JPS62282487A - High conductivity electric circuit and manufacture of the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a highly conductive electric circuit and a method for manufacturing the same. This invention relates to an electric circuit transferred to a computer and a method for manufacturing the same.

[Technical background of the invention]

Conventionally, methods for forming electrical circuits such as wiring boards include: (1) forming a copper thin film on a wiring board board, laminating a mask in the shape of a circuit pattern, and chemically etching the WI thin film to form a circuit; A method that uses a special plating method that applies plating only to the circuit part; 2) In addition, a conductive thin film is formed over the entire surface of the support film, and while it is laminated on the transfer target, only the circuit part (transfer part) is heated. A method of forming a circuit by transferring only the circuit portion onto a board using a hot platen that can be pressed (Japanese Patent Application Laid-open No. 141789/1989)
Methods such as these are known.

In the circuit formation method described above, the method of etching the copper thin film is a method that has been used for a long time and is still widely used today, but the copper thin film other than the circuit part must be dissolved and removed. This has the drawback of wasting materials and making it expensive, and when chemically etching a copper thin film with a ferric chloride solution or a cupric chloride solution, masked circuit parts are Another disadvantage is that the copper edges are slightly melted.

Further, although the method of plating only the circuit portion does not result in the above-mentioned waste of materials, it has the disadvantage that it requires special plating equipment and a large amount of capital investment.

Furthermore, a method for forming a circuit in which a conductive thin film is laminated on the entire surface of the support film and then transferred using a hot platen that can heat and press only a predetermined portion requires a hot platen that can heat and press only a predetermined portion. Furthermore, since the conductive thin film other than the transfer portion is discarded, there is a disadvantage that material is wasted and costs are inevitably high. Furthermore, in such a transfer method, since the circuit pattern is transferred by heating and pressing only a predetermined portion using the hot platen, it is necessary that the conductive M film is well-cut. This cracking of the conductive thin film tends to worsen as the thickness of the thin film increases, so it is not possible to make the conductive thin film thicker. If the amount of particles is increased, the adhesiveness of the conductive thin film tends to deteriorate, so there is also the drawback that it is difficult to manufacture a circuit with good conductivity and excellent adhesive strength.

[Summary of the invention]

The present invention has been made in view of the above points, and has good conductivity without requiring special or expensive equipment or increasing costs due to waste of materials. An object of the present invention is to provide an electric circuit using a transfer method with good adhesive strength of the transfer circuit, and a method for manufacturing the same.

Therefore, in the highly conductive electric circuit according to the present invention, 500 to 100 parts of copper powder is added to 100 parts by weight of resin on the circuit board.
It is characterized in that an anti-oxidation film is coated on an electrical circuit which has been transferred and formed with a basic conductive paint by adding 0 parts by weight and treated with sodium sulfide.

Further, according to the method for manufacturing a highly conductive electric circuit according to the present invention, a conductive paint which is basically made by adding 500 to 1,000 parts by weight of copper powder to 100 parts by weight of resin is coated on the support film. A circuit pattern is printed on the film that shows easy peelability when heated and pressurized, and the temperature is 80 to 250℃ and the pressure is 5 to 50℃.
This is characterized in that an electric circuit is formed on the circuit board by heating and pressurizing at 10 Kg/cI11, treated with an aqueous sodium sulfide solution, and further an antioxidant film is formed on the electric circuit.

□According to the highly conductive electric circuit according to the present invention, by treating the electric circuit formed by transfer with sodium sulfide, the copper oxide film covering the surface of the copper powder is removed, and the copper sulfide is removed by the sodium sulfide. As a result of the formation of , the conductivity is improved, so the thickness of the conductive paint that forms the electric circuit is small, and it has the advantage that it has good conductivity with a small amount of copper powder mixed in.
Since it forms an oxidation-preventing film, it prevents the copper sulfide newly generated by sodium sulfide and the copper powder in the conductive paint from oxidizing, resulting in a highly conductive electrical circuit with good durability. .

Further, according to the method for manufacturing a highly conductive electric circuit according to the present invention, a circuit pattern is formed on a support film using a conductive paint, and this is transferred to a transfer target to form a circuit pattern on a circuit board. In addition to being treated with sodium sulfide, an anti-oxidation film is formed. Therefore, conductivity can be improved by (1) treatment with sodium sulfide. (2) It is not necessary to add a large amount of copper powder to obtain the desired conductivity, so there is an advantage that adhesive strength is not impaired. Furthermore, since the oxidation-preventing film is formed to prevent oxidation of the copper powder, there is an advantage that the durability of the manufactured highly conductive electric circuit is greatly improved.

[Detailed description of the invention]

As shown in FIG. 1, the highly conductive electric circuit according to the present invention has an electric circuit 2 formed by transfer on a circuit board 1, and an anti-oxidation film 3 is further formed on this electric circuit 2. It has a structure.

The circuit board 1 is not fundamentally limited in the present invention, and may be of any type as long as the electric circuit 2 can be transferred thereto. For example, ABS
, As5HTPS, polyacecool, vinyl chloride,
It can be a thermoplastic such as nylon, polycarbonate, polyethylene, etc.

The electric circuit 2 formed on the circuit board 1 as described above is
It is formed by transferring a basic conductive paint by adding 500 to 1000 parts by weight of copper powder to 100 parts by weight of resin, and is treated with sodium sulfide.

The conductive paint described above is capable of printing a good fine circuit pattern on the support film that constitutes the transfer body, and uses copper powder that has a potential function as a highly conductive electric circuit. Furthermore, the basic performance as a transfer material,
For example, it is necessary to satisfy various conditions such as being able to peel well from the support film when heated and pressurized, and adhering to the circuit board 1 with sufficient strength without destroying the circuit pattern.

In order to satisfy these conditions, it is important to select the support film and the resin solution (solvent and solute) that will be the base material of the conductive paint, as well as the amount of copper powder added and the particle size. It is also necessary to consider. The resin solution that serves as the base material for such conductive paints includes a resin component (solute) that has adhesive properties with the support film at room temperature and can form a circuit pattern that is easily peeled off when heated and pressurized, such as acrylic, Vinyl chloride, urethane, polyester resins, etc. or one or more of cyclized rubber, chlorinated rubber, rosin, etc., for example, MEK SMIBK, ketone solvents such as cyclohexanone, aromatic solvents such as toluene and xylene, IPA, butanol. It can be a resin solution dissolved in one or more of alcohol solvents, ether solvents, ester solvents, and the like.

The copper powder added to the resin solution is added because it has good conductivity and is inexpensive. For example, if carbon is added as a conductive particle, it will not be possible to create a good conductive electric circuit due to the low conductivity of carbon, silver has good conductivity but is expensive, and nickel has slightly inferior conductivity and , has the disadvantage of being relatively expensive. On the other hand, although copper powder has good conductivity and is inexpensive as mentioned above, some of its surface is already oxidized between the time it is manufactured and used. h has the disadvantage that it is easily oxidized over time during processing, and in particular, it lacks reliability over time during processing. In the present invention, the above-mentioned disadvantage of being easily oxidized is eliminated by forming an oxidation-preventing film, which will be described later.

Such copper powder is used in an amount of 500 to 100 parts by weight based on 100 parts by weight of resin.
Add 1000 parts by weight. Less than 500 parts by weight,
It becomes difficult to reduce the surface resistance to 1.0 Ω/mouth or less after sodium sulfide treatment, which is required for such a circuit filled with metal conductive particles.On the other hand, if it exceeds 1000 parts by weight,
There is a risk that sufficient adhesion may not be maintained.

The average particle size of the copper powder is preferably 10 μm or less. 1
This is because if it exceeds 0 μm, it becomes difficult to form a circuit pattern on the support film by screen printing.

Other additives such as antioxidants, dispersants, etc. can be optionally added to the conductive paint.

Such a conductive ink layer 2 has been treated with sodium sulfide to improve its conductivity. When treated with sodium sulfide, even if oxidized copper powder is used, the sodium sulfide treatment turns into copper sulfide with high conductivity.

The oxidation prevention film 3 formed on the conductive ink layer 2 is formed in order to prevent the oxidation of the copper powder in the conductive ink layer 2, and as described above, the oxidation prevention film 3 is formed on the conductive ink layer 2. Any film that is irritating may be used as long as it can prevent this. For example, it can be a plating film of nickel, tin, silver, gold, or the like. The thickness of such an antioxidant film is preferably 5
It is preferable that the thickness is μm or more. If it is less than 5 μm, there is a risk that the copper powder will be oxidized, and extremely thick plating is not practical from both economical and productivity standpoints.

Next, a method for manufacturing a highly conductive electric circuit according to the present invention will be explained.

FIG. 2 is a sectional view showing a circuit transfer body used in the method of manufacturing a highly conductive electric circuit of the present invention. As shown in FIG. The conductive ink layer 2 is formed by printing a conductive paint that exhibits easy peelability when pressed into a desired circuit shape.

The support film 4 on which such a conductive ink layer 2 is formed is not fundamentally limited in the present invention.
, has good adhesion to the conductive ink layer 2 at room temperature, easily peels off from the circuit pattern under heat and pressure, has heat resistance or smoothness, and is free of solvents contained in the conductive paint. Synthetic resin films that are not immersed in water can be effectively used. Specific examples of the support film 1 include polyester film, polyimide film, polypropylene, and silicone-treated release paper.

Although the circuit pattern 5 is printed on the support film 4 using such a conductive paint, this printing method is not limited in the present invention. For example, it can be effectively printed using known printing methods such as screen printing and gravure printing.

This conductive paint is preferably applied to the support film 4 by:
It is preferable to print to a thickness of 20 to 50 μm.

If the thickness of the conductive paint is less than 20 μm, a large amount of copper powder must be filled in order to obtain a conductivity of 1.0 Ω/mouth or less after treatment, and the circuit board 1 and the transferred electric circuit 2 must be filled with a large amount of copper powder. There is a risk that the adhesive strength of
If it exceeds this, it may become difficult to print a circuit pattern by screen printing or the like.

In the circuit transfer body used in the present invention, the thickness of the lines of the circuit pattern can be freely changed as described above, and the degree of conductivity can be controlled by the thickness of the lines. That is, it is possible to change the conductivity without being limited only to the amount of copper powder filled, and the degree of freedom in designing the circuit transfer body is improved. In particular, by increasing the thickness of the wire, it is possible to reduce the amount of copper powder filled,
Therefore, the adhesive strength of the transferred circuit is improved, and the accuracy is also improved compared to conventional transfer methods.

It goes without saying that it is preferable that the line width or distance between lines of the circuit pattern 5 be smaller. In the circuit transfer body according to the present invention, in order to make it possible to form a circuit with the above-mentioned line width or distance between lines of 0.5 mm or less, the thickness of the lines is further increased (to obtain good conductivity), and the thickness of the lines is increased (to obtain good conductivity). In order to form a circuit with a strong adhesive strength, the viscosity of the conductive paint to be printed is set to 10~10.
It is preferable to adjust to 200 poise. If the density of the conductive paint is less than 10 poise, there is a risk that the line will lose its shape and the circuit will be short-circuited, while if it exceeds 400 poise, it will be difficult to print the circuit pattern on the support film 4. It is.

According to the circuit transfer method according to the present invention, as shown in FIG. 3, a printing foil consisting of a support film 4 and a conductive ink layer 2 is brought into contact with the transfer target portion of the transfer target 1, and heated by means such as a press. Pressing is applied to adhere the printing foil to the transfer target 1, and at the same time, the conductive ink layer 2 is transferred.

The heating and pressing method for performing the transfer is not limited in the present invention, and various means can be used. For example, the transfer can be performed by applying heat and pressure using a hot press or the like.

When transferring the circuit pattern 5, it is preferable to transfer at a temperature of 80 to 250° C. and a pressure of 5 to 10 kg/cIII. If the transfer temperature is lower than 80°C, there is a risk that the circuit pattern 5 formed on the circuit transfer body will not be transferred;
If the temperature is higher than 50° C., there is a risk that the circuit board 1 will be warped, thermally contracted, thermally deteriorated, etc.

Furthermore, if the transfer pressure is less than 5Kg/cj, there is a risk that the circuit pattern 5 will not be transferred well;
This is because if it is larger, there is a risk that the circuit pattern 5 will collapse.

After the conductive ink layer 2 is transferred onto the circuit board 1 in this manner, it is immersed in a sodium sulfide aqueous solution and treated to improve the conductivity of the conductive ink layer 2.

The concentration of such an aqueous sodium sulfide solution is preferably 0.01 to 0.2% by weight.

If it is less than 0.01% by weight, there is a risk that the effect of treatment with an aqueous sodium sulfide solution, that is, improvement in conductivity will be slight, while if it exceeds 0.2% by weight, rather good high conductivity will be obtained. This makes it difficult to adjust the soaking time.

Further, the treatment time with the sodium sulfide aqueous solution is not particularly limited, but can be replaced depending on the concentration of the aqueous solution.

Furthermore, the treatment temperature is not particularly limited, and the treatment can be carried out at room temperature.

On the contrary, if the temperature of the sodium sulfide aqueous solution rises, it is not preferable if the solution comes into contact with the human body due to the alkalinity of the sodium sulfide aqueous solution.

After the electrical circuit 2 thus formed on the circuit board 1 is treated with an aqueous sodium sulfide solution, an anti-oxidation film is formed.

Such an antioxidant film 3 can be formed by an electroless plating method. It is formed only on the electric circuit 2.

EXAMPLES Circuit patterns were printed on a silicone-treated release film at a thickness of 25 μm with various line widths and distances between lines using a conductive paint (viscosity: 70 poise) having the composition shown below.

Composition Acrylic resin 100 parts by weight Ester and ketone solvents 100 parts by weight Copper powder
850 parts by weight (average particle size 2
μm) The circuit pattern printed as described above was brought into close contact with a circuit board made of polyester resin, and the circuit pattern was transferred at a temperature of 130°C and a pressure of 8 kg/-. With line width and distance between lines,
A good circuit with a thickness of 22 μm could be formed with high precision.

Next, a sodium sulfide aqueous solution with a concentration of 0.16% by weight (
Table 1 shows the results of the treatment at a temperature of 25°C) with the treatment time varied in 30 second increments.

(Left below) A highly conductive circuit in which a 5 μm thick anti-oxidation film was formed by plating on the first surface was heated at room temperature for 1000 hours (indicated as A).
Weathering test at 60°C and 95% RH (denoted as B)
The changes in conductivity after performing this are shown in Table 2 below. Second
The measurement results in the table are the results when the initial conductivity was measured using the best value in Table 2.

Table 2 [Effects of the Invention] As explained above, according to the highly conductive electric circuit and the manufacturing method thereof according to the present invention, a circuit made of conductive paint mixed with copper powder by printing means such as printing or gravure printing By printing a pattern and transferring this circuit base to a circuit board, a circuit is formed in a physical form.It is also treated with sodium sulfide and an oxidation-preventing film is formed, so there is no risk of the copper powder being oxidized. ,
Further, there is an advantage that a highly conductive electric circuit having good adhesive strength and conductivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of a highly conductive electric circuit according to the present invention, and FIG. 2 is a cross-sectional view of an example of a circuit transfer body used in the present invention. DESCRIPTION OF SYMBOLS 1... Circuit board, 2... Conductive ink layer, 3...
Antioxidant film, 4...Support film, applicant's agent
Tadashi Amemiya Procedural Amendment W-＜Hōriki

Claims (2)

[Claims] (1) On a circuit board, 500 to 1000 parts by weight of copper powder is added to 100 parts by weight of resin, and a conductive paint is transferred and formed, and the electrical circuit is treated with sodium sulfide. A highly conductive electric circuit characterized by being coated with a preventive film. (2) A circuit pattern that is basically made by adding 500 to 1,000 parts by weight of copper powder to 100 parts by weight of resin on the support film and shows easy peelability when heated and pressurized from the support film. is printed, heated and pressurized at a temperature of 80 to 250°C and a pressure of 5 to 10 kg/cm^2 to form an electric circuit on the circuit board, treated with a sodium sulfide aqueous solution, and further formed an oxidation prevention film on the electric circuit. A method of manufacturing a highly conductive electric circuit, characterized by: