Composite material for the production of printed circuit boards and manufacturing processes

Abstract

A composite material for the manufacture of printed circuit boards that has advantages in cost, weight and availability over the commonly used copper-clad laminate (CCL) comprises - a flat carrier having a first and a second side, at least the two sides being made of an electrically insulating material, - an aluminum foil bonded to one of the two sides of the carrier and - a solderable metallic coating containing copper or nickel or silver or gold with a maximum layer thickness of 25 µm, arranged on the side of the aluminium foil facing away from the carrier, which at least partially covers the aluminium foil. The invention also relates to a method for producing the composite material.

Description

The invention relates to a composite material for producing printed circuit boards and to a method for producing the same.A printed circuit board is a carrier for electronic components. It serves for mechanical fastening and electrical connection. Printed circuit boards consist of electrically insulating material for a flat carrier with conductive connections (conductor tracks) adhering to it. Suitable insulating materials are various materials, such as fiber-reinforced plastic, hard paper, epoxy resins, glass fibers, polytetrafluoroethylene and polyimide. The conductor tracks are usually etched from a thin layer of copper, usually 35 μm. The components are soldered onto pads ("pads") or in pads.The precursor for the production of printed circuit boards before the step of etching the conductor tracks is a composite material comprising the flat carrier made of electrically insulating material with at least one metal layer which is bonded to one of the two sides of the carrier.The precursor used in the production process of printed circuit boards is usually copper-coated laminate ("Copper-Clad Laminate"-CCL). A distinction is made between rigid and flexible copper-coated laminates. The copper layer enables the formation of conductor tracks, connection pads and vias.A via ("via") is a vertical electrical connection between the conductor track planes of a printed circuit board. The connection is usually carried out by an internally metallized passage through the carrier of the printed circuit board; it therefore presupposes a lamination of the carrier with a copper layer on both sides, which lamination overlaps at least in the region of the through-connection.The production of the one- or both-sided copper-coated laminates for circuit board production usually comprises the lamination of copper foil to the carrier under heat and pressure.For the production of plated-through holes, bores are first made in the carrier. When the bores on the inner walls are metallized, the plated-through holes are formed. The metallization of the bores requires a seeding, subsequent electroless deposition of a thin copper layer and finally its electrolytic reinforcement.The subsequent production of the conductor tracks of a single-sided or multi-sided printed circuit board is generally effected photolithographically by applying a thin layer of photosensitive photoresist to the surface of the still completely copper-coated laminate. After the photoresist has been exposed through a mask having the desired layout of the conductor tracks, either the exposed or the unexposed portions of the resist are soluble in a developer solution and are removed, depending on the photoresist used. If the printed circuit board thus pretreated is placed in a suitable etching solution, for example iron(III) chloride or sodium persulfate dissolved in water, only the exposed part of the metallized surface is attacked; the portions covered by the photoresist are retained because the lacquer is resistant to the etching solution.To protect the conductor tracks, solder resist can then be applied, which covers the conductor tracks and leaves only the soldering surfaces free.If SMD components are to be soldered on, solder paste is applied to the connection areas by means of a solder paste mask. In addition, the SMD components can be fixed by applying adhesive spots until soldering.US 20230054257 A1 discloses copper-coated laminate as composite material, which comprises a carrier made of insulating material. The substrate contains a resin composition having a specific polymer to produce a circuit board having a high signal transmission speed and heat capacity from the composite material.Proceeding from this prior art, the object of the invention is to propose a composite material for producing printed circuit boards, which composite material has advantages in terms of cost, weight and availability compared with the commonly used copper-coated laminate (CCL). A method for producing the same is also to be proposed.This object is achieved by a composite material having the features of independent claim 1 and a method for producing the same having the features of independent claim 16.The composite material for producing printed circuit boards comprises a planar carrier having a first and a second side, wherein at least the two sides consist of an electrically insulating material.The planar carrier can be rigid or flexible, depending on the requirements of the printed circuit board to be produced. The planar rigid carrier can consist in particular of the materials FR4, CEM1, CEM3 or PTFE:• FR4 denotes a class of flame-retardant composite materials consisting of epoxy resin and glass fibre fabric.• CEM materials are a cost-effective alternative, which are to be located qualitatively below the FR4 materials, since these materials do not consist entirely of a glass fibre fabric. CEM-1 has a core of epoxy impregnated paper with one outer layer of fiberglass fabric. CEM-3 has a core of glass fiber impregnated with epoxy resin and also a glass fiber fabric outer layer.• Polytetrafluoroethylene (abbreviated to PTFE) is an unbranched, linearly constructed, partially crystalline polymer made of fluorine and carbon. PTFE circuit boards are used in high frequency and / or high temperature applications. PTFE circuit boards have very good mechanical, thermal and electrical properties.For high-performance electronic circuits with high heat development, the planar, rigid carrier can have a metal core between the two sides of said metal core made of an electrically insulating material. The carrier can be designed, for example, as an IMS carrier with an aluminum core (IMS abbreviation: "Insulated Metal Substrate"), wherein the aluminum core distributes the punctiform heat at so-called "hot spots" over the entire printed circuit board. A build-up of heat at the components of the populated circuit board is avoided.Finally, the planar rigid carrier can consist of ceramic materials, such as aluminum oxide and aluminum nitride, under very high expected thermal load on the printed circuit board to be produced.The rigid support preferably has a thickness of 0.5-2 mm.A flat flexible carrier can be designed in particular as a film which preferably consists of polyimide (abbreviation PI), polyethylene terephthalate (abbreviation PET), polycarbonate (abbreviation PC) or polypropylene (abbreviation PP).The flexible support preferably has a thickness of 10-200 μm.According to the invention, an aluminum foil is bonded to at least one of the two sides of the carrier in order to produce a single-layer printed circuit board. To produce double-sided printed circuit boards which can be fitted on both sides, both sides of the carrier are connected to an aluminum foil in each case by a material bond. The cohesive connection is effected by lamination, wherein the term comprises both cohesive thermal joining of the aluminum foil to the carrier exclusively by pressure and temperature and also the connection of the aluminum foil to the carrier by means of an adhesive. Each aluminium foil covers one of the two sides of the support at least partially, but preferably completely.Each aluminum foil has a thickness of 1 μm-500 μm, preferably a thickness of 50 μm-55 μm. The preferred thickness of 50 μm-55 μm corresponds in terms of electrical conductivity to the standard of a 35 μm thick copper layer of a copper-coated laminate according to the prior art.The aluminum foils for forming the conductor tracks preferably consist of aluminum alloys of groups 1xxx and 8xxx. Preferred Group 1xxx aluminum alloys are the 1100, 1200, 1235 aluminum alloy. Preferred Group 8xxx aluminum alloys are the 8011 and 8089 type aluminum alloys. However, aluminum alloys of groups 3XXX and 6XXX are also suitable for the formation of the conductor tracks. In the context of the invention, the term "aluminum foil" includes foils of pure aluminum (group 1xxx) with at least 99% aluminum and foils of aluminum alloys of the further groups with other alloying elements.In order to improve adhesion to the surface of the support, each aluminum foil may have a roughened surface on the side facing the support.According to the invention, a solderable metallic coating containing copper or nickel or silver or gold is applied to the side of each aluminum foil facing away from the carrier with a maximum layer thickness of 25 μm, preferably of a maximum of 10 μm, which at least partially covers the aluminum foil. The metallic coating contains the metals copper or nickel or silver or gold as the main constituent, i.e. the aforementioned metals make up at least 90 percent by weight of the mass of the alloy for forming the metallic coating. The metallic coating can, however, also consist entirely of the aforementioned metals.The printed circuit board to be produced from the composite material must have a solderable, metallic surface at least on the connection surfaces. For this reason, each aluminum foil has the metallic coating on the side facing away from the carrier.A copper- or nickel-containing metallic coating offers a solderable surface with a good adhesion for soldered connections to electrical components or SMD components. Metallic coatings of gold or silver are also suitable for producing the solderable metallic surfaces.The exclusively one-sided metallic coating of each aluminum foil on the side facing away from the carrier is necessary because a metallic coating which would be arranged directly on the carrier material could not be removed in a subsequent etching process for producing the conductor track structure of the printed circuit board and short circuits would thus arise between the conductor tracks.For the deposition of nickel on the aluminum foil, for example, the zincate method is suitable. The "Notice O8-2nd Edition, Electroplating and Chemical Coatings, Overall Dressing of the Aluminum Industry, e.g., Va." describes the zincate process for metal coating of aluminum. The surface pretreatment required for the metal coating of aluminum comprises several steps, namely cleaning and degreasing, pickling and activation. The cleaning serves to remove debris and grease from the surface of the aluminum workpiece. The subsequent alkaline pickling removes the oxide layer of the aluminum. Subsequent pickling with acid solution removes undissolved heavy metal particles present as alloying constituent from the surface of the workpiece. Subsequent activation by zincate treatment prevents surface oxidation again. For this purpose, the surface is rinsed with a zincate mordant at least once. Zinc precipitates from the solution.The metallic coating can also be deposited on one side of the aluminum foil by means of an atmospheric plasma process.The metallic coating can furthermore be applied by physical vapor deposition (PVD) or by rolling on a thin metal foil, wherein the rolled-on metal foil mechanically meshes with the aluminum foil located underneath.When the metallic coating of the aluminum foil is carried out chemically or electrochemically in a dip bath, it is necessary to provide one side of the aluminum foil with a releasable protective film before the coating of the aluminum foil, which protective film is again released before the step of laminating the coated aluminum foil with the support.The single-sided solderable metallic coating on the side of the aluminum foil facing away from the carrier has, according to the invention, a maximum layer thickness of 25 μm, preferably of a maximum of 10 μm. This limitation of the maximum layer thickness ensures that the metallic coating is also removed during the subsequent etching process of the aluminum foil for forming the conductor track structure, if necessary. With a greater layer thickness, the etchant could no longer remove the solderable metallic coating and short circuits could arise. The solderable metallic coating preferably has a thickness of 1 μm-5 μm, particularly preferably a thickness of 2 μm-3 μm.In one embodiment of the invention, a barrier layer having a maximum layer thickness of 1 μm is arranged between the solderable metallic coating and the aluminum foil in order to avoid electrocorrosion between the adjoining metallic layers. The barrier layer contains nickel, palladium or zinc and is applied to the surface of the aluminum foil.For the production of printed circuit boards on both sides with plated-through holes, it is necessary for the metallic coatings of the aluminum foils to overlap at least in regions on both sides of the carrier. This prerequisite is always fulfilled in the preferred production method of the composite material with complete metallic coating of the aluminum foil on both sides of the carrier. The vias connect the overlapping regions of the metallic coatings on the top and bottom sides of the composite material in order to electrically connect the conductor track planes located on both sides of the printed circuit board to be produced to one another.In order to produce a through-connection, it is necessary for the composite material to have passages between the overlapping regions for forming the through-connections. The passages are introduced into the carrier in a direction perpendicular to the surface of the carrier, in particular by way of a bore, and the metal-coated aluminum layers on both sides of the carrier.In order to metallize the passages selectively by electrodeposition only on the inner walls of the passages, in particular with copper, but to prevent a further increase in the layer thickness of the metallic coating already applied beforehand on the two aluminum foils of the composite material for producing a two-sided printed circuit board, the aluminum foils including the metallic coatings are each provided on both sides of the carrier with a removable masking in order to effect the selective metallization of the passages by electrodeposition exclusively in the passages of the composite material. The removable masking can be, for example, a lacquer, in particular a photoresist or a plastic film, which is not attacked during metallization by means of electrodeposition.In an advantageous embodiment of the invention, it is provided that the masking surrounds the passage annularly at a distance from the edge of the passage, so that the metallization is deposited not only on the inner wall of the passage but also on the annular region surrounding the passage on the surface of the metallic coating. The annular region has, for example, a constant width of 20-100 μm. The annular, non-masked region improves the electrical connection of the through-connection to the metallic coating on both sides of the carrier. The metallization of the passages preferably has a thickness of up to 25 μm.In order to improve the adhesion of the metallization in the vias, the vias can be provided with an adhesion promoter before metallization. Palladium can be used as the adhesion promoter because it has high affinity for plastics and has good adhesion properties. The seeding of the passages with palladium can be carried out by chemical deposition, electrodeposition or plasma coating. Alternatively, carbon inks are suitable as adhesion promoters. Typically, carbon ink contains between 3 and 5 wt% suspended carbon particles in the range of 10 nm to 1000 nm.The invention is explained in more detail below with reference to the figures. They show FIG. 1 shows a composite material according to the invention for producing a single-sided printed circuit board, FIG. 2 shows a composite material for producing a circuit board on both sides, FIGS. 3 a) to g) show the introduction of a through-connection into a composite material for a circuit board on both sides, FIGS. 4 a), 4 b) show the composite material with FIGS. 3 a), b) in plan view, FIG. 5 a) shows a schematic illustration of the production of a single-sided printed circuit board from the composite material according to the invention, FIG. 6 shows a schematic illustration of the production of a single-sided printed circuit board from a faulty composite material with a solderable metallic coating that is too thick.FIG. 1 shows a section through a composite material 1 according to the invention for producing a one-sided printed circuit board comprising a planar carrier 2 which, in the exemplary embodiment shown, consists as a rigid carrier of one of the conventional electrically insulating materials, such as FR4, CEM1 or CEM3, for example.The planar carrier 2 has two parallel, planar sides 2.1, 2.2, wherein the first side 2.1 in the image is integrally bonded over its entire surface to an aluminum foil 3. The cohesive connection is effected by lamination, wherein the lamination comprises both cohesive thermal joining of the aluminum foil 3 to the carrier 2 exclusively under pressure and temperature and also the connection of the aluminum foil 3 to the carrier 2 by means of an adhesive.On the side of the aluminum foil 3 facing away from the carrier 2, i.e. in the figure on the top side thereof, a solderable metallic coating 4 is arranged. In the exemplary embodiment shown, the solderable metallic coating 4 covers the aluminum foil 3 over the entire surface. In principle, however, it is also conceivable for the solderable metallic coating 4 to only partially cover the aluminum foil 3 in the regions in which the printed circuit board to be produced has connection surfaces for components and / or wirings.The aluminum foil 3 has a preferred thickness of about 50 μm to 55 μm. This thickness corresponds in terms of electrical conductivity to the standard of a 35 μm thick copper layer of a copper-coated laminate for producing a printed circuit board.The solderable metallic coating 4 contains copper, nickel, silver or gold as the main constituent and is designed in a maximum layer thickness of 25 μm, preferably 10 μm. The limitation of the maximum layer thickness of the solderable metallic coating 4 ensures that the metallic coating is also removed during the subsequent etching process of the aluminum foil 3 for producing the conductor track structure, if necessary, as will be explained in more detail below with reference to FIGS. 5 a), 5 b) and 6.In the exemplary embodiment shown in FIG. 1, a barrier layer 5 is arranged between the solderable metallic coating 4 and the aluminum foil 3 in order to avoid electrocorrosion between adjacent metallic layers. The barrier layer 5 contains nickel, palladium or zinc and is applied to the surface of the aluminum layer 3 facing upward in FIG. 1.FIG. 2 shows a composite material 6 for producing a two-sided printed circuit board. If the composite material 6 has matching plies / layers, the same reference numerals are used as for the composite material 1 according to FIG. 1. In the case of the composite material 6 for producing double-sided printed circuit boards, which can be equipped with electronic / electrical components on both sides, both sides 2.1, 2.2 of the carrier 2 are each connected to an aluminum foil 3 in a materially bonded manner. The material-to-material connection takes place in the same way as in the case of the composite material 1. the solderable metallic coatings 4 of the aluminum foils 3 on both sides 2.1, 2.2 of the carrier 2 overlap completely on both sides of the carrier 2. Between the solderable metallic coating 4 and the aluminum foil 3, a barrier layer 5 is arranged on each of the two sides 2.1, 2.2 of the carrier 2.The thickness of the aluminum foils 3 and of the solderable metallic coatings 4 corresponds in thickness to the corresponding layers / plies of the composite material 1.FIG. 3 illustrates the process of introducing a through-connection 7 into a composite material 8; FIG. 3 a) shows as starting point a composite material 8 for producing a two-sided printed circuit board, which corresponds in terms of its structure to the composite material 6 according to FIG. 2, but has no barrier layer 5 on both sides 2.1, 2.2 of the carrier 2 between the solderable metallic coating 4 and the aluminum foil 3. The solderable metallic coatings 4 and the aluminum foils 3 on both sides of the carrier 2 completely overlap. The through-connection 7 to be introduced connects the overlapping regions of the metallic coatings 4 on the upper side and underside of the composite material 8, in order to electrically connect the conductor track planes located on both sides of the printed circuit board to be produced to one another.In order to produce a through-connection 7, it is necessary for a passage 9 to be introduced into the composite material 8, in particular by way of a bore 10, as is illustrated in FIG. 3 b). The passage 9 passes through the carrier 2 and the aluminum layers 3 on both sides 2.1, 2.2 of the carrier 2, each of which is provided with the solderable metallic coating 4.In order to metallize the passage 9 selectively with copper only on the inner walls of the passage 9 by means of the electroplating process, but to prevent a further increase in the layer thickness of the solderable metallic coating 4 already applied beforehand on the two aluminum foils 3 of the composite material 8, the two aluminum foils 3 including the solderable metallic coating 4 are each provided on both sides of the carrier 2 with a removable masking 11, for example in the form of a removable plastic film.A power source 12 is connected to the solderable metallic coating 4 on both sides of the carrier 2 of the masked composite material 8 in order to deposit copper electrochemically on the inner wall of the passage 9. The metallic deposits of the copper form a metallization 13 exclusively in the passage 9, as can be seen in FIG. 3 c ). The metallization 13 is electrically conductively connected to the aluminum foil 3 and to the conductive metallic coating 4 deposited thereon on both sides 2.1, 2.2 of the carrier 2.After the electrodeposition of the copper in the passage 9 and thus the production of the through-connection 7, the masking 11 is detached. FIG. 3 d ) shows the composite material 8 with a through-via 7 after the detachment of the masking 11.FIG. 4 a) shows the composite material 8 corresponding to FIG. 3 a) in a plan view of the masking 11, while FIG. 4 b) shows a plan view of the masking 11 of the composite material 8 after the bores for the passages 9 have been made.FIGS. 3 e), 3 f) and 3 g) show a composite material 8 for producing a circuit board on both sides, wherein for the sake of clarity the metallic coating 4 is only shown on one side of the carrier 2.The masking 11 surrounds each passage 9 annularly at a small distance from the circumferential edge 19 of the passage 9, which masking can be applied in the form of a PET film or photolithographically before the passages 9 are introduced.The annular, non-masked region 18 of the metallic coating 4 surrounding each passage has the effect that the metallization 13 is deposited selectively not only on the inner wall of the passage 9 but also on the annular region 18 on the surface of the metallic coating 4, as is illustrated in FIGS. 3 f) and 3 g). FIG. 3 f) shows the composite material 8 with the plated-through hole 7 after the detachment of the masking 11.FIG. 5 a),b) illustrates the production of a single-sided printed circuit board from a composite material 1. the production of the conductor tracks 16 including the connection areas is effected photolithographically in that a photomask 14 is placed on the surface of the composite material 1, i.e. the solderable metallic coating 4. As can be seen from FIG. 5 a), the carrier 2 is completely covered with the aluminum foil 3 and the solderable metallic coating 4. The composite material 1 provided with the photomask 14 is introduced into a suitable etching solution 15, for example iron(III) chloride dissolved in water, and attacks the part of the solderable metallized coating 4 exposed through the mask 14 and then of the aluminum foil 3 and completely removes these two layers, as can be seen in FIG. 5 b). The two conductor tracks 16 remain on the carrier 2, the solderable metallic coatings 4 of which are electrically separated from one another.By limiting the maximum layer thickness of the solderable metallic coating 4, it is ensured that the metallic coating 4 is also removed during the etching process of the aluminum foil 3 for forming the conductor tracks 16, if necessary.FIG. 6, however, shows the case that the maximum layer thickness of the solderable metallic coating 4 limited according to the invention has been exceeded by 25 μm. It can be seen that the etching solution could not sufficiently remove either the metallic coating 4 or the aluminum foil 3. The webs 17 of the aluminum foil 3 that are not removed lead to a short circuit between the conductor tracks 16 to be produced.List of reference characters1 Composite material (for producing a one-sided printed circuit board) 2 Carrier 2.1 First side 2.2 Second side 3 Aluminum foil 4 Solderable metallic coating 5 Barrier layer 6 Composite material (for producing a two-sided printed circuit board) 7 Through-connection 8 Composite material (for producing a two-sided printed circuit board) 9 Passage 10 Bore 11 Masking 12 Current source 13 Metallization 14 Photomask 15 Etching solution 16 Conductor tracks 17 Webs 18 Annular region 19 Circumferential edgeReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 20230054257 A1

[0011]

Claims

Composite material (1, 6, 8) for producing printed circuit boards, comprising - a planar carrier (2) having a first and a second side (2.1, 2.2), wherein at least the two sides (2.1, 2.2) consist of an electrical insulating material, - an aluminium foil (3) which is bonded to one of the two sides (2.1, 2.2) of the carrier (2), - a solderable metallic coating (4) which is arranged on the side of the aluminium foil (3) facing away from the carrier (2) and contains copper or nickel or silver or gold having a maximum layer thickness of 25 μm and at least partially covers the aluminium foil (3).Composite material according to Claim 1, characterized in that both sides (2.1, 2.2) of the carrier (2) are connected in a materially integral manner to in each case one aluminium foil (3).Composite material according to claim 1 or 2, characterised in that each aluminium foil (3) at least partially covers one of the two sides (2.1, 2.2) of the support (2).Composite material according to Claims 2 and 3, characterized in that the metallic coatings (4) of the aluminium foils (3) overlap on both sides (2.1, 2.2) of the carrier (2) at least in regions.Composite material according to Claim 4, characterized in that passages (9) for forming plated-through holes (7) between the metallic coatings (4) are arranged between the overlapping regions.Composite material according to claim 5, characterised in that the aluminium foils (3) including the metallic coatings (4) are each provided on both sides (2.1, 2.2) of the support (2) with a removable masking (11), adapted to allow selective metallisation (13) of the passages (9).Composite material according to claim 6, characterised in that the masking (11) surrounds each passage (9) annularly at a distance from the edge (19) of the passage (9) in such a way that the metallisation is deposited selectively not only on the inner wall of the passage (9) but also in an annular region (18) surrounding the passage on the surface of the metallic coating (4) on both sides (2.1, 2.2) of the carrier (2).Composite material according to one of Claims 5 to 7, characterized in that the passages (9) are coated with a nucleating agent.Composite material according to one of Claims 1 to 8, characterized in that the solderable metallic coating (4) of each aluminium foil (3) contains copper or nickel or silver or gold as main constituent, which makes up at least 90% by weight of the mass of the metallic coating.Composite material according to one of Claims 1 to 9, characterized in that a barrier layer (5) is arranged between the solderable metallic coating (4) and the aluminium foil (3).Composite material according to one of Claims 1 to 10, characterized in that each solderable metallic coating (4) has a thickness of 1 μm - 5 μm.Composite material according to one of claims 1 to 11, characterised in that each aluminium foil (3) has a thickness of 1 μm - 500 μm, preferably a thickness of 50 μm - 55 μm.Composite material according to any one of claims 1 to 12, characterised in that each aluminium foil consists of an aluminium alloy of the following groups: 1XXX, 3XXX, 6XXX, 8XXX.Composite material according to one of Claims 1 to 13, characterized in that the planar carrier (2) is rigid and consists of FR4, CEM1, CEM3 or PTFE.Composite material according to one of Claims 1 to 13, characterized in that the planar carrier (2) is rigid and a metal core is arranged between the two sides (2.1, 2.2) of said planar carrier made of an electrical insulating material.Composite material according to one of Claims 1 to 13, characterized in that the planar carrier (2) is flexible and consists of a film of PI, PET, PC or PP.Method for producing a composite material (1) according to claim 1, characterised bythe following steps: - providing a flat carrier (2) with a first and a second side (2.1, 2.2), wherein at least the two sides (2.1, 2.2) consist of an electrical insulating material, - one-sided coating of only one side of the aluminium foil (3) with a solderable metallic coating (4) containing copper or nickel or silver or gold with a maximum layer thickness of 25 μm, which at least partially covers the aluminium foil (3), - laminating the aluminium foil (3) to one of the two sides (2.1, 2.2) of the carrier (2) for producing a cohesive connection between the carrier (2) and the aluminium foil (3), wherein the metallic coating (4) is located on the side of the aluminium foil (3) facing away from the carrier (2).Method for producing a composite material according to claim 17, characterised bythe further steps - covering one side of the aluminium foil (3) with a removable protective film before the one-sided coating, wherein the one-sided coating takes place chemically or electrochemically in a dip bath exclusively on the other side of the aluminium foil with the solderable metallic coating (4), - removing the protective film from the aluminium foil (3) after the step of one-sided coating and before the step of laminating.Method for producing a composite material according to Claim 17 or 18, characterized in that - an aluminium foil (3) is laminated in each case on both sides (2.1, 2.2) of the carrier (2), wherein the metallic coatings (4) of the two aluminium foils (3) overlap on both sides (2.1, 2.2) of the carrier (2) at least in regions, - the aluminium foils (3) including the metallic coatings (4) are masked in each case on both sides (2.1, 2.2) of the carrier (2) in such a way that the masking (11) can be removed again, - passages (9) for forming plated-through holes (7) between the overlapping regions of the metallic coatings (4) are introduced into the composite material (8), and - after the masking and introduction of the passages (9), the passages of the composite material are metallized.Method for producing a composite material according to Claim 19, characterized in that, before the metalizing step, the passages (9) are coated with a nucleating agent.Method for producing a composite material according to Claim 19 or 20, characterized in that copper is electrodeposited in the passages (9) for metallization.Method for producing a composite material according to one of Claims 19 to 21, characterized in that - the aluminium foils (3) including the metallic coatings (4) on both sides (2.1, 2.2) of the carrier (2) are each masked in such a way that the masking (11) surrounds each passage (9) annularly at a distance from the edge (19) of the passage (9), and - after masking and introducing the passages (9), the passages and the regions (18) surrounding each passage (9) are metallized on the surface of the metallic coating (4) on both sides (2.1, 2.2) of the carrier (2).

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