Resistor and method for operating same

Abstract

The invention relates to a resistor (1), in particular a snubber shunt (1) for damping voltage peaks, comprising a resistor element (9) made of a resistor material, wherein the resistor element (9) has a meandering course with at least one deflection region (12) in which the current flow direction is deflected. According to the invention, the resistor element (9) consists, in the deflection region (12), at least partly of a conductor material (e.g. copper) which has a greater specific electrical conductivity than the resistor material such that the current-carrying cross-section of the resistor element (9) in the deflection region (12) consists at least partly of the conductor material.

Description

[0001] DESCRIPTION

[0002] Resistance and operating procedures for it

[0003] Technical field of the invention

[0004] The invention relates to an electrical resistor, in particular a so-called snubber shunt for damping voltage spikes. The invention further relates to an operating method for such a resistor.

[0005] Background of the invention

[0006] Electrical resistors are known from the prior art (e.g., DE 43 39 551 CI) in which a meandering resistive element is arranged on a support element. Such resistors are used not only for current measurement purposes but also as so-called snubber shunts for damping unwanted oscillations and voltage spikes in electrical engineering and electronics.

[0007] However, a disadvantage of the known snubber shunts with a meandering guide for the resistance element is the unsatisfactory durability of the snubber shunts, especially under electrical pulse loads with a high pulse current.

[0008] Description of the invention

[0009] The invention is therefore based on the objective of improving the durability of snubber shunts with a meandering guide for the resistance element.

[0010] This problem is solved by a resistor according to the main claim and an associated operating method.

[0011] The invention is based on the technical and physical insight that the relatively short lifespan of known snubber shunts with a meandering resistance element is caused by temperature peaks (hot spots) that occur in the U-shaped bends of the meandering resistance element. These areas can experience temperature increases of approximately 200 K compared to the average temperature in the resistance element away from the bends. These temperature increases lead to corresponding thermal stress, which reduces the lifespan of known snubber shunts.

[0012] The invention is further based on the technical-physical finding that the disturbing temperature increases (hot spots) in the resistance element in the deflection areas are caused by an uneven current density distribution.

[0013] The invention therefore provides that the resistive element in the deflection area consists at least partially of a conductor material that has a higher specific electrical conductivity than the resistive material from which the resistive element otherwise consists. Thus, in the resistor according to the invention, the current-carrying cross-section of the resistive element in the deflection area consists at least partially of the conductor material. This reduces the average specific electrical resistance in the outer area of ​​the deflection. As a result, the current is directed away from the inner area of ​​the deflection to the outer area, thereby improving the utilization of the resistive element and its available heat capacity, and distributing the power loss more evenly across the entire area.

[0014] In the resistor according to the invention, the resistive element preferably runs in a plane of resistance, as is also the case with the known resistor described above according to DE 43 39 551 CI. However, the invention is not limited to such planar resistor shapes. Rather, it is also possible in principle for the resistive element to be curved or to run on a cylindrical surface, to name just a few examples.

[0015] Furthermore, it should be mentioned that the resistor according to the invention preferably has a carrier plate, wherein the resistive element is preferably applied to the carrier plate. For example, the resistive element can be applied to the carrier plate by means of an adhesive layer, wherein the adhesive layer can also be electrically insulating in order to electrically insulate the resistive element from the carrier plate. The carrier plate of the resistor according to the invention can therefore optionally consist of an electrically conductive material or an electrically insulating material (e.g., ceramic). In the preferred embodiment of the invention, the carrier plate has two plate-shaped terminal parts made of a conductor material (e.g., copper) to introduce the electric current into and out of the resistor.An insulating element made of an electrically insulating material (e.g., resin) is preferably located between the two plate-shaped connection parts to prevent current flow between them. Such a design is also known, for example, from the aforementioned patent DE 43 39 551 CI.

[0016] In the aforementioned plate-shaped structure, the conductor material in the deflection area of ​​the resistive element can be applied as a relatively thin coating to the resistive element, which otherwise consists of the resistive material. The coating of the conductor material preferably has a thickness of at most 1 mm, 500 µm, 250 µm, 100 µm, or 50 µm, the thickness being measured perpendicular to the resistive plane. However, the coating of the conductor material should be sufficiently thick to adequately reduce the disruptive temperature spikes (hot spots) in the deflection area.

[0017] In another embodiment of the invention, the conductor material extends over at least 10%, 20%, 50%, 80%, or at least 90% of the thickness of the resistive element in the deflection area of ​​the resistive element, the thickness being measured perpendicular to the resistive plane. In this case, the conductor material thus comprises a portion of the thickness of the resistive element. The conductor material can therefore form a cladding on the resistive material of the resistive element.

[0018] However, within the scope of the invention, it is also possible that the conductor material extends over the entire thickness of the resistance element in the deflection area, with the thickness being measured perpendicular to the resistance plane.

[0019] Furthermore, it is also possible that the conductor material in the deflection area extends perpendicular to the resistance plane over the entire thickness of the resistive element and even projects upwards beyond the resistive material.

[0020] The above description outlines the various possible dimensions of the conductor material in the deflection region, perpendicular to the resistive plane and relative to the resistive element. In absolute terms, the thickness of the conductor material in the deflection region preferably ranges from 10 pm to 100 pm, 20 pm to 70 pm, 30 pm to 50 pm, or is 40 pm.

[0021] As mentioned above, the resistive element in the deflection region is preferably substantially U-shaped, thus having a base and two adjacent legs. In the base of the U-shaped deflection region, the conductor material can extend over a portion of the width of the base, preferably at least 20%, 40%, 50%, 60%, or 80% of the width of the base in the plane of resistance, the width of the base being measured perpendicular to its longitudinal extent.

[0022] However, there is also the alternative possibility that the conductor material in the U-shaped deflection area in the base extends over the entire width of the U-shaped deflection area in the resistance plane.

[0023] Furthermore, there is even the possibility that the conductor material in the deflection area extends across the entire width of the base of the U-shaped deflection area and even protrudes into the adjacent legs of the U-shaped deflection area.

[0024] It should be noted that the conductor material in the U-shaped deflection area in the base is preferably located at the outer edge and extends inwards from the outer edge.

[0025] Furthermore, it should be noted that the conductor material in the U-shaped deflection area preferably extends over a portion of the base's length along the current flow direction, preferably over at least 20%, 40%, 60%, or 80% of the total base length along the current flow direction. Alternatively, however, the conductor material in the U-shaped deflection area could extend over the entire length of the base along the current flow direction in the plane of resistance.

[0026] In the preferred embodiment of the invention, the meandering resistor element has numerous U-shaped deflection sections, each with a base and two adjacent legs. The base of the U-shaped deflection section alternately lies in one of two parallel straight outer tracks, the outer tracks being coated or plated with the conductor material on their upper surface in the region of the base of the U-shaped deflection sections. The resistor according to the invention is preferably designed for a specific rated current, whereby, during operation with the rated current, a specific average operating temperature develops in the legs of the U-shaped deflection section away from the base.The design of the resistor according to the invention now results in a relatively small maximum temperature rise occurring in the base of the U-shaped deflection area, which is at most 20K, 40K, 60K, 80K or at most 100K when the resistor is energized with the rated current or with a pulse current equal to twice, three times or four times the rated current.

[0027] Furthermore, it should be mentioned that the resistor according to the invention can also have several meandering resistor elements that are electrically connected in parallel and intertwined. It is advantageous if the plating or coating with the conductor material is triangular at the ends of the base of the U-shaped deflection areas.

[0028] It should be noted that the invention is not limited to a specific conductor material. For example, the conductor material could be one of the following:

[0029] • Copper or a copper alloy,

[0030] • Aluminum or an aluminum alloy,

[0031] • Nickel or a nickel alloy,

[0032] • Tin or a tin alloy,

[0033] • Silver or a silver alloy,

[0034] • Chromium or a chromium alloy.

[0035] Furthermore, it should be generally mentioned that the resistor according to the invention is preferably designed as a film resistor and as an SMD resistor (SMD: Surface Mounted Device).

[0036] Furthermore, it should also be mentioned in general that the resistor according to the invention preferably has a resistance value in the range of lmQ-lkQ.

[0037] Furthermore, it should be mentioned that the invention is not limited to a specific resistance alloy with regard to the resistance material. Preferably, however, the resistance material is one of the following resistance alloys:

[0038] • Copper-manganese-nickel alloy, in particular CuMn12Ni or CuN25-10, • Copper-manganese-tin alloy, in particular CuMn7Sn,

[0039] • Nickel-chromium alloy,

[0040] • Tin alloy,

[0041] • Copper-nickel-tin alloy.

[0042] Furthermore, it should be mentioned that the term "deflection region" used within the scope of the invention preferably provides for a U-shaped reversal of the current direction, i.e., with a change of direction of 180°. However, it is also possible within the scope of the invention that the current direction in the deflection region undergoes only a change of direction that includes an angle of less than 180°.

[0043] Finally, it should be mentioned that the invention also includes a corresponding operating method in which only a relatively small temperature increase occurs in the deflection areas in order to improve the durability of the resistor.

[0044] Other advantageous embodiments of the invention are characterized in the dependent claims or are explained in more detail below together with the description of the preferred embodiments of the invention with reference to the figures.

[0045] Brief description of the drawings

[0046] Figure 1 shows a perspective view of a snubber resistor according to the invention with a meandering shape of the resistance element.

[0047] Figure 2 shows a schematic representation of a U-shaped deflection area of ​​the resistance element in the snubber resistor according to Figure 1.

[0048] Figure 3 shows a modification of the embodiment according to Figures 1 and 2 with two meandering resistance elements.

[0049] Detailed description of the drawings

[0050] The following section describes the embodiment of a snubber resistor 1 according to the invention, as shown in Figures 1 and 2. It should be noted beforehand that the snubber resistor 1 is designed to dampen voltage spikes. For this purpose, the snubber resistor 1 can be mounted on two contact surfaces 2, 3 of a printed circuit board, which also contains conductive traces 4, 5 to introduce an electric current I into and out of the snubber resistor 1.

[0051] The snubber resistor 1 according to the invention initially has two plate-shaped connection parts 6, 7, wherein the electric current I is introduced into the snubber resistor 1 via the connection part 6, while the electric current I is again led out of the snubber resistor 1 via the connection part 7.

[0052] Between the two plate-shaped connection parts 6, 7 there is an insulating element 8 made of an electrically insulating material (e.g. resin) to prevent a current flow between the two plate-shaped connection parts 6, 7.

[0053] A meandering resistance element 9 is applied to the top surface of the plate-shaped connection parts 6, 7 and the insulating element 8, wherein the meandering resistance element 9 is glued to the top surface of the plate-shaped connection parts 6, 7 and the insulating element 8 by means of an electrically insulating adhesive layer.

[0054] At the ends of the meandering resistance element 9 are two contact rails 10, 11, which connect the meandering resistance element 9 to the plate-shaped connection part 6 and to the plate-shaped connection part 7, respectively.

[0055] The meandering resistance element 9 has numerous U-shaped deflection areas 12, which are shown in detail in Figure 2 and each comprise a base 13 and two legs 14, 15.

[0056] The invention provides that the base 13 of the U-shaped deflection areas 12 is each covered with a plating 16 made of a conductor material (e.g. copper) in order to avoid the temperature increases (hotspots) in the U-shaped deflection areas 12 that are disturbing in the prior art.

[0057] The plating 16 made of the conductor material (e.g., copper) extends inwards from an outer edge 17 over a certain width c. The base 13 of the U-shaped deflection area 12 therefore consists partly of the conductor material over width c and partly of the actual resistor material over the remainder of its width e.

[0058] Furthermore, Figure 2 shows that the plating 16 made of the conductor material (e.g., copper) extends only over a portion of the thickness of the base 13 of the U-shaped deflection region 12, specifically over a thickness d, while the remaining thickness a of the base 13 of the U-shaped deflection region 12 consists of the resistive material. Thus, there is a thickness difference b between the thickness of the base 13 in the area of ​​the plating 16 and the thickness of the base 13 adjacent to the plating 16. For example, the plating 16 made of the conductor material (e.g., copper) can have a thickness d = 40 pm.

[0059] Furthermore, it can be seen from Figure 2 that the plating 16 made of the conductor material (e.g. copper) extends over the entire length of the base 13 of the U-shaped deflection area 12.

[0060] Finally, Figure 1 shows two parallel, straight outer tracks 18, 19, with the base 13 of the U-shaped deflection areas 12 alternating between these two outer tracks 18, 19. The plating 16 then also alternates between these two outer tracks 18, 19.

[0061] Figure 3 shows a modification of the embodiment according to Figures 1 and 2, this modification being partly identical to the embodiment described above, so that to avoid repetition, reference is made to the above description, using the same reference numerals for corresponding details.

[0062] A special feature of this embodiment is that two meandering resistance elements 9.1, 9.2 are provided, wherein the two meandering resistance elements 9.1, 9.2 are electrically connected in parallel.

[0063] In the U-shaped deflection areas of the meandering resistive elements 9.1, 9.2, platings 16.1 and 16.2 made of a conductor material (e.g., copper) are also applied. On the outside, the platings 16.1 made of the conductor material (e.g., copper) are triangular in plan view, while the platings 16.2 are essentially rectangular on the inside. The triangular shape of the platings 16.1 is advantageous from a manufacturing perspective. The invention is not limited to the preferred embodiments described above. Rather, a multitude of variants and modifications are possible, which also make use of the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and the features of the dependent claims independently of the respective referenced claims and especially also without the features of the main claim.The invention therefore comprises various aspects of the invention, each of which enjoys independent protection.

[0064] Reference symbol list

[0065] 1 Snubber resistor

[0066] 2. Contact surface on the circuit board for introducing current into the resistor

[0067] 3. Contact surface on the circuit board for conducting the current from the resistor

[0068] 4. Conductor track on the circuit board for introducing the current into the resistor

[0069] 5. Conductor track on the circuit board for conducting the current from the resistor

[0070] 6. Plate-shaped connection part for introducing current into the resistor

[0071] 7. Plate-shaped connection part for diverting the current from the resistor

[0072] 8 Insulation element to prevent current flow between the connection parts

[0073] 9 Meander-shaped resistance element

[0074] 9.1, 9.2 Meandering resistance elements

[0075] 10, 11 Contact rails for electrical contacting the ends of the meandering resistance element

[0076] 12. Deflection area with deflection of the current flow direction

[0077] 13 Base of the U-shaped deflection area

[0078] 14, 15 Legs of the U-shaped deflection area

[0079] 16. Plating with a conductor material

[0080] 16.1 Triangular plating with the conductor material

[0081] 16.2 Rectangular plating with the conductor material

[0082] 17 Outer edge of the base of the U-shaped deflection area

[0083] 18, 19 Outer paths of the resistor with the base of the U-shaped deflection regions a Thickness of the resistor material in the base of the U-shaped deflection region b Thickness difference between leg and base of the U-shaped deflection region c Width of the conductor material in the base of the U-shaped deflection region d Thickness of the conductor material in the base of the U-shaped deflection region e Width of the base of the U-shaped deflection region

[0084] Current through the resistor

Claims

REQUIREMENTS 1. Resistor (1), in particular snubber shunt (1) for damping voltage peaks, comprising a) a resistive element (9; 9.1, 9.2) made of a resistive material, wherein the resistive element (9; 9.1, 9.2) has a meandering shape with at least one deflection region (12) with a deflection of the current flow direction, characterized in that the resistive element (9; 9.1, 9.2) in the deflection region (12) consists at least partially of a conductor material which has a higher specific electrical conductivity than the resistive material, so that the current-carrying cross-section of the resistive element (9; 9.1, 9.2) in the deflection region (12) consists at least partially of the conductor material.

2. Resistor (1) according to claim 1, characterized in that the resistance element (9; 9.1, 9.2) runs in a resistance plane.

3. Resistor (1) according to one of the preceding claims, characterized in that a) the resistor (1) has a carrier plate (6, 7, 8), b) the resistive element (9; 9.1, 9.2) is applied to the carrier plate (6, 7, 8), c) the resistive element (9; 9.1, 9.2) is preferably bonded to the carrier plate (6, 7, 8) by means of an adhesive layer, d) the adhesive layer is preferably electrically insulating and the resistive element (9; 9.1, 9.2) electrically insulated from the carrier plate (6, 7, 8), e) that the carrier plate (6, 7, 8) preferably comprises: e) a plate-shaped first terminal part (6) made of a conductor material, in particular for introducing the current (I) into the resistor (1), e2) a plate-shaped second terminal part (7) made of a conductor material, in particular for introducing the current (I) out of the resistor (1), and e3) an insulating element (8) between the first terminal part (6) and the second terminal part (6) to prevent a short circuit between the first terminal part (6) and the second terminal part (7).

4. Resistor (1) according to claim 2 or 3, characterized in that the conductor material in the deflection region (12) of the resistive element (9; 9.1, 9.2) extends a) as a coating over a maximum of 1 mm, 500 µm, 250 µm, 100 µm or 50 µm of the thickness of the resistive element (9; 9.1, 9.2) perpendicular to the resistive plane, or b) over a minimum of 10%, 20%, 50%, 80% or at least 90% of the thickness of the resistive element (9; 9.1, 9.2) perpendicular to the resistive plane, in particular as a plating (16), or c) over the entire thickness of the resistive element (9; 9.1, 9.2) perpendicular to the resistive plane, in particular as a plating (16), or d) over the entire thickness of the resistive element (9; 9.1, 9.2) extends perpendicular to the resistance plane and projects upwards above the resistance material, in particular as cladding (16).

5. Resistor (1) according to one of claims 2 to 4, characterized in that the conductor material in the deflection area (12) extends perpendicular to the resistance plane over a thickness of 100-1000, 200-7000, 300-50000 or 40 ...

6. Resistor (1) according to one of the preceding claims, characterized in that the resistance element (9; 9.1, 9.2) in the deflection area (12) is essentially U-shaped with a base (13) and two adjacent legs (14, 15).

7. Resistor (1) according to claim 6, characterized in that the conductor material in the U-shaped deflection area (12) in the base (13) extends a) over a part of the width of the base (13) of the U-shaped deflection area (12) in the resistance plane, preferably at least 20%, 40%, 50%, 60%, 80% of the width of the base (13) in the resistance plane, or b) over the entire width of the U-shaped deflection area (12) in the resistance plane, or c) over the entire width of the resistance element (9; 9.1, 9.2) in the resistance plane and projects into the adjacent legs (14, 15) of the U-shaped deflection area (12).

8. Resistor (1) according to claim 5 or 6, characterized in that the conductor material extends inwards from an outer edge of the U-shaped deflection area (12) in the base (13).

9. Resistor (1) according to one of the claims, characterized in that the conductor material extends in the U-shaped deflection area (12) over at least 20%, 40%, 60%, 80% or even over the entire length of the base (13) along the current flow direction in the plane of resistance.

10. Resistor (1) according to one of the preceding claims, characterized in that a) the meandering resistive element (9; 9.1, 9.2) extends in a resistive plane, and b) the meandering resistive element (9; 9.1, 9.2) has several U-shaped deflection regions (12) each with a base (13) and two adjacent legs (14, 15), c) the meandering resistive element (9; 9.1, 9.2) has two parallel straight outer tracks, wherein the base (13) of the U-shaped deflection regions (12) alternately lies in one of the two outer tracks, and d) the outer tracks with the base (13) of the individual U-shaped deflection regions (12) are coated on their upper side with the conductor material.

11. Resistor (1) according to one of the preceding claims, characterized in that a) the resistor (1) is designed for a predetermined nominal current, b) the resistive element (9; 9.1, 9.2) in the legs (14, 15) of the U-shaped deflection region (12) assumes a certain average operating temperature when the resistor (1) is energized with the nominal current, and c) the resistive element (9; 9.1, 9.2) in the base (13) of the U-shaped deflection region (12) exhibits a maximum temperature rise of at most 20K, 40K, 60K, 80K or 100K relative to the operating temperature when the resistor (1) is energized cl) with the nominal current and / or c2) with a pulse current equal to twice, three times or four times the nominal current.

12. Resistor (1) according to one of the preceding claims, characterized in that a) the resistor (1) has several meandering resistance elements (9.1, 9.2), b) the meandering resistance elements (9.1, 9.2) are connected electrically in parallel, and / or c) the meandering resistance elements (9.1, 9.2) are intertwined.

13. Resistor (1) according to claim 12, characterized in that a) the meandering resistance elements (9.1, 9.2) each have several U-shaped deflection areas (12), b) the individual U-shaped deflection areas (12) each have a base (13) and two adjacent legs (14, 15), and c) in the outer U-shaped deflection areas (12) the conductor material is applied to the ends of the base (13) of the U-shaped deflection areas (12) in two dirty areas (16.1).

14. Resistor (1) according to one of the preceding claims, characterized in that a) the conductor material is one of the following materials: a) copper or a copper alloy, a2) aluminum or an aluminum alloy, a3) nickel or a nickel alloy, a4) tin or a tin alloy, a5) silver or a silver alloy, a6) chromium or a chromium alloy, and / or b) that the resistor (1) is a foil resistor, and / or c) that the resistor (1) has a resistance value that is c) greater than 1 mΩ, 2 mΩ, 5 mΩ, 10 mΩ, 20 mΩ or 50 mΩ.Q, and / or c2) is less than 1 kQ, 500 Q, 250 Q, 100 Q, 50 Q, 25 Q, 10 Q or 5 Q, and / or d) that the resistive material is a resistive alloy, in particular a dl) copper-manganese-nickel alloy, in particular CuMn12Ni or CuMnNi 25-10, or d2) a copper-manganese-tin alloy, in particular CuMn7Sn, or d3) a nickel-chromium alloy, or d4) a tin alloy, d5) copper-nickel-tin alloy, and / or e) that the resistor (1) is an SMD resistor (1), and / or f) that the conductor material is applied in plate form to the resistive material.

15. Operating method for a resistor (1) according to one of the preceding claims, wherein the resistor (1) is energized with a predetermined nominal current, such that a certain average operating temperature is reached in the legs (14, 15) of the U-shaped deflection region (12) and a certain average operating temperature is reached in the base (13) of the U-shaped deflection region (12). The maximum temperature increase relative to the average operating temperature in the legs (14, 15) is set, characterized in that the maximum temperature increase relative to the operating temperature is at most 20K, 40K, 60K, 80K or 100K.

16. Operating method according to claim 15, characterized in that the maximum temperature increase relative to the operating temperature is at most 20K, 40K, 60K, 80K or 100K when the resistor (1) is energized with a pulse current equal to two, three or four times the rated current.

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