JPH1041628A - Manufacturing method of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form high precision fine holes used as buried via-holes, by forming a cured resin composition layer on a copper foil circuit of an inner layer board having the copper foil circuit on the surface thereof. SOLUTION: A resin composition material 6 is applied on a glass-epoxy laminated board (inner board) 2, having a copper foil circuit 1 and having copper foils on both surfaces electrically connected by silver paste 3, and is dried so that the thickness thereof on the copper circuit becomes e.g. 50μm. Then, a resin composition material 6 is also formed on the opposite surface. Continuously, it is exposed to ultra-violet irradiation except buried via-hole forming parts through a pattern film, and by developing the non-exposed part with 1% sodium carbonate solution, high precision 0.1mmϕ buried via-hole forming fine holes 9 can be formed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board suitable for high-density mounting. In particular, it is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board having buried via holes for interlayer connection using a conductive paste.

[0002]

2. Description of the Related Art As electronic devices have become smaller and more multifunctional,
Currently, printed wiring boards are moving toward higher densities. For example, thinner conductor circuits, higher multilayers, smaller via holes including interstitial via holes such as through via holes, blind via holes, and buried via holes, and high-density mounting by surface mounting of small chip components. Therefore, various methods for manufacturing a multilayer printed wiring board excellent in large format and excellent in mass productivity are being developed. In addition, a multi-chip module (MC
M) is also formed by providing the above-mentioned via hole, but a change from the conventional device-based or ceramic-based MCM to a low-cost resin-substrate-based MCM is desired.

Conventionally, a copper-clad laminate having copper foil laminated on both sides via one or a plurality of glass epoxy prepregs or glass polyimide prepregs has been subjected to an etching treatment to form a wiring pattern of an inner layer panel and blackened. After processing, prepreg and copper foil are appropriately laid up and laminated by heating and pressing with a press, followed by drilling, plating, etching, etc. Are manufactured.

In the conventional method for manufacturing a multilayer printed wiring board, since a hot press is generally used as described above,
Inner layer panel, 0.05-0.2 as preparation for hot pressing
1 to 2 mm prepreg and copper foil, release film,
It is necessary to lay up a mirror press plate or the like, thermocompress it with a hot press or a vacuum hot press, and then take out and disassemble. This involves batch production such as lay-up, temperature rise during heating, heat-press bonding, cooling, dismantling, and has the problem of requiring a large number of steps.

In the case of drilling, since the number of steps is increased for drilling one hole at a time, the efficiency of drilling is generally increased by stacking a plurality of copper-clad laminates. However, as the density has increased recently, and small holes such as through via holes and blind via holes are required, it is necessary to drill the copper-clad laminates repeatedly due to problems such as processing accuracy and drill strength. In order to drill holes one by one with high precision, advanced processing technology is required, and there has been a problem such as a decrease in productivity.

To solve the above problem, Japanese Patent Laid-Open No.
In JP-A-42977, JP-A-7-86749, and JP-A-7-231163, a conductive paste is formed on a copper foil of an inner layer plate, and an insulating resin sheet such as a glass epoxy prepreg is coated with a conductive paste. A method of manufacturing a multilayer printed wiring board, characterized in that the layers are laminated by a hot press so as to penetrate, and a conductive paste is pressure-bonded to the outermost copper-roughened surface so that continuity between layers is obtained by bumps of the conductive paste. Has been proposed.

However, in this method, in order to penetrate the insulating resin sheet, the conductive paste is formed by, for example, screen printing so as to have a conical projection shape. It is necessary to increase the diameter of the paste. Therefore, the diameter of the conductive paste cannot be reduced for high-density wiring. Further, in order to penetrate the insulating resin sheet, it is necessary to make the tip of the conductive paste as sharp as possible, so that the shape of the tip when connecting by pressure bonding to the outer copper foil becomes large, and a stable bump shape cannot be obtained. There was a disadvantage.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board which eliminates the drawbacks of the above conventional method, is excellent in mass productivity, and has high density and high reliability.

[0009]

According to the present invention, a layer of a curable resin composition (hereinafter referred to as "resin composition A") is formed on a copper foil circuit of an inner plate having a copper foil circuit on the surface. Forming fine holes in a layer of the resin composition A, exposing the copper foil circuit through the fine holes; curing the resin composition A; conductive material for interlayer connection in the fine holes Filling and curing to form a layer thicker than the layer of the resin composition A; a thermoplastic curable resin having a thickness near the difference between the thickness of the conductive material and the layer of the resin composition A The resin composition side of a copper-clad insulating sheet obtained by forming a layer of a composition (hereinafter referred to as “resin composition B”) on the roughened side of a copper foil,
The inner layer plate is laminated by heat and pressure on the surface on which the conductive material is formed, and the copper foil on the inner layer plate and the copper foil on the copper-clad insulating sheet (hereinafter, referred to as "copper foil of outer layer") are formed by the conductive material. It is a method for manufacturing a multilayer printed wiring board, comprising: a step of electrically connecting the components; and a step of curing the resin composition B. Note that the order of the above steps may be changed as necessary.

According to the method of manufacturing a multilayer printed wiring board of the present invention, the diameter of a buried via hole made of a conductive material formed by using, for example, screen printing is determined by the diameter of a fine hole in a layer of the resin composition A. As a result, the bumps can be prevented from spreading at the time of print formation as in the prior art, so that a bump with a smaller diameter can be formed. And since a copper-clad insulating sheet having a layer of the resin composition B can be easily laminated by a hot roll or a hot press, a copper foil surface of an outer layer having high smoothness and high mass productivity is obtained, and high density is obtained. This facilitates the processing of forming a simple pattern. The bump portion of the conductive material is pressed against the roughened surface of the copper foil of the outer layer, so that the copper foil circuit on the inner layer board is electrically connected to the copper foil of the outer layer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition A having fine holes according to the present invention is a resin composition having thermosetting properties and / or active energy ray curability, and having heat resistance and insulating properties after curing. The fine holes for bumps made of a conductive material can be provided by, for example, laser processing or drilling after curing the resin composition A. On the other hand, when the resin composition A has curability by ultraviolet rays among the active energy rays and has alkali solubility, ultraviolet exposure and alkali development, that is, a layer of the composition is formed through a pattern film to form fine holes. By exposing and curing the part other than the part by ultraviolet irradiation and curing the unexposed part by alkali development, it is possible to provide a large number of fine holes in a lump and it is more preferable because mass productivity is improved. The curing of the layer of the resin composition A may be completely cured by the ultraviolet rays, or substantially cured by the ultraviolet rays, and then completely cured after forming the fine holes or after laminating a copper-clad insulating sheet described later. Is also good.

As the resin composition A, those having curability by an electron beam among the active energy rays are more preferable. This is because when the copper-clad insulating sheet is hot-pressed and laminated on the surface of the inner layer plate on which the conductive material is formed, when the resin composition is completely cured only by heating, the volatile component is contained in the resin composition. If it is contained, bubbles may be generated during thermosetting. However, when the resin composition is cured by irradiating an electron beam with a dose that transmits the copper foil, the state of the outer layer when the copper foil is laminated can be maintained, so that the smoothness is increased. Further, even if the resin composition contains some volatile components, no air bubbles are generated because the resin composition is fixed. Even if heat curing is used in combination after electron beam irradiation, the resin composition is solidified, so that the smoothness can be maintained and the generation of bubbles can be prevented.

The preferred resin composition A includes (1) acrylic acid and / or methacrylic acid (hereinafter referred to as “(meth)
Acrylic acid ". ) And a (meth) acrylic acid ester as main components (hereinafter referred to as “unmodified acrylic polymer”), and a carboxyl group derived from (meth) acrylic acid as a constituent component thereof A polymer having a compound having a glycidyl group and a C ＝ C unsaturated double bond added thereto (hereinafter referred to as “first component”); (2) a C ＝ C unsaturated double bond at the terminal (Hereinafter referred to as "second component"), (3) heating and / or irradiation of active energy rays
= A polymerization initiator capable of initiating the polymerization of unsaturated double bonds (hereinafter referred to as “third component”), (4) an active energy ray curing reaction accelerator (hereinafter referred to as “fourth component”), and When flame retardancy is required, a composition comprising (5) phosphorus or a phosphorus-based flame retardant (hereinafter, referred to as "fifth component") may be used.

Further, if necessary according to the type and purpose, the resin composition may contain a filler such as talc or charcoal, a coloring pigment, an antifoaming agent, a leveling agent, a thixo agent or a polymerization inhibitor. May be appropriately added.

On the other hand, the resin composition B having thermoplasticity formed on the roughened surface of the copper-clad insulating sheet of the present invention is, for example, 60 to 60% when laminated with an inner layer plate formed with a conductive material.
It has fluidity when heated at 120 ° C., has curability, and has heat resistance and insulating properties after curing.

The resin composition B can be used as long as it has thermosetting properties in addition to thermoplasticity. However, it is preferable that the resin composition B also has curability by electron beams. This is because, when the resin composition B is cured only by heating, the resin composition flows at the time of heating, and traces of the inner copper foil circuit and expansion and contraction of the resin cause the outer copper foil to have wrinkles and undulations. Sometimes. Further, when a volatile component is contained in the resin composition, air bubbles may be generated during thermosetting. However, when the electron beam is irradiated at a dose that transmits the copper foil, the resin composition is hardened, and the state of the copper foil of the outer layer when laminated is maintained, so that the smoothness is increased. Further, even if the resin composition contains some volatile components, bubbles are hardly generated because the resin composition is fixed. Even if combined with heat curing after electron beam irradiation, maintain the smoothness because the resin composition is solidified,
The generation of air bubbles can be prevented.

Although the resin composition B does not necessarily need to be alkali-soluble, it is more preferable that the resin composition B be alkali-soluble because after laminating the copper-clad insulating sheet, it is possible to carry out alkali washing for removing the resin that has flowed out.

Preferred resin compositions B include (1) the first component, (2) the second component, (3) the third component, and (4) the One obtained by blending five components is exemplified. The difference from the resin composition A is that the resin composition needs to have thermoplasticity and does not require ultraviolet curing. Moreover, as long as it has thermoplasticity, the composition may be the same as that of the resin composition A.

If necessary according to the type and purpose, a filler such as talc or charcoal, a coloring pigment, an antifoaming agent, a leveling agent, a thixotropic agent, and a polymerization inhibitor may be appropriately added to the resin composition. It may be added.

The unmodified acrylic polymer is, for example, methyl acrylate and / or methyl methacrylate (hereinafter referred to as “acrylate and / or methacrylate”).
Is referred to as “(meth) acrylate”. ), Butyl (meth) acrylate, hexyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate or tetrahydrofurfuryl (meth) acrylate, and (meth) acrylic acid ester, and (meth) acrylic acid. At a suitable composition ratio in a solvent, preferably an alcoholic solvent such as isopropyl alcohol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether or a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone, to give azobisisobutyrate. It can be obtained by copolymerization using lonitrile or benzoyl peroxide as an initiator.

Unmodified acrylic polymers include (meth)
As monomers other than acrylic acid and (meth) acrylic acid esters, vinyl monomers such as styrene and acrylonitrile other than these are used in a proportion of 25 mol% or less of all monomers constituting the unmodified acrylic polymer. Copolymerization is also possible, and it is preferable to use styrene among vinyl monomers because heat resistance is increased.

The preferred molecular weight of the unmodified acrylic polymer (weight average molecular weight in terms of polystyrene by gel permeation chromatography) is 10,000 to 10
0000, more preferably 20,000 to 70,0
00. If the molecular weight is too small, heat resistance and moisture resistance will be reduced, and if the molecular weight is too large, alkali solubility tends to be reduced.

The ratio of (meth) acrylic acid to (meth) acrylic acid ester is such that the acid value of the final composition is in the range of 0.5 to 3.0 meq / g in terms of alkali solubility. Considering that a part of the acid is used for addition to the ethylenically unsaturated compound having a glycidyl group, (meth) acrylic acid is used as the monomer of all the monomers constituting the unmodified acrylic polymer. Of which 20
Preferably, it is about 60 mol%.

Next, the first component in the present invention comprises a carboxyl group derived from (meth) acrylic acid copolymerized in an unmodified acrylic polymer, with a glycidyl group and a C
= C A compound having an unsaturated double bond is added.

Examples of the compound having a glycidyl group and a C ＝ C unsaturated double bond include glycidyl (meth) acrylate, allyl glycidyl ether, vinylbenzyl glycidyl ether and 4-glycidyloxy-3,5-
Glycidyl (meth) acrylate is preferred among these, from the viewpoint that the addition reaction to the acid is easy. In the present invention, since the compound is crosslinked with the second component in a state of being added to the unmodified acrylic polymer, it is considered that heat resistance and moisture resistance are greatly improved.

The amount of the compound having a glycidyl group and a C ＝ C unsaturated double bond is preferably from 5 to 25 mol% of all monomers constituting the unmodified acrylic polymer. If it is less than 5 mol%, heat resistance and moisture resistance will not be sufficiently exhibited, and if it exceeds 25 mol%, (meth) acrylic acid will be excessive in the unmodified acrylic polymer, and the cured product of the resin composition will not be obtained. Both are not preferred because they become brittle.

Next, the polymerizable compound having a C ＝ C unsaturated double bond at the terminal, which is the second component, will be described. It has an acryloyl group and / or a methacryloyl group (hereinafter referred to as "(meth) acryloyl group"), an allyl group or a vinyl group at its terminal, and is polymerized by irradiation with active energy rays such as ultraviolet rays and / or heating. It is a compound that can be used.

Specifically, methyl (meth) acrylate, butyl (meth) acrylate, 2-
Ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth)
Monofunctional (meth) acrylates such as acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate, and compounds having a vinyl group such as styrene and acrylonitrile are exemplified. With two double bonds, 1,3-butanediol di (meth) acrylate,
Di (meth) acrylates such as diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, di (meth) acrylate of bisphenol A type epoxy, and urethane (meth) acrylate;
Alternatively, there may be mentioned allyl compounds such as diallyl phthalate and diallyl ether of bisphenol A. When the number of double bonds is three or more, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like can be mentioned. To impart flame retardancy to the resin composition of the present invention, it is preferable to add a halogenated epoxy acrylate, particularly a brominated epoxy acrylate, as the second component.

When a compound having three or more double bonds among the above polymerizable compounds is used, the crosslink density is increased and the heat resistance is increased, but the cured resin is hard and brittle, and the copper foil and the inner layer plate are hardened. Of the adhesive becomes poor. On the other hand, in the case of a compound having two or less double bonds, the adhesion is improved, but the heat resistance is deteriorated. Therefore, it is preferable to mix and mix three or more compounds and two or less compounds in a range of 30 parts by weight / 70 parts by weight to 70 parts by weight / 30 parts by weight. From the viewpoint of compatibility with the first component, urethane (meth) acrylate or polyethylene glycol di (meth) acrylate is used as the compound having two double bonds, and trimethylolpropane tri (meth) acrylate is used as the compound having three double bonds. Alternatively, pentaerythritol tri (meth) acrylate is preferred. The amount of the second component is preferably in the range of 20 to 50% by weight based on the total amount of the first component and the second component from the viewpoint of heat resistance and adhesion.

Among the polymerization initiators as the third component, aromatic ketones such as benzophenone, Michler's ketone, xanthone, thioxanthone and 2-ethylanthraquinone as polymerization initiators by active energy rays such as ultraviolet rays and electron beams;
Acetophenones such as acetophenone, trichloroacetophenone, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone and the like; benzyl and methyl benzoyl as diketones Formate and the like are included, and the blending amount is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the total amount of the first component and the second component. If the amount is less than 0.5 part by weight, the curing is insufficient and the heat resistance tends to be inferior. . When curing is performed using an electron beam among the active energy rays, the polymerization initiator may be omitted.

Examples of the initiator by heating include an organic peroxide type and an azobis type, and those having a high decomposition initiation temperature are preferable in order to obtain storage stability. Examples include dicumyl peroxide, t-butyl cumyl peroxide,
Examples thereof include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne. The added amount is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the total of the first component and the second component. If the amount is less than 0.5 part by weight, the curing is insufficient and the heat resistance tends to be inferior.If the amount exceeds 10 parts by weight, a large amount of decomposed products remains in the composition, and when heated, the copper foil swells, The effect is manifested and the heat resistance tends to be inferior.

Either active energy rays or heating may be used to cure the resin composition. However, in many cases, heat resistance is not sufficiently increased only with active energy rays. Is preferred.

As the fourth component, an accelerator for active energy ray curing such as ultraviolet rays, Nissocure EPA, EMA, IAMA, EHMA, MABP, E
ABP etc., Kayakua EPA, D made by Nippon Kayaku Co., Ltd.
ETX, DMBI, etc., Ward Blenkinso
p Company's Quantacure EPD, BEA, EOB,
DMB or the like, DABA manufactured by Osaka Organic Chemical Industry Co., Ltd., PAA or DAA manufactured by Daito Chemical Industry Co., Ltd. can be used.
The amount is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the total of the first component and the second component. When the amount is less than 0.5 part by weight, the reaction rate of the active energy ray curing is hardly improved, and when the amount exceeds 10 parts by weight, the reaction is accelerated, and the shelf life tends to be reduced. Since the resin composition B does not require ultraviolet curing, this component may be omitted.

Of the fifth component, the phosphorus-based flame retardant is a phosphorus compound that is generally used frequently as an additive for imparting flame retardancy. Examples thereof include zyl phosphate, cresyl diphenyl phosphate, and tributyl phosphate, and halogen-containing phosphoric esters such as trischloroethylethyl phosphate, trisdichloropropyl phosphate, and tris (tribromophenyl) phosphate. Furthermore, red phosphorus, which is not a compound but pure phosphorus itself, can be used as the fifth component.

The present inventors have found that the combined use of halogenated epoxy acrylate as the second component and phosphorus or a phosphorus-based flame retardant as the fifth component produces a synergistic effect on flame retardancy, and the necessary introduction of both components It has been found that the amount can be reduced and good flame retardancy can be provided without impairing the heat resistance of the resin composition.

The preferred content of halogen and phosphorus in each resin composition used in the present invention is based on the total amount of the first to third components and, if necessary, the fourth and fifth components added. , 2 to 20% by weight of halogen,
It is preferable to use 0.2 to 5% by weight of phosphorus and to use both in this range. If the halogen content is less than 2% by weight, the flame retardancy is insufficient, and if it exceeds 20% by weight, the solder heat resistance deteriorates. When the content of phosphorus is less than 0.2% by weight, the flame retardancy is also insufficient, and when it exceeds 5% by weight, heat resistance, moisture resistance and electric insulation deteriorate. A more preferable halogen content is 8 to 15% by weight, and a more preferable phosphorus content is 0.5 to 2% by weight. Among the halogens, bromine is most preferable from the viewpoint of flame retardancy as described above.

As the conductive material, a conductive paste such as a silver paste, a copper paste or a solder paste is preferably used, but a solder ball may be used by reflowing. The fine holes are filled with a conductive material by screen printing and cured, and the thickness of the conductive bump is formed to be thicker than the thickness of the resin composition A layer. The protruding thickness is formed to be about the thickness of the resin composition B layer of the copper-clad insulating sheet to be laminated. The conductive paste may be a heat-curable type or an active energy ray-curable type such as an electron beam. However, a solvent-free conductive paste has higher dimensional accuracy, and therefore the latter containing no solvent is preferable.
When a solder paste is used, conductivity can be obtained by performing screen printing and then performing solder reflow at 200 to 260 ° C. to melt. It is preferable that the conductive material is completely cured before laminating the copper-clad insulating sheet. However, before lamination, it is roughly cured with an electron beam or the like, and is completely heated and / or irradiated with an electron beam after lamination. It may be cured.

When a copper-clad insulating sheet is laminated under heat and pressure on the surface of the inner layer plate on which the conductive material is formed, the thermoplastic resin composition B causes fluidity, and the conductive material becomes a rough surface of the outer copper foil. Then, the outer copper is electrically connected to the surface. When the resin composition A and the resin composition B are completely cured after lamination, the conductive paste is solidified with the resin.

The thickness of the layer of the resin composition A is from 30 to 100.
μm, the thickness of the layer of the resin composition B is preferably 10 to 50 μm, and the height of the conductive material is preferably 50 to 150 μm.

The conditions for laminating the copper-clad insulating sheet are preferably 60 to 120 ° C. and a roll pressure of 1 to 5 kg / cm ^2, but by vacuum laminating at a reduced pressure of 3.5 torr or less, the lamination boundary It is more preferable because bubbles are prevented from entering.

The complete curing of the resin composition and the conductive material is carried out by heating and / or electron beam. In the case of thermal curing, the temperature is preferably from 160 to 180 ° C. for about 30 to 60 minutes. 10 at 150 to 250 kV
Irradiation of ~ 30 MRad is preferred.

According to the present invention, a multilayer printed wiring board having four layers can be manufactured by laminating a copper-clad insulating sheet on both sides of an inner layer board having a copper foil circuit on both sides. The number of layers can be increased by sequentially laminating the sheets.

[0043]

【Example】

Example 1 (Synthesis of First Component) From 40 parts by weight of n-butyl methacrylate, 15 parts by weight of methyl methacrylate, 15 parts by weight of styrene, 10 parts by weight of hydroxyethyl methacrylate, 20 parts by weight of methacrylic acid and 2 parts by weight of azobisisobutylnitrile The mixture was dropped into 120 parts by weight of propylene glycol monomethyl ether maintained at a temperature of 80 ° C. in a nitrogen gas atmosphere over 5 hours. After aging for 1 hour, 0.5 part by weight of azobisisobutylnitrile was further added and the mixture was aged for 2 hours to synthesize a methacrylic resin having a carboxyl group. Next, while blowing in air, 20 parts by weight of glycidyl methacrylate, 1.5 parts by weight of tetrabutylammonium bromide, and 0.15 parts by weight of hydroquinone as a polymerization inhibitor were added and reacted at a temperature of 80 ° C. for 8 hours to give a molecular weight of 50,000. ~ 70,
000, acid value 1.8 meq / g, unsaturated group concentration 1.14
A base resin (first component) having a carboxyl group of mol / kg was synthesized.

(Preparation of Resin Composition A)
0 parts by weight, pentaerythritol triacrylate (Aronix M-30 manufactured by Toagosei Co., Ltd.) as the second component
5) 20 parts by weight and brominated epoxy acrylate 30
Dicumyl peroxide (Park Mill D, manufactured by NOF Corporation) 1.0 as a thermal polymerization initiator among the parts by weight and the third component
Parts by weight and 2-methyl- [4-
(Methylthio) phenyl] -2-morpholino-1-propanone (Irgacure 907 manufactured by Ciba Geigy Co., Ltd.) 3 parts by weight, and as a fourth component a photopolymerization accelerator ethyl p-dimethylaminobenzoate (Kayacure EPA manufactured by Nippon Kayaku Co., Ltd.)
2 parts by weight and 0.5 part by weight of a phosphate ester-based flame retardant as a fifth component were mixed well to prepare a resin composition A.

(Preparation of Resin Composition B)
0 parts by weight, pentaerythritol triacrylate (Aronix M-30 manufactured by Toagosei Co., Ltd.) as the second component
5) 20 parts by weight and brominated epoxy acrylate 30
Dicumyl peroxide (Park Mill D, manufactured by NOF Corporation) 1.0 as a thermal polymerization initiator among the parts by weight and the third component
By weight, 0.5 part by weight of a phosphate ester-based flame retardant as a fifth component was well mixed to prepare a resin composition B.

(Preparation of Copper-Clad Insulating Sheet) The resin composition B (4) was applied to a roughened surface of a copper foil 8 having a thickness of 35 μm with a bar coater and dried at 80 ° C. for 10 minutes. A copper-clad insulating sheet 7 having a thickness of 15 μm of the thermoplastic resin composition was prepared.

(Preparation of Printed Wiring Board) A 0.6 mm thick glass-epoxy laminate (inner board) having a 35 μm thick copper foil circuit 1 and electrically connecting both-side copper foil with silver paste 3 2, a resin composition A (6) was applied by roll coating and dried at 90 ° C. for 10 minutes to form a copper foil having a thickness of 50 μm on a circuit. Next, a layer of the resin composition A was similarly formed on the opposite surface. Subsequently, the exposed portion was exposed to ultraviolet light except for the portion where the buried via hole was formed through the pattern film, and the unexposed portion was developed with a 1% sodium carbonate solution to form a 0.1 mmφ fine hole 9 for the buried via hole. .625 mm pitch.

Next, a conductive material (electron beam-curable silver paste) 5 (FA-9411 manufactured by Toagosei Co., Ltd.)
Was formed to a thickness of 65 μm by screen printing. Next, the silver paste and the resin composition A were cured by irradiating an electron beam at 175 KV for 10 Mrad. Next, the copper-clad insulating sheet 7 was laminated on both sides of the panel with a hot roll at 90 ° C. Then apply electron beam to both sides at 210K
After irradiation with V for 20 Mrad, the composition was thermally cured at 170 ° C. for 30 minutes. Subsequently, a circuit pattern was formed by etching the outermost copper foil to obtain a multilayer printed wiring board. Electrical continuity was obtained between the copper foil of the inner layer plate and the copper foil of the outermost layer.

The above multilayer printed wiring board was heated at 100 ° C. 30
The test was carried out up to 500 cycles with one cycle at -55 ° C. for 30 minutes, and no abnormality was found in the conduction of the buried via holes. Further, even after 1000 hours after application of 85 ° C., 85% RH, and 30 V, the insulation resistance between the copper foil circuit of the inner layer board and the outer copper foil circuit and the insulation resistance between the buried via holes are 10 ¹⁰ Ω or more. there were. Further, in the solder float test, no abnormality was observed at 260 ° C. for 180 seconds.

[0050]

As described above, in the multilayer printed wiring board of the present invention, a buried via hole having a small diameter can be easily formed with high precision, and a multilayer printed wiring board having high mass productivity and high reliability can be obtained. It is of high industrial value.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a state in which fine holes are provided after a layer of a resin composition A is formed on an inner layer board in a process of manufacturing a multilayer printed wiring board of the present invention.

FIG. 2 is a schematic cross-sectional view showing a state in which a conductive paste is formed in the manufacturing process.

FIG. 3 is a schematic sectional view showing a state before laminating a copper-clad insulating sheet in the same manufacturing process.

FIG. 4 is a schematic cross-sectional view showing a state after laminating a copper-clad insulating sheet in the same manufacturing process.

FIG. 5 is a schematic sectional view showing a state after a circuit pattern is formed by etching an outer layer copper foil in the same manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper foil circuit of inner layer board 2 Inner board 3 Silver paste 4 Thermoplastic resin composition 5 Conductive material 6 Resin composition 7 Copper-clad insulating sheet 8 Copper foil of outer layer 9 Micro hole

Continuation of the front page (72) Inventor Hideki Hiraoka 1 in Funami-cho, Minato-ku, Nagoya-shi, Aichi, Japan

Claims (1)

[Claims] A step of forming a layer of a curable resin composition on a copper foil circuit of an inner layer board having a copper foil circuit on a surface thereof; Exposing the copper foil circuit through the fine holes; curing the curable resin composition; filling the fine holes with a conductive material for interlayer connection and curing; Forming a layer of a thermoplastic curable resin composition having a thickness near the difference between the thickness of the conductive material and the thickness of the layer of the curable resin composition, on the rough surface side of the copper foil. The resin composition side of the copper-clad insulating sheet formed on the inner layer plate is hot-pressed and laminated on the surface of the inner layer plate on which the conductive material is formed. A step of electrically connecting the copper foil; a step of curing the thermoplastic curable resin composition And a method for manufacturing a multilayer printed wiring board.