JP2001308493A - Method for forming hole by carbonic acid gas laser and method for posttreating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a hole by a carbonic acid gas laser suitable for manufacturing a high-density printed circuit board, and a method for posttreating after the hole is formed. SOLUTION: A method for forming a through hole and/or a blind via hole comprises the steps of mechanically cutting and exposing a surface layer copper foil on a target mark formed on an inner layer board of a multilayer copper-clad board, reading the mark by a CCD camera, directly radiating the carbonic acid gas laser of a high output suitably selected by 10 to 60 mJ from above a hole perforating auxiliary layer formed on a surface of the surface layer copper foil, and thereby removing the outer layer and the inner layer copper foil. The method for posttreating after the hole is formed comprises the steps of removing a burr generated at front and rear surfaces of the copper foil and the inner layer of the copper foil by etching and simultaneously partly melting to remove the copper foil of the surface layer in a thickness direction. Thus, the through hole and/or the blind via hole can be perforated directly by the carbonic acid gas laser so as not to generate a hole forming fault even when the inner layer board is contracted. The high-density printed circuit board can be obtained.

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 multilayer copper-clad board by a novel carbon dioxide laser, and a method for post-treating a copper foil burr generated in the hole. . A printed wiring board using a multilayer copper-clad board in which small-diameter holes are formed by the method of the present invention is a high-density small-sized printed wiring board having small-diameter holes and a fine pattern. Suitable for use in etc.

[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. According to this method, only a blind via hole can be formed, and a through hole is separately formed by mechanical drilling or the like, so that the number of steps is large and work efficiency is poor. As the through-hole forming method, holes of the same size were previously made in a predetermined method using a negative film in the front and back copper foils, and the same holes were formed in the inner layer copper foil by etching in advance. There is a method in which an object is placed and a hole is formed through the front and back sides with a carbon dioxide laser. However, in the case of this method, a gap is generated between the hole and the land above and below the hole, and the displacement of the inner layer copper foil,
There were drawbacks such as poor connection and inability to form front and back lands. Also, in order to be able to see the target mark formed on the inner layer, an etching film is attached to the surface of the multilayer copper-clad board, exposed, the film on the target mark is developed and removed, and the surface layer is etched. In addition, a step of removing the copper foil and then dissolving and removing the etching film was required, which was inferior in workability.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a hole in a multilayer copper-clad board and a post-treatment method after the formation of the hole, which solves the above problems.

[0004]

According to the present invention, a target formed on an inner layer plate of a multilayer copper-clad board before a carbon dioxide laser is directly irradiated on a copper foil to form a through hole and / or a blind via hole. After mechanically scraping and removing the copper foil on the surface of the mark, the position is determined by reading the target mark with a CCD camera, and sufficient to remove the copper foil from the drilling auxiliary layer formed on the surface of the surface copper foil. A hole forming method using a carbon dioxide gas laser, wherein a through-hole and / or a blind via hole is formed by directly irradiating carbon dioxide laser energy. The drilling assisting layer is provided to enable drilling of the copper foil by direct irradiation of a carbon dioxide gas laser. The hole forming method of the present invention is excellent in workability and automatically corrects a hole position shift due to shrinkage of the inner layer plate, so that there is no defect. Thereafter, the copper foil burrs generated in the holes are removed by etching with a chemical solution, and at the same time, a part of the surface copper foil is dissolved and removed, and a high-density printed wiring board is formed using the same.

[0005] The copper foil surface auxiliary layer is not particularly limited, and may be any as long as it can be drilled by directly irradiating a carbon dioxide gas laser. Preferably, nickel treatment, nickel alloy treatment, metal oxide treatment, chemical treatment, one or more of metal compound powder, metal powder, or carbon powder having a melting point of 900 ° C. or more and a binding energy of 300 kJ / mol or more Can be used in a water-soluble resin.

The multilayer copper-clad board after the formation of the holes is plated up with copper plating, circuits are formed on the front and back, and a printed wiring board is formed by a standard method. In order to make the front and back circuits fine, it is preferable to use copper foil of the front and back layers with a thickness of 2 to 7 μm.In this case, there is no occurrence of defects such as shorts and pattern breaks, and high density printing Wiring boards can be created. According to the method of the present invention, the processing speed is remarkably faster than when drilling, the productivity is good, and the economy is excellent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in a direct drilling process for a multilayer copper-clad board by a carbon dioxide gas laser, an auxiliary drilling layer is formed on the surface copper foil of the multilayer copper-clad board, When drilling through holes and / or blind via holes by directly irradiating a gas laser, after removing the outer layer copper foil on the target mark for drilling formed in the inner layer by machining, read the target mark with a CCD camera ,
This is a hole forming method for removing a copper foil, a glass fiber, and a resin by directly irradiating a carbon dioxide gas laser beam having sufficient energy for drilling a copper foil from above the auxiliary layer. Thereafter, the copper foil burrs generated in the holes are dissolved and removed with a chemical solution, and at the same time, a part of the surface copper foil is removed by etching with a chemical solution, and then a printed wiring board is formed by a generally known method.

In the present invention, there is no particular limitation on the auxiliary layer on the surface of the multilayer copper-clad board which can be perforated by irradiating the carbon dioxide gas laser directly onto the copper foil.
Nickel alloy treatment, metal oxide treatment, chemical treatment, melting point 900
C. or more, and a resin composition layer in which one or more of metal compound powder, metal powder or carbon powder having a binding energy of 300 kJ / mol or more is blended in an amount of preferably 3 to 97% by volume based on the water-soluble resin. No.

The hole-forming auxiliary layer provided on the surface copper foil includes
There is no particular limitation, as long as it can make holes in the copper foil by direct irradiation of a carbon dioxide gas laser. For example, a layer of zinc, cobalt, nickel, or an alloy thereof may be provided on a copper foil. The most preferable layers include a nickel layer and a nickel alloy layer.
Nickel alloys include nickel and cobalt, iron, copper,
An alloy such as zinc is exemplified. These layers are usually formed by plating, vapor deposition, or the like. Further, a metal oxide layer such as black copper oxide may be provided on the copper foil. Furthermore, treatment of the copper foil surface with a chemical solution, such as CZ treatment (Mec), can also be used.

In the present invention, the auxiliary hole forming layer formed on the copper foil surface has a melting point of 900 ° C. or more and a binding energy of 300 kJ / mol.
As the above metal compounds, generally known compounds can be used. Specifically, oxides include copper oxides such as copper oxide; titanias such as titanium oxide; magnesias such as magnesium oxide; nickel oxides such as nickel oxide; manganese oxides such as manganese dioxide. Zinc oxides such as zinc oxide; cobalt oxides such as cobalt oxide;
Tin oxides such as tin oxide; tungsten oxides such as tungsten oxide; silicon dioxide, aluminum oxide, and rare earth oxides. Examples of the non-oxide include boron nitride, silicon nitride, titanium nitride, aluminum nitride, barium sulfate, aluminum hydroxide, and magnesium hydroxide. In addition, various glass powders which are a mixture of metal oxides may be used. Carbon powder can also be used. Furthermore,
Commonly known metal powders such as silver, tin, iron, nickel, tin, and copper are exemplified. These can be used alone or in combination of two or more. The amount used is 3-97% by volume of the resin,
Preferably 5 to 95% by volume, the particle size is 5 μm or less,
Preferably, 1 μm or less is used.

[0011] Since the molecules are dissociated or melted and scattered by the irradiation of the carbon dioxide laser, the metal adheres to the hole walls,
Use a semiconductor chip that does not affect the adhesion to the hole wall. Since Na, K, Cl ions and the like particularly adversely affect the reliability of the semiconductor, those containing these components are not preferred.

[0012] The resin of the auxiliary layer is not particularly limited, and generally known resins can be used. However, when peeled after drilling, the adhesive may remain on the surface of the copper foil, and a water-soluble resin is preferred from the viewpoint of subsequent dissolution and removal. Specifically, water-soluble polyester resin, polyether resin,
Polyvinyl alcohol resin, starch and the like. In this case, various additives can be added.

The method for preparing a resin composition comprising a metal compound or the like and a resin or the method for forming a sheet is not particularly limited. A method of kneading at high temperature with no solvent in a kneader or the like, extruding and adhering to a thermoplastic film in a sheet form, dissolving the acidic resin in a solvent, adding the above powder, uniformly stirring and mixing the mixed paint with copper Coating on a foil surface, drying to form a coating film, applying a coating on a thermoplastic film and drying to form a resin sheet with a film, and placing it on the copper foil surface or thermocompression bonding with a laminate For example, a method of forming a drilling auxiliary layer can be used. The thickness is not particularly limited,
Preferably, the thickness of the coating is 30 to 100 μm when applied, and the total thickness is 30 to 200 μm when applied on a thermoplastic film.

When laminating on the copper foil surface under heating and pressure, the coating resin layer is directed to the copper foil surface, and the temperature is generally 40 to 150 ° C., preferably 60 to 120 ° C., and the linear pressure is 1 ~
Lamination is performed at a pressure of 20 kgf, preferably 2 to 10 kgf, and the resin is melted and brought into close contact with the copper foil surface. The lamination temperature is not less than the melting point of the resin to be used, and also depends on the linear pressure and the laminating speed. In general, lamination is performed at a temperature higher by 5 to 20 ° C. than the melting point of the resin.

The surface copper foil of the multilayer board is preferably 3 to 12 μm
Use electrolytic copper foil. Drill a hole with a carbon dioxide gas laser, and then copper-plate as it is and fill the inside of the hole with copper plating of 80% by volume or more, or dissolve and remove the copper foil burrs generated in the hole with a chemical solution and simultaneously remove the surface copper foil in the thickness direction Then, copper is plated by dissolving and removing a portion to a thickness of 2 to 7 μm. As the inner layer copper foil, an electrolytic copper foil having a thickness of 9 to 35 μm is generally used. Of course, rolled copper foil can also be used.

As the multilayer copper-clad board used in the present invention, those reinforced with a base material, those with a film base, and those with a single resin without a reinforcing base can be used. However, those using a glass cloth as a base material are preferable from the viewpoint of dimensional shrinkage and the like. As the base material of the multilayer 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 for a 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, JP-B-41-1928 and JP-B-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. Particularly for carbon dioxide laser drilling, 10 to 80% by weight in the resin composition to homogenize the shape of the hole, preferably 20%
Add ~ 70% by weight. The kind of the insulating inorganic filler is not particularly limited. Specifically, talc, calcined talc, aluminum hydroxide, magnesium hydroxide, kaolin, alumina, wollastonite, synthetic mica, and the like can be mentioned, and one or more kinds are mixed.

The thermosetting resin composition of the present invention can be cured by heating itself, but has a low curing rate and is inferior in workability, economy and the like. 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, a surface copper foil on a target mark (also referred to as an alignment mark) formed in an inner layer is ground and removed by machining. This machine is only required to be capable of grinding copper foil, and for example, a router, a spot facing device, or the like can be used. After grinding removal, read the target mark as it is with a CCD camera, or pour a resin layer into the ground surface to increase the transparency, read, and determine the position of the hole to be drilled. After the reading, a carbon dioxide gas laser having a power of preferably 10 to 60 mJ is directly irradiated from above the multilayer copper-clad plate on which the auxiliary layer has been formed to form a hole having a hole diameter of 80 to 180 μm. 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. When drilling through-holes and / or blind via holes, the same energy is applied from the beginning to the end to make holes.
Any method may be used, such as lowering and drilling.

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 burrs of the copper foil generated in the holes is not particularly limited. For example, JP-A-02-22887, JP-A-02-22896, JP-A-02-22896
-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 speed is generally 0.02 to 1.0 μm / sec. 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. .

On the back surface of the copper-clad plate, it is possible to simply arrange a metal plate to prevent the laser machine table from being damaged by the laser when the holes penetrate. The resin layer to which at least a part is adhered is arranged by being adhered to the copper foil on the back surface of the copper-clad multilayer board, and the metal plate is peeled off after drilling through holes.

In most cases, a resin layer 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 desmear treatment before etching. However, if the liquid does not reach the inside of the small-diameter hole, the removal of the resin layer remaining on the surface of the copper foil of the inner layer remains. May occur, 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 front and back copper foil burrs are removed by etching. In the case of a blind via hole, it is preferable to remove the 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 processing, generally known processing can be used,
For example, plasma treatment, low-pressure ultraviolet treatment, and the like can be given.
The plasma partially excites molecules with a high-frequency power supply,
Use ionized low-temperature plasma. This is because high-speed processing using ion bombardment and gentle processing using radical species are generally used, and reactive gases,
An inert gas is used. 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, but the inside of the hole can be partially filled with copper plating, preferably 80% or more. In drilling, an excimer laser, a YAG laser or the like can be used together. Also, a mechanical drill can 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 1 600 parts of 2,2-bis (4-cyanatophenyl) propane, 1,
300 parts of 4-dicyanatobenzene and 100 parts of bis (4-maleimidophenyl) ether were melted at 150 ° C., and reacted with stirring for 4 hours to obtain a prepolymer. This was dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide. Bisphenol A type epoxy resin (trade name: Epicoat 1001, Yuka Shell Epoxy Co., Ltd.) 80
0 parts, Cresol novolak type epoxy resin (trade name: ES
200 parts of CN-220F (manufactured by Sumitomo Chemical Co., Ltd.) were added and uniformly dissolved and mixed. Further add 0.4 part of zinc octylate as a catalyst, dissolve and mix, add 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 add The varnish A was obtained by stirring and mixing.
This varnish was impregnated into a glass woven fabric having a thickness of 100 μm and dried at 150 ° C. to prepare a prepreg B having a gel time (at 170 ° C.) of 110 seconds and a glass cloth content of 50% by weight. Also, thickness 50
A varnish A was impregnated into a μm glass woven fabric and dried to prepare a prepreg C having a gelling time of 150 seconds and a glass cloth content of 31% by weight. A general electrolytic copper foil having a thickness of 12 μm was placed above and below the ^two prepregs B and laminated and formed at 200 ° C., 20 kgf / cm ² , and a vacuum of 30 mmHg or less to prepare a double-sided copper-clad laminate D.
A copper foil with a diameter of 0.5 mm is left in each of the four corners as a target mark. At the same time, a circuit is formed entirely, black copper oxide treatment is performed, and one prepreg C is placed on each of the front and back surfaces. An electrolytic copper foil with a nickel alloy layer (also called Japan Energy Co., Ltd., Y treatment, LD foil) is placed on the surface of the foil, and a 1.5 mm thick stainless steel plate is placed outside the foil. 15 sets between hot plates, 200 ℃, 20kgf
/ cm ^2, 30 mmHg for 2 hours laminate molded under the following vacuum to give a double-sided copper-clad multilayer board E. On the other hand, a resin obtained by dissolving polyvinyl alcohol in water was applied to one surface of an aluminum foil having a thickness of 50 μm, and dried at 110 ° C. for 20 minutes to prepare a backup sheet F having a coating film having a thickness of 20 μm.

A copper foil of the surface layer on the target mark formed on the inner layer of the copper-clad multilayer board E is spotted with a spotting device with a diameter of 3 m.
It was removed by grinding in the range of m. The backup sheet F is placed on the back side of the multilayer board E, the target mark of the inner layer is read by the CCD camera to determine the position, and 900 holes of 100 μm in diameter are directly formed in the 50 mm square from the surface copper foil of the copper-clad multilayer board E. CO2 laser, pulse oscillation, 3 shots at 10 mJ output, 2 at 20 mJ
Shot irradiation was performed to make a total of 63,000 through holes in 70 blocks. Also, irradiate 3 shots at 15 mJ and make the hole diameter 100μ
m blind via holes were drilled.

The lower backup sheet F is removed, and S
The UEP solution is sprayed at a high speed to dissolve and remove the burrs on the front and back surfaces to remove them almost completely, and to reduce the thickness of the surface copper foil to 3 μm.
Until dissolved. Copper plating is adhered by 15μm by the standard method, and the circuit (line / space = 50 / 50μ)
m), pads for solder balls and the like were formed, and except for at least the semiconductor chip portion, the bonding pad portions, and the solder ball pad portions, they were covered with a plating resist and plated with nickel and gold to produce a printed wiring board. Table 1 shows the evaluation results of the printed wiring board.

Example 2 300 parts of epoxy resin (trade name: Epicoat 1001, manufactured by Yuka Shell Epoxy Co., Ltd.) 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 G was obtained by uniformly stirring and mixing. This is 100μm thick
Impregnated in glass woven cloth, dried, gelled for 150 seconds, prepreg H 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 I having a content of 31% by weight was prepared.

Using one piece of this prepreg H, 12 μm
m electrolytic copper foil was placed and laminated and formed at 190 ° C., 20 kgf / cm ² and 30 mmHg to obtain a double-sided copper-clad laminate J. 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 above prepregs I above and below, Was placed with a 5 μm electrolytic copper foil having a 35 μm carrier copper foil, and laminated and formed in the same manner to form a four-layer multilayer board K. After removing the carrier copper foil, this surface layer is subjected to CZ treatment, and the surface layer copper foil on the target mark formed on the inner layer copper foil of the multilayer board is ground and removed with a router within a range of 3 mm in diameter, and ground and removed with a fast-curing resin. The transparent surface was covered with a resin to increase the transparency. Laminate backup sheet F on the back side at 100 ℃, 5kgf, read target mark of inner layer with CCD camera, 2 shots of CO2 laser from surface of multilayer board with 20mJ output, 25mJ
Two shots were irradiated to open through holes.

Further, three shots were irradiated at an output of 22 mJ from a carbon dioxide laser to form a blind via hole. After removing the back-up sheet F on the back side and performing desmear treatment with a potassium permanganate solution, the whole is plated with copper and the inside of the hole is filled with 92% by volume.
m. A pattern of line / space = 50/50 μm was prepared by a standard method, and a printed wiring board was prepared in the same manner as in Example 1. Table 1 shows the evaluation results.

Example 3 In the step of preparing the multilayer copper-clad board of Example 1, a general copper foil (Japan Energy, JTC-
A laminate L was obtained in the same manner except that the LP foil was used. The surface copper foil on the inner layer target mark was removed with a counterbore device. On the other hand, a water-soluble polyester resin was dissolved in water, and copper oxide powder (average particle size: 3 μm) was added thereto so as to be 40% by volume based on the water-soluble polyester resin.
Avoid this on the target mark on the copper foil, thickness 40μ
m, and dried at 110 ° C to form a coating film.
The backup sheet F was placed on the back. The target mark was read by a CCD camera to determine the position of the through-hole, and three shots were radiated from the surface at 30 mJ, and then three shots were radiated at 25 mJ to drill the through-hole. Blind via holes were made by irradiating three shots at 23 mJ. This was put into a plasma processing apparatus, processed, and then subjected to SUEP treatment from the front and back to remove copper foil burrs and to melt the surface copper foil to a thickness of 4 μm. After that, a printed wiring board was formed in the same manner as in Example 1.
Table 1 shows the evaluation results.

COMPARATIVE EXAMPLE 1 A hole was formed with a carbon dioxide laser under the same conditions as in Example 3 without any adhesion to the surface of the double-sided copper-clad multilayer board L of Example 3, but no holes were formed. .

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. I got This is impregnated with a 100 μm thick glass woven fabric, dried, and gelled.
140 seconds (at 170 ° C), prepreg with a glass content of 52% by weight
N, using a 50μm thick glass cloth, gel time 180
In seconds, a prepreg O having a glass content of 35% by weight was obtained. Using two sheets of this prepreg N, put a general 12μm electrolytic copper foil on both sides, 180 ° C., 20 kgf / cm ² , laminated molding under vacuum of 30 mmHg or less for 2 hours to obtain a double-sided copper-clad laminate P . After forming a circuit on both sides of this laminated board P and performing black copper oxide treatment, one prepreg O was placed on each side, and a general copper foil of 12 μm was arranged outside the same, as in Example 2. Under the following conditions. Using this, a through hole was formed by drilling with a mechanical drill. Even when the carbon dioxide laser was directly irradiated on the copper foil surface, no blind via hole was formed. Copper plating was performed without performing the SUEP treatment, and a printed wiring board was obtained in the same manner as in Example 1. Table 1 shows the evaluation results.

COMPARATIVE EXAMPLE 3 In Example 2, the upper and lower copper foils were removed by etching using a double-sided copper-clad plate J so as to have a hole diameter of 100 μm at a portion to be a through hole in the inner layer, and a circuit was formed. A black copper oxide treatment is applied to the copper foil surface, a prepreg I is placed outside the copper foil treatment, and a general electrolytic copper foil of 12 μm is placed outside the prepreg I, and laminated and formed under the same conditions as in Example 2 to form a four-layer plate. did. Using this multilayer copper-clad board, a hole diameter of 100
900 μm holes were drilled by etching a copper foil. Similarly, on the back surface, 900 holes having a hole diameter of 100 μm were formed in the same position by etching the copper foil. Using a carbon dioxide laser from the surface, a total of 63,000 holes, 70 blocks of 900 patterns,
Four shots were made at an output of 15 mJ, and through holes were made. After that, in the same manner as in Comparative Example 2, copper plating was performed without performing the SUEP treatment.
After applying 15 μm and forming circuits on both sides, a printed wiring board was prepared. Table 1 shows the evaluation results.

Comparative Example 4 In Example 3, a hole having a diameter of 0.5 mm was drilled at the original target mark without removing the surface copper foil on the inner target mark, and the hole was read by a CCD camera. Was drilled in the same manner as in Example 3, but due to dimensional shrinkage of the inner layer plate during lamination molding, a hole could not be formed at a predetermined position, displacement with the inner layer copper foil occurred, and 33% of defective parts occurred .

[0041] Table 1 Item implementation example comparisons Example 1 2 3 2 3 top- land copper foil with clearance (μm) 0 0 0 0 22 deviation of hole position of the inner layer (μm) 0 0 0 0 36 Glass Transition temperature (° C) 233 160 233 139 160 Through-hole heat cycle test (%) 100 cycles 1.2 1.3 1.3 1.6 3.9 350 cycles 1.5 1.8 1.6 2.3 10.3 Drilling time (min) 16 14 19 630 ー Migration resistance (HAST ) (Omega) normal 5x10 ¹¹ over over 1x10 ¹¹ over ^{200hrs. 7x10 8 <10 8 500hrs} . 6x10 8 over 700hrs. 4x10 ⁸ 1000hrs. 2x10 ⁸ pattern breakage and short (number) 0/200 0/200 0/200 55 / 200 52/200

<Measurement method> 1) The gap between the front and back holes, the gap between the inner layer copper foil and the hole wall The hole with a hole diameter of 100 or 150 μm (mechanical drill) is 900 holes /
70 blocks (63,000 holes total) were drilled using a carbon dioxide laser and a mechanical drill.
The time required to make a hole in the copper clad sheets, the gap between the copper foil for front and back lands and the hole, and the maximum value of the displacement of the inner layer copper foil are shown. 2) Glass transition temperature Measured by the DMA method. 3) Through hole heat cycle test Create a land with a diameter of 250μm in each through hole, connect 900 holes alternately front and back, one cycle is 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) Cut and short circuit pattern In each of the examples and comparative examples, a board without holes was made, and a comb-shaped pattern of line / space = 50/50 μm was made. Then, 200 patterns after etching with a magnifying glass were visually observed. And observed, and the total of the broken pattern and the short-circuited pattern was shown in the molecule.

[0043]

According to the present invention, the surface copper on the target mark formed on the inner layer of the multilayer copper-clad board in which the auxiliary layer which can be perforated by irradiating the carbon dioxide laser directly on the copper foil is formed on the surface of the copper foil. After mechanically cutting and removing the foil, the target mark is read from above with a CCD camera to determine the position, and a carbon dioxide laser with sufficient energy to remove the copper foil from the copper foil directly formed with the drilling auxiliary layer This is a hole forming method of forming a through hole and / or a blind via hole by irradiating a beam. ADVANTAGE OF THE INVENTION According to the method of this invention, since it is excellent in workability | operativity, since the dimensional correction with respect to the displacement of an inner layer is performed, there is no hole drilling defect and the thing excellent in hole reliability is obtained. Also, at the same time dissolving and removing copper foil burrs generated by drilling with a chemical solution, partially dissolving and removing the surface copper foil in the thickness direction, thickness 2 ~ 7μm,
When the thickness is preferably 3 to 5 μm, a fine pattern can be formed in the subsequent pattern formation of the copper-plated product, and a high-density printed wiring board free from shorts and pattern breaks can be obtained. According to the method of the present invention, since a through hole and / or a blind via hole having a hole diameter of 80 to 180 μm or less are formed by a carbon dioxide gas laser, the processing speed is remarkably higher than that of an excimer laser, a YAG laser, or a mechanical drilling. Performance can be greatly improved.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/46 H05K 3/46 S // B23K 101: 42 B23K 101: 42 F term (reference) 4E068 AA04 AF00 AJ04 CF00 CF03 DA11 5E317 AA24 BB01 CC53 CD01 CD27 CD32 GG16 5E346 AA02 AA12 AA15 AA29 AA32 AA42 AA43 AA60 CC04 CC05 CC09 CC10 CC32 CC55 EE13 FF01 FF02 FF07 FF14 GG15 GG16 H26 GG28H26

Claims (5)

[Claims] 1. A copper foil of a target mark surface layer formed on an inner layer plate of a multilayer copper clad board is mechanically irradiated before a carbon dioxide laser is directly irradiated on the copper foil to form a through hole and / or a blind via hole. After the target is cut and removed, the position is determined by reading the target mark using a CCD camera, and a carbon dioxide laser energy sufficient to directly remove the copper foil from the auxiliary drilling layer formed on the surface of the surface copper foil is applied. Forming a through hole and / or a blind via hole by using a carbon dioxide gas laser. 2. The hole formed by a carbon dioxide gas laser according to claim 1, wherein the hole-forming auxiliary layer formed on the surface copper foil of the multilayer copper-clad board is a nickel layer, a nickel alloy layer, a metal oxide treatment layer or a chemical treatment layer. Forming method. 3. The hole-forming auxiliary layer formed on the surface copper foil of the multilayer board has a melting point of 900 ° C. or more and a binding energy of 300 kJ / m 2.
2. A pore formation by a carbon dioxide laser according to claim 1, wherein the water-soluble resin composition layer is formed by mixing one or more kinds of metal compound powders, metal powders or carbon powders in an amount of 3 to 97% by volume with a water-soluble resin. Method. 4. The method according to claim 1, wherein the output of the carbon dioxide laser is 10 to 60 mJ. 5. The method according to claim 1, wherein after the hole is formed by the carbon dioxide laser, the generated copper foil burrs are dissolved and removed with a chemical solution, and at the same time, the surface copper foil is partially dissolved and removed in the thickness direction. 5. The post-treatment method for forming holes by using a carbon dioxide gas laser according to 3 or 4.