Method for producing a resistor arrangement

Abstract

The invention relates to a method for producing a resistor arrangement (1) comprising the following method steps: a) providing a substrate (2) made of a conducting material, b) applying a resistor material (3) to the substrate (2) by means of an additive method so that a resistor element (31) is formed, c) separating the substrate (2) so that at least two separate connection elements (21, 22) that are physically separated from one another are formed from the substrate (2) for connecting the resistor arrangement (1) to an external circuit.

Description

[0001] Description

[0002] Method for producing a resistor arrangement

[0003] The invention relates to a method for producing a resistor arrangement.

[0004] Current measurements in electronic circuits are carried out using measuring resistors connected in series with the component to be monitored. The current is determined according to Ohm's law from the voltage drop across the measuring resistor, known as the shunt resistor. The value of the resistor is assumed to be known. Accurate and reliable current measurement is particularly important, for example, in the battery management system of an electric or hybrid vehicle.

[0005] A resistor assembly comprising such a low-ohm measuring resistor of approximately 10 to 50 pOhm and connecting elements for connecting the resistor assembly to the circuit can be manufactured from a longitudinally welded composite material by transversely dividing this composite material. This is known, for example, from document EP 0605 800 A1. The composite material is manufactured from three metal strips, each of which is joined to one another via a longitudinal seam using an electron beam or laser welding process. The middle metal strip consists of a material with a very low temperature coefficient of resistance. This material forms the actual resistance element of the measuring resistor. The two outer strips are usually made of a material with high electrical conductivity, for example, copper or aluminum.Such materials usually have a high temperature coefficient of resistance compared to the material of the resistance element. These two outer bands form connection elements through which the measuring resistor can be connected to an electrical circuit.

[0006] This manufacturing process is advantageous when resistor arrays are produced in large quantities and within a specific dimensional range.

[0007] There is a growing demand for the production of resistor arrays in small quantities and in a wide variety of dimensions. By varying the width, length, and / or thickness of the resistor element, it is possible to achieve widely varying resistance values. In particular, resistance elements with a thickness of more than 4 mm are required to measure high currents. Longitudinal seam welding processes are no longer suitable for the production of resistor arrays with such resistor elements due to the limited penetration depth of the electron or laser beam, meaning that the resistor array cannot be manufactured using the process known from EP 0 605 800 A1.

[0008] The invention is based on the object of specifying a method for producing a resistor arrangement with a resistor element and connection elements, wherein the method can be used in a wide range of dimensions, in particular for resistor elements with a thickness of greater than 4 mm, and is economical even for small quantities.

[0009] The invention is defined by the features of claim 1. The further dependent claims relate to advantageous embodiments and developments of the invention. The invention relates to a method for producing a resistor arrangement with at least two connection elements and at least one

[0010] Resistor element, the method comprising the following method steps: a) providing a substrate made of a conductor material, b) applying a resistor material to the substrate by means of an additive method so that a resistor element is formed, c) separating the substrate so that at least two separate, spatially separated connection elements for connecting the resistor arrangement to an external circuit are formed from the substrate.

[0011] The resistor arrangement manufactured according to the method described above can comprise a shunt resistor with a resistance of 10 to 100 pOhm as the resistance element. Both the resistance element and the connection elements are made of electrically conductive materials. The specific electrical resistance of the resistance material, i.e., the material of the resistance element, is at least a factor of 10 greater than the specific electrical resistance of the conductor material, i.e., the material of the connection elements. On the other hand, the temperature coefficient of resistance of the conductor material is much larger, typically at least a factor of 80 greater than the temperature coefficient of resistance of the resistance material. Typically, the temperature coefficient of resistance of the resistance material is less than 5 10' 5 1 / K, while the resistance temperature coefficient of the conductor material is approximately 4 10'3 1 / K. The connection elements of the resistor arrangement can be made, in particular, of copper, a preferably low-alloy copper alloy, aluminum, or a preferably low-alloy aluminum alloy, or can comprise at least one of these materials. The resistance element can be made of a copper alloy that is commonly used as a resistance alloy.

[0012] The substrate provided in process step a) is preferably formed in one piece and monolithically. The substrate can have any geometric shape. In particular, it can be band- or strip-shaped, i.e., flat. Alternatively, it can also have a shape that has a recess for receiving the resistor material in step b), for example, an LI shape or a trough shape. The substrate can be made from a semi-finished product, for example, from a rolled strip or a pressed profile. Alternatively, the substrate can also be produced by means of a primary forming process, for example, by casting or by a powder metallurgical process. The substrate can have regions that serve to electrically contact the resistor arrangement. Means, in particular bores, can be provided in these regions, through which the resistor arrangement can be connected to an external circuit.

[0013] In process step b), a resistance material is applied to the substrate using an additive process. This creates a resistance element. In an additive process, the material to be added to a substrate is applied to the substrate without the use of tools, and a metallurgical bond is created between the substrate material and the applied material. The applied material forms a layer on the substrate, the thickness of which is typically 0.2 to 1 mm. To create a resistance element with a greater thickness, the resistance material is applied in multiple layers.

[0014] Advantageously, during process step b), the substrate can be heated locally, i.e., at a specific location, with an energy source, for example, a laser beam, to briefly melt the substrate material at this point on its surface. The resistance material is then introduced into this melt and briefly melts itself. This creates a particularly good metallurgical bond between the substrate and the resistance material. In a similar manner, a previously applied layer of the resistance material can also be heated to ensure a good metallurgical bond between this layer and another layer of the resistance material.

[0015] In process step c), the substrate is separated into at least two spatially separated sub-regions. In particular, the conductor material of the substrate is separated into at least two spatially separated sub-regions. The separation takes place in such a way that two sub-regions of the substrate are no longer in direct electrical contact, but are only electrically connected to one another via the resistance material. In other words: by separating the substrate, spatially separated sub-regions are first formed from the substrate. These sub-regions then form connection elements for connecting the resistance arrangement to an external circuit. By separating the substrate, it is achieved that when current flows through the resistance arrangement, the current flows from one connection element through the resistance element formed from the resistance material to the other connection element.The separation can be achieved, for example, by creating a slot or recess using longitudinal milling. The slot or recess can also be filled with an electrically insulating material to improve the mechanical stability of the resistor arrangement.

[0016] The particular advantage of the proposed process is that it can be used to manufacture resistor arrays in a wide range of dimensions. It can therefore respond flexibly to geometric requirements depending on individual customer needs. In particular, the thickness of the resistor element and thus the resistance value of the measuring resistor can be varied within a wide range. The starting materials required for the process are available. Established equipment and processes can be used. The dimensions of the resistor array can be quickly varied by changing the process parameters. Significant changes to the equipment and tools are not required for this. Therefore, the process is particularly suitable for the economical production of resistor arrays in small quantities.Furthermore, the additive process used in process step b) has the advantage that only the material required to produce the finished resistor assembly is used. The use of a binder, as is the case with metal powder injection molding, is unnecessary.

[0017] Within the scope of one embodiment, the additive process in step b) can be cold gas spraying or flame spraying. These processes enable the production of a particularly homogeneous resistance material that also exhibits few defects, such as segregation and pores. The transition between the substrate material and the applied resistance material is very sharp. There is only a very narrow zone in which material mixing occurs.

[0018] Within the scope of a specific embodiment of this method, at least one powder can be used as the starting material in process step b) to apply the resistance material. By using powder as the starting material, a resistance material of particularly high quality can be applied.

[0019] In particular, when using powdered starting materials, the additive process can be high-velocity flame spraying. In this process, a heated process gas, such as nitrogen or helium, is accelerated to supersonic speed, and the powder particles are then injected into the gas jet. The injected particles are accelerated to such a high speed that, unlike other thermal spraying processes, they form a dense and firmly adhering layer. The kinetic energy at the moment of impact is insufficient to completely melt the particles. The advantage of this process is that the substrate does not need to be partially melted or melted.

[0020] In a particularly advantageous refinement of the above-described embodiment, the resistance material can be an alloy of copper and alloying elements, and in process step b), individual powders can be used for the copper and for the alloying elements. Manganese, iron, and nickel are particularly suitable as alloying elements. By using powders that each consist of only one element for the components of the alloy, the alloy composition can be varied within a wide range without great effort. Furthermore, it is even possible to produce a resistance element that has a changing composition, i.e., a gradient in its composition.

[0021] In this particularly advantageous embodiment of the method, the individual powders can be mixed and homogenized to form a powder mixture having the composition of the alloy, i.e., the target composition. This powder mixture is then fed to the device for carrying out method step b). In contrast, it is also possible to feed the respective powders individually to the device for carrying out method step b) and only mix them in the device, for example, in the injector of the device. In an alternative, particularly advantageous embodiment of this embodiment, the resistance material can be an alloy of copper and alloying elements, and in method step b), a powder consisting of particles having the composition of the alloy can be used.For this purpose, the desired alloy can be pre-adjusted in a melting furnace with regard to its chemical composition. After solidification, it can then be processed into powder in a metal powder spraying system. Because the powder particles already have the composition of the alloy, the composition of the resistor material is precisely determined and subject to only very slight fluctuations.

[0022] In contrast, it is also possible that in process step b) a wire-shaped starting material is used to apply the resistance material by wire flame spraying. For this purpose, a bolt with the chemical composition of the resistance material is first cast. The bolt is then processed into a wire using known semi-finished product manufacturing processes. To apply the resistance material, the wire is fed to the wire flame spraying system. There, the wire is melted and atomized in a fuel gas flame. The atomized material is accelerated towards the substrate and cools upon impact with the substrate surface. The advantages of this process variant are that the chemical composition of the resistance material can be adjusted very precisely and that wire is a semi-finished product that can be produced cost-effectively.

[0023] In a further advantageous embodiment of the invention, the substrate can be a U-shaped profile. In this context, a U-shaped profile is understood to mean a shape with a recess or a depression in the substrate. Such a recess can be a groove, for example. In process step b), the recess is filled with the resistance material. The recess serves as a mold for the resistance material. The thickness of the resistance element formed from the resistance material then corresponds to the depth of the recess, and the width of the resistance element is determined by the width of the recess. Using a substrate with such a profile, it is possible to define the dimensions of the resistance element geometrically with great precision.

[0024] Advantageously, the substrate can be a component manufactured using powder metallurgy, for example, by pressing and sintering. Powder metallurgical processes are particularly well suited for the production of components in small batches. The process is very flexible with regard to the geometry of the component. In combination with the additive process in process step b), it is thus possible to produce resistor arrays that cover a very wide range of dimensions using just a few devices.

[0025] The invention is explained in more detail using an exemplary embodiment and the schematic drawings, in which:

[0026] Fig. 1 a cross section of a substrate

[0027] Fig. 2 a cross section of a substrate with resistance material Fig. 3 a resistor arrangement in cross section

[0028] Corresponding parts are provided with the same reference numerals in all figures.

[0029] Fig. 1 shows a cross-section of a substrate 2 made of a conductor material. The substrate 2 has a profile with a flat underside 201. On its upper side 202, the substrate 2 has a recess 4 with a trapezoidal cross-section, so that the profile of the substrate 2 has a substantially U-shape. The U-shape can be formed by introducing a wide groove into a band- or strip-shaped material. The shape of the recess 4 then corresponds to the shape of the groove. Due to the trapezoidal profile of the recess 4, the flanks 41, 42 of the recess 4 are inclined. The inclination promotes the introduction of energy, for example by means of a laser beam, for heating the substrate 2 in the region of the flanks 41, 42 during method step b). The flanks 41, 42 preferably form an angle of at least 120° and at most 140° with the bottom 43 of the recess 4.If the angle is less than 120°, the energy input in the area of ​​the flanks 41, 42 is unfavorable. If the angle is greater than 140°, a large amount of material must be applied in process step b). In the example shown, the substrate 2 consists exclusively of a conductor material, for example, copper, a copper alloy, aluminum, or an aluminum alloy.

[0030] On both sides of the recess 4, the substrate has a section 26, 27 in which the substrate 2 is thicker than in the area of ​​the recess 4. The lateral sections 26, 27 serve to connect the resistor arrangement to an external circuit. For this purpose, both lateral sections 26, 27 each have a bore 23, 24, each indicated by dashed lines.

[0031] Fig. 2 shows a cross-section of a substrate 2 with resistance material 3. This corresponds to the cross-section of the intermediate product after process step b) and before process step c). Resistance material 3 was applied to the substrate 2 using an additive process, so that the recess 4 of the substrate is filled with resistance material 3. In this way, a resistance element 31 was formed. The geometric shape of the resistance element 31 is defined by the shape of the recess 4 in the substrate 2. The dimensions of the resistance element 31, in particular its thickness and width, can thus be determined very precisely by the shape of the recess 4 in the substrate 2. Fig. 3 shows a cross-section of the product after process step c), i.e., a resistance arrangement 1. In process step c), a slot 25 was introduced into the substrate 2 below the resistance material 3. The slot 25 extends as far as the resistance material 3.This split the substrate 2 into two separate sections, forming connection elements 21, 22 for connecting the resistor assembly 1 to an external circuit. If the resistor assembly 1 is connected to an electrical circuit via the two holes 23, 24, the current flows from the first connection element 21 through the resistor element 31 to the second connection element 22. The current can be determined from the electrical voltage drop across the resistor element 31.

[0032] The width of the slot 25 influences the effective resistance value of the resistance element 31. Therefore, the slot 25 should ideally be as wide as the shorter of the two parallel sides of the resistance element 31. On the other hand, the width of the slot 25 influences the mechanical stability of the resistance arrangement 1. Therefore, it may be advantageous to make the slot 25 narrower than the length of the shorter of the two parallel sides of the resistance element 31.

[0033] List of reference symbols Resistor arrangement Substrate Top Bottom Connection element Connection element Bore Bore Slot Side section Side section Resistor material Resistor element Recess Flank Flank Bottom

Claims

Patent claims 1 . Method for producing a resistor arrangement (1 ) comprising the following method steps: a) providing a substrate (2) made of a conductor material, b) applying a resistor material (3) to the substrate (2) by means of an additive method, so that a resistor element (31 ) is formed, c) separating the substrate (2) so that at least two separate, spatially separated connection elements (21 , 22) for connecting the resistor arrangement (1 ) to an external circuit are formed from the substrate (2).

2. Process according to claim 1, characterized in that the additive process in step b) is cold gas spraying or flame spraying.

3. Method according to claim 2, characterized in that in method step b) at least one powder is used as starting material to apply the resistance material (3).

4. Method according to claim 3, characterized in that the resistance material (3) is an alloy of copper and alloying elements and that in method step b) individual powders are used for the copper and for the alloying elements.

5. Method according to claim 3, characterized in that the resistance material (3) is an alloy of copper and alloying elements and that in method step b) a powder is used which consists of particles which have the composition of the alloy.

6. Method according to claim 2, characterized in that in method step b) a wire-shaped starting material is used to apply the resistance material (3).

7. Method according to one of the preceding claims, characterized in that the substrate (2) is a profile with a U-shape.

8. Method according to one of the preceding claims, characterized in that the substrate (2) is a powder metallurgically produced component is.

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