METHOD AND DEVICE FOR MANUFACTURING ELECTRICAL COMPONENTS ON A FLEXIBLE SUPPORT

Description

[0001] The invention relates to a method for producing electrical or electronic components or circuits on a flexible, flat or three-dimensional carrier by applying a liquid or pasty starting material for a structured or unstructured electrical or electronic functional layer and subsequently drying, sintering and / or crosslinking the starting material on the carrier, as well as an arrangement for carrying out this method.

[0002] The production of functional layers, which includes sintering or cross-linking of an originally liquid or pasty starting material, on components of electrical devices, energy storage devices or in electronic components or assemblies has long been part of the state of the art.

[0003] With the dramatically increasing technical and economic importance of modern battery technologies on the one hand, and the equally rapid spread of printed electronic circuits of this type (so-called "printed electronics"), such processes are becoming increasingly important. The use of substrate materials that are as readily available and cost-effective as possible, as well as being as recyclable as possible, is becoming increasingly important, as is the process management adapted to these novel substrate materials with the highest possible yield of high-quality end products.

[0004] For example, in innovative battery designs, such as those required for electromobility and, in the future, for high-performance storage devices in the field of energy generation, polymer films based on PE, PVC, PET, or PP, or even paper, are used in addition to very thin metallic carrier foils. Furthermore, efforts are being made to use water-soluble coatings as widely as possible for environmental protection and occupational safety reasons. Similar configurations have been proposed for the electrodes of fuel cells, which could be used in fuel cell-powered vehicles in the future.

[0005] When drying or crosslinking coatings, the temperature sensitivity of the substrate material must be taken into account, while at the same time striving to achieve a high-quality coating (free of drying-related defects) with the highest possible throughput through a suitable drying system. It is understood that the production and operating costs of the drying systems also play a significant role in the cost of the final products – which should become increasingly lower with increasing mass use. Known tunnel kiln-type drying systems only meet these requirements to a very limited extent and are space-consuming and expensive to construct and operate. Such systems are known, for example, from WO2011 / 087362, US2016 / 074941, and DE10048361.

[0006] The invention is therefore based on the object of providing an improved method of the generic type and a corresponding arrangement which meet the above requirements.

[0007] This object is achieved by a method having the features of claim 1 and an arrangement having the features of claim 8. Appropriate developments of the inventive concept are the subject of the respective dependent claims.

[0008] The invention includes the idea of ​​providing the energy required for sintering and / or crosslinking the starting material on the support, which is not very thermally stable due to its thickness, but often also due to the material itself, in such a way that its effect is exerted essentially within the coating, while the overall thermal load on the support (over the duration of the drying process) remains as low as possible. For typical coating materials, particularly water-based ones, radiation in the near-infrared range has proven effective for this purpose, with a maximum amplitude in the wavelength range between 800 nm and 1,500 nm. This radiation is particularly effectively implemented in largely water-based (but also in many solvent-based) solutions, emulsions, and pastes.

[0009] Furthermore, the invention involves the idea of ​​applying this radiation at such a high energy density that the desired sintering and / or crosslinking in the coating can take place in such a short time that the amount of energy transferred to the substrate, and thus its overall thermal load, remains limited. Depending on the specific application, substrate, and coating, energy densities in the range between 50 kW / m² and 1,000 kW / m², particularly 120 kW / m² at 1,000 kW / m², appear suitable for the coating surface.

[0010] For many current applications, according to the inventors' findings, the exposure time to near-infrared radiation can be limited to between 1 and 3 seconds, particularly between 2 and 20 seconds. It is understood that the specific treatment time depends on the thickness and nature of the coating and the specific power density selected.

[0011] In applications that are currently considered particularly promising, the substrate is a temperature-sensitive substrate, such as a polymer film or paper, and the power density and exposure duration of the near-infrared radiation are adjusted such that the temperature does not rise above a critical temperature for the material, in particular not above a temperature in the range between 100°C and 200°C. The specific value of the limit temperature naturally depends on the material, and the setting of the appropriate energy density and throughput speed of the substrate through the drying system to comply with this limit value can be determined by a person skilled in the art using a limited number of simple tests.

[0012] The process in this form has potential for the further development of printed electronics, a promising field of application. Here, liquid starting material is selectively or selectively applied to the substrate using a printing process. This is achieved with particular precision, speed, and efficiency using an inkjet printing process. The power density and exposure duration of the near-infrared radiation are adjusted such that a temperature above a material-specific sintering or crosslinking temperature, particularly above a temperature in the range between 50 and 200°C, is briefly reached in the selective coating.

[0013] In another potentially significant application, a pasty starting material is applied to the substrate essentially over its entire surface, particularly by a roller or doctor blade application process, and then, if necessary, structured (e.g., by etching processes or using a laser). Here, too, the power density and exposure duration of the near-infrared radiation are adjusted such that a temperature above a material-specific sintering or crosslinking temperature is briefly reached in the selective coating. This design is likely to be particularly important in the production of battery electrodes for electromobility and energy technology, as well as fuel cell electrodes.

[0014] A specific proposed process in this area assumes that a polymer film with a thickness in the range between 75 µm and 200 µm or a metal foil in the range between 3 µm and 10 µm is used as the carrier, and a viscous water-based or organic solvent-based paste with an initial thickness in the range between 10 and 1,000 µm and a solids content in the range between 40% and 80% is used as the coating. Near-infrared radiation with a power density in the range between 50 and 200, particularly 70 and 150 kW / m², is used for drying, sintering, and / or crosslinking. In this application, which can be referred to as a "thick-film application," precise control of the radiation exposure is preferred, depending on the parameters of the carrier and the coating, as well as in terms of time.Timing control is of considerable importance for the quality of the final product and the yield of the process, particularly in the initial and final areas of an elongated flat carrier.

[0015] In another application, which can also be referred to as a "thin-film application" and is relevant, for example, for printed electronics, the coating has a thickness of only approximately 1 to 20 µm and is applied to the substrate, particularly by printing or spraying ("jet technology"). In this application, fixed NIR radiation power densities can be used, and these can exceed the values ​​mentioned above.

[0016] In further embodiments of the method according to the invention, the exposure to near-infrared radiation is carried out within an NIR irradiation zone with a predetermined profile of non-constant power density. In particular, the radiation density profile can be adjustable in response to the material properties of the carrier and / or the starting material.

[0017] Such process controls allow for the specific requirements of certain functional layers, as well as particularly temperature-sensitive substrates, to be addressed in a differentiated manner. In particular, they allow for preheating and temperature-holding phases to be set before and after a main drying phase with high power density.

[0018] Furthermore, a temperature maintenance zone can also be realized independently of the use of near infrared radiation in a downstream system component, in particular a hot air dryer.

[0019] In another potentially advantageous process, near-infrared radiation is applied from both surfaces of the substrate. This process appears particularly suitable for relatively temperature-stable substrates (e.g., metal foils). If it is also to be used for products with temperature-sensitive substrates, setting different power densities on the surface of the coating on the one hand and the surface (back) of the substrate on the other seems particularly useful.

[0020] In another special process, the application of near-infrared radiation is combined with the application of an air stream to at least one surface of the substrate. Such a warm air stream allows, in particular, evaporated liquid components of the coating to be easily and precisely removed (e.g., into suitable filters). At the same time, excessive heating of the substrate material can be prevented even when high power densities are required for a relatively long time. This may be necessary to sufficiently heat a relatively thick or material-specific coating.

[0021] Specifically, it can be provided that the supply of warm air in the irradiation zone and / or the supply of hot air in an optionally provided hot air dryer is provided on both surfaces of the carrier and is in particular adjustable.

[0022] Device aspects of the present invention largely follow from the method aspects explained above. Therefore, a repetition of the above explanations from a device perspective can largely be dispensed with.

[0023] According to the above, an arrangement according to the invention comprises at least conveying means for conveying the flexible planar carrier through the arrangement, coating means for coating the planar carrier with the starting material, in particular during the conveying of the carrier, and means for drying, sintering and / or crosslinking the starting material layer on the carrier, in particular during the conveying of the carrier, which include at least one radiation source for radiation in the near infrared range, the amplitude maximum of which is in the wavelength range between 800 nm and 1,500 nm and which is designed, configured or adjustable in such a way that its power density on the surface of the carrier is in the range between 50 kW / m 2< and 1,000 kW / m 2<.

[0024] In particular, the means for drying, sintering, and / or crosslinking include a plurality of NIR radiation sources that are arranged and / or controllable in an NIR irradiation zone such that a predetermined profile of non-constant power density can be generated within the irradiation zone. This can be configured, in particular, such that the NIR emitters have different spacings and different reflector geometries over the length of the irradiation zone and / or are placed at different distances above the surface of the coated carrier, or the radiation sources have different power levels.

[0025] The aforementioned profile of non-constant power density across the length of the irradiation zone can also be controllable, for example, by providing means for power control of some or all NIR radiation sources or mechanical adjustment means for variably adjusting the height of the radiation sources above the carrier. In this way, the irradiation zone, in particular, can be flexibly configured into a preheating zone and a main drying zone and / or a main drying zone and a temperature maintenance zone.

[0026] To realize the mentioned treatment temperature holding zone, a separate treatment section can also be provided in the drying arrangement, which is designed in particular as a hot air dryer or as a tunnel oven section.

[0027] Furthermore, means for supplying an air stream, in particular one or more fans with associated air guiding devices, can be assigned to the NIR irradiation zone. In a further embodiment, these can be configured so that the air stream, after passing over the surface of the coating, enters a filter device for filtering out harmful solvent components of the coating and / or a heat exchanger for energy recovery. A corresponding filter or heat exchanger device is then also part of the proposed arrangement.

[0028] Furthermore, it can be provided that the means for supplying an air flow and / or the treatment temperature holding zone comprise control means for controlling the air flow or the temperature in the treatment temperature holding zone. This enables control of the drying process in a manner that is particularly flexible and adaptable to different types of substrates and coatings, thus allowing the processing of different substrate-coating configurations for electrical or electronic applications in one and the same drying arrangement without complex structural modifications.

[0029] Advantages and usefulness of the invention will become apparent from the following description of exemplary embodiments and aspects, partly with reference to figures. They show: Fig. 1 is a schematic representation of an embodiment of the arrangement according to the invention in the form of a longitudinal section, Fig. 2 is a schematic representation of an embodiment of the NIR dryer 1A according to Fig. 1 , and Fig. 3 a schematic representation of a further embodiment of the NIR dryer of an arrangement according to the invention, together with further system components.

[0030] Fig. 1 shows the concept of a drying system 1 for functionally coated substrates 2, which, in their finished state, are intended to serve as battery or fuel cell electrodes. The substrate can be a quasi-endless aluminum or copper foil that has been coated in a coater (not shown here) using a doctor blade system or a slot die with a viscous water-based or organic solvent-based paste 2a with a typical solids content between 50% and 70%.

[0031] The thickness of the carrier film can range between 5 and 150 µm, and the wet layer thickness of the viscous paste can range between 10 and 1,000 µm. In the illustrated embodiment, the coating is applied to one side of the carrier, but battery components coated on both sides can also be produced in successive coating and drying phases. Instead of metal foils, polymer films (e.g., PET films) with significantly greater thickness (e.g., between 100 and 150 µm) can also be used as carriers.

[0032] For drying the aforementioned supports, the drying system 1 comprises an NIR dryer 1A with NIR radiators (not shown here) located on both sides of the support 2 and integrated warm air ventilation, symbolized by the arrows Vi and Vo. The NIR dryer 1A has a variably adjustable temperature profile, which is realized by corresponding power controllers of the NIR dryers, and the warm air flow is also adjustable. Directly connected to the NIR dryer 1A in the conveying direction of the support 2, downstream of the NIR dryer 1A, is a hot air dryer 1B, which also has warm air ventilation Vi / Vo with a variably adjustable air flow.

[0033] With a total system length of several meters, which is considered advantageous for reasons of space, and with an NIR dryer equipped with commercially available NIR emitters with an associated reflector, throughput speeds in the range of 1 - 2 m / min can be achieved while taking into account the quality requirements of the drying process, thus creating a drying process that offers significant advantages over conventional drying systems in terms of space requirements and throughput.

[0034] Fig. 2 shows, in the form of a functional block diagram, the essential components of an exemplary NIR dryer 1A according to Fig. 1 The figure is intended to be a schematic diagram and is not intended to show the actual mechanical structure of the NIR dryer. For simplicity, only the functional components above the carrier 2 are shown. Corresponding components can also be provided below the carrier; however, embodiments of the arrangement according to the invention are also possible in which corresponding means are provided exclusively on one (the coated) side of the carrier.

[0035] The NIR dryer 1A comprises several NIR emitters 11, each with an associated reflector 12, which are individually connected to a control output of a power control unit 13. The power control unit 13 can thus be used to separately adjust the irradiation power of each individual NIR emitter 11, thus realizing a predetermined power density profile of the NIR radiation on the carrier 2 over the length of the NIR dryer 1.

[0036] A quantity of air, which can be controlled by an air quantity control unit 15, enters the inlet of NIR dryer 1A via an air supply 14, and the heated exhaust air, which has absorbed solvent components of the coating 2a, reaches a heat exchanger and filter unit 17 via an exhaust air outlet 16. In the heat exchanger and filter unit 17, excess heat is extracted from the exhaust air of the NIR dryer and made available for external use, and the solvent components are filtered out in an environmentally friendly manner and recycled if necessary.

[0037] Fig. 3 shows an example of an arrangement 1' for carrying out the method according to the invention, in which two transport rollers 1C, 1E are schematically shown as conveying means for conveying the carrier 2 through the arrangement and a doctor blade device 1D as a coating device. For sintering / crosslinking the coating 2a applied to the carrier 2, an NIR irradiation zone 1A' is realized by a plurality of NIR radiators 11a-11g, each with an attached reflector 12a-12g.

[0038] It should be noted that the number and design of the NIR emitters is merely a conceptual representation. A set of emitters with different reflector geometries at different distances creates a preheating zone 1.1, a main drying zone 1.2, and a temperature maintenance zone 1.3 within the NIR irradiation zone 1A'. This represents an alternative to the previously described Fig. 2 explained individual power settings of basically identical NIR emitters.

[0039] In an arrangement according to the invention, NIR emitters that are particularly suitable are cost-effective, long-established, and long-standing halogen lamps for drying applications. In principle, however, an NIR irradiation zone can also be realized using differently shaped emitters or an LED array with correspondingly powerful IR LEDs. Both designs are familiar to those skilled in the art and therefore require no further explanation here.

[0040] Reflectors can be individual reflectors, each structurally combined with a radiator, as well as integrated reflector arrangements assigned to several radiators. Even in such interconnected reflector assemblies, different reflector geometries are possible for the respective radiators (as in Fig. 3 shown in sketch form) can be realized.

[0041] Arrangements of the type shown in the figures, possibly modified for specific applications, can also be used to manufacture products in the field of printed electronics. In these cases, the substrates are, for example, paper or plastic films, which, depending on the material, must not be heated above limit temperatures in a range between approximately 80°C and 140°C. The coatings can be conductive inks, pastes, or even powders, depending on the function of the respective component. The thermal treatment therefore aims at evaporating water or solvents, sintering the paste, melting and possibly sintering a powder, and possibly also inducing thermochemical reactions and phase transformations in the coating.

[0042] According to the inventors' investigations, the use of an NIR irradiation zone also offers a significant acceleration in these processes and thus the possibility of a significant increase in throughput and / or reduction in the length of a corresponding dryer.

[0043] The embodiment is not limited to the examples and aspects highlighted above, but is also possible in a variety of modifications that are within the scope of the appended claims.

Claims

1. Method for producing electrical or electronic components or circuits on a flexible flat or three-dimensional carrier by applying a liquid or pasty starting material for a structured or unstructured electrical or electronic functional layer and then drying, sintering, and / or cross-linking the starting material on the carrier, wherein the step of drying, sintering and / or cross-linking includes exposing the coated substrate to radiation from halogen emitters or IR LEDs in the near-infrared range, the maximum amplitude of which lies in the wavelength range between 800 nm and 1,500 nm, designed as a method for manufacturing a battery or fuel cell electrode, wherein a polymer film with a thickness in the range between 75µm and 200µm or a metal film with a thickness in the range between 3µm and 10µm is used as the substrate and a viscous paste based on water or an organic solvent is used as the coating, which has an initial thickness in the range between 10 and 1,000µm and a solid content in the range between 40% and 80%, and wherein near-infrared radiation with a power density in the range between 50 and 200 kW / m2, in particular between 70 and 150 kW / m2 with an exposure time in the range between 1 s and 30 s, in particular between 2 s and 20 s, is used for drying, sintering and / or crosslinking.

2. Method according to claim 1, wherein the carrier is a temperature-sensitive carrier, namely a polymer film, and the power density and exposure time of the near-infrared radiation are adjusted such that the temperature does not rise above a material-critical temperature, in particular not above a material-critical temperature in the range between 100°C and 200°C.

3. Method according to claim 1, wherein a pasty starting material is applied to the carrier essentially over the entire surface, in particular by a roller or squeegee application process, and the power density and exposure time of the near-infrared radiation are adjusted such that a temperature above a material-specific sintering or cross-linking temperature is reached in the selective coating.

4. Method according to one of the preceding claims, wherein the exposure to near-infrared radiation is carried out within a NIR irradiation zone with a predetermined profile of non-constant power density and, in particular, the radiation density profile in the irradiation zone is adjustable in response to material properties of the substrate and / or the starting material.

5. Method according to one of the preceding claims, wherein the exposure to near-infrared radiation is combined with exposure to an air flow at least on one surface of the carrier.

6. Method according to claim 5, wherein the supply of warm air in the irradiation zone and / or the supply of hot air in an optionally provided hot air dryer is provided on both surfaces of the carrier and, in particular, is adjustable.

7. Method according to one of the preceding claims, wherein, following the exposure to near-infrared radiation, the coated carrier is passed through a treatment temperature holding zone, in particular a hot air dryer.

8. Arrangement for carrying out the method according to one of the preceding claims, comprising - conveying means for conveying the flexible flat carrier through the arrangement, - coating means for coating the flat carrier with the starting material, in particular during the conveying of the carrier, and - means for drying, sintering, and / or cross-linking the starting material layer on the carrier, in particular during the transport of the carrier, which include at least one halogen radiator or an IR LED for radiation in the near-infrared range, whose maximum amplitude lies in the wavelength range between 800 nm and 1,500 nm and which are adjustable in such a way that their power density on the surface of the carrier lies in the range between 50 and 200 kW / m2 whereby the conveying means and coating means are adapted ly such that a polymer film with a thickness in the range between 75µm and 200µm or a metal film with a thickness in the range between 3µm and 10µm is used as the carrier and a viscous paste based on water or an organic solvent is used as the coating, which has an initialthickness in the range between 10 and 1,000µm and a solid content in the range between 40% and 80%.

9. Arrangement according to claim 8, wherein the means for drying, sintering and / or crosslinking include a plurality of NIR radiation sources which are arranged and / or controllable in a NIR irradiation zone in such a way that a predetermined profile of non-constant power density can be generated within the irradiation zone on the surface of the starting material layer.

10. Arrangement according to claim 8 or 9, wherein the means for drying, sintering and / or cross-linking further comprise a treatment temperature holding zone, which is designed in particular as a hot-air dryer.

11. Arrangement according to claim 9 or 10, wherein the NIR irradiation zone is assigned means for supplying an air flow.

12. Arrangement according to claim 11, wherein the means for supplying an air flow and / or the treatment temperature holding zone comprise control means for controlling the air flow or the temperature in the treatment temperature holding zone.