JPH09331136A - Printed wiring board with conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a printed wiring board which is resources-saving, environment-protecting, and low in cost by a method wherein a photosensitive insulating resin layer where a part which serves as a conduction circuit is removed by development is provided to the surface of an insulating board. SOLUTION: A photosensitive resin layer 2 is formed on the one side or both the sides of an insulating board 1 which serves as a supporting body. Then, a negative film is provided onto the insulating board 1 and irradiated with ultraviolet rays, a recessed part is provided onto the insulating board 1 by development, and conductive paste 3 is filled up into the recessed part for the formation of a one-sided or a double-sided copper-plated laminated board. Furthermore, when a multilayer printed wiring board is formed, a second photosensitive resin layer 4 is formed on the obtained one-sided or double-sided copper-plated board, a recessed part is provided in the copper-plated board by irradiation with light rays and development, and a second conductive paste 5 is filled in the recessed part. By this setup, a multilayer printed wiring board can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a printed wiring board using a photosensitive insulating resin and a conductive paste, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, high-precision personal computers and mobile phones have become widespread, and the functionality and size of printed wiring boards have been increasing. At the same time, however, there is an urgent need for cost reduction. . In addition, environmental measures during the manufacture of printed wiring boards have become an important issue.

Conventional printed wiring boards have generally used a single-sided or double-sided copper-clad laminate to remove unnecessary portions of the copper foil by etching to form a circuit. In this case, a paper base phenolic resin laminate (hereinafter referred to as paper phenol laminate), a glass fiber base epoxy resin laminate (hereinafter referred to as glass epoxy laminate), a polyimide film, or the like is used as the support insulating plate. However, phenol resin moldings, thermoplastic films, and the like are rarely used because it is difficult to laminate a copper foil on the surface.

In the conventional method for manufacturing a printed wiring board, since the copper foil in the unnecessary portion is removed by etching, there are problems in terms of environment and resources. On the other hand, as a manufacturing method for applying a conductor only to a necessary portion, there are an additive method and a conductive paste printing method. The additive method is
This is a circuit in which a plating resist is formed in advance and electroless plating is applied only to the necessary parts, but the number of steps is large and it takes a very long time for electroless plating. Although it is advantageous, it is disadvantageous in terms of cost. On the other hand, the conductive paste printing method is
A resin paste having conductivity is printed only on a necessary portion. A typical method of printing is screen printing, but the problem is that the conductive resistance value becomes large because the thickness of the printed conductive paste is limited, and in the state where it is thick, it becomes fine. When circuits are printed, bridging between circuits is likely to occur and long-term insulation reliability is poor due to migration and other causes.

On the other hand, the conductive paste can be thickened,
Further, as a manufacturing method with high reliability of insulation between circuits, there is a method of forming a recess in advance in a portion where a conductive paste is printed. For example, there is a method of using a phenol resin molded product in which a recess is formed by die molding, a phenol resin molded product in which a recess is formed by cutting with a router, or another insulating substrate, and filling the recess with a conductive paste. . In this case, since the conductive paste is formed thick, the electric resistance value is low (the conductivity is good), and since the circuit is formed in the groove of the recess, the insulation reliability between the circuits is also excellent. However, the phenol resin molded product using the mold is very expensive, and thus it is disadvantageous in terms of cost when a small amount and a large variety of products are used. Also in the cutting method using a router, the thickness of the insulating substrate is limited, and it is difficult to process the concave portion having a small width.

In the conventional manufacturing method, a press is used to form a multilayer structure. However, in order to simplify the process, when multilayering is performed without using a press such as roll lamination, since unevenness due to the circuit exists in the inner layer circuit board, the finished multilayer printed board has poor surface smoothness, To prevent this, it was necessary to use an undercoating agent to eliminate irregularities in advance.

[0007]

However, the conventional method of forming a circuit by removing the copper foil of the copper clad laminate by etching has problems in terms of resources and environment. In addition, the method of forming a conductor only in a necessary portion by the additive method or the conductive paste printing method is disadvantageous in cost in the case of the additive method, and in the case of the conductive paste printing method, the cost and the conduction resistance value are also reduced. , There is a problem in long-term insulation reliability between circuits. Further, since there are irregularities due to the inner layer circuit, it is difficult to form multiple layers without using a press.

The present invention has been made as a result of various studies in order to solve these problems, and an object of the present invention is to achieve a printed wiring board or a multilayer printed wiring which achieves resource saving, environmental protection, and cost reduction. To provide a plate.

[0009]

According to the present invention, a photosensitive insulating resin layer obtained by removing a portion which becomes a conductive circuit by development is provided on one side or both sides of an insulating plate or a printed circuit board, and the portion removed by development is provided. The present invention relates to a printed wiring board characterized by being filled with a conductive paste to form a conductive circuit, or a multilayer printed wiring board characterized by repeating the process a plurality of times, and a manufacturing method thereof.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing a manufacturing process of a multilayer printed wiring board according to the present invention. Although the circuit is formed only on one side of the insulating plate in FIG. 1, the same can be done when the circuit is formed on both sides. It is also possible to use a prefabricated printed circuit board instead of the insulating plate.

First, a photosensitive resin layer (2) is formed on one side or both sides of an insulating plate (1) serving as a support (A, B). The insulating plate (1) may be any as long as it is electrically insulating. Thermosetting resin laminated plates such as glass epoxy laminated plates and paper phenol laminated plates, thermoplastic films such as polyimide films and polyethylene terephthalate films, phenolic resins. There are thermosetting resin molded products such as melamine resin, and glass, ceramics, etc. can also be used. The photosensitive resin layer (2) can form recesses by light irradiation and development, and serves as an insulating layer. For example, epoxy (meth) acrylate used as a heat-resistant solder resist, carboxyl group-containing phenol novolac. Examples thereof include those containing epoxy (meth) acrylate as a main component and photosensitive polyimide resins. Since this insulating resin layer is preferably made equal in thickness to the conductive paste filled in the portion removed by development, it is preferably 100 μm or more, and 150 μm or more in order to reduce electric resistance and improve conductivity. It is more preferable if it exists. Examples of the method for forming this insulating resin layer on the insulating plate include a method in which an ink-like material is applied with a curtain coater one or more times, or a dry film-like one is laminated once or twice or more.

Next, a negative film is placed on the insulating plate,
After irradiation with ultraviolet rays, a recess is formed by development (C),
Filling the formed recesses with a conductive paste (3)
(D). The conductive paste is a paste having conductivity, for example, a powder of a conductive metal such as copper, silver, gold, carbon, or nickel is epoxy resin, phenol resin (resole resin or novolac resin), polyimide resin. And the like mixed with a heat resistant resin. As a filling method, there are screen printing, roller coating and the like, but in order to accurately fill only the concave portion, it is preferable to print by screen printing one or more times. When the conductive paste is printed on a place other than the concave portion, a method of removing it by polishing with a buff or a belt sander is effective. In this way, a single-sided or double-sided copper clad laminate is obtained.

Further, in the case of producing a multilayer printed wiring board, a second photosensitive resin layer (4) is formed on the printed wiring board obtained above (E), light irradiation and development are performed. Thus, the concave portion is formed (F), and the concave portion is filled with the conductive paste (5) of the second layer (G). In this way, a multilayer printed wiring board is obtained.

In the present invention, since a concave portion is formed on the surface of the insulating substrate by patterning a photosensitive resin and the concave portion is filled with a conductive paste to form a circuit, it is necessary to use a step of etching a copper foil for forming the circuit. Moreover, since the thickness of the conductive paste can be increased, a printed wiring board having a small conduction resistance value and high long-term insulation reliability between circuits can be obtained. In addition, since the surface of the printed circuit board on which the circuit is formed can be made flat, solder bridges do not occur and component mounting is easy,
Furthermore, it is convenient for multi-layering by build-up. Since a circuit can be formed only by printing as compared with the conventional process using a press, it becomes possible to manufacture a low-cost printed wiring board or a multilayer printed wiring board.

[0015]

EXAMPLES The present invention will be described below with reference to examples. << Example 1 >> A solder resist made of a photosensitive epoxy methacrylate resin was applied to one side of a 1.6 mm-thick glass epoxy laminate using a curtain coater and dried at 80 ° C. for 30 minutes (touching was removed). . It was applied again thereon and dried at 80 ° C. for 30 minutes. Thickness 100 μm
Met. Next, a negative film is placed and UV rays are applied to 30
After irradiation with 0 mJ, it was developed with a 1% sodium carbonate aqueous solution. Further, heat treatment was performed at 150 ° C. for 30 minutes to completely cure the solder resist. Next, using a screen printer, the conductive copper (or
The silver) paste was printed, and heat treatment was performed at 150 ° C. for 1 hour to cure the conductive copper paste to obtain a printed wiring board. The pattern line width and line spacing are each 150 μm
And

Example 2 On one side of a glass epoxy laminate having a thickness of 1.6 mm, a solder resist dry film made of a photosensitive resin of epoxymethacrylate type having a thickness of 100 μm was laminated using a roll laminator, and then a negative film was formed. A film is placed and UV rays are 300 mJ
After irradiation, it was developed with a 1% aqueous sodium carbonate solution.
Further, heat treatment was performed at 150 ° C. for 30 minutes to completely cure the solder resist. Next, a conductive copper paste was printed on the concave portion formed by development using a screen printer, and heat treatment was performed at 150 ° C. for 1 hour to cure the conductive copper paste to obtain a printed wiring board. The line width and line interval of the pattern were each 150 μm.

Example 3 On one side of a glass epoxy laminate having a thickness of 1.6 mm, the solder resist dry film having a thickness of 75 μm used in Example 2 was laminated using a roll laminator, and the cover film was peeled off. Again, the above-mentioned solder resist dry film was laminated thereon to make the film thickness 150 μm. Subsequently, a negative film was arranged, irradiated with 300 mJ of ultraviolet rays, and then developed with a 1% sodium carbonate aqueous solution. further,
Heat treatment was performed at 150 ° C. for 30 minutes to completely cure the solder resist. Next, a conductive copper paste is printed on the recess formed by the development using a screen printing machine, and 1
Heat treatment was performed at 50 ° C. for 1 hour to cure the conductive copper paste and obtain a printed wiring board. The line width and line interval of the pattern were each 150 μm.

Example 4 The solder resist used in Example 1 was applied to one surface of a phenol resin molded substrate having a thickness of 2 mm using a curtain coater and dried at 80 ° C. for 30 minutes. It was applied again thereon and dried at 80 ° C. for 30 minutes. The thickness was 100 μm. Subsequently, a negative film was arranged, irradiated with 300 mJ of ultraviolet rays, and then developed with a 1% sodium carbonate aqueous solution. Further, heat treatment was performed at 150 ° C. for 30 minutes to completely cure the solder resist. next,
A conductive copper paste was printed on the recesses formed by the development using a screen printer, and heat treatment was performed at 150 ° C. for 1 hour to cure the conductive copper paste to obtain a printed wiring board. The pattern line width and line spacing are each 1
It was 50 μm.

Example 5 The solder resist dry film having a thickness of 100 μm used in Example 2 was laminated on the upper surface of the printed wiring board prepared in Example 2 by using a roll laminator, and then a negative film was arranged. Then
After irradiating with 300 mJ of ultraviolet rays, it was developed with a 1% sodium carbonate aqueous solution. Further, heat treatment was performed at 150 ° C. for 30 minutes to completely cure the solder resist. Next, a conductive copper paste was printed on the concave portion formed by development using a screen printer, and heat treatment was performed at 150 ° C. for 1 hour to cure the conductive copper paste to obtain a multilayer printed wiring board. The pattern line width and line spacing are each 15
It was set to 0 μm.

With respect to the printed wiring board or the multilayer printed wiring board thus obtained, the conductive resistance value and long-term insulation reliability were measured, and the results shown in Table 1 were obtained.

(Measurement method) 1. Conduction resistance value: circuit width 150 μm, circuit length 10 cm
Was measured using a 4-point conduction resistance measuring instrument. 2. Long-term insulation reliability: Under conditions of a temperature of 85 ° C. and a relative humidity of 85%, a voltage load of 50 V was applied, and the time until all the test pieces of n = 10 were short-circuited was measured.

Table 1 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Conduction resistance value (Ω) Long-term insulation reliability (time) − -------------------------------- Example 1 6.5 1000 <Example 2 6.3 1000 <Example 3 4 .1 1000 <Example 4 6.2 1000 <Example 5 6.7 1000 <--------------------------------. −

[0023]

According to the present invention, since a concave portion is formed on the surface of an insulating substrate by patterning a photosensitive resin and the concave portion is filled with a conductive paste to form a circuit, it is necessary to use a step of etching a copper foil to form a circuit. In addition, since the conductive paste can be thickened, the conductive resistance is small, the insulation reliability between circuits is high, and it is suitable for manufacturing a low-cost printed wiring board or a multilayer printed wiring board. .

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a manufacturing process of a multilayer printed wiring board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 1st layer photosensitive resin 3 1st layer conductive paste 4 2nd layer photosensitive resin 5 2nd layer conductive paste

Claims (4)

[Claims] 1. A conductive circuit is provided on one or both sides of an insulating plate by providing a photosensitive insulating resin layer in which a conductive circuit portion is removed by development, and filling a conductive paste in the removed portion. A printed wiring board characterized by the above. 2. A conductive circuit is provided on one or both sides of a printed wiring board by providing a photosensitive insulating resin layer in which a portion to be a conduction circuit is removed by development, and filling the portion removed by development with a conductive paste. A multilayer printed wiring board, characterized in that the step of performing is repeated once or a plurality of times. 3. A photosensitive insulating resin layer is provided on one surface or both surfaces of an insulating plate, and a portion which becomes a conductive circuit is removed by light irradiation and development to form a concave portion, and the concave portion is filled with a conductive paste to conduct electricity. A method for manufacturing a printed wiring board, which is a circuit. 4. A photosensitive insulating resin layer is provided on one surface or both surfaces of the printed wiring board obtained in claim 1, and a portion which becomes a conductive circuit is removed by light irradiation and development to form a concave portion. A method for manufacturing a multilayer printed wiring board, characterized in that the step of filling a conductive paste into a conductive circuit is repeated once or a plurality of times.