JPH05218619A - Manufacture of circuit board - Google Patents

Abstract

PURPOSE:To form a high-reliability wiring pattern in an insulating board having a three-dimensional shape by a method wherein, while the molding face of a molding mold is being pressed to the insulating board, a conductive paste is fed to a recessed part or a hole part and the paste is hardened. CONSTITUTION:A molding mold 5 provided with a molding face whose shape corresponds to the surface of an insulating board 1 is used; a recessed part 4 or a hole part 2 which corresponds to a wiring pattern is formed in the molding face of the molding mold 5 or in the insulating board 1. While the molding face of the molding mold 5 is being pressed to the insulating board 1, a conductive paste 7 is fed to the recessed part 4 or the hole part 2, and the paste is hardened. It is preferable that the recessed part 4 is formed only in the insulating board 1 because the surface of the circuit board 1 which is obtained is made smooth and a component can be mounted easily. The hole part 2 is formed normally in the insulating board 1. Thereby, the wiring pattern whose reliability is high can be formed easily on the insulating board 1 provided with a three- dimensional shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a circuit board on which an electronic circuit or the like is formed. More specifically, it is intended to provide a method capable of easily manufacturing a highly reliable electronic circuit board by supplying a conductive paste using a mold and curing the paste to form a wiring pattern. is there. The method of the present invention is particularly preferably used for manufacturing a circuit board in which a wiring pattern having a through hole is formed on a three-dimensional insulating board, that is, a so-called three-dimensional double-sided circuit board.

[0002]

2. Description of the Related Art Recent electric and electronic devices have been rapidly reduced in size and weight. For this size reduction and weight reduction, for example, the field of use of printed wiring boards is expanding,
In particular, printed wiring boards are often incorporated in household electric appliances or industrial appliances.

Conventionally, in order to miniaturize equipment, it has been widely carried out to mount electric / electronic components on an insulating substrate having a three-dimensional shape and to form a wiring pattern on the three-dimensional insulating substrate. There is. Among these, as a specific method adopted when forming a wiring pattern on a three-dimensional insulating substrate, a flat printed wiring board is fixed to the surface or inside of the three-dimensional insulating substrate with a screw or an adhesive. Method, the wiring pattern is formed on the transfer film with a conductive paste, etc., and is inserted into the mold of the injection molding machine to form a transfer film from the resulting molded product. A method of transferring a wiring pattern to the surface of a three-dimensional insulating substrate by peeling, a metal foil on which a wiring pattern has been printed beforehand with an etching resist is inserted into a mold and molded, and then etching is performed to perform wiring. A method of forming a pattern is known.

[0004]

In the above method, the degree of miniaturization that can be achieved is unsatisfactory, and the printed wiring board often peels off due to vibration or the like. On the other hand, with the method (1), it is difficult to form a wiring pattern on both sides of a three-dimensional insulating substrate, and even if it can be formed on both sides, it is not easy to electrically connect the wiring patterns on both sides. Moreover, since the material of the insulating substrate is limited to the thermoplastic resin or the like, it is difficult to apply it to the insulating substrate in which the metal is coated with the insulating material.

These conventional techniques have many problems in forming a three-dimensional circuit, particularly a three-dimensional double-sided circuit, and it is quite difficult to easily manufacture a three-dimensional circuit board having a curved surface or the like, especially a three-dimensional double-sided circuit board. It was

[0006]

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have found that a conductive paste is added to a molding surface of a molding die and / or a concave portion formed on an insulating substrate. It has been found that a highly reliable circuit board, particularly a three-dimensional double-sided circuit board having a through hole, can be easily manufactured by performing a specific operation such as supplying to a hole and / or curing, and completed the present invention. Came to do.

That is, according to the present invention, when a wiring pattern is formed on an insulating substrate using a conductive paste to manufacture a circuit board, a molding die having a molding surface having a corresponding shape on the surface of the insulating substrate is used. A recess and / or a hole corresponding to a wiring pattern is formed on the molding surface of the molding die and / or the insulating substrate. While the molding surface of the molding die is pressed against the insulating substrate, the depression and / or the hole is formed. The method for producing a circuit board is characterized in that a conductive paste is supplied to and cured.

In the present invention, known conductive pastes can be used without limitation. Typical examples of the conductive paste include conductive materials such as gold, silver, copper, nickel, lead and carbon, and crosslinkable epoxy resins, crosslinkable phenol resins, crosslinkable melamine resins, crosslinkable urea resins and the like. Examples of the conductive paste include a thermosetting resin and the like, and a conductive paste including the conductive material and a thermoplastic resin such as polyethylene and polypropylene. Among them, the conductive paste in which a conductive material and a thermosetting resin having a crosslinkability are mixed has good conductivity because of a large volume contraction rate at the time of cooling and solidification, and particularly manufactures a circuit board for a large current. It is suitable for use. Further, it is preferable that this conductive paste does not generate a volatile substance during crosslinking. When a conductive paste that generates a volatile substance during crosslinking is used, it is preferable to devise a curing step by crosslinking because the generation of voids can be suppressed. Further, the resin contained in the conductive paste is preferably a low viscosity resin that does not require the use of a solvent for adjusting the viscosity.

The viscosity of the conductive paste used in the present invention is not particularly limited, and it is generally determined according to the method adopted when supplying the conductive paste as described later. For example, when the conductive paste is supplied by injection, the viscosity of the conductive paste is 10,000.
It is preferably 0 ps (poise) or less because the fluidity is excellent and the wiring pattern can be formed well.

As the insulating substrate used in the present invention, those having various materials and structures can be used without limitation. Typical examples of this insulating substrate are a paper base material-phenolic resin laminated board, a paper base material-epoxy resin laminated board, a paper base material-polyester resin laminated board, a glass base material-epoxy resin laminated board, a paper base material-Teflon. Resin laminated substrate, glass base material-polyimide resin laminated substrate, glass base material-BT
(Bismaleimide-triazine) resin resin laminated substrate,
Synthetic resin substrates such as composite resin substrates, ceramic substrates, glass substrates, etc. that are generally used for electronic circuit boards, and also polysulfone, polyether sulfone, fluororesin, polyphenylene sulfide, polyamide imide, polyether imide, etc. Thermosetting resins and thermoplastic resins with good heat resistance, and metal-based insulating substrates obtained by insulating metal such as aluminum, iron, and stainless with epoxy resin, etc., which are generally used as the material of the enclosure, However, the present invention is not limited to these, and those in which the portion forming the wiring pattern is an insulator can be used without limitation.

Further, as the insulating substrate, not only a flat type but also a bent type or a curved type such as a box type or a cylindrical type can be used without limitation.

In the circuit board manufacturing method of the present invention,
When a circuit pattern is manufactured by forming a wiring pattern on the insulating substrate using the conductive paste, a molding die having a molding surface whose shape corresponds to the surface of the insulating substrate is used.

In the present invention, the material of the molding die used is not particularly limited, but those which do not react with the components in the conductive paste, for example, metals such as steel and stainless steel, ceramics, resins and the like are preferable. More preferable material is
The affinity with the conductive paste is inferior to that with the insulating substrate. In addition, it is preferable that the material near the molding surface of the molding die be an elastic body such as rubber so that when the molding surface of the molding die is pressed against the insulating substrate, the molding surface of the molding die and the insulating substrate are It is preferable because a gap is unlikely to occur and an unnecessary wiring pattern is difficult to form. Although the hardness of the elastic body is not particularly limited, it is 10 to 10 in Rockwell hardness.
90 is preferable.

It is preferable that a heater for heating and curing the conductive paste after being supplied is incorporated in the molding die. As this heater, known heaters can be used without limitation, and examples thereof include circulated heating oil and steam. The temperature of the heater such as the heating oil or steam is usually adjusted in consideration of the curing temperature of the conductive paste.

The above mold is usually provided with a sprue for feeding the conductive paste. The number of this sprue is not particularly limited and may be one or plural. And
It is preferable that the position of the sprue is devised and determined so as not to cause disconnection in the formation of the wiring pattern by the conductive paste.

In the present invention, recesses and / or holes corresponding to the wiring pattern are formed on the molding surface of the molding die and / or the insulating substrate.

The method for forming the above-mentioned recess is not particularly limited. Examples of the method of forming the recess include a method of forming a recess by cutting a commercially available mold or an insulating substrate, a method of manufacturing and using a mold or an insulating substrate in which the recess is formed in consideration of the wiring pattern, and the like. Can be mentioned.

In the present invention, when forming the concave portion, it is preferable to form the concave portion only on the insulating substrate because the surface of the obtained circuit board becomes smooth and components can be easily mounted. The depth of the recess is not particularly limited, but is preferably 0.01 to 20 mm because the cured product of the conductive paste has good conductivity. When the wiring pattern is complicated, it is more preferable to set the depth of the concave portion to 0.5 to 20 mm because disconnection is less likely to occur in the cured product of the conductive paste.

On the other hand, the above-mentioned holes are usually formed in an insulating substrate. Then, when a conductive paste is supplied to the hole and cured, a through hole is formed.

The method of forming the holes is not particularly limited. For example, an insulating substrate formed by using only an insulating material is used, and a method of forming a hole in the insulating substrate or using only the insulating material is used. Examples include a method of manufacturing an insulating substrate so as to have holes in advance, a method of providing a through hole in the above-described metal-based insulating substrate, and then performing an insulation treatment on the inner wall of the through-hole portion of the metal-based insulating substrate.

In the present invention, while the molding surface of the molding die is pressed against the insulating substrate, the conductive paste is supplied to the recess and / or the hole and cured to manufacture the circuit board.

In the present invention, the method of supplying the conductive paste is not particularly limited, and examples thereof include a method using injection pressure.

In the present invention, as a method for curing the conductive paste, a known method for curing the conductive paste can be adopted without limitation. For example, a method of heating the conductive paste may be used. When the conductive paste is cured, it is preferable to perform primary curing in the molding die and then remove the molding die and then perform secondary curing in order to increase work efficiency.

[0024]

According to the method of manufacturing a circuit board of the present invention, a highly reliable wiring pattern can be easily formed on an insulating substrate having a three-dimensional shape with a conductive paste. Further, the method of the present invention can form not only a wiring pattern on an insulating substrate but also a through hole at the same time, and therefore, it is a method which can be particularly suitably adopted in the production of a three-dimensional double-sided circuit board having a double-sided circuit. ..

[0025]

EXAMPLES Examples will be shown below for specifically explaining the present invention, but the present invention is not limited to these examples.

The method for preparing the copper paste used in the examples is as follows.

Average particle size 6.8 μm, tap density 2.99
dendritic electrolytic copper powder of g / cm ³ and specific surface area of 4200 cm ² / g, linoleic acid to the copper powder surface area 0.25 × 10
^-5 mmol / cm ² blended in a nitrogen atmosphere at 1
Premix for 5 minutes in a mortar. The pretreated copper powder thus obtained was mixed with 1,6-hexanediol diglycidyl ether (epoxy equivalent = 165) / novolac type phenol resin (hydroxy equivalent = 105) = 74/26.
456 parts by weight are added to 100 parts by weight of the binder (weight ratio), and 2.8 parts by weight of 2-ethyl-4-methylimidazole are further added to 100 parts by weight of the binder, and then 30 minutes by a three-roll mill. It was kneaded into a copper paste. The viscosity of the obtained copper paste is 280 P at room temperature.
It was S. Example 1 A circuit board was manufactured according to the following steps (a) to (d). The outline of these steps (a) to (d) is shown in FIG.

(A) A through hole 2 constituting a through hole having a diameter of 3 mm is opened in an aluminum plate 1 having a thickness of 3 mm bent at 90 degrees, and the entire surface is covered with an epoxy resin 3 for insulation treatment. went. The thickness of epoxy resin is about 5
It was set to 0 μm.

(B) Two molding dies 5 having a molding surface corresponding to the shape of the insulated aluminum plate were prepared. A concave portion 4 having a depth of 3 mm and a width of 3 mm corresponding to a desired wiring pattern was formed on the molding surface of the molding die. In addition, the molding die is provided with a hollow portion 6 so that oil for heating and cooling can be circulated. Then, on the insulated aluminum plate,
The molding surfaces of the two molds were pressed and fixed.

(C) The copper paste prepared in advance was passed through a plunger at room temperature, and injection was performed so as to be supplied to the molding surface of the mold and the recesses and holes formed in the insulating substrate. This injection is a 50 ton hydraulic press and an inner diameter of 22 mm
Surface pressure of 2 tons by the plunger method using the die of
It was done in cm ² . Then, the silicone paste 8 heated to 150 ° C. was circulated in the hollow portion of the mold for 5 minutes to primarily cure the copper paste.

(D) The mold was removed after cooling, and the taken-out plate was heated at 180 ° C. for 10 minutes to secondarily cure the copper paste to complete the circuit board. An overall view of this circuit board is shown in FIG.

When the wiring pattern of the circuit board obtained through the above steps was ignored, no disconnection or short circuit was found. The volume resistivity of the wiring pattern on the obtained circuit board was measured and found to be 1.2 × 10 ^−4.
It was [Ω · cm].

Example 2 A circuit board was manufactured according to the following steps (a) to (d). An outline of the steps (a) to (d) is shown in FIG.

(A) Thickness 3.5 made of fluororesin
A curved fluororesin insulating substrate 9 having a size of mm, a radius of curvature of 120 mm and a length of 180 mm was prepared by injection molding. At this time, the insulating substrate has a depth of 1 m corresponding to the wiring pattern.
m, a width of 2 mm, and a through hole 2 forming a through hole having a diameter of 1.5 mm were provided, and the insulating substrate was treated with sodium / naphthalene to improve the surface adhesiveness.

(B) Next, two molding dies 5 having a molding surface corresponding to the surface shape of the insulating substrate are prepared, and a hollow portion 6 is provided in the molding dies so that oil for heating and cooling can be circulated. I chose Then, the molding surfaces of the two molding dies were pressed and fixed to the insulating substrate.

(C) The copper paste prepared in advance was passed through a plunger at room temperature, and injection was performed so as to supply it to the concave portion of the molding die. This injection was performed at a surface pressure of 2 tons / cm ² by a plunger system using a 50-ton hydraulic press and a die having an inner diameter of 22 mm. Then 1 in the hollow part of the mold
The copper paste was primarily cured by circulating silicon oil 8 heated to 50 ° C. for 5 minutes.

(D) The mold was removed after cooling, and the taken-out plate was heated at 180 ° C. for 10 minutes to secondarily cure the copper paste to complete the circuit board. An overall view of this circuit board is shown in FIG.

When the wiring pattern of the circuit board obtained by the above steps was ignored, no disconnection or short circuit was found. The volume resistivity of the obtained wiring pattern was measured and found to be 1.1 × 10 ⁻⁴ [Ω · cm].

[Brief description of drawings]

FIG. 1 is a diagram showing a process in manufacturing a circuit board according to a first embodiment.

2 is an overall view of the circuit board obtained in Example 1, in other words, the circuit board obtained by the process shown in FIG.

FIG. 3 is a diagram showing a process in manufacturing a circuit board of Example 2;

4 is an overall view of the circuit board obtained in Example 2, in other words, the circuit board obtained by the process shown in FIG.

[Explanation of symbols]

 1 Aluminum Plate 2 Through Hole 3 Epoxy Resin 4 Recess 5 Mold 6 Hollow 7 Conductive Paste 8 Silicon Oil 9 Insulating Substrate

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[Procedure amendment]

[Submission date] January 31, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (1)

[Claims] 1. When manufacturing a circuit board by forming a wiring pattern on an insulating substrate using a conductive paste, a mold having a molding surface having a corresponding shape on the surface of the insulating substrate is used. The molding surface and / or the insulating substrate is provided with recesses and / or holes corresponding to the wiring pattern. While the molding surface of the molding die is pressed against the insulating substrate, the recesses and / or holes are made electrically conductive. A method of manufacturing a circuit board, which comprises supplying a paste and curing the paste.