JP4078715B2 - Highly reliable via hole formation method - Google Patents

Description

【００３３】
＜測定方法＞
1)ビア孔底部
断面を観察した。
2)ビア孔あけ時間
炭酸ガスレーザー及びメカニカルドリルで孔あけを行なった場合の、63,000孔／枚孔をあけるのに要した時間を示した。
3)回路パターン切れ及びショート
実施例、比較例で、ライン/スペース＝50/50μm のパターンを拡大鏡で200パターン目視にて観察し、パターン切れ、及びショートしているパターンの合計を分子に示した。
4)ガラス転移温度
ＤＭＡ法にて測定した。
5)ビア孔ヒートサイクル試験
ビア孔を表裏交互に900孔つなぎ1サイクルが、260℃・ハンダ・浸せき30秒→ 室温・5分 で、200サイクル実施し、抵抗値の変化の最大値を示した。
【００３４】
【発明の効果】
プリント配線板の表層にある１層目の銅箔と、ビア孔部にある銅箔間を電導導通するためのマイクロビア孔を炭酸ガスレーザーであけるに際し、ビア孔底部の銅面の表層一部を除去し、且つ、銅箔を貫通しない形でビア孔を形成し、金属メッキ又は導電塗料で最外層とビア部の銅層とを導通する構造のビア孔が形成されたプリント配線板とすることにより、デスミア処理の必要もなく、最外層とビア部に露出した銅層との接続信頼性に優れたものを得ることができた。また、加工速度はドリルであけるのに比べて格段に速く、生産性についても大幅に改善できるものである。銅箔孔あけ部に張りだした銅箔バリ及び銅箔の表面を厚さ方向に一部平面的に同時に薬液でエッチング除去することにより、銅箔が薄くなるため、その後の金属メッキでメッキアップして得られた表裏銅箔の細線の回路形成において、ショートやパターン切れ等の不良の発生もなく、高密度のプリント配線板を作成することができた。
【図面の簡単な説明】
【図１】 実施例２の炭酸ガスレーザーによるビア孔あけ［（１）、（２）（３）］の工程図である。
【図２】 実施例２のＳＵＥＰによるバリ除去（４）及び銅メッキ（５）の工程図である。
【図３】 比較例２の炭酸ガスレーザーによる同様の工程図である。
【図４】 比較例４の炭酸ガスレーザーによるビア孔あけ［（１）、（２）、（３）］の工程図である。
【図５】 比較例４の銅メッキ（４）の工程図である。
【符号の説明】
ａ 金属粉含有樹脂シート
ｂ 銅箔
ｃ ガラス布基材熱硬化性樹脂層
ｄ 40mJ/パルスの炭酸ガスレーザー
ｅ 発生したバリ
ｆ 30mJ/パルスの炭酸ガスレーザー
ｇ ビア孔底部の銅箔表層
ｈ ビア孔銅メッキ部
ｉ メカニカルドリル
ｊ ４層目（下側外層銅箔）ヘ突き抜けた孔
ｋ 高出力の炭酸ガスレーザーで内層銅箔を突き抜けた箇所[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a via hole in a printed wiring board. In particular, a part of the surface layer of the copper foil at the bottom of the via hole, which becomes a via hole, is removed so that the copper foil does not penetrate, and the via hole obtained by metal plating or conductive paint is used for the surface layer and the via. The present invention relates to a method for forming a via hole in a printed wiring board having excellent connection reliability, wherein the hole copper foil layer is electrically connected. The obtained printed wiring board is mainly used for a small semiconductor plastic package.
[0002]
[Prior art]
Conventionally, a high-density multilayer printed wiring board used for a semiconductor plastic package or the like has a via hole drilled or a carbon dioxide laser. When drilling, if the copper foil thickness of the inner layer is thin or the thickness variation of the multilayer board is large, it is difficult to stop the via hole in the middle of the inner copper foil, sometimes reaching the copper foil layer below it It was a cause of failure. When drilling with a carbon dioxide laser, a resin layer of about 1 μm remained on the copper foil surface on the lower surface of the via hole, and it was necessary to perform desmear treatment before copper plating. In this case, if the desmear treatment is insufficient, the electrical conductivity between the surface layer after copper plating and the copper foil therebelow is not good, resulting in poor conduction. In addition, the desmear process has a problem that it takes two to three times as long as the general desmear process time for a through hole or the like and the workability is poor.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for forming a small-sized via hole at a high speed that does not require desmearing and solves the above-described problems.
[0004]
[Means for Solving the Problems]
Copper foil of the double-sided copper clad laminate and multilayer plate surface with a copper foil on both surfaces, the surface is irradiated at least carbon dioxide laser, with melting point 900 ° C. or higher, and bond energy 300 kJ / mol or more metal compounds, carbon powder Alternatively, a coating film or sheet made of one or more metal powders and a water-soluble resin is arranged, and a pulse oscillation of a carbon dioxide laser having an energy selected from the energy of 20 to 60 mJ / pulse is provided at least. A hole is made in the copper foil on the surface layer, and then, at the energy of 20 to 35 mJ / pulse, the bottom of the via hole below or a part of the surface layer of the opposite outer layer copper foil on the double-sided plate is processed so that the copper foil does not penetrate. Then, a via hole in which a new surface inside the copper foil at the bottom of the via is exposed is formed.
After that, to process the copper foil surface in the drug solution. When processing with a chemical solution, in forming a via hole using a double-sided copper-clad plate, care is taken so that the copper foil in the via hole is not dissolved.
When a via hole is formed by directly irradiating the copper foil with a carbon dioxide laser, burrs of the copper foil are generated at the surface copper foil perforated portion. Since it is difficult to take in the mechanical polishing, it etched with a chemical solution. Both surfaces of the copper foil are planarly etched, and a part of the thickness of the original copper foil is removed by etching, thereby simultaneously removing the copper foil burrs protruding from the holes. When such a treatment is carried out, the copper foil becomes thin. Therefore, in the formation of a thin line circuit of the front and back copper foil obtained by plating up with subsequent metal plating, there is no occurrence of defects such as short-circuiting or pattern breakage. A printed wiring board with high density could be created. In addition, there is no need to apply desmear treatment, it is excellent in workability, and when connecting the outermost layer and the copper foil directly below it with metal plating or conductive paint, the connection area is large and the connection reliability of the via hole is excellent Things were obtained.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for forming a via hole that does not require desmear treatment on a surface layer of a double-sided copper-clad plate and a multilayer plate having at least two copper layers before metal plating.
As a method for forming a via hole in the surface, the metal compound powder and the binding energy in melting point 900 ° C. or higher 300 mJ / pulse, one of the carbon powder or metal powder, or a resin containing two or more 3 to 97 volume% The composition is applied to the surface of the copper foil to form a coating, or arranged as a sheet shape, and directly irradiated with energy selected from a high output 20 to 60 mJ / pulse carbon dioxide laser from above. A hole is made in the copper foil, and then the copper foil at the bottom of the via hole underneath, or a part of the outer layer copper foil on the opposite side of the double-sided plate, is encapsulated with energy selected from 20 to 35 mJ / pulse. The foil is processed so that it does not penetrate, and a via hole in which a new surface inside the copper foil is exposed is formed.
After that, performing a copper foil surface treatment with chemical liquid. In the case of mechanical polishing, a general polishing machine can be used. However, if burrs occur in the hole, it is necessary to perform polishing several times, and the dimensional change rate of the plate may increase. Oh Ru. In the present invention, simultaneously with the etching of the surface layer with chemical, it intends row copper foil surface treatment method of dissolving and removing even the burrs. By removing both surfaces of the copper foil by planar etching, the copper foil becomes thin, and in the formation of thin wire circuits on the front and back copper foils obtained by plating up with subsequent metal plating, defects such as shorts and pattern breaks There is no occurrence, and a high-density printed wiring board can be created. Moreover, since it is not necessary to perform a desmear process, it is excellent in workability. When there is no resin layer on the copper foil surface at the bottom of the via hole and the via hole is plated with metal or embedded with conductive paint, the outermost layer of the via hole is connected to the copper foil directly below it. A printed wiring board having a large area and excellent via hole connection reliability could be obtained. As the chemical for etching, generally known chemicals can be used. For example, JP 02-22887, 02-22896, 02-25089, 02-25090, 02-59337, 02-60189, 02-166789, 03-25995, 03-60183, 03 -94491, 04-199592, 04-263488, and the chemicals disclosed in JP-A-04-263488 are used. These chemicals dissolve and remove the metal surface (referred to as the SUEP method). The etching rate is generally 0.02 to 1.0 μm / sec.
[0006]
The double-sided board and multilayer board having at least two or more copper layers used in the present invention are preferably made of glass cloth as a base material and blackened by adding a dye or pigment to the thermosetting resin composition. In addition, a double-sided copper-clad laminate having a homogeneous structure in which 10 to 60% by weight of an inorganic insulating filler is mixed in the resin composition is used.
Moreover, as a multilayer board, the said double-sided copper clad laminated board of a glass cloth base material is processed into an inner-layer board, and it is used suitably. Apply metal copper oxide treatment to the surface as necessary, place inorganic or organic cloth base material prepreg, resin sheet, copper foil with resin, or paint film with paint on top and bottom, place copper foil if necessary, heat, pressurize, Preferably, lamination molding is performed under vacuum.
In addition to the copper-clad plate described above, a double-sided plate or a multilayer plate of a generally known high heat-resistant film such as a polyimide film, a polyester film, or a polyparabanic acid film can be used.
[0007]
As the substrate, generally known inorganic and organic woven fabrics and nonwoven fabrics can be used. Specifically, examples of the inorganic base material include woven fabrics and nonwoven fabrics of fibers such as E, S, D, and M glass. Examples of organic fibers include woven fabrics and nonwoven fabrics of fibers such as liquid crystal polyester and wholly aromatic polyamide.
[0008]
As the resin of the thermosetting resin composition used in the present invention, generally known thermosetting resins are used. Specific examples include epoxy resins, polyfunctional cyanate ester resins, polyfunctional maleimide-cyanate ester resins, polyfunctional maleimide resins, unsaturated group-containing polyphenylene ether resins, and the like. More than one type is used in combination. Considering the shape of the through-hole formed by processing with high-power carbon dioxide laser irradiation, a thermosetting resin composition with a glass transition temperature of 150 ° C or higher is preferable, moisture resistance, migration resistance, and electrical characteristics after moisture absorption In view of the above, a polyfunctional cyanate ester resin composition is preferred.
[0009]
The polyfunctional cyanate ester compound which is the 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-cyanato Phenyl) 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 reaction of novolac with cyanogen halide.
[0010]
In addition to these, the polyfunctionality described in JP-B Nos. 41-1928, 43-18468, 44-4791, 45-11712, 46-41112, 47-26853 and JP-A-51-63149 Cyanate ester compounds can also be used. In addition, a prepolymer having a molecular weight of 400 to 6,000 having a triazine ring formed by trimerization of cyanate groups of these polyfunctional cyanate ester compounds is used. This prepolymer polymerizes the above-mentioned polyfunctional cyanate ester monomers using, for example, acids such as mineral acids and Lewis acids; bases such as sodium alcoholates and tertiary amines; salts such as sodium carbonate and the like as catalysts. Can be obtained. This prepolymer also includes a partially unreacted monomer, which is in the form of a mixture of the monomer and the prepolymer, and such a raw material is suitably used for the application of the present invention. Generally, it is used after being dissolved in a soluble organic solvent.
[0011]
As the epoxy resin, generally known epoxy resins can be used. Specifically, liquid or solid bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin; butadiene, pentadiene, vinylcyclohexene, dicyclopentyl ether, etc. And polyglycidyl compounds obtained by reaction of polyols, hydroxyl group-containing silicon resins and epohalohydrin, and the like. These may be used alone or in combination of two or more.
[0012]
As the polyimide resin, generally known resins can be used. Specific examples include reaction products of polyfunctional maleimides and polyamines and terminal triple bond polyimides described in JP-B-57-005406.
[0013]
These thermosetting resins may be used alone, but may be used in appropriate combination in consideration of balance of characteristics.
[0014]
In the thermosetting resin composition of the present invention, various additives can be blended as desired within a range where the original 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-acrylonitrile copolymer, polychloroprene, butadiene-styrene copolymer. Low molecular weight liquid to high molecular weight elastic rubbers such as polymers, polyisoprene, butyl rubber, fluororubber, 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; high molecular weight prepolymers such as polycarbonate, polyphenylene ether, polysulfone, polyester, polyphenylene sulfide Are oligomers; polyurethane and the like are exemplified and used as appropriate. In addition, various additions of known organic fillers, thickeners, lubricants, antifoaming agents, dispersants, leveling agents, photosensitizers, flame retardants, brighteners, polymerization inhibitors, thixotropic agents, etc. Agents are used in appropriate combinations as desired. If necessary, the compound having a reactive group is appropriately mixed with a curing agent and a catalyst.
[0015]
Although the thermosetting resin composition of the present invention itself is cured by heating, the curing rate is slow and the workability, economy and the like are inferior, so that a known thermosetting catalyst can be used for the thermosetting resin used. . The amount used is 0.005 to 10 parts by weight, preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the thermosetting resin.
[0016]
As the inorganic insulating filler, generally known ones can be used. Specifically, 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, perlite, etc. It is done. The addition amount is 10 to 60% by weight, preferably 15 to 55% by weight.
[0017]
Further, 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. The particle diameter is preferably 1 μm or less for uniform dispersion. As the kind of dye and pigment, generally known insulating ones can be used. The addition amount is preferably 0.1 to 10% by weight. Furthermore, the glass fiber etc. which dyed the surface of the fiber black can also be used.
[0018]
Generally known copper foil can be used for the outermost copper foil. Preferably, an electrolytic copper foil having a thickness of 3 to 18 μm is used. Moreover, 12-70 micrometers electrolytic copper foil is used suitably for inner layer copper foil.
[0019]
The glass cloth base reinforced copper clad laminate preferably used is firstly impregnated with the thermosetting resin composition to the glass cloth base so that the glass content becomes 30 to 80% by weight and dried to form a B stage. Create a prepreg. Next, a predetermined number of the prepregs are used, copper foils are arranged on the upper and lower sides, and are laminated and formed under heating and pressure to obtain a double-sided copper-clad laminate. In the cross section of the copper clad laminate, the resin other than glass and the inorganic filler are uniformly dispersed, and the holes are evenly formed when laser drilling is performed. Further, since it is black, the laser beam is difficult to disperse, and the hole wall is uniform with few irregularities.
[0020]
Double-sided copper-clad laminate, or on the copper foil surface to be irradiated with a carbon dioxide laser of the surface layer of the multilayer board, with melting point 900 ° C. or higher, and the binding energy of atoms is 300 kJ / mol or more metal compounds powder, carbon powder or metal A resin coating film or sheet containing 3 to 97% by volume of powder is placed, and a carbon dioxide laser is directly irradiated to make a hole.
[0021]
As the auxiliary material used in the present invention, generally known compounds can be used as the metal compound having a melting point of 900 ° C. or higher and a binding energy of 300 kJ / mol or higher. For example, titanias as oxides; magnesias; iron oxides; zinc oxides; cobalt oxides; tin oxides, etc. Non-oxides include silicon carbide, tungsten carbide, boron nitride, Examples include silicon nitride, titanium nitride, and barium sulfate. In addition, carbon can be used. These may be used alone or in combination of two or more. Furthermore, generally known metal powder is used. However, those that generate heat or ignite when dissolved in water or solvents are not used. Those having an average particle diameter of 5 μm or less, preferably 1 μm or less are used.
[0022]
The water-soluble resin of the auxiliary material was mixed kneaded applied to a copper foil surface, when dried, or when a sheet, you select the one which does not peel missing from copper foil. In particular, water-soluble resin in terms of the environment, such as polyvinyl alcohol, polyvinyl alcohol saponified, polyesters, such as starch, generally known is preferably used.
[0023]
How to create a metal compound powder, carbon powder or metal powder and consisting of water-soluble resin composition is not particularly limited, kneading at high temperature without a solvent in a kneader or the like, how to extrude into sheets, dissolved in water Using the resin composition, add the above powder to this, stir and mix uniformly, and use this to apply to the surface of the copper foil as a paint and dry to form a film. And a sheet obtained by impregnating and drying a glass substrate and the like.
[0024]
A carbon dioxide laser generally has a wavelength of 9.3 to 10.6 μm in the infrared wavelength region. The output is 20-60 mJ / pulse. First, at least the first layer copper foil on the surface is processed to make a hole, and then the output is dropped to 20-35 mJ / pulse. The surface layer of the copper foil to be processed is preferably processed so as not to penetrate the copper foil. In general, it is processed at 1 to 10 shots per 100 μm thickness of an insulating layer such as a glass cloth base copper clad laminate.
[0025]
For plating the via hole, generally known copper plating or the like can be used. Also, a conductive paint is put into the via hole so that the upper and lower copper foil layers are electrically connected. As the conductive paint, generally known ones can be used. Specifically, a copper paste, a silver paste, a solder paste, and other solders.
[0026]
【Example】
The present invention will be specifically described below with reference to examples and comparative examples. Unless otherwise specified, “parts” represents 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 for 4 hours with stirring 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, manufactured by Yuka Shell Epoxy Co., Ltd.) and 600 parts of cresol novolac type epoxy resin (trade name: ESCN-220F, manufactured by Sumitomo Chemical Co., Ltd.) In addition, it was uniformly dissolved and mixed. Further, 0.4 part of zinc octylate as a catalyst was added, dissolved and mixed, and this was mixed with an inorganic insulating filler (trade name: BST # 200, with an average particle diameter of 0.4 μm, manufactured by Nippon Talc Co., Ltd.), and 8 parts of a black pigment was added and uniformly stirred and mixed to obtain varnish A. This varnish was impregnated into a glass woven cloth having a thickness of 100 μm 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. An electrolytic copper foil with a thickness of 18μm is placed on the top and bottom of the prepreg B1 and laminated for 2 hours under a vacuum of 200 ° C, 20kgf / cm ² , 30mmHg, and a double-sided copper-clad laminate B with an insulating layer thickness of 100μm Got.
On the other hand, 800 parts of copper oxide powder having an average particle size of 0.86 μm was added to a varnish obtained by dissolving a partially saponified water-soluble polyvinyl alcohol powder in water, and the mixture was uniformly stirred and mixed (varnish C). This was coated on a polyethylene terephthalate film having a thickness of 25 μm, a thickness of 50 μm, and dried at 110 ° C. for 30 minutes to form a sheet with a film having a copper oxide powder content of 20% by volume. Place this on the double-sided copper-clad laminate B, and apply 900 pulses of holes with a spacing of 400μm and a diameter of 100μm directly with a carbon dioxide laser, one pulse (shot) at an output of 40mJ / pulse, and then output. The surface layer portion of the copper foil on the lower outer layer was processed and removed with 2 pulses at a drop of 30 mJ / pulse. A total of 70 blocks of via holes (63,000 holes in total) were drilled. Thereafter, the back surface was coated with an etching resist, the entire surface was treated by the SUEP method, and the copper foil burrs around the holes were dissolved and removed, and at the same time, the copper foil on the surface was dissolved to 7 μm. After removing the etching resist, this time, the entire surface is covered with the etching resist, and the copper foil on the back surface is dissolved and removed to 7 μm by the SUEP method. After removing the etching resist, the copper plating is 15 μm on this plate (total thickness: 22 μm) gave. A land having a diameter of 250 μm was formed at the location of the via hole, and a copper foil at the bottom of the via hole was used as a ball pad. In addition, a circuit (200 lines / space = 50 / 50μm) is formed, and solder ball lands, etc. are formed thereon, and at least the semiconductor chip, bonding pads, and solder ball pads are covered with a plating resist. Then, nickel and gold plating were applied to produce a printed wiring board. The evaluation results of this printed wiring board are shown in Table 1.
[0027]
Example 2
1400 parts of epoxy resin (trade name: Epicoat 5045), 600 parts of epoxy resin (trade name: ESCN220F), 70 parts of dicyandiamide, 2 parts of 2-ethyl-4-methylimidazole are dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide, and 500 parts of the insulating inorganic filler of Example 1 was added, and the mixture was forcibly stirred and uniformly dispersed to obtain varnish D. This was impregnated into a 50 μm thick glass woven cloth and dried to prepare a prepreg (prepreg E) having a gel time of 150 seconds and a glass cloth content of 35 wt%. One prepreg E was used, an electrolytic copper foil of 18 μm was placed on both sides, and laminate molding was performed for 2 hours under a vacuum of 190 ° C., 20 kgf / cm ² , 30 mmHg or less to prepare a double-sided copper clad laminate F. The thickness of the insulating layer was 100 μm. After forming a circuit above and below and performing copper oxide treatment, prepreg E is placed on the top and bottom, 12 μm electrolytic copper foil is placed on both sides, and laminated in the same manner, and a four-layer board with double-sided copper foil F.
On the other hand, copper powder having an average particle size of 0.7 μm was dissolved in a polyvinyl alcohol solution to obtain varnish G having 70% by volume of copper powder. This was applied onto the double-sided copper-clad four-layer board F so as to have a thickness of 40 μm, and dried at 110 ° C. for 30 minutes to form a coating film (FIG. 1 (1)). From this, a hole of 100μm in diameter is made in the copper foil with 2 pulses (shot) at a carbon dioxide laser output of 40mJ / pulse (Fig. 1 (2)), and then similarly processed with 2 pulses at 30mJ / pulse. Thereafter, a multilayer printed wiring board in which via holes were formed was produced in the same manner as in Example 1 (FIGS. 1, 2 (3), (4), and (5)). The evaluation results are shown in Table 1.
[0028]
Comparative Example 1
Double-sided copper-clad laminate of Example 1, have use a double-sided copper-clad multilayer plate of Example 2, was carried out similarly drilled with carbon dioxide gas laser without the use of auxiliary materials on the front surface, the hole is not red It was.
[0029]
Comparative Example 2
In Example 2 (FIG. 3 (1)), using a mechanical drill with a drill diameter of 100 μm, 63,000 holes were similarly drilled from the surface layer to the copper foil immediately below. The entire cross section of the hole was confirmed, and 13% of the holes as shown in FIG. The others stopped through the inner layer copper foil. After performing the desmear process once without performing the SUEP process, a printed wiring board was produced in the same manner. The evaluation results are shown in Table 1.
[0030]
Comparative Example 3
Using the double-sided copper-clad multilayer board of Example 2, the copper foil on this surface was etched by opening 63,000 holes with a diameter of 100 μm at 400 μm intervals, and 3 pulses with carbon dioxide energy of 18 mJ / pulse. Opened. Without performing the SUEP process, a known desmear process was repeated twice, similarly, 15 μm of copper plating was applied, circuits were formed on the front and back, and processed in the same manner to produce a printed wiring board. The evaluation results are shown in Table 1.
[0031]
Comparative Example 4
In Example 2, via holes were similarly drilled in the double-sided copper-clad multilayer board at 4 pulses with a carbon dioxide laser output of 40 mJ / pulse (FIGS. 4 (1) and (2). This is the center of the inner copper foil. (Fig. 4 (3)), this was subjected to SUEP treatment, similarly plated (Fig. 5 (4)), and a printed board was produced.
[0032]

[0033]
<Measurement method>
1) The bottom section of the via hole was observed.
2) Via drilling time Shown is the time required to drill 63,000 holes / plate when drilling with a carbon dioxide laser and mechanical drill.
3) Circuit pattern cuts and shorts In the examples and comparative examples, the line / space = 50/50 μm pattern was observed with 200 magnifiers with a magnifying glass, and the total of the pattern cuts and shorted patterns is shown in the molecule. It was.
4) Measured by the glass transition temperature DMA method.
5) Via hole heat cycle test Two via holes were alternately connected on the front and back, and one cycle was performed 200 cycles at 260 ° C, solder, immersion 30 seconds → room temperature, 5 minutes, and showed the maximum resistance change. .
[0034]
【The invention's effect】
When a micro via hole for conducting electrical conduction between the copper foil in the surface layer of the printed wiring board and the copper foil in the via hole is made with a carbon dioxide laser, a part of the copper layer on the bottom of the via hole And a via hole is formed so as not to penetrate the copper foil, and a via hole having a structure in which the outermost layer and the copper layer of the via portion are electrically conductive is formed by metal plating or conductive paint. As a result, there was no need for desmear treatment, and it was possible to obtain an excellent connection reliability between the outermost layer and the copper layer exposed in the via portion. In addition, the machining speed is much faster than drilling, and productivity can be greatly improved. The copper foil is thinned by etching away the copper foil burrs and the surface of the copper foil that has been pierced in the copper foil perforated part in the thickness direction simultaneously with a chemical solution in the thickness direction. In the formation of thin wire circuits of the front and back copper foils obtained in this way, it was possible to produce a high-density printed wiring board without occurrence of defects such as short-circuiting or pattern breakage.
[Brief description of the drawings]
FIG. 1 is a process diagram of via drilling [(1), (2), (3)] using a carbon dioxide laser in Example 2.
FIG. 2 is a process diagram of deburring (4) and copper plating (5) by SUEP in Example 2.
3 is a similar process diagram using a carbon dioxide laser in Comparative Example 2. FIG.
4 is a process diagram of via drilling [(1), (2), (3)] by a carbon dioxide gas laser of Comparative Example 4. FIG.
FIG. 5 is a process diagram of copper plating (4) of Comparative Example 4;
[Explanation of symbols]
a metal powder-containing resin sheet b copper foil c glass cloth base thermosetting resin layer d 40 mJ / pulse carbon dioxide laser e generated burr f 30 mJ / pulse carbon dioxide laser g copper foil surface layer h at the bottom of the via hole h via hole Copper plated part i Mechanical drill j Hole penetrated into the 4th layer (lower outer copper foil) k Place penetrated through the inner copper foil with high-power carbon dioxide laser

Claims (1)

Copper having at least two or more copper layers when a micro-via hole for conducting conduction between the first copper foil on the surface of the printed wiring board and the copper foil in the via portion is formed with a carbon dioxide gas laser. on the surface layer copper foil-clad board, in melting point 900 ° C. or higher, and bond energy 300 kJ / mol or more metal compounds powder, water-soluble, including one carbon powder or a metal powder or two or more of 3 to 97 volume% The resin composition is arranged in the form of a coating film or sheet, and a carbon dioxide laser is irradiated at an output of 20 to 60 mJ / pulse to remove at least the first copper foil layer of the via hole, and then 20 to 35 mJ / pulse. At the output, a part of the copper foil surface layer which becomes the bottom of the via hole is processed and removed to form a via hole without penetrating the copper foil, and then the copper foil burrs protruding from the via hole and the copper foil are removed. of a part in the thickness direction planar removed performed simultaneously with the etching process, and the metal main Method of forming a via hole, which comprises conducting conduction between copper foil layer of the outermost layer and the via hole in the key or the conductive paint.

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