JPS62186589A - Manufacture of circuit board - 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 Industrial Application] The present invention relates to a method of manufacturing a circuit board using a conductive paste.

[Prior art]

Generally, the method of forming a conductive circuit on a board is to paste copper foil over the entire board and use an etching method to leave the circuit part and melt the other parts to manufacture the conductive circuit. However, this method requires complicated steps such as resist coating, etching, and resist removal, and there are problems such as processing of etching solution, so it is desired to have a simple post-processing method using a dry process as much as possible.

For this reason, various methods of printing conductive circuits using conductive paste using metal powder have been studied because they are industrially simple. As a conventional method, silver paste using silver powder is widely used due to its reliability, but it is very expensive, so development of copper paste using cheaper copper powder as the main conductive material is progressing. It is being

However, copper paste has the disadvantage that conductivity deteriorates due to oxidation of the copper powder, so there are methods of adding organic compounds (for example, Japanese Patent Publication No. 60-58268, Japanese Patent Publication No. 58-24032), and plating methods. (For example, Japanese Patent Publication No. 1988-215!11) and the like have been proposed.

The plating method still has the problem of waste liquid, and the process is complicated. On the other hand, with the method of adding organic compounds, if the copper paste composition is changed to improve adhesion to suit the substrate to be printed, the amount and type of rust preventive agent to be added must be reconsidered; According to research conducted by the inventors, it has insufficient electrical conductivity compared to silver, and also has problems such as poor solderability.

On the other hand, as a new method for manufacturing circuit boards, electrostatic copying method (for example, Japanese Patent Publication No. 127787/1987),
A method of compressing powder in a groove (for example, published patent publication 1986)
502233), but the manufacturing process is complicated and there are problems in forming fine circuit patterns.

[Problems to be Solved by the Invention] The present inventors have discovered that even if a conductive circuit is formed by screen printing using a copper paste that is a mixture of copper powder and a synthetic resin, sufficient conductivity is not achieved. In that case, even if the paste composition is changed to improve the circuit characteristics, or even if the type of board is changed, the conductivity will not be affected and furthermore, the solderability will be good. The present invention was completed as a result of various studies on the production of.

[Means for solving problems]

That is, in the present invention, a mold release agent is applied to one part of a synthetic resin film, and a desired conductive circuit pattern is formed thereon by a printing method using a copper paste containing electrolytic copper powder as a main conductive material. a first step; applying an adhesive having adhesiveness to the substrate over the conductive circuit printed in the first step;
Alternatively, a second step of applying an adhesive to the substrate, and a third step of adhering the synthetic resin film and the substrate while applying pressure with a hot roll, via the adhesive layer applied in the second step. The fourth step is to peel off the synthetic resin film from the release agent layer and transfer the desired conductive circuit pattern onto the substrate.
A method of manufacturing a circuit board is characterized by comprising the following steps.

[Effect]

As the synthetic resin film used in the first step, any film can be used as long as it does not bend when removed or deform when pressure is applied with a hot roll, but films such as polyethylene terephthalate and polyamide are preferred.

The mold release agent may be silicone resin, polyvinyl alcohol, paraffin, wax, Teflon dispersion, etc., as long as it can easily peel off the printed copper paste and synthetic resin film.

As the copper powder which is the main conductive material of the copper paste, it is necessary to use electrolytic copper powder having a dendritic shape, which is obtained by depositing from an aqueous solution by an electrolytic method. Spherical and flaky copper powders obtained by other manufacturing methods do not have excellent performance. There are no restrictions on the particle size of the electrolytic copper powder, but copper powder of 20 microns or less is preferred from the viewpoint of printability.

As the resin component of the copper paste, thermosetting resins such as acrylic, polyvinyl chloride, and ethyl cellulose are preferred, but thermosetting resins such as epoxy, phenol, and melamine can also be used by adjusting the curing time.

The amount of copper powder mixed into the resin may be 75-85% by weight of copper powder and 25-15% by weight of resin, but if soldering properties are required, 85-95% by weight of copper powder and 15-5% by weight of resin. Copper paste with increased weight percentage and copper powder content may be used. As a method for printing the conductive circuit pattern on the synthetic resin film, a screen printing method that is commonly used for printing conductive paste may be used.

The adhesive used in the second step is to adhere the substrate and the conductive circuit, and if the substrate is made of phenol, epoxy, polyimide, or polyethylene terephthalate, an appropriate adhesive can be freely selected from known adhesives. Just do it.

In the third step, the heat roll is a heated rubber roll or metal roll, and the heating temperature needs to be changed depending on the synthetic resin film and adhesive used, but it is 150°C or more.
200℃ is good. There is also a method of applying pressure using a press instead of a roll. This is not an industrially preferred method because pressure may not be applied uniformly and continuous production is not possible.

The pressure to be applied is preferably high enough to prevent the line width of the conductive circuit formed by the copper base from expanding too much due to the pressure.

The synthetic resin film can be peeled off by physically peeling it off, and if the substrate is also in film form, each can be wound up with a roll.

The following may be considered as the reason why the circuit board obtained by the manufacturing method of the present invention has excellent conductivity and good solderability.

The copper powder that is the main conductive material of the copper paste used in the present invention is electrolytic copper powder and has a dendritic shape, so the copper powders become entangled with each other with a small amount of pressure, reducing the contact resistance between the copper powders in the coating film. conductive performance close to that of silver paste. In addition, if you try to increase the solderability by increasing the amount of copper powder using the conventional method, as stated in Japanese Patent Publication No. 112386/1986, if the conventional printed circuit remains the same, the board However, with the manufacturing method of the present invention, there is no problem with the adhesion to the board because the adhesive is used, and the conductivity is also reduced because the copper powder gets entangled with each other. Therefore, since better conductivity can be obtained, solderability can be improved by increasing the amount of copper powder without considering these other properties.

Furthermore, a feature of the manufacturing method of the present invention is that since the printed conductive circuit is transferred, the copper powder that was precipitated at the bottom of the coating film in the conventional printing method appears on the surface of the circuit in the method of the present invention.
It is also thought that the surface will be very smooth and the solderability will be improved.

As mentioned above, in the manufacturing method of the present invention, there is no need to consider adhesion with the substrate or conductivity, so long-term production using a copper base suitable for the intended circuit, that is, using various additives, is unnecessary. Another feature is that copper paste with excellent durability and heat resistance can be applied.

An embodiment of the present invention will be described below.

〔Example〕

FIG. 1 is a schematic diagram of a circuit board manufacturing apparatus used in an embodiment of the present invention.

In this example, a method was used in which adhesive was applied to the substrate in advance.

The manufacturing apparatus used in this example includes a roll (6) made of hard silicone rubber, a metal roll (7), and a heater (8) that heats the silicone rubber from the outside.

Next, a process for manufacturing a circuit board using this apparatus will be explained.

First, a 25 μm polyethylene terephthalate synthetic resin film (1) was coated with a silicone resin (2) as a mold release agent, and a desired circuit pattern was formed by screen printing with copper paste (3).

The copper paste used contained 85% by weight of 5 μm electrolytic copper powder and 15% by weight of acrylic resin, and the viscosity was adjusted with toluene and methyl ether ketone.

Next, a 75 μm polyethylene terephthalate resin substrate (
5) coated with adhesive polyester resin (4) was manufactured.

The synthetic resin film thus produced and the substrate were placed between the rolls (6) and (7) so that the conductive circuit portion was in contact with the substrate as shown in the figure.

The synthetic resin film and the substrate were moved at a speed of 10 cm/sec while being heated by applying a pressure of 2 kg/cJ to the roll (6), and the conductive circuit was brought into close contact with the substrate via the adhesive. After cooling for a while, the unnecessary film was peeled off from the mold release agent layer to produce a circuit board having the desired conductive circuit pattern.

Table 1 shows the specific resistance values of the coating film obtained in this example, and as a comparative example, the resistivity values of the circuit coating film obtained by the conventional method, that is, screen printing the copper paste used in this example on a board. Indicates specific resistance value.

Table 1 [Effects of the Invention] As explained in detail above, the manufacturing method of the present invention is characterized in that an excellent conductive circuit can be obtained using a conductive base using inexpensive copper powder as the main conductive material.

Furthermore, since the conductive copper paste is less affected by resins and additives tailored to the substrate, printed circuits suitable for the purpose, such as long-term reliable circuits, heat-resistant circuits, etc., can also be manufactured using the manufacturing method of the present invention. You can get it at

Therefore, printed circuits for which only silver paste could be used and printed circuits manufactured using copper foil can be produced by the manufacturing method of the present invention, which is an industrially useful invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a circuit board manufacturing apparatus used in an embodiment of the present invention.

1-Synthetic resin film 2-Release agent layer 3 ~ Coating film with copper paste 4-Adhesive layer 5-board 6-Heat roll 7-roll 8-Heater

Claims (1)

[Claims] The first step is to apply a mold release agent onto a synthetic resin film, and then form a desired conductive circuit pattern by a printing method using a copper paste containing electrolytic copper powder as the main conductive material.
a second step of applying an adhesive having adhesiveness to the substrate from above the conductive circuit printed in the first step, or applying an adhesive toward the substrate; a third step of bonding the synthetic resin film and the substrate through the applied adhesive layer while applying pressure with a hot roll;
1. A method for manufacturing a circuit board, comprising a fourth step of peeling off the synthetic resin film from the release agent layer and transferring a desired conductive circuit pattern onto the board.