JP2002204069A - Conductive connection method between metal layers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive connection method between metal layers which keeps a durability and a good reliability of a conductive connection and reduces the number of steps and the raw material cost. SOLUTION: The conductive connection method between metal layers comprises a step of forming a thermosetting resin layer 4 partly exposed at the surface of a porous resin layer 3 laminated on a first metal layer 1, a step of forming an opening 5 extending from the surface of the resin layer 4 to the first metal layer 1, a step of filling the opening 5 with a conductive paste 6 with the surface height approximately equal to the height of the surrounding object and a step of hot pressing the filled laminate together with a second metal layer 2, hereby reducing the total thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for conductively connecting metal layers by filling a conductive paste in a via hole formed in an insulating layer and electrically connecting the metal layers to each other. Useful for the production of

[0002]

2. Description of the Related Art Conventionally, in a process of forming a base layer and an insulating layer of a printed wiring board used for electronic equipment and the like, a thermosetting resin is impregnated into a glass fiber woven fabric or a polymer nonwoven fabric and the like. Cured prepregs and the like have been used. Usually, prepreg is used by being laminated on copper foil, for example,
A multilayer structure in which a wiring layer and an insulating layer are sequentially laminated by repeating the steps of laminating and curing the underlying wiring layer and the like by hot-pressing the laminate and the step of forming a wiring pattern on the copper foil. Is formed. A laminate in which copper foil is laminated on both sides of a prepreg by hot pressing is used for a core substrate of a multilayer wiring substrate or a double-sided wiring substrate.

As a method of conductively connecting these wiring layers or metal layers before forming a wiring pattern, there is known a method of filling a via hole formed in an insulating layer with a conductive paste and conductively connecting the metal layers. Have been. Specifically, as shown in FIGS. 2A to 2E, in a state where the resin film 13 is further laminated on the prepreg 10 laminated on the copper foil 11, an opening reaching the copper foil 11 by laser via processing. After the conductive paste 6 is formed, the inside of the conductive paste 6 is filled with a conductive paste 6 by screen printing or the like, and the resin film 13 is peeled off to make the surface of the conductive paste 6 convex.
It is known that the copper foils 12 are laminated so as to be in pressure contact with each other and hot-pressed to electrically connect the copper foil layers.

[0004]

However, the method of laminating a resin film on a prepreg and peeling it after filling with a conductive paste as described above increases the number of steps and increases the cost by the amount of the resin film. There's a problem. Unless the resin film is laminated and peeled off, the convex portion of the conductive paste is not formed, the pressure contact force between the conductive paste and the copper foil becomes insufficient, and the durability and reliability of the conductive connection between the wiring layers are reduced. Problems, such as a decrease in performance, are likely to occur.

Accordingly, an object of the present invention is to provide a conductive connection method between metal layers which can reduce the number of steps and material costs while maintaining good durability and reliability of the conductive connection.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a method of making conductive connection between metal layers without laminating a resin film for forming a convex portion of a conductive paste. By forming a thermosetting resin layer so that a part thereof is exposed on the surface side of the layer, and simultaneously performing impregnation of the exposed portion and consolidation of the conductive paste during conductive connection by hot pressing, The inventors have found that the object can be achieved, and have completed the present invention.

That is, according to the method for electrically connecting between metal layers of the present invention, a thermosetting resin layer is formed so that at least a part thereof is exposed on the surface side of the resin porous layer, and the laminate is formed together with the metal layer. The thickness of the whole is reduced by hot pressing, and the conductive paste filled in the opening of the laminate is consolidated.

According to the present invention, there is provided a step of forming a thermosetting resin layer so that at least a portion thereof is exposed on a surface side of a resin porous layer laminated on a first metal layer, and a step of forming a surface of the thermosetting resin layer. Forming an opening from the first metal layer to the first metal layer;
A step of filling the opening with a conductive paste so that the surface height is substantially the same as the surrounding height, and a step of hot-pressing the filled laminate together with the second metal layer to reduce the overall thickness. It is preferable to include

In the above method, when forming the thermosetting resin layer, a solid coating film obtained by applying a raw material liquid on the surface of a base material and drying is transferred to a surface portion of the porous resin layer. Is preferred.

According to the conductive connection method between metal layers of the present invention, a thermosetting resin layer is formed so that at least a part thereof is exposed on the surface side of the resin porous layer, and the laminate is formed. A resin film for forming a convex portion as in the prior art in order to reduce the overall thickness by hot pressing together with the metal layer and to consolidate the conductive paste filled in the openings of the laminate. Without laminating and peeling
At the time of conductive connection, a sufficient pressure contact force can be obtained between the metal layer and the conductive paste. As a result, the number of steps and material costs can be reduced while maintaining good durability and reliability of the conductive connection.

In particular, when the above steps are included, a thermosetting resin layer is formed so that a part thereof is exposed on the surface side of the resin porous layer, and a conductive paste is provided in an opening of the thermosetting resin layer. While the exposed portion of the thermosetting resin layer is impregnated inside the porous resin layer during conductive connection by hot pressing, so it is equivalent to the height of the exposed portion. To this extent, the conductive paste is consolidated.

In the case where the thermosetting resin layer is formed, a solid coating film obtained by applying a raw material liquid on the surface of a base material and drying is transferred to a surface portion of the porous resin layer. In comparison with the method of directly applying the raw material liquid to the surface of the resin porous layer, it is easier to form the thermosetting resin layer so that the thickness of the exposed portion is uniform, and as a result, the metal layer and the conductive paste Is uniform, and the durability and reliability of the conductive connection can be further improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) to 1 (e)
FIG. 2 is a process chart showing an example of a method for conductively connecting metal layers according to the present invention.

In the present embodiment, as shown in FIG. 1A, the thermosetting resin layer 4 is formed so that at least a part thereof is exposed on the surface side of the resin porous layer 3 laminated on the first metal layer 1. Is formed. In the present invention, the entire thermosetting resin layer 4 may be exposed from the resin porous layer 3 and adhered at the interface between them, and conversely, substantially the entire thermosetting resin layer 4 is formed of the resin porous layer. 3 may be impregnated.

However, in the present invention, the thickness of the exposed portion of the thermosetting resin layer 4 depends on the thickness and the porosity of the resin porous layer 3, but is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm. More preferred. If the thickness of the exposed portion is too small, the pressing force between the metal layer and the conductive paste and the compaction of the conductive paste tend to be insufficient.If the thickness of the exposed portion is too large, the thermosetting The exposed portion of the resin layer 4 tends to remain on the surface without being impregnated.

The step of forming the thermosetting resin layer 4 includes:
A method in which the raw material liquid of the thermosetting resin layer 4 is directly applied to the surface of the resin porous layer 3 by various coaters or the like may be used. However, as described above, the raw material liquid is applied to the surface of the base material and dried. A method of transferring the solid coating film onto the surface of the resin porous layer 3 is preferable. The thickness of the exposed portion can be adjusted by the thickness of the solid coating film and the amount of impregnation at the time of transfer.

Examples of the material of the substrate include various resins, metals, glasses and the like, and those having a smooth surface are preferable. The shape of the substrate may be any of sheet, plate, roll, belt and the like. The substrate is particularly preferably a resin film.

Examples of such a resin film include polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polyamide films and polyimide films. In addition, the surface to be coated may be subjected to a release treatment or the like so that it is easily peeled in a later step.

Examples of the thermosetting resin include an epoxy resin, a phenol resin, a polyimide resin, and a polyamic acid. An epoxy resin or a mixture of an epoxy resin and another resin is preferable from the viewpoint of cost and ease of handling. The raw material liquid of the thermosetting resin may contain a catalyst, a curing agent, a flame retardant, a filler, a plasticizer, an accelerator and the like in addition to the solvent.

The solvent contained in the raw material liquid of the thermosetting resin depends on the type of the thermosetting resin, but includes ketones, acetates, ethers, aromatic hydrocarbons, alcohols and the like. The content of the solvent is preferably 1 to 60% by weight in the raw material liquid in view of the time required for drying and the like and the ease of application.

Examples of the coating method include a coating method using a blade coater, a comma coater, a roll coater, a calendar coater, and a bar coater. The coating thickness is
The thickness of the solid coating is appropriately determined depending on the amount of the contained solvent according to the thickness of the solid coating described later. The more uniform the thickness, the more uniform the thickness of the solid coating and the more uniform the impregnation amount.

In the drying of the solvent, it is not necessary to completely remove the solvent, and the solvent may be non-fluidized. As a drying method, heat drying or hot air drying is preferable in terms of efficiency. As the heating temperature, a temperature at which the curing reaction of the thermosetting resin does not proceed excessively is selected.

The transfer method may be such that at least a part of the solid coating is impregnated by heating and laminating the solid coating together with the base material on the porous film and pressing. The heating of the solid coating film can be performed by various heaters, and the heating temperature is selected so that the solid coating film is softened to the extent of impregnation and the curing reaction of the thermosetting resin does not proceed too much.

As a method of laminating and pressurizing while heating, various hot presses and heat laminators, a device having a vacuum exhaust device added thereto, or a function of heating and pressurizing the above-mentioned coated base material can be used. A method using an applied device or the like can be used. In the present invention, it is preferable to use a thermal laminator.

The resin porous layer 3 laminated on the first metal layer 1
As a method in which a porous film is formed directly on a metal foil, or a method in which a metal film is laminated after forming a porous film, any of them may be used. It is preferable to use

As the material of the porous film, a resin having good heat resistance and mechanical strength is preferable, and various materials such as polyimide, polyester, polyamide, especially aromatic polyamide, polyamideimide, polyetherimide, polyethersulfone and the like can be used. Resin can be employed. Among these resins, polyimide resins are preferable because they have good insulation and heat resistance and good adhesion to the metal layer. Aromatic polyamide is also preferable because it has good insulation and heat resistance and has a low coefficient of linear thermal expansion.

In particular, when a porous film of an aromatic polyimide is used, it is often heated to a high temperature during the imide conversion. Therefore, it is preferable to use a metal or the like having a high heat resistance as a substrate at the time of film formation.

Various materials such as copper, copper, bronze, bronze, brass, aluminum, nickel, iron, stainless steel, gold, silver, and platinum are used as the material of the first metal layer 1 (metal serving as a film forming base material). it can. These may be either a metal foil or a metal plate, and the thickness thereof is preferably 1 to 50 μm. In the present invention, it is particularly preferable to use a copper foil suitable as a wiring pattern of a wiring board. The surface of the metal foil may be subjected to various physical or chemical surface treatments such as a surface roughening treatment and a blackening treatment in order to enhance the adhesion to the porous film.

A resin film can be used as the film-forming substrate. As the resin film, the same resin film as the above-mentioned resin film for the coating substrate can be used, but other film-forming substrates can also be used. it can.

The porous film may be formed by various film forming methods such as a wet coagulation method, a dry coagulation method, and a stretching method. The wet coagulation method is preferable because an open-cell porous film can be easily obtained. In the wet coagulation method, in general, a film-forming stock solution (dope) in which a resin and additives are dissolved in a solvent is prepared, and the solution is applied (cast) to a film-forming base material and immersed in the coagulation solution to form a solvent. By substituting, the resin is solidified (gelled), and then the coagulation liquid or the like is dried and removed to obtain a porous film.

The polyimide resin may contain another copolymer component or a blend component as long as it is mainly composed of a repeating unit in which an acid residue and an amine residue are imide-bonded. Preferably, it is a polyimide having an aromatic group in the main chain from the viewpoint of heat resistance, hygroscopicity, and mechanical strength, and examples thereof include a polyimide comprising a polymer of a tetracarboxylic acid component and an aromatic diamine component. In particular,
A polymer having an intrinsic viscosity (measured at 30 ° C.) of 0.55 to 3.00, preferably 0.60 to 0.85 is desirable. Those having an intrinsic viscosity in the above range,
When a porous film is formed by a wet coagulation method, a self-supporting porous film having good solubility in a solvent and high mechanical strength is obtained.

As the polyimide resin, the polymer or its precursor (polyamic acid) can be used, but since polyamic acid has higher solubility than polyimide, there is an advantage that there is little restriction on the molecular structure. There is. The polymer is preferably completely imidized, but may be one having an imidation ratio of 70% or more. When a material having a relatively high imidation ratio is used for dope, it is preferable to use a polymer containing a highly flexible component such as butanetetracarboxylic dianhydride in a repeating unit.

The solvent for dissolving the polyimide resin or its precursor is not particularly limited as long as it can dissolve them, but N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide And an aprotic polar solvent such as dimethyl sulfoxide can be preferably used from the viewpoint of solubility and the speed of solvent replacement with a coagulating solvent when a porous film is formed by a wet coagulation method. Preferred examples include N-methyl-2-pyrrolidone. Further, a solvent such as diethylene glycol dimethyl ether or diethylene glycol diethyl ether may be mixed to adjust the solvent replacement rate in the wet coagulation method.

Examples of the aromatic polyamide include so-called para-type aramid and meta-type aramid, those in which a part of the skeleton is substituted with diphenylether, diphenylpropane, diphenylmethane, diphenylketone, diphenylsulfoxide, biphenyl, etc., and aromatic ring hydrogen. Examples thereof include those obtained by substituting a group with a methyl group, a halogen atom, or the like.

Examples of the para-type aramid include poly-p-phenylene terephthalamide and the like. Aramid composed of only a rigid component such as this polymer needs to be dissolved with a special agent. Therefore, as the aromatic polyamide used for the porous film, it is preferable to use at least a part of an aramid or a meta-aramid whose skeleton is partially substituted with a component imparting flexibility. Examples of the component that imparts flexibility include m-phenylene, 2,7-naphthalene, diphenyl ether, 2,2-diphenylpropane, and diphenylmethane. Such a component is used as a dicarboxylic acid monomer or a diamine monomer in the copolymerization and is introduced into the skeleton. Generally, the higher the copolymerization ratio of the component, the higher the solubility in a solvent.

Solvents for dissolving the aromatic polyamide include, for example, tetramethylurea, hexamethylphosphoramide, N, N-dimethylacetamide, N
-Methyl-2-pyrrolidone, N-methylpiperidone-
2, N, N-dimethylethylene urea, N, N, N ',
N′-tetramethylalonamide, N-methylcaprolactam, N-acetylpyrrolidine, N, N-diethylacetamide, N-ethylpyrrolidone-2, N, N-dimethylpropionamide, N, N-dimethylisobutylamide, Examples include N-methylformamide, N, N-dimethylpropylene urea, and mixtures thereof. Further, aprotic polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide and N, N-dimethylformamide can be preferably used from the viewpoint of solubility and the speed of solvent replacement with a coagulating solvent. . A particularly preferred example is N-methyl-2-pyrrolidone.

Further, a solvent such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether or the like may be mixed to adjust the rate of solvent replacement.

When a polyimide resin is used,
The dope in the wet coagulation method is preferably -20 to 40.
It is applied in a temperature range of ° C. Further, as the coagulation liquid, without dissolving the resin to be used, as long as it has compatibility with the above-mentioned solvent, water, methanol, ethanol, alcohols such as isopropyl alcohol and a mixture thereof are used. In particular, water is preferably used. The temperature of the coagulating liquid at the time of immersion is not particularly limited, but is preferably a temperature of 0 to 90 ° C.

The polymer concentration of the stock solution is preferably in the range of 5% to 25% by weight, more preferably 7% to 20% by weight.
Is more preferred. If the concentration is too high, the viscosity becomes too high and handling becomes difficult. If the concentration is too low, a porous film tends to be difficult to form.

An inorganic substance such as lithium nitrate and an organic substance such as polyvinylpyrrolidone can be added for controlling the pore shape and pore diameter. The concentration of the additive is preferably from 1% by weight to 10% by weight in the solution. When lithium nitrate is added, the replacement speed between the solvent and the coagulating liquid is high, and a finger void structure (a structure having finger-like voids) can be formed in the sponge structure. By adding an additive such as polyvinylpyrrolidone which slows down the coagulation speed, a porous film having a sponge structure uniformly spread can be obtained.

Before immersion in the coagulating liquid, for example, 30
The pore size of the porous film near the surface may be controlled by allowing the dope to absorb moisture and the like by leaving it in an atmosphere at a temperature of 90 ° C. or higher and a relative humidity of 90% or higher for a predetermined time (for example, 1 second to 10 minutes). For example, by this operation,
In some cases, even with a dope composition that forms a skin layer on the surface, the pore size can be increased to some extent.

The dope is applied to a certain thickness and immersed in a coagulating liquid such as water to coagulate, or left in a steam atmosphere to coagulate, and then immersed in water to remove the solvent. It becomes a porous film. After the formation of the porous film, it is taken out of the coagulation liquid and dried. The drying temperature is not particularly limited, but drying at 200 ° C. or less is desirable.

When a precursor (polyamic acid) is used when forming a porous film of a polyimide resin, the precursor (polyamic acid) is finally heat-treated at 200 to 500 ° C., and the precursor (polyamic acid) is heated and closed. To polyimide.

The back surface of the porous film preferably has an average pore diameter of 0.05 μm or more. More preferably 0.1 to
5 μm. Further, the size of the pores in the sponge structure portion (inside) may be 0.05 μm to 10 μm,
Preferably it is 1 μm to 7 μm. In the finger void structure, the average pore diameter is preferably 0.05 μm to 10 μm. The porosity of the porous film is 30 to 98%.
Is preferable, and 40 to 70% is more preferable.

In this embodiment, as shown in FIG. 1B, a step of forming an opening 5 from the surface of the thermosetting resin layer 4 to the first metal layer 1 is included. The opening 5 only needs to expose a part of the surface of the first metal layer 1 on the bottom surface thereof.
It is preferable that the entire opening area of the first metal layer 1 is exposed.

When the opening area is large, the opening 5 can be formed by drilling or the like controlled by a computer. However, usually, laser processing using various lasers such as a YAG laser is performed. Any conventional method can be applied to the laser processing method and conditions. Note that the thermosetting resin layer 4 also has a role of protecting the resin porous layer 3 below it during laser processing.

In this embodiment, as shown in FIG. 1C, a step of filling the opening 5 with the conductive paste 6 so that the surface height is substantially equal to the surrounding height is included. In the present invention, since the porous portion is present around the opening 5, when filling the conductive paste 6, problems such as generation of voids due to remaining bubbles and the like hardly occur.

Examples of the conductive paste 6 include those in which fine particles such as silver, copper, carbon, and solder are dispersed in a binder resin or a solvent. As the binder resin, a thermosetting resin is suitably used, and a curing reaction proceeds by a hot press described later. The average particle diameter of the fine particles is preferably larger than the average pore diameter of the resin porous layer 3.

The conductive paste 6 can be filled by printing such as screen printing, offset printing, pad printing, ic jet printing, bubble jet (registered trademark) printing, or by filling with squeeze. In addition, if the conductive paste remains on the surface other than the opening 5 after filling, a short circuit may be caused. Therefore, a process for removing the conductive paste remaining on the surface may be performed. In addition,
A peelable layer may be provided on the surface of the thermosetting resin layer 4, and the layer may be peeled after filling the conductive paste 6.

As shown in FIGS. 1D to 1E, the present embodiment includes a step of hot-pressing the filled laminate together with the second metal layer 2 to reduce the overall thickness. By this step, the exposed portion of the thermosetting resin layer 4 is
Of the conductive paste 6 (the resin porous layer 3 ′ after the impregnation), the conductive paste 6 is compacted by an amount corresponding to the height of the exposed portion, and the conductive paste 6 and the metal layers The pressing force with the second member 2 is increased.

Various presses such as a vacuum press, a hot press, and a continuous press can be used for the hot press. However, in order to prevent air bubbles inside the laminate,
A vacuum press is preferred.

As the conditions for the hot pressing, heating conditions under which the thermosetting resin layer 4 is sufficiently softened so as not to consolidate the non-impregnated resin porous layer are preferable. Preferably, 100-200 degreeC is more preferable. Further, the press pressure is preferably 1 to 10 MPa.

[Other Embodiments] Hereinafter, other embodiments of the present invention will be described.

(1) In the above-described embodiment, an example in which the thermosetting resin layer is formed on the surface side of the resin porous layer previously laminated on the first metal layer has been described. The order of the laminating step may be performed in any order as follows.

For example, after the step of forming a thermosetting resin layer, after the step of forming an opening, after the step of filling a conductive paste, or when hot-pressing the filled laminate with a metal layer And so on.

That is, according to the method for electrically connecting the metal layers of the present invention, a thermosetting resin layer is formed so that at least a part thereof is exposed on the surface side of the resin porous layer, and the laminate is formed together with the metal layer. Any material may be used as long as it reduces the overall thickness by hot pressing and consolidates the conductive paste filled in the openings of the laminate.

(2) In the above-described embodiment, an example in which the thermosetting resin layer is formed on one surface side of the resin porous layer has been described, but the thermosetting resin layer is formed on both surface sides of the resin porous layer. A layer may be formed, and the laminate may be hot-pressed together with the metal layer to impregnate the inside of the porous resin layer with the thermosetting resin layer from both sides.

A laminate having a thermosetting resin layer interposed between a resin porous layer and a metal layer is formed, and the laminate is hot-pressed together with another metal layer to form a thermosetting resin. The resin layer may be impregnated inside the resin porous layer.

[0059]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the average pore diameter and the porosity of the porous film were measured as follows.

(1) Average Pore Size of Porous Film Using a scanning electron microscope (SEM), photographs of the surface and the cross section were taken, and the average pore size was determined from image analysis of the photographs using a computer.

(2) Porosity of Porous Film Porosity (%) = {(weight / density) / volume} × 100 The volume and weight of the porous film were measured, and the above equation was obtained using the density of the material. Was used to determine the porosity.

[Preparation Example of Aramid Porous Film] An aromatic polyamide (manufactured by Teijin Limited, Conex) was converted to N-
Dissolved in methyl-2-pyrrolidone (NMP), further added polyvinylpyrrolidone (PVP) (K-90, manufactured by ASP Japan Co., Ltd.) and water, and added aromatic polyamide (100 parts by weight), NMP (900 Parts by weight), PVP
(40 parts by weight) and a polymer solution of water (40 parts by weight) were obtained. This was applied on a polypropylene film (thickness: 30 μm) with a thickness of 30 μm, and then immediately immersed in a water bath at 60 ° C. to form a porous film. Then 1
It was stored in water day and night to remove the solvent. The resulting porous body is
It had a sponge structure in which continuous holes having a thickness of 30 μm were formed. The average pore size was 0.2 μm, and the porosity was 50%. [Adhesive Preparation Example 1] A thermosetting epoxy adhesive 1 (resin solid content: 20% by weight) having the following composition was prepared. Epoxy resin 169 parts by weight (E1032H60, manufactured by Yuka Shell Epoxy Co., Ltd.) Phenol resin (Tamanol P-180, manufactured by Arakawa Chemical Co., Ltd.) 111 parts by weight Methyl ethyl ketone (MEK) 1120 parts by weight [Example 1] PET film having a thickness of 23 μm The above-mentioned thermosetting epoxy adhesive 1 was applied thereon at a thickness of about 75 μm, and dried by a dryer at 80 ° C. for 15 minutes to fix the epoxy adhesive on the PET film (solvent remaining 1% by weight). ). The thickness of the epoxy adhesive layer was about 15 μm. The epoxy adhesive surface of this PET film with an epoxy adhesive and the aramid surface of the aramid porous film are brought into close contact with each other, and are laminated by a heat laminator under the conditions of 90 ° C. × 0.3 m / min and a pressure of 1 MPa. A porous substrate was manufactured. The overall thickness of the manufactured porous substrate with adhesive (including upper and lower PP and PET film layers) is about 98μ.
m.

The PP film of the porous substrate with an adhesive was peeled off, the peeled surface was brought into close contact with a 35 μm copper foil, and laminated with a heat laminator at 100 ° C. × 0.3 m / min. did. After peeling off the PET film, the epoxy adhesive layer was transferred onto the aramid porous substrate. A via having a hole diameter of about 50 μm was opened from the epoxy adhesive layer side with a YAG laser. A conductive paste (solder powder (average particle size of about 8
μm) 50 vol% and solvent 50 vol%) were filled into the vias by screen printing, and then 35 μm
m copper foil laminated, 50 ℃ × 0.5m with a heat laminator
/ Min. The total thickness of the sample after lamination was about 115 μm. This sample was hot-pressed by a vacuum press under the conditions of a chamber pressure of 3 torr, a heating temperature of 180 ° C., and a press pressure of 20 kg / cm ² , to produce a double-sided copper foil substrate. The overall thickness of the manufactured double-sided copper foil substrate was reduced to about 100 μm.

Example 2 P of the above aramid porous substrate
The P film was peeled off, the peeled surface was brought into close contact with the 35 μm copper foil, and laminated with a hot laminator at 80 ° C. × 0.3 m / min. The above-mentioned thermosetting epoxy adhesive 1 was applied on an aramid porous film laminated on a copper foil by 7
It was applied at a thickness of 5 μm and dried at 80 ° C. for 15 minutes using a drier. The thickness of the entire sample after drying was about 75 μm because a part of the epoxy adhesive was impregnated in the aramid porous substrate. Y from epoxy adhesive application side
Vias having a hole diameter of about 50 μm were opened by an AG laser.
Conductive paste (Solder powder 5) from the epoxy adhesive layer surface
(0 vol%, solvent 50 vol%) was filled into the via by screen printing, and then a 35 μm copper foil was laminated on the epoxy adhesive layer surface, and then heated at 50 ° C. × 0.5 m / min with a laminator.
Were laminated under the following conditions. The total thickness of the sample after lamination was about 110 μm. The sample was subjected to a chamber pressure of 3 torr and a heating temperature of 18 using a vacuum press machine.
Hot pressing was performed under the conditions of 0 ° C. and a pressing pressure of 20 kg / cm ² to produce a double-sided copper foil substrate. The overall thickness of the manufactured double-sided copper foil substrate was reduced to about 100 μm.

COMPARATIVE EXAMPLE 1 A thermosetting epoxy adhesive 1 shown in Table 1 was directly applied on a 35 μm copper foil to a thickness of 75 μm, and dried at 80 ° C. for 15 minutes with a drier. The total thickness after drying was about 50 μm. A 25 μm-thick polyimide film Kapton 100H (manufactured by Du Pont-Toray Co., Ltd.) was brought into close contact with the epoxy adhesive and laminated with a heat laminator at 50 ° C. × 0.5 m / min. The thermosetting epoxy adhesive 1 shown in Table 1 was directly applied to the surface of the polyimide film at a thickness of 75 μm, and dried at 80 ° C. for 15 minutes using a drier. The total thickness at this time was about 90 μm. YAG from epoxy adhesive coated side
Vias having a hole diameter of about 50 μm were opened by laser. Conductive paste (Solder powder 50vo) from the epoxy adhesive layer surface
(1%, solvent: 50 vol%) was filled into the via by screen printing, and then a 35 μm copper foil was laminated on the epoxy adhesive layer surface, and laminated by a thermal laminator at 50 ° C. × 0.5 m / min. The overall thickness of the sample after lamination was about 125 μm. This sample was subjected to a chamber pressure of 3 torr and a heating temperature of 180 using a vacuum press machine.
Hot pressing was performed at a temperature of 20 ° C. and a pressing pressure of 20 kg / cm ² to produce a double-sided copper foil substrate. The overall thickness of the produced double-sided copper foil substrate was almost the same as before hot pressing.

Test Example In order to compare the connection reliability of the double-sided copper foil substrates manufactured in Examples 1 and 2 and Comparative Example 1, a thermal shock test was performed under the following conditions. That is, −65 ° C. × 3
0 min and 125 ° C. × 30 min were repeated 1000 cycles, and the resistance values before and after that were measured.

Table 1 shows the results.

[0068]

[Table 1] As is clear from the results shown in Table 1, according to the embodiment of the present invention, the resistance value hardly decreases by the thermal shock test, and the durability and reliability of the conductive connection are improved. On the other hand, in Comparative Example 1 in which the conductive paste is not pressed against the metal layer, the resistance value in the thermal shock test decreases, and the durability and reliability of the conductive connection decrease.

[Brief description of the drawings]

FIG. 1 is a process diagram showing an example of a method for conductive connection between metal layers of the present invention.

FIG. 2 is a process diagram showing an example of a conventional conductive connection method between metal layers.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first metal layer 2 second metal layer 3 resin porous layer 4 thermosetting resin layer 5 opening 6 conductive paste

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shinji Tahara 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 5E317 AA24 BB01 BB03 BB12 BB14 BB18 BB22 CC22 CC25 GG03 GG17 5E346 AA06 AA12 AA15 AA22 AA32 AA42 AA43 AA51 CC02 CC10 CC32 CC38 CC39 CC40 DD02 EE06 EE09 EE13 EE18 FF18 GG15 GG19 GG28 HH11 HH31

Claims (3)

[Claims] 1. A thermosetting resin layer is formed so that at least a part thereof is exposed on the surface side of a resin porous layer, and the laminate is hot-pressed together with a metal layer to reduce the overall thickness. A conductive connection method between the metal layers for consolidating the conductive paste filled in the openings of the laminate. 2. A step of forming a thermosetting resin layer such that at least a part thereof is exposed on a surface side of a resin porous layer laminated on a first metal layer; A step of forming an opening reaching the first metal layer, a step of filling the opening with a conductive paste so that the surface height thereof is substantially equal to the height of the surroundings, and a step of filling the filled laminate with the second metal Hot pressing with the layers to reduce the overall thickness. 3. The method according to claim 1, wherein, when forming the thermosetting resin layer, a solid coating film obtained by applying a raw material liquid on a surface of a substrate and drying is transferred to a surface portion of the resin porous layer. Item 1
Or the conductive connection method between metal layers according to 2.