JP2003218539A - Method of forming through hole through multilayered double-sided copper-clad board with laser beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form through holes having good small shapes through a multi-layered double-sided copper-clad board in a high-density pattern by directly projecting a laser beam upon the board. <P>SOLUTION: In a method of forming through holes through multilayered double-sided copper-clad board, through holes having diameters of 30-80 μm are formed through the multilayered double-sided copper-clad board from both sides of the board by using a UV laser. In the method, holes are formed halfway through an outer copper foil, an insulating layer, and inner copper foil in the thickness direction by directly projecting a laser beam upon the copper foil from one side of the board, and then, holes are made from the opposite side again by directly projecting the laser beam upon the board from the same position on the opposite side. In addition, through holes having diameters of 80-180 μm are formed through the board by means of a carbon dioxide laser and, when the copper foil is thick, the copper foil is made thinner by etching off a part of the foil in the thickness direction and, at the same time, the burrs of the inner and outer copper foil of the board formed in the hole sections are removed by melting. A multilayered printed board is obtained by using the multilayered double-sided copper-clad board having the through holes thus formed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method of directly irradiating a UV (excimer, YAG) laser and / or a carbon dioxide gas laser from the front and back surfaces of a copper foil of a multilayer double-sided copper clad plate to form a through hole. The double-sided copper clad board having the through holes thus obtained is used as a new semiconductor plastic package, a mother board, etc. as a high-density small printed wiring board having holes of small diameter.

[0002]

2. Description of the Related Art Conventionally, in a high-density multilayer printed wiring board used for a semiconductor plastic package or the like, a through hole for a through hole is formed by a metal drill. 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 holes with such small diameters, the drill diameter is small, so the metal drill bends, breaks, and processing speed. However, there are drawbacks in productivity, reliability, etc.

Further, when forming through holes for through holes, holes of the same size are previously formed in the upper and lower copper foils by using a negative film in a predetermined method, and the through holes are vertically penetrated by a carbon dioxide laser. However, there is a defect that the upper and lower holes are misaligned and it is difficult to form the land.

On the other hand, there is a method in which the surface of the copper foil is treated, and then the copper foil is directly perforated with a carbon dioxide gas laser to form a through hole, but the thickness of the copper clad laminate is 1.0 mm. If it exceeds the above range, the number of laser shots increases and the hole shape becomes larger on the irradiation side.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for solving the above problems and forming a through hole for a through hole having a uniform hole shape of a multilayer double-sided copper clad board and having a good diameter. is there.

[0006]

A multi-layer double-sided copper clad board with 30-18
In the method of making a through hole of 0 μm, laser is directly irradiated onto the copper foil from one side of the multi-layer double-sided copper clad board, the outer copper foil and the insulating layer are through-hole processed, and a hole is further formed in a part of the inner copper foil. After forming, by forming a through hole through the outer layer copper foil, the insulating layer and the inner layer copper foil by irradiating the laser again from the same position on the opposite side, the hole shape of a particularly thick multilayer copper clad plate is good. Things are obtained.

A through hole having a diameter of 30 μm or more and less than 80 μm can be opened by a UV laser, and a through hole of 80 μm or more and 180 μm or less can be formed by a carbon dioxide laser. Alternatively, the copper foil can be processed with a UV laser, and then a carbon dioxide laser can be used to make holes.

When a carbon dioxide laser is directly irradiated onto a thick outer layer copper foil to form a through hole, a burr of the copper foil occurs around the hole. This outer layer copper foil burr can be removed by mechanical polishing, but in order to completely remove the burr, both surfaces of the copper foil should be planarized in the thickness direction so that a part of the original copper foil has a flat thickness. At the same time as the etching removal, it is preferable to remove the inner and outer layer copper foil burrs overhanging the holes as well.By forming a through hole in which the copper foil around the hole remains, the connection reliability is excellent and the through hole is Since it can be formed without bending and the outer layer copper foil becomes thin, defects such as shorts and pattern breaks may occur in the circuit formation of the fine wire of the front and back copper foil obtained by plating up with the subsequent metal plating. Without, it is possible to create a high-density printed wiring board. In addition, the processing speed was remarkably faster than that obtained with a drill, the productivity was good, and the economy was excellent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a laser to
Regarding the method of making a small diameter and good shape through hole in a multilayer double-sided copper clad board with more than one copper layer, use UV laser to make holes directly from the copper foil, or use carbon dioxide laser. Place an auxiliary material for drilling on the surface of the outer copper foil, use a copper foil treated with nickel and / or cobalt alloy, or treat the copper foil surface with black copper oxide treatment, chemical treatment, etc. Or, use a thin copper foil, irradiate a laser beam directly on this copper foil to penetrate the outer copper foil and the insulating layer, and process a part of the inner copper foil. The multilayered double-sided copper clad plate is turned upside down and a laser beam is similarly irradiated from the opposite side to penetrate the outer layer copper foil, the insulating layer and the inner layer copper foil to form a through hole. When drilling with a carbon dioxide laser, if the copper foil is thick, burr of the copper foil will occur in the formed hole, but this inner and outer layer burr is etched away with a chemical solution and at the same time a part of the front and back copper foil in the thickness direction Are removed by etching. Due to this thinning of copper and deburring, in the subsequent copper plating, there is no overhang due to the plating of the holes, the total thickness of the front and back copper foil after plating can be kept thin, and a suitable one for fine pattern formation can be obtained. A high-density printed wiring board can be manufactured.

In the drilling of a copper clad laminate with a carbon dioxide gas laser, one of a metal oxide powder, carbon or metal powder having a melting point of 900 ° C. or more and an atomic binding energy of 300 kJ / mol or more is formed on the surface to be irradiated with laser. Or a mixture of two or more kinds and a resin such as a water-soluble resin is applied to the surface of the copper foil and dried to form a coating film, or it is adhered to one surface of the thermoplastic film to assist drilling. The material is placed and preferably adhered to the copper foil surface, and the carbon dioxide gas laser is directly radiated onto the surface of the material to process and remove the copper foil. In addition, on the shiny surface of the copper foil, a copper clad plate is prepared using a copper foil having a nickel metal layer, a cobalt metal layer, and an alloy layer thereof, and a carbon dioxide laser is directly irradiated onto the copper clad plate to reduce the diameter of the copper foil. The holes can be formed in the outer layer. Furthermore, the copper foil surface of a copper clad plate overlaid with a general copper foil is treated with black copper oxide treatment, or the copper foil surface is treated with a chemical solution to form fine irregularities, and then carbon dioxide is directly applied. Through holes can be formed in the outer layer copper foil by irradiating with a gas laser. After that, the insulating layer is processed, and further, a part of the inner layer copper foil in the thickness direction is processed to make a hole, and then the multilayer double-sided copper clad plate is turned over and similarly made to form a through hole.

Among the auxiliary materials used in the present invention, the melting point of 90
As the metal compound having a binding energy of 300 kJ / mol or more at 0 ° C. or higher, generally known compounds can be used. Specifically, as the oxide, titania such as titanium oxide, magnesia such as magnesium oxide, iron oxide such as iron oxide, nickel oxide such as nickel oxide, zinc oxide such as manganese dioxide and zinc oxide. , Silicon dioxide, aluminum oxide, rare earth oxides, cobalt oxides such as cobalt oxide, tin oxides such as tin oxide, and tungsten oxides such as tungsten oxide. Examples of the non-oxide include generally known ones such as silicon carbide, tungsten carbide, boron nitride, silicon nitride, titanium nitride, aluminum nitride, barium sulfate, and rare earth oxysulfide. In addition, carbon can also be used. Further, various kinds of glass which are a mixture of the metal oxide powder can be mentioned. Further, carbon powder may be mentioned, and further, simple substances such as silver, aluminum, bismuth, cobalt, copper, iron, magnesium, manganese, molybdenum, nickel, palladium, antimony, silicon, tin, titanium, vanadium, tungsten, zinc, or the like. The metal powder of the alloy is used. These are used alone or in combination of two or more. The average particle size is
Although not particularly limited, it is preferably 1 μm or less.

It is preferable that the metal is attached to the hole wall or the like and does not adversely affect the semiconductor chip, the adhesion to the hole wall, etc., because the molecule dissociates into atoms upon irradiation with the carbon dioxide laser. Since Na, K, Cl ions, etc., particularly adversely affect the reliability of the semiconductor, those containing these components are not suitable. The compounding amount is 3 to 97% by volume, preferably 5 to 95% by volume.
Is mixed with the water-soluble resin and uniformly dispersed.

The resin in the auxiliary material is not particularly limited,
A water-soluble resin is preferable because it needs to be removed when attached after processing. The water-soluble resin is not particularly limited, but is selected so that it does not peel off when kneaded, applied to the surface of the copper foil, dried, or formed into a sheet.
For example, generally known substances such as polyvinyl alcohol, polyester, polyether polyol, polyethylene oxide, starch and the like are used.

The method of preparing a composition comprising a resin and one or more of metal compound powder, carbon powder, or metal powder is not particularly limited, but the composition is kneaded in a solvent-free manner at a high temperature to obtain thermoplasticity. A method of extruding and adhering in a sheet form on a film, dissolving a water-soluble resin in water or a water-soluble organic solvent, adding the above powder to this, uniformly stirring and mixing, and using this, a thermoplastic film as a paint A generally known method can be used, such as a method of forming a film by coating on the surface and drying. The thickness is not particularly limited, but when applied, it is 20 to
200 μm, when applied to a thermoplastic film, the total thickness including film is 30 to 200 μm.

The carbon dioxide laser is in the infrared wavelength range.
Wavelengths of 9.3 to 10.6 μm are commonly used. Energy is
The copper foil is processed by pulse oscillation at 5 to 60 mJ, preferably 7 to 50 mJ, and holes are drilled. Energy is processed on the surface copper foil,
It is appropriately selected depending on the thickness of the copper foil. The UV / YAG laser generally has a wavelength of 200 to 400 nm.

The multilayer copper-clad board used in the present invention is a multilayer double-sided copper-clad board having three or more copper layers. The thermosetting resin multilayer double-sided copper-clad laminate is made of an inorganic or organic base material. Known thermosetting multilayer double-sided copper clad laminate, a copper foil sheet with a resin on the surface layer or inside, a multilayered plate using a film, etc., a multilayered copper clad plate of generally known constitution, a polyimide film, a polyester film, polyparabanic acid A copper clad plate as a base material such as a film may be used.

In the base material reinforced multilayer double-sided copper clad laminate, a reinforcing base material is first impregnated with a thermosetting resin composition and dried to prepare a B stage to prepare a prepreg. Next, a predetermined number of the prepregs are stacked, a copper foil is arranged on the outer side of the prepregs, and laminated under heat, pressure, and preferably under vacuum to form a copper-clad laminate. The type of copper foil is not particularly limited, but electrolytic copper foil is preferably used. The thickness of the inner layer copper foil is preferably 12 to 35 μm. If necessary, a through hole is opened in this copper-clad laminate with a mechanical drill, laser, etc., and after the desmear treatment, the copper foil surface is subjected to a chemical treatment such as black copper oxide treatment, and prepreg, B stage resin sheet, etc. are placed on both sides. , A copper foil is placed on the outer side thereof, or a B-stage resin sheet with a copper foil is placed on both sides of the inner layer board, and laminated under heat, pressure and preferably under vacuum to form a multilayer double-sided copper clad laminate. . The thickness of the outer layer copper foil is preferably 3 to 12 μm. In addition, general metal foils such as nickel foil and alloy foil can also be used.

As the substrate, generally known organic and inorganic woven fabrics and nonwoven fabrics can be used. Specific examples of the inorganic fiber include E, S, D, M and NE glass fibers. Examples of the organic fiber include generally known fibers such as wholly aromatic polyamide and liquid crystal polyester. These may be mixed papers. Moreover, a film base material can also be used.

As the resin of the thermosetting resin composition used in the present invention, generally known thermosetting resins are used. Specifically, epoxy resin, polyfunctional cyanate ester resin, polyfunctional maleimide-cyanate ester resin, polyfunctional maleimide resin, unsaturated group-containing polyphenylene ether resin and the like, one kind or two or more kinds. Are used in combination. A thermosetting resin composition having a glass transition temperature of 150 ° C. or higher is preferable from the viewpoint of through-hole shape in processing by high-power carbon dioxide laser irradiation, and moisture resistance, migration resistance, electrical characteristics after moisture absorption, etc. From this point of view, a polyfunctional cyanate ester resin composition is preferable.

The polyfunctional cyanate ester compound which is a suitable thermosetting resin component of the present invention is a compound having two or more cyanato groups in the 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-
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) sulphone, tris (4-cis) Anatophenyl) phosphite, tris (4-cyanatophenyl) phosphate, and cyanates obtained by the reaction of novolac with cyanogen halide. These known Br addition compounds are also included.

In addition to these, Japanese Examined Patent Publications 41-1928 and 43-1846
8, polyfunctional cyanate ester compounds described in JP-A-51-63149 and JP-A-44-4791, JP-A-45-11712, JP-A-46-41112 and JP-A-47-26853 can also be used. Further, a prepolymer having a molecular weight of 400 to 6,000 and having a triazine ring formed by trimerizing the cyanato group of these polyfunctional cyanate ester compounds is used. This prepolymer is obtained by polymerizing the above-mentioned polyfunctional cyanate ester monomer using, for example, acids such as mineral acid and Lewis acid; bases such as sodium alcoholate and tertiary amines; salts such as sodium carbonate as a catalyst. It is obtained by The prepolymer also contains some unreacted monomer and is in the form of a mixture of the monomer and the prepolymer. Such a raw material is suitably used for the purpose of the present invention. Generally, it is used by dissolving it in a soluble organic solvent.

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 reacting a hydroxyl group-containing silicone resin with epohalohydrin. Moreover, these well-known Br addition resin is mentioned. These may be used alone or in combination of two or more.

As the polyimide resin, a generally known one can be used. Specific examples thereof include reaction products of polyfunctional maleimides and polyamines, and polyimides 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 combination as appropriate in consideration of the balance of properties.

Various additives may be added to the thermosetting resin composition of the present invention as desired, as long as the original properties of the composition are not impaired. These additives include polymerizable double bond-containing monomers such as unsaturated polyester and prepolymers thereof; polybutadiene, epoxidized butadiene, maleated butadiene, butadiene-
Low molecular weight liquid to high molecular weight elastic rubbers such as acrylonitrile copolymer, polychloroprene, butadiene-styrene copolymer, polyisoprene, butyl rubber, fluororubber, natural rubber; polyethylene, polypropylene, polybutene, poly-4-methyl Penten, polystyrene, AS
Resin, ABS resin, MBS resin, styrene-isoprene rubber,
Acrylic rubber, these core shell rubber, polyethylene
-Propylene copolymers, 4-fluorinated ethylene-6-fluorinated ethylene copolymers; high molecular weight prepolymers or oligomers such as polycarbonate, polyphenylene ether, polysulfone, polyester, polyphenylene sulfide; polyurethane and the like are used as appropriate. To be done. In addition, other known organic and inorganic fillers, dyes, pigments,
Various additives such as a thickener, a lubricant, an antifoaming agent, a dispersant, a leveling agent, a photosensitizer, a flame retardant, a brightening agent, a polymerization inhibitor, and a thixotropic agent are appropriately combined and used as desired. To be In particular, since the resin processing speed is higher than that of the base material for forming holes with a laser, generally known inorganic fillers are added in an amount of 10 to 90% by weight, preferably 20 to 80% by weight, in order to improve the shape of the holes. Is preferred. Further, if necessary, the compound having a reactive group is appropriately mixed with a curing agent and a catalyst.

The thermosetting resin composition of the present invention itself is cured by heating, but the curing rate is slow and the workability and economy are poor. Therefore, the known thermosetting catalyst 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, based on 100 parts by weight of the thermosetting resin.

The lamination conditions for the copper clad laminate are not particularly limited, but generally the temperature is 100 to 280 ° C, preferably 120 to 250 ° C.
The pressure is generally 5 to 50 kgf / cm ² , preferably 10 to 30 kgf / cm ^2.
Then, it is preferable to laminate-mold under a vacuum.

When a through hole is formed by irradiating a carbon dioxide laser with pulse oscillation at an output of 5 to 60 mJ, for example, 7 μm
With the above thick copper foil, burrs are generated around the holes. Therefore, after the carbon dioxide laser irradiation, both surfaces of the copper foil are planarly etched in the thickness direction, preferably with a chemical solution, and a part of the original metal foil is removed to simultaneously remove burrs. The removed and thinned copper foil obtained is suitable for forming a fine pattern, and forms a through hole in which the copper foil around the hole suitable for a high-density printed wiring board remains. In this case, etching is more preferable than mechanical polishing from the viewpoints of removing burrs from the holes and changing the dimensions due to polishing.

Burrs may also be generated by the UV laser, and these burrs can be removed by the same method.

A combination of a UV laser and a carbon dioxide laser can also be used in forming the holes.

The method for etching away the copper burrs generated in the holes of the present invention is not particularly limited, but for example, JP-A-02-22887, 02-22896, 02-25089, 02-2.
5090, 02-59337, 02-60189, 02-166789, 03-25
995, same 03-60183, same 03-94491, same 04-199592, same 04-263
Method for dissolving and removing metal surfaces with chemicals disclosed in 488
(Called the SUEP method). Etching rate is 0.02
Perform at ~ 1.0 μm / sec. Further, a method in which a chemical solution is sucked through the through holes to remove the inner layer copper foil burr by etching is also suitably used.

[0031]

The present invention will be specifically described below with reference to Examples and Comparative Examples. Unless otherwise specified, “part” means part by weight. Example 1 900 parts of 2,2-bis (4-cyanatophenyl) propane, bis (4-
Maleimide phenyl) 100 parts of methane is melted to 150 ℃,
The reaction was carried out for 4 hours with stirring to obtain a prepolymer. This was dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide. In addition to this, bisphenol A type epoxy resin (trade name: Epicoat 1001, Yuka Shell Epoxy Co., Ltd.)
400 parts of cresol novolac type epoxy resin (trade name: ESCN-220F, manufactured by Sumitomo Chemical Co., Ltd.) were added and uniformly mixed. Furthermore, zinc octylate 0.4 as a catalyst
2000 parts of an inorganic filler (trade name: calcined talc, manufactured by Nippon Talc Co., Ltd.) was added, and the mixture was stirred and mixed uniformly to obtain a varnish A. This varnish was impregnated into a glass woven cloth with a thickness of 100 μm and dried at 150 ° C, and the gelling time (at 170
(° C) for 120 seconds, a prepreg having a thermosetting resin composition content of 47% by weight (prepreg B) and a prepreg having a thermosetting resin composition content of 58% by weight (prepreg C) were prepared.
Electrolytic copper foil with a thickness of 25 μm is placed above and below the above six prepregs B and placed under a vacuum of 200 ° C, 20 kgf / cm ² , 30 mmHg or less.
Time-wise lamination molding was performed to obtain a double-sided copper-clad laminate D having an insulating layer thickness of 0.6 mm. Through holes were carefully drilled one by one with a mechanical drill having a diameter of 0.5 mm at the positions of the target marks at the four corners of each printed wiring board within the working size of the double-sided copper-clad laminate D. A baking film was put in the through holes for target marks at the four corners to form a pattern by a conventional method. After this inner layer copper foil is subjected to black copper oxide treatment, one prepreg C is placed on each side and the thickness is 12 μm on the outside.
The electrolytic copper foil of was placed and laminated in the same manner to produce a 4-layer double-sided copper clad laminate. The copper foil above the target mark is removed by etching with a diameter of 3 mm, and the 4-layer double-sided copper-clad laminate E
And

On the other hand, 800 parts of black copper oxide powder (average particle diameter: 0.8 μm) as a metal powder was added to a varnish prepared by dissolving polyvinyl alcohol powder in water, and uniformly mixed by stirring (varnish F). This is coated on one side of a 25 μm thick polyethylene terephthalate film so that the thickness is 60 μm,
After drying at 110 ° C. for 30 minutes, auxiliary material G having a metal compound content of 65% by volume was formed. Auxiliary material G is placed on the front and back of the above-mentioned multilayer double-sided copper clad laminate E so that the resin surface faces the copper foil side so as not to cover the target marks at the four corners, and the temperature is 100 ° C.
The rolls were laminated at a linear pressure of 5 kgf / cm and adhered. Read the target marks at the four corners of the inner layer board with a CCD camera and set the distance from the surface of this multilayer double-sided copper clad laminate.
900 holes with a diameter of 120 μm and a diameter of 1 mm were directly irradiated with 3 shots with a pulse energy of 28 mJ by using a carbon dioxide laser, and 70 blocks were penetrated through the outer copper foil and 40 to 80% of the inner copper foil was processed. Next, this was turned upside down, and a 120 μm hole was irradiated at the same position on the back surface for 4 shots with the same energy to penetrate through the outer layer and the inner layer copper foil to form a hole. This deviation in hole position was less than 5 μm. By the SUEP method, the chemical solution was sucked into the inside of the holes to dissolve and remove the copper foil burr generated around the inner and outer layer holes, and at the same time, the surface copper foil was also dissolved to 4 μm. Copper plating is 15μm on this plate by the usual method (total thickness: 1
9 μm). All the copper foil for land around this hole remained.

Patterns (200 lines / space = 50/50 μm), solder ball lands, etc. are formed on the front and back by an existing method, and at least the semiconductor chip portion, the bonding pad portion, and the solder ball pad portion are formed. Except for this, it was covered with a plating resist and plated with nickel and gold to prepare a multilayer printed wiring board. Table 1 shows the evaluation results of this multilayer printed wiring board.

Example 2 700 parts of epoxy resin (trade name: Epicoat 5045), 300 parts of epoxy resin (trade name: ESCN220F), dicyandiamide 35
And 1 part of 2-ethyl-4-methylimidazole were dissolved in a mixed solvent of methyl ethyl ketone and dimethylformamide, 800 parts of the calcined talc of Example 1 was further added, and the mixture was forcibly stirred and uniformly dispersed to obtain a varnish. This was impregnated into a glass woven fabric having a thickness of 100 μm and dried, and a gelling time of 150 seconds, a thermosetting resin composition content of 48 wt% prepreg (prepreg H) and a thermosetting resin composition content of 57 wt% % Prepreg (prepreg I) was prepared. Eight pieces of this prepreg H are used, and electrolytic copper foil with a thickness of 18 μm is placed on both sides, 190 ° C, 20 kgf / cm ² , 30
Double-sided copper-clad laminate J after laminated molding for 2 hours under vacuum below mmHg
Was produced. A pattern is formed on the surface of this copper foil, and chemical treatment (Mech treatment: CZ8100 + CL8300E treatment, copper foil surface unevenness 3
, and then place one prepreg I on each side, and place a 12 μm thick electrolytic copper foil with a cobalt alloy treatment on the copper foil shiny surface on both sides, and laminate and mold in the same manner. A four-layer double-sided copper clad laminate K was produced.

The front and back copper foil on the surface of the target mark formed on the inner layer plate of this multilayer double-sided copper-clad laminate K was removed by etching with a diameter of 2 mm so that the target mark could be read from the surface. Read the target mark formed on the inner layer with a CCD camera from this surface, irradiate 2 shots with carbon dioxide laser energy of 17 mJ from the surface to penetrate the outer copper foil, and further process 40 to 70% of the inner copper foil. Then, turn over this multilayer double-sided copper clad laminate, read the target mark formed on the inner layer with a CCD camera in the same way, and irradiate 6 shots with the energy of 17 mJ from the copper foil on the back at the same position to the outer layer copper foil and insulation. The layers were processed and perforated and perforated. The maximum positional deviation was 7 μm. Using this,
Similarly, a multilayer printed wiring board was used. The evaluation results are shown in Table 1.

Example 3 The copper foils on the front and back sides of the multilayer double-sided copper clad laminate E of Example 1 were etched to a thickness of 4 μm. Directly on this surface U with a wavelength of 355 nm
Irradiate 250 shots of V-YAG laser to process about 67% of outer layer copper foil, insulation layer and inner layer copper foil, open a hole with a hole diameter of 50 μm halfway, and turn it over again and similarly irradiate 260 shots from the other side. Then, a 50 μm through hole was formed. After the desmear treatment, copper plating was adhered to 15 μm to obtain a multilayer printed wiring board in the same manner. The evaluation results are shown in Table 1.

Comparative Example 1 Using the multilayer double-sided copper clad laminate E of Example 1, without using a backing sheet on the lower surface, the copper clad board was slightly floated to form an air layer on the lower surface, and 12 shots were made with carbon dioxide laser energy of 35 mJ. When irradiation was performed to form a through hole, the shape of the hole around the inner layer copper foil became large, and processing chips adhered to the periphery of the pilot hole. SU
EP treatment was performed to obtain a multilayer printed wiring board in the same manner. The evaluation results are shown in Table 1.

Comparative Example 2 A hole diameter of 120 is provided in the inner layer of the double-sided copper-clad laminate J of Example 2.
A μm hole was etched by a conventional method to form a pattern at the same time. After this copper foil surface is subjected to black copper oxide treatment, one prepreg I is placed on each side of the copper foil, and a general 12 μm electrolytic copper foil is placed on the outside of the prepreg I, and laminated molding is performed under the same conditions as in Example 2. A four-layer double-sided copper clad laminate was obtained. The copper foil of the inner layer has a hole diameter of 120 μm, and the surface copper foil is etched by a conventional method at a diameter of 120 μm at the same place where the hole having a hole diameter of 120 μm is formed. It was Desmear treatment is applied, SUEP treatment is not applied, copper plating is applied to 15 μm, and patterns are formed on the front and back sides.
Similarly, a multilayer printed wiring board was prepared. Table 1 shows the evaluation results
Shown in.

Comparative Example 3 The multilayer double-sided copper clad laminate E of Example 1 was used, and a thickness of 10
A 0 μm aluminum foil was placed, a 1.6 mm-thick paper phenol plate was placed on the back surface, and a through hole was made with a mechanical drill having a diameter of 120 μm. After desmearing, copper plating was adhered to a thickness of 15 μm to obtain a multilayer printed wiring board in the same manner. The evaluation results are shown in Table 1.

(Table 1) Item Example Comparative Example 1 2 3 1 2 3 Deviation between front and back hole positions (μm) 5 7 5 <5 21 38 Deviation between hole wall and inner layer copper foil (μm) 0 0 0 0 16 0 Hole shape Almost circular Almost circular Almost irregular Irregular irregular Almost circular Pattern breaks and shorts (pieces) 0/200 0/200 0/200 12/200 51/200 47/200 Land peripheral copper foil missing None None None None None Yes None Glass transition temperature (℃) 235 160 235 235 235 160 235 Through hole heat cycle test (%) 2.9 4.0 2.7 17.5 27.0 2.8

<Measurement method> 1) Misalignment of front and back hole positions and misalignment of surface hole and inner layer hole position Work size 250 mm square, 70 through holes with 900 through holes / block (total 63,000 holes) were created. The maximum deviation of the hole position between the front and back and the hole wall and the inner layer copper foil was measured. 2) Pattern break and short circuit After creating a comb-shaped pattern with line / space = 50/50 μm using the copper clad plate with holes that was made and copper plating adhered to it in Examples and Comparative Examples. The 200 patterns after etching were visually observed with a magnifying glass, and the total number of broken and short patterns was shown in the molecule. 3) Glass transition temperature Measured by the DMA method of JIS C6481. 4) Through-hole / heat cycle test A land diameter of 200 μm was created in each through-hole, 900 holes were connected alternately on the front and back sides, and one cycle was 260 ° C / solder / immersion.
200 cycles were carried out from 30 seconds to room temperature for 5 minutes, and the maximum rate of change in resistance was shown. 5) Cutting of copper foil around the land After SUEP, it was observed whether the copper foil remained around the hole.

[0042]

EFFECT OF THE INVENTION A method of forming a through hole of 30 to 180 μm on a multilayer double-sided copper clad plate from both sides, and irradiating a laser directly on the copper foil from one side of the multilayer double-sided copper clad plate to form an outer layer copper foil and an insulating layer. And after forming a hole to a part of the thickness direction of the inner layer copper foil, irradiate the laser again from the same position on the opposite side, the hole diameter of the hole is 30
80 μm through holes with a diameter of 80 μm or more
By opening a through hole of m or more and 180 μm or less with a carbon dioxide gas laser, there is no need to remove the copper foil by etching in advance, there is almost no deviation of the hole position on the front and back of the copper clad plate, and a through hole with a good shape is formed. It is workable, and both surfaces of the copper foil are planarly etched in the post-treatment to remove the thickness of part of the original copper foil by etching, so that the burr of the copper foil generated in the holes at the same time. Can be removed by etching, and even in the pattern 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 defects such as shorts and pattern breaks, and it has excellent reliability. I was able to get what I had.

[Brief description of drawings]

FIG. 1 is a through-hole forming process of the second embodiment (first half).

FIG. 2 is a through-hole forming process of the second embodiment (second half).

FIG. 3 is a through-hole forming step of Comparative Example 2.

[Explanation of symbols]

a Inner-layer double-sided copper-clad laminate b One printed wiring board c Target mark (alignment mark) formed on the inner-layer board with a mechanical drill d Cross-section view e Land of the through-hole forming area of the inner-layer board f Pattern making area g Inner layer Insulation layer h Part laminated and formed with prepreg i Cobalt alloy treated outer layer copper foil j Inner layer copper foil with the copper foil in the part to be pre-drilled removed by etching k CCD camera l Etching the outer layer copper foil on the target mark Removed part m Target mark of inner layer of 4-layer copper clad laminate n Outer layer copper foil burr generated by carbon dioxide laser drilling o Part of inner layer copper foil processed by carbon dioxide laser drilling p Inner layer copper foil Hole penetrated halfway q Inside out copper foil that is thinly etched with SUEP s SUEP with inner layer copper that is turned inside out and a carbon dioxide laser is irradiated from the opposite side Burr portion t Outer copper foil burr portion removed by etching with SUEP u Copper-plated surface copper foil portion and through hole portion v Pattern formed on outer layer w Outer layer copper foil portion previously removed by etching x General electrolytic copper foil y Through hole Area where holes of the same size are formed by etching the inner copper foil of the outer copper foil previously removed by etching z A gap between the hole wall and the outer copper foil created when a through hole was opened with a carbon dioxide laser α Gap between the inner wall and the inner wall of the hole created when a through hole was opened with a carbon dioxide laser

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Taro Yoshida             6-1, 1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi tile             The chemical company Tokyo factory F-term (reference) 4E068 AA05 AF01 AF02 AJ04 CA01                       CA04 CA08 DA11 DB14                 5E346 AA42 CC08 CC09 CC32 DD02                       FF03 GG15 HH32

Claims (3)

[Claims] 1. A method of forming a through hole of 30 to 180 μm on both sides of a multilayer double-sided copper clad board by directly irradiating a laser onto the outer side copper foil from one side of the multilayer double-sided copper clad board to form an outer layer copper foil and an inner layer. After forming a hole in a part of the copper foil, laser is irradiated again from the same position on the opposite side to process the outer layer copper foil and the inner layer copper foil to form a through hole. Method for forming through-holes in copper-clad plate 2. The multilayer double-sided copper-clad sheet according to claim 1, wherein a through hole having a hole diameter of 30 μm or more and less than 80 μm is opened by a UV laser, and a through hole of 80 μm or more and 180 μm or less is formed by a carbon dioxide gas laser. Through-hole forming method. 3. A carbon dioxide laser is directly irradiated onto a copper foil to form a through hole, and then burrs of the inner and outer copper foils generated around the hole are dissolved and removed by a chemical solution, and at the same time, thickness directions of the front and back copper foils are removed. 3. A method of forming a through hole in a multilayer double-sided copper clad board according to claim 1 or 2, wherein a part of the above is melted.