JPS589593B2 - Method for manufacturing printed circuit boards using fast-curing paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed circuit board using a fast-curing paint, and the present invention relates to a method of manufacturing a printed circuit board using a fast-curing paint. It relates to the rapid production of printed circuit boards at low temperatures using light and heat.

Conventionally, printed circuit boards are manufactured by printing paint containing powders of conductors, resistors, and insulators on the board at 150°C to 200°C.
The coating film is cured and fixed by heating at a high temperature of 00°C for 5 to 30 minutes.

However, this method of curing the resin by heating requires a relatively long time and has poor workability, and when copper foil is used as a conductor, the copper foil is easily oxidized because it is exposed to high temperatures. There are various problems in terms of performance, such as a decrease in dimensional accuracy due to heat shrinkage of the substrate, and warping and twisting of the substrate.

On the other hand, UV-curable resins are cured within a few sheets by ultraviolet rays, have fast curing properties, are easy to work with, and have good performance as they cure at room temperature. , carbon black, graphite, or other conductive materials, resistive materials, or insulating powders for electrical elements, the transmittance of ultraviolet rays will be significantly reduced, and the deep portions of the coating will remain uncured and become conductive. Not only do the predetermined characteristics of each element such as a resistor or the like not appear, but also the adhesion to the substrate is insufficient.

This means that when forming a multilayer wiring circuit, an insulating layer is formed between each layer, but an inorganic pigment is added to this insulating layer for coloring or to improve the coating properties of the paint. This also happens when there is a decrease in

The present invention was made in view of the above points, and it is possible to form conductors, resistors, and insulator circuits using an ultraviolet curable and thermosetting coating composition containing conductive or electrically insulating powder on an insulating substrate. Printing maintains the characteristic of fast curing by ultraviolet rays, and compensates for the lack of light curing caused by the deep layer of the coating film and powder formulation, which hinders light transmission, with thermosetting properties, resulting in a fast curing process as a whole. The aim is to manufacture printed circuit boards with high quality and high performance.

The paint used in the present invention has a composition containing a radically crosslinkable prepolymer, a vinyl monomer, a photopolymerizable catalyst, a thermally polymerizable catalyst, and noble metal powder such as gold, silver, palladium, or platinum, or copper powder, carbon black, or graphite powder. and other conductive powders are added and kneaded to form conductive paints and resistor paints.
Alternatively, an inorganic powder is added to the above composition and kneaded to form a coating for insulators.

゛The paint thus formed is printed along the desired electric circuit by silk screen printing on a laminated substrate made of phenolic resin epoxy resin, polyester resin, etc., and is irradiated with ultraviolet rays and heat rays such as infrared rays or far infrared rays. .

Note that coating also includes printing.

In this way, when irradiated with ultraviolet rays, the photopolymerizable catalyst causes a radical reaction between the prepolymer and the vinyl monomer to cause crosslinking, and the thermal polymerization catalyst is excited by the heat rays, thereby crosslinking and curing the prepolymer and the vinyl monomer. .

At this time, in the surface layer of one coating film, ultraviolet curing is mainly accompanied by thermal curing, but in the deeper parts of the coating film, where ultraviolet rays do not pass, only thermal curing proceeds.

Next, examples of the present invention will be described.

Example 1 A conductive paint consisting of 90% by weight of an epoxy acrylate photosensitive resin and 65% by weight of flaky silver powder was printed with a 225 mesh Tetron screen on a paper phenol substrate (Hitachi Chemical MCL-437F). It was cured in 60 seconds by passing twice at a conveyor speed of 3.5 m/min using a three-lamp ultraviolet curing device using a high-pressure mercury lamp with an input of 120 watts/cIfL.

After further curing for 1 minute using a far-infrared curing oven, an insulating paint was screen printed on the conductor pattern as a protective layer for the conductor, and was cured using the above-mentioned ultraviolet curing device at a conveyor speed of 6 m/min.

This time was 3 seconds. The resistance value of this conductor was 74 mΩ/mouth in terms of sheet resistance (Rs).

Further, in a heat resistance test in which this conductor was immersed in molten solder at 260° C. for 10 seconds, the rate of change in resistance value decreased by 13.8%.

For comparison, the sheet resistance (Rs) of a sheet cured using only an ultraviolet curing device without far infrared curing is R
The resistance change rate was as high as 28,377 LΩ/mouth, and the rate of change in resistance in the heat resistance test similar to the previous one in which ultraviolet rays and far infrared rays were irradiated was reduced by 21.7%, which was a larger rate of change than in the case of the present invention.

Example 2 A resistor paint consisting of 90% by weight of epoxy acrylate photosensitive resin and 10% by weight of acetylene black was coated on a paper phenol substrate (MCL-437F, manufactured by Hitachi Chemical) for 22 hours.
Screen printing is performed using a 5-mesh Tetron screen, and the conveyor speed is 3 m using a 3-lamp ultraviolet curing device using a high-pressure mercury lamp with an input of 120 watts/crrL.
It was passed twice under the condition of /min and cured in 50 seconds.

After that, it was further cured for 1 minute using a far-infrared curing oven, and then an ultraviolet-curable insulating paint was screen printed on the resistor pattern as a protective film for the resistor, and cured using the above-mentioned ultraviolet curing device at a conveyor speed of 6 m/min. .

The curing time was 3 seconds.

The resistance value of the resistor at this time is the sheet resistance (Rs), which is R
s=4.3KΩ/mouth.

Further, in a heat resistance test in which this resistor was immersed in molten solder at 260° C. for 10 seconds, the resistance change rate was reduced by 4.3%.

For comparison, the resistance (Rs) of the product that was not cured by far infrared rays was Rs = 4.2KΩ/mouth, and the rate of change in resistance in the heat resistance test was a decrease of 7.4%, which is a large rate of change. there were.

Example 3 An insulating paint composed of an epoxy acrylate photosensitive resin was applied to a paper phenol substrate (manufactured by Hitachi Chemical, MCL-437F).
) A copper foil is used for the lower electrode on top, and this copper foil is screen printed through a 150 mesh Tetron screen,
Using a high-pressure mercury lamp with an input of 80 watts/crfL, the distance between the lamp and the substrate was set to 10 cIfL, and ultraviolet irradiation was performed for 3 seconds.

Thereafter, infrared curing is further performed for 6 seconds.

Then, mercury particles were placed on the formed cured insulating film, and the mercury was used as an upper electrode to measure the insulation resistance of the insulating film using a high-insulation meter.

In this case, the insulation resistance value was 3×10 13 Ω, indicating extremely high insulation properties.

1. On the other hand, for comparison, the case where infrared curing was not performed showed 5 x 10''Ω, indicating that the insulating film properties were significantly improved by infrared curing.

According to the present invention, an electric circuit is printed on an insulating substrate using an ultraviolet curable and thermosetting synthetic resin coating composition containing conductive or electrically insulating powder, and an electric circuit is printed on the substrate. The coating composition is irradiated with ultraviolet rays and then heat is applied for a short period of time to cure the coating composition and fix the electric circuit, so the coating composition is quickly cured at room temperature by ultraviolet irradiation and has good workability. At the same time, since curing by heating is an auxiliary process and takes only a short time, it is not held in a high-temperature, zero atmosphere for a long time for curing, so oxidation of copper foil and insulating substrates may occur due to heat shrinkage. There is no risk of such problems, and the performance of the product can be improved.

In addition, areas that are shaded by ultraviolet rays due to the combination of conductive or electrically insulating powders or areas where the hardening effect of ultraviolet rays is insufficient due to thick coatings can be reliably cured by heating for a short time. Since no parts are left with insufficient powder, the electrical properties of the printed circuit as a conductor, resistor, or insulator made of the blended conductive or electrically insulating powder can be fully demonstrated. In addition, adhesion to the board is ensured, and heat resistance when the printed circuit board is immersed in molten solder can be improved.

Claims (1)

[Claims] 1. An electric circuit is printed on an insulating substrate using an ultraviolet curable and thermosetting synthetic resin coating composition containing conductive or electrically insulating powder, and the coating composition printed on this substrate is irradiated with ultraviolet rays. A method for producing a printed circuit board using a fast-curing paint, which further comprises applying heat for a short period of time to cure the paint composition and fix an electric circuit.