WO2003049500A2

WO2003049500A2 - Method and device for producing an electrical strip conductor on a substrate

Info

Publication number: WO2003049500A2
Application number: PCT/EP2002/012969
Authority: WO
Inventors: Karsten Wermbter; Andreas Killinger; Chuanfei Li; Wolfgang Hinreiner; Rainer Gadow
Original assignee: Schott Glas; Carl-Zeiss-Stiftung; Carl-Zeiss-Stiftung Trading As Schott Glas
Priority date: 2001-12-05
Filing date: 2002-11-20
Publication date: 2003-06-12
Also published as: WO2003049500A3; DE10160451A1; AU2002356680A8; AU2002356680A1

Abstract

The invention relates to a method and a device for producing an electrical strip conductor (16, 17), especially a surface heat conductor, on a substrate (14). According to the invention, an electroconductive material is sprayed onto the substrate (14), by means of thermal spraying, preferably by means of plasma spraying, using a torch (18), the torch (18) and the substrate (14) being displaceable in relation to each other. The geometric form or the longitudinal direction of the strip conductor (16, 17) produced and/or the electroconductivity of said strip conductor (16, 17) can be topically varied by adapting the spraying parameters and/or the relative speed or direction of the torch (18) in relation to the substrate (14) and vice versa in a targeted manner during the spraying process.

Description

Method and device for producing an electrical conductor track on a substrate

The invention relates to a method for producing an electrical conductor track, in particular a surface heating conductor, on a substrate, in which an electrically conductive material is sprayed onto the substrate by means of a burner by thermal spraying, preferably by plasma spraying, while the burner and substrate are moved relative to one another ,

The invention further relates to a suitable device for carrying out the method according to the invention.

In the development of hobs with energy-saving direct heating, the focus is on cooking systems in which the heating conductors are applied directly to the underside of the hob, possibly with an insulating layer interposed. In this way, the losses are avoided which were previously associated with conventional cooktops with heating by radiators provided at a distance from the hotplate, in which the energy transfer to the hotplate takes place essentially through radiant energy. The parboiling performance and the control behavior can thus be significantly improved.

Such a cooking system is known, for example, from EP 0 853 444 A2.

Here, the hob consists of a contact heat-transferring electric hotplate, which consists of a non-oxide ceramic, in particular silicon nitride, on the underside of which a heating resistor is applied. The heating resistor can be designed as a thick-film heating resistor formed from a printed paste or as a thin-film heating resistor. The heating resistor can be applied by a thermal spraying method such as flame or plasma spraying, an electrical insulation layer, for example made of aluminum oxide, being applied between the hotplate body and the heating resistor. The production of such cooking systems is simplified by the application of the heating conductor by thermal spraying.

In modern hotplate systems, however, special requirements are placed on the distribution of the heating conductors on the hob. Special surface designs for the base area to be heated, such as circular, square, segmented, etc., are required. Furthermore, a variable power input in different segments or areas of a heating zone is desirable. Different segments or zones of the area to be heated are equipped with different heating capacities.

In order to produce such specially adapted heating conductors by thermal spraying on a substrate, complex masking methods have to be used. Furthermore, different heating conductor materials sometimes have to be used in order to produce certain heating zones with a higher electrical resistance and other heating zones with a lower electrical resistance. A whole series of requirements are placed on the radiators for use in cooking systems, such as permanent temperature resistance up to about 600 ° C, oxidation resistance, high power densities, homogeneous power densities, and a high degree of occupancy. Of particular importance is a variable surface design of the heating conductor and a variable power input in different segments of the cooking zone.

The latter requirement can be met by different specific sheet resistances or different geometries of the heating layers (ratio of length to cross section of the Conductor). For this purpose, meandering conductor tracks are printed on printed thick-film heaters with silver conductive pastes. The resistance and thus the performance of the meandering tracks can be influenced by the conductor or meander length, the conductor cross section and the proportion of the conductive component in the conductive paste.

According to EP-A-0 861 014, a heating system with multiple sub-segments is disclosed, in which the heating conductor consists of an enamel, which is applied to the substrate by means of a screen printing technique.

The lack of thermal stability at operating temperatures between 400 and 500 ° C has proven to be a disadvantage here. The layers applied by screen printing contain a glassy part in addition to the metallic conductor, so that the flow temperatures during the layer penetration can be reduced. The low-melting glass solders in the mixture of the paste ensure that a sealed, closed conductor layer is formed at baking temperatures of around 650 ° C. However, the operating temperature and the baking temperature are close to one another, so that the glass portions during operation are close to the softening point, which affects the stability. The presence of the glass frit further reduces the metallic, conductive portion. Sub-segments of the conductor track that have a higher proportion of glass locally are areas with higher resistance. If the current flows through, overheating and material failure may occur. In addition, such heating conductors can cause cracking when the conductor pastes are burned in. Against this background, the object of the invention is to create a method and a device for producing an electrical conductor track, in particular a surface heating conductor, on a substrate, with which the disadvantages of the prior art are avoided. In particular, the geometry and the electrical resistance of the generated conductor track should be adaptable to the respective system specifications within the broadest possible limits. The production should be as simple and inexpensive as possible.

This object is achieved according to the invention by a method for producing an electrical conductor track, in particular a surface heating conductor, on a substrate, in which an electrically conductive material is sprayed onto the substrate by means of a burner by thermal spraying, preferably by plasma spraying, while the burner and substrate are relative are moved towards each other, a local variation of the geometric shape or the direction of extension of the conductor track produced and / or the electrical conductivity of the conductor track produced being achieved by a targeted adaptation of the spray parameters and / or the relative speed or direction between substrate and burner during the spraying process.

The object of the invention is completely achieved in this way.

With the method according to the invention, an electrical conductor track can be produced by thermal spraying on a substrate, which is a particularly inexpensive and reliable method. The trace created When using a suitable electrically conductive material, it is sufficiently resistant to oxidation and high temperatures so that it can also be used at operating temperatures of up to 500 ° C or more, as can occur in cooktops. Without the need for various electrically conductive materials or special masking processes, the desired geometric variations in the shape, the cross section and the direction of extension of the ^' conductor track produced and, if appropriate, the electrical conductivity of the conductor track produced can be achieved directly by thermal spraying during manufacture.

This represents a significant improvement over conventional methods. In particular, the layer thickness and width can be adjusted by the relative speed between the burner and the substrate, so that the electrical resistance of the conductor track obtained can be varied locally. In this case, rectilinear, angled or curved conductor tracks can also be produced.

The object of the invention is further achieved by a device for producing electrical conductor tracks, in particular heating conductor tracks on a substrate, with a substrate holder for receiving the substrate with a burner for applying electrically conductive material by thermal spraying, preferably by plasma spraying, to the substrate , with a burner holder on which the burner is held, at least one of the two holders having drive means for moving the holder relative to the other holder, and with a control device which has means for entering and storing a program, and wherein the Control device is at least coupled to the burner or the drive means to program controlled at least the movement of the drive means or the setting of spray parameters, such as the feed rate of electrically conductive material to the burner, the distance of the burner from the substrate or the gas flow ratio of gases supplied to the burner change.

When using such a device, the advantages of the method according to the invention can be used in a wide variety of ways.

Here, for example, the burner can be accommodated on a robot, by means of which the burner can be moved in a controlled manner relative to the substrate.

Alternatively, it would in principle also be conceivable to move the substrate relative to the burner by means of an automatic control in at least one axis with respect to the burner.

However, the use of a robot system for the controlled method of the burner is considered to be simpler and more advantageous. It goes without saying that instead of using a robot system, any other drive systems can also be used, provided that these enable controlled movements in at least one axis. For example, one or more controlled, drivable linear axes can be coupled to one another in order to achieve the desired movement of the burner. If the relative speed between the burner and the substrate is changed, the layer thickness and the layer width of the interconnect produced can be influenced.

If necessary, the distance between the burner and the substrate can additionally be changed within certain limits, as a result of which the width of the interconnect produced is influenced.

Furthermore, by changing the feed rate of the electrically conductive material to the burner during the spraying process, the layer thickness or layer width of the conductor track generated can be influenced.

If a larger width or height of a conductor track has to be produced than can be achieved with a single spray application, the conductor track can at least partially be run over several times in order to spray on electrically conductive material. In this way, larger layer thicknesses and widths can be produced.

According to a further embodiment of the method according to the invention, at least two adjacent conductor tracks are injected without masking the substrate lying between them.

Surprisingly, it has been shown that the overlapping spray mist between adjacent conductor tracks is not electrically conductive if the distance between the conductor tracks is chosen to be large enough.

If the burner moves sufficiently fast between adjacent conductor tracks that should not come into contact with one another, the spraying process does not even have to be interrupted in order to produce conductor tracks at different points on the substrate in one operation, which are not in contact with one another. This represents a considerable simplification of the manufacturing process.

It goes without saying that the features of the invention mentioned above and those yet to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own without departing from the scope of the present invention.

Further advantages and features of the invention result from the following description of preferred exemplary embodiments with reference to the drawing. Show it:

Fig. 1 is a schematic representation of a device according to the invention;

Figure 2 shows a meandering radiator, which is made with the inventive method.

Fig. 3 shows a hob with a plurality of radiators produced according to the invention and

Fig. 4 shows a tubular body with radiators produced according to the invention.

In Fig. 1, a device according to the invention is shown purely schematically and generally designated by the number 10. The device 10 has a substrate holder 12 in which it can be, for example, a table or another suitable surface. A substrate 14 is placed on the substrate receptacle 12 and is to be coated with one or more electrical conductor tracks. In the preferred area of application, the substrate 14 is a plate made of glass ceramic or glass for a ceramic hob, to which electrical conductor tracks, in particular heating conductor layers, are to be applied by thermal spraying. The substrate 14 can thus be, for example, a glass ceramic, such as CERAN®, onto which the heating conductor layers are to be sprayed. As is known, such a glass ceramic has an NTC characteristic, ie the electrical conductivity increases noticeably as the temperature rises. It is therefore necessary to first apply a ceramic insulating layer, for example made of aluminum oxide, to the substrate surface before applying electrical conductor tracks or radiator surfaces, which can also be done by thermal spraying. In the case shown, it is assumed that before the application of electrical conductor tracks at the relevant points, a suitable ceramic insulating layer has already been applied, preferably by thermal spraying with a suitable layer thickness of, for example, 100 to 500 μm.

In the case shown, so-called atmospheric plasma spraying is used both for the application of ceramic insulating layers or adhesion promoter layers, for example made of Al ₂ O ₃ , and for the production of electrical conductor tracks on the surface of the substrate. In plasma spraying, a plasma torch usually burns between a rod-shaped tungsten electrode and a water-cooled copper anode in a gas atmosphere (nitrogen / hydrogen; argon / hydrogen; Argon / Helium) an arc with a high energy density. The arc is ignited at high frequency. Due to the thermal energy of the arc, the plasma gas is ionized. When the ions recombine to form neutral gas molecules, heat energy is released and an electrically neutral plasma jet leaves the anode at high temperature and speed. Using a conveying gas, powdered spray is introduced into the plasma flame, melted, accelerated and sprayed onto the surface to be coated with high kinetic energy.

Such a plasma torch for the plasma spraying process is indicated purely schematically in FIG. 1 with the number 18. The burner 18 is received on a robot arm 22 of a robot 20. This enables the burner 18 to be moved on optionally curved or linear paths in the x direction, y direction and z direction in a numerically controlled manner. Depending on the desired requirements, it can be an articulated arm robot whose robot arm 22 can be pivoted in a controlled manner about several axes, so that both movements on curved paths and movements on linear movement paths can be achieved as a result of the superimposition of several pivoting movements. Alternatively or in addition, one or more controlled linear axes can also be provided. In any case, the robot arm 22 or the burner receptacle formed in this way is designed such that the burner 18 can be moved in a controlled manner at least in one plane in the x and y directions, preferably additionally perpendicular to it in the z direction. In Fig. 1, a supply line, which comprises a whole bundle of individual lines for the burner 18, is shown simply with the number 26. This is a gas line for the supply of argon or another inert gas, as well as a further gas line for the supply of hydrogen, and a carrier gas line for the gas-assisted supply of the pulverized spray material to the burner 18. The individual lines for the plasma gas supply (Ar and H ₂ ) are indicated schematically with the numbers 28 and 32 and provided with suitable controllable metering valves 30 and 34, respectively. A corresponding line branch of the carrier gas line for the supply of the powdered spray material is also indicated by the number 40 and provided with a suitable controllable metering valve 42.

The device 10 further comprises a central control device 24 with which the movement of the burner 18 relative to the surface of the substrate 14 can be controlled and at the same time the most important spray parameters of the burner 18 can be controlled. These include the distance of the burner 18 from the substrate surface 14, which is already predetermined by controlling the movement of the robot arm 22, the gas flow ratio between argon and hydrogen, the feed rate for the spray material, ie the powder feed rate, and the substrate temperature, which may be by cooling or heating can be affected. The central control device 24, which can be, for example, a PLC control, controls at least the movement of the robot arm 22 and, if necessary, additionally individual of the spray parameters. The control device 24 naturally has suitable input and storage means 25, a suitable processor device and interfaces. In the The control device 24 can be a control integrated in the robot 20, but also an additional external or possibly PC-based control. In FIG. 1, control lines 36, 38, 44 for controlling the metering valves 30, 34, 42 for the two plasma gas lines 28, 32 and carrier gas line 40 for the powder supply are indicated purely schematically.

According to the method according to the invention, the movement of the burner 18 during the plasma spraying process relative to the surface of the substrate 14 is now controlled in a program-controlled manner, it being possible for individual spraying parameters to be regulated simultaneously. In this way, the geometry of the conductor tracks generated, i.e. in particular in width and height, to be adapted to the desired specifications, it being possible at the same time to produce any straight, curved or even three-dimensionally curved conductor tracks.

As is known, the electrical resistance of a conductor R results from the formula R = (pxl) / A with p = specific resistance of the material, 1 = conductor length and A = conductor cross-section. Hence R = (pxl) / (wxh), with b = conductor width and h = conductor height.

In order to be able to locally vary the electrical resistance, in particular of electrical conductor tracks which are used for panel radiators on cooktops, the width and the height of the respective conductor track produced are accordingly adapted accordingly. The trace width created with the spray jet can be adjusted by selecting the type of plasma torch and the distance between the torch and the substrate. There the distance between the burner and the substrate should generally not be changed in order to maintain a desired optimized oxidation behavior in the production of the conductor track in question, in particular the feed rate and the powder conveying rate are controlled in order to be able to specifically adjust the layer thickness of the conductor track produced. In addition, of course, any geometries of conductor tracks can be sprayed, for example meandering conductor tracks, which are particularly preferred in particular for heating conductors on cooking systems. As coating materials for the production of heat conductor surfaces, for example on hobs, so-called heat conductor alloys are preferred in particular for operating temperatures up to approximately 1200 ° C. These are primarily nickel-chrome base alloys (e.g. 2.4658) and chrome-aluminum base alloys (e.g. 1.4725) with additives made of aluminum, copper, iron and silicon. These materials are summarized in the steel key under material group 12 (heat-resistant steels, heating alloys). All of these alloys can be thermally sprayed.

For the highest oxidation resistance requirements, quaternary alloys, so-called M-CrAlY materials, are thermally sprayed, with M = Ni, Co, Cr, Fe or alloys such as FeCo; CoCr. Traces of refractory metals such as Hf and Ta can be added to further increase the resistance to oxidation.

In general, however, the heating conductor materials for the illustrated application on hot plates or tubular heaters are those mentioned above _. n Sufficient nickel-chrome base alloys and chrome-aluminum base alloys. By a suitable process control, the oxidation of the sprayed metal material that always occurs to a certain extent during atmospheric plasma spraying is kept as low as possible. The oxidation process can be divided into two phases, namely the oxidation during the particle flight phase and the oxidation during the solidification phase on the substrate.

The particle oxidation in the flight phase is significantly influenced by the spray parameter setting. The most important measures against oxidation are preventing particle melting through (adjustable e.g. via the particle size in the wettable powder) as well as reducing the particle flight time or increasing the particle speed. This can be achieved in plasma spraying by adjusting the gas flow ratio between argon and hydrogen. The hydrogen content also essentially determines the energy density in the gas and thus the thermal energy transferred to the particle in the flight phase.

The spraying distance also plays an important role. If the spraying distance is too large, the particle oxidation increases because the atmospheric oxygen introduced into the plasma flame by swirling effects favors the oxidation of the hot layer surface. In contrast, if the spraying distance is too large, the particle flight time increases, which favors the oxidation due to the longer residence time of the particle in the hot plasma zone. Compared to the spray distance, the powder feed rate and the feed gas flow have less influence on the particle oxidation. An increasing powder delivery rate usually leads to reduce oxidation, but also to significantly increase the internal stress due to the high application rate.

The most important influencing factors for the oxidation in the solidification phase are substrate temperature and cooling. If the substrate temperature remains low during the coating process, the layer is less oxidized. Furthermore, the use of nitrogen as an auxiliary cooling instead of compressed air significantly reduces the oxidation in the layer.

In order to be able to set the resistances of the conductor tracks applied by thermal spraying in a targeted manner, as already mentioned above, the width and height of the conductor tracks generated are adjusted in particular by adjusting the feed speed and feed direction, and if necessary by adjusting the powder feed rate and the burner spacing set. The electrical resistance of the conductor track generated can be seamlessly set differently for different layer segments. If the extent of the change in resistance is too small, an additional change in resistance can optionally be achieved by changing the gas flow ratio of gases supplied by the burner, for example by changing the ratio of argon to hydrogen. As a result, the oxide content in the layer can be changed in this way and thus the electrical resistance can be changed locally.

With a corresponding movement program, three-dimensional substrates can also be provided with electrical conductor track structures with a homogeneous structure. The particle density of the spray jet emerging from the burner decreases during plasma spraying in the edge zone of the coating cone. At right angles to the direction of travel, a spray mist is created when the layer forms, which is also known as overspray. Investigations have shown that, surprisingly, this overspray is not electrically conductive since it does not produce a coherent conductor strip. It is therefore not necessary to use a mask for separating the individual meander segments to produce a meandering heating conductor structure, for example, if conductors lying next to one another, as indicated by conductor tracks 16 and 17 in FIG. 1, have a sufficiently large distance. With a correspondingly high feed rate of the burner, a particle distribution with large intergranular distances is created instead of a layer. Thus, at a high feed rate of the burner, no coherent conductor strip is produced, but only particles that are isolated from one another.

In this way, heating zones or surfaces which are spatially separate from one another and which are not connected to one another in an electrically conductive manner can be produced. Thus, the particle flow in the coating process need not be interrupted. Masking of the areas of the substrate surface that are not to be coated can optionally be dispensed with. Nevertheless, the use of masks can be useful for certain areas, if heating conductors with a more constant thickness profile in relation to the cable cross-section are desired. The current density is more constant over the entire cross-section of the conductor than with a layer application without a mask. The conductor resistance can be set via the layer thickness. If greater layer thicknesses are to be produced that cannot be achieved with a single pass, individual conductor tracks or conductor track sections can of course be run over several times.

FIGS. 2 to 4 show examples of some panel radiators that can be manufactured seamlessly by plasma spraying using the method according to the invention or with the device according to the invention.

In Fig. 2, a meandering panel radiator with two contactable heating circuits of different power is designated by the number 50. The radiator 50 can be deposited in a continuous plasma spraying process without using a mask. It has two heating circuits, a first heating circuit between the connections 51 and 52 with a first output, and a second heating circuit between the connections 52 and 53 with a second output. The surface heating element 50 consists consistently of the same heating conductor material and can be sprayed without using a template.

In Fig. 3 a hob is shown schematically with the number 64. The hob 64 has a glass ceramic plate made of CERAN®, on the underside of which a plurality of radiators is produced by plasma spraying with the interposition of a ceramic insulating layer, which can be made of aluminum oxide, for example.

In Fig. 3 are a first meandering heater 54, a second meandering heater 56 for a larger cooking vessel diameter and a third meandering heater 58 shown for a smaller cooking vessel diameter. In addition, two rectangular radiators 60, 62 are shown, which serve as warming zones with lower output.

All of the radiators 54, 56, 58, 60, 62 can be sprayed without using a mask and without interrupting the material flow. There is no electrically conductive connection between the individual zones. While the burner 18 moves at low speed when generating the individual conductor tracks, the burner 18 moves during the transition from one heater to the next, for example during the transition from the heater 54 to the heater 56 at high speed, as a result of which no coherent interconnect is produced in the intermediate space on the substrate, but rather only particles which are isolated from one another are deposited.

A tubular body 66 with a cylindrical surface is shown purely schematically in FIG. 4. This can be, for example, an oven muffle, a gas dryer or a fluid heater, which consists of glass, glass ceramic or ceramic (for example A1 ₂ 0 ₃ ). Radiators 68, 70 of the desired shape and structure can also be produced on such a tubular body 66 with the method according to the invention, provided that a suitable three-dimensionally controlled displaceability and, if appropriate, pivotability of the burner is made possible.

Claims

claims

1. A method for producing an electrical conductor track (16, 17), in particular a surface heating conductor, on a substrate (14), in which an electrically conductive material by thermal spraying, preferably by plasma spraying, by means of a burner (18) on the substrate (14) is sprayed on while the burner (18) and substrate (14) are moved relative to one another, with a specific adjustment of the spraying parameters and / or the relative speed or direction between the substrate (14) and the burner (18) during the spraying process local variation of the geometric shape or the direction of extension of the conductor track (16, 17) and / or the electrical conductivity of the conductor track (16, 17) produced is achieved.

2. The method of claim 1, wherein the burner (18) or the substrate (14) by means of an automatic control (24) are moved relative to each other in at least one axis.

3. The method according to claim 1 or 2, wherein the relative speed between the burner (18) and the substrate (14) is changed in order to influence the layer thickness and layer width of the conductor track (16, 17) generated.

4. The method according to any one of the preceding claims, wherein the feed rate of the electrically conductive material to

4. The method according to any one of the preceding claims, wherein the feed rate of the electrically conductive material to the burner (18) is changed during the spraying process in order to influence the layer thickness and layer width of the conductor track (16, 17) generated.

5. The method according to any one of the preceding claims, wherein the distance between the burner (18) and the substrate (14) is changed during the spraying process.

6. The method according to any one of the preceding claims, in which at least two adjacent conductor tracks (16, 17) are injected without masking the intermediate substrate (14).

7. The method according to any one of the preceding claims, in which at least one conductor track (16, 17) is passed over at least partially several times during the spraying process in order to spray on electrically conductive material.

8. The method according to any one of the preceding claims, in which on the surface of a substrate (14) a plurality of mutually insulated conductor tracks (16, 17) is produced without masking the substrate (14), the burner (18) between the different, interconnects (16, 17) insulated from one another travels at high speed without the spray jet of the burner (18) being interrupted.

9. Device for generating electrical conductor tracks (16, 17), in particular heating conductor tracks, on one Substrate (14), with a substrate holder (12) for receiving the substrate (14), with a burner (18) for applying electrically conductive material by thermal spraying, preferably by plasma spraying, onto the substrate (14), with a burner holder ( 22) on which the burner (18) is held, at least one of the two receptacles (12, 22) having drive means for moving the receptacle (22) relative to the other receptacle (12), and with a control device (24) which Has means (25) for entering and storing a program, and wherein the control device (24) is coupled at least to the burner (18) or the drive means to at least the movement of the drive means or the setting of spray parameters, such as the feed rate of electrical conductive material to the burner (18), the distance of the burner (18) from the substrate (14) or the gas flow ratio of gases supplied to the burner (18) to be changed in a program-controlled manner.

10. The device according to claim 9, with a robot (20) on which the burner (18) for the controlled movement of the burner (18) relative to the substrate (14) is received.

11. Use of a device according to claim 9 or 10 for the production of panel radiators (50; 54, 56, 58, 60, 62; 68, 70) on cooktops (64) or tubular bodies (66), such as tubular heaters for fluids or furnace muffles ,

12. substrate with a surface on which at least one electrical conductor track (16, 17) is provided, which according to a method according to one of claims 1 to 8 is produced.