Process for producing an electrical component by means of successive printing and sintering of particle-containing ink

Abstract

A process for producing an electrical component (1), in particular a sensor such as a gas sensor or a solid oxide fuel cell, is presented. The process comprises: (a) providing a substrate (3), (b) printing a first layer (5) of an ink (7) onto the substrate, wherein the ink comprises a flowable binder and a multiplicity of particles (9) of a metallic, metal-oxide and / or ceramic material that are incorporated in the binder, (c) sintering the substrate including the first layer of ink at a temperature above 300°C, preferably at least 600°C, for a period within a range from 1 min to 1 h, preferably less than 20 min, (d) printing a further layer (11) of an ink onto the substrate, wherein the ink comprises a flowable binder and a multiplicity of particles of a metallic and / or ceramic material that are incorporated in the binder, (e) sintering the substrate including the further layer of ink at a temperature above 300°C for a period within a range from 1 min to 1 h, wherein steps (d) and (e) are repeated multiple times. The combination of ink jet-printed layers and respective sintering of each individual layer in a short and hot sintering operation allows rapid, flexible and cost-effective manufacture of the component.

Description

[0001] METHOD FOR PRODUCING AN ELECTRICAL COMPONENT

[0002] BY SUCCESSIVE PRINTING AND SINTERING OF

[0003] PARTICLE-CONTAINING INK

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to a method for producing an electrical component, in particular a sensor, such as a gas sensor, or a solid oxide fuel cell. The invention further relates to an electrical component that can be produced using the method.

[0006] BACKGROUND OF THE INVENTION

[0007] Electrical components can be used for a wide variety of purposes. The functionality of such components can be influenced in particular by their structural design and the properties of the materials used. For example, electrical components can be composed of several different layers. Each of these layers can be specifically selected or adapted for the intended use of the electrical component with regard to its structural properties, such as its layer thickness, contour, homogeneity, porosity, surface texture, etc., as well as its material-specific properties, such as its electrical properties (especially conductivity), thermal properties (especially coefficient of expansion), mechanical properties, etc.

[0008] For example, gas sensors are known in which electrodes are arranged on a layer with solid electrolytic properties. The electrodes can be metallic or metal oxide, for example. An electrical voltage can be applied to the solid electrolytic layer they contact via the electrodes. The solid electrolytic layer can be constructed from ceramic and / or metal oxide material. Free ions can move within the solid electrolytic layer due to the applied electrical voltage, particularly when the solid electrolytic layer is heated to elevated temperatures of, for example, over 400°C. The concentration of free ions can depend on ambient conditions. Such ambient conditions generally include, in particular, gases that come into contact with the layer.Accordingly, by measuring an electric current flowing due to the electrical voltage applied to the layer, conclusions can be drawn about the ambient conditions, in particular surrounding gases and their concentrations.

[0009] Solid oxide fuel cells (SOFC) are also known, in which, among other things, a layer of a solid electrolyte is arranged between electrodes.

[0010] Various manufacturing processes have been developed to produce electrical components made up of layers of different materials. For example, layers can be applied to a substrate by physical vapor deposition (PVD) and / or chemical vapor deposition (CVD). Alternatively, layers can be applied to the substrate using printing techniques such as screen printing. However, the technologies conventionally used to apply the layers usually require complex and / or expensive equipment to deposit the layers. Furthermore, both vapor deposition techniques and printing techniques are usually configured to cover the entire surface with a layer. This means that if only parts of a surface are to be coated, i.e. if a layer with a pattern orIf a contour is to be applied, additional measures such as the use of masks, stencils, etc. are required. This often results in additional effort and costs. Furthermore, in addition to the actual surfaces to be coated, adjacent surfaces covered by the mask or stencil are also printed, resulting in a significant additional consumption of printed material.

[0011] SUMMARY OF THE INVENTION AND ADVANTAGEOUS EMBODIMENTS

[0012] It was therefore recognized that there may be a need for an improved method for manufacturing an electrical component, as well as for an electrical component that can be manufactured thereby. In particular, the component should be able to be manufactured with minimal material expenditure, minimal equipment expenditure, in a short time, with high reliability, high energy efficiency, with high flexibility of the manufacturing process, and / or at relatively low cost.

[0013] Such a need can be met by the subject matter of one of the independent claims. Advantageous embodiments are set forth in the dependent claims and in the following description and illustrated in the figures.

[0014] According to a first aspect of the invention, a method for manufacturing an electrical component is presented. The method comprises at least the following steps, preferably in the specified order:

[0015] (a) providing a substrate,

[0016] (b) printing a first layer of an ink onto the substrate, wherein the ink comprises a flowable binder and a plurality of particles of a metallic, metal oxide and / or ceramic material embedded in the binder,

[0017] (c) sintering the substrate including the first layer of ink at a temperature above 300°C for a period of time in a range of 1 minute to 1 hour,

[0018] (d) printing a further layer of an ink onto the substrate, the ink comprising a flowable binder and a plurality of particles of a metallic and / or ceramic material embedded in the binder,

[0019] (e) sintering the substrate including the further layer of ink at a temperature above 300°C for a time in a range of 1 minute to 1 hour, wherein steps (d) and (e) are repeated with a plurality of repetitions.

[0020] According to a second aspect of the invention, an electrical component, in particular a sensor or a solid oxide fuel cell, is presented. The component comprises a substrate and a plurality of layers of a metallic, metal oxide, and / or ceramic material applied to the substrate. Each of the layers is produced by printing an ink comprising a flowable binder and a plurality of particles of a metallic, metal oxide, and / or ceramic material embedded in the binder, and subsequently sintering the ink at temperatures above 300°C.

[0021] Possible features and advantages of embodiments of the invention may be considered, among other things and without limiting the invention, to be based on ideas and findings described below.

[0022] Briefly summarized, and without limiting the invention in any way, the principle underlying the manufacturing process presented here is that full-surface and / or structured layers are printed onto a substrate using inkjet techniques, and the layers are suitably solidified by sintering in order to impart structural and functional properties to them. One or more of the inks used contain, in addition to a binder, a powder with particles of metallic, metal oxide, and / or ceramic material. The ink is printed in a thin layer and then subjected to a sintering process. The sintering process is specifically adapted to solidify the ink and sinter the particles it contains into a single layer.Sintering parameters are selected so that the sintering process can be relatively short while still achieving the desired properties of the sintered layers. In particular, it was recognized that by printing multiple layers successively and solidifying each individual layer in a short, sufficiently hot sintering step before a subsequent layer is printed, a layer stack with the desired structural and functional properties for the formation of an electrical component can be created. The combination of layer formation by inkjet printing, on the one hand, and short, hot sintering steps for each individual layer, on the other, enables high efficiency in terms of material utilization, energy consumption, required equipment, short manufacturing process duration, etc.In addition, the use of inkjet printing allows structured layers with different contours to be produced in a simple manner, which means that the described manufacturing process can be flexibly and quickly adapted to the production of different electrical components.

[0023] Possible details and advantages of embodiments of the described method are given below.

[0024] The method presented here for producing an electrical component generally begins with providing a suitable substrate. The substrate is usually flat, i.e. disc-shaped. In particular, the substrate can be a type of wafer. The substrate can have lateral dimensions in the range of more than 1 mm, preferably more than several millimeters, more than 1 cm or even more than several centimeters up to several decimeters or even several meters. A thickness of the substrate can be less than 1 cm, preferably less than 3 mm, less than 1 mm or even less than 0.5 mm. The substrate can provide the entire electrical component with a predominant portion of its mechanical strength. The substrate can be self-supporting.

[0025] The substrate should be made of a material that can withstand high temperatures, especially temperatures above 300 °C, above 500 °C, above 600 °C, or even above 800 °C, without damage. The use of a temperature-resistant material for the substrate enables sintering at relatively high temperatures in subsequent process steps.

[0026] In contrast, substrates based on plastics, in particular polymers, have traditionally been used in the manufacture of electrical components. These substrates are inexpensive and / or can be bent in a desired manner for some applications, but typically have only low temperature resistance, ie they should not be heated above 200 °C, for example, and often even not above 150 °C or 100 °C, as they may otherwise suffer permanent damage, in particular permanent deformation.

[0027] According to one embodiment, the substrate may consist of an inorganic material. In particular, the substrate may consist of a ceramic material or a semiconductor material. For example, the substrate may consist of aluminum oxide (Al2O3), aluminum nitride (AlN), zirconium oxide (ZrO2), silicon carbide (SiC), silicon nitride (Si3N4), aluminum titanate (Al2TiO5), or even aluminum silicates, aluminum oxide-silicon oxide compositions, and / or silicon. Such materials are typically very temperature-resistant. Furthermore, they may, for example, have low expansion coefficients and / or high thermal shock resistance and are thus well suited for use at high temperatures.

[0028] According to one embodiment, the substrate can be made of an electrically insulating material. The use of an electrically insulating material can be advantageous for functionalities of the electrical component to be formed. In particular, the substrate can serve as electrical insulation between adjacent electrically conductive layers. A first layer, followed by further layers of ink, are subsequently printed onto the substrate.

[0029] The ink's composition and rheology, particularly its flowability and viscosity, are adapted for printing onto a substrate surface using inkjet printing techniques. Tiny droplets, typically with a volume in the picoliter range (often in a volume range of 0.1 pL to 30 pL, preferably 0.5 pL to 5 pL), are sprayed from a print head toward the surface to be printed. The droplets can be printed very closely spaced or even overlapping each other. This allows the surface to be printed to be wetted with ink, at least in partial areas. Ultimately, the entire surface can be covered with a layer of ink.Alternatively, only partial areas of the surface can be covered with a layer of ink, thereby creating contoured or patterned layer areas of ink that are adapted to create desired functionalities in the electrical component.

[0030] The ink generally comprises a flowable binder. Binders that can be used include, for example, glycol ethers (e.g., triethylene glycol (TGME)), alcohols (e.g., ethanol, methanol, ethylene glycol), terpineols, dimethylformamide (DMF), diethanolamine (DEA or DEOA), dimethyl sulfoxide (DMSO), water, or cyclohexanone. Particles made of a metallic, metal oxide, and / or ceramic material are embedded in the binder. The volume fraction of the particles in the ink can range from less than 1 wt.% up to 70 wt.% or even more, for example, from 1 wt.% to 70 wt.%, preferably from 2 wt.% to 50 wt.%.

[0031] To form an electrically conductive layer, for example, the ink can contain metallic or metal oxide particles. For example, the particles can consist of metals such as platinum (Pt), gold (Au), copper (Cu), silver (Ag), nickel (Ni), palladium (Pd), tin (Sn), or mixtures or alloys thereof. In particular, it can be advantageous for the functionality of the component to be formed to use particles made of precious metals. The metals can also be present as metal oxides. Metal oxides have different properties than pure metals or their mixtures or alloys. Metal oxides are used in metal oxide sensors, e.g. n-type semiconductor sensors or in field-effect transistors. Materials for this include zinc oxide (ZnO), tungsten oxide (WO3), aluminum-doped zinc oxide (AZO), palladium oxide (PdO), nickel oxide (NiO), tin oxide (SnO2), titanium oxide (TiO2), cerium oxide (CeO2), copper oxide (CuO), indium tin oxide (ITO).

[0032] To enable the ink to form, for example, an electrically insulating layer, particularly a layer acting as a solid-state electrolyte, or special types of electrodes (e.g., for fuel cells), the ink can contain ceramic particles. For example, the particles can consist of yttrium oxide-stabilized zirconium oxide (YSZ). Alternatively, the particles can consist of lanthanum strontium cobalt ferrite (LSCF), lanthanum strontium gallium magnesium oxide (LGSM), lanthanum strontium ferrite (LSF), gallium-doped cerium oxide (GDC), or other types of perovskite.

[0033] According to one embodiment, the particles in the ink should be nanoparticles. Such nanoparticles typically have dimensions in the nanometer range, i.e., in the submicrometer range. Due to their small size, even very small droplets, such as those sprayed in inkjet printing, can contain very many tiny particles. This enables the desired rheology of the ink. The ink can also be referred to as a nanoparticle suspension.

[0034] According to one embodiment, the ink and thus the layers formed therewith are printed in such a way that the layer has a layer thickness of between 5 pm and 60 pm, preferably between 10 pm and 30 pm, after printing and before subsequent sintering. By printing such thin layers, the properties of an overall layer formed by the multiple layers can be influenced in a desired manner. In particular, the individual layers can be so thin that they do not flow laterally after printing, or at most only flow insignificantly. This allows layers with a desired lateral contour to be printed precisely. Furthermore, the individual layers can be so thin that binding agents escape from them quickly and easily.

[0035] In this context, it should be noted that the layer thickness that results during or after printing can be influenced by other factors besides the volume of ink applied. For example, the porosity or absorbency of the substrate to be printed can influence how much of the ink is absorbed into the substrate and thus does not form part of the layer above. In this case, the layer thickness can be understood as the thickness of the layer that remains above the surface of the substrate when the substrate is already saturated with the ink absorbed into it. Furthermore, the ink can have a curved outer surface due to surface tension, in which case the layer thickness can be understood as the maximum thickness of the layer.The volume fraction of particles absorbed in the ink can also vary greatly, for example between a few percent and up to 70 vol%, and can influence the required ink layer thickness.

[0036] After each layer is printed, the printed layer undergoes a sintering process before the next layer is possibly printed.

[0037] Sintering takes place at a temperature of more than 300°C. Preferably, after printing at least one of the multiple layers, the sintering process is carried out at a temperature of more than 500°C or even a temperature of 600°C or more. In particular, it may be advantageous to carry out the subsequent sintering process at above 500°C or even at least 600°C, at least after printing the last of the multiple layers. In other words, it is considered advantageous to subject each of the printed layers to sintering at least once at at least 500°C, preferably at least 600°C. Preferably, each of the sintering processes after printing each layer is carried out at at least 500°C, preferably at least 600°C. The sintering process can take place relatively quickly and is therefore sometimes referred to herein as a rapid sintering process.In particular, sintering may take longer than 1 minute but less than 1 hour. Preferably, the sintering time for at least one of the sintering steps, and preferably for all sintering steps, is less than 20 minutes, preferably less than 15 minutes, or even less than 10 minutes. In contrast, conventional thermal sintering usually requires very long sintering times of several hours to obtain a layer with a high density.

[0038] It has been observed that, particularly at the desired high sintering temperatures, a relatively short sintering step can be sufficient to impart the desired functionality, in particular the desired electrical properties such as ionic or electrical conductivity, to the printed and then sintered layer, as is desired for the formation of a manufactured electrical component. Due to the short duration of each individual sintering step, the entire component with multiple printed layers can be built within a short time, particularly within a few hours.

[0039] To sinter the respective printed layer, according to one embodiment, the substrate can be placed in an oven preheated to at least 300°C, preferably at least 500°C or at least 600°C, immediately after the respective layer has been printed, in particular without prior drying and / or compacting of the printed layer. In other words, in contrast to conventional methods, in which an applied layer must first be dried and / or compacted prior to sintering to prevent damage to the layer during sintering, such additional process steps can be dispensed with.

[0040] Conventionally applied layers are often very thick and therefore require a significant amount of binder in order to create a layered structure with a high thickness in a single step. To prevent the binder from damaging the layer during sintering, it usually has to be evaporated beforehand in a drying process and / or the layer has to be compacted. In the process presented here, layered structures are composed of individual, very thin layers, and each of these thin layers is sintered individually. Since each layer contains only a small amount of binder and this can escape over a relatively large surface area, each layer can be sintered without prior drying and / or compaction. Accordingly, the substrate can be placed in a preheated oven immediately after the respective layer has been printed.The time between printing and sintering can thus be as short as a few minutes, for example, less than 10 minutes, less than 5 minutes, or even less than 2 minutes. This can save considerable time and effort.

[0041] According to one embodiment, sintering can be carried out without surrounding the substrate in a protective gas atmosphere. Additionally or alternatively, sintering can be carried out without applying an electrical voltage to the substrate.

[0042] Alternative sintering processes are known for certain applications or for the production of specific components. For example, in so-called ultrafast sintering, electrical voltages are applied to a substrate to be sintered. For this purpose, for example, two strips of carbon fiber are placed on a sintered sample and then an electrical voltage is applied, which can create temperatures of up to 3000 °C in the sintered sample. However, contacting each individual sintered sample requires considerable effort. In addition, the sintered sample must usually be protected during sintering by surrounding it with a protective gas atmosphere. In an alternative approach, also known as flash sintering, an additional electric field is applied to a sintered sample at a specific sintering temperature. This can limit the sintering time to just a few minutes.However, higher energy consumption and additional modules for applying the electric field are generally required.

[0043] In contrast to the approaches described above, the sintering processes used in the manufacturing process proposed here can essentially be carried out under ambient conditions. The substrate with the layer applied thereto only needs to be brought to an elevated sintering temperature, without the need to create a special gas atmosphere around the substrate. In particular, there is no need to provide a protective gas, for example in the form of a noble gas or inert gas. There is also no need to generate an electric field, in particular electrical contact with the layer to be sintered in order to apply an electrical voltage. Overall, this allows the process to be carried out with very minimal equipment, low energy consumption, and / or in a short time.

[0044] According to one embodiment, the substrate is cooled to ambient temperature after sintering and before printing each of the subsequent layers. The ambient temperature can typically be between 10°C and 30°C, preferably between 15°C and 25°C. For this purpose, the substrate can be removed from the furnace and then, due to its large surface area, cooled to ambient temperature relatively quickly, i.e., in particular within a few minutes. The printing process can thus be carried out without the need for special precautions, for example, for heating or cooling the substrate.

[0045] According to a specific embodiment, a complete layer of ceramic material is first deposited on the surface of the substrate. For this purpose, the first layer and, preferably, one or more of the further layers directly adjacent to the first layer are printed with an ink containing particles of ceramic material. In other words, a layer stack, preferably comprising several thin layers, is created by printing ink containing ceramic nanoparticles, with each of the thin layers being sintered before the subsequent layer is printed. Overall, this can generate a ceramic layer whose layer thickness is composed of the individual thin layers. This ceramic layer can serve as a solid-state electrolyte layer within a component to be formed, in particular within a sensor or a fuel cell.Subsequently, a further overall layer of electrically conductive material can be applied to the layer of ceramic material. For this purpose, one or preferably several of the additional layers can be printed with an ink comprising particles of a metallic and / or metal oxide material. Similar to the ceramic layer, the electrically conductive overall layer can also be created by a plurality of successively printed and sintered thin layers. The electrically conductive overall layer can serve to form one or more electrodes within the component to be formed.

[0046] According to a further specific embodiment, a multilayer stack can be formed from alternating at least two layer stacks with ceramic material and at least two layer stacks with metallic material. Each of the layer stacks with ceramic material is formed by printing the first layer and / or one or more of the further layers directly adjacent to one another with an ink comprising particles of a ceramic material. Each of the layer stacks with metallic material is formed by printing one or more of the further layers directly adjacent to one another with an ink comprising particles of a metallic and / or metal oxide material.

[0047] In other words, an electrical component can be formed by stacking several layer stacks on top of each other to form an overall stack. Each individual layer stack can be composed of a single layer or, preferably, several layers, wherein the layers of a layer stack are each formed using the same ink. At least two different types of layer stacks are produced and stacked alternately on top of each other. A first type of layer stack is produced using ink with ceramic particles and is therefore referred to as a layer stack with ceramic material, whereas a second type of layer stack is produced using ink with metallic and / or metal oxide particles and is therefore referred to as a layer stack with metallic material. The layer stacks with metallic material can form an electrode or part of an electrode.Between adjacent layer stacks of metallic material, a layer stack of ceramic material is interposed, which can form a solid-state electrolyte layer.

[0048] By alternately forming layer stacks with ceramic material and layer stacks with metallic material, an overall stack can be formed in which one or more electrode layers are separated from each other by intermediate solid electrolyte layers.

[0049] It has been observed that such a multilayer stack offers various advantages. For example, it has been recognized that a sensor formed with the various alternating layer stacks can measure with greater sensitivity and / or precision the more adjacent interfaces between an electrode layer and a solid electrolyte layer it contains. Furthermore, it has been observed that material phases can form locally at adjacent interfaces between an electrode layer and a solid electrolyte layer, which can have beneficial effects. For example, such material phases can impart increased mechanical and / or chemical stability to the sensor.

[0050] In particular, at least one of the further layers can be printed in the form of a pattern that depicts two electrodes that are laterally spaced from one another. In other words, one or more of the printed layers can be printed not as a continuous or full-surface layer, but as at least two partial layers, wherein the two partial layers are laterally spaced from one another and each partial layer, with its contour, forms one of two or more electrodes. The two electrodes can thus be formed spatially separated from one another on the underlying ceramic layer and accordingly connected to one another only via the ceramic layer and otherwise electrically insulated from one another. If the ceramic layer serves as a solid-state electrolyte layer, an electrical current that occurs when an electrical voltage is applied to the two electrodes can depend on the properties of this solid-state electrolyte layer.The properties of the solid-state electrolyte layer can in turn depend on environmental conditions, particularly the surrounding gas atmosphere, so that the entire component can act as a gas sensor.

[0051] The electrical component according to an embodiment of the second aspect of the invention can be manufactured, in particular, using the method presented herein. The component comprises multiple layers of metallic, metal oxide, and / or ceramic material on a substrate. The layers are produced by printing an ink comprising a binder and embedded particles, followed by sintering the ink at temperatures above 300°C, preferably at least 500°C. In particular, each of the layers is individually sintered after printing. Due to such manufacturing, the overall layer formed from the multiple layers has typical microscopic and / or macroscopic properties, in particular a typical microscopic and / or macroscopic structure. In particular, it can be seen in the overall layer that particles are sintered together in each of the individual layers.The stacked structure of the multiple layers, which were printed one after the other and each sintered, is also evident in the final overall layer and can serve as a typical feature that the electrical component was manufactured according to an embodiment of the method described herein. For example, a porous structure typical of the manufacturing process is evident. This generally results in excellent functionality of the layer. The porous structure typically results in an increased surface area or reaction area at the so-called three-phase boundary (TPB). Furthermore, sintering necks of the sintered nanoparticles are usually visible, which is typical of this manufacturing process.

[0052] It should be noted that possible features and advantages of embodiments of the invention are described herein partly with reference to a manufacturing method designed according to the invention and partly with reference to an electrical component according to the invention. A person skilled in the art will recognize that the features described for individual embodiments can be suitably transferred, adapted, and / or exchanged in an analogous manner to other embodiments in order to achieve further embodiments of the invention and possibly synergistic effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Advantageous embodiments of the invention are further explained below with reference to the accompanying drawings, wherein neither the drawings nor the explanations are to be interpreted as limiting the invention in any way.

[0054] Fig. 1 (a) - (d) shows in side views a sequence of process steps of a manufacturing method according to an embodiment of the present invention.

[0055] Fig. 2 shows a plan view of an electrical component according to an embodiment of the present invention.

[0056] Fig. 3 shows a sectional view through a multi-layer electrical component according to an embodiment of the present invention.

[0057] The figures are merely schematic and not to scale. The same reference numerals designate the same or equivalent features in the various drawings.

[0058] DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS

[0059] Fig. 1 shows a sequence of process steps for producing an electrical component 1 in side views. Fig. 2 shows a plan view of a finished component 1 in the form of a gas sensor 29.

[0060] As illustrated in Fig. 1(a), a substrate 3 is first provided. For example, a disk or wafer made of aluminum oxide or silicon can serve as the substrate 3. A first layer 5 of ink 7 is printed onto the substrate 3 using an inkjet head 21, as shown in Fig. 1(b). The ink 7 comprises particles of metallic, metal oxide, or ceramic material embedded in a binder.

[0061] After the first layer 5 has been printed, the substrate, together with this first layer 5, is subjected to a sintering process. During this process, the substrate 3, together with the layer 5 of ink 7, is sintered for up to five minutes at 600°C, in some cases at up to 900°C. As schematically illustrated in the enlarged section in Fig. 1(c), the particles 9 contained in layer 5 come into direct contact with one another after the binder of the ink 7 has escaped. Neighboring particles 9 can form integral bonds with one another during sintering due to the resulting diffusion processes and / or local melting and / or form so-called sinter necks.

[0062] After sintering, the substrate 3 is removed from the furnace and allowed to cool to ambient temperature.

[0063] Subsequently, several further layers 11 of ink 7 are successively printed onto the substrate 3. After each individual printing process, the respective printed layer 11 is sintered, preferably at a temperature adapted to the printed material, for example, 600 °C or more, and for ceramic materials typically even 900 °C or more.

[0064] As illustrated in Fig. 1(d) and Fig. 2, this makes it possible to produce a layer stack 13 with ceramic material on an upper side of the substrate 3, which layer stack forms a solid-state electrolyte layer 19. The layer stack 13 with ceramic material can be produced by printing an ink 7 with ceramic particles 9 to form one or more adjacent layers 11'. A further layer stack 15 with metallic material is formed above this solid-state electrolyte layer 19, thereby producing one or more electrodes 17. The layer stack 15 with metallic material can be produced by printing an ink 7 with metallic or metal oxide particles 9 to form one or more adjacent layers 11".

[0065] In particular, two electrodes 17 can be formed laterally spaced from one another such that a gap 23 remains between them. When an electrical voltage is applied to the two electrodes 17, an electrical current can only flow between the electrodes 17 if the solid electrolyte layer 19 adjacent to the electrodes 17 has a certain conductivity, in particular due to ionic conduction. In other words, a direct electrical voltage can be applied between the two printed electrodes, whereby an oxygen ion current can flow in the solid electrolyte (heated, for example, to at least 400°C (for YSZ)) and an electrical current can flow in the external circuit electrically connected to it. Since the ionic conductivity of the solid electrolyte layer 19 depends, among other things, on the surrounding gas atmosphere, this can be used to determine the concentration of gases in the environment.Overall, the electrical component 1 can therefore act as a gas sensor 29.

[0066] In addition, a further layer stack 25 with metallic material can be formed on a back side of the substrate 3 of the component 1, which can act as a heating coil 27 so that the entire gas sensor 29 can be heated to a predetermined temperature if required.

[0067] Fig. 3 shows a sectional view through an electrical component 1 designed as a gas sensor, in which two layer stacks 13 with ceramic material and two layer stacks 15 with metallic material were deposited alternately on top of one another, thereby forming a multi-layer overall stack 16. Each of the layer stacks 13 with ceramic material comprises at least one or preferably several layers 11', each of which was produced by printing an ink 7 with ceramic material and subsequent sintering, and which together form a solid electrolyte layer 19. Each of the layer stacks 15 with metallic material comprises at least one or preferably several layers 11", each of which was produced by printing an ink 7 with metallic or metal oxide material and subsequent sintering, and which together form an electrode 17 or part of an electrode 17.

[0068] It should be noted that in the figure, each of the layer stacks 13, 15 has only two layers 11' and 11", respectively, but that in practical applications, significantly more such layers may be present. Furthermore, in practical applications, more than two layer stacks 13 with ceramic material may be provided for forming the solid electrolyte layer 19 and / or more than two layer stacks 15 with metallic material may be provided for forming the electrode 17.

[0069] Each of the layer stacks 15 can be structured in such a way that two laterally spaced-apart electrodes 17 are formed (as illustrated in Fig. 2). The two electrodes 17 in the various layer stacks 15 can have identical or different contours, but preferably at least partially overlap each other in plan view. The layer stacks 13 extending between the adjacent layer stacks 15 for forming the solid electrolyte layer 19 can be formed over the entire surface, particularly since they are generally porous and gas can thus flow through these solid electrolyte layers 19. Alternatively, the layer stacks 13 for forming the solid electrolyte layer 19 can also be structured, particularly with a geometry or contour analogous to the geometry of the layer stacks 15 forming the electrodes 17.

[0070] Three-phase boundaries (TPB) can form at interfaces between adjacent layer stacks 13 of the solid-state electrolyte layer 19, on the one hand, and layer stacks 15 of the electrodes 17, on the other hand. Due to the large number of such interfaces within the overall stack 16, the sensitivity of the overall sensor-like electrical component 1 can be improved. Following are accompanying thoughts on the approach explained herein, as well as possible embodiments of the method presented herein, or the resulting component, presented again with slightly different terminology:

[0071] On a large scale, electrochemical sensors have so far been manufactured primarily using screen printing or, in some cases, PVD processes. Both processes consume a lot of material compared to inkjet printing, as they generally also require sputtering or printing on a mask. The well-known large-scale manufacturing methods of PVD and screen printing therefore have high material consumption and require the purchase of masks. Therefore, the existing methods for manufacturing electrochemical sensors are not particularly flexible. Rapid prototyping or quick adaptation to the manufacturing technology is hardly possible or only possible with a lengthy process.

[0072] The approach described here utilizes, among other things, inkjet printing, sometimes referred to as the inkjet process. Since the inkjet process is maskless, it eliminates the high material consumption typical of conventional processes. Furthermore, the inkjet printing process is a purely digital process. This eliminates additional production steps or purchases such as a mask, which are typically required with PVD and screen printing systems. The known process solutions require additional equipment, have high energy consumption, or are limited to the sintering of dense materials ("green bodies"), or do not describe the process of individually sintered (metallic and ceramic) layers. Furthermore, some of the known methods cannot sinter at ambient temperatures, and rapid production of the entire system is not possible.

[0073] The process presented here also offers a significant improvement in inkjet printing in that the overall process time can be significantly reduced and the energy consumption for sintering is lower than previously used processes. Furthermore, the process described here promises applicability to metallic and ceramic materials, as well as good control over layer thickness and morphology. For the first time, multiple individual layers could be printed, each of which, with the aid of a thermal "rapid" sintering step (thermal rapid sintering), led to a functional electrochemical solid electrolyte sensor. This process results in morphologies that are advantageous for sensor function.

[0074] The approach described herein represents a rapid process route for the production of electrochemical solid electrolyte sensors and / or SOFCs using inkjet processes, employing layer-by-layer printing of functional materials in combination with a rapid sintering process for the production of electrochemical solid electrolyte components. It refers to a general process for the production of thin metallic, ceramic, and / or metal oxide layers, whereby individual nanoparticle suspension layers are applied layer by layer and sintered using a rapid thermal sintering process under ambient conditions. The process allows for the production of ceramic and metallic layers in an energy-efficient, simple, fast, and well-controlled manner with regard to morphology (porous or dense, layer thickness, and homogeneity of the layers).The produced layers can be used in the field of electrochemical (high-temperature) solid electrolyte components (e.g. sensors and SOFCs).

[0075] The electrochemical (high-temperature) solid electrolyte components (sensors and SOFCs) mentioned here consist in particular of the following single-layer structures:

[0076] Electrolyte: a ceramic layer

[0077] Electrode: a metallic / (metal oxide) layer Heating coil: a metallic layer

[0078] Several functional solid electrolyte oxygen sensors have already been manufactured. Good results were achieved with the sensors in both short characterization tests and a 2,000-hour long-term test.

[0079] The rapid process route for the production of electrochemical high-temperature solid electrolyte sensors using inkjet technology is intended to reduce both production time and energy consumption for the production of such layers. Furthermore, the presented process generally eliminates the need for a drying or densification step (unlike other sintering processes). Another aspect is the process time: The layer-by-layer construction combined with rapid sintering significantly shortens the process time compared to conventional methods. The quality of the layers (in terms of porosity, electrochemical properties, and long-term stability) has even been significantly improved.

[0080] Al2O3 is used as the substrate material. In principle, other temperature-stable materials, such as silicon wafers, could also be used. Using metallic or ceramic nanoparticle suspensions or nanoparticle inks, individual layers are printed with a suitable dot density. After each layer, they are sintered at material-specific temperatures for less than 15 minutes (thermal rapid sintering). This layer-by-layer construction allows for good control over both the layer thickness and the morphology.

[0081] Using the process route developed here, it is possible to quickly create porous structures, such as those advantageous for electrochemical sensors or SOFCs, or dense structures, such as those advantageous for the production of heating coils. The rapid thermal sintering process is adapted to the final application or function of the layers. For example, the YSZ top layer should be relatively porous, a YSZ electrolyte for fuel cells should be rather dense, and the YSZ electrolyte for SOFCs or sensors should be rather porous. This process route can be used to produce electrochemical solid electrolyte sensors that exhibit long-term stability of over 1,000 hours and a response time of less than 4 seconds (in some cases even in the range of one second) at pressures of 1 x 10' 4 mbar enable.

[0082] An example of a manufacturing process is described below:

[0083] A given structure is completely filled with nanoparticle ink. For this purpose, a suitable self-created print pattern with a defined print dot density is selected. However, these settings are highly dependent on the print head, ink, desired structure, etc. The printing time depends on the printer system and the number of sensors to be produced.

[0084] A material-specific sintering process is selected: a) For metallic layers, here e.g. platinum. Initially, Pt layers are printed as a "support layer" and sintered at 600°C (or in some cases up to 900°C, whereby improved adhesion between the platinum layer and the electrolyte or substrate can be achieved, which can be explained by a quasi-baking). This layer is necessary insofar as the subsequent printed layers meet the requirements in terms of print image and electrical conductivity. The printed layers (usually 1 - 3 per step) are placed directly in the furnace at 600°C, i.e. in many cases at the target temperature, sintered for up to 10 minutes, removed at 600°C and cooled to room temperature. This means that the samples can be printed again after just a few minutes (max. 5 min). This process is repeated until the desired layer thickness orthe desired electrical resistance is reached. b) For ceramic layers, here e.g. YSZ. The substrates are printed with the ceramic ink and placed in the furnace at 600°C. The heating rate is selected as high as possible (e.g. 1600°C / h) so that the printed layers reach the material-specific target temperature of 950°C (for YSZ) as quickly as possible. The layers are sintered for up to 15 minutes and, after an internal cooling process at 600°C (max. 15 min), removed from the furnace and cooled further at room temperature. This means that the samples can be printed again after just a few minutes (max. 5 min). This process is repeated until the desired layer thickness is reached.

[0085] The oxygen sensors manufactured using the presented process currently consist of a heating coil (platinum, 5-15 layers), an electrode (platinum, 5-10 layers), and an electrolyte (YSZ, 5-10 layers). With a total of 15 layers, each lasting approximately 35 minutes, the maximum printing time is estimated at 8 hours 45 minutes. In principle, the production of solid electrolyte sensors (FES) using the presented process can be achieved in a total of 12 hours.

[0086] In summary, the core of the invention can be seen in the process route, which for the first time made it possible to produce sensors with sufficient sensor signals and temporal resolution for vacuum applications. The entire process was newly developed and, in a first step, designed for the production of electrochemical solid electrolyte sensors. Another key feature is the simple and accelerated production method, which results in the printing of the individual layers and the accelerated sintering step (thermal rapid sintering). A key feature of the developed process is the method of layer-by-layer printing with a suitable dot density in combination with the subsequent rapid sintering process for the production of, for example,

[0087] Solid electrolyte sensors. The layer-by-layer printing process allows the functional materials (here, YSZ and Pt) to be applied with good layer thickness control. Combined with the rapid sintering process, it enables the production of porous, uniform layers of the printed materials in a short time.

[0088] Finally, it should be noted that terms such as "comprising", "comprising", etc. do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps which are mentioned with reference to one of the above

[0089] Embodiments have been described, can also be used in combination with other features or steps of other embodiments described above. Reference symbols in the claims are not to be construed as

[0090] restriction.

[0091] List of reference symbols

[0092] I electrical component

[0093] 3 Substrat

[0094] 5 first layer

[0095] 7 Ink

[0096] 9 particles

[0097] II further layer

[0098] 11 ' further layer created with ink with ceramic particles

[0099] 11" additional layer created with ink with metallic particles

[0100] 13 layer stacks with ceramic material

[0101] 15 layer stacks with metallic material

[0102] 16 total stacks

[0103] 17 Electrode

[0104] 19 Solid electrolyte layer

[0105] 21 inkjet head

[0106] 23 gap

[0107] 25 layer stacks with metallic material

[0108] 27 heating coil

[0109] 29 Gas sensor

Claims

Claims 1. A method for producing an electrical component (1), comprising at least the following steps: (a) providing a substrate (3), (b) printing a first layer (5) of an ink (7) onto the substrate (3), wherein the ink (7) comprises a flowable binder and a plurality of particles (9) of a metallic, metal oxide and / or ceramic material embedded in the binder, (c) sintering the substrate (3) including the first layer (5) of ink (7) at a temperature above 300°C for a period of time in a range of 1 minute to 1 hour, (d) printing a further layer (11) of an ink (7) onto the substrate (3), wherein the ink (7) comprises a flowable binder and a plurality of particles (9) of a metallic and / or ceramic material embedded in the binder, (e) sintering the substrate (3) including the further layer (11) of ink (7) at a temperature above 300°C for a period of time in a range from 1 minute to 1 hour, wherein steps (d) and (e) are repeated with a plurality of repetitions.

2. The method according to claim 1, wherein in the repetitions the substrate (3) is sintered at least once at a temperature above 500°C.

3. Method according to one of the preceding claims, wherein the sintering time in at least one of the sintering steps, preferably in all sintering steps, is shorter than 20 minutes.

4. Method according to one of the preceding claims, wherein the substrate (3) consists of an inorganic material, in particular a ceramic material or a semiconductor material, and / or wherein the substrate (3) consists of an electrically insulating material.

5. Method according to one of the preceding claims, wherein the sintering is carried out by introducing the substrate (3) into an oven preheated to at least 300°C immediately after the printing of the respective layer (5, 11), in particular without prior drying and / or compacting of the printed layer (5, 11).

6. Method according to one of the preceding claims, wherein the sintering is carried out without the substrate (3) being surrounded by a protective gas atmosphere and / or without an electrical voltage being applied to the substrate (3).

7. Method according to one of the preceding claims, wherein the particles (9) in the ink (7) are nanoparticles.

8. Method according to one of the preceding claims, wherein the first and / or the further layers (5, 11) are printed in such a way that they have a layer thickness of between 5 pm and 60 pm after printing and before sintering.

9. Method according to one of the preceding claims, wherein the substrate (3) is cooled to ambient temperature before printing each of the further layers (11).

10. Method according to one of the preceding claims, wherein the first layer (5) and, optionally, one or more of the further layers (11') are printed directly adjacent to the first layer (5) with an ink (7) which comprises particles (9) of a ceramic material.

11. The method according to claim 10, wherein at least one of the further layers (11") is printed with an ink (7) which comprises particles (9) made of a metallic and / or a metal oxide material.

12. The method according to claim 11, wherein a multi-layer overall stack (16) is formed from alternating at least two layer stacks (13) with ceramic material and at least two layer stacks (15) with metallic material, wherein each of the layer stacks (13) with ceramic material is formed by printing the first layer (5) and / or one or more of the further layers (11') directly adjacent to one another with an ink (7) which comprises particles (9) of a ceramic material, and wherein each of the layer stacks (15) with metallic material is formed by printing one or more of the further layers (11") directly adjacent to one another with an ink (7) which comprises particles (9) of a metallic and / or a metal oxide material.

13. Method according to one of the preceding claims, wherein at least one of the further layers (11) is printed in the form of a pattern which depicts two electrodes (17) laterally spaced from one another.

14. Electrical component (1), in particular a sensor or solid oxide fuel cell, comprising: a substrate (3), and a plurality of layers (5, 11) made of a metallic, metal oxide and / or ceramic material applied to the substrate (3), wherein each of the layers (5, 11) is produced by printing an ink (7) which comprises a flowable binder and a plurality of particles (9) made of a metallic, metal oxide and / or ceramic material embedded in the binder, and subsequently sintering the ink at above 300°C.

15. Electrical component (1) according to claim 14, wherein the component (1) is manufactured by means of a method according to one of claims 1 to 13.

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