DE861119C - Process for the production of printed electrical circuit elements - Google Patents

Description

Process for the production of printed electrical circuit elements The invention relates to a method for producing electrical switching elements and electrical circuits made by printing processes.

During the past few years there has been demand for printed Circuits increased more and more as one. their possible uses more and more and the methods of making them have since improved.

Various methods of making printed electrical circuits have become known so far. In one method, the circuit is made by means of a suitable color varnish painted on the base plate. Here, painting can be done using a stencil. In a variant of this process, it is melted Injected metal. Furthermore, metal coatings are stenciled by simultaneous Syringes made from separately prepared solutions of suitable chemicals. Finally, one method proposed using stencils to metals splash.

Another variation of the process is to place a sheet of metal on the Base plate applied, and having a masking varnish on for the capacitors required metal surface has been applied, the remaining. metal etched off and the masking varnish removed. Most used fabrics for tacking the Leaf metals are curable adhesives. One embodiment this process is the transfer printing process, being a. with a varnish and plastic coated paper is used and hot pressing is applied.

In all of these procedures it is. important to have a uniform product with a minimum. to get from committee. Most known procedures revealed. themselves. various difficulties. These consisted in the products were not even and so the percentage of rejects was quite high.

There has now been a method of printing electrical circuit elements and printed electrical circuits were found to produce very uniform products can be obtained which is easy to monitor and in which the unused conductive materials can be recovered for reuse. After this In addition, overprinting can easily be carried out according to the method of the invention.

The inventive method for producing printed electrical Switching elements is that. on the surface of an organic electrically insulating material essentially of. non-volatile organic substances Free coating of an electrically conductive material applied in finely divided form and the material provided with the coating with a relief printing plate at the same time Application of heat and @ pressure is brought into contact with the application coming temperatures, pressures and times are chosen so that the individual Particles of the conductive material are connected at the points of contact and at least partly in the underlying insulating material with no significant change the electrical; Surface properties are embedded and that 'on this the Coating of the conductive material from the. not in contact with the printing press previous positions is removed.

Those used in the present invention. Starting materials exist made of a finely divided conductive material that conducts well or less well can be, such as B. fine: dispersed silver or carbon. These are in a volatile diluent, optionally with a small addition of one less volatile organic solvent that acts as a temporary adhesive. Suitable diluents are, for example, lower alcohols, in particular methanol and ethanol, the cyclic ethers, e.g. B. Dioxane, the lower. aliphatic ketones, such as B. acetone and methyl ethyl ketone, and water. When choosing the diluent Care must be taken that there are no undesirable effects; such as B. swellings on the surface of the insulating material. The in the invention Method used conductors are z. B. finely divided silver obtained by filtering and washing a preparation made by a proposed method is obtained, furthermore finely divided copper, carbon black, and colloidal graphite. the less volatile organic diluents present in the slurry are for example the lower polyhydric alcohols, such as. B. ethylene glycol and glycerin, and the amino alcohols, such as. B. monoethanolamine. The weight percentage at fixed. Substances in the slurry varies widely and depends on the one used Fabric off. In the case of finely divided silver, the ratio can be approximately q. : i be while when using carbon black a ratio. from i: i is suitable.

The organic electrically insulating material can be: a thermoplastic or hardenable plastic or a highly polymeric product. These substances can also with inorganic insulating materials, such as. B. asbestos, silica or glass fibers are weighted down. Suitable electrically insulating materials are z. B. Phenolform.-aldchyd- and Anilinformaldehydkuns.tharze, polyacrylic resins, such as z. B. polymethyl methacrylate, polyvinyl resins, such as. B. Polystyrenes, and Polyethylenes. There can also be mixtures of thermoplastic and curable plastics, such as z. B. the so-called styrene copolymers, and the products are used by the use of such mixtures, such as. B. Phenol-formaldehyde condensation products with a low proportion of polyvinyl chloride. These substances can in different. Forms., Such as B. in thin, round or elliptical layers, even. somehow arched. . Layers, extruded shapes, into shape. thin films, lined panels, and block form can be used.

In the following an embodiment of the invention is described in which a printed circuit is produced with the aid of a silver preparation on a phenol-formaldehyde layer. The plate, into which any number of holes can be drilled, is evenly coated with the finely distributed silver. For this purpose can. a slurry of spongy silver in methanol can be sprayed onto the surface of the phenol-formaldehyde layer. The greater part of the methanol is then removed by drying, with a small part being retained to temporarily adhere the silver to the layer. The layer is then placed in a press, and the one with the. The coated surface is brought into contact with a heated relief printing plate. Here, the printing plate can consist of a printing plate customary for copper relief printing. In this process, the use of the highest possible pressure and the lowest possible temperature is preferred. Here times are of the order of magnitude; from i to io seconds applied. For phenol-formaldehyde isolators, pressures are approximately 70 atm. and temperatures of about 200 ° C. and contact times of about 4 seconds are particularly suitable if fabrics with a fairly well-defined melting point can be printed. the printing plate can be heated slightly above the melting point for a short time. In this way, polyethylene can be printed using a printing plate maintained at a temperature of about 20 ° C. above the melting point. A prerequisite for this, however, is that the contact times are sufficiently short, namely, for example, 1 sec. In curable plastics, very high temperatures, e.g. B. Zoo up to 25o ° C, high prints, z. B. 70 to iq.o atm., Preferred. The fabrics that soften when heated can be printed on using a printing plate that can be kept at a much higher temperature than the one at which they soften. In a way, the contact time seems to be dependent on stone. of, the printed surface.

One continuous, previously with the conductive material on one side provided roll can be printed by placing it between two rollers can slide through, one of which is heated and the relief printing plate on its surface bears. This roller is in contact with the side of the material which has been coated with the conductive material. If desired, the other can Side of the material in the same way in a subsequent operation; can be printed. This method. is very suitable if very short contact times; desirable sin. The pressure at the point of contact of the rollers can be any Value can be set.

At. the places where the, silver or other conductive material was not in contact with the relief printing plate, it becomes: conductive material only held very loosely after pressure treatment. Hence, these substances can easily brushed away or blown away by compressed air. That way, most of the time it is possible to recover the unused material. This: is special: Advantage in the case of a material such as silver, that is proportionate. is expensive.

If 'a printed circuit made in the manner described' the gaps that were left free for the resistors can be be overprinted. Here, the entire surface of the once printed. plate with a poorly conductive material, such as. B. graphite, on the same already described Way to be covered, and then the plate using a second Relief printing plate, which only has the corresponding relief parts for the resistors, reprinted. In order to make contact, it is necessary that on the lines at the .suitable places. there is little overlap. The one not used Graphite can then be brushed away. Optionally, the resistors can go first printed and then the metallic conductors are printed.

Not only complete circuits, but also individual switching elements such as -z. B. coils can be printed in this way. An important feature of the process is that the conductor touches the surface of the insulating material without a. Permanent binder, can be applied. A small amount of the boiling organic liquid or the residue of the more volatile diluent remains on the surface of the insulating material to secure the particles of the conductive material thereon. These diluents are available at least at the locations; where the relief printing plate was in contact with the insulating material. In the finished product, the particles are firmly attached to one another, and at least the lower parts of these parts are firmly embedded in the insulating material at the printed areas.

The higher boiling organic liquid can be chosen so that it counteracts the inclination of the conductor during the first stage of the process to change chemically. So when using spongy silver one can A small addition to ethanolamine can be made to reduce the oxidation of silver to silver oxide to prevent or reverse such a reaction if it occurs during hot pressing should enter. However, since the reduction is an exothermic process. is, is not possible to use pure silver oxide in the process of making electrical parts to use by coating. Examples i. A layer of polyethylene with a melting point of about 15 ° C and 0.08 cm thick was used. The shift was with a slurry of: sponge silver in methanol containing 2% glycerine injected. The slurry contained 80 parts by weight of silver for every 20 parts by weight Diluents. The greater part of the diluent was then used Air evaporates. The essentially dried layer was placed in a press brought and with a copper relief printing plate, .that kept at approximately i35 ° C was brought into contact, the pressure used being approximately 3.5 atm., the Contact time was a little less than 1 sec. Then the layer came out removed from the press and blown away the unpressed silver.

If the press is operated at a temperature of i2o ° C, is a contact time of 2 to 3 seconds is required. The surface of the layer can 'then, if desired, polished.

2. A layer consisting of. Polymethyl methacrylate of a thickness of 0.6 cm and an initial softening point of 80 ° C. was used: This layer was made with carbon black of low absorption for oil suspended in ethyl alcohol was splattered. The ethyl alcohol used contained 2% glycerine. The carbon black and the liquid diluent was used in equal parts by weight. the The coated surface was made substantially by infrared rays dried and then placed in a press with a relief printing plate, the was operated at 145 to i60 ° C, the pressure used being 35 atm. and the contact times between 3 and 6 seconds. Here, the shorter times were with the higher Temperatures applied. Of the. Soot got from the uncompressed places removed by brushing in water.

3. A polystyrene layer 0.0013 cm thick was sprayed with sponge silver, which had an average particle size of 50 µ, as described in Example i. The layer was placed between two rollers, one of which had a relief print pattern and the one at the contact points to a pressure of 1.4Atm. could be set. The temperatures used were between 125 and I40 ° C, and the speed of the passage; was about 122 cm per minute. After passing through the roller, the silver was removed from the uncompressed areas by washing in a trough.

4. A phenol-formaldehyde layer 0.3 cm thick was used. This layer was sprayed with sponge silver using methanol containing .5% ethanolamine, the suspension containing 80 parts by weight of silver for every 20 parts by weight of diluent. The sprayed surface was substantially dried by infrared rays and then placed in a press having a plate with a relief pattern. This press was at 20o ° C and a pressure of 7o atm. operated. The contact time was 4 seconds. Unpressed silver was removed from the printing plate by brushing.

5. The procedure of Example 4 was repeated by replacing of sponge silver. an electrolytic copper powder was used, which was passed through a 400-mesh sieve went.

6. This example explains that; Printing resistors on a Board that already has a printed circuit, as made according to Example 4 was exhibited.

A slurry of colloidal graphite in water became uniform applied to the entire surface of the plate. This was already with the silver parts printed on the circuit and was dried by means of infrared rays at i40 ° C. The coated plate was then placed in a press which at 175 ° C and a pressure of 84.3 atm. was operated. The time of contact with the relief printing plate was 10 seconds. This printing plate was for those in the circuit required resistances and showed a slight overlap on the appropriate positions on the line to effect contact. The circuit was previously printed on the plate, as described in Beispi @ a 4. To Removing from the press, the plate was washed well and brushed in water.

7. One. an.ilinformaldehyde layer provided with inlays was used and this was treated as described in Example 4. The layer was placed in a press and at 185 ° C and one. Pressure of 49.2 atm. while Pressed for 4 seconds. Resistors were placed on the plate as described in Example 6 imprinted.

B. This example shows the printing of electrical wires: on a plate that already has resistors.

A phenol-formaldehyde layer 0.3 cm thick was used here. A slurry of colloidal graphite in water was applied evenly over the entire surface. This coating was dried at i40 ° C by means of infrared rays. The coated plate was then placed in a press operating at 175 ° C and a pressure of 84.3 atm. was operated. The contact time with the relief printing plate was 10 seconds. After removing it from the press, the plate was washed off well and brushed off in water.

The plate was then, as described in Example 4, with a Circuit, consisting of silver particles, printed with small overlaps on which resistors were attached to ensure a secure contact.

Claims (5)

PATENT CLAIM: i. Process for the production of printed electrical Switching elements, printed electrical circuits or printed: electrical Resistors, characterized in that on the surface of an organic electrically insulating material an essentially, non-volatile organic matter Free coating of an electrically conductive material applied in finely divided form. and the material provided with the coating with a rotogravure printing plate, which the Pattern of the circuit or resistance in relief bears, under simultaneous Application of heat and pressure is brought into contact, the being applied coming temperatures, pressures and times are chosen so that the individual Particles of the conductive material at the contact points are related or a forming a bad leader and at least in part by. underlying insulating Material embedded without any significant change in the electrical surface properties and that thereupon the coating of the conductive material of the not with areas in contact with the printing press are removed. 2. Method of manufacture of a printed electrical circuit.,. characterized in that the electrical Lines and at least one resistor. in any order one after the other be printed according to claim i. 3. The method according to claim i and 2, characterized in that that the organic electrically insulating material is made of phenolformal.dehyde or Anilline formaldehyde resin, polyamide, polyacrylic, polyvinyl resin, polyethylene, one Styrene copolymer or a phenylformaldehyde vinyl chloride copolymer consists. q .. Method according to Claims 1 to 3, characterized in that the electrical conductive material in the form of a slurry in a volatile diluent, optionally with a low content of, a less volatile organic Solvent, is applied. 5. The method according to claim r to q., Characterized in that that a hardenable plastic is used as an electrically insulating material, with temperatures of about zoo to 25o ° C and pressures full about 7o to iq.o atm. come into use.