Resistance and associated manufacturing process

Abstract

The invention relates to a resistor (1) comprising a conductor material layer (3) made of a conductor material, a resistive material layer (2) made of a resistive material joined to the conductor material layer (3), and a groove (4) having a specific groove width (b), a specific groove depth (t), and a specific groove flank angle relative to the plane of the conductor material layer (3), wherein the groove (4) is arranged in the conductor material layer (3) and divides the conductor material layer (3) into two terminal parts (5, 6) and projects into the resistive material layer (2). The invention provides that the groove flank angle is set such that the temperature coefficient of the resistance value is as close to zero as possible. Furthermore, the invention includes an associated manufacturing process.

Description

Technical field of the invention

[0001] The invention relates to a resistor, in particular a low-resistance current-sensing resistor for measuring an electric current. The invention further relates to a manufacturing method for producing such a resistor according to the invention. Background of the invention

[0002] Current measurement using the so-called four-wire technique is known from the prior art (e.g., EP 0 605 800 A1). In this technique, the electric current to be measured is passed through a low-resistance current-sensing resistor, the voltage across the resistor is measured, and this voltage is then used, according to Ohm's law, to determine the electric current flowing through the resistor.

[0003] To manufacture such low-resistance current-sensing resistors, it is also known to bond a conductor layer made of a conductive material (e.g., copper) with a resistive layer made of a resistive material (e.g., Zeranin®), which can be done, for example, using a roll cladding process. Subsequently, a groove is machined into the conductor layer, extending into the resistive layer and separating two terminals within the conductor layer. These terminals serve to introduce the electric current to be measured into the current-sensing resistor and to discharge it from the current-sensing resistor. The groove separating the two terminals can be machined, for example, by milling and typically has groove flanks that are perpendicular to the circuit board layer, i.e., with a groove flank angle α = 90°.

[0004] One requirement for such low-resistance current-sensing resistors is the lowest possible temperature coefficient of resistance (TCR). This means the resistance of the current-sensing resistor should be as temperature-independent as possible to avoid temperature-dependent measurement errors in current measurement. A problem with the design of a low-resistance current-sensing resistor described above is that the electric current to be measured flows not only through the actual resistive element made of the resistive material, but also through the terminals made of the conductor material (e.g., copper), whose temperature coefficient is relatively high compared to that of the resistive material. Therefore, a disadvantage of known low-resistance current-sensing resistors with a slot to separate the two terminals is the disruptive temperature dependence of the resistance value. Description of the invention

[0005] The invention is therefore based on the objective of creating a resistor (e.g., a current-sensing resistor) whose resistance value has the lowest possible temperature dependence. Furthermore, the invention is based on the objective of creating a manufacturing process for such a resistor according to the invention.

[0006] This problem is solved by a resistor according to the invention or an associated manufacturing process according to the independent claims.

[0007] The resistor according to the invention is preferably used for current measurement, so that the resistor according to the invention is preferably a low-resistance current-measuring resistor ("shunt"). However, the principle according to the invention can also be implemented with other types of resistors.

[0008] In accordance with the known current-measuring resistor described above, the resistor according to the invention also has a conductor material layer consisting of a conductor material (e.g. copper).

[0009] Furthermore, the resistor according to the invention also has a resistance material layer in accordance with the known current-sensing resistor described above, which consists of a resistance material, wherein the resistance material layer is joined to the conductor material layer, for example by a roller plating process.

[0010] In the resistor according to the invention, in accordance with the known current-sensing resistor described above, a groove is located in the conductor material layer of the resistor. This groove extends into the resistance material layer and divides the conductor material layer into two terminal sections. These two terminal sections serve to introduce the electric current to be measured into the resistor and to guide the electric current to be measured out of the resistor, respectively. The groove ensures that the current cannot flow in the conductor material layer between the two terminal sections, but must instead flow through the resistance material layer.

[0011] The invention is based on the technical and physical insight that the temperature coefficient of resistance also depends on the slot flank angle of the slot in the resistor. The temperature coefficient is generally at its maximum when the slot flank angle is 90°, i.e., when the slot flank is oriented perpendicular to the conductor material layer, as in the prior art. It should be noted that, in this description, the slot flank angle is measured between the slot flank and the plane of the conductor material layer. A decrease in the slot flank angle (i.e., a greater inclination of the slot flank) generally leads to an increase in the temperature coefficient of resistance. Conversely, an increase in the slot flank angle (i.e., a lesser inclination of the slot flank) generally leads to a decrease in the temperature coefficient of resistance.This relationship is exploited within the scope of the invention to achieve a temperature coefficient of the resistance value that is as small as possible in absolute terms. For example, if the temperature coefficient of the resistance value is greater than zero, the slot flank angle should be increased to lower the temperature coefficient. Conversely, if the temperature coefficient of the resistance value is less than zero, the slot flank angle should be decreased to increase the temperature coefficient of the resistance value. According to the invention, the slot flank angle can then be adjusted such that the temperature coefficient of the resistance value is less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K, or even less than 5 ppm / K.

[0012] In the resistor according to the invention, the slot flank angle can therefore be smaller than 90°, 88°, 86°, 84°, 82°, 80°, 77° or 75°, whereas the slot flank angle in the known current-sensing resistor described above is usually always 90° due to the manufacturing process, i.e., the slot flank in the known current-sensing resistors is always oriented perpendicular to the plane of the conductor material layer.

[0013] In the manufacture of the resistor according to the invention, a target value for the resistor's resistance is generally specified. In addition, an actual resistance value is measured or calculated using a model during the manufacturing process. The slot flank angle and the slot depth in the resistor are then adjusted to meet two requirements. First, the temperature coefficient of the resistor should be as small as possible in absolute terms; that is, it should be less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K, or even less than 5 ppm / K. Second, the actual resistance value should be equal to the specified target value with a deviation of no more than 5%, 2%, 1%, or 500%. It should be noted that the slot flank angle influences both the temperature coefficient of the resistor and the resistance value itself.The same applies to the groove depth, which influences both the temperature coefficient of the resistance value and the resistance value itself. Therefore, within the scope of the invention, the two parameters (groove flank angle and groove depth) must be coordinated to meet both requirements.

[0014] It has already been mentioned above that the conductor material layer of the resistor according to the invention consists of a conductor material, which can be, for example, copper. However, the invention is not limited to copper with regard to the conductor material of the conductor material layer, but can alternatively also be implemented with a copper alloy, aluminum or an aluminum alloy.

[0015] However, the conductor material of the conductor material layer should have a lower specific electrical resistance than the resistive material of the resistive layer.

[0016] It should be noted that the resistor is preferably low-resistance and therefore has a resistance value of at most 10 mΩ, 1 m2, 500 µΩ, 250 µΩ or 100 µΩ.

[0017] Furthermore, it should be noted that the resistive material layer preferably has a thickness of at most 5 mm, 4 mm, 3 mm, or 2 mm, while the conductive material layer preferably has a thickness of at most 5 mm, 2 mm, 1 mm, or 0.5 mm. In practice, however, the conductive material layer should be thinner than the resistive material layer.

[0018] Furthermore, it should be noted that the groove flank angle is preferably the same on both opposite groove flanks. However, within the scope of the invention, it is also possible for the groove flank angle to be different on the two opposite groove flanks.

[0019] As mentioned above, the conductor material of the conductor material layer preferably has a specific electrical resistance that is lower than the specific electrical resistance of the resistive material. For example, the specific electrical resistance of the conductor material can be less than 0.5 Ω·mm. 2 , 0.2 Ω·mm 2 , 0.1 Ω·mm 2 , 0.05 Ω·mm 2 or 0.03 Ω·mm 2 .

[0020] With regard to the resistive material of the resistive layer, the invention is not limited to a specific resistive material. Preferably, however, the resistive material is a resistive alloy. For example, the following resistive alloys are possible within the scope of the invention: • Copper-manganese alloy, in particular a copper-manganese-nickel alloy or a copper-manganese-aluminium alloy or a copper-manganese-tin alloy, • Nickel-chromium alloy, in particular a nickel-chromium-aluminium-silicon alloy, • Copper-nickel alloy, • Copper-silver alloy, • Nickel-copper alloy, • Nickel-iron alloy.

[0021] Furthermore, it should also be mentioned in general that the resistor according to the invention is preferably an SMD resistor (SMD: Surface mounted device) which is suitable for surface mounting on a printed circuit board.

[0022] Finally, it should be generally mentioned that the term temperature coefficient of the resistance value used in the context of the invention preferably refers to a temperature range of +20°C to +60°C.

[0023] In addition to the resistor described above as a finished component, the invention also includes a manufacturing process for such a resistor, the individual process steps of the manufacturing process according to the invention are already readily apparent from the present description, so that a separate description of the manufacturing process according to the invention can be dispensed with.

[0024] 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 embodiment of the invention with reference to the figures. Brief description of the drawings Fig. Figure 1A shows a sectional view of a current measuring resistor according to the invention. Fig. 1B shows an enlarged view of detail Z from Fig. 1A. Fig. Figure 2 shows a diagram that shows, on the one hand, the dependence of the resistance value on the slot depth and, on the other hand, the dependence of the temperature coefficient of the resistance value on the slot depth. Fig. Figure 3 shows a variation of Fig. 2. Fig. Figure 4 shows a flowchart to illustrate the manufacturing process according to the invention. Detailed description of the drawings

[0025] The following will now describe the Fig. 1A and Fig. 1B described, which show a low-resistance current measuring resistor 1 according to the invention.

[0026] The low-resistance current measuring resistor 1 has a resistance material layer 2 made of a resistance material, which can be, for example, a copper-manganese-tin alloy (e.g. Zeranin®).

[0027] Furthermore, the current measuring resistor 1 according to the invention has a conductor material layer 3 which consists of a conductor material (e.g. copper).

[0028] The conductor material layer 3 is joined to the resistance material layer 2, for example by a roller cladding process, as is known from the prior art.

[0029] In the conductor material layer 3, there is a groove 4 that separates the conductor material layer 3 into two terminal parts 5, 6, with the groove 4 extending into the resistance material layer 2. The groove 4 ensures that an electric current to be measured cannot flow directly in the conductor material layer 3 between the two terminal parts 5, 6, but must flow through the resistance material layer 2.

[0030] Slot 4 has a fixed width b that cannot be changed. A specific PCB design with a particular solder pad grid requires a corresponding slot width b for slot 4. Therefore, slot width b is not suitable as a parameter for adjusting the resistance value R or the temperature coefficient TCR of the current resistor 1.

[0031] Furthermore, the groove 4 has a groove depth t which influences both the resistance value R and the temperature coefficient TCR of the resistance value R.

[0032] Furthermore, the groove 4 has groove flanks 7 which are angled at a specific groove flank angle α to the plane of the printed circuit board layer 3, as shown from Fig. As can be seen in Figure 1B. The slot flank angle α also influences both the resistance value R and the temperature coefficient TCR of the resistance value R of the current-sensing resistor 1.

[0033] In the manufacture of the current-sensing resistor 1 according to the invention, the slot depth t and the slot flank angle α are adjusted to meet two requirements. Firstly, the actual resistance value R should correspond as closely as possible to the specified target value R. SOLL for the resistance value. Secondly, the temperature coefficient TCR of the resistance value R should be as small as possible in absolute value.

[0034] Fig. Figure 2 shows a diagram illustrating the utilization of the slot flank angle α to achieve the smallest possible temperature coefficient TCR of the resistance value R.

[0035] Here, a resistor with a resistance value R is to be used. SOLL=500 µΩ. The diagram then shows a slot depth of t = 0.45 mm. However, with an initial slot flank angle of α = 86°, the resulting temperature coefficient TCR is approximately -11 ppm / K, meaning the temperature coefficient TCR is less than zero. To increase the temperature coefficient TCR, the slot flank angle α is therefore reduced, as indicated by the bold arrow in the diagram. The slot flank angle α is reduced until the temperature coefficient TCR of the resistance value R is approximately zero. For example, the slot flank angle can be reduced from an initial value of α = 86° to a final value of α = 82°, to give just one example.

[0036] The diagram according to Fig. Figure 2 shows an example where the temperature coefficient TCR of the resistance value is initially less than zero and then needs to be increased accordingly by reducing the slot flank angle.

[0037] Fig. Figure 3, however, shows another example of a resistor with a desired resistance value R. SOLL = 400 µΩ. The diagram shows that this target value R SOLL The resistance value R requires a groove depth t=0.35mm.

[0038] At this slot depth t, the temperature coefficient TCR of the resistance value R is greater than zero (TCR ≈ +14 ppm / K), meaning the temperature coefficient TCR must be reduced. This is achieved by increasing the slot flank angle α. For example, in this embodiment, the slot flank angle α can be increased from an initial value of α = 80° to a final value of α = 86°.

[0039] The diagram according to Fig. Figure 2 shows an example where the temperature coefficient TCR of the resistance value R is initially greater than zero and must then be reduced accordingly by increasing the slot flank angle.

[0040] It should be noted that in practice, the groove depth t and the groove flank angle α are not set sequentially. Instead, a pair of values ​​is defined that includes both the groove flank angle α and the groove depth t, and is used to set the desired resistance value R. SOLL as well as leading to the setting of the desired temperature coefficient TCR≈0 of the resistance value R.

[0041] The following will now describe the in Fig. The flow diagram shown in Figure 4 is described and serves to explain the manufacturing process according to the invention.

[0042] In a first step S1, a target value R is determined. SOLL The desired resistance value R of the current measuring resistor 1 is specified.

[0043] In a further step S2, the customer specifies a particular printed circuit board design with a specific grid dimension for the solder pads.

[0044] In the next step S3, the required groove width b for groove 4 in the current-sensing resistor 1 is then specified according to the grid spacing of the solder pads. The groove width b therefore cannot be varied within the scope of the manufacturing process according to the invention, but is predetermined by the design.

[0045] In the next step S4, a pair of values ​​for the slot depth t and the slot flank angle α is calculated, whereby this pair of values ​​is calculated such that the finished current measuring resistor 1 has a resistance value R≈R SOLL and has a temperature coefficient TCR≈0.

[0046] In the next step S5, a conductor material layer 3 made of a conductor material (e.g. copper) is then provided in the conventional manner.

[0047] In a further step S6, a resistance material layer 2 made of a resistance material (e.g. Zeranin®) is then provided.

[0048] A next step S7 then provides that the resistance material layer 2 is joined with the conductor material layer 3, for example by a roller cladding process, as is known from the prior art.

[0049] In the next step S8, the groove 4 is then formed in the conductor material layer 3 and in the resistance material layer 2, with the previously defined values ​​of groove width b, groove depth t, and groove flank angle α. The finished current-sensing resistor 1 then has a resistance value R ≈ R OLL and a temperature coefficient TCR≈0.

[0050] The invention is not limited to the preferred embodiments described above. Rather, the invention also includes variants and modifications that likewise 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, in particular, also without the features of the main claim. The invention thus comprises various aspects of the invention that enjoy independent protection. Reference symbol list 1 current measuring resistor 3. Copper conductor material layer 2 Resistance material layer 4 groove 5, 6 connection parts 7 groove flank α Slot flank angle relative to the plane of the conductor material layer b Groove width d Total thickness of the current-sensing resistor R SOLLTarget value for the resistance value R of the current measuring resistor t groove depth TCR Temperature coefficient of the resistance value R of the current-sensing resistor QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 0 605 800 A1

[0002]

Claims

[1] Resistor (1), in particular a low-resistance current-sensing resistor, with a) a conductor material layer (3) made of a conductor material, in particular copper, b) a resistive material layer (2) made of a resistive material, wherein the resistive material layer (2) is joined with the conductive material layer (3), and c) a groove (4) with a specific groove width (b), a specific groove depth (t) and a specific groove flank angle (α) relative to the plane of the conductor material layer (3), wherein the groove (4) is arranged in the conductor material layer (3) and separates the conductor material layer (3) into two terminal parts (5, 6) and extends into the resistive material layer (2), characterized by , d) that the slot flank angle (α) is set such that the temperature coefficient (TCR) of the resistance value (R) is less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K or 5 ppm / K. [2] Resistor (1) according to claim 1, characterized by , that the groove flank angle (α) is smaller than 90°, 88°, 86°, 84°, 82°, 80°, 77° or 75°. [3] Resistor (1) according to any of the preceding claims, characterized by , a) that the resistance (1) has a predetermined setpoint (R SOLL ) of the resistance value (R) has, b) that the resistor (1) has a predetermined actual value of the resistance value (R), and c) that the groove flank angle (α) and the groove depth (t) are matched, c1) that the temperature coefficient (TCR) of the resistance value (R) is less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K or 5 ppm / K, and c2) that the actual value of the resistance value (R) is equal to the specified target value (R) with a deviation of at most 5%, 2%, 1% or 500% SOLL ) is. [4] Resistor (1) according to any of the preceding claims, characterized by , a) that the conductor material is copper, a copper alloy, aluminum or an aluminum alloy and / or b) that the conductor material has a lower specific electrical resistance (1) than the resistive material, and / or c) that the resistor (1) has a resistance value (R) of at most 10 mΩ, 1 mΩ, 500 µΩ, 250 µΩ, 100 µΩ, and / or d) that the resistance material layer (2) has a layer thickness of not more than 5 mm, 4 mm, 3 mm or 2 mm, and / or e) that the conductor material layer (3) has a layer thickness of not more than 5 mm, 2 mm, 1 mm or 0.5 mm, and / or f) that the conductor material layer (3) is thinner than the resistive material layer (2), and / or g) that the groove flank angle (α) is the same or different on both groove flanks of the groove (4), and / or h) that the conductor material has a specific electrical resistance (1) that is less than 0.5 Ω·mm 2 / m, 0.2 Ω·mm 2 / m, 0.1 Ω·mm 2 / m, 0.05 Ω·mm 2 / m or 0.03 Ω·mm 2 / m, and / or i) that the resistance material is a resistance alloy, in particular i1) a copper-manganese alloy, in particular a copper-manganese-nickel alloy or a copper-manganese-aluminium alloy or a copper-manganese-tin alloy, or i2) a nickel-chromium alloy, in particular a nickel-chromium-aluminium-silicon alloy, or i3) a copper-nickel alloy, or i4) a copper-silver alloy, or i5) a nickel-copper alloy, or i6) a nickel-iron alloy, and / or j) that the resistor (1) is an SMD resistor (1). [5] Manufacturing method for a resistor (1), in particular for a resistor (1) according to one of the preceding claims, comprising the following steps: a) Provision of a conductor material layer (3) made of a conductor material, in particular copper, b) Provision of a resistive material layer (2) made of a resistive material, c) Joining the resistive material layer (2) with the conductive material layer (3), in particular by roller cladding, and d) Providing a groove (4) with a specific groove width (b), a specific groove depth (t) and a specific groove flank angle (α) relative to the plane of the conductor material layer (3) into the conductor material layer (3), wherein the groove (4) separates the conductor material layer (3) into two terminal parts (5, 6) and extends into the resistive material layer (2), characterized by , e) that the groove depth (t) and the groove flank angle (α) depend on the desired resistance value (R) SOLL ) are set such that the temperature coefficient (TCR) of the resistance value (R) is less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K or 5 ppm / K. [6] Manufacturing process according to claim 5, characterized by the following steps: a) Specification of a target value (R SOLL ) for the resistance value (R) of the resistor (1), b) Adjusting the groove flank angle (α) and the groove depth (t) so b1) that the temperature coefficient (TCR) of the resistance value (R) is less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K or 5 ppm / K and b2) that the actual value of the resistance value (R) is equal to the specified target value (R) with a deviation of at most 5%, 2%, 1% or 500% SOLL ) is.

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