NO821481L - PRINT CIRCUIT AND PROCEDURE FOR MANUFACTURING THEREOF - Google Patents

Abstract

Pressure circuit including at least two crossed or superimposed conductor networks isolated from each other with the exception of some interconnection points. Pressure circuit (30) including a carrier (31) such as a polyester film, the upper surface (32) of which is provided with a network of conductor tracks (34-38) and contact areas (39-40) and the lower surface (33) of which also comprises a networks with conductor tracks, these networks being formed by screen printing deposition of conductive ink and polymerizing this ink, the connections between the two networks being established by means of holes (4 2) in the carrier (31), the walls of which are at least partially covered with polymerized conductor ink. The invention relates in particular to flexible printed circuits for their manufacture and method.

Description

The invention relates to an electric pressure circuit of the type which

has at least two crossed or superimposed conductor networks separated by a dielectric.

Conventional "single-sided" and "double-sided" printed circuits are well known and include a dielectric support, generally epoxy resin or glass coated on one or both major surfaces with a thin layer of copper, most of which is then removed to leave a net of conductor tracks and contact pads or areas with copper on one or both carrier rafts.

The main disadvantages of printed circuits are their high cost due to the complicated procedure of their manufacture, due to the loss of large parts of copper which are initially coated on the carrier and due to the fact that they are generally thick and rigid. Copper contact pads or areas also require additional treatment to resist oxidation.

Flexible printed circuits are also known to be provided

by the same process and which differs from it only by the nature of the carrier and which can be a foil of flexible dielectric material. However, the copper tracks on these circuits are brittle and break after folding or hard bending. They are also expensive.

To mitigate these disadvantages, manufacturing techniques have recently been developed on both flexible and rigid printed circuits.

They consist in the deposition of conductor black by means of screen printing on a dielectric carrier, to form a conductor network on a carrier surface. After the ink has been deposited on the support, it is polymerized by heating. Printed circuits are thus provided at a much lower cost than ordinary copper track printed circuits and the conductor track formed by means of polymerized conductor blacks does not break when folded.

At present, however, this method is only suitable for the manufacture of circuits having a single conductor network. Countless attempts have been made to provide such printed circuits with two crossed or superimposed networks which are electrically isolated from each other except at certain connection points. In principle, the experiments consist of: screen-printing a first layer of conductive ink to form a first network on the support, polymerizing the layer to dry and harden it, and then screen-printing a layer of insulating or dielectric ink on certain parts of the first network and polymerizing it until it hardens and drying it, and then screen-printing a second layer of conductive black on the support and on certain parts of the first network and layer with dielectric black and polymerizing the second layer with conductive black by heating it. A second conductor network is thus provided which is isolated from the first by certain zones of intermediate dielectric black and which is connected to the first network by means of zones where the second layer of conductor black is deposited directly on the first layer of conductor black.

The following main disadvantages have been observed with circuits provided in this way: Conductor particles in the conductor blacks migrate through the layer of dielectric black and produce short circuits between the two conductor networks.

Layer of dielectric ink becomes brittle during polymerization and it breaks by folding or bending thereby breaking underlying paths of the first conductor network. Insulating black shrinks a lot when heated and thereby breaks the conductor track that runs over them.

When the insulating black is heated to polymerize, it often forms bubbles that make it impossible to deposit a second conductor layer on it.

Insulating blackened adhesives, bad for some carriers such as polyester foil.

Insulating black must be much thicker than a layer of conductive black which means that the insulating black forms steps or protrusions on the carrier and the first conductive layer. The conductor tracks of the second network where this was deposited over the steps and protrusions have gaps and/or micro-

cracks and does not resist folding.

- Insulating inks become thinner during polymerization heating and in zones where the thinning is marked after it is these bare microdots with the first layer of conductive ink that lead to* short circuits between the two conductive layers. - The dielectric effect of the insulating black layer is not constant over the entire circuit due to variations in its thickness. - Results obtained by using the same inks are not reproducible.

The essential purpose of the present invention is to eliminate these disadvantages.

It provides a printed circuit having at least two networks of crossed or superimposed conductors formed by silk-screen deposition of conductive ink, the circuit being free from the above-mentioned defects and which can be manufactured at a cost 3-4 times less than that of an equivalent circuit provided using known screen printing processes.

For this purpose, the present invention produces a pressure circuit which includes a dielectric carrier and at least two crossed or superimposed electrical conductive networks carried by the carrier, the network being electrically isolated from each other with the exception of these interconnection points, characterized in that each of the networks includes paths with polymerized conductor blacks which are formed on respective sides of the carrier in such a way as to be electrically isolated from each other by means of the carrier, each connection between the networks being provided from one side of the carrier to. the other using an even layer of polymerized conductor black.

In accordance with the present invention, two conductive networks with a printed circuit are completely separated from each other by means of the circuit carrier which is of constant thickness, which has flat surfaces and through which conductive particles to sver-

ten cannot walk.

According to another characteristic feature of the invention, the connection between the networks is holes that pass through the carrier and whose walls are at least partially covered by film with polymerized conductive ink.

The desired connections between two networks are thus very easy to provide by means of holes passing through the carrier, which have walls that are at least partially covered with a film of conductive black, which provides a smooth and reliable connection between the networks.

The characteristic of the invention is totally different from what is previously known with ordinary previously known printed circuits with copper tracks on both sides of a thick and rigid epoxy glass carrier. In previously known technology, the networks are interconnected by means of "patch-through" holes in the carrier. These holes are drilled at desired locations in the carrier after both conductor networks have been completely fabricated and then the cylindrical walls of the holes are coated with a conductive metal film by means of electroplating, which is a long and expensive procedure and which further increases the cost by such printed circuits.

In contrast to the present invention, a connection between the two networks is formed at the same time as the conductor networks in a simple operation and without the circuit being subjected to further processing.

The invention also provides a multilayer printed circuit comprising several crossed or superimposed networks which are electrically isolated from each other except for certain connection points between certain zones of at least some of the networks, characterized in that it includes a printed circuit certain carrier is provided on both its surfaces with a conductor network formed by silk-screen deposition of conductive ink and that at least one surface of the printed circuit and coated with a foil or film of dielectric material whose outer surface has a conductor network formed by silk-screen deposition of conductive ink, the connection holes being formed through the foil or the film and whose walls are covered at least partially with conductive black.

According to another characteristic of the invention, the printed multilayer circuit includes a stack of foils or films of dielectric material, each of which has a conductive network of the above-mentioned type on one surface and which has connection holes with walls covered at least partially with conductive black.

Such a printed multilayer circuit can e.g. be between 1 and 2

mm thick and can be completely flexible and include a large number of crossed or superimposed conductor networks, the number of e.g. lies between 3 and 15.

The invention also provides a method of manufacturing a printed circuit, characterized in that it consists in the formation of holes through a planar support of dielectric material at predetermined points, screen printing deposition of conductive ink on the support to form a conductive network on each of the support surfaces and to cover in at least partially coating the walls of the holes with a film of conductive black and then polymerizing the black by means of heating.

According to another characteristic feature of the invention, the method consists in simultaneous silk-screen deposition of the conductive blacks on both surfaces of the carrier or by silk-screen printing a first network of conductive blacks on a first carrier surface, polymerization of the black by means of heating and then deposition of a second network of conductive blacks on the second carrier surface and polymerizing it by heating.

To produce a printed multilayer circuit, the method consists of attaching a foil or film by direct feeding. rial on a surface of a previously prepared circuit, the foil or film being pierced by holes at predetermined points in such a way that the holes open into the conductor parts of the circuit, silk deposition of a layer of conductive ink on the outer surface of the foil or film to form a conductor network on the surface and to cover at least partially the walls of the holes with conductor black and polymerize the black thus deposited by heating.

This operation may be repeated to provide a multilayer printed circuit comprising a stack of foils or films of dielectric material, each having a conductive network of polymerized black on one of its faces.

The invention will now be described in more detail by means of an example with reference to accompanying drawings, where: Fig. 1 shows an enlarged perspective view of part of a

pressure circuit produced according to prior art.

Fig. 2 shows a section through part of said circuit.

Fig. 2A shows on an enlarged scale a detail of fig. 2

circled with II - A.

Fig. 3 shows a schematic enlarged view of part of one

pressure circuit according to the present invention.

Fig. 4 shows a section through part of the circuit shown in fig. 3.

Fig. 5 shows a block diagram of the steps in the manufacture of

a pressure circuit according to the present invention.

Fig. 6 shows a block diagram of further manufacturing steps for manufacturing a printed multilayer circuit. Fig. 7 shows a section through a printed multilayer circuit according to

present invention.

Reference is initially made to Figures 1, 2,

2A which shows a previously known pressure circuit.

The printed circuit 10 includes a planar carrier 11 made of dielectric material, which can be thick and rigid, but which is advantageously thin and flexible, e.g. such as a 0.1 mm thick polyester film. First conductor paths 13, 14 and 15 are formed on the top surface 12 of the carrier 11 by means of silk-screen printing of a conductive black which is then polymerized by heating.

A layer 16 of insulation or dielectric ink is then silk-screened onto some parts of the top surface 12 of the carrier 11 and the conductor tracks 13, 14 and 15 and then polymerized by heating. The insulation layer 16 is thicker than the conductor paths 13, 14 and 15.

Further leader lanes 17 are then formed as before on the team

16 with insulating black on the top surface 12 of the carrier 11 over some parts of the first conductor paths 13, 14 and 15 at places where it is desirable to provide an electrical connection between a first conductor network consisting of the paths 13, 14 and 15 and a second conductor network consisting of the leader lane 17.

By way of example, the conductor tracks can be about 1 mm wide and 20 to 30 µm thick, while the strip of insulating black is both wider and thicker than the conductor tracks.

Fig. 2 is a section of the printed circuit 10 through a zone where the conductive path 17 of the second network crosses a conductive path 15 of the first network, being isolated from this by means of the dielectric ink strip 16. On the top surface 12 of the carrier 11, the strip 16 forms steps or protrusions 18 over which the conductor track 17 is deposited much thinner than it is over the planar areas due to the fluidity of the conductor host.

Gaps and/or microcracks have been observed to form in the thin zones 19 of the conductor tracks 17.

The main disadvantage of such a previously known drive circuit has been mentioned above. Here further references are made only to the fact that conductor particles (e.g. silver) in the track tend to migrate through the dielectric ink layer 16 to establish short circuits between the two conductor networks. Layer 16 becomes brittle after the warm-up and where it breaks or also breaks the conductor tracks that it covers. Furthermore, the conductor and dielectric blacks are not very compatible with each other and the other network traces 17 adhere poorly to the strip of dielectric black. For this reason, it is often necessary to deposit further layers of insulating black over these parts with the grooves 17 which are themselves deposited on insulating black layers 16 in order to try to strengthen the unit.

Fabrication of a printed circuit such as 10 is a relatively time-consuming process and requires four screen printings respectively to deposit the conductor tracks 13, 14 and 15 on the first conductor network, to deposit the strip 16 on the insulating black to deposit the conductor tracks 17 on the second conductor network and for to deposit additional layers of insulating black 16 on some parts of the second network paths and the first insulating layers. Furthermore, each new layer of tools can be deposited after the previous layer has been polymerized, which entails a series of operations for screen printing deposition and for polymerization by means of heating.

The essential purpose of the invention is to avoid all these disadvantages and also to produce a considerable increase in the quality of the printed circuits.

Reference is now made to fig. 3 and 4 which show a printed circuit in accordance with the invention.

The printed circuit 30 includes a planar carrier 31 of dielectric material, such as a polyester film between 15 and 1500 µm thick, e.g. between 80 and 100 pm thick. Such film is known in the trade under the trade name "MYLAR". Each surface 32 and 33 of the carrier 31 has a respective conductor network formed thereon by means of screen printing deposition with a conductor black which is then polymerized by heating. The network dan-

net on top surface 32 of carrier 31 includes conductor tracks 34, 35, 36, 37, 38, etc. along with contact tabs 39 and 40 connected to tracks 37 and 38 respectively.

The conductor network formed on the bottom surface 33 of the carrier 31 has conductor paths 41, only one of which is shown in fig. 3. The desired connections between the two conductor networks are established via the holes 42 in the carrier 31, the holes having an upper opening in a path in the first network and a lower opening in a path in the second network. A hole 4 2 can be at least partially filled with polymerized conductor black. In the example shown in fig. 3, one end of the path 41 to the lower conductor network is connected by means of such a connection with the path 3 5 to the upper conductor network, while the other end of the path 41 is connected to the path 38 of the upper network by means of a film 43 with conductor black covering at least part of the wall of a hole 4 2 and which forms a ring-shaped edge 44 around each end of the hole 4 2 on the corresponding support surface 31, the outer diameter of the edge being larger than the diameter of the hole 4 2 .

An important characteristic of the invention is that the film 43 of the conductive black covering the wall of the hole is of the same thickness as the conductive black forming the tracks 41 and 38 on the surfaces 33 and 32 of the carrier. After the black has polymerized a perfectly even connection is provided free of defects (so such as gaps, cracks and variations in thickness at the end of the holes). , which is essential when the carrier is a flexible film of thin plastic material, e.g. 80 to 100 pm thickness.. This connection quality through the carrier is due to the method according to the present invention, by means of which the paths and the connection through the carrier are produced in a simple operation. When the holes are filled with conductor black, they contain a relatively large amount of conductor black which is likely to shrink during polymerisation, and there is thereby a risk of cracks around the edges of the holes.

The holes 42 may be circular in cross-section as shown, in which case the cylindrical wall is completely coated with a film of conductive black or else they may be square or rectangular, in which case only one flat face of the hole or a pair of opposing faces is coated

with blackness.

A connection between two conductor paths formed on opposite surfaces of the carrier can also be formed around the edge of the carrier as shown in fig. 3 with reference number 43a.

A projecting edge part of the carrier, such as that shown in fig. 3 with the ends of the webs 34, 35, 36 and 37 can be used as trade by a standard coupling. When the carrier is a flexible film of plastic material, the protrusion part can be folded over a corresponding protrusion on a rigid carrier of suitable thickness.

If so desired, the contact tab or area 39 and

40 together with the tips of the webs 34 to 37 which end at the edge 43 of the carrier 41 and which serve to form a connection with a connector each produced by a different conductor black than that used to produce the conductor webs and which after polymerization is harder than or has greater mechanical strength than the black used for the conductor track. By way of non-limiting example, the contact tabs or areas can be made from blacks produced by the company "EPOTECNY" under the designation H 20 F-1 while the conductor tracks can be made from blacks produced by "COMPTOIR LYON ALEMAND LOUYOT" under the reference V F 5 or of the company "DUPONT DE NEMOURS" under the reference 40 49 .

It is also possible according to the invention to use resistive, capacitive or inductive screen printing hosts such as are commercially available for screen printing of conductor networks containing resistors, capacitors or inductors respectively.

Components such as resistors, capacitors, inductors, transistors, integrated circuits, etc., can be soldered into a circuit in accordance with the invention such as the circuit shown in fig. 3.

In a variant embodiment, the flexible support of a polyester film can e.g. be replaced by a thicker foil or dielectric material, such as a foil made of epoxy glass, e.g. This gives a rigid or a semi-rigid pressure circuit depending on the thickness of the carrier.

In all cases, the diameter of the holes 42 for providing connection between the two conductive networks of the circuit must be chosen in such a way that the hole walls are partially or completely covered with conductive black when the conductive network is formed on the carrier by screen printing. The diameter is a function of the thickness of the carrier and the viscosity of the ink used. It has been observed that for most conductor blacks and for a carrier that is about 80 to 100 µm thick, the best results are obtained with holes that are at least about 0.8 mm in diameter.

Reference will now be made to fig. 5 which shows a diagram of the various steps in the production of a pressure circuit in accordance with the invention.

The first step 45 consists in drilling the carrier 31 to form holes of predetermined size at the places where the connection is to be provided between the two conductive networks. The next step 4 6 consists in the use of two blackened silk screens to deposit a network of conductive ink on each of the surfaces 32, 33 of the carrier 31. This technique of printing or screen printing is well known and will not be described further. The walls of the holes 4 2 drilled through the carrier are coated, at least partially, with a conductive ink film while the conductor network is formed on two carrier surfaces 31. The following step 47 consists in heating the carrier with both its faces having their respective conductor networks to polymerize the manager host. The heating generally takes place in an oven, e.g. by using infrared or ultraviolet radiation at a temperature of 150°C for 5 to 10 minutes.

The printed circuit is then completed and can be used.

If necessary, one or both of the conductor networks can be covered in the usual way by means of a film of dielectric material such as an insulating varnish.

In the variant method, after step 45, where the carrier is drilled, a conductor network is deposited on a single surface of the carrier 31 by means of screen printing followed by heating and polymerization of the ink as before. Then, as indicated by a striped arrow 48, another conductor network is deposited on the other surface and the support is again heated to polymerize black as indicated by a dotted arrow 49.

Contact tabs or areas 39 and 40 can be formed at the same time as corresponding conductor networks, i.e. with the same conductor black or else they can be formed separately with a further screen printing deposition of a conductor black which, after polymerization, will be harder or stronger mechanically than the black of the conductor tracks.

In another variant embodiment, a flexible, semi-rigid or rigid carrier is used which has two surfaces which are already provided with a conductor network, e.g. made of copper. To do this, a common starting point is used for a carrier that has two surfaces that are metallized, e.g.

by means of copper film and the production of a network on each surface by means of ordinary photo-technique, the holes being then drilled through the support and these points where the connection is to be provided between two networks. It is then sufficient to silk-screen deposit conductive black in the zones that have holes and subsequently to heat the unit for polymerization of the black. This technique can also be used to form contact tabs or areas on a conductor network made of copper. A conductor black containing silver particles can be used for this purpose with polymerization causing the particles to form contact areas which are on the copper tracks or which are connected thereto.

Fig. 6 shows a diagram of another variant of the method according to the invention, but here for the production of printed multilayer circuits as shown in fig. 7. The circuit 50 is produced from a pressure circuit 51 provided by means of the method in fig. 5. The circuit 51 thus includes a carrier 52 such as a polyester film which is 'about 80 to 100 µm thick,

with a conductor network on each face including the conductor paths 53 and 54 respectively and interconnected by means of holes 55 passing through the carrier 52 and having walls which are at least partially coated with polymerized conductor black.

A support 56, such as a foil or film of polyester, is attached to the top surface of the support 52 on top of the upper conductor network having webs 53. The support 56 is between 15 and 100 µm thick and is e.g. thinner than the carrier 52 on the circuit 51. A conductor network having conductor paths 57 is formed on the top surface of the foil 56. The holes 58 are formed through the foil 56 and are provided with a film of polymerized black having desired connections between the conductor paths 57 formed on the top surface of the foil 56 and conductor paths 53 in the network formed on the top surface of the printed circuit 51. Another film or foil of dielectric material, e.g. polyester, which includes its own conductor network has conductor webs 61 on its top surface and may be identical to the film or foil 56, is then attached to the top surface of the foil 56 and the conductor network thereon. The holes 62 are then formed through the film 60 and provided with a film of polymerized conductive black to form the desired connection between the conductor tracks 57 and the conductor tracks 61. A hole 62 in the film 60 may be vertically aligned with a hole 58 in the foil 56 and in this case, a connection is established between lanes 61, 57 and 53.

A multilayer printed circuit can thus be built up by stacking films or foils 56, 60, ... each of which includes a conductor network and holes for providing connection between the networks.

The method for producing such a printed multilayer circuit e.g. based on a pressure circuit provided by means of method 5, as shown in fig. 6 a first step 65 where the foil or film 56 with dielectric material is drilled. The next step 66 consists in fixing the foil or film on the surface of the printed circuit 51, e.g. by hot gluing and pressing. The following step 67 consists in forming a network of conductors 57 on the top or the free surface of the foil with the film 56 by means of screen printing deposition of conductor black. The following step 68 is then the heating operation to polymerize deposited conductor black. This operation is then repeated for the foil or film 60.

The invention has many advantages compared to prior art:

The costs of a pressure circuit according to the present invention

is about one-eighth of the cost of a conventional printed circuit using copper conductor tracks on epoxy glass carriers and about one-third to one-fourth of the cost of a printed circuit such as that shown in fig. 1, 2 and 2A.

The percentage of scrap in the production of printed circuits according to the present invention is zero because it is possible to retouch its conductor network produced by screen printing deposition of conductive ink which is subsequently polymerized, while on the other hand the percentage of scrap when producing printed circuits such as those shown in fig. 1 and 2 are 25% to a minimum of 30%.

The insulation between two conductor networks is guaranteed by the thickness of the carrier.

Only two silk screens are used in the method of fig.

5 instead of three or four which are necessary when making the circuits of fig. 1 and 2.

A printed circuit in accordance with the invention can be produced using a single silk screen instead of three or four in previously known devices.

In the method of fig. 5, the circuit is conducted only once

into an oven for polymerization of the black, while with previously known devices three or four passes through an oven were necessary.

A pressure circuit according to the present invention is much more reliable than a pressure circuit of the type shown in fig. 1 and 2 since the conductor ink paths and connections do not break even if the carrier is bent very sharply. Simultaneous deposition of conductor black on both carrier surfaces or two consecutive depositions of conductor black, first on one surface and then on another, always ensures that the walls of the interconnection holes are well • coated with an even layer of a single black that is then polymerized by means of heating and this has the effect of providing a smooth connection free of internal mechanical stresses (which avoids expansion gradients, the appearance of microcracks, etc.).

The thickness of the ink film coating of the interconnection holes is substantially equal to the thickness of the conductor paths formed on both surfaces of the carrier, thereby avoiding the risk of cracking or cracking around the edges of the holes after polymerization.

The invention makes it possible to provide printed circuits

having at least two networks of crossed or superimposed conductors, certain circuits being flexible, semi-rigid or rigid as a function of the nature and thickness of the carrier dielectric material.

The invention also makes it possible to produce printed circuits from foils of polyester which are metallized on both surfaces, e.g. with a thin copper film which is then photo-etched to form a network of conductors on each surface. The connections between the two networks are provided via holes passing through the carrier, the walls of the holes being coated at least partially with polymerized conductive black.

Claims (23)

Printed circuit including a dielectric carrier and at least two crossed or superimposed electrically conductive networks carried by the carrier, and electrically isolated from each other except for certain interconnection points, characterized in that each of the network ends includes paths of polymerized conductive black formed on respective sides of the carrier in such a way as to be electrically isolated from each other by means of the carrier, each of the connections between the networks being provided from one side of the carrier to the other by means of an even layer of polymerized conductor black. 2. Circuit according to claim 1, characterized in that the carrier is a flexible film or foil, e.g. of polyester. 3. Circuit according to claim 2, characterized in that the film is between about 50 and about 1500 µm thick. 4. Circuit according to any one of the preceding claims, characterized in that the connection between the networks is holes passing through the carrier having walls that are at least partially covered by a film of polymerized conductive black. 5. Circuit according to any one of the preceding claims, characterized in that the conductor black which at least partially covers a connecting wall is of the same thickness as the conductor black's paths formed on two carrier surfaces. 6. Circuit according to any one of claims 1-4, characterized in that the networks of the conductor host include interconnection conductor tracks, contact pads, and passive components such as resistors, capacitors and inductors. 7. Circuit according to any one of claims 1-4 or claim 6, characterized in that the networks are formed on the carrier by means of silk-screen printing of conductor black which is then polymerized by means of heating. 8. Circuit according to any one of the preceding claims, characterized in that some of the connections between the two carrier surfaces are formed by means of paths with conductor black deposited over the carrier edge perpendicular to it. 9. Circuit according to claim 7, characterized in that the holes are at least around 0.8 µm in diameter. 10. Circuit according to any one of the preceding claims, characterized in that at least one of the conductor networks is covered at least over its main part by a very thin film of dielectric material, such as insulating varnish. 11. Printed multilayer circuit including several crossed or superimposed networks which are electrically isolated from each other with the exception of certain connection points between certain zones of at least some of the networks, characterized in that it includes a printed circuit according to any of the preceding claims, in that at least one of its surfaces is coated with a foil or film of dielectric material having an outer surface having a conductor network formed by silk-screen deposition of conductive ink, the holes being formed through the foil or film and whose walls are covered with conductive ink, each holes connecting a conductive zone of the network with a conductive zone of a network formed on the raft of the printed circuit. 12. Circuit according to claim 11, characterized in that the outer surface of the foil or film of dielectric material is itself coated with another foil or film of dielectric material whose outer surface contains a conductor network formed by means of screen printing deposition of conductor black and which includes holes, the walls of which are coated with conductive black which provides connection between the conductive network of both foils or films. 13. Circuit according to claim 11 or 12, characterized in that it includes a stack of the foil or film of dielectric material, each of which has a conductor network of the above-mentioned type on a surface and each of which has connection holes with walls covered with conductor black. 14. Circuit according to claim 13, characterized in that some of the holes through the foil are aligned and form a connection between several conductor networks. 15. Circuit according to any one of claims 11 to 14, characterized in that each foil or film of dielectric material is between about 15 and 1500 pm thick. 16. Circuit according to claims 11 to 15, characterized in that the foil with the films of dielectric material is attached to the circuit or to another foil or film by heat-pressing or gluing. 17. Method for the production of a printed circuit according to any one of claims 1 to 10, characterized in that it consists in the formation of holes through a planar carrier of dielectric material at predetermined points, screen printing deposition of conductor black on the carrier to form a conductor network on each of the carrier rafts, and to cover at least the walls of the holes with a film of conductive black and polymerization of the black by heating. 18. Method according to claim 17, characterized in that conductive ink is simultaneously deposited by screen printing on both carrier floats. 19. Method according to claim 17, charac- .sert in that a first network with conductive ink is deposited on a first carrier surface by a screen print, by polymerization of the ink by means of heating, by subsequent deposition of a second network with conductive ink on the second carrier surface and by polymerization of this by heating. 20. Method according to any one of claims 17 to 19, characterized in that flaps with conductive ink are deposited by screen printing on at least one carrier surface and by polymerizing them by heating to provide flaps or zones. 21. Method according to claim 20, characterized in that a conductor black is used for the contact tabs or zones which after polymerization are hardened or have greater mechanical strength than the black used for the conductor paths of the network. 22. Method according to any one of claims 17 to 21 for producing a printed multilayer circuit, characterized in that a foil or film of dielectric material is attached to a surface of the provided circuit, the foil or film being pierced at predetermined points in such a way that the holes open into the conductive parts of the circuit, by screen printing a layer of conductive ink on the outer surface of the foil or film to form a conductive network on the surface and to cover at least partially the walls of the holes with conductive ink and by polymerization of the black thus deposited by heating. 23. Method according to claim 22, characterized in that said operation is repeated to provide a multilayer printed circuit comprising a stack of foils or films of dielectric material, each having a conductor network of polymerized black on its surface.