JPH10190159A - Printing substrate, circuit board-connecting material using the substrate, and manufacture of multilayered circuit board using the connection material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing substrate which can suppress the viscosity rise of a paste-like composition which is printed on a mask film and fills up via holes at continuous printing time by improving the scrapability of the remaining composition so as to improve the number of times for printing of the composition, a circuit board- connecting material using the printing base material, and a multilayered circuit board manufacturing method using the connecting material. SOLUTION: A printing substrate is constituted in a multilayered structure in which at least one of the outermost layers works as a mask film, and the mask film is composed of a synthetic resin film and a mold release agent so that the external surface of the film can have a mold releasability. In addition, the surface roughness of the mask film is adjusted to <=100nm, or the modulus of elasticity of the film is adjusted to >=300kgf/mm<2> . A multilayered circuit board is manufactured by sandwiching a circuit board-connecting agent 303 which is obtained by removing the mask film after via holes provided in the printing printing substrate is filled up with a conductive composition between two both-sided circuit boards 309, and heating and pressurizing the laminated body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed substrate for printing or filling a paste-like composition on a circuit board (printed wiring board) having through holes, ie, via holes (hereinafter referred to as "vias"). About. Further, the present invention relates to a circuit board connecting material using the printed base material and a method for manufacturing a multilayer circuit board using the same.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become higher in performance and smaller in size, circuit boards have been required to have more layers and higher densities. An inner via-hole connection method is known as a connection method between layers of a substrate that enables electrical connection between electronic components such as ICs to be performed in the shortest distance, and thereby, it is possible to increase the density of a multilayer substrate.

A multilayer substrate using an inner via-hole connection method is a method in which a circuit board connection material such as a prepreg in which a paste-like conductive composition is filled into vias is formed of a pair of copper foils for pattern formation or a pattern formed in advance. It is manufactured by holding and pressing under a core material.

As the paste-like conductive composition, a paste in which a conductive filler such as copper powder is dispersed in a synthetic resin binder such as an epoxy resin is used. Vias provided in the circuit board connecting member are filled with the paste-like conductive composition by a method such as printing. In this printing step, the conductive composition is directly printed on a circuit board connecting member provided with a film such as PET on the surface, and is filled in a via. At this time, the film plays a role of a disposable mask.

After filling by printing, the composition remaining on the mask film of the printing substrate is scraped off by a squeegee and used for printing and filling the next printing substrate. At this time, if a normal PET film is used as the mask film, the composition containing a large amount of the resin component is left unscrewed.

In the printing process, the viscosity of the composition is an important parameter and needs to be controlled to an optimum value. However, even if the viscosity of the composition is initially controlled to an appropriate value, if a scraping residue of the composition with a high resin component occurs on the mask film, the viscosity of the composition increases each time the printing is repeated, Eventually you will not be able to print.

[0007]

As described above, when the composition is left unscrewed on the mask film, the viscosity of the composition immediately increases, so that it is necessary to frequently replace the composition with a new composition. is there. This contributes to an increase in manufacturing cost. Further, the composition whose viscosity has been increased to such an extent that it cannot be printed is discarded. However, it is not preferable from the viewpoint of the global environment that the discarded amount increases.

For the reasons described above, the scraping property of the composition on the mask film is improved to suppress the increase in the viscosity of the composition during continuous printing, that is, the number of times the paste composition can be printed is improved. It is desired.

Accordingly, an object of the present invention is to provide a printing substrate capable of improving the number of printable times of the paste composition. It is also an object of the present invention to provide a circuit board connecting material using the printed base material and a method for manufacturing a multilayer circuit board using the same.

[0010]

According to a first aspect of the present invention, there is provided a printing base material having a multilayer structure used in a step of filling or printing a paste-like composition, wherein the printing base material has an outermost layer. At least one of them plays a role of a mask film, and the outside of the mask film has a releasing property.

Since the outer surface of the mask film has a releasability, the paste-like composition hardly adheres and is easily scraped off by a squeegee. Therefore, the resin component of the paste composition does not remain on the printing substrate, and the number of times the paste composition can be used repeatedly (the number of times that the paste composition can be printed) is improved.

In order to make the outer surface of the mask film have releasability, for example, the mask film may be composed of a synthetic resin film and a release agent applied thereon. As the release agent applied on the synthetic resin mask film, a generally used silicon-based or fluorine-based release agent can be used.

A second configuration of the printing substrate according to the present invention is a multi-layered printing substrate used in the step of filling or printing the paste-like composition, wherein at least one of the outermost layers is used. Plays the role of a mask film, and the outer surface roughness of the mask film is 100 nm or less. By using a film having a surface roughness of 100 nm or less as a mask film, a gap between the squeegee and the surface is reduced when the paste-like composition is scraped off, and almost no scraping residue of the paste composition is left.

Further, a third configuration of the printing base material according to the present invention is a multi-layered printing base material used in a step of filling or printing the paste-like composition, wherein at least one of the outermost layers is used. Plays a role of a mask film, and the elastic modulus of the mask film is 300 kgf / mm ² or more. The elastic modulus is 300 kgf / mm ²
By using the above film as a mask film, the surface of the mask film becomes relatively flat even if the printing substrate has a somewhat rough surface, and the paste composition can be scraped off with a squeegee.

In each of the above structures, the mask film is preferably made of a synthetic resin film. For example, a polyethylene terephthalate film or a polypropylene film can be used.

Further, the circuit board connecting material according to the present invention is such that a through-hole is provided at a predetermined position of the above-mentioned printing substrate, and the through-hole is filled with a conductive composition. That is, the printing base material itself is used as a circuit board connecting material (insulating layer) constituting the multilayer board. Thus, the multilayer board can be efficiently manufactured while obtaining good electrical connection between the conductor layers of the multilayer board.

The conductive composition has an average particle size of 0.5 to 0.5.
20 μm of at least one metal powder 80 selected from gold, silver, nickel, copper, palladium and alloys thereof
To 92% by weight and at least one selected from an epoxy resin, a phenol resin, a polyimide resin and an acrylic resin.
It preferably contains 4.5 to 20% by weight of one synthetic resin.

One of the methods for manufacturing a multilayer circuit board according to the present invention is a method for manufacturing a multilayer circuit board, comprising the steps of: providing a circuit board having at least two circuit patterns and a circuit board having at least one circuit pattern; The method includes a step of sandwiching the connection material from which the mask film has been removed, and heating and pressing the obtained laminate. Further, another method for manufacturing a multilayer circuit board according to the present invention is a method of manufacturing a multilayer circuit board, wherein the circuit board having at least two layers or more of circuit patterns is overlapped on both sides of the circuit board with the mask film of the circuit board connecting material removed, and further on both sides. After attaching a metal foil, heating and pressing the obtained laminated body, the method includes processing the metal foil to form a circuit pattern. With such a manufacturing method, a multilayer circuit board having high reliability of electrical connection between conductive layers can be efficiently manufactured.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below with reference to some examples. First, the paste composition, prepreg, copper foil, and mask film used in each example will be described.

(A) Paste composition In each of the examples, 87.5% by weight of copper powder, 3.0% by weight of bisphenol F, 7.0% by weight of glycidyl-esterified epoxy resin of dimer acid and 7.0% by weight of amine adduct type curing agent A paste-like conductive composition consisting of 2.5% by weight was used. However, the paste-like composition used for the printing substrate of the present invention is not limited to such a specific paste-like conductive composition, but also includes a paste-like resistor composition, a paste-like insulating composition, and a paste-like heat conductive composition. Various paste compositions can be used depending on the application, such as a volatile composition. Further, the circuit board connecting material of the present invention, the paste-like conductive composition used in the method for manufacturing a multilayer circuit board using the same is not limited to the specific paste-like conductive resin composition as described above, A paste composition containing conductive powder as a filler and using organic or inorganic materials as a binder and having desired electric characteristics can be used.

(B) Prepreg In each of the examples, an aramid (aromatic aramid) epoxy nonwoven fabric sheet was used in which a nonwoven fabric made of “Kevlar” manufactured by DuPont was impregnated with an epoxy resin. The above nonwoven fabric is produced by a wet method using fibers having a fiber strength of 2.2 denier and a fiber length of 6 mm. After paper making, temperature 300
After performing a calendaring process under the conditions of a temperature of 200 ° C. and a pressure of 200 kg / cm ^2, a heating process was performed at 250 ° C. for 10 minutes to obtain a basis weight of 70 g / cm ^2.
A nonwoven fabric having a thickness of m ² and a thickness of 100 μm is obtained. However, the present invention is not limited to such a specific prepreg, a general prepreg such as a glass epoxy prepreg, a synthetic resin sheet such as a polyimide sheet, or a base material such as a ceramic substrate filled with the paste composition or It can be applied to a printing process.

(C) Copper Foil Copper foil was used as the conductor layer of the multilayer circuit board produced in each of the examples. An electrolytic copper foil having a thickness of 9 to 70 μm is generally used, but is not limited to this.

(D) Mask Film In each of the examples, a polyethylene terephthalate (PET) film and a polypropylene film were used as mask films. However, the present invention is not limited to these specific mask films and may be, for example, a general synthetic resin film such as polyimide or polyethylene, or a metal film such as stainless steel. or,
As the release agent applied to the surface of the mask film, a silicon release agent and a fluorine release agent were used. However, in practicing the present invention, not only these specific release agents but also other types of release agents may be applied to the surface of the mask film.
In each of the examples, a combination of a plurality of sub-examples including a comparative example, as shown in Table 1, for example, by a combination of these plural types of mask films and release agents, and a combination of a plurality of levels of surface roughness it can.

Embodiment 1 As a first embodiment of the present invention, as shown in FIG. 1, various mask films 101 as shown in Table 1 are thermally applied on both sides of a prepreg 102 having a length of 240 mm and a width of 240 mm. The printed substrate was produced by bonding by press bonding and opening a via (through hole) 103 having a diameter of 150 μm with a carbon dioxide laser. The conductive composition has a viscosity of 200
100 g of Pa · s were charged. The printing substrate was placed on a table of a printing machine, and the conductive composition was printed on a mask film and filled into vias. In FIG. 1, reference numeral 104 denotes a conductive composition filled in vias.

In order to evaluate the number of times of repetitive printing, the conductive composition on the mask film was left unscrewed,
The filled state of the conductive composition into the via was checked, and the viscosity before printing and the viscosity after printing were measured using an E-type viscometer.
It measured at 0.5 degreeC and 0.5 degreeC. The aforementioned mask film,
Table 1 shows the results of the evaluation of a plurality of examples and comparative examples based on the combination of the surface roughness and the release agent.

[0026]

[Table 1]

Table 1 shows data on the 300th printing substrate when the conductive composition was repeatedly printed and filled on 300 printing substrates. However, in Comparative Example 1-1 and Comparative Example 1-3, the viscosity of the conductive composition became considerably high after printing 50 sheets (Comparative Example 1-1 had a viscosity of 300).
0 Pa · s or more), a large amount of unscraped composition was generated, and the vias could not be filled.

Examples 1-1 to 1-4 are four examples by combining two types of mask films and two types of release agents. The films have a surface roughness Ra = 200 μm and an elastic modulus E = 100 kgf. / Cm ² . In all cases, the increase in viscosity was small even after printing 300 sheets, and both the scraping property of the composition and the filling property into the via were good.

Comparative Examples 1-1 to 1-4 and Example 1
In Nos. 5 to 1-13, one of the surface roughness Ra and the elastic modulus E of the mask film was changed without applying any release agent. The value not changed is Ra = 200.
μm or E = 100 kgf / cm ² . Reduce surface roughness Ra of mask film (100 μm or less)
Alternatively, the elastic modulus E of the mask film is increased (300 k
gf / cm ² or more), the increase in viscosity was relatively small even after printing 300 sheets, and both the scraping property of the composition and the filling property of the via were improved.

(Embodiment 2) As a second embodiment of the present invention,
Then, as shown in FIG. 2, the printing base material prepared in Example 1 was used.
Using the circuit board connecting material 203 filled with the conductive composition
A double-sided circuit board was manufactured. Time when the mask film is peeled off
The circuit board connecting member 203 is made of two copper foils 205 having a thickness of 35 μm.
(FIG. 2 (a)), temperature 200 ° C., pressure 5 in vacuum
0kg / cm ^TwoUnder the conditions described above, heating and pressurization were performed for about 1 hour. this
As a result, the circuit board connection material hardens and the copper foil
It was bonded to the plate connecting material (FIG. 2 (b)).

Next, a circuit pattern 206 was formed on the copper foil on both sides by a known photolithography method.
(C)). Specifically, a dry film is stuck on both sides of the laminate of FIG. 2B with a hot roll, and the pattern is exposed to ultraviolet light to cure only the portion where the copper foil remains. Next, the uncured portion is removed by a development process, and etching is performed in a copper chloride solution. Finally, the excess dry film is peeled off to form the circuit pattern 206.

The double-sided circuit board thus manufactured was evaluated by an electrical continuity test and a reliability test. The electrical continuity was determined by measuring the connection resistance per via by a four-terminal method. As a reliability test, a solder reflow test and an oil dip test were performed, and after each test, the sum of the connection resistance of 500 vias and the resistance of the circuit pattern was measured by a four-terminal method. Then, the value obtained by subtracting the initial resistance from the measured value after the test, that is, the amount of change in the resistance value of 500 vias was obtained and evaluated.

In the solder reflow test, the sample double-sided circuit board was placed in a solder reflow furnace heated to a temperature of 260 ° C.
The cycle of charging for 0 seconds and then leaving in the atmosphere for 10 minutes was repeated 10 times. 5 at this time
It was determined to be good if the amount of change in the resistance value of the 00 vias was 250 mΩ or less. This is equivalent to 0 .0 per via.
This corresponds to a change of 5 mΩ or less.

The oil dip test is a temperature cycle in which a double-sided circuit board of a sample is immersed in oil heated to a temperature of 260 ° C. for 10 seconds, and then immersed in oil at a temperature of 20 ° C. for 10 seconds at room temperature. Performed by repeating 200 times. Then, the resistance when immersed in the high-temperature oil and the low-temperature oil was measured, it was checked that no disconnection occurred during 200 temperature cycles, and the resistance change before and after the test was measured. The criterion for determining the quality of the resistance change is the same as that of the solder reflow test. Table 2 shows the evaluation results.

[0035]

[Table 2]

Table 2 shows the 300th printing substrate of each of Examples and Comparative Examples shown in Table 1 (Example 1) (for Comparative Example 2-1 and Comparative Example 2-3, the 50th printing substrate). 2 shows data on a double-sided circuit board manufactured using a printed substrate. As can be seen from this table, Comparative Examples 2-1 to 2-4
Each substrate has a relatively large resistance value per via, and has a resistance value of 5% after a solder reflow test or an oil dip test.
The amount of change in the resistance value of the 00 vias exceeds 250 mΩ. Some of them were broken after the oil dip test. On the other hand, the substrates of Examples 2-1 to 2-13 each have a small resistance value per via (about 0.37 mΩ to 0.48 mΩ), and 500 pieces after the solder reflow test or the oil dip test. The change amount of the resistance value of the via per minute was less than 250 mΩ, indicating a good result.

(Example 3) Next, as a third example of the present invention, a multilayer substrate was manufactured using a circuit board connecting material in which the conductive composition was filled into the printing base material manufactured in Example 1. In this embodiment, as shown in FIG.
Was sandwiched between two double-sided circuit boards 309 to produce a multilayer board. A glass epoxy substrate was used as the double-sided circuit board.

The glass epoxy double-sided board was manufactured as follows. First, a prepreg (about 100 μm thick) in which a glass woven fabric is impregnated with a thermosetting resin equivalent to FR-4.
Were superposed on each other, and a copper foil having a thickness of 35 μm and subjected to a roughening treatment on both surfaces was superposed on both surfaces thereof. The laminated body is heated at a temperature of 17 in vacuum.
Heating and pressurizing was performed for about 1 hour at 0 ° C. and a pressure of 40 kg / cm ² to cure the substrate and bond the copper foil. A through-hole (via) 307 having a diameter of 0.6 mm was drilled at a predetermined position on the substrate thus manufactured by a drilling machine, and a copper plating film was formed on the inner wall 308 of the via and the surface conductor layer by copper plating. Thereafter, a circuit pattern 306 was formed on the surface conductor layer by photolithography.

The circuit board connecting member 303 from which the mask film has been peeled off is positioned and sandwiched between the two glass epoxy double-sided substrates 309 produced as described above, and this laminate is heated under the same conditions as described above. Pressurized. At this time, a land is provided in a portion of the double-sided board to be electrically connected to another layer of the circuit pattern, and the conductive composition 304 of the circuit board connecting member 303 comes into contact with the land. Then, via portion 3 formed by drilling of double-sided substrate 309
07 and the position of the conductive composition 304 of the circuit board connecting member are not overlapped.

As described above, a multilayer circuit board having four conductive circuit layers was manufactured. The via portion 307 of the double-sided board was completely covered by the epoxy resin of the circuit board connecting material. Table 3 shows the results of the electrical continuity test and the reliability test of this multilayer circuit board.

[0041]

[Table 3]

Table 3 shows the 299th printing substrate of each of Examples and Comparative Examples shown in Table 1 (Example 1) (for Comparative Example 3-1 and Comparative Example 3-2, the 49th printing substrate). 2 shows data on a multilayer circuit board manufactured using a printed base material. As can be seen from this table, Comparative Examples 3-1 to 3-4
Each substrate has a relatively large resistance value per via, and has a resistance value of 5% after a solder reflow test or an oil dip test.
Although the change in the resistance value of the 00 vias exceeded 250 mΩ, the substrates of Examples 3-1 to 3-13 all had a small resistance value per via (about 0.39 mΩ to
0.50 mΩ), and the change in the resistance value of the 500 vias after the solder reflow test or the oil dip test is also 250.
less than mΩ, indicating good results.

(Example 4) Next, as a fourth example of the present invention, a circuit board connecting material in which the conductive material was filled into the printed base material prepared in Example 1 was used. Multilayer substrates were made by different methods. In this embodiment, as shown in FIG. 4, the four-layer circuit board 410 is
3, and a copper foil 405 was further laminated on both sides to produce a multilayer substrate.

The four-layer circuit board 410 was manufactured using a glass epoxy substrate as follows. First, a prepreg (thickness: about 100 μm) in which a thermosetting resin is impregnated in a glass woven fabric
Are laminated, and a copper foil having a thickness of 35 μm, which has been roughened on one side, is further laminated on both sides, and is heated and pressed in a vacuum at a temperature of 170 ° C. and a pressure of 40 kg / cm ² for about 1 hour to cure the substrate. And copper foil were bonded. After bonding the copper foil, a circuit pattern was formed by photolithography. Specifically, a dry film is stuck on both sides using a laminator, and after pattern exposure, development, etching, and dry film peeling are performed.

Next, the copper foil surface of the substrate on which the circuit pattern was formed was subjected to blackening treatment, and two prepregs were further laminated on both surfaces thereof, and a single-side roughened copper foil was laminated on both surfaces with the roughened surface inside. The heat and pressure treatment was performed again. A via 407 having a diameter of 0.6 mm was formed at a desired position on the substrate by a drilling machine, and a copper plating film was formed on the inner wall 408 of the via and the outer layer surface by copper plating. Thereafter, a circuit pattern was formed on the outer layer surface by photolithography.

Using the glass epoxy four-layer substrate 410 manufactured as described above as an intermediate layer, the circuit board connecting material 403 from which the mask film has been peeled off is aligned and superposed on both surfaces thereof. The copper foil 405 was overlaid and heated and pressed under the same conditions as above. A circuit pattern was formed on the surface copper foil of the multilayer substrate thus manufactured by using the same photolithography method as described above. At this time, the four-layer substrate 410 and the surface copper foil 405 are connected by the conductive composition 404, and a land 412 for electrical connection is provided at a position of the circuit board connecting member 403 corresponding to the conductive composition 404. Have been. Then, the position of the via portion 407 of the four-layer board 410 and the circuit board connecting material 403
Of the conductive composition 404 is not overlapped.

As described above, a multilayer circuit board having six conductive circuit layers was manufactured. The via portion 407 of the double-sided board is completely closed by the epoxy resin of the circuit board connecting material flowing therein. Table 4 shows the results of the electrical continuity test and the reliability test of this multilayer circuit board.

[0048]

[Table 4]

Table 4 shows the 298-th and 297-th printing substrates (Comparative Examples 3-1 and 3-2 for each of Examples and Comparative Examples shown in Table 1 (Example 1)). The data on the substrates using the 48th and 47th printing substrates) are shown. As can be seen from this table, Comparative Example 4-1
Each of the substrates 4 to 4-4 has a relatively large resistance value per via, and the resistance change amount of the 500 vias after the solder reflow test or the oil dip test is 250.
Although it exceeds mΩ, the substrates of Examples 4-1 to 4-13 all have a small resistance value per via (about 0.
44 mΩ to 0.55 mΩ), and the amount of change in the resistance value of the 500 vias after the solder reflow test or the oil dip test is less than 250 mΩ, indicating a good result.

In this embodiment, a multilayer circuit board having six layers is manufactured. However, by repeating the above-described steps as many times as necessary, a multilayer board having a larger number of layers can be manufactured. In the method for manufacturing a multilayer circuit board according to this embodiment, a completed multilayer circuit board that has been inspected and a circuit board connecting member are laminated, so that a high manufacturing yield can be obtained and an increase in cost can be suppressed. Further, according to the manufacturing method of this embodiment, a multilayer substrate having a large number of stacked layers can be relatively easily manufactured.

It is to be noted that the intermediate layer is not a completed multi-layer substrate but a laminated body before heating and pressurizing, and a circuit board connecting material and a copper foil are laminated on both sides thereof, and then heated and pressurized at once to perform multi-layering. A circuit board may be manufactured. Similarly, when an aramid epoxy double-sided board manufactured by using the circuit board connecting material in Example 2 was used as the intermediate layer instead of the glass epoxy four-layer circuit board, similarly good evaluation results were obtained.

[0052]

As described above, according to the printing substrate of the present invention, the number of times the paste composition to be printed / filled can be used repeatedly is greatly improved. In addition, a highly reliable circuit board connecting material can be manufactured using the printed base material, and a multilayer board can be easily and rationally manufactured using the circuit board connecting material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a printing base material according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a double-sided circuit board according to Embodiment 2 of the present invention.

FIG. 3 is a cross-sectional view illustrating a method for manufacturing a multilayer circuit board according to Embodiment 3 of the present invention.

FIG. 4 is a sectional view showing a method for manufacturing a multilayer circuit board according to Embodiment 4 of the present invention.

[Explanation of symbols]

 Reference Signs List 101 mask film 102 prepreg 103 via 104, 204, 304, 404 conductive composition 203, 303, 403 circuit board connection material 205, 405 copper foil 206 outer layer circuit pattern 306, 406 circuit pattern 307, 407 drilled hole 308, 408 Copper plating through 309 Glass epoxy double-sided board 410 Glass epoxy 4-layer board 412 Land

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoji Ueda 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] 1. A printing substrate having a multilayer structure used in a step of filling or printing a paste-like composition, wherein at least one of an outermost layer plays a role of a mask film, and an outer surface of the mask film. Has a mold release property. 2. The printing substrate according to claim 1, wherein the mask film comprises a synthetic resin film and a release agent applied thereon. 3. The printing substrate according to claim 2, wherein the release agent is a silicon-based release agent. 4. The printing substrate according to claim 2, wherein the release agent is a fluorine-based release agent. 5. A multi-layered printing substrate used in a step of filling or printing a paste-like composition, wherein at least one of an outermost layer plays a role of a mask film, and an outer surface of the mask film. Has a surface roughness of 100 nm
A printing substrate characterized by the following. 6. A printing substrate having a multilayer structure used in a step of filling or printing a paste-like composition, wherein at least one of an outermost layer plays a role of a mask film, and has an elasticity of the mask film. Rate is 300kgf / mm
A printing base material characterized by being ² or more. 7. The printing substrate according to claim 5, wherein the mask film is a synthetic resin film. 8. The printing substrate according to claim 2, wherein the synthetic resin film is a polyethylene terephthalate film or a polypropylene film. 9. A circuit board connecting material, wherein a through-hole is provided in a predetermined position of the printing base material according to claim 1, and the through-hole is filled with a conductive composition. 10. The conductive composition has an average particle size of 0.1.
5 to 20 μm of 80 to 92% by weight of at least one metal powder selected from gold, silver, nickel, copper, palladium and alloys thereof, an epoxy resin, a phenol resin,
10. The circuit board connecting material according to claim 9, comprising 4.5 to 20% by weight of at least one synthetic resin selected from a polyimide resin and an acrylic resin. 11. The circuit board connecting material according to claim 9, wherein a mask film is removed between a circuit board having at least two or more circuit patterns and a circuit board having at least one or more circuit patterns. A method for producing a multilayer circuit board, comprising a step of heating and pressing the obtained laminate while sandwiching the laminated body. 12. A circuit board having at least two layers of circuit patterns, on both sides of which a mask film is removed from the circuit board connecting material according to claim 9, and a metal foil is attached on both outer sides. And a method of manufacturing a multilayer circuit board, comprising a step of heating and pressurizing the obtained laminate, and processing the metal foil to form a circuit pattern.