JPH03179794A - Manufacture of conductive printed board - Google Patents

Abstract

PURPOSE:To simplify a conductive printed board in manufacturing process and to enable it to have a conductive pattern of high quality by a method wherein a pattern is formed on the printed board using a thermosetting adhesive agent, metal powder is made to adhere to the pattern, the surface of the pattern is pressed down, and the board is subjected to a thermal treatment to cure the thermosetting adhesive agent. CONSTITUTION:A pattern is formed on an insulating board 1 with uncured thermosetting adhesive agent 3 through a screen printing method or a roll transfer printing method. Metal powder and/or metal fiber 4 (metal powder or the like) are made to adhere to the pattern of the uncured or the semicured thermosetting adhesive agent. The surface of the pattern onto which metal powder and the like are attached are pressed down by a roller or a press. Lastly, the metal powder and the like attached onto the board other than the conductive pattern are removed by blowing air or spraying water against the board or brushed from the board, and the board is cleaned.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a method for forming a desired circuit wiring pattern or gMI on a substrate.
The present invention relates to a method of manufacturing a conductive printed circuit board used when forming a shield pattern to obtain an electric circuit.

(Prior art and problems) Conventionally, there are etching methods and printing methods using conductive paste as methods for forming conductors such as steel, gold, silver, etc. as wiring patterns on substrates. To melt metal foil with non-wiring patterns,
There is a lot of waste of metal foil, and it is expensive to recover it even once! In addition, there were other drawbacks such as the need to be careful in handling the etching solution. On the other hand, in the printing method using a conductive paste, there is a large difference in specific gravity between the contained metal and the binder (a stirring process must be performed before printing, and the screen printing process requires a conductive paste). However, since the metal powder of the adhesive paste clogs the screen, the screen has to be wiped frequently.

In order to solve the above problems, after forming a pattern on a substrate with a thermosetting adhesive.

There is a method of depositing metal powder on the pattern and curing the pattern, but in this case, sufficient conductivity cannot be achieved. In addition to the above method, there is a method in which ultrafine metal powder is mixed with metal powder and the ultrafine metal powder is melted at the same time as the thermosetting adhesive is cured to form a pattern. Due to the restriction that the melting point of the mixture of ultrafine metal powder must be within the optimum curing temperature range of the M curable adhesive, and furthermore, this ultrafine metal powder is very expensive. However, it has the disadvantage of being extremely costly.

(Means for Solving the Problems) The present invention solves the above-mentioned drawbacks, and provides a method for manufacturing a printed circuit board having a conductive pattern of high quality, which can simplify the process.

That is, in the present invention, a predetermined pattern is formed on a substrate using a thermosetting adhesive, and metal powder and/or metal fibers are attached onto the pattern.

A method for manufacturing a conductive printed circuit board, which is characterized in that the pattern surface is then pressed, and the thermosetting adhesive is cured by heat treatment at the same time as the pressing or after the pressing. This method of manufacturing a conductive printed circuit board is characterized by polishing the surface of the formed pattern after curing.

The manufacturing method of the present invention will be explained below for each step.

Step I> First, a pattern is formed on an insulating substrate using an uncured thermosetting adhesive by screen printing, roll transfer printing, or the like. The insulating substrate can be either a rigid type or a highly flexible tr-flexible type.The rigid type uses resin materials such as glass epoxy and phenol, or ceramic materials, and the flexible type uses resin materials such as paper phenol and polyimide. is used. The thermosetting adhesive may be a melamine adhesive, a phenol adhesive, an epoxy adhesive, or a mixture thereof, which is liquid at room temperature and hardens when heated.

Step (2) Next, metal powder and/or gold fibers (hereinafter also referred to as metal powder, etc.) are attached onto the uncured or semi-cured thermosetting adhesive. The first method is adopted as the attachment method.

■ A method of spraying metal powder, etc. from a nozzle ■ A method of adhering metal powder, etc. by passing it through the substrate ■ A method of attaching a patterned surface formed with a thermosetting adhesive onto the metal powder, etc. The metal powder used in the present invention includes At.

It is not particularly limited as long as it is a powder that exhibits conductivity, such as a metal powder such as A, 9, Cu, At+Pd, or a mixture thereof, or a powder coated with a conductive substance. The shape of the metal powder is one piece.

The particles may have any shape such as dendritic, spherical or irregular, and the particle size is preferably 100 μIn or less, particularly,
1 to 30 μm is preferable.

Particles with a diameter of less than 1 μm are easily oxidized.

The electrical conductivity of the resulting coating film decreases, resulting in poor solderability.

Further, as the metal fibers used in the present invention, fibrous materials of the above-mentioned metals, mixtures thereof, or fibrous bodies coated with a conductive substance can be employed without any restriction. The length of the metal fiber is arbitrarily selected depending on the line spacing of the conductive pattern, but is preferably 150 μm or less and L (length)/D.
(diameter) of 1 to 30 is adopted because the decrease in conductivity is small.

Incidentally, the above-mentioned metal powder and metal fiber can be used not only individually but also as a mixture. The mixing ratio is preferably in the range of metal powder:metal fiber=20=80 to 50:50. Further, the metal powder and the like may be surface-treated with a titanate coupling agent, a silane coupling agent, etc. in order to improve oxidation resistance and conductivity. Furthermore, since the conductive pattern according to the present invention is formed without melting the metal powder, etc., the melting point of the metal powder, etc. is set to 2, taking into account the optimum curing temperature of the thermosetting adhesive or the heat-resistant temperature of the substrate.
Preferably, the temperature is 70°C or higher.

Step ■〉 The surface of the pattern on the substrate to which metal powder, etc. has adhered is pressed with a roller, press, etc. As a result, metal powder etc. are partially or completely embedded in the surface of the thermosetting adhesive!
After heat curing, the binding effect and conductivity can be improved. Note that it is a preferable mode to simultaneously perform pressing and curing using a heated roller, heated press, etc. from the viewpoint of simplifying the process and improving productivity, but it is not necessarily limited to this.
It may be heated and cured after pressing.l/-1.

The pressure is 20-50% of the metal powder etc. in the thickness direction of the pattern.
When the degree of embedding is less than 20%, the binding effect after heat curing is small (the effect of improving conductivity is small. When it is more than 50%, the line width of the pattern increases significantly and fine line properties are reduced. inferior to

Step ■> Finally, metal powder, etc. on the substrate that has adhered to areas other than the conductive pattern is removed and cleaned by spraying with water or air, or by brushing. At this time, a step of polishing the surface of the formed pattern can also be employed. By adopting this process, metal powder etc. that protrude between the pattern lines can be scraped off, and as a result, it is possible to prevent short circuits between the lines and improve the fine line properties of the pattern at the rehabilitation design stage. becomes.

(Effects of the Invention) The conductive printed circuit board manufactured by the method of the present invention has conductive performance comparable to that of conductive patterns produced by conventional screen printing methods, etc., and has no clogging of the screen.
The work efficiency can be improved by omitting the work of wiping the plate. Furthermore, it is possible to prevent short circuits between lines and form a pattern with high isometry. Furthermore, there is no need to use expensive f, H ultrafine metal powder, which can be supplied at a low cost.

Example 1 A phenolic thermosetting resin was screen printed onto a glass epoxy substrate with a portion of the steel foil left on to a thickness of 2Q.
A pattern of 6°w×10m+ is formed so that Arn. Next, silver powder with an average particle size of 10 μm was sprayed onto the pattern from a nozzle, and immediately heated at 150°C for 3
Heat pressing was performed for 0 minutes. After that, excess silver powder outside the pattern was removed by light brushing. next,
The conductive pattern and the steel foil were electrically connected using a dry silver paste, and the resistance value was measured to calculate the sheet resistance value.

The results are shown in Table 1.

Example 2 Same as Example 1, but instead of silver powder, 150 μm in length, L/
Using D10 silver fibers, the pattern was similarly sprayed and heat pressed at 150°C for 930 minutes. Thereafter, the surface of the substrate having the conductive pattern was polished using a puff to remove silver fibers protruding outside the pattern and excess silver fibers. The resistance values were measured in the same manner as in Example 1, and the calculated sheet resistance values are shown in Table 1.

Example 3 The same procedure as in Example 1 was carried out except that instead of using only silver powder, a mixture of silver powder and silver fibers at a ratio of 30:70 was used. The results are shown in Table 1.

Comparative Example 1 Instead of the heat press in Example 1, a patch furnace was used for 15 minutes.
The same procedure was carried out except that heat curing was carried out at 0° C. for 30 minutes, and the results are shown in Table 1.

Table 1 Example 4 Instead of the 60 x 10- rectangular pattern in Example 2, a line of 1111300 μm was used.

A six linear pattern with a line spacing of 3001+m and a line length of 60 is formed using phenolic resin, and the average length of the silver fibers is 50μm.

L/T') 1 in the same manner except that about 10 silver fibers were used.
Heat pressing was performed at 50°C for 30 minutes.

Next, the surface of the substrate having a conductive pattern was buffed to remove silver fibers and red silver fibers protruding outside the lines, and then the conductive lines and the copper foil were electrically connected with a dry silver paste. Next, the presence or absence of electrical disconnections (opens) in each conductive line and short circuits (short circuits) in adjacent lines was examined. Table 2 shows the results of examining each of the 30 patterns, where 1 is defined as the presence of at least one open or short in the conductive pattern (six conductive lines).

Comparative Example 2 After forming a conductive pattern by hot pressing as in Example 4, instead of polishing the surface of the substrate with a puff, only the excess silver fibers were removed by light brushing.

Thereafter, each conductive line was electrically connected to the steel foil in the same manner, and the presence or absence of open and short circuits was examined. The results are shown in Table 2.

4,

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a printed circuit board manufactured according to a representative embodiment of the present invention. 1... Insulating substrate 2... Copper foil 3... Thermosetting adhesive 4... Metal powder and/or metal fiber 5...
drying silver paste

Claims (2)

[Claims] (1) Form a predetermined pattern on a substrate using a thermosetting adhesive, adhere metal powder and/or metal fibers onto the pattern, then press the pattern surface, and then simultaneously or after pressing. A method for producing a conductive printed circuit board, comprising curing a thermosetting adhesive by heat treatment. (2) The method for manufacturing a conductive printed circuit board according to claim (1), wherein the surface of the formed pattern is polished after the thermosetting adhesive is cured.