JP2002344103A - Multilayered sheet and via hole-filled double-sided board and via hole-filled double-sided printed board using the sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board having via hole connections which are improved in conductivity by making conductive powder packed in via holes compact by compressing the powder without causing falling and missing of conductive paste containing a wide variety of base materials or allowing the paste to infiltrate into the gap between copper foil and an insulating film in the compacting step at the time of forming the via hole connection by using the conductive paste. SOLUTION: In a multilayered sheet, peelable films 2 are laminated upon both surfaces of an insulating sheet 1 composed of an insulating resin. The multilayer sheet has through holes 3 which have larger diameters in the peelable films 2 than those in the insulating sheet 1 and are filled up with the conductive paste 4 containing conductive powder and thermosetting resin while the paste 4 is maintained in a semi-hardened state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer sheet comprising an insulating sheet made of an insulating resin and releasable films laminated on both sides, a via-hole-filled double-sided board using the same, and a via-hole-filled double-sided print. The present invention relates to a substrate, a multilayer printed circuit board filled with via holes, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a technique of using a conductive paste for electrical connection between layers in a double-sided printed circuit board and a multilayer printed circuit board has been actively adopted and attracted attention. The greatest advantage of interlayer connection by filling via holes with conductive paste is that a stacked via structure can be formed in a simple process compared to a general printed wiring board method using plating. In addition, since via holes can be arranged at arbitrary positions in each layer, the degree of freedom in circuit design is increased, which is effective in greatly improving wiring density and mounting density.

Further, a method of increasing the compactness of a conductive cured product when the conductive paste is filled into a via hole and then pressurizing and curing the same to increase the volume fraction of the conductive powder in the entire cured product is disclosed in US Pat. Japanese Patent No. 0260128 and Japanese Patent Application Laid-Open No.
No. 8 is known. As the former method, a porous substrate having a compressibility with a release film,
A through hole for a via hole is made by a laser or the like, and then a conductive paste is printed and filled in the through hole, and after the release film is peeled off, copper foil is overlaid on both surfaces of the porous base material and heated and pressed to compress. At this time, by using a porous substrate having a high compression ratio, the substrate thickness after pressing becomes smaller than before pressing and the volume of the via hole is reduced, so that the conductive powder is densified and the laminated copper It is possible to manufacture a double-sided copper-clad laminate in which the conductive paste hardened in the via hole and the via hole is electrically connected with high conductivity. By pattern-etching this double-sided copper foil, a double-sided printed board filled with via holes can be manufactured. A multilayer circuit board can be manufactured by alternately pressing and laminating the double-sided printed circuit board thus manufactured and the intermediate base material filled with the conductive paste on the porous base material.

[0004] In the latter method, a resin film is bonded to an insulating substrate containing an organic resin to form a via hole, and then filled with a conductive paste, the film is peeled off, and the conductor end is projected from the insulating substrate. In this case, a wiring layer pre-patterned is overlapped and compressed and filled, thereby embedding the wiring layer in the insulating resin substrate and compressing and filling the conductor to reduce the resistance of the via hole. These methods can print and fill the via holes without deteriorating the fluidity of the conductive paste, increase the compressibility of the base material and the conductive paste, and enable interlayer connection with a low resistance value. It is excellent in production efficiency in that the number of steps does not increase even if the number of layers increases.

[0005]

However, in the method using a porous substrate, the selection of a substrate for obtaining an appropriate porosity is restricted, and a special step for obtaining a porous material is required. Consideration is required, such as in the production of multilayer printed circuit boards that require insulating substrates that do not take the form of prepreg or non-compressible insulating substrates without using cloth or nonwoven fabric that tends to be porous. It was not applicable and lacked versatility.

In the case of a porous base material having compressibility, a process of using a change in thickness to increase conductivity is used, and thus a device using a cloth or a nonwoven fabric to maintain a dimensional change in a planar direction. Is required, which is disadvantageous for producing a substrate having a higher density than a substrate having no compressibility. In the method of transferring and embedding the wiring layer in the conductive paste protruding from the other insulating substrate, the conductive paste bleeds into a gap between the insulating base plate and the wiring layer when pressurizing, and the via-via Anxiety such as short circuit between via and wiring could not be denied.

Further, in both of these methods, when the film laminated on the insulating resin is peeled off, the filled conductive paste is carried away to the film side, and the compressed paste is lacking in a stable compression filling property. There has been a problem that the paste thus peeled off from the insulating base material and a fatal defect such as a lack of conductivity is likely to occur. In addition, as the thickness of the insulating layer and the diameter of the via hole are further reduced in the trend of becoming lighter and thinner, it is strongly desired to solve the problem of the filled conductive paste falling off.

[0008]

Means for Solving the Problems In view of such problems, the present inventors have conducted intensive studies, and as a result, using a multilayer sheet in which releasable films are laminated on both sides of an insulating sheet made of an insulating resin, A through hole is formed so as to penetrate the multilayer sheet, the opening diameter of the peelable film in the through hole is larger than the opening diameter of the insulating sheet, and conductive powder is provided in the through hole. By filling the conductive paste made of thermosetting resin and semi-cured, the semi-cured conductive paste easily protrudes without dropping off to the via hole sites on both sides of the insulating sheet after the film is peeled off. When the copper foil is bonded and heated and pressed to form a double-sided printed circuit board, the conductive powder is compressed into the via hole without the paste bleeding into the gap between the copper foil and the insulating sheet. However, it is possible to inter-connect with a high conductivity, duplex and multi-layer printed circuit board produced by this process as to solve the above problems, have completed the present invention.

That is, the present invention is as follows. The multilayer sheet according to claim 1, wherein a peelable film is laminated on both sides of an insulating sheet made of an insulating resin, wherein the multilayer sheet has a through-hole, and the through-hole is formed by the peeling. An opening diameter of a possible film is larger than an opening diameter of the insulating sheet, and a conductive paste having a conductive powder and a thermosetting resin is filled in a semi-cured state. In addition, the via hole filling type double-sided substrate according to claim 2 is characterized in that the peelable film of the multilayer sheet according to claim 1 is removed, copper foil is adhered to both sides, and hot pressing is performed.

According to a third aspect of the present invention, there is provided a via-hole-filled double-sided printed circuit board, wherein the copper foil of the via-hole-filled double-sided board is patterned and electrically connected to the conductive paste. Features. According to a fourth aspect of the present invention, there is provided a via-hole-filled multilayer printed circuit board, wherein a plurality of the via-hole-filled double-sided printed boards according to the third aspect are stacked and electrically connected between the multilayers.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a double-sided printed circuit board filled with a via hole, wherein the peelable film is formed on a multilayer sheet in which a peelable film is laminated on both sides of an insulating sheet made of an insulating resin. An opening diameter is provided with a through hole larger than the opening diameter of the insulating sheet, the through hole is filled with a conductive paste having a conductive powder and a thermosetting resin in a semi-cured state, and the peelable film is removed. It is characterized in that copper foil is bonded to both sides by a hot press, and the copper foil is patterned and electrically connected to the conductive paste.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The insulating sheet used in the present invention is not particularly limited with respect to its material and structure, as long as it is a generally known substrate.
Either can be used. Typical examples of the material include glass epoxy resin, paper phenol resin, paper epoxy resin, polyimide resin, polyester resin, BT resin resin, polyphenylene sulfide resin, polyphenylene ether resin, and poly. Ether ketone resin, polyetherimide resin,
A substrate such as a polysulfone resin can be used, and can be used alone or as a composite material. Regarding the structure, it is possible to use these insulating resins alone,
It can be used as a composite material of an organic fiber or an inorganic fiber with a woven or nonwoven fabric, a composite material of an organic powder or an inorganic powder, or a material combining these.

The material or structure of the insulating sheet is preferably selected appropriately in consideration of drilling workability. For example, in the case of drilling by laser processing, a structure having no woven fabric such as a resin or cloth having a high glass transition temperature is used. Are preferred. These insulating sheets can be used as uncured, semi-cured or cured, and in producing a multilayer printed circuit board, these substrates may be the same if necessary, or may be different. May be. Furthermore, selecting a material having a high glass transition temperature in order to suppress the flow of resin during pressurization is also an effective measure for reducing the resistance of the cured conductive paste.

The adhesive sheet may or may not have an adhesive layer formed on both sides of the insulating sheet, but a base material which can sufficiently obtain the adhesive strength with the insulating sheet after laminating copper foil on both sides is selected. Is preferred. The thickness of the insulating sheet can be freely selected, but is generally 10 μm or more and 300 μm or more.
μm or less is appropriate. The material of the peelable film used in the present invention can be used without limitation as long as it is generally used, for example, a polyester-based resin,
Polyethylene resin type, vinyl chloride resin type, polyimide resin type, polypropylene resin type, polyphenylene oxide resin type, cellulose resin type, etc., can be used alone or as a composite material. May be formed.

An adhesive layer may be formed on the surface of the peelable film to be attached to the substrate,
A plasma treatment, a corona treatment, a surface treatment for releasing or bonding with a coupling agent or the like may be performed. In any case, it is preferable to select the material of the film and the surface state of the surface to be bonded to the insulating sheet in consideration of the above-described material of the insulating sheet and the peelability of the film. The thickness of the peelable film used in the present invention is not particularly limited, but is preferably not more than the thickness of the insulating sheet, and is preferably 5 μm or more and 200 μm or less. The thickness of the film is closely related to the height of the protrusion of the semi-cured conductive paste that protrudes and remains in the through-hole portions on both sides of the insulating sheet after peeling, and thus the conductive powder of the conductive paste cured product after hot pressing. Since the thickness of the insulating sheet greatly affects the conductivity, that is, the conductivity, it is preferable to select an appropriate thickness in consideration of the thickness and compressibility of the insulating sheet and the ratio of the conductive powder / organic binder in the conductive paste. For example, when using a base material that does not compress the insulating sheet at all and using a conductive paste having a conductive powder / organic binder ratio of 7/3, the compression ratio of the semi-cured paste volume is 20 to
It is desirable to select the thickness of the film to be 50%.

The method for laminating the insulating sheet and the peelable film in the present invention is not limited, but a general press machine such as a press machine or a roll press machine such as a laminator can be used. At this time, conditions such as vacuum and heating and pressing can be appropriately selected according to the selected insulating base material and film material. In addition, the step of laminating the films can be performed after the through holes are provided in the film or the insulating sheet, however, a problem such as misalignment occurs. Therefore, a method of providing the through holes after lamination is effective.

The film-laminated insulating sheet used in the present invention is provided with through holes for filling a conductive paste. Regarding this through-hole, it is essential that the opening diameter on the releasable film side is larger than the opening diameter of the insulating sheet. Although there is no limitation on the degree of the size, it is practically preferably 1.05 to 3 times the opening diameter of the insulating sheet, more preferably 1.1 to 2 times. As a method of forming the through-hole, drilling, punching, various laser processing, counterbore processing, etching and the like, and a combination thereof, can be used without limitation as long as it is a commonly used method. is there. In the case of laser processing, it is also possible to appropriately select the material of the film to be laminated and to adjust the opening diameter on the film side by performing a plurality of punching treatments. The diameter of the through-hole is not particularly limited, and can be arbitrarily set as long as it can be performed by the above processing method. The range is 0.01 to
It is about 3 mm, preferably 0.03 to 2 mm, and more preferably 0.05 to 1.0 mm.

The conductive paste used in the present invention may be any one which uses a generally known material such as silver, copper, silver-plated copper, nickel, gold, carbon, etc. as a conductive powder. As the conductive powder, one kind or a mixture of two or more kinds, which is kneaded with a resin binder or the like, can be used. These conductive powders can be used in the form of a sphere, a polyhedron, a scale, a flake, or a mixture thereof. Regardless of the shape, a known method of mechanically processing powder can be used. Further, the conductive powder can be used as long as the particle size is substantially in the range of industrial use.
The preferred range is 0.1 to 0.1 as the average particle size.
It is 30 μm, more preferably 0.5 to 15 μm.

Suitable conductive powders include silver, copper, silver-plated copper, copper alloy powder, and the like. When silver powder is used, it has high oxidation resistance, and thus ensures reliable electrical connection and high reliability. Although it is rich, it causes migration problems. Further, when copper is used, problems such as a decrease in electrical connection and a decrease in reliability due to oxidation cannot be denied. The most suitable conductive powder in consideration of these factors is disclosed in JP-A-6-260015, which has already been disclosed by the present applicant.
And copper alloy powder prepared by an inert gas atomizing method described in Japanese Patent Application Laid-Open Publication No. H10-146, in which silver is segregated on the surface of particles at a higher concentration than the average silver concentration. The copper alloy powder has the general formula Agx
Cuy (however, 0.001 ≦ x ≦ 0.4, 0.6 ≦ y
≦ 0.999, x + y = 1 (atomic ratio)) and is a copper alloy powder having a region where the silver concentration on the particle surface is higher than the average silver concentration of the particle.

At this time, the silver amount x of the copper alloy powder is 0.00
If it is less than 1, sufficient oxidation resistance cannot be obtained, and if it exceeds 0.4, good migration resistance cannot be obtained and the cost of the powder increases. The preferred range of the amount x of silver is 0.005 ≦ x ≦ 0.3, and more preferably 0.02 ≦ x0.25. The copper alloy powder has a silver concentration on the surface of the powder higher than the average silver concentration, and the silver concentration on the surface is 1.4 times or more, more preferably 2.1 times or more of the average silver concentration. Is desirable. The silver concentration on the surface and near the surface of the copper alloy powder was determined as a surface silver concentration at a depth of about 50 ° from the surface using an X-ray photoelectron spectrometer ESCALAB200-X manufactured by VG, UK. . The silver concentration at this time was Ag3d5 /
2 (Kα line of Al) and the peak of Cu3p (Kα line of Mg). The average silver concentration was determined by dissolving a sample in concentrated nitric acid, using a high frequency inductively coupled plasma emission spectrometer (JY, manufactured by Seiko Denshi Kogyo KK).
38P-P2).

As the conductive paste in the present invention, a resin binder known in the art as a thermosetting resin can be used. For example, phenol resin, epoxy resin, melamine resin, urea resin, xylene resin, alkyd resin, unsaturated polyester resin, acrylic resin, polyimide resin, furan resin, urethane resin and the like, preferably phenol resin, epoxy resin, melamine Resin and xylene resin, more preferably phenol resin and epoxy resin. In some cases, it is also possible to use a thermoplastic resin together with the thermosetting resin. At this time, characteristics such as printability and adhesion can be improved by combining the resin binder. Among the above resin binders, one kind or a combination of two or more kinds is possible, and in consideration of the viscosity and the structural viscosity index of the conductive paste, the combination is appropriately possible according to the material of the insulating sheet and the like. is there.

Further, the conductive paste of the present invention includes:
It is preferable to use a diluent such as an organic solvent for the purpose of adjusting the flow characteristics and / or improving the volume fraction of the conductive powder in the via hole after hot pressing. in this case,
Since the organic solvent contained in the paste is volatilized during the process of heating and semi-curing the filled paste, there is no void in the via hole when copper foil is bonded and heated and pressed after the film is peeled off, and the organics in the paste are removed. Since the components are reduced, the compactness of the compressed conductive powder is improved, and the effect of improving the conductivity is advantageously obtained.
As the diluent, any known and commonly used diluent may be used. An appropriate amount of addition is 5% by weight or less.

It is essential that the conductive paste in the present invention is semi-cured while being filled in the film-laminated insulating sheet. The term “semi-cured” as used herein means that, in an indenter indentation test using a dynamic ultra-micro hardness tester DUH-W201S manufactured by Shimadzu Corporation, the amount of paste displacement at a test force of 4 mN is within a range of 2 to 7 μm. . When the paste is uncured, when the film on both sides is peeled, the paste is transferred to the release film side and moves, or it is peeled off with the paste clogged in the through hole on the film side, so the insulating sheet The swelling of the paste at the through-hole portions on both sides becomes uneven, and when pasted with copper foil and pressed, fluid paste flows between the copper foil and the insulating layer and bleeds, resulting in poor reliability. This leads to a decrease in conductivity.

Therefore, the filled paste needs to have a certain degree of hardness with suppressed fluidity. Displacement is 2μ
m or less, when the copper foil is laminated and hot-pressed, the conductive paste flows and penetrates between the copper foil and the insulating sheet, and a compressed effect is not obtained, resulting in a cured product having low conductivity. Become. In addition, the displacement amount is 7
If it exceeds μm, the fluidity of the paste is almost lost, and the compactness of the conductive powder in the cured product is extremely reduced, resulting in low conductivity. The preferred range is 3 μm or more and 6 μm or less, and more preferably 4 μm or more and 5 μm or less.
m or less.

As a method of semi-curing, any method may be used, but a curing method by heating is generally used. In this case, known methods such as a box type hot blast stove, a continuous hot blast stove, a muffle type heating furnace, a near-infrared furnace, a far-infrared furnace, and a vacuum heating press can be used. The atmosphere at this time is preferably an atmosphere having a low or no oxygen concentration, an inert gas atmosphere, or a reducing atmosphere, but may be air. A suitable semi-curing temperature depends on the resin binder and curing agent used, but is generally in the range of 40 to 130 ° C.

As a method for filling the conductive paste into the through holes in the present invention, there are a screen printing method, a bar coating method, a dispenser method and the like, and a screen printing method is generally used. In this case, printing / filling is possible through a mesh screen plate or metal mask plate, etc. In addition, since the peelable film serves as a mask while preventing contamination, it is printed directly with a squeegee without using a screen plate. It is also possible. When a screen plate is used, it is desirable to appropriately select the pattern diameter of the screen plate according to the opening diameter of the through hole to be filled. Eliminate bleeding of the through-hole portion of the film surface of the conductive paste filled by each of the above-mentioned methods, and make the height of the semi-cured conductive paste projecting to the through-hole portions of both surfaces of the insulating sheet after peeling the film uniform. For the purpose, it is also possible to wipe off excess paste from above the film using a buff roll or the like after filling, if necessary.

Next, the present invention will be described in detail based on examples. (1) Preparation of conductive powder 30.0 kg of copper particles (purity of 99% by weight or more) and 7.5 kg of silver particles (purity of 99% by weight or more) are put into a graphite crucible, melted at 1650 ° C. by a high frequency induction heating device, and heated. did. The atmosphere was performed in nitrogen of 99% by volume or more. Next, after introducing the molten metal from the tip of the crucible into a spray tank in a helium gas atmosphere, a helium gas (purity of 99% by volume or more, pressure of 35 kg / cm ² G) is supplied from a gas nozzle provided near the tip of the crucible. Was spouted and atomized to produce a copper alloy powder. The average ratio of silver concentration to the surface of the obtained powder was 2.7.

Next, the copper alloy powder was used to prepare a conductive paste by removing as much as possible a powder having a size of 12 μm or more using an airflow classifier. (2) Preparation of conductive paste To 100 parts by weight of the copper alloy powder prepared in (1), 1.4 parts by weight of a novolak type phenol resin, 2.5 parts by weight of neopentyl glycol diglycidyl ether, and a latent curing agent (HX -3741, 0.4 parts by weight of Asahi Epoxy Co., Ltd. and 1.9 parts by weight of benzyl alcohol were added, and the mixture was stirred with a defoaming kneader for 15 minutes to obtain a conductive paste. (3) Method for Producing Film-Laminated Insulating Sheet with Paste-Filled Through-holes FIG. 1 shows a method for producing the film-laminated insulating sheet with paste-filled through-holes in the present invention. A peelable film 2 is laminated on an insulating sheet 1 (FIG. 1a) made of an insulating resin by a laminator or the like (FIG. 1b).
The through holes 3 are provided at predetermined positions and sizes by laser processing, drill processing, or the like (FIG. 1C). Fill the through-holes with conductive paste 4 using a screen printer or dispenser, remove excess conductive paste using a baffle or the like as necessary, and then semi-cure the filled paste using an oven or reflow oven. State (Fig. 1
d). At this time, when a thin base material is used, it is desirable to perform a preliminary press and a semi-curing treatment simultaneously using a hot press. (4) Method for Manufacturing Double-Sided Printed Board FIG. 2 shows a method for manufacturing a double-sided printed board using the film-laminated insulating sheet with paste-filled through holes according to the present invention. The peelable film on both sides of the film-laminated insulating sheet with the paste-filled through hole manufactured in (3) is peeled off by using various delaminators (FIG. 2).
a). At this time, taking into account the adhesion between the insulating base material and the film,
It is an effective measure to appropriately set the peeling speed, angle, temperature and the like. The film is peeled off, the semi-cured conductive paste protrudes on both sides of the through-holes, and the copper foil 5 is laid on both sides of the remaining insulating sheet (FIG. 2b) using a vacuum heat press or the like to form an insulating base material or the like. If present, the adhesive layer formed on both sides of the insulating base material and the semi-cured conductive paste are cured by heating and brought into close contact with the copper foil (FIG. 2c). Finally, a copper foil circuit pattern 6 is formed according to a standard method of pattern etching of a printed wiring board to manufacture a double-sided printed board (FIG. 2).
d). (5) Method for Manufacturing Multilayer Printed Circuit Board FIG. 3 shows a method for manufacturing a multilayer printed circuit board according to the present invention. A sheet in which semi-cured conductive paste protrudes and remains on the through-holes on both sides of the insulating sheet shown in FIG. 2A and the double-sided printed circuit board manufactured in (4) are alternately combined (FIG. 3A), and a vacuum press machine Then, a multilayer printed circuit board (FIG. 3B) is manufactured by lamination.

[0029]

Example 1 A 9 μm thick sheet was laminated on a 24 μm thick polysulfone cyanoester sheet by a vacuum press. Next, when using a laser beam machine, 576 through-holes per sheet were punched at predetermined positions from both sides of the laminated sheet a plurality of times. The opening diameter of the center sheet was 30 μm, and the opening of the outer sheet was opened. 38μ caliber
m.

Next, a conductive paste was filled in the through-holes using a screen printer through a metal mask.
Heating was performed at 80 ° C. for 60 minutes while applying a pressure of 15 kg / cm ² using a vacuum heat press machine, so that the filled conductive paste was semi-cured. The displacement of the semi-cured conductive paste in the indentation test was 4 μm. Next, the laminated films on both sides were peeled off, but no falling off of the semi-cured paste was observed at all. Lay copper foil on both sides,
Heating was performed at 230 ° C. for 60 minutes while applying a pressure of 35 kg / cm ² using a vacuum heat press machine to obtain a double-sided copper-clad substrate. Pattern etching was performed using a dry film resist to prepare a via hole test sample. As a result of observing the cross section of the via hole, no bleeding of the conductive paste was observed in the gap between the copper foil and the insulating base material. The volume resistivity per via hole is 0.7 × 10 −5 Ω ·
cm and good.

[0031]

Example 2 A polyester film having a thickness of 12 μm was laminated on a polyimide sheet having an adhesive layer having a thickness of 40 μm using a vacuum laminator. When 576 through holes were formed at predetermined positions using a laser beam machine, the opening diameter of the polyimide sheet was 48 μm and the opening diameter of the polyester film was 52 μm. This through-hole is filled with a conductive paste using a screen printing machine through a metal mask, and heated in the air at 80 ° C. for 50 minutes using a batch oven, and the filled conductive paste is filled with the conductive paste. Semi-cured. The indentation displacement of the semi-cured conductive paste was 5 μm.

When the laminated films on both sides were peeled off, the conductive paste did not fall off at all. Next, the copper foil was layered on both sides, and 30 kg
Heating was performed at 240 ° C. for 40 minutes while pressurizing at / cm ² , to prepare a double-sided copper-clad substrate. Pattern etching was performed using a dry film resist to prepare a via hole test sample. As a result of observing the cross section of the via hole, no bleeding of the conductive paste was observed in the gap between the copper foil and the insulating base material. The volume resistivity per via hole was as good as 0.5 × 10 −5 Ω · cm.

[0033]

Comparative Example 1 When the same laminated sheet as used in Example 1 was provided with through holes by changing the laser processing conditions, the opening diameter of both the center sheet and the outer sheet was 42 μm. Next, a conductive paste was filled in the through holes using a screen printer through a metal mask. While applying a pressure of 15 kg / cm ² using a vacuum heat press, 80
Heating was performed at 60 ° C. for 60 minutes to semi-harden the filled conductive paste. The indentation displacement of the semi-cured conductive paste was 4 μm.

Next, when the laminated films on both sides were peeled off, the semi-cured paste was found to fall off in 10 of the 576 holes. Next, copper foil was laminated on both sides, and the copper foil was pressed at 35 kg / cm ² by a vacuum hot press machine.
Heating was performed at 30 ° C. for 60 minutes to obtain a double-sided copper-clad substrate.
Pattern etching was performed using a dry film resist to prepare a via hole test sample. As a result of observing the cross section of the via hole, no bleeding of the conductive paste was observed in the gap between the copper foil and the insulating base material. With respect to the resistance value, the via hole in which the paste was observed to drop was completely open.

[0035]

Comparative Example 2 Using the same laminated sheet as that laminated and laser-processed in Example 1, a conductive paste was filled into the through holes, and the mixture was heated at 60 ° C. for 30 minutes in the air using a batch type oven. Heated. At this time, the indentation displacement of the conductive paste was 15 μm. When the laminated films on both sides were peeled off, the conductive paste did not fall off at all.

Next, a copper foil was laminated on both sides, and pressed at 235 ° C. under 40 kg / cm ² by a vacuum hot press machine.
Heating was performed for a minute to produce a double-sided copper-clad substrate. Pattern etching was performed using a dry film resist to prepare a via hole test sample. As a result of observing the cross section of the via hole, noticeable bleeding of the conductive paste was observed in the gap between the copper foil and the insulating base material, and the volume resistivity per via hole was as high as 2.5 × 10 −4 Ω · cm. .

[0037]

Comparative Example 3 A conductive paste was filled in through-holes using the same laminated sheet obtained by laminating and laser processing in Example 1, and the mixture was heated at 150 ° C. for 20 minutes in the air using a batch type oven. Upon heating, the indentation displacement of the conductive paste was 0.8 μm. When the laminated films on both sides were peeled off, the conductive paste did not fall off at all.

Next, a copper foil is laminated on both sides, and is pressed at 230 ° C. at 60 ° C. while applying a pressure of 30 kg / cm ² by a vacuum hot press machine.
Heating was performed for a minute to produce a double-sided copper-clad substrate. Pattern etching was performed using a dry film resist to prepare a via hole test sample. As a result of observing the cross section of the via hole, no bleeding of the conductive paste was observed in the gap between the copper foil and the insulating base material, but the volume resistivity per via hole was as high as 3.5 × 10 −4 Ω · cm. Was.

[0039]

As described above, as shown in the embodiments, a through-hole is formed through a multilayer sheet using a multilayer sheet in which a releasable film is laminated on both sides of an insulating sheet. Characterized in that the opening diameter of the releasable film is larger than the opening diameter of the insulating sheet, and the film is semi-cured after filling a conductive paste made of a conductive powder and a thermosetting resin in the through holes. The laminated insulating sheet prevents the paste from falling off or being broken during the film peeling or during the process, and the semi-cured conductive paste easily projects and remains in the via hole portions on both sides of the insulating sheet after the film is peeled off. The double-sided printed circuit board manufactured by laminating the copper foil and heat pressing the conductive powder into the via hole without flowing and bleeding the paste between the copper foil and the insulating sheet Compressed densified, it is possible to improve the conductivity.

That is, according to the present invention, interlayer connection having high conductivity can be achieved without being restricted by the material and structure of the insulating sheet, and the production efficiency of a double-sided printed board or a multilayer printed board having an extremely small diameter via hole can be improved. It is possible to manufacture a high-density printed circuit board with high versatility over a wide range.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a cross-sectional structure illustrating a method for manufacturing a multilayer sheet according to the present invention.

FIG. 2 is a conceptual diagram of a cross-sectional structure illustrating a method of manufacturing a via-hole-filled double-sided printed circuit board using a multilayer sheet according to the present invention.

FIG. 3 is a conceptual diagram of a cross-sectional structure illustrating a method of manufacturing a via-hole-filled multilayer printed board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating sheet 2 Peelable film 3 Through hole 4 Semi-cured conductive paste 5 Copper foil 6 Copper foil circuit pattern layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E317 AA24 BB01 BB02 BB03 BB12 BB13 BB14 BB15 5E346 AA43 CC08 CC09 CC10 CC32 CC37 CC38 CC39 DD12 EE02 EE05 FF18 GG15 GG22 HH07 HH33

Claims (5)

[Claims] 1. A multilayer sheet in which a peelable film is laminated on both sides of an insulating sheet made of an insulating resin, wherein the multilayer sheet has a through hole, and the through hole is formed of the peelable film. A multilayer sheet having an opening diameter larger than the opening diameter of the insulating sheet and filled with a conductive paste having a conductive powder and a thermosetting resin in a semi-cured state. 2. A via-hole-filled double-sided board, wherein the peelable film of the multilayer sheet according to claim 1 is removed, copper foils are laminated on both sides, and hot-pressed. 3. A via-hole-filled double-sided printed circuit board, wherein the copper foil of the via-hole-filled double-sided board according to claim 2 is patterned and electrically connected to the conductive paste. 4. A via-hole-filled multilayer printed circuit board, wherein a plurality of via-hole-filled double-sided printed circuit boards according to claim 3 are stacked and electrically connected between multiple layers. 5. A multi-layer sheet in which a releasable film is laminated on both sides of an insulating sheet made of an insulating resin is provided with a through hole in which the opening diameter of the releasable film is larger than the opening diameter of the insulating sheet. The through hole is filled with a conductive paste having a conductive powder and a thermosetting resin in a semi-cured state, the peelable film is removed, and a copper foil is laminated on both sides by a hot press, and the copper A method for producing a via-hole-filled double-sided printed circuit board, wherein a foil is patterned and electrically connected to the conductive paste.