JPH11289147A - Formation of through hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To open a small diameter through hole accurately in a copper clad laminated plate by irradiating high output carbon dioxide gas laser directly. SOLUTION: A metal oxide film is formed on the copper foil of a thermosetting resin copper clad laminated plate having more than one copper layer using one energy selected from 20-60 mJ/pulse sufficient for removing the copper foil with carbon dioxide gas laser and then a through hole is opened by irradiating carbon dioxide gas laser directly. Furthermore metal foil on the opposite sides is subjected to planar etching and a part of original copper foil is removed by etching and, at the same time, the hole part is deburred to form a through hole for through hole plating. Since holes can be opened accurately on the opposite sides, through hole for high density printed wiring board can be obtained economically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, in which a copper-clad laminate having at least two copper layers is directly drilled with a carbon dioxide gas laser. The small printed wiring board is mainly used for a new semiconductor plastic package or the like.

[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 smaller and smaller, and the hole diameter has become 0.15 mmφ or less.When drilling such small holes, the drill diameter is small, so the drill bends when drilling, the processing speed is slow, etc. However, there is a problem in productivity, reliability and the like. In addition, the circuit width and space of high-density printed wiring boards are becoming increasingly narrower, and lines / spaces are 100 μm.
Some have a size of m / 100 μm or less, and in this case, too, many patterns are cut or short-circuit defects occur, and the yield is low.

[0003] Furthermore, if holes of the same size are made in advance by a predetermined method using a negative film in the upper and lower copper foils, and a through hole for conducting the upper and lower sides with a carbon dioxide laser is to be formed, the upper and lower holes are formed. Have disadvantages, such as a shift in the position, 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.
When the output is small, the thermosetting resin copper-clad laminate of the glass cloth base material has difficulties in processing the glass, and there are problems such as fluffs remaining on the hole walls, and also contains an inorganic filler. And a defect such as a residue remaining after processing was observed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a small-diameter through hole for a through hole, which solves the above problems.

[0005]

That is, the present invention provides a method for removing 20 to 60 mJ / cm 2 sufficient to remove a copper foil with a carbon dioxide gas laser.
Using one energy selected from the pulse, the carbon dioxide laser is directly irradiated by the pulse oscillation of the carbon dioxide gas laser, and the copper foil of the thermosetting resin copper-clad laminate having at least two or more copper layers is formed. In drilling and drilling through holes, the surface of the copper foil to be irradiated with a carbon dioxide gas laser is coated with a generally known black or brown metal oxide film, preferably with irregularities of about 0.5 to about 0.5 to such a degree that the carbon dioxide laser light is not reflected.
This method is to form a through hole for through-holes by directly irradiating a carbon dioxide gas laser to a thickness of 3 μm and then etching both surfaces of the copper foil two-dimensionally. A method for forming a through hole for a through hole, characterized in that a portion for the through hole is formed by etching and removing a copper foil burr generated in the hole at the same time as removing the portion by etching.

In the present invention, the glass cloth substrate thermosetting copper-clad laminate has a glass content of 40 to 65% by weight, and 10 to 60% by weight in the thermosetting resin composition. Inorganic filler is mixed, and the hole is 100μm thick with carbon dioxide laser output of 20-60mJ / pulse.
Processing is preferably performed at 1 to 10 shots per m. Further, the black or brown metal oxide film formed on the surface of the copper foil at the hole forming position on the surface to be irradiated with the carbon dioxide gas laser has irregularities such as not reflecting the carbon dioxide laser light, for example, irregularities of 0.5 to 3 μm. It is preferable to use the one formed as described above.

According to the present invention, the lands can be formed without displacing the copper foil positions of the upper and lower holes, and the through-holes can be formed without bending up and down. In the circuit formation of the front and back copper foils obtained by plating up in the above, a high-density printed wiring board was able to be produced without occurrence of defects such as short-circuits and cut patterns. In addition, a processing speed was remarkably higher than that of the case of drilling, and a product having good productivity and excellent economic efficiency was obtained.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making through holes for through holes, particularly small diameter holes, in a copper-clad laminate of at least two layers using a carbon dioxide laser. Are used for mounting semiconductor chips. When drilling a copper-clad laminate with a carbon dioxide gas laser, a black or brown metal oxide film is formed on the surface to be irradiated with the laser, and the carbon dioxide gas laser is directly irradiated on the copper foil surface to form a through hole for a through hole. It is a method of forming.

[0009] The copper-clad laminate used in the present invention is a thermosetting resin copper-clad laminate having at least two or more copper layers. Or use a glass cloth base thermosetting copper-clad laminate for the inner layer,
A generally known material such as a multilayer board obtained by disposing a resin layer and a thermosetting resin layer reinforced with an organic base material on the outside thereof, further placing a copper foil on the outside thereof, and laminating and forming the same is included. In the present invention, the output of the carbon dioxide laser is 20 to 60.
With a high output of mJ / pulse, the surface of which is covered with a black or brown metal oxide film is perforated so that copper foil, glass fiber and inorganic filler can be processed without leaving any residue. It is possible to easily form a through hole for a through hole.

As the glass cloth substrate, generally known woven or non-woven cloth of glass fiber can be used.
A, C, L, M, S, D, N, quartz glass, and the like. Examples of the organic cloth substrate include woven fabrics such as wholly aromatic polyamide and wholly aromatic polyester fibers, and nonwoven fabrics. Used in blending.

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 an unsaturated group-containing polyphenylene ether resin. Are used in combination. Polyfunctional cyanate ester resin compositions are preferred from the viewpoints of heat resistance, moisture resistance, migration resistance, electrical properties after moisture absorption, and the like.

The polyfunctional cyanate compound which is a thermosetting resin component of the present invention is a compound having two or more cyanato groups in a molecule. Specifically, 1,3-
Or 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene, 1,3-, 1,4-, 1,6-, 1,8-, 2,6- or 2,7-dicyanato Naphthalene, 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 43-184
68, 44-4791, 45-11712, 46-41112, 47-26853
And polyfunctional cyanate compounds described in JP-A-51-63149 and the like can also be used. A prepolymer having a molecular weight of 400 to 6,000 and having a triazine ring formed by trimerizing a cyanato group of these polyfunctional cyanate compounds is 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 a sodium alcoholate or a tertiary amine; a salt such as sodium carbonate as a catalyst. 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 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 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, 4-fluoroethylene-6-fluoroethylene copolymers; polycarbonate, polyphenylene ether, polysulfone, polyester, polyphenylene sulfide, etc. High molecular weight prepolymers or oligomers; polyurethanes and the like are exemplified, and are 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 economy, so that 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.

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. In addition, it is preferable to add a black dye or pigment to the resin so that light is not dispersed by irradiation with a carbon dioxide laser. As the types of dyes and pigments, generally known ones can be used. 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 metal foil can be used as the outermost metal foil. Preferably, a copper foil or a copper alloy foil having a thickness of 3 to 18 μm is used.

The copper-clad laminate substrate is first impregnated with a thermosetting resin composition and dried to form a B-stage to prepare a prepreg. Next, a predetermined number of the prepregs are used, copper foils are arranged above and below, and laminated under heat and pressure to form a copper-clad laminate.

A black or brown metal oxide film is formed on the copper foil surface of the substrate-reinforced copper-clad laminate at the hole forming position on the surface to be irradiated with the carbon dioxide gas laser, preferably to reduce the reflection of laser light. For this purpose, holes are formed by irradiating a carbon dioxide laser which is formed with fine irregularities of 0.5 to 3 μm and is directly squeezed to a target diameter. A generally known method can be used for forming the metal oxide film. Specifically, a black or brown copper oxide treatment may be mentioned.

When a carbon dioxide laser is irradiated with an output of 20 to 60 mJ / pulse to form a through hole, burrs are generated around the hole. Therefore, after irradiating the carbon dioxide laser, both surfaces of the copper foil are etched two-dimensionally at a speed of 0.02 to 1.0 μm / sec.
By etching away 1/3 to 1/2 the thickness of the original metal foil, burrs are also etched off at the same time, and the obtained copper foil is suitable for fine pattern formation, and high density printing A through-hole plating through-hole in which copper foil on both sides around the hole suitable for a wiring board remains.

The method of etching and removing copper burrs generated in the holes according to the present invention is not particularly limited. For example, Japanese Patent Application Laid-Open Nos. 02-22887, 02-22896, 02-25089 and 02-2.
5090, 02-59337, 02-60189, 02-166789, 03-2
5995, 03-60183, 03-94491, 04-199592, 04-2
According to the method disclosed in 63488 for dissolving and removing a metal surface with a chemical (referred to as SUEP method). Etching rate is 0.02 ~
Perform at 1.0 μm / sec. It is also possible to remove the burrs of the copper foil by mechanical polishing. However, when the copper-clad laminate is thin, problems such as a large dimensional change occur, and burrs cannot be completely removed.

The carbon dioxide laser is in the infrared wavelength range.
Wavelengths of 9.3 to 10.6 μm are commonly used. Output is 20 ~
Processing is performed at a rate of 60 mJ / pulse, preferably 22 to 55 mJ / pulse, with 1 to 10 shots per 100 μm of the thickness of the insulating layer such as a copper-clad laminate. Although it is possible to process even more shots, it is not preferable in terms of productivity.

[0026]

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 and 100 parts of bis (4-maleimidophenyl) methane 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. 400 parts of bisphenol A type epoxy resin (trade name: Epicoat 1001, Yuka Shell Epoxy Co., Ltd.) and cresol novolak type epoxy resin (trade name: ESCN-220F, Sumitomo Chemical Co., Ltd.)
600 parts were added and uniformly dissolved and mixed. Further, 0.4 part of zinc octylate is added as a catalyst, and the mixture is dissolved and mixed, and an inorganic filler (trade name: calcined talc BST-200, Nippon Talc Co., Ltd.) is added.
Varnish A was obtained by adding 500 parts of a black dye and 1 part of a black dye, followed by uniform stirring and mixing.

This varnish is impregnated in a glass woven cloth having a thickness of 100 μm, dried at 150 ° C., and gelled for 120 minutes at at 170 ° C.
In seconds, a prepreg (prepreg B) having a glass cloth content of 57% by weight was prepared. Electrolytic copper foil with a thickness of 12 μm is placed above and below the four prepregs B, 200 ° C., 20 kgf / cm ² ,
Laminate under vacuum of 30mmHg or less for 2 hours, and insulate layer thickness 4
A 00 μm double-sided copper-clad laminate B was obtained.

The surface was subjected to a black copper oxide treatment to form a film having a surface irregularity of 0.7 to 1.3 μm. From above, interval 3
900 pulses of 100 μm in diameter and 100 μm in diameter were directly irradiated with 8 pulses (shots) of 40 mJ / pulse by a carbon dioxide gas laser to form 70 blocks of through-holes. After the desmear treatment, the copper foil burrs around the holes were dissolved and removed by the SUEP method, and the copper foil on the surface was also dissolved to 7 μm. 15μm copper plating (total thickness: 22μm)
gave. All of the land copper foil around this hole remained. On the front and back, a circuit (line / space = 50)
200 pcs / 50 μm), solder ball land, etc. Except for at least the semiconductor chip, bonding pad, and solder ball pad, cover with plating resist, nickel and gold plating, and print wiring board Created. Table 1 shows the evaluation results of the printed wiring board.

Example 2 700 parts of epoxy resin (trade name: Epikote 5045) and 300 parts of epoxy resin (trade name: ESCN220F), 35 parts of dicyandiamide, 1 part of 2-ethyl-4-methylimidazole were mixed with methyl ethyl ketone and dimethylformamide. After dissolving in a solvent, 800 parts of calcined talc (trade name: BST-200) was added, and the mixture was uniformly dispersed by forced stirring (varnish C). This was impregnated into a 100 μm thick glass woven fabric and dried to prepare a prepreg (prepreg D) having a gelling time of 150 seconds and a glass cloth content of 53% by weight. Using two prepregs D, place 12μm electrolytic copper foil on both sides, 190 ° C, 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. The thickness of the insulating layer was 200 μm. A circuit is formed on the front and back sides of this, and a black copper oxide treatment is applied to form an inner plate (hereinafter referred to as an inner plate E).

The varnish C was impregnated into a liquid crystal polyester nonwoven fabric having a thickness of 180 μm and dried to obtain a prepreg having a gelation time of 105 seconds. This prepreg was placed above and below the inner layer plate E, and a 12 μm electrolytic copper foil was placed on the outer side of the prepreg, and similarly laminated and molded to obtain a four-layer plate. A brown copper oxide treatment was similarly performed thereon. The surface irregularities were 0.2 to 1.0 μm. From above, 9 pulses (shots) were directly irradiated at an output of 30 mJ / pulse of a carbon dioxide laser to form a through hole for a through hole. 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 2 was drilled in the same manner with a carbon dioxide gas laser without surface treatment, but no holes were formed. Comparative Example 2 Using the double-sided copper-clad laminate of Example 1, the surface of the portion to be drilled was coated with black magic and irradiated with a carbon dioxide gas laser in the same manner, but no hole was formed. Comparative Example 3 In Example 2, epicoat 5045 was used as the epoxy resin.
A single-sided copper-clad laminate prepared in the same manner was used in 1,000 parts, and black copper oxide treatment was applied in the same way. After that, 19 shots were similarly irradiated with a carbon dioxide laser at an output of 17 mJ / pulse. Drilled through holes for holes. In this hole wall, glass fiber was found in the hole, and the hole shape was not a perfect circle but an elliptical shape.

COMPARATIVE EXAMPLE 4 Using the double-sided copper-clad laminate of Example 1, holes were made 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 rate of 1 m / min. After the desmear treatment, copper plating was similarly applied to 15 μm, circuits were formed on the front and back surfaces, and processed in the same manner to prepare a printed wiring board. Two drill breaks occurred on the way. Table 1 shows the evaluation results.

Comparative Example 5 900 holes having a hole diameter of 900 μm were formed on the copper foil surface of the double-sided copper-clad laminate of Example 1 at intervals of 300 μm, and the copper foil was etched. Similarly, a hole with a hole diameter of 100 μm
Open 900 pieces, 70 blocks of 900 patterns per pattern, 63,0 total
The hole of No. 00 was subjected to 8 pulses (shots) from the surface with a carbon dioxide laser at an output of 40 mJ / pulse, and a through hole for a through hole was formed. Thereafter, in the same manner as in Comparative Example 4, desmear treatment was performed, copper plating was performed at 15 μm, circuits were formed on the front and back surfaces, and a printed wiring board was similarly prepared. Table 1 shows the evaluation results.
Shown in

[0034]

Table 1 Example Comparative Example 1 2 3 4 5 Positional deviation of front and back holes (μm) 0 0 0 0 25 hole shape Circular Circular Oval Circular Circular pattern cut and (pieces) 0/200 0/200 55/200 57 / 100 57/200 Short glass transition temperature (℃) 235 160 139 234 234 Through-hole heat cycle (%) 2.5 5.7 25.0 2.6 5.0 Test pressure Normal 6 × 10 ¹³ − 6 × 10 ¹³ − − Cooker treatment 200hrs 4 × 10 ¹² Insulation resistance after 3 × 10 ⁹ 500hrs 5 × 10 ¹¹ <10 ⁸ value (Ω) 700hrs 3 × 10 ¹¹ 1000hrs 9 × 10 ¹⁰ My gray resistant normal 5 × 10 ¹³ −6 × 10 ¹³ − −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 (min) 24 26 −630 −

<Measurement method> 1) Misalignment of the front and back holes and time for drilling Holes having a hole diameter of 100 μm were cut into 900 holes / block by etching copper foil within a work size of 250 mm square.
Blocks were created (63,000 holes total). Drilling was performed using a carbon dioxide laser and a mechanical drill. The required time and the maximum value of the deviation between the front and back hole positions are shown. 2) Cut and short circuit pattern In the examples and comparative examples, a board without holes was created in the same way, a comb pattern of line / space = 50/50 μm was created, and 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 is formed in each through-hole, 900 holes are alternately connected to the front and back, and one cycle is performed at 260 ° C./solder/immersion for 30 seconds → room temperature / 5 minutes; The cycle was performed, and the maximum value of the rate of change of the resistance value was shown. 5) Insulation resistance value after pressure cooker treatment In Examples and Comparative Examples, line / space = 50 / 50μ
m, a pattern with no cut or short circuit, a black metal oxide film was applied to this, then one identical prepreg was placed on top of this, and a 12 μm electrolytic copper foil was placed on top of it, and the same Lamination molding was performed under the conditions to obtain a multilayer board. After forming a circuit on it, put it in 121 ° C and 2 atm for a predetermined time, take it out, leave it at 25 ° C and 60% RH for 2 hours, apply 500VDC for 60 seconds, and apply The insulation resistance was measured. 6) Migration resistance One through hole with a gap of 300 μm and a diameter of 100 μm is independently connected to each other.
50 VDC was applied in an atmosphere of 85 ° C. and 85% RH, and the insulation resistance between the through holes after a predetermined time treatment was measured.

[0037]

According to the present invention, at least one energy selected from 20 to 60 mJ / pulse sufficient to remove a copper foil with a carbon dioxide laser is used to directly irradiate a carbon dioxide laser by pulse oscillation of the carbon dioxide laser. In drilling a through hole by processing copper foil of a thermosetting resin copper-clad laminate having two or more copper layers, a black or brown metal oxide film is applied to the copper foil surface irradiated with a carbon dioxide laser. After forming a through hole for a through hole by irradiating a carbon dioxide gas laser, both surfaces of the copper foil are planarly etched,
By removing a part of the original copper foil by etching and simultaneously removing the burrs of the metal generated in the hole, by forming a hole for through-hole plating in which the copper foil on both sides around the hole remains. The copper foil positions of the upper and lower holes do not shift, lands can be formed, through holes can be formed without bending, and when removing burrs in the holes, the copper foil surface can also be etched and removed at the same time. In the circuit formation of the front and back copper foil obtained by plating up with copper plating, it is possible to create a high-density printed wiring board without occurrence of defects such as short-circuits and pattern breaks, and obtain products with excellent reliability etc. Was completed. Further, the processing speed is much faster than drilling, and the productivity can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a process chart of a through hole for a through hole by a carbon dioxide gas laser of Examples 1 and 2. (1): formation of a metal oxide film, (2): drilling, (3): removal of burrs by SUEP and melting of surface copper foil, (4): copper plating step.

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

[Explanation of symbols]

a: metal oxide film, b: copper foil, c: glass cloth substrate reinforced thermosetting resin layer, d: through hole through hole by carbon dioxide gas laser, e: generated burrs.

Claims (2)

[Claims] At least one energy selected from 20 to 60 mJ / pulse sufficient to remove a copper foil with a carbon dioxide laser is directly irradiated with a carbon dioxide laser by pulse oscillation of a carbon dioxide laser. When drilling through holes by processing copper foil of a thermosetting resin copper-clad laminate having two or more copper layers, a black or brown metal oxide treatment is applied to the copper foil surface irradiated with a carbon dioxide laser. Subject to
A method for forming a through hole for a through hole, wherein the hole is directly formed by irradiating a carbon dioxide gas laser. 2. The copper foil of the perforated copper clad laminate is planarly etched on both surfaces to partially remove the original metal foil and simultaneously remove burrs in the holes by etching. The method for forming a through hole for a through hole according to claim 1, wherein the hole for a hole is formed.