JP2000031622A - Method of forming through-hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a through-hole, which can make a hole with a small diameter with high reliability on the hole wall in the hole position at the surface or the rear at high speed, using a carbon dioxide laser. SOLUTION: This is a method of forming a through-hole or a via hole which bores a hole by applying a carbon dioxide gas laser at least, and arranging a paint film or a sheet of organic matter including metallic powder by 3-97 volume % on the surface of the copper foil of the copper-clad plate, and subjecting it to irradiation by a carbon dioxide laser with required pulses, in a method of forming a through-hole or a via hole in a copper-clad plate which has at least two or more layers of copper, by the pulse oscillation of a carbon dioxide laser, using energy selected from 20 to 60 mJ which is pulse sufficient to remove a copper foil by the carbon dioxide laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drilling a through hole or a via hole in a copper clad board having at least two copper layers instead of a mechanical drill. More specifically, the present invention relates to a method of forming a through hole or a via hole by arranging an auxiliary material on a copper foil surface without etching the surface copper foil in advance, and irradiating a high-output carbon dioxide laser from above. The printed wiring board using the copper-clad board obtained by the method of the present invention is mainly used for small semiconductor plastic packages.

[0002]

2. Description of the Related Art Hitherto, in high-density printed wiring boards used for semiconductor plastic packages and the like, through holes for through holes have been drilled. In recent years, the diameter of drills has become increasingly smaller, and the hole diameter has become smaller than 0.15 mm.When drilling such small holes, the drill diameter is small, so the drill will bend, break, and process at drilling. It has disadvantages such as slowness, and has problems in productivity, reliability, and the like. Using a negative film on the upper and lower copper foils in advance to make holes of the same size by a predetermined method, and trying to form a through hole that conducts up and down with a carbon dioxide gas laser, the position of the upper and lower holes is shifted. This has disadvantages such as difficulty in forming lands and an increase in the number of manufacturing steps. In addition, there is a drawback that processing cannot be performed even if a carbon dioxide gas laser is directly irradiated on a copper foil surface having a metallic luster. Also,
The circuit width and space of high-density printed wiring boards are becoming increasingly narrower, and lines / spaces of less than 100 μm / 100 μm have also been created. It was bad.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by arranging an auxiliary material on the surface of a copper foil and irradiating a high-output carbon dioxide laser from above to form a small-diameter hole. It is an object of the present invention to provide a method for forming a hole wall at high speed with high reliability. In addition, the generated burrs are removed by etching with a chemical solution, and part of the thickness of the surface copper foil is removed by etching in a planar manner.In the subsequent copper plating, the through hole reliability is excellent and the surface circuit is formed. Another object is to form a high-density circuit.

[0004]

That is, the present invention relates to a method for removing copper foil by using a carbon dioxide gas laser, which has a thickness of 20 to 60 mJ.
Irradiates the carbon dioxide laser by the pulse oscillation of the carbon dioxide laser using the energy selected from the / pulse,
In a method of forming a through-hole or a via hole by processing a copper foil of a copper-clad board having at least two copper layers, a metal powder is applied to a surface of the copper foil of the copper-clad board to be irradiated with a carbon dioxide gas laser. By arranging a coating film or a sheet made of an organic material containing 3 to 97% by volume of one or more kinds of the above components and forming through holes for through holes in the copper clad board, it is very efficient to use a large number of small diameter The inventor has found that a through hole or a via hole for a through hole can be formed and completed. afterwards,
By etching both surfaces of the copper foil two-dimensionally and etching away part of the thickness of the original copper foil, the copper foil burrs that overhang the hole at the same time are etched away, and the copper foil around the hole is removed. By forming plating holes for the remaining through holes or via holes, lands can be formed without displacing the copper foil positions of the upper and lower holes in the through holes,
The through hole can be formed without bending up and down, and
Because the surface copper foil is thin, in the circuit formation of the front and back copper foil obtained by plating up with subsequent metal plating,
A high-density printed wiring board can be produced without occurrence of a defect such as a short circuit or a broken pattern. Also, the processing speed is much faster than when drilling, the productivity is good, and the economy is excellent. After drilling through holes or via holes for through holes, the surface can be polished with a machine other than the method of etching with a chemical solution.However, from the viewpoint of dimensional stability, removal of burrs, creation of fine patterns, Etching is preferred. Further, the hole making method of the present invention can be applied to not only a double-sided board but also a multilayer board.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method of manufacturing a copper clad board having at least two copper layers by pulse oscillation of a carbon dioxide gas laser using energy selected from 20 to 60 mJ / pulse. This is a method of arranging an auxiliary material and irradiating a carbon dioxide gas laser on this to form a through hole for a through hole and a via hole in the copper clad board, and then etch the burrs of the copper foil generated in the hole with a chemical solution Simultaneously with the removal, a part of the surface of the copper foil is removed by etching to obtain a copper-clad board used for a high-density printed wiring board having a through hole for a through hole and a via hole.

The copper-clad board used in the present invention includes inorganic,
Organic substrate reinforced thermosetting resin copper-clad laminates, double-sided boards having copper foil on both sides of a film, and multilayer boards thereof. Also, a copper foil with a resin, a resin sheet, and a build-up multilayer board by applying a paint may be used. Above all, a glass cloth is used as a base material, a thermosetting resin composition is used as an insulating layer, a dye or a pigment is blended to make black, and an inorganic insulating filler is mixed at 10 to 60% by volume to be homogeneous. A double-sided copper-clad laminate and a multilayer board having the above configuration are preferably used.

As the substrate, generally known woven or nonwoven fabrics of inorganic or organic fibers can be used. As inorganic fibers,
E, A, C, L, M, S, D, N, C, quartz glass and the like can be mentioned, and these can be used alone or in combination. Examples of the organic fibers include wholly aromatic polyamides and liquid crystal polyesters. Further, a polyimide film or the like can be used as the base material.

As the resin of the thermosetting resin composition used in the present invention, generally known thermosetting resins are used. Specific examples include an epoxy resin, a polyfunctional cyanate ester resin, a polyfunctional maleimide-cyanate ester resin, a polyfunctional maleimide resin, and a polyphenylene ether resin containing an unsaturated group.
More than one type is used in combination. Heat resistance, moisture resistance,
A polyfunctional cyanate resin composition is preferred in terms of migration resistance, electrical properties after moisture absorption, and the like.

The polyfunctional cyanate compound which is the thermosetting resin component of the present invention is a compound having two or more cyanato groups in the molecule. To give a concrete example, 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-cyanatophenyl) 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 600 and having a triazine ring formed by trimerization of a cyanato group of these polyfunctional cyanate compounds is also used. This prepolymer is obtained by polymerizing the above-mentioned polyfunctional cyanate ester monomer using, for example, an acid such as a mineral acid or a Lewis acid; a base such as sodium alcoholate or a tertiary amine; a salt such as sodium carbonate as a catalyst. Is 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 group-containing silicone resin with an ephalohydrin, 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 thereof 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, fluoro rubber, natural rubber; polyethylene, polypropylene,
Polybutene, poly-4-methylpentene, polystyrene, AS resin, ABS resin, MBS resin, styrene-isoprene rubber, polyethylene-propylene copolymer,
-Fluorinated ethylene-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 appropriately used. In addition, other known organic fillers, dyes, pigments, thickeners, lubricants, defoamers, dispersants, leveling agents, photosensitizers, flame retardants, brighteners, polymerization inhibitors, thixotropic agents And various other additives are used in combination as needed. If necessary, the compound having a reactive group is appropriately blended with a curing agent and a catalyst.

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 and economic efficiency. Can be used. The amount used is 0.005 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the thermosetting resin.

In order to improve the hole shape by irradiation with a carbon dioxide gas laser, it is preferable to add various additives. As the inorganic filler, generally known inorganic fillers can be used. Specific examples include silicas such as natural silica, calcined silica, and amorphous silica; white carbon, titanium white, aerosil, clay, talc, wollastonite, natural mica, synthetic mica, kaolin, magnesia, alumina, pearlite, and the like. Can be The amount added is 10 to 60% by weight, preferably 15 to 50% by weight.

Preferably, a black dye or pigment is added to the resin so that the light is not dispersed by the irradiation of the carbon dioxide laser. As the types of dyes and pigments, generally known ones can be used. Particle size is 1μm for uniform dispersion
The following is preferred. The addition amount is preferably 0.1 to 10% by weight. Furthermore, a method of dyeing the surface of the fiber with black, a method of blending a black dye or the like into the organic fiber, and the like can also be used.

A generally known copper foil can be used as the outermost layer. Preferably, a copper foil, a copper alloy foil or the like having a thickness of 3 to 18 μm is used. The same applies to the inner layer copper foil.

The glass cloth substrate reinforced copper-clad laminate is first impregnated with a thermosetting resin composition and dried to form a B stage to prepare a prepreg. Although the glass content is not particularly limited, the resin is generally adhered so as to be 30 to 80% by weight. Next, a predetermined number of the prepregs are used, copper foils are arranged on the upper and lower sides, and laminated under heat and pressure to form a double-sided copper-clad laminate. Further, it is preferable to add an inorganic filler. In the cross section of the copper clad laminate, the resin and inorganic filler other than glass are uniformly dispersed, and the holes are uniformly formed when laser drilling is performed. Further, by blending a black pigment or a black dye, the laser beam does not disperse and the pore wall becomes more uniform.

As the metal powder to be used as a part of the auxiliary material on the copper foil surface of the copper clad plate or the multilayer plate at the hole forming position on the surface to be irradiated with the carbon dioxide gas laser, generally known metal powder can be used. Specifically, silver, aluminum, bismuth, cobalt, copper, iron, manganese, molybdenum, nickel, vanadium, antimony, silicon, tin, titanium,
A simple substance such as zinc, or one or a combination of two or more of these alloys is used. These are appropriately selected and used in consideration of the type of a solvent, an organic substance, and the like to be used. water,
Use a material that is stable in solvents, etc., does not generate heat and reacts when dissolved. The amount is 3 to 97% by volume, preferably 5 to 9%.
5% by volume. Usually, the average particle diameter is 5 μm or less, more preferably the particle diameter is 1 μm or less.

The organic material of the auxiliary material is not particularly limited, but those which do not peel or drop when kneaded and applied to the surface of the copper foil and dried or when formed into a sheet are selected. Preferably, a resin is used. In particular, a water-soluble resin, for example, a generally known resin such as polyvinyl alcohol, polyester, polyether, and starch is also used from the viewpoint of washing the environment or the copper foil surface after processing. Further, if necessary, the above-mentioned various resins, additives and the like can be appropriately selected and used.

The method for preparing a composition comprising a metal powder and an organic substance is not particularly limited. For example, a method of kneading at a high temperature without a solvent using a kneader or the like and extruding into a sheet form, or a method of dissolving a resin composition soluble in a solvent or water. Use, add the metal powder to this,
A method of uniformly stirring and mixing, applying a coating to the copper foil surface as a paint, drying to form a film, a method of directly spraying the copper foil surface with a spray, a method of applying and drying a film to form a sheet,
A generally known method, such as a method of impregnating an organic or inorganic substrate and drying to obtain a sheet containing the substrate, can be used. The thickness is not particularly limited, but is preferably 30 to 200 μm. Known films can be used as the film to be applied. For example, a film such as polyethylene phthalate is suitable. The thickness of the film is not particularly limited, but is preferably 25 to 200 μm.

A coating film or a sheet made of a resin composition containing metal powder is placed on the copper foil surface of the copper clad plate at the hole forming position on the surface to be irradiated with the carbon dioxide gas laser, and is squeezed to a target diameter. Drill holes by irradiating the output with a carbon dioxide laser. In the case of a sheet, it is preferable to use the sheet by laminating it on a copper-clad board at a temperature equal to or higher than the melting point of the resin from the viewpoint of the hole shape.

When a carbon dioxide laser is irradiated with an energy selected from an output of 20 to 60 mJ / pulse to form a through hole or a via hole, burrs are generated around the hole. Therefore, after the carbon dioxide laser irradiation, both surfaces of the copper foil are etched two-dimensionally, and the thickness of a part of the original metal foil is removed by etching, thereby simultaneously removing the burrs by etching. As a result, the obtained copper foil is suitable for forming a fine pattern, and a through hole for plating through holes or a via hole in which copper foil on both sides around a hole suitable for a high-density printed wiring board is formed. When drilling a via hole, a method in which the output is initially high and then the output is low may be used.

The method of etching and removing copper burrs generated in the holes according to the present invention is not particularly limited, and examples thereof include, for example, JP-A Nos. 02-22887, 02-22896, and 02-25089.
02-25090, 02-59337, 02-60189, 02-16
6789, same 03-25995, same 03-60183, same 03-94491, same
A method of dissolving and removing a metal surface with a chemical (referred to as a SUEP method) disclosed in JP-A-04-199592 and JP-A-04-263488 is preferable. Generally, the etching rate is 0.02-1.0 μ
Perform at m / s. Although it is possible to remove the burrs of the copper foil by mechanical polishing, when the copper-clad laminate is thin, there are problems such as a large dimensional change, and the burrs may not be completely removed.

The carbon dioxide laser is in the infrared wavelength range.
Wavelengths between 9.3 and 10.6 μm are commonly used. Output is 20 ~
60 mJ / pulse, preferably 22-55 mJ / pulse. The method of the present invention can be applied not only to the formation of the through hole but also to the method of forming the via hole by stopping the laser at the copper foil portion immediately below the copper clad laminate.

[0027]

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 bis (4-maleimidophenyl) methane at 150 ° C
To obtain a prepolymer. This was dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide. This is bisphenol A
Epoxy resin (trade name: Epicoat 1001, Yuka Shell Epoxy Co., Ltd.) 400 parts, Cresol novolak type epoxy resin (trade name: ESCN-220F, Sumitomo Chemical Co., Ltd.)
Was added and mixed uniformly. Further, 0.4 part of zinc octylate was added as a catalyst, and the mixture was dissolved and mixed. To this, 500 parts of an inorganic filler (trade name: calcined talc BST- # 200, manufactured by Nippon Talc Co., Ltd.) and 8 parts of a black dye were added. The varnish A was obtained by stirring and mixing. This varnish is 100μ thick
m, and dried at 150 ° C. to prepare a prepreg (prepreg B) having a gel time (at 170 ° C.) of 120 seconds and a glass cloth content of 57% by weight. The 12 μm-thick electrolytic copper foil was placed above and below the four prepregs B, and
The laminate was molded under a vacuum of 20 kgf / cm ² and a pressure of 30 mmHg or less for 2 hours to obtain a double-sided copper-clad laminate having an insulating layer thickness of 400 μm. On this surface, a paint obtained by adding copper powder (average particle diameter: 0.9 μm) to an aqueous solution of polyvinyl alcohol was applied to a thickness of 60 μm and dried to form a film of 10 vol% of metal powder. From above, 900 pulses of 100 μm in diameter with a spacing of 300 μm were directly irradiated with 6 pulses (shot) at an output of 40 mJ / pulse by a carbon dioxide gas laser to form 70 blocks of through-holes. By the SUEP method, the copper foil burrs around the holes were dissolved and removed, and the copper foil on the surface was also dissolved to 5 μm. This plate is plated with copper by a usual method at 15 μm (total thickness: 20 μm).
m) applied. All of the land copper foil around this hole remained. A circuit (line / space = 50/50 μm 200 pieces), a land for solder balls, etc. are formed on the front and back sides by a conventional method. And plated with nickel and gold to prepare a printed wiring board. Table 1 shows the evaluation results of the printed wiring board.

Example 2 700 parts of an epoxy resin (trade name: Epicoat 5045), 300 parts of an epoxy resin (trade name: ESCN220F), 35 parts of dicyandiamide, and 1 part of 2-ethyl-4-methylimidazole were mixed with methyl ethyl ketone and dimethylformamide. Dissolved in a mixed solvent, and further calcined talc (trade name; BST- # 20)
0) was added, and the mixture was uniformly dispersed by forced stirring. This was impregnated into a glass woven cloth having a thickness of 100 μm and dried to prepare a prepreg (prepreg C) having a gelling time of 15 seconds and a glass cloth content of 53% by weight. Using two prepregs C,
Place 12μm electrolytic copper foil on both sides, 190 ℃, 20kgf / cm ² ,
Laminate molding was performed for 2 hours under a vacuum of 30 mmHg or less to prepare a double-sided copper-clad laminate D. The thickness of the insulating layer was 200 μm. Circuits were formed on the front and back, black copper oxide treatment was performed, and an inner layer plate was formed. The varnish was impregnated into a liquid crystal polyester fiber nonwoven fabric having a thickness of 80 μm and dried to obtain a prepreg having a gel time of 105 seconds. The prepreg was placed above and below the inner layer plate, and a 12 μm electrolytic copper foil was placed on the outside of the prepreg, and similarly laminated and molded to obtain a four-layer plate. On the other hand, nickel powder (average particle diameter 0.7 μm) was blended into a resin aqueous solution consisting of polyvinyl alcohol and starch, and after uniform stirring and mixing,
This was applied to one side of a 50 μm polyethylene terephthalate film so as to have a thickness of 20 μm, and dried at 110 ° C. for 25 minutes to prepare a film-form auxiliary material E having a metal powder content of 90% by volume. The auxiliary material E is placed on the four-layer copper-clad multilayer board such that the resin layer containing the metal powder is in contact with the copper foil surface, and from there, 7 pulses (shot) at a carbon dioxide laser output of 30 mJ / pulse. Irradiation was performed to form through holes for through holes. Thereafter, processing was performed in the same manner to produce a printed wiring board. Table 1 shows the evaluation results.

Comparative Example 1 The double-sided copper-clad laminate of Example 1 was drilled in the same manner with a carbon dioxide laser without surface treatment, but no holes were formed.

Comparative Example 2 In Example 2, Epicoat 5045 was used as the epoxy resin.
Using a double-sided copper-clad multilayer board prepared in the same manner as above, using 1000 parts alone, applying a black magic to the surface of the portion to be drilled, and irradiating the same with a carbon dioxide gas laser in the same manner, but there was no hole.

Comparative Example 3 Using the double-sided copper-clad multilayer board of Comparative Example 2, similarly arranging auxiliary materials, irradiating 19 shots with a carbon dioxide laser at an output of 17 mJ / pulse in the same manner, Opened. In this hole wall, glass fiber was found in the hole, and the hole shape was not a perfect circle but an elliptical shape. Table 1 shows the evaluation results. The printed wiring board was prepared by performing the same processing without performing the SUEP process.

Comparative Example 4 Using the double-sided copper-clad laminate of Example 1, holes were drilled at intervals of 300 μm with a mechanical drill having a diameter of 100 μm at a rotation speed of 100,000 rpm and a feed speed of 1 m / min. After the desmear treatment was not performed, copper plating was similarly performed at 15 μm thereafter, circuits were formed on the front and back surfaces, and the same processing was performed to produce a printed wiring board. Two drill breaks occurred on the way. Table 1 shows the evaluation results.

Comparative Example 5 On the copper foil surface of the double-sided copper-clad laminate of Example 1, 900 holes each having a hole diameter of 100 μm were formed by etching the copper foil at intervals of 300 μm. Similarly, a hole with a hole diameter of 100 μm
Open 900 pieces, 70 blocks of 900 pieces per pattern, total 63,
000 holes from the surface with carbon dioxide laser, output 40mJ /
Six pulses (shots) were applied to form a through hole for a through hole. After that, in the same manner as in Comparative Example 4, the SUEP
Without performing the treatment, copper plating was applied at 15 μm, circuits were formed on the front and back sides, and a printed wiring board was similarly prepared. Table 1 shows the evaluation results.

<Measurement method> 1) Misalignment of the front and back holes and drilling time A hole with a hole diameter of 100 μm was placed in a work size of 250 mm square by 900.
70 blocks (63,000 holes total) were prepared as holes / blocks. Drilling was performed with a carbon dioxide laser. The required time and the maximum value of the deviation between the front and back hole positions are shown. 2) Cut and short circuit patterns In the examples and comparative examples, a plate without holes was prepared in the same manner, and a comb pattern of line / space = 50/50 μm was prepared, and then 200 patterns were etched with a magnifying glass. Was visually observed, and the total of the broken pattern and the short-circuited pattern was shown in the molecule. 3) Glass transition temperature Measured by the DMA method. 4) Through-hole / Heat cycle test A land diameter of 200 μm was created for each through-hole, 900 holes were connected alternately on the front and back, and one cycle was performed at 260 ° C, solder, immersion for 30 seconds → room temperature for 5 minutes, and 200 cycles were performed. And the maximum value of the rate of change of the resistance value. 5) Insulation resistance value after pressure cooker treatment In Examples and Comparative Examples, line / space = 50 / 50μ
m, create a comb pattern, select one without pattern breaks and shorts, apply a black metal oxide film on it,
One identical prepreg is placed on this, and 12μ
m of electrolytic copper foil was placed and laminated and formed under the same conditions to obtain a multilayer board. After forming a circuit on this, it is heated to 121 ° C.
Put it in the atmosphere for a predetermined time, take it out, then 25 ℃ ・ 60% R
H was left for 2 hours, 500 VDC was applied for 60 seconds, and the insulation resistance between the terminals was measured. 6) Migration resistance 900 through holes of 300 μm between holes and 100 μm in diameter are connected independently one by one alternately on the front and back sides. 70 sets of these are made, and 50 VDC is applied in an atmosphere of 85 ° C. and 85% RH. Then, the insulation resistance between the through holes after the treatment for a predetermined time was measured.

Table 1 Item Example Comparative Example 1 2 3 4 5 Position of Front and Back Lands 0 0 0 0 25 Deviation (μm) Hole Shape Round Circular Elliptical Round Upper Round Lower Elliptical Hole Inside Straight Line Straight Inner Wall Straight Almost Straight Unevenness Large pattern breaks and shorts (pieces) 0/200 0/200 55/200 57/200 57/100 Glass transition temperature (℃) 235 160 139 234 235 Through-hole heat cycle test (%) 2.5 5.7 25.0 2.6 5.0 Pressure condition ^{6 × 10 13 - 6 × 10} 13 - - cooked ^{200hrs 4 × 10 12 - 3 ×} 10 9 - - insulation resistance 500hrs 5 × 10 ¹¹ after - <10 ⁸ - - value (Ω) 700hrs 3 × 10 ¹¹ - - - - 1000hrs 9 × 10 10 - - - - anti-migration state ^{5 × 10 13 - 6 × 10} 13 - - Deployment of ^{200hrs 4 × 10 12 - 8 ×} 10 9 - - (Ω) 500hrs 5 × 10 11 ^{- 1 × 10 9 - - 700hrs} 3 × 10 11 - <10 8 - - 1000hrs 1 × 10 11 - - - - drilling time 18 21 - 630 - (min)

[0037]

According to the present invention, a carbon dioxide laser is irradiated by pulse oscillation of a carbon dioxide laser using an energy selected from 20 to 60 mJ / pulse sufficient to remove copper foil with the carbon dioxide laser. In processing a copper foil of a copper-clad board having a copper layer by drilling a through hole or a via hole for a through hole, a metal powder and an organic substance are formed on the copper foil surface of the copper-clad board irradiated with a carbon dioxide laser. Is formed, and a carbon dioxide laser is directly irradiated to form a through hole for a through hole or a via hole. Furthermore, both surfaces of the copper foil are etched two-dimensionally, and part of the thickness of the original copper foil is removed by etching, and at the same time, burrs of the metal generated in the hole are removed by etching. By forming the plating holes of the through holes and the via holes where the copper foil remains, the copper foil positions of the upper and lower holes do not shift, lands can be formed, and the through holes can be formed without bending up and down, and When removing burrs in the holes, the surface of the copper foil can also be removed by etching at the same time, and defects such as short-circuits and pattern breaks also occur in the circuit formation of the front and back copper foil obtained by plating up with subsequent copper plating. Thus, a high-density printed wiring board could be produced without any problem, and a product excellent in reliability and the like could be obtained. Also, the processing speed is much faster than that of a drill, and the productivity can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a process drawing of a through hole for a through hole by a carbon dioxide laser according to a first embodiment.

FIG. 2 is a similar process drawing using a carbon dioxide laser of Comparative Example 5. However, SUEP is not used.

[Explanation of symbols]

 a Resin coating containing metal powder b Copper foil c Thermosetting resin layer of glass cloth base d Drilled through hole by carbon dioxide gas laser e Burr generated

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuo Tanaka 6-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo factory F-term (reference) 4E068 AA04 AF01 CA03 CF03 DA11 DB02

Claims (2)

[Claims] 1. Copper having at least two or more copper layers by pulse oscillation of a carbon dioxide gas laser using an energy selected from 20 to 60 mJ / pulse sufficient to remove a copper foil with a carbon dioxide gas laser. In the method of forming a through hole or a via hole for a through hole in a veneer, an organic coating film or sheet containing 3 to 97% by volume of metal powder is arranged on at least the copper foil surface of the copper veneer to be irradiated with a carbon dioxide laser. And forming a through hole for a through hole by irradiating a required pulse of a carbon dioxide laser. 2. A hole for a through hole is formed by etching away a part of the copper foil on both surfaces of the perforated copper clad plate and simultaneously removing burrs of the hole. 2. The method for forming a through hole for a through hole according to claim 1.