DE19955214B4 - Method for producing conductor structures - Google Patents

Abstract

method for producing conductor structures on rigid or flexible, section or web-shaped Substrates using a printing medium in offset printing, thereby characterized in that two printing units (2, 3), each of which a Applicator roll (5; 15), a plate cylinder (6; 16), a blanket roll (7; 17) and a printing cylinder (8; 18), which are perpendicular to one another, touching, are arranged to form an adjustable gap (38) through which the substrate (14; 24) is passed horizontally, on its front and back sides simultaneously the printing medium is printed on the substrate (14, 24), being on both sides register accurate on the substrate by curing and etching or Application of electrically conductive Print medium, the conductor structures arise.

Description

The The invention relates to a method for producing conductor structures on rigid or flexible, section or web-shaped substrates using a printing medium in offset printing.

The classic production of printed circuit boards is with a variety affected by environmental problems such as high energy consumption, toxic wastewater pollution, material losses during structuring the conductor image, use of various chemical processes, at which polluting substances arise.

Especially for the Realization of fine and ultra fine conductor structures is a high Number of process steps required, which is an additional Consumption of chemicals and energy lead and so the structuring process from the point of view of environmental pollution due to the necessary consumption of resources and the amount of waste generated to a critical sub-step in the overall process of PCB manufacturing can be.

was standing the technique of creating a pattern on a substrate for applications in the field of fine and fine conductor technology, the application of the Photolithography. By this is meant that radiation-sensitive Polymers in liquid or solid form such as liquid resist or dry resist applied to the surface to be structured and by a Positive film or negative film, each serving as a mask exposed through and so the required structure is created. The essential Steps in photolithography are the surface cleaning of the substrate, the whole area Coating the substrate with a photoresist, the exposure through a mask of the substrate coated with the photoresist, the Development of the exposed photoresist, etching the metallic coating of the substrate and stripping the cured photoresist. It will et al made the mask as a positive or negative film by a conductor image original is used for film production, the film is exposed, developed and fixed. After using the Mask in the photolithographic process, this must be disposed of.

For good full-surface adhesion the photoresist needs the metallic surface cleaned and roughened the substrate in a multi-stage process become. This includes a treatment with a mixture of, for example, sulfuric acid and phosphoric acid, a Cascade rinsing, Treatment with sodium persulfate, repeated cascade rinsing, pickling and another cascade rinse. The overflows, the caused by the addition of the various treatment agents, have to in a copper hut be disposed of. The rinsing waters are Although driven in the cycle, must However, by means of ion exchange and distillation before the recent Use be prepared. The handling of the resulting sulfuric acid solutions requires the Compliance with appropriate health and safety regulations. such solutions have to be neutralized before disposal, resulting in an increase their salt freight leads. The whole area Application of liquid or solid resist on the substrate surface takes place in the latter case both sides under clean room conditions in a laminator at about 100 ° C. After Adjustment and exposure through a mask will be outside under normal conditions of the clean room generally with a sodium carbonate solution. In each case, organic film material goes into solution, before the wastewater discharge like, filtered and adapted must become. For the subsequent flush is again relatively much Water required. After flushing, the exposed copper surfaces at elevated Temperature in the next Etched away process step. The etchant residues must be rinsed off and the spent etching solutions can again in a copper hut be disposed of. In the last step, the rest of Resist stripped with caustic soda. Here are each turn organic material in solution. The precipitation and Disposal takes place as in the development step. After the final rinsing process is the finished printed circuit board with hot air dried.

The use of the screen printing technique for the structured application of an etching resist to a metallized substrate is known. So is in the DE 40 20 215 A1 a device for printing by the screen printing method of plate-shaped objects, in particular of electrical circuit boards with paints, etch pastes, Lötstopplacken and the like described.

In this device, two printing devices for vertically oriented plates are provided, wherein the printing devices with their printing sides facing each other and spaced exactly opposite each other. The two printing devices are after moving in a plate to be printed on them and moved away after printing the plate of this. Each of the two printing devices has a screen printing stencil and one or more inking doctor blades and optionally scraper blades, which are each adjustable in an exact opposite of each other. As already mentioned, this known printing device is only suitable for the screen printing method, but not for the photo printing method or an offset printing method. The achievable with screen printing accuracy and the contour sharpness of a circuit pattern and the process-related low resolution make it possible only to achieve lateral structure widths on the circuit board of the same size 100 microns.

Out the publication "Printed Circuit Technology the film etching technique ", author Eisler, Paul, Munich, Carl Hanser Verlag 1961, page 102 is the application of offset printing for printed Circuits known, but there is no evidence of one simultaneous front and back pressure on the substrates. Nor are there any suggestions regarding the dimensions of conductor structures as well as a high register accuracy between front and back pressure the substrates.

From the US 4 458 590 A is a lithographic offset printing press with two printing units is known, each of which consists of a plate cylinder and a Druckfilz- or blanket roll. A fabric tape is printed. The plate cylinders and the blanket rollers are connected together by a rod which is pivotally connected to eccentrics so that the plate cylinders can be swung away from the blanket rollers if necessary. A technical realization of a simultaneous two-sided printing of a substrate for the production of printed circuits on the front and back of the substrate is not addressed, although it can be seen from the document that the offset printing for printed circuits is applicable.

The EP 0 650 831 A1 relates to a printing device for printing the top and bottom of a tape cassette, wherein the upper printing unit of a plate cylinder, is applied to the ink, and a printing cylinder, which is an inking roller with rubber elastic jacket made of silicone rubber. The lower printing unit is constructed in the same way and consists of a plate cylinder and a printing cylinder. An application of such a printing device for producing printed circuits is not mentioned.

In EP-B 0 113 601 is an offset rotary printing machine for variable Formats with a frame described in its upper part a blackening, a moistening device, at least one ink roller and three Pressure rollers and a cassette containing the superimposed pressure rollers supported, these being vertically superposed Touch rollers in printing position. Furthermore, there are funds for moving the cassette horizontally. The waves the three superimposed Pressure rollers are rotatably mounted on a carriage at each end, the one between two vertical, arranged on a post of the cassette guide devices is movable. The carriages are separated from each other by intermediate layers separated, their height corresponds to the distance between the axes of the waves. This distance depends on the print format, the two lower carriages on which the shaft of the lower platen roller is rotatably supported on upper rod ends of vertical lifting cylinders, the one height-adjustable Crossbeam carries. This offset rotary press is only for one-sided printing a substrate suitable.

task The invention is a method for producing conductive patterns to improve so that a two-sided printing of individual Substrates or a substrate tape with conductor structures with high Register accuracy between front and back of the substrates achievable is, whereby the energy and material consumption as well as polluting emissions should be reduced and above In addition, a significant cost savings should be made possible.

These Task is procedurally in the way solved, that two printing units, each of which has an applicator roller, a plate cylinder, comprises a blanket roll and a printing cylinder, which are vertically stacked, touching are arranged to form an adjustable gap through which the Substrate passed horizontally will, on its front and back simultaneously the printing medium is printed on the substrate, wherein on both sides register accurate on the substrate by curing and etching or Application of electrically conductive pressure medium the ladder structures arise.

In Embodiment of the method, the printing medium on the substrate, the metal coated, cured by radiation.

In Another embodiment of the method is the direct imaging of conductor structures by means of a laser plotter on a layer a metal plate is created and each of the two metal plates clamped on the plate cylinder of the respective printing unit.

Conveniently, the substrates are plastic films based on polyimide, polyethylene terephthalate or coated fuel papers.

Immediately after the substrates have been printed, the curing and / or etching of the printed circuit patterns takes place, so that ultimately there is a one-step process from the creation of the conductor structures to the finished circuit patterns or printed circuits. Through this process control, the small widths of the conductor structures and the small distance between adjacent conductor structures, the material consumption is optimized, so that only a very small waste material and thus only small polluting emissions arise, compared to known multi-stage processes in the production of printed electrical circuits.

With The invention is a significant reduction in process steps and associated elimination of the use of chemicals, Electric energy and water achieved. Through the targeted local application of etch resistant printable Medium according to the pattern structure in the printing method according to the invention across from a full-surface Application of photoresist in the conventional method is the consumed amount of photoresist - also because of the smaller layer thickness when printing - to about 60% lowered. Accordingly, there are significant cost savings at the photoresist. As in the method according to the invention no Trockenfotoresiste used, deleted the lamination step, which is under heat takes place, whereby electrical energy can be saved. Will the Printing plates directly exposed by means of a laser plotter, so is also the use of film material for the production of masks or pattern templates are obsolete. The washing out of the printing plates takes place in the method according to the invention with water and is ecologically harmless, since only silicone rubber residues, but not silver ions ins Wastewater, as in the use of conventional Silver halide films is the case. In addition to the high savings Energy, water, photoresist is eliminated also the entire photochemical process and the associated problematic disposal of wastewater. Further advantages result through the use of printable materials that only contain low-toxic components and according to established disposal procedures for printing companies can be disposed of. In addition, there is also the workability when transitioning to a flexible printed circuit board substrate and the possibility given from roll to roll.

The Invention will be explained in more detail below with reference to the drawings. It demonstrate:

1 2 schematically the process steps known in the prior art for producing a one-sided pattern on a substrate,

2 the method steps for producing a single-sided conductor pattern on a substrate according to the invention,

3 schematically a printing device with two printing units for producing a respective conductor pattern on the front and back of a substrate, and

4 a schematic comparison of the method steps according to the invention using a positive and negative pressure clichés and etch-resistant and self-etching pressure medium for the production of one conductor pattern on the front and back of a substrate.

In the process steps used in the prior art, as shown schematically in 1 are shown, a one-sided metallized substrate over its entire surface with a printable medium, such. B. positive or negative photoresist (photoresist) coated and then exposed through a film mask, which is a positive or negative film of a Leiterbildoriginals. Thereafter, the pattern is completed by process steps such as curing, etching and stripping the photoresist. The preparation of the film mask is carried out in such a way that from a Leiterbildoriginal a positive or negative film is produced, which is exposed, developed and fixed. This film mask is then placed on the fully coated photoresist layer and through this film mask is exposed through. The film mask must be disposed of after use, as described above in the introduction to the description.

Of the entire area applied photoresist may be in liquid or solid form (dry resist) be applied to the surface to be structured. The Film or exposure masks are in the form of classic silver halide films Made on a polyester basis. For this purpose, the films, for example, via a Laser plotter exposed and then - after photographic model - under Application of the appropriate chemicals developed and fixed.

In 2 a preferred embodiment of the method according to the invention is shown schematically. A master image original is scanned by a laser plotter and exposed and baked directly onto a silicone rubber layer on a metal plate, ie, the silicone rubber layer at the areas to be printed is burned away by the laser beam. The printing plate thus produced is placed on a plate cylinder 6 . 16 a printing unit 2 . 3 the printing device 1 as they are in 3 shown is stretched.

In another embodiment of the method, the printing plate may be formed in a conventional manner by forming a positive or negative film from a conductor original and then transferring the film image by exposure to the silicone rubber layer of the metal plate become. The printing plate itself consists for example of thin aluminum sheet, which carries a 1 to 2 microns thick silicone rubber layer and can be disposed of in an environmentally safe manner. Excellent resolution, edge sharpness and consistency of the track width are achieved, with both the track width and the distance between the tracks in the range of 5 to 25 microns. As based on 3 will be described, both sides metallized substrates or a metallized substrate web on both sides are printed on the front and back with conductor images. The print is comparable to a waterless offset print. The silicone rubber layer must adhere to the metal plate, which is preferably a thin aluminum plate, for which purpose a primer layer is generally applied to the surface of the aluminum plate. Another possibility is that on the aluminum surface, a radiation-sensitive layer is applied, on which the silicone rubber layer is located. This radiation-sensitive layer then produces the adhesion to the silicone rubber layer and, moreover, changes as a result of the irradiation in such a way that the silicone rubber can be washed off at the non-baked areas by means of water as a lubricant. As a result of the laser irradiation, either only the silicone rubber layer can be burned off at the points to be printed or, together with the silicone rubber layer, the regions of the radiation-sensitive layer lying underneath it.

In 3 is a schematic printing device 1 with an upper printing unit 2 and a lower printing unit 3 shown, wherein Hubverstellvorrichtungen are omitted for clarity. There are either individual discrete substrates 14 . 14 or a continuous substrate web 24 by means of transport rollers 12 . 13 in the printing device 1 introduced. The two printing units 2 . 3 are in the printing device 1 spaced apart exactly opposite each other and each comprise an applicator roll 5 . 15 , a plate cylinder 6 . 16 , a blanket roll 7 . 17 , and a printing cylinder 8th . 18 , Between the printing cylinders 8th and 18 there is a gap 38 whose height corresponds to the thickness of the substrates 14 or the substrate web 24 is adjustable by means of Hubverstellvorrichtungen. The printing cylinder 8th , the blanket roll 7 and the plate cylinder 6 of the upper printing unit 2 are arranged vertically above one another and touch each other. They have the directions of rotation indicated by the arrows. In the same way, the plate cylinder 16 , the blanket roll 17 and the printing cylinder 18 of the lower printing unit 3 arranged vertically above each other and are in contact with each other. An applicator roll 5 of the upper printing unit 2 is horizontal next to the plate cylinder 6 in the upper printing unit 2 arranged and forms a right angle with the vertical arrangement of plate cylinder 6 , Blanket roll 7 and impression cylinder 8th ,

In the same way, an applicator roller closes 15 a right angle with the vertical arrangement of plate cylinder 16 , Blanket roll 17 and impression cylinder 18 of the lower printing unit 3 one. To the applicator rollers 5 and 15 is in each case by means of anilox rollers 9 respectively. 19 a print medium offered. On the plate cylinders 6 . 16 For example, plates are mounted on which with an imaging system 11 . 11 the structured printing cliché was created. Through the application rollers 5 . 15 The printing medium is applied to the printing plates of the plate cylinders 6 . 16 applied. These in turn are in contact with the blanket rolls 7 . 17 that with the printing cylinders 8th . 18 are in contact. The actual printing takes place so that the pressure is not directly on the substrate 14 or the substrate web 24 takes place, but from the right-sided printing plate, these are the plates on the plate cylinders 6 . 16 first on the blanket rolls 7 . 17 is reversed, and from these the printed image in the correct direction on the substrate 14 or the substrate web 24 is transmitted. At the blanket rolls 7 . 17 These are rollers that are equipped with a rubber blanket.

After the exit of the double-sided printed substrates 14 or the substrate web 24 from the printing device 1 becomes a drying station 21 . 21 through, which is constructed symmetrically to both sides of the substrates or the substrate web. This drying station 21 contains on each side at least one spotlight 40 which is arranged in the focal line of the parabolic, spherical or ellipsoidal mirrored inner walls of the housing. At the spotlights 40 . 40 These are UV emitters, which are the structured printed images on the front and back of the substrates resulting from the applied printing medium 14 or the substrate web 24 cure by UV radiation. The removal of the substrates 14 or the substrate web 24 from the printing device is done with the help of further transport rollers 22 . 23 , Etch-resistant or corrosive inks, as well as print media with electrically conductive properties come into consideration as the printing medium. The term "corrosive" refers to a printing ink which has corrosive properties and which directly carries out the etching of the conductive pattern without further etching medium.

In 4 the individual process steps are compared using a negative pressure cliché and a positive pressure cliché each other. The starting point is in each case a metal plate, for example made of aluminum or another metal, which carries a 1 to 2 μm thick silicone rubber layer. In the silicone rubber layer is either a negative image (step (a) of 4 on the left side) or a positive image (step (a) of 4 on the right side) of a circuit pattern structure or a Leiterbildoriginals be burned by means of a laser beam, then rinsed the metal plate to remove silicone rubber residues and the metal plate on the plate cylinder 6 . 16 of the printing unit 2 . 3 clamped. From the application rollers is applied to the printing plates printing medium, such as an etch-resistant or etching ink that fills the silicone rubber-free areas, as in step (b) of 4 shown. The printing plate represents a dry plate, with the help of a dry conductor image is obtained. The printing ink structure of the respective printing cliché is printed on the front and back of the individual substrates or the substrate web in step (c) and then etched away in step (d) the etching ink and the metal-coated areas covered by the substrates or the substrate web or the etch resistant ink cured by radiation and etched away the metal coated areas therebetween. Step (d) of 4 shows that the same pattern is obtained in both cases.

When Silicone rubber layers are known, such as described in DE-A 43 30 279, those used by partial Crosslinking of polymers containing polysiloxane residues as the main skeleton, be obtained with crosslinking agents. For hardening the silicone rubber layers if they are condensed, i. a polysiloxane with hydroxyl groups at both ends is crosslinked with a silane or a siloxane, the hydrolyzable one bonded directly to a silicon atom thereof wearing functional group. An addition type silicone rubber becomes a polysiloxane with ≡Si-H groups and subjecting a polysiloxane having -CH = CH groups to an addition reaction, forming a silicone rubber. The condensed silicone rubber causes changes its curing properties and its adhesion to a photosensitive layer depending on the moisture content the atmosphere while of curing. A particularly suitable silicone rubber is by the crosslinking a mixture of polysiloxanes and a hydrogenpolysiloxane by addition reaction receive. These polysiloxanes contain at least two directly Silicon atoms bound alkenyl groups and alkyl, aryl, aralkyl, vinyl or halogenated Hydrocarbon groups. The hydrogenpolysiloxane contains a Hydrogen or a methyl group, furthermore an alkyl, aryl, aralkyl or vinyl group.

The Catalysts for the addition reaction of these components may be from those in the art selected catalysts selected become. Particularly suitable are platinum compounds such as elemental Platinum, platinum chloride, chloroplatinic (IV) acid or platinum with olefins is coordinated. The silicone rubber may further comprise a crosslinking inhibitor contain. The printing plate must be so flexible be that it be clamped easily on the plate cylinder of the printing unit can and stress during can withstand the printing process.

Examples for substrates or for the substrate web which can be used according to the method are plastic films Polyimide based, possibly on polyethylene terephthalate or coated Fuel paper. The polyimides are polymers with imide groups as main structural units of the main chain. The imid groups can are present as linear or cyclic units. Of special technical Meaning are the polyimides, by polycondensation of aliphatic or aromatic diamines with aromatic tetracarboxylic dianhydrides, the above polyamide acids be prepared as intermediates. To be the polyimides Also polymers counted, in addition to imide also amide, ester and Contain ether groups as constituents of the main chain. The polyimides belong to the high temperature resistant Plastics and high-performance plastics and are characterized by high Strength in a wide temperature range from -240 to +370 ° C, high heat resistance up to about 360 ° C, thermal stability and flame retardancy. They are also resistant to dilute alkalis, acids, Solvent, Fats and oils. Among other things, they are considered carriers of printed circuits, i. used by printed circuit boards.

The according to the inventive method substrates to be printed or the substrate web are plastic films with metallic layers on the front and back. In the case of this plastic Films are preferably polyimides. The layer thickness of the pressure medium 1 to 2 μm. As metal layers u.a. Copper, aluminum, zinc or Steel layers into consideration.

has the pressure medium electrically conductive properties, so are the too printing substrates or the substrate web non-metal coated plastic films, on which arise by printing electrically conductive structures.

With the invention, the advantages are achieved that the substrates of the printed circuit boards on printing rolls of a printing device in the offset process, printed with a printing medium according to the desired conductor patterns are printed so that immediately following the etching of the conductor images can be done. Thus, the previous multi-stage process of printed circuit board manufacturing is reduced to a one-step process of etching after printing. If the printing medium has electrically conductive properties, then the printed circuit board production is further simplified, since then the etching is omitted and the printed circuit boards are completed immediately after the printing of the substrates and drying or hardening of the printing medium.

Claims (4)

Method for producing conductor structures on rigid or flexible, section or web-shaped substrates using a printing medium in offset printing, characterized in that two printing units ( 2 . 3 ), each of which has an applicator roller ( 5 ; 15 ), a plate cylinder ( 6 ; 16 ), a blanket roll ( 7 ; 17 ) and a printing cylinder ( 8th ; 18 ), which are arranged vertically one above the other, touching, an adjustable gap ( 38 ) through which the substrate ( 14 ; 24 ) is guided horizontally, on its front and back simultaneously the printing medium on the substrate ( 14 ; 24 ) is printed, on both sides register exactly on the substrate by curing and etching or applying electrically conductive printing medium, the conductor structures arise. Method according to claim 1, characterized in that that the printing medium on the substrate, which is metal coated, is cured by radiation. Method according to claim 1, characterized in that that the direct imaging of conductor structures by means of a laser plotter is produced on a layer of a metal plate and that each of the two metal plates on the plate cylinder of each Printing unit is clamped. Method according to claim 1, characterized in that the substrates ( 14 ; 24 ) Are polyimide, polyethylene terephthalate-based plastic films or coated fuel papers.