surface treatment is performed. Physical treatment uses ion bombardment to clean the surface. The low ultraviolet ray is an ultraviolet ray having a short wavelength region, and irradiates a short wavelength region having a peak at 184.9 nm and 253.7 nm, and decomposes and removes the resin layer.

The inside of the hole can be subjected to ordinary copper plating.
It can also be filled by volume% or more.

For drilling, an excimer laser, a YAG laser or the like can of course be used. Further, the combined use of the lasers is also possible. A mechanical drill can also be used in combination.

[0029]

The present invention will be specifically described below with reference to examples and comparative examples. Unless otherwise specified, “parts” indicates parts by weight.

Example 1 900 parts of 2,2-bis (4-cyanatophenyl) propane,
100 parts of (maleimidophenyl) methane are melted at 150 ° C,
The mixture was reacted for 4 hours with stirring to obtain a prepolymer. This was dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide. Add bisphenol A type epoxy resin (trade name: Epicoat 1001, Yuka Shell Epoxy Co., Ltd.)
) And 600 parts of a cresol novolac type epoxy resin (trade name: ESCN-220F, manufactured by Sumitomo Chemical Co., Ltd.) were uniformly mixed and dissolved. Further, as a catalyst, zinc octylate 0.4
2,000 parts of an inorganic filler (trade name: calcined talc, Nippon Talc Co., Ltd., average particle size 4 μm), and 8 parts of black pigment, and uniformly stirred and mixed to prepare Varnish A. Obtained. This varnish is impregnated with a 100 μm thick glass woven fabric and
It dried at ° C, and prepared the prepreg (prepreg B) whose gel time (at 170 ° C) was 102 seconds and the content of the glass cloth was 50% by weight.

Electrolytic copper obtained by applying a nickel alloy treatment (also referred to as Japan Energy Y-treated LD foil) at 3 μm to both sides of a double-sided treated copper foil having a thickness of 5 μm is placed on the front and back of the four prepregs B. place the stainless steel plate 1.5mm put it between 15 sets hot ^{plates, 200 ℃, 20kgf / cm 2} , 30mm
Laminate molding was performed for 2 hours under a vacuum of not more than Hg to obtain a double-sided copper-clad laminate C. Holes with a hole diameter of 0.5 mm are drilled at the four corners with an NC drill machine.
The laminate was laminated at a temperature of 0 ° C. to obtain a copper-clad laminate D. On the other hand, a resin obtained by dissolving polyvinyl alcohol in water
The solution was applied to one side of a μm aluminum foil and dried at 110 ° C. for 20 minutes to prepare a backup sheet E having a coating film having a thickness of 20 μm.

The film was exposed and developed so as to have a hole diameter of 0.5 mm at the peripheral and central six corners of the etching film stuck on both sides of the copper-clad laminate D, and the copper foil was removed by etching. Target mark (Fig. 1
(1)). Place the backup sheet E on this back,
The target mark is read with a CCD camera, 900 holes with a diameter of 100 μm from the top of the film are 900 directly within a 50 mm square.
Shot irradiation was performed to open 70 block through holes (Fig. 1
(2)). In this case, the maximum value of the length of the burr of the copper foil was 20 μm on the front surface and 24 μm on the back surface. The lower backup sheet is removed, plasma processing is performed while the etching film is left as it is, and burrs on the front and back are dissolved and removed to almost 0 by spraying a high-speed SUEP solution (FIG. 1).
(3)) After dissolving and removing the etching film and removing the nickel alloy treatment on the surface layer with a chemical solution, copper plating is applied to 15 μm (FIG. 1 (4)), and a circuit (line / space = 70/70 μm) is formed by an existing method. (FIG. 1 (5)), pads for solder balls, etc. are formed, covered with a plating resist except for at least the semiconductor chip portion, the bonding pad portions, and the solder ball pad portions, and plated with nickel and gold. It was created. Table 1 shows the evaluation results of the printed wiring board.

Example 2 Epoxy resin (trade name: Epicoat 1001, Yuka Shell Epoxy Co., Ltd.) 300 parts, and epoxy resin (trade name: ESC
N220F, manufactured by Sumitomo Chemical Co., Ltd.) 700 parts, dicyandiamide
35 parts, 1 part of 2-ethyl-4-methylimidazole was dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide,
Varnish F was obtained by uniformly stirring and mixing. This is 100μm thick
Impregnated in glass woven cloth, dried, gelled for 150 seconds, prepreg G with a glass cloth content of 48% by weight, impregnated in glass cloth with a thickness of 50 μm, dried and gelled for 170 seconds, glass cloth Prepreg H having a content of 31% by weight was prepared.

Using one piece of this prepreg G, place a general 12 μm electrolytic copper foil on the upper and lower sides, 190 ° C., 20 kgf / cm ² , 30 mmHg
To form a double-sided copper-clad laminate I. At the same time as forming a circuit on the front and back of this board, leaving a copper foil with a diameter of 0.5 mm at the four corners, creating a target mark, applying black copper oxide treatment, placing one of the prepregs H above and below, Then, a 5 μm-thick electrolytic copper foil with a 35 μm copper foil carrier was arranged in the same manner and laminated and formed in the same manner to form a four-layer multilayer board. 35
After removing the μm copper foil carrier, the surface of the copper foil is subjected to CZ treatment (MEC Corporation), and a 20 μm liquid etching resist is applied thereon and dried (FIG. 2 (1)), and the resist on the target mark of the inner layer is removed. Exposure, development, and removal, the copper foil in this portion is removed by etching, and then a backup sheet E is placed below the plate (FIG. 2 (2)). The target mark (o) was read with a CCD camera, and two shots were irradiated from above the resist with a carbon dioxide laser output of 10 mJ and two shots of 15 mJ to make through holes. The maximum value of copper foil burr is 4 μm on the front and
It was 8 μm.

Further, at an output of 12 mJ of a carbon dioxide laser,
Via irradiation was performed by shot irradiation. While leaving the liquid etching film as it is, only the back-up sheet on the back side was removed (FIG. 2 (3)), and the burr of the copper foil generated on the inner and outer layers was dissolved and removed by SUEP until it became almost 0 (FIG. )) And then removing the liquid etching resist on the front and back layers (FIG. 3).
(5)) Then, a treatment is performed with an aqueous solution of potassium permanganate, copper plating of 15 μm is performed through a normal process (FIG. 3 (6)), and a pattern of line / space = 50/50 μm is created. It was a printed wiring board. Table 1 shows the evaluation results.
Shown in

Comparative Example 1 A double-sided copper-clad board similar to that of Example 1 was prepared using a general electrolytic copper foil, and the surface of the copper foil was directly irradiated with a carbon dioxide gas laser under the same conditions as in Example 1 using this. However, there was no hole.

Comparative Example 2 2,000 parts of an epoxy resin (trade name: Epicoat 5045), 70 parts of dicyandiamide, and 2 parts of 2-ethylimidazole were dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide. Was added and mixed with stirring to obtain a varnish. This is thickness 100
Impregnated into glass woven cloth of μm, dried and gelled for 140 seconds (at 170 ° C), prepreg J with glass content of 52% by weight, 180 seconds between gelation, glass content of 50μm thick glass cloth 35% by weight of prepreg K was obtained. This prepreg J
Using two sheets, put a general 12μm electrolytic copper foil on both sides, 18
Laminate molding was performed at 0 ° C., 20 kgf / cm ² , and a vacuum of 30 mmHg or less for 2 hours to obtain a double-sided copper-clad laminate L. Circuits are formed on both sides of this laminate L, and after black copper oxide treatment, prepreg K
Was placed, and a general 12 μm copper foil was placed on the outside thereof, and laminated and formed in the same manner. Using this, a through hole was similarly formed by a mechanical drill. Even if the carbon dioxide laser was directly irradiated, the beam was reflected and no via hole was formed. Although the copper plating was performed without performing the SUEP treatment, a part of the burr at the entrance grew and closed the hole, and there was a portion where the copper plating did not adhere. Using this, a printed wiring board was formed in the same manner as in Experimental Example 2. Table 1 shows the evaluation results.

Comparative Example 3 In Example 2, a double-sided copper-clad board I (FIG. 4 (1)) was used, and the copper foil at a portion to be a through hole in the inner layer was formed with a hole diameter of 100 μm.
After etching and removing the upper and lower copper foils to form a circuit, the copper foil surface is treated with black copper oxide, prepreg H is placed on the outside, and a general 12μm electrolytic copper foil is placed on the outside. Similarly, a four-layer plate was formed by lamination molding. Using this multilayer board, a hole diameter of 100μ
900 holes were formed in the copper foil by etching. Similarly, 900 holes having a hole diameter of 100 μm were formed at the same position on the back surface (FIG. 4B). 70 blocks of 900 patterns per pattern, total 63,00
The 0 hole was subjected to four shots from the surface with a carbon dioxide laser at an output of 15 mJ to form a through hole (FIG. 4 (3)). Thereafter, in the same manner as in Comparative Example 2, a desmear treatment was performed once and a copper plating was performed at 15 μm without performing the SUEP treatment (FIG. 4).
(4)) A circuit was formed on the front and back, and a printed wiring board was prepared in the same manner. Table 1 shows the evaluation results.

Table 1 Item Practical example Comparative example 1 2 2 3 Gap between front and back land copper foil (μm) 0 0 0 22-0 0 36 Hole position deviation (μm) between inner layer copper foil and hole wall ) Glass transition temperature (℃) 235 160 139 160 Through-hole heat cycle test (%) 100 cycles 1.1 1.3 1.6 3.9 300 cycles 1.3 1.7 1.8 6.5 500 cycles 1.6 1.9 2.6 29.9 Pattern breaks and 0/200 0/200 55 / 200 52/200 short, the number drilling time (min) 19 14 630 over migration resistance (HAST) (Omega) normal 5x10 ¹¹ over 1x10 ¹¹ over ^{200hrs. 7x10 8 <10 8 500hrs} . 6x10 8 over 700hrs. 4x10 ⁸ 1000hrs. 2x10 ⁸

<Measurement method> 1) Clearance between front and back holes The hole with a hole diameter of 100 or 150 μm (mechanical drill) is 900 holes /
70 blocks (63,000 holes total) were prepared. The time required for drilling 63,000 holes in one copper clad plate using a carbon dioxide laser and a mechanical drill, the gap between the copper foil for front and back lands and the hole, and the gap between the inner layer copper foil and the hole wall were measured. The maximum value was shown. 2) Glass transition temperature Measured by the DMA method. 3) Through hole heat cycle test Create a land diameter of 250 μm for each through hole hole, connect 900 holes alternately front and back, one cycle: 260 ° C, solder, immersion 30 seconds → room temperature, 5 minutes, up to 500 cycles The maximum value of the rate of change of the resistance value was shown. 4) Migration resistance (HAST) 50 through holes of 100μm or 150μm (mechanical drilling) copper plated through holes are connected one by one alternately on both sides, and two sets of these are parallel with a hole wall of 150μm. Make a total of 100 sets, 130 ℃, 85% R
After processing at H, 1.8 VDC for a predetermined time, the samples were taken out and the insulation resistance between through holes arranged in parallel was measured. 5) Circuit pattern cut and sheet A board without holes was prepared in the examples and comparative examples, and a comb pattern of line / space = 50/50 μm was prepared. Then, 200 patterns after etching with a magnifying glass were visually observed. The total number of cut patterns and sheets was shown in the molecule.

[0041]

According to the present invention, an etching film or a liquid etching solder resist is formed on a copper-clad plate which has been subjected to a surface treatment capable of piercing by directly irradiating a carbon dioxide laser on the copper foil to form a target mark. After etching and removing the copper foil from the portion, the target mark is read by a CCD camera and directly irradiated from the film or resist with carbon dioxide laser energy sufficient to remove the copper foil, and the through holes and / or blind vias are exposed. By forming the holes, it is possible to prevent the residue of the copper foil, glass fiber, resin, and the like scattered upward at the time of drilling from dropping and attaching. After that, while the film or the resist is still attached, the copper foil burrs generated in the holes are dissolved and removed with a chemical solution, and then the film or the resist is removed and then plated with copper, so that the holes in the subsequent copper plating are formed. There is no protrusion at the portion, and a material having excellent hole reliability can be obtained. Further, by using a copper foil having a thickness of 2 to 7 μm, preferably 3 to 5 μm, a fine pattern can be formed in the subsequent pattern formation of the copper plating, and a high-density pattern with no short circuit or pattern breakage can be formed. A printed wiring board can be obtained. Further, the hole diameter is 80 ~
Forming the through-holes and / or blind via holes of 180 μm with a carbon dioxide gas laser is much faster than excimer lasers, YAG lasers, and mechanical drilling, and can greatly improve productivity.

[Brief description of the drawings]

FIG. 1 shows the removal of the film portion at the target mark of the double-sided copper-clad laminate with an etching film of Example 1.
(1) After etching and removing the copper foil at the target mark, read the target mark with a CCD camera and drill through holes from the etching film with a carbon dioxide laser.
FIG. 2 (2) is a process diagram of etching removal of copper foil burrs by SUEP (3), copper plating (4), and pattern formation (5).

[FIG. 2] A four-layer plate with a liquid etching solder resist of Example 2 (1). After removing the copper foil on the target mark formed on the inner layer by etching, the target mark is read by a CCD camera (2). FIG. 7 is a process chart until a through hole and a blind via hole are drilled (3).

[FIG. 3] A copper foil burr is etched by SUEP while leaving the liquid etching solder resist of Example 2 as it is.
FIG. 4D is a process diagram of performing copper plating (5).

FIG. 4 is a process diagram of drilling and copper plating of a double-sided copper-clad multilayer board of Comparative Example 3 with a carbon dioxide gas laser (without SUEP).

[Explanation of symbols]

a Etching film adhered to the front and back of the copper clad laminate b Copper foil treated with nickel alloy c Location where the etching film was removed d CCD camera e Target mark where the copper foil was removed by etching f Through hole with carbon dioxide gas laser g Scattered processing residue h Surface copper foil burr generated i SUEP treated surface copper burr j SUEP treated through hole k Copper plated through hole l Through hole copper plating m Surface layer pattern n Liquid etching solder resist o Target mark formed on inner layer p Inner layer pattern q Copper foil removed point r CZ treated surface copper foil s Polyvinyl alcohol resin layer t Aluminum foil u Blind via hole drilled by carbon dioxide gas laser v Blind via hole generated Part of copper foil burr w Inner layer copper burr generated x SUEP treated inner layer copper burr part y Blind via hole plated with copper z Outer layer portion removed by etching for drilling through hole a Inner layer portion removed by etching for drilling through hole β Inner layer copper foil portion with displacement γ No copper plated SUEP treatment Through hole

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 3/00 H01S 3/00 B H05K 3/24 H05K 3/24 A 3/26 3/26 B // B23K 101: 42 B23K 101: 42 F term (reference) 4E068 AF01 AF02 CA02 DA11 DB01 5E343 AA15 AA17 BB14 BB16 BB24 BB67 BB71 CC22 CC32 DD32 EE36 EE38 GG20 5F072 AA05 YY06

Claims (4)

[Claims] 1. An etching film or a liquid etching solder resist layer is disposed on a copper clad board, and after removing a film or a resist layer at a target mark location, a copper foil at the location is etched away to form a target mark. Alternatively, the target mark formed on the inner layer plate is exposed, the position is determined by reading the target mark with a CCD camera, and a sufficient amount of carbon dioxide laser energy is applied to directly remove the copper foil from the film or resist. Forming a through hole and / or a blind via hole, and then removing a copper foil burr remaining in the hole portion by etching with a chemical solution, and then removing a surface film or a resist, thereby forming a hole by a carbon dioxide gas laser. Method. 2. The method according to claim 1, wherein the copper foil of the copper-clad plate is surface-treated by nickel treatment, nickel alloy treatment, metal oxide treatment or chemical treatment. 3. The method for forming holes according to claim 1, wherein the output of the carbon dioxide laser is an output selected from 10 to 60 mJ. 4. The method according to claim 1, wherein the copper foil of the copper clad board has a thickness of 2 to 7 μm.