JP2003290958A - Method for forming through-hole to multilayered both- side copper clad plate by laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a method for boring through-holes of 30 to 180 μm in hole diameter by directly irradiating the surface of a multilayered both-side copper clad plate with a laser. <P>SOLUTION: First, the points to be bored with the through-holes of the inner layer substrate (a) are previously formed with holes (e) by etching copper foil (j) at the diameter smaller than the diameter of the through-holes and thereafter the multilayered both-side copper clad plate is manufactured by performing multilayer molding. The top of the outer layer copper foil (i) in the bored positions of the inner layer is directly irradiated with the laser to form the holes through the points formed with the holes by previously etching the copper foil of the outer layer copper foil (i), an insulating layer (h) and inner layer copper foil (j) and thereafter, the copper foil is again irradiated with the laser from the same position on the opposite surface and is worked in the same manner, by which the holes penetrating the front and rear are formed. Accordingly, the through-holes having a good hole shape and excellent reliability can be bored and the high-density printed wiring board which has through holes of small diameter and is formed with the fine and dense patterns can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of directly irradiating a UV (excimer, YAG) laser and / or a carbon dioxide laser from front and back copper foils of a multilayer double-sided copper clad board to form a through hole, The obtained double-sided multilayer copper clad plate having through holes,
As a high-density small printed wiring board with small diameter holes, it is used for new semiconductor plastic packages, motherboards, etc.

[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 less than 150 μmφ.When drilling such small holes, the drill diameter is thin, so the metal drill bends, breaks, and the processing speed is high. However, there were drawbacks such as slowness, and there were problems with productivity, reliability, etc.

When a through hole for a through hole is to be formed, holes of the same size are prepared in advance by using a negative film on the upper and lower copper foils, and the upper and lower sides are penetrated by a carbon dioxide laser. When a hole is to be formed, there is a defect that the positions of the upper and lower holes are displaced and the land is difficult to form.

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 laser to form through holes. Since the insulating layers have different degrees of processing, there are drawbacks such as non-uniform pore size.

[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 good hole shape in a multilayer double-sided copper clad board.

[0006]

A multi-layer double-sided copper clad board with 30-18
In the method of forming a through hole of 0 μm, laser is applied from one side of a multilayer double-sided copper clad plate prepared by using an inner layer plate in which a hole smaller than the through hole diameter is preliminarily etched at the place where the through hole of the inner layer copper foil is formed. After directly irradiating on the copper foil, after forming a hole through the outer layer copper foil, the insulating layer and the inner layer copper foil portion that has been pre-drilled, irradiate the laser again from the same position on the opposite side. By forming a through-hole through the outer-layer copper foil, the insulating layer and the inner-layer copper foil portion that has been pre-drilled,
In particular, a multilayer copper clad plate having a large number of inner copper foil layers and a good hole shape can be obtained.

The through holes having a diameter of 30 μm or more and less than 80 μm can be opened by a UV laser, and the through holes having a diameter of 80 μm or more and 180 μm or less can be formed by a carbon dioxide laser, but not limited to this. Also, the surface copper foil processing is performed with a UV laser,
After that, it can be processed by a method of making holes with a carbon dioxide laser. Other than that, it is possible to make holes with an arbitrary combination of a UV laser and a carbon dioxide laser.

When a through hole is formed by directly irradiating a thick copper foil with a carbon dioxide laser, after that, a burr of the copper foil occurs around the hole. This surface 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 It can be formed without bending, and since the surface 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 is much faster than that of a mechanical drill, the productivity is good, and the economy is excellent. Furthermore, it is possible to obtain a through hole with almost no hole position deviation between the front and back. did it.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a laser to
The present invention relates to a method for forming a through hole having a small diameter and a good shape in a multilayer double-sided copper clad board having at least two copper layers. Holes are directly drilled from the surface of the copper foil using a UV laser, the holes are made in the inner copper foil by etching, and the holes are pierced. A laser is directly irradiated on the copper foil to process the outer copper foil and the insulating layer to form a through hole.

Alternatively, by using a carbon dioxide laser, an auxiliary material for drilling is arranged on the surface of the copper foil on the surface layer, nickel and / or cobalt, or a copper foil which has been subjected to a known alloy treatment is used. Apply black carbon oxide treatment, chemical treatment, etc. on the foil surface, or use a thin copper foil and irradiate a carbon dioxide gas laser beam directly onto this copper foil to form an outer copper foil or insulating layer. And, after processing the inner layer copper foil at the location where holes have been made in the copper foil by etching in advance, turn over the multilayer double-sided copper clad plate and irradiate the same with a laser beam from the opposite side, the outer layer copper foil, A through hole is formed by penetrating the insulating layer and the inner copper foil portion where the copper foil has been previously etched to make a 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.

When drilling a multi-layer double-sided copper clad plate with a carbon dioxide gas laser, the surface irradiated with the laser has a melting point of 900
A coating that mixes at least one kind of metal oxide powder, carbon, or metal powder having an atomic binding energy of 300 kJ / mol or more with a resin such as a water-soluble resin at a temperature of ℃, is dried on the copper foil surface, and then is coated. Or, arrange the auxiliary material for perforation obtained by applying the above-mentioned paint to one side of the thermoplastic film, preferably adhered to the copper foil surface, and directly irradiate the surface with carbon dioxide gas laser. 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. The holes can be formed in the outer layer by irradiating with a gas laser. After that, the insulating layer is processed,
Further, the inner layer copper foil is subjected to perforation at a portion where a hole has been previously formed by etching to form a hole, and then the multilayer double-sided copper clad plate is turned upside down and similarly perforated to form a hole having front and back sides penetrating therethrough.

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.

Since molecules are dissociated into atoms by irradiation with a carbon dioxide laser, it is preferable that the metal does not adhere to the pore wall and the like and does not adversely affect the semiconductor chip, the adhesion to the pore wall and the like. 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 to be removed when it adheres after processing. The water-soluble resin is not particularly limited,
When kneading is applied to the surface of the copper foil, dried, or formed into a sheet, a material that does not peel off is selected. For example, generally known resins such as polyvinyl alcohol, polyester, polyether polyol, polyethylene oxide and starch are used.

The method for preparing a composition comprising a metal compound powder, carbon powder, or at least one kind of metal powder and a resin is not particularly limited, but it is kneaded at a high temperature in a solvent-free manner, and is kneaded on a thermoplastic film. A method of extruding and adhering to a sheet shape, dissolving a water-soluble resin in water or a water-soluble organic solvent, adding the above powder to it, stirring and mixing uniformly, and using this, coating it on a thermoplastic film as a paint A generally known method such as a method of drying to form a film can be used. The thickness is not particularly limited, but when it is directly applied to the surface copper foil, it is preferably 20 to 200 μm, and when it is applied to the thermoplastic film, the total thickness 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 laser is for irradiating a laser beam having a UV wavelength to make a hole, and the wavelength is not particularly limited.
Generally, wavelengths of 200-400 nm and 1.06 μm are used. Especially solid state UV lasers are used. In this method, the organic substance is processed by a mechanism of breaking the molecular bond constituting the organic substance without giving the influence of heat to the utmost. Carbon is not generated in the holes as compared with the carbon dioxide laser, and the holes are clean, so that the subsequent copper plating can be deposited with high reliability. Since the UV laser wavelength is short, it is also absorbed by copper, and by irradiating the laser directly on the copper-clad plate without using a hole-aiding material, holes can be made in the copper foil and even in the insulating layer. Is possible. The UV laser is not particularly limited, excimer laser, Nd-YAG
Known ones such as laser are used.

Target marks (also referred to as alignment marks) are formed in advance on at least three corners of the work size, preferably four corners or more, at the same position on the front and back sides of the inner layer or outer layer of the multilayer double-sided copper clad plate in which a laser through hole is formed. Keep it. More preferably, it is formed at each of the four corners of the printed wiring board with one imposition. By reading this target mark with a CCD camera and then making a hole, the hole forming position is accurate, and the through hole can be formed at the same position with almost no deviation between the front and back hole positions. The displacement of the through hole due to the displacement of the front and back holes inside the hole is about 5-10 μm, but due to the large diameter of the hole, there is no particular defective plating of the through hole.

The copper-clad board used in the present invention is a multi-layer double-sided copper-clad board having three or more copper layers, and known ones can be used. The thermosetting resin multilayer double-sided copper-clad laminate, inorganic, known thermosetting multilayer double-sided copper-clad laminate of an organic substrate, a copper foil sheet with a resin in the surface layer or inside, a multilayer plate using a film, etc. Multilayer copper clad plate of known configuration, also, a polyimide film, a polyester film, a polyparabanic acid film, a copper clad plate of a substrate such as a wholly aromatic polyamide film can be mentioned, but preferably dimensional shrinkage during lamination molding. A small substrate is 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 the prepreg is laminated under heat and pressure to form a copper-clad laminate. The type of copper foil is not particularly limited, but electrolytic copper foil is preferably used. A nickel foil, an alloy foil thereof, or the like can be used for this. The thickness of the inner copper foil is preferably 12 to 35 μm. In this copper clad laminate for the inner layer substrate, if necessary, a through hole is formed with a mechanical drill, a laser, etc., and the copper foil at the place where the through hole is formed during circuit formation after desmearing is smaller than the through hole diameter, preferably the through hole. Holes with a diameter of 50 to 80% are etched and opened, chemical treatment such as black copper oxide treatment is performed on the copper foil surface, prepreg, B stage resin sheet, etc. are placed on both sides, and copper foil is placed on the outside. Alternatively, the B-stage resin sheet with 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 5 to 12 μm. The outer layer is also a general metal foil,
For example, nickel foil or alloy foil can 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, generally known epoxy resin, polyfunctional cyanate ester resin, polyfunctional maleimide-cyanate ester resin, polyfunctional maleimide resin, unsaturated group-containing polyphenylene ether resin, and the like, 1 type Or 2
More than one type is used in combination. From the viewpoint of the through-hole shape in the processing by high-power carbon dioxide laser irradiation, a thermosetting resin composition having a glass transition temperature of 150 ° C. or higher is preferable, and further an inorganic filler is 10 to 80% by weight, preferably Is used in an amount of 15 to 60% by weight. A polyfunctional cyanate ester resin composition is preferable from the viewpoints of moisture resistance, migration resistance, electrical characteristics after moisture absorption, and the like.

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.

[0024] In addition to these, Japanese Patent Publications 41-1928 and 43-1846
8, the same 44-4791, the same 45-11712, the same 46-41112, the same 47-26853 and polyfunctional cyanate ester compounds described in JP-A-51-63149, cyanate polyphenylene ether resin may also be used. . Further, a mixture of a prepolymer and a monomer having a molecular weight of 400 to 6,000 and having a triazine ring formed by trimerization of cyanato groups of these polyfunctional cyanate 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. Polyepoxy compounds having epoxidized double bond thereof; polyol, polyglycidyl compounds obtained by reaction of hydroxyl group-containing silicone resins with epohalohydrin, and further epoxidized polyphenylene ether resin. In addition, these known Br
Examples include inclusions and phosphorus inclusions. These are 1 or 2
More than one type can be used in combination.

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.

Although these thermosetting resins can be used alone, it is preferable to use them in combination in consideration of the balance of properties.

Various additives can 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, in the case of forming holes with a laser, the processing speed of the resin is higher than that of the substrate. Therefore, it is preferable to add a generally known inorganic filler in order to improve the shape of the holes. If necessary, when a compound having a reactive group is added, a curing agent and a catalyst may be added appropriately.

The thermosetting resin composition of the present invention is itself cured by heating, but has a slow curing rate and is inferior in workability, economical efficiency and the like. Therefore, a 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 of 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 ^{2 to} 50 kgf / cm ² , preferably 5 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, when the thickness of the copper foil is as thick as 7 to 12 μm, burrs are generated around the hole. Therefore, after carbon dioxide laser irradiation, both surfaces of the copper foil are planarly etched in the thickness direction, preferably with a chemical solution,
By removing a part of the thickness of the original metal foil, burrs are also removed at the same time, and the thinned surface copper foil is suitable for forming a fine pattern, and a high-density printed wiring board can be manufactured. In this case, etching is better than mechanical polishing.
It is preferable 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 a similar method.

The method of etching away the copper burr 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 of spraying a chemical solution or sucking the inside of the through hole to remove the inner layer copper foil burr by etching is preferably used.

[0034]

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 mixture was reacted for 4 hours with stirring to obtain a mixture of a monomer and 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.), cresol novolac type epoxy resin (trade name: ESCN-220F, Sumitomo Chemical Co., Ltd.)
(Manufactured by Mitsui Chemicals Co., Ltd.) was added and uniformly dissolved and mixed. Furthermore, 0.4 parts of zinc octylate was added as a catalyst, dissolved and mixed, and this was mixed with inorganic filler (trade name: calcined talc, manufactured by Nippon Talc Co., Ltd.)
Parts were added and mixed with uniform stirring to obtain a varnish A. A glass woven cloth having a thickness of 100 μm was impregnated with this varnish and dried at 150 ° C., gelling time (at 170 ° C.) 120 seconds, and the content of the thermosetting resin composition was 47 wt% prepreg (prepreg B) and A prepreg (prepreg C) containing 58% by weight of the thermosetting resin composition was prepared. Electrolytic copper foil with a thickness of 25 μm is placed above and below the above six prepreg B sheets, and the temperature is 200 ° C, 20 kgf / cm ² , 30 mmHg.
Laminated and molded for 2 hours under the following vacuum, insulation layer thickness 0.6mm
A double-sided copper-clad laminate D was obtained. 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 the target marks at the four corners to form a pattern by a standard method, and at the same time, the copper foil at the position where the through holes were to be opened was etched with a diameter of 70 μm. After this inner layer copper foil is treated with black copper oxide, one prepreg C is placed on each side, and an electrolytic copper foil with a thickness of 12 μm is placed on the outside of the copper foil, and laminated in the same manner. A stretched laminate was prepared. The copper foil on the target mark was removed by etching with a diameter of 3 mm to obtain a 4-layer double-sided copper-clad laminate E.

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 stirred and mixed (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 F is arranged on the front and back of the 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 set to 10
A roll at 0 ° C. was laminated at a linear pressure of 5 kgf / cm and adhered. The target marks at the four corners of the inner layer board were read with a CCD camera, and the hole diameter of 12
900 holes of 0 μm were directly irradiated with a carbon dioxide laser with a pulse energy of 30 mJ for 4 shots, and 70 blocks were punched through the outer copper foil, the insulating layer and the inner copper foil. Next, turn this over, and similarly read the target marks at the four corners of the inner layer plate with a CCD camera, irradiate the same position on the back side, which is the opposite side, with a 120 μm hole at the same energy for four shots, and then use the outer copper foil and insulating layer. And the inner layer copper foil was processed to form holes penetrating the front and back. The maximum deviation of the hole positions between the front and back was 5 μm. By the SUEP method, the chemical solution is sucked and passed through the inside of the hole,
At the same time as the copper foil burr generated around the inner and outer layer holes was dissolved and removed, the copper foil on the surface was also dissolved to 4 μm. The plate was plated with copper by 15 μm (total thickness: 19 μm) by a usual method. Patterns (line / space = 50/5
(200 μm of 0 μm), solder ball lands, etc. are formed, and at least semiconductor chips, bonding terminals, and solder ball lands are covered with plating resist, and nickel and gold plating is applied to create a multilayer printed wiring board. did. 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. Use 8 pieces of this prepreg H,
Place 18μm thick electrolytic copper foil on both sides, 190 ℃, 20kgf / cm ² ,
A double-sided copper-clad laminate J having an insulating layer thickness of 0.8 mm was produced by laminating and forming under a vacuum of 30 mmHg or less for 2 hours. A pattern is formed on the surface of this copper foil, and the copper foil at the position where the through hole is to be formed
Etching off at 80 μm, and making target marks at four corners of each printed wiring board by drilling in the same manner as in Example 1,
After chemical treatment (mech treatment: CZ8110 + CL8300E treatment, copper foil surface unevenness 3 μm) is applied to the copper foil surface, one prepreg I is placed on each side, and the copper foil shiny surface is nickel / cobalt on both sides. An alloy-treated electrolytic copper foil having a thickness of 12 μm was placed, and similarly laminated and formed to prepare a four-layer double-sided copper-clad laminate K.

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 mmφ so that the target mark could be read from the surface. After reading the target mark formed on the inner layer with a CCD camera from this surface, irradiating 4 shots with carbon dioxide gas laser energy of 12 mJ from the surface to process the outer layer copper foil, insulating layer and inner layer copper foil, and then further this multilayer double-sided copper clad Turn the laminate upside down, read the target mark formed on the inner layer with a CCD camera in the same way, and irradiate 4 shots at the same position on the backside copper foil with 12 mJ of energy to expose the outer copper foil, insulating layer and inner copper foil. Processed through both front and back hole diameter
A 120 μm through hole was formed. The maximum positional deviation was 7 μm. Using this, a multilayer printed wiring board was similarly prepared. 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 back sheet on the lower surface, the copper clad board was slightly floated to form an air layer on the lower surface, and carbon dioxide laser energy was 35 mJ for 12 shots. 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 at an 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 surface copper foil was etched by a conventional method at the same location as the location where a hole having a pore diameter of 120 μm was formed in this inner layer copper foil, and 15 mJ of carbon dioxide gas energy was irradiated for 7 shots to form a through hole. Desmear treatment was performed, SUEP treatment was not performed, copper plating was performed at 15 μm, circuits were formed on the front and back surfaces, and a multilayer printed wiring board was similarly prepared. The evaluation results are shown in Table 1.

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 the desmear treatment, copper plating was adhered to a thickness of 15 μm and the multilayer printed wiring board was similarly prepared without the SUEP treatment. The evaluation results are shown in Table 1.

(Table 1) Item Example Comparative Example 1 2 1 2 3 Deviation of front and back hole positions (μm) 5 7 <5 21 38 Gap between hole wall and inner copper foil (μm) 0 0 0 16 0 Hole shape Almost circular Almost circular Irregularly irregular Irregularly circular pattern breaks and shorts (pieces) 0/200 0/200 0/200 51/200 47/200 Missing copper foil around holes No No No Yes No No Glass transition temperature (℃) 235 160 235 160 235 Through-hole heat cycle test (%) 2.4 3.9 17.9 27.1 2.8 Migration resistance Normal 1x10 ¹⁴ 2x10 ¹⁴ー ー 300hrs. 4x10 ¹¹ 4x10 ⁹ー ー 500hrs. 5x10 ¹⁰ <10 ⁸ー ー

<Measurement method> 1) Deviation of front and back hole position and deviation of surface hole and inner layer hole position: 70 blocks were created with a hole size of 100 μm as 900 holes / block within a work size of 250 mm square (a total of 63,000 holes). ) Was prepared, and the maximum value of the 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 forming a comb-shaped pattern of line / space = 50/50 μm using a copper clad plate with holes made in Examples and Comparative Examples to which copper plating was adhered by 15 μm 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: In each example and comparative example, a 200-μm land was made in a through-hole with a hole diameter of 120 μm, and 900 holes were connected alternately on the front and back sides. 200 cycles were carried out from seconds to room temperature for 5 minutes, and the maximum rate of change in resistance was shown. 5) Copper foil break around land: After SUEP, it was observed whether copper foil remained around the hole or was missing. 6) Migration resistance: In each Example and Comparative Example,
A comb-shaped pattern was formed on the inner layer substrate with a line / space = 50/50 μm, and after the black copper oxide treatment, a prepreg used in each of the examples and comparative examples was laminated and molded to form a four-layer board. After making and removing the copper foil on the surface layer by etching, apply this at 85 ℃ ・ 85% RH ・ 50VDC, and after processing for a predetermined time, take it out and leave it in an atmosphere of 25 ℃ ・ 65% RH for 2 hours, then apply a voltage of 500VDC. Was applied to measure the insulation resistance value between the patterns.

[0043]

EFFECTS 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. After forming, and then multilayer molding to produce a multilayer double-sided copper clad board, laser is directly irradiated on the outer layer copper foil at the position where the inner layer is perforated to form the outer layer copper foil, the insulating layer and the inner layer copper foil. After forming a hole through the place where the copper foil was previously etched to form the hole, the outer layer copper foil, the insulating layer and the copper foil were previously etched by irradiating the laser again from the same position on the opposite surface. By forming holes that penetrate the front and back of the inner layer copper foil that has been formed with holes, it is not necessary to etch and remove the outer layer copper foil in advance, and the position of the holes on the front and back of the copper clad plate can be misaligned. Almost no through holes having a good shape could be formed. Furthermore, both surfaces of the copper foil can be planarly etched by post-treatment, and the thickness of part of the original copper foil can be removed by etching, and at the same time, the burrs of the copper foil generated in the holes can be removed by etching.
Even in the circuit formation of the front and back copper foil obtained by plating up with subsequent copper plating, defects such as shorts and pattern breaks do not occur, and it is possible to create a high-density printed wiring board that is well connected to the inner copper foil. , I was able to obtain a highly reliable one.

[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 Location seen from cross section e Formed by etching with a diameter smaller than the through hole to be drilled in advance Through-hole forming part of inner layer f Pattern formation area g Inner insulating layer part h Layer formed by prepreg i Outer layer copper foil treated with cobalt alloy j Inner layer copper foil obtained by etching away the copper foil at the part where the through hole is to be formed in advance k CCD Camera l Part of the target mark where the outer layer copper foil is removed by etching m Target mark of the inner layer of the 4-layer copper clad laminate n Outer layer copper foil burr generated by carbon dioxide gas laser drilling o Inner layer copper generated by carbon dioxide gas laser drilling Foil burr p A hole halfway through the inner layer copper foil q A reverse etching, through which a carbon dioxide laser was applied from the opposite side, and a through hole r SUEP for thin etching Outer layer copper foil s Inner layer copper foil burr part removed by etching with SUEP t Outer layer copper foil burr part removed by etching with SUEP u Copper plated surface layer copper foil part and through hole part v Pattern formed on outer layer w Outer layer removed by etching in advance Copper foil part x General electrolytic copper foil y Part of the inner layer copper foil of the part where the through hole is to be formed is removed by etching the hole of the same size as the size of the outer layer copper foil previously formed z When the through hole is opened by carbon dioxide laser Gap between the hole wall and the outer layer copper foil α Gap between the hole wall and the inner layer copper foil generated 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 AA01 AF01 CA08 DA11 DB14                 5E346 AA29 AA42 CC04 CC05 CC09                       CC10 CC12 CC13 CC32 CC37                       DD02 DD12 DD32 EE01 EE06                       EE09 EE13 FF07 GG15 GG17                       GG22 GG28 HH07 HH22 HH25                       HH26 HH33

Claims (2)

[Claims] 1. A method of forming a through hole of 30 to 180 μm on both sides of a multi-layer double-sided copper clad plate by first etching a copper foil with a diameter smaller than the through hole diameter in advance at the place where the through hole of the inner layer substrate is to be formed. After forming it, and then forming a multilayer double-sided copper clad board by multi-layer molding, one side of the outer layer copper foil is directly irradiated with a laser to etch the outer layer copper foil, the insulating layer and the inner layer copper foil in advance. After forming a hole through the place where the hole was formed, laser is irradiated again from the same position on the opposite surface to etch the outer copper foil, the insulating layer and the copper foil in advance to form the hole. A method of forming a through hole in a multilayer double-sided copper clad plate by a laser, which comprises forming a through hole through the inner layer copper foil. 2. The method for forming a through hole in a multilayer double-sided copper clad board by a laser according to claim 1, wherein the hole diameter preformed by etching the inner layer copper foil is 50 to 80% of the through hole diameter.