JP2005045046A - Process for producing multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a high density multilayer printed wiring board having a through hole exhibiting excellent workability, economy and reliability. <P>SOLUTION: A copper clad multilayer substrate is made by aligning a multilayer board including electronic circuit conductors at high density in an inner layer and the copper foil is irradiated directly with a UV laser beam from above to open a through hole where the difference of diameter is 20% or less between the surface and rear and the hole diameter is preferably in the range of 20-100 μm on the incoming side. Copper plating is carried out on the entire surface including the inside of the through hole by electroless plating and/or electroplating and then the central part of the hole is closed by a plating deposition layer projected from the opposite hole walls by electroplating. Subsequently, upper and lower spaces remaining in the through hole are filled by 90% or more with copper or a copper alloy deposited by performing electroplating using a reverse pulse power supply. At the same time, pattern plating is performed on the electronic circuit conductors and electronic circuits are formed on the opposite outer sides thus producing a multilayer printed wiring board. Thickness of the printed wiring board is preferably set in the range of 0.1-0.5 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a multilayer printed wiring board having through-holes with a small diameter, and particularly to a multilayer printed wiring board having high-density wiring and excellent hole reliability, the obtained multilayer printed wiring board is Can be widely used for semiconductor plastic packages, motherboards, etc.

Conventionally, a printed wiring board has a prepreg and a copper foil disposed on an inner layer board, and a through hole is drilled after integral molding (see, for example, Patent Document 1). This drill had a problem that the drill breaks when drilling with a small diameter of 150 μm or less, and the processing speed is slow. In addition, there is a printed wiring board that is made by gradually laminating and stacking with a build-up method and conducting conduction between the upper and lower copper foils through blind via holes (see, for example, Patent Documents 2 to 4). As a result, the process is long and the price is high. Further, when the through hole is large, when the inside of the through hole is filled with copper plating, many voids remain in the copper plating, and the plating solution remains, resulting in poor reliability.
JP 2000-91750 A JP 2000-91750 A JP 2000-183384 A Japanese Patent Laid-Open No. 4-338695

  The present invention solves the above-mentioned problems by integrally forming a multilayer copper-clad plate, and by conducting each layer of this multilayer copper-clad plate preferably through a small-diameter through hole having a pore diameter of 20 to 100 μm, An object of the present invention is to provide a high-density multilayer printed wiring board having a small-diameter through hole having a shorter processing step and superior reliability than the substrate manufacturing method at low cost.

  In the present invention, through holes are formed in a multilayer copper-clad board using a UV laser and filled with copper plating, and then a multilayer printed wiring board is manufactured. In this case, the hole diameter is preferably 20 to 100 μm. The hole has a tapered shape, but the hole is preferably drilled so that the difference in the hole diameter on the outlet side is 20% or less with respect to the hole diameter on the inlet side. Next, electroless copper plating and / or ultra-thin electrolytic copper plating is performed on the entire surface including the inside of the through hole to make the surface of the insulator electrically conductive, and then the central portion of the through hole is placed from both hole walls by direct current electroplating. Closed by the deposited copper plating deposit layer, then filled the space left and right in the through hole with electroplating by reverse pulse power supply with deposited copper or copper alloy, and simultaneously pattern plated the electronic conductor, and finally the electronic circuit on both sides To form a multilayer printed wiring board.

  Also in the case of drilling, the hole diameter is preferably 20-100 μm, the insulating layer is preferably a base-reinforced thermosetting composition, and the electrically insulating interlayer thickness is preferably 10 μm-0.48 mm, The hole filling degree is remarkably improved and the reliability is excellent, and a high-density multilayer printed wiring board can be obtained.

  By making the through hole diameter difference due to the UV laser 20% or less, when filling the through hole with copper plating, it is possible to eliminate the filling failure caused by defects in the plated copper filling speed and shape due to the difference in hole diameter.

  A process of manufacturing a multilayer printed wiring board having an electronic circuit conductor in the inner layer and metal in both outer layers bonded to the entire surface, and then penetrating both the outer layer and inner layer electronic circuit conductor by UV laser Then, the step of forming the micro-holes so that the difference in diameter between the front and back surfaces is 20% or less, and then the copper inside the through-holes by copper or copper alloy by electroless plating and electroplating. The center of the hole is closed by the plating deposit layer, and then the space remaining above and below the through hole is filled with deposited copper or copper alloy by electroplating with a reverse pulse power source, and at the same time, the electric conductor is pattern-plated, and then both sides are electronic circuits By manufacturing the multilayer printed wiring board, the high-density circuit board equivalent to the high-density multilayer board by the build-up method can be greatly reduced in the multilayer circuit formation process. Gender, it was possible to obtain an excellent multilayer printed wiring board in economy. Furthermore, by filling the hole with copper plating, a high-density multilayer printed wiring board excellent in hole conduction reliability could be manufactured.

  In the printed wiring board of the present invention, a multilayer copper-clad board having one or more copper layers inside is manufactured by a normal multilayer substrate manufacturing process, and a UV laser is directly irradiated on the copper foil from one side to open a through hole. The through hole is filled with 90% by volume or more with copper plating, and the surface layer is preferably mechanically polished and smoothed, and then an outer layer circuit is formed by a known method to obtain a multilayer printed wiring board.

  As the multilayer printed wiring board used in the present invention, generally known multilayer copper foil-clad boards are used. The resin used is not particularly limited, and generally known resins are used. Specifically, thermosetting resin compositions such as epoxy resins, polyimide resins, polyfunctional maleimide resins, polyfunctional cyanate ester resins, unsaturated group-containing polyphenylene ether resins, thermoplastic resins, photoselective heat Generally known resins such as curable resins and additive resins are used alone or in combination of two or more. In order to obtain a multilayer printed wiring board having excellent heat resistance and migration resistance, it is preferable to use a resin composition containing a polyfunctional cyanate ester resin as an essential component.

  The polyfunctional cyanate ester compound which is a suitable resin 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 the reaction of novolac and cyanogen halide.

  Besides these, multifunctional cyanic acid described in JP-B-41-1928, JP-A-43-18468, JP-A-44-4791, JP-A-45-11712, JP-A-46-41112, JP-A-51-63149, etc. Ester compounds can also be used. Those containing bromine and phosphorus in these molecules can also be used. Further, 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 resin also contains a partially unreacted monomer and is in the form of a mixture of a monomer and a 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.

  There is no limitation in particular as an epoxy resin, Generally a well-known thing can be used. For example, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, alicyclic epoxy resin, novolac-type epoxy resin, biphenyl-type epoxy resin and the like are used alone or in combination. It is preferably used after being dissolved in a soluble organic solvent.

  What is used as an organic solvent for dissolving the resin is not particularly limited, for example, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aromatic hydrocarbons such as toluene and xylene; N, N-dimethylformamide and the like These amides may be used, and these may be used alone or in combination of two or more.

  The curable resin composition of the present invention is cured by heating, but has a slow curing rate and is inferior in workability, economy, and the like, and therefore a known curing catalyst is used for the curable resin used. When (meth) acrylates are used, a photopolymerization initiator is used. The amount used is 0.005 to 10 parts by weight, preferably 0.01 to 5 parts by weight per 100 parts by weight of each curable resin.

  In the curable resin composition of the present invention, various additives other than the above can be blended as desired within a range where the original properties of the composition are not impaired. Examples of these additives include solid and liquid epoxy resins, double bond addition polyphenylene ether resins, polyphenylene ether resins, polyolefin resins, epoxy acrylates, polyfunctional (meth) acrylates, and other known bromides and phosphorus-containing materials. Various resins such as compounds, other known inorganic and organic fillers, dyes, pigments, thickeners, lubricants, antifoaming agents, dispersants, leveling agents, photosensitizers, flame retardants, brighteners, Various additives such as a polymerization inhibitor and a thixotropic agent are used in appropriate combination as desired. If necessary, the compound having a reactive group is appropriately mixed with a known curing agent and catalyst.

   As a method for uniformly dispersing the components of the present invention, generally known methods can be used. For example, generally known methods such as mixing each component with an organic solvent and stirring at high speed with a homomixer, kneading with a three-roller at room temperature or under heating, or kneading with a ball mill or a likai machine are used. Is done.

  The printed wiring board used in the present invention may be either without a base material or with a base material, but in order to increase the rigidity, a substrate having a base material reinforcement is preferable. A base material is impregnated with the above resin composition and dried to form a B stage, or a resin layer is disposed on both surfaces of the base material and integrated by thermocompression bonding or the like to prepare a prepreg. As the substrate, organic or inorganic fiber woven fabric or non-woven fabric is used. Although there is no particular limitation on the type, a heat-resistant woven or non-woven fabric such as liquid crystal polyester fiber, polybenzazole fiber, wholly aromatic polyamide fiber or the like is preferably used as the organic fiber cloth. As the inorganic fiber cloth, a known glass fiber woven cloth or non-woven cloth having a general circular cross section and a flat shape, and further a ceramic fiber woven cloth or non-woven cloth are used. These are preferably opened glass woven fabrics. Moreover, heat resistant organic film base materials, such as a polyimide film, a wholly aromatic polyamide film, and a liquid crystal polyester film, can also be used conveniently. In order to improve the adhesion of the thermosetting resin composition, the surface of the film substrate is subjected to corona treatment, plasma treatment, chemical treatment, and the like.

  In addition, for example, there are no particular limitations on the layers that are arranged on the inner substrate on which the double-sided circuit is formed, and there are no particular limitations. Additive resin composition, copper foil with B-stage resin, organic or inorganic base material reinforced B-stage resin composition (Prepreg), heat-resistant film equipment B-stage resin composition (prepreg), etc., generally known laminated sheets, build-up type photoselective thermosetting resists, etc. can be used. Blind via holes can be formed if necessary, but from the viewpoint of productivity, efficiency, cost, etc., all are laminated to form a multilayer copper-clad plate, and finally a direct copper foil using a UV laser After that, the entire circuit including the inside of the through hole is plated with copper, and then a circuit is formed to form a printed wiring board, or a pattern plating resist is attached to the surface and then developed, exposed, and exposed. The whole including the inside is plated with copper, and after removing the plating resist, a high-density printed wiring board is formed by a method of forming a fine circuit by flash etching or the like.

  A method for producing a multilayer board having at least one copper layer as an inner layer of the present invention is not particularly limited. For example, a prepreg is produced by impregnating a substrate with the resin composition and drying, and a metal foil on both sides. A double-sided copper-clad board containing a substrate is preferably produced using copper foil. After using this to form circuits on both sides and chemically treating the surface, use a plurality of this inner layer plate, arrange the prepreg between the inner layer plates, arrange the prepreg and copper foil on both outer sides, laminate molding, A multilayer copper-clad plate is used. The thickness of the copper foil to be used is not particularly limited, but is appropriately selected in consideration of processability, subsequent formation of a fine circuit, and the like. Preferably, the inner layer copper foil is 5 to 18 μm, and the outer layer copper foil is 3 to 12 μm. Of course, it is also possible to use a 3 to 12 μm copper foil-clad multilayer board and a copper foil thickness of 1 to 2 μm by dissolving the surface layer copper foil with a chemical solution. The manufacturing method of the multilayer copper-clad board of this invention is not limited to this, Generally a well-known method can be used.

Lamination molding conditions for multi-layering of the present invention are not particularly limited, but are charged into a known apparatus such as a vacuum laminator press, a general multi-stage press, etc., generally at a temperature of 100 to 300 ° C., a pressure of ^{2 to} 50 kgf / cm ^2. The time is from 1 minute to 5 hours, and preferably laminated and formed under vacuum. Those having a short lamination time are post-cured in a heating furnace or the like.

  In addition to this, in the case of using a known multilayer copper-clad plate, for example, a build-up type light selective thermosetting resist or additive resin composition, it is coated on a substrate and dried to form a B-stage to roughen the surface. In addition, it is possible to use a multi-layered copper plating method for forming a circuit. In any case, the thickness between the insulating layers is preferably 10 μm to 0.48 mm.

  When forming a through-hole with the UV laser of the present invention, a backup sheet is used on the back surface. In general, a known backup sheet can be used. For example, the backup sheets described in JP-A-11-346044, JP-A-11-347767, JP-A-2003-008172, JP-A-2003-008173, etc. can be used. Furthermore, a room temperature laminate type backup sheet in which a pressure-sensitive adhesive is blended in the resin composition layer that can be bonded at room temperature can also be used.

  A UV laser is used for through-hole drilling according to the present invention. The hole diameter on the entry side is preferably 20-100 μm. The type of UV laser is not particularly limited, and generally known ones such as UV-YAG laser and UV-Vana laser can be used, and a wavelength of 200 to 400 nm is preferably used. The hole shape is such that the outlet side hole diameter is 80% or more compared to the inlet side hole diameter. Of course, a combination of a carbon dioxide laser and a UV laser can also be used, but a UV laser is preferred when forming small-diameter holes. In order to control the hole diameter difference between the through holes, the optimum machining conditions are selected as machining conditions of the UV laser by machining design using a combination of a galvanometer position control program for controlling the number of laser beam shots, laser beam output control and position.

  In producing the ultrafine wire circuit of the present invention, in a semi-additive process, copper plating is performed after forming a pattern plating resist, and after the resist is removed, a fine circuit is formed by etching. Although this solution is not particularly limited, for example, JP-A Nos. 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 a method of dissolving and removing a metal surface with a chemical (referred to as SUEP method). The etching rate is 0.02 to 1.0 μm / sec.

  The process of manufacturing the multilayer printed wiring board of the present invention includes the steps of manufacturing a multilayered multilayer printed wiring board having an electronic circuit conductor on the inner layer and a metal foil bonded to the entire surface on both outer layers. Next, a step of forming a through hole through both the outer layer and inner layer electronic circuit conductors with a UV laser, and then filling the inside of the through hole with copper or a copper alloy by electroless plating and then electroplating with a DC reverse pulse power source. The inner and outer layer electronic conductors are pattern plated, and then electronic circuits are formed on both outer sides. This through hole shape has a difference of 20% or less of the diameter of the exit side with respect to the diameter of the entrance side, and when drilling, the diameter of the hole is preferably 20-100 μm, and the thickness between the insulating layers is preferably By using a thermosetting composition for substrate reinforcement and having an electrically insulating interlayer thickness of preferably 10 μm to 0.48 mm, a highly reliable multilayer printed wiring board can be obtained.

In the method of filling the through holes of the present invention, electroless copper plating and / or ultra-thin electrolytic copper plating is performed on the entire surface including the through holes, and the surface of the insulator is made electrically conductive. The center of the hole is closed approximately at the center by a copper plating deposit layer protruding from both hole walls, and then the remaining space above and below the through hole is filled with deposited copper by electroplating with a reverse pulse power source. The through hole is plated with copper or copper alloy, and is generally plated and filled with a current density of 1 to 3 A / dm ² . This filling rate is 90% by volume or more. Of course, the upper and lower portions of the hole may be partially uneven, but in order to make it smooth, the surface is mechanically polished with a buffing device or the like to make it smooth.

  In the case of pattern plating, electrolytic copper plating is deposited so as to exceed the thickness of the pattern plating resist, and the surface is polished smoothly by mechanical polishing to a predetermined thickness. By doing so, uneven thickness due to variations in pattern copper plating thickness is eliminated, and at the same time, the surface layer becomes smooth, and a multilayer printed wiring board suitable for flip chip mounting and the like can be obtained.

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)
2,2-bis (4-cyanatophenyl) propane monomer was melted in 400 parts at 150 ° C. and reacted for 4 hours with stirring to obtain a monomer and prepolymer mixture having an average molecular weight of 1,900. This was dissolved in methyl ethyl ketone to obtain varnish A. In addition to this, 350 parts of bisphenol A type epoxy resin (trade name: Epicoat 1001, manufactured by Japan Epoxy Resin Co., Ltd.), 50 parts of novolac type epoxy resin (trade name: DEN431, manufactured by Dow Chemical Co., Ltd.), cresol novolac type epoxy resin (Product name: ESCN-220F, manufactured by Sumitomo Chemical Co., Ltd.) 100 parts were blended, 0.3 part of acetylacetone iron was dissolved in methyl ethyl ketone as a curing catalyst, and the mixture was uniformly stirred to obtain varnish B. Furthermore, 1200 parts of spherical silica (average particle size 4.1 μm) was added, and dispersed and mixed uniformly to obtain varnish C. This varnish C is impregnated into a glass woven fabric having a thickness of 50 μm, dried, and prepreg D (gelation time at 170 ° C. for 130 seconds, resin composition content: 54 wt%) and a opened glass woven fabric having a thickness of 15 μm. Was impregnated and dried to prepare prepreg E (gelation time at 170 ° C .: 143 seconds, resin composition content: 81 wt%). Using a single prepreg D, an electrolytic copper foil having a thickness of 12 μm was placed on both sides, and laminate-molded at 200 ° C. and 25 kgf / cm ² for 90 minutes to prepare a double-sided copper-clad laminate F. Using this, circuits are formed on the front and back, and this surface is treated with black copper oxide. Then, one prepreg E is placed between the two inner layers, and one prepreg E is placed on both outer sides. Then, an electrolytic copper foil having a thickness of 12 μm was placed thereon and laminated and molded in the same manner to obtain a 6-layer double-sided copper-clad board G. This copper foil was etched and thinned with a SUEP solution to a copper foil thickness of 4 μm to obtain a 6-layer double-sided copper-clad plate H.

  On the other hand, a backup sheet I was prepared by applying and drying a solution of water-soluble polyester resin having adhesiveness at room temperature on one side of an aluminum foil having a thickness of 50 μm in water so as to have a resin layer thickness of 50 μm. The backup sheet I was placed under the six-layer double-sided copper-clad laminate H so that the resin surface faced the copper foil side, and was laminated and adhered at room temperature with a linear pressure of 5 kgf / cm. From the top of this 6-layer double-sided copper-clad laminate H, through-holes having an upper hole diameter of 60 μm and a lower hole diameter of 55 μm were formed by directly irradiating a copper foil with a UV-YAG laser at an interval of 1 mm.

  Electroless copper plating 0.5 μm and electrolytic copper plating 1 μm are attached to the entire plate to make the insulator surface electrically conductive. Then, a pattern plating resist is attached 25 μm thick on this surface, and direct current electroplating is applied to the inside of the through hole. The center of each hole was protruded from both hole walls, and the center of the hole was closed with a copper plating deposited layer, and then the space remaining above and below the through hole was filled with the deposited copper to achieve a filling rate of 100%. At the same time, the height of the copper plating for the circuit was adhered to 25 to 28 μm, and this surface was polished to a copper plating height of 22 μm by mechanical polishing to smooth the surface. Thereafter, the pattern plating resist was peeled and removed, and then flash etching was performed with a SUEP solution to form a circuit of line / space = 30/30 μm. A 6-layer printed wiring board was produced by attaching nickel plating and further gold plating to the surface. The evaluation results are shown in Table 1.

(Example 2)
Bisphenol A type epoxy resin (trade name: Epicote 1001), 500 parts, phenol novolac type epoxy resin (trade name: DEN438, manufactured by Dow Chemical Co., Ltd.), 500 parts, imidazole curing agent (trade name: 2E4MZ, Shikoku) Kasei Chemical Co., Ltd.) 30 parts, carboxyl group-modified acrylic multilayer structure powder (trade name: Staphyloid IM-301, average particle size 0.2 μm, Max. Particle size 0.5 μm), finely pulverized silica (average particle size) 2.4 μm, Max. Particle size 5.0 μm) 40 parts, Talc (average particle size 1.8 μm, Max. Particle size 4.2 μm) 100 parts, and acrylonitrile-butadiene rubber (trade name: Nipol 1031, manufactured by Nippon Zeon Co., Ltd.) A solution in which 30 parts were dissolved in methyl ethyl ketone was added and dispersed well with three rolls to obtain Varnish J. This varnish J was applied to one side of a release PET film having a smooth surface and a thickness of 25 μm, dried, and dried to obtain a B-stage resin composition sheet K with a release film having a thickness of 7 μm (at 170 ° C. The gelation time is 67 seconds), and when it comes out of the drying zone, a protective polypropylene film with a thickness of 20 μm is placed on the resin surface and laminated continuously with a roll at a temperature of 100 ° C and a linear pressure of 5 kgf / cm. Wound up.

  Also, bisphenol A type epoxy resin (trade name: Epicote 1001), 500 parts, phenol novolac type epoxy resin (trade name: DEN438), 450 parts, imidazole curing agent (trade name: 2E4MZ), 30 parts, MBS Varnish L was obtained by adding 150 parts of resin powder (trade name: average particle size 0.2 μm, Max. Particle size 0.5 μm) and uniformly dispersing with three rolls. This varnish L is continuously applied to a 25 μm thick smooth PET release film and dried to form a B-stage resin composition layer M having a resin composition thickness of 10 μm and a gel time of 65 seconds. Is placed on one side of heat-resistant film N with a surface of 4.5μm thick aromatic polyamide (aramid) film treated at 900W for 2 minutes and a water contact angle of 5 degrees, and B on the opposite side. B stage resin composition sheet with double-sided release film containing heat-resistant film base material, placed while peeling off protective film of stage resin composition sheet K, laminated with a heating roll at a temperature of 100 ° C. and a linear pressure of 5 kgf / cm Was made. Further, a B-stage resin composition sheet P with a double-sided release film in which a B-stage resin composition layer M was adhered to both surfaces of the heat-resistant film N was produced.

On the other hand, a circuit is formed on an epoxy-based copper-clad laminate (trade name: CCL-EL170, manufactured by Mitsubishi Gas Chemical Co., Ltd.) with a thickness of 0.1 mm and 12 μm double-sided copper, and this inner layer is treated with black copper oxide on the conductor. The release film on both sides of the B-stage resin composition sheet P with a release film containing a heat-resistant film substrate is placed between two plates, and the B-stage with the release film is placed on both outer sides of the inner layer plate. The release film on the resin composition layer 10 μm side of the resin composition sheet O is peeled off and placed, loaded into a press machine, the temperature is raised to 170 ° C. in 25 minutes, the pressure is set to 15 kgf / cm ² from the beginning, vacuum After holding for 30 minutes at a temperature of 170 ° C at a temperature of 0.5 Torr, cooling and taking out, removing the release film on this surface, roughening with chromic acid aqueous solution, from the resin surface layer The total unevenness was 2.9 to 5.0 μm (average roughness Rz: 3.5 μm). Next, 1 μm of electroless copper plating is attached to this roughened surface, put in a heating furnace, gradually increase the temperature from 100 ° C to 150 ° C in 30 minutes, further increase the temperature gradually and heat at 170 ° C for 60 minutes Cured. The back-up sheet I of Example 1 was laminated and bonded to the lower side of this plate at room temperature, and a UV-YAG laser having a wavelength of 355 nm was directly irradiated on the plate to form a through-hole having an inlet-side hole diameter of 40 μm and an outlet-side hole diameter of 35 μm. After opening, a pattern plating resist is formed 25 μm in height on this, and after exposure and development, electroless copper plating 0.4 μm and electrolytic copper plating 25 to 28 μm are applied in the same manner as in Example 1 to fill the through hole 100%. Then, after dissolving and removing the resist, a circuit of line / space = 20/20 μm is prepared by flash etching with SUEP solution, and the circuit conductor is nickel-plated and gold-plated to form a 6-layer printed wiring board as in Example 1. did. The evaluation results are shown in Table 1.

Example 3
Varnish Q containing 50% by weight of calcined talc in varnish B of Example 1 was impregnated into a 30 μm-thick wholly aromatic polyamide fiber nonwoven fabric and dried to obtain a resin composition content of 75 wt% and a gel time of 120 Second (at 170 ° C.) prepreg R was prepared. Using this, 8 sheets of prepreg D of Example 1 were used, 12μm thick electrolytic copper foil was placed on both sides, and laminate molding was performed at 200 ° C and 25kgf / cm ² for 90 minutes to produce a double-sided copper-clad laminate did. Using this, circuits are formed on the front and back, and this surface is treated with black copper oxide, then one prepreg R is placed on both sides of this inner layer board, and 5 μm electrolytic copper with a 35 μm thick copper foil carrier on the outside. A four-layer copper-clad laminate S was prepared by arranging foils and laminate-molding under the same lamination conditions. After peeling off the carrier foil on the surface, the copper foil thickness was dissolved to 2 μm with the SUEP solution, and the backup sheet I of Example 1 was laminated and bonded to the lower side of this plate, and UV-Vana with a wavelength of 355 nm was applied from above the plate. Irradiate a laser to form a through hole with an incoming hole diameter of 70 μm and an outgoing hole diameter of 60 μm, and attach electroless copper plating 0.7 μm and electrolytic copper plating 1.5 μm to it, and carry pattern plating resist on it It was made to adhere in the same manner as in Example 1 and processed in the same manner to fill the inside of the through hole with 98% copper plating. After polishing the surface layer to a copper plating thickness of 22μm by mechanical polishing and smoothing the surface, the pattern plating resist was peeled off, and a circuit of line / space = 25 / 25μm was prepared by flash etching, as in Example 1. The circuit conductor was nickel-plated and gold-plated to form a 4-layer printed wiring board. The evaluation results are shown in Table 1.

(Comparative Example 1)
Using the double-sided copper-clad laminate F of Example 1, a 150 μm through hole was drilled with a general NC drill, and electroless copper plating 0.5 μm and electrolytic copper plating 15 μm were attached. After forming a double-sided circuit on this and performing black copper oxide treatment, one prepreg E was placed on each side, and 12 μm electrolytic copper foil was placed on the outside to form a four-layer board in the same manner. . A blind via hole having a hole diameter of 100 μm was formed in this with a carbon dioxide laser, and the inner layer plate and the through hole were connected to each other to form a conductive structure. Desmear treatment, electroless copper plating 0.7μm, electrolytic copper plating 15μm attached, black copper oxide treatment is applied after circuit formation, prepreg E is placed on this front and back, laminated molding, pattern processing is done in the same way, 6 layers, Printed wiring. The evaluation results are shown in Table 1.

(Comparative Example 2)
In Example 2, a 0.5 mm thick, 12 μm double-sided copper-clad laminate was used for the inner layer plate, and the others were similarly processed into a 6-layer copper-clad laminate, which was used as a printed wiring board. The evaluation results are shown in Table 1.

(Table 1)
Item Example Comparative example
1 2 3 1 2
Multilayer printed wiring board thickness (mm)
0.28 0.33 0.52 0.31 1.15
Number of printed wiring board layers
6 6 4 6 6
Multilayer insulation interlayer thickness (μm)
24 15 35 24 15
Through hole diameter (μm)
60 40 70 100 150
Through-hole ratio
0.97 0.88 0.86 --- 1.0
Filling rate of copper plating in through hole (%)
100 100 98 --- 84
Conduction hole / heat cycle test (%)
1.3 2.6 1.0 11.5 10.1

(Table 2) Number of machining comparison items Example Comparative example
1 2 3 1 2
Laminating press 1 1 1 2 1
Drilling 1 1 1 5 1
Copper plating 1 1 1 3 1
Conductor circuit creation 3 3 2 3 3
Drilling time comparison 1 1 1 3.3 1.2

<Measurement method>
1) Multilayer printed wiring board thickness: The total thickness including copper foil was measured with a thickness meter.
2) Thickness of laminated insulating layer: A cross-sectional photograph was taken and the thickness between insulating layers was measured. The thickness between the surface insulating layers is shown.
3) Through hole front / back ratio: 100 inlet-side hole diameters and outlet-side hole diameters were measured, and the average value was used to indicate the ratio of the back diameter / front diameter.
4) Copper plating in through-holes: Percentage of copper plating filling in the holes opened in each example and comparative example was observed at 100 cross-sections, and the rate of filling 90% or more copper plating in the holes showed that. In addition, the thing with a space | gap inside was not filled.
5) Front / back through-hole / heat cycle test: Land diameter of 200μm is made in each hole, 900 holes are connected alternately on the front and back, and one cycle is 200 cycles at 260 ° C, solder, immersion 30 seconds → room temperature, 5 minutes The maximum change rate of the resistance value was shown.
6) Machining process: The number of processes until the printed wiring board is completed, including the production of the inner layer board, is shown. Further, the comparison of the drilling time was shown as a comparative value with the example as 1.0 including the inner layer plate processing.

Claims (9)

A process of manufacturing a multilayer printed wiring board having an electronic circuit conductor in the inner layer and metal in both outer layers bonded to the entire surface, and then penetrating both the outer layer and inner layer electronic circuit conductor by UV laser In addition, the step of forming the through hole so that the difference between the diameter of the entrance side hole and the exit side hole of the through hole is 20% or less, and electroless plating and / or ultrathin electroplating is performed on the entire surface including the inside of the through hole to insulate After the body surface is made electrically conductive, the center portion in the through hole is closed by a plating deposit layer protruding from both hole walls by direct current electroplating, and then electroplated by a reverse pulse power source to remain above and below the through hole. A multilayer printed wiring board characterized in that the inner and outer layer electronic conductors are pattern plated at the same time, and then an electronic circuit is formed on both outer layers. After electroless copper plating and / or ultra-thin electrolytic copper plating is applied to the entire surface including the through holes to make the insulator surface electrically conductive, the center of the through hole is protruded from both hole walls by direct current electroplating. The central portion of the hole is closed with a copper plating deposition layer, and then the space remaining above and below the through hole is filled with deposited copper by 90% or more of the hole volume by electrolytic copper plating with a reverse pulse power supply. Item 11. A multilayer printed wiring board according to Item 1. 3. The multilayer printed wiring board according to claim 1, wherein the electrolytic copper plating is deposited so as to exceed the thickness of the pattern plating resist, and the surface is polished smoothly by mechanical polishing. The multilayer printed wiring board according to claim 1, 2 or 3, wherein the thickness of the multilayer printed wiring board is 0.1 to 1.0 mm. The multilayer printed wiring board according to claim 1, 2, 3, or 4, wherein the through-hole diameter of the through hole is 20 to 100 µm. The multilayer printed wiring board according to claim 1, 2, 3, 4, or 5, wherein the thickness of the electrical insulating layer between the electronic circuit conductors of each layer is 10 µm or more and 0.48 mm or less. The multilayer printed wiring board according to claim 1, 2, 3, 4, 5, or 6, wherein the electronic circuit conductor is mainly copper foil and / or electroplated copper. The multilayer printed wiring board according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the electrical insulating layer is a thermosetting resin composition reinforced with a reinforcing substrate. The reinforcing substrate according to claim 8 is composed of one or more selected from glass fiber cloth, heat-resistant organic fiber cloth, and heat-resistant plastic film. The multilayer printed wiring board according to 6, 7, or 8.