WO2001050826A1

WO2001050826A1 - Method and device for producing a conductive structure on a substrate

Info

Publication number: WO2001050826A1
Application number: PCT/EP2000/013335
Authority: WO
Inventors: Carsten Nieland; Christine Kallmayer; Ralf Miessner; Rolf Aschenbrenner; Andreas Ostmann
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1999-12-30
Filing date: 2000-12-29
Publication date: 2001-07-12
Also published as: DE19963850A1

Abstract

The invention relates to a method and to a device for producing a conductive structure (8) on a substrate (10) by means of a transfer/transmission method. According to the inventive method, first a metal layer is chemically or electrochemically deposited on a structured metal layer (6) in a selective manner so as to produce a conductive structure, said structured metal layer being provided on a reusable support (2). The conductive structure (8) produced is transferred to the substrate (10) and the reusable support (2) is separated from the substrate (10).

Description

Method and device for producing a conductive structure on a substrate

description

The present invention relates to methods and devices for producing conductive structures on a substrate or on a circuit carrier.

There are currently different methods for producing conductor tracks, which in principle have two basic steps, namely the application of a conductive material to a substrate and the structuring thereof. These two basic steps can also be combined in one step, which is the case, for example, in the production of conductor tracks by screen printing using conductive filled polymer pastes.

When manufacturing conductor tracks from pure metals, for example copper (Cu) or aluminum (Al), as well as metal alloys, two steps are predominantly required. First, the metal is applied to the entire surface of the substrate material. Mechanical processes, for example the rolling of metal foils, chemical or electrochemical deposition processes or vapor deposition, for example sputtering, PVD, CVD (PVD = Physical Vaper Deposition; CVD = Chemical Vaper Deposition) are used. The structuring then takes place in a second step by means of mechanical methods, for example by milling, or by a combination of photolithographic processes and etching methods. The latter two methods are often the cost determining factors in PCB manufacturing. These cost-intensive steps have to be applied to the structuring of each individual substrate. In the known method described, cost reductions are therefore only possible by combining several substrates for one benefit, since here all le substrates of benefit go through a process step simultaneously.

After the structuring of the metallization, the conductor tracks are reinforced via chemical or electrochemical processes or provided with additional functional layers, for example made of nickel or gold.

The above-described metal conductor formation on substrates, i.e. Circuit breaker, has decisive disadvantages. First, all substrates have to go through the corresponding process steps described. However, this means that the substrate materials must be suitable for the processes mentioned, or alternatively the processes must be matched to the materials. Correspondingly inexpensive materials, such as are used, for example, for the production of smart card or label inlets, can only be produced in a comparatively complex manner using pure metal conductor tracks or alloys or layer structures. Furthermore, the high costs for lithography during structuring are incurred for each substrate or substrate benefit, so that the cost share of this process in the finished substrate is very high.

Filled polymer pastes are often used to produce conductor tracks in the production of smart card or label inlets. However, it should be noted here that the printing of polymer conductor tracks is usually unsuitable for producing very fine structures with a conductor path spacing of approximately 100 μm. Rather, structuring of metal layers on the substrate carrier by means of photolithography and subsequent etching process is necessary. This can result in increased tolerances for the conductor track geometry, in particular when producing conductor tracks on flexible circuit carriers, which can only be processed in small uses or from roll to roll.

In addition to the above methods, direct Generation of metal conductor tracks on the substrate by hot stamping. In this case, the conductor structure is punched out of a metal foil with the aid of a punching tool and, at the same time, the substrate is also transferred by means of pressure and temperature, or partially pressed into the substrate material. This method, as it is used in so-called "MIDs" (Molded Interconnect Devices), is severely restricted mainly with regard to the substrate materials that can be used and the smallest structure sizes that can be produced.

The object of the present invention is to provide an inexpensive method for producing a conductive structure on a substrate, which also enables the production of very fine, highly precise structures, and also devices which can be used in such a method.

This object is achieved by a method according to claim 1 or claim 4 and devices according to claims 9 and 11.

A first exemplary embodiment of a reusable tool carrier which can be used according to the invention comprises a carrier element and a primary metallization which is formed on the carrier element and which is structured depending on the conductive structure to be produced, on which the conductive structure can be selectively deposited. A second exemplary embodiment of a reusable tool carrier has a primary metallization and a cover layer which is formed on the primary metallization and, depending on the conductive structure to be produced, has recesses up to the primary metallization. Finally, a third exemplary embodiment of a reusable tool carrier for producing a conductive structure comprises recesses which are formed depending on the conductive structure to be produced, into which paste-like or liquid material can be introduced and can be converted into a solid state, in order thereby to produce the conductive structure. The present invention thus creates a method which is composed of two basic processes. The first basic process is the production of a conductive structure, preferably a structured metallization layer, using a reusable tool. The second basic process is then the transfer of this generated conductive structure to a substrate, preferably a circuit carrier.

In contrast to the usual manufacturing processes for structured circuits described above, the structuring process of the metallization, which is to be the later conductor track, does not take place directly on the substrate, but in a separate step. This means that the substrate does not come into contact with the required structuring processes. In contrast to conventional methods, the metallization layer is not first applied to the substrate and then structured, nor is the metallization layer produced in a structuring process on the substrate, as is the case, for example, when producing conductor tracks from filled polymer pastes by means of screen printing or when hot stamping metal foils ,

Rather, according to the invention, the conductive structure is produced on a reusable tool carrier, the same being transferred to the substrate only after completion. This is possible according to the invention, since it has been found that conductive structures can be produced in a removable manner on reusable tool carriers. This is possible, for example, if a metallization layer is deposited chemically or electrochemically on a primary metallization. It has been shown that this peelability occurs with a large number of materials, for example stainless steel, titanium, tungsten, vanadium, palladium, chromium or alloys thereof can preferably be used as the primary metallization. The conductive structure can then be produced from copper, aluminum or gold, for example become. Excellent removability has been shown in a preferred exemplary embodiment when using a TiW layer as the primary metallization and the chemical deposition of copper as the conductive structure thereon.

When the generated conductive structure is transferred from the reusable tool carrier to the substrate or an intermediate carrier, sufficient adhesion of the conductive structure to the substrate or the intermediate carrier must be ensured. For this purpose, an adhesive layer can be provided on the substrate or the intermediate carrier. Alternatively, it is possible to at least partially press the conductive structure into the substrate material.

After the conductive structure has been detached, the reusable tool carrier is again available for reapplication or introduction of a material for producing a conductive structure, as long as it is not damaged by wear. With the conductor track layout remaining the same, a new structuring of the carrier is not necessary. The reusable tool holder is therefore a so-called multiple tool.

The method of producing the conductive structures or conductor tracks independently of the substrate on an external carrier, ie the reusable tool carrier, and the subsequent transmission method have decisive advantages over conventional methods for producing conductor tracks on substrates. The tool carrier can be reused for several process runs, depending on the wear. This reusability of the carrier saves costs and environmental pollution due to the structuring processes, ie lithography and etching processes, which are eliminated in comparison with conventional methods. According to the invention, the substrates to which the conductive structure is to be applied come with the structuring process not in contact, so that a reduced load on the substrates takes place. Furthermore, according to the invention, the structuring or the minimal structure widths and spacings that can be generated are independent of the substrate to which the corresponding conductive structure is to be applied.

Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

1 schematically shows the steps of a preferred method for producing a conductive structure on a substrate according to the present invention; and

Fig. 2 shows schematically the steps of a method for producing a preferred embodiment of a reusable tool holder according to the invention.

In the following, a preferred exemplary embodiment of a method according to the invention for producing a conductor track metallization on a substrate is first explained in more detail with reference to FIG. 1. The method according to the invention can advantageously produce, for example, coil metallizations on ticking foils for labels or contactless chip cards. After the coil metallizations have been produced by the method according to the invention, the foils can then still be provided with corresponding components, e.g. a transponder C, and then laminated.

As shown in FIG. 1 in a step S1, a reusable tool carrier 2 is first provided, which in the exemplary embodiment shown has a carrier element 4 and a primary metallization 6 formed on the carrier element 4. The primary metallization 6 is structured depending on the conductive structure to be produced, so that the conductive structure can be selectively deposited thereon. A method of manufacturing such a reusable tool carrier as shown in FIG. 1 will be explained later with reference to FIG. 2. The carrier element 4 can be formed, for example, by a silicon wafer, a ceramic, a metal plate or a rigid or flexible carrier made of plastic. In the preferred exemplary embodiment of the present invention, the structured primary metallization 6 is formed from titanium-tungsten.

In the exemplary embodiment shown, the conductor metallization 8 is now produced on the primary metallization 6 by selective metal deposition being carried out in a chemical or electrochemical process. At this point it should be noted that the metallization of the reusable tool carrier, referred to herein as the primary metallization, is subject to the requirement that in a chemical or electrochemical process the metallizations can be deposited on it, which later the conductor track on the substrate carrier, i.e. the trace metallization. However, the adhesion of these metallizations to be deposited on the primary metallization must be sufficiently low to enable the conductor metallization to be removed later. Furthermore, the deposition of the metallization must take place selectively on the primary metallization, wherein deposition on the carrier element 4 must be prevented. In a preferred exemplary embodiment of the present invention, the interconnect metallization 8 is produced by chemically depositing a copper layer on the structured titanium-tungsten primary metallization.

The tool carrier 2 on which the conductor metallization 8 is produced is shown at S2 in FIG. 1. This interconnect metallization 8 is now transferred to the actual substrate 10, which is shown at S3 in FIG. 1. For this purpose, in the exemplary embodiment shown, an adhesive layer 12, preferably an adhesive layer, is provided on a lower surface of the substrate, that is to say the circuit carrier 10. As indicated by arrows 14, 16 and 18 in FIG. 1 the surface of the tool carrier 2 on which the conductor track metallization 8 is formed and the surface of the substrate 10 on which the adhesive layer 12 is formed are brought together, as shown at S4 in FIG. 1. Subsequently, as indicated by the arrows 20 and 22, the reusable tool carrier 2 and the substrate 10 are separated, as a result of which the interconnect metallization 8 is detached from the original metallization 6 due to the detachability thereof and due to the adhesive effect of the adhesive layer 12 the substrate 10 remains. Thus, after the method has been completed, the reusable tool carrier 2 is available for a new metal deposition, as shown at S5 in FIG. 1. On the other hand, as shown at S6 in FIG. 1, there is the substrate 10 provided with the conductor track metallization 8.

In the illustrated embodiment, the reusable tool carrier can be used in many ways as long as the primary metallization 6 is not damaged. The substrate shown at S6 in FIG. 1 can then be processed further, for example by applying a transponder IC over the schematically illustrated conductor ends 8 ′ and 8 ″ of the schematically illustrated coil metallization 8.

A method for producing the reusable tool carrier 2 shown in FIG. 1 is briefly discussed below with reference to FIG. 2. First, the carrier element 4 is provided in a step S10. As indicated above, this can be a silicon wafer, a ceramic, a metal plate or a rigid or flexible carrier made of plastic. A primary metallization 30 is then applied to the entire surface of this carrier element 4 in a step S12. The preferred exemplary embodiment of the present invention is titanium tungsten. Alternatively, however, other materials can be used, on which electrochemically or After germination, have other conductive materials deposited chemically, but which have a low adhesion to the primary metallization. For example, stainless steel, titanium, tungsten, vanadium, palladium, chromium or alloys thereof can be used as the primary metallization.

The application of the full-surface primary metallization 30 can be carried out in any conventional manner, for example the rolling on of metal foils, chemical or electrochemical deposition or vapor deposition processes, such as e.g. Sputtering, PVD and CVD.

Subsequently, in step S14, the original metallization 30 applied over the entire surface is structured using a photoresist 32 which is exposed via a mask 34, as is indicated schematically by the illustration of an incandescent lamp 36. After the exposure, a corresponding etching is carried out to complete the structuring, so that after the structuring step S14, the finished, reusable tool carrier 2, which has a carrier element 4 on which the structured primary metallization 6 is formed, is present.

In addition to the structuring described above by means of photolithography, the primary metallization layer 30 can also, for example, by mechanical methods such as Milling or evaporation using a laser can be structured. In any case, the structure remaining when the plan view of the carrier element is viewed from above is a mirrored image of the conductor track to be produced later on the substrate carrier.

At this point, it should be noted that the procedure described with reference to FIG. 2 merely represents an exemplary embodiment for producing the reusable tool carrier 2, alternatively other methods known from the prior art for applying a structured metallization for producing the original tallization 6 can be used on the support member 4.

In the method according to the invention described above with reference to FIG. 1, the interconnect metallization 8 was produced by means of selective deposition on a structured primary metallization 6. Alternatively, it is possible to produce the conductor track metallization using a reusable tool carrier which has a full-surface primary metallization which is covered by a covering layer which is formed thereon and, depending on the conductive structure to be produced, has recesses up to the primary metallization. In other words, a full-surface primary metallization is covered with a mask, or a structured cover layer is produced thereon. The part of the material of the primary metallization which does not belong to the conductor track structure to be produced is covered by this cover layer, while the openings of this cover layer which extend to the surface of the primary metallization represent the corresponding mirror image of the subsequent conductor track. In this case, the desired prevention of the deposition of the conductor metallization to be applied later in the areas in which no conductor structures are to be achieved is achieved by the mask above the primary metallization. The conductor path metallization then grows, starting from the surface of the primary metallization, only in the openings of the mask or cover layer. The cover layer can be produced, for example, by applying a photoresist, for example by spin coating, and subsequently photostructuring the same. In such a case, it is not necessary to provide a separate carrier element, rather the carrier element can be formed by the primary metallization itself. The above-mentioned materials are again suitable as the primary metallization material, stainless steel, for example, which is used for electrodeposition, being suitable if the external carrier is formed by the primary metallization itself. With the above described example of a reusable tool carrier, a coating of a separately manufactured carrier with a primary metallization is no longer necessary.

Again, alternatively, the reusable tool carrier can be a one-piece element in which, depending on the conductive structure to be produced, recesses are formed, into which paste-like or liquid material can be introduced and converted into a solid state, in order to thereby generate the conductive structure. The recesses formed correspond to a mirror image, i.e. a negative, the conductive structure to be produced. Here, the conductor track can be produced by using pastes or dispersed liquids which are conductive, at least in the solidified state. Examples of these are conductive polymer pastes. For this purpose, the corresponding conductor track shape is worked into the tool carrier, for example by mechanical methods, such as Milling, chemical processes, e.g. Etching, or electrochemical or other processes, such as e.g. Lasering or eroding. The paste or liquid is then introduced into this introduced form, for example by printing, pouring or dispensing. After the evaluation or solidification process, the conductor track is transferred to the actual substrate in the transfer process. Here, too, it is a prerequisite that the solidified conductor track can be detached from the tool carrier. For this purpose, the surface of the tool carrier is preferably provided with a material on which the conductor track adheres poorly. This material depends on the conductor paste or conductor liquid used. For example, Teflon (PTFE = Polytetraflurethylene) can be used advantageously, which is applied to the reusable tool holder after structuring. Alternatively, the entire carrier or at least parts thereof can be made of PTFE.

In the preferred exemplary embodiment of the method according to the invention described above with reference to FIG. 1 the surface of the substrate 10 to which the conductor track structure 8 was to be applied is provided with an adhesive layer 12. As a result, after the substrate has been brought into extensive contact with the tool carrier, the conductor path is detached from the tool carrier and adheres to the substrate due to the adhesive force of the adhesive layer of the substrate and the low adhesive strength of the conductor track metallization on the primary metallization. This removal can take place simultaneously over the entire surface, or step by step by unrolling or pulling off the substrate obliquely from the tool carrier. Alternatively, the adhesive layer can also be provided on the conductor track metallization still located on the tool carrier. However, the adhesive layer is preferably applied to the entire surface of the substrate. Alternatively, it is possible for the substrate to be provided with the adhesive layer selectively only on partial areas, for example the areas on which the conductor tracks come to lie. In any case, however, the adhesion between the substrate and the respective free surfaces on the tool carrier, on which there is no interconnect metallization, must be as low as possible so that only the interconnect metallizations are detached.

The required adhesive effect between the interconnect metallization and the determination substrate to which it is to be applied can also be generated in other ways. For example, when the substrate and external carrier come into contact with pressure and possibly simultaneous exposure to temperature, the conductor track can be at least partially pressed into the substrate material, so that the adhesion between the substrate and the conductor track metallization is produced in this way.

Although, according to the above description, the conductor track metallization has been applied directly from the tool carrier to the determination substrate, it is possible to use an intermediate carrier, so that a double transfer process, contrary to the single transfer process described above, process results. In any case, it is necessary that the adhesion between the primary metallization and the interconnect metallization is less than that between the interconnect metallization and the substrate to which the interconnect metallization is to be applied.

Claims

claims

1. A method for producing a conductive structure (8) on a substrate (10) by means of a transfer method by the following steps:

Performing selective chemical or electrochemical metal deposition on a structured metallic layer (6) formed on a reusable carrier (2) to form a conductive structure;

Transferring the generated conductive structure (8) to the substrate (10); and

Separating the reusable carrier (2) from the substrate (10).

2. The method of claim 1, wherein the structured metallic layer (6) consists of a material selected from the group containing stainless steel, titanium, tungsten, vanadium, palladium, chromium or alloys thereof.

3. The method of claim 1 or 2, wherein the conductive structure is formed from copper, aluminum or gold.

4. A method for producing a conductive structure (8) on a substrate (10) with the following steps:

Introducing a pasty or liquid material into recesses of a reusable carrier;

Converting the pasty or liquid material to a solid state to form a conductive structure; Transferring the generated conductive structure to the substrate; and

Separating the reusable carrier from the substrate.

5. The method according to claim 4, wherein at least the surface of the recesses of the reusable carrier are coated with Teflon.

6. The method according to any one of claims 1 to 5, wherein the conductive structure (8) is transferred to an intermediate carrier before transfer to the substrate (10).

7. The method according to any one of claims 1 to 6, wherein the substrate 10 or the intermediate carrier are provided with an adhesive (12) before the transfer step.

8. The method according to any one of claims 1 to 7, wherein the conductive structure is pressed into the substrate during transfer to the substrate.

9. Reusable carrier (2) for producing a conductive structure on a substrate according to the method according to any one of claims 1 to 3, characterized by

a carrier element (4); and

a structured metallic layer (6) which is formed on the carrier element (4) and which is structured depending on the conductive structure (8) to be produced, on which the conductive structure (8) can be selectively deposited.

10. A reusable support according to claim 9, wherein the metallic layer (6) is made of a material selected from the group consisting of stainless steel, titanium, tungsten, vanadium, palladium, chromium or alloys thereof.

11. Reusable carrier for producing a conductive structure on a substrate according to the method according to claim 4, characterized by

Recesses which are formed depending on the conductive structure to be produced, into which paste-like or liquid material can be introduced and can be converted into a solid state, in order to thereby form the conductive structure.

12. Reusable carrier according to claim 11, wherein at least the surfaces of the recesses are coated with Teflon.