Resistor and associated production method

Abstract

The invention relates to a resistor (1) with a conductive material layer (3) made of a conductive material, a resistive material layer (2) made of a resistive material and joined to the conductive material layer (3), and with 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 conductive material layer (3), wherein the groove (4) is arranged in the conductive material layer (3) and separates the conductive material layer (3) into two connection parts (5, 6) and projects into the resistive material layer (2). According to the invention, the groove flank angle is set such that the temperature coefficient of the resistance value is as close as possible to zero. The invention also relates to an associated production method.

Description

[0001] DESCRIPTION

[0002] Resistance and associated manufacturing process

[0003] Technical field of the invention

[0004] 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.

[0005] Background of the invention

[0006] Current measurement using the so-called four-wire technique is known from the prior art (e.g., EP 0 605 800 Al). 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.

[0007] 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 of α = 90°.

[0008] One requirement for such low-resistance current-sensing resistors is the lowest possible temperature coefficient of resistance (TCR). In other words, 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.

[0009] Description of the invention

[0010] 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.

[0011] This problem is solved by a resistor according to the invention or an associated manufacturing process according to the independent claims.

[0012] 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.

[0013] 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).

[0014] Furthermore, the resistor according to the invention also has a resistance material layer in accordance with the known current-sensing resistor described at the outset, 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.

[0015] 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.

[0016] 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 of resistance 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.

[0017] 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 in the known current-sensing resistor described above, the slot flank angle is generally always 90° due to the manufacturing process; that is, the slot flank in the known current-sensing resistors is always perpendicular to the plane of the conductor material layer. In the manufacture of the resistor according to the invention, a target value for the resistance value is generally specified. In addition, an actual resistance value is also measured or calculated using a model during manufacturing. The slot flank angle and the slot depth in the resistor are then adjusted to meet two requirements. Firstly, the temperature coefficient of the resistance value should be as small as possible in absolute terms.The temperature coefficient should be less than 100 ppm / K, 50 ppm / K, 25 ppm / K, 10 ppm / K, or even less than 5 ppm / K. Furthermore, the actual resistance value should deviate from the specified target value by no more than 5%, 2%, 1%, or 500%. It should be noted that the slot flank angle influences both the temperature coefficient of the resistance value and the resistance value itself. The same applies to the slot depth, which also affects the temperature coefficient and the resistance value. Therefore, within the scope of the invention, these two parameters (slot flank angle and slot depth) must be coordinated to meet both requirements.

[0018] 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.

[0019] However, the conductor material of the conductor material layer should have a lower specific electrical resistance than the resistive material of the resistive layer.

[0020] Generally speaking, the resistor is preferably low-resistance and therefore has a resistance value of at most 10 mQ, 1 mQ, 500 pQ, 250 pQ or 100 pQ.

[0021] 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.

[0022] Furthermore, it should be noted that the groove flank angle on the two opposite groove flanks is preferably the same. However, within the scope of the invention, it is also possible for the groove flank angle on the two opposite groove flanks to be different.

[0023] 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 mm. 2 , 0.2 Q-mm 2 , 0.1 Q-mm 2 , 0.05 Q-mm 2 or 0.03 mm² 2 .

[0024] 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:

[0025] • Copper-manganese alloy, in particular a copper-manganese-nickel alloy or a copper-manganese-aluminium alloy or a copper-manganese-tin alloy,

[0026] • Nickel-chromium alloy, in particular a nickel-chromium-aluminium-silicon alloy,

[0027] • Copper-nickel alloy,

[0028] • Copper-silver alloy,

[0029] • Nickel-copper alloy,

[0030] • Nickel-iron alloy.

[0031] 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.

[0032] 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.

[0033] 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 omitted. 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.

[0034] Brief description of the drawings

[0035] Figure 1A shows a sectional view of a current measuring resistor according to the invention.

[0036] Figure 1B shows an enlarged view of detail Z from Figure 1A.

[0037] Figure 2 shows a diagram that illustrates, 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.

[0038] Figure 3 shows a variation of Figure 2.

[0039] Figure 4 shows a flowchart to illustrate the manufacturing process according to the invention.

[0040] Detailed description of the drawings

[0041] Figures 1A and 1B, which show a low-resistance current measuring resistor 1 according to the invention, are described below.

[0042] 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®).

[0043] 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).

[0044] The conductor material layer 3 is joined to the resistance material layer 2, for example by a roll cladding process, as is known from the prior art. A groove 4 is located in the conductor material layer 3, which divides 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 instead flow through the resistance material layer 2.

[0045] 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.

[0046] 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.

[0047] Furthermore, the slot 4 has slot flanks 7 which are angled to the plane of the printed circuit board layer 3 at a specific slot flank angle α, 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.

[0048] In the manufacture of the current-sensing resistor 1 according to the invention, the slot depth t and the slot flank angle a are adjusted to meet two requirements. Firstly, the actual resistance value R should correspond as closely as possible to the specified target value RSOLL for the resistance value. Secondly, the temperature coefficient TCR of the resistance value R should be as small as possible in magnitude.

[0049] Figure 2 shows a diagram illustrating the utilization of the slot flank angle a to achieve the smallest possible temperature coefficient TCR of the resistance value R.

[0050] The aim here is to manufacture a resistor with a resistance value RSOLL = 500 pQ. The diagram indicates a slot depth t = 0.45 mm. However, with an initial slot flank angle a = 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 a is therefore reduced, as shown by the bold arrow in the diagram. The reduction of the slot flank angle a is carried out until the temperature coefficient TCR of the resistance value R is approximately zero. For example, the slot flank angle can be reduced from the initial value a = 86° to a final value a = 82°, to give just one example.

[0051] The diagram according to Figure 2 therefore shows an example where the temperature coefficient TCR of the resistance value is initially less than zero and then has to be increased accordingly by decreasing the slot flank angle.

[0052] Figure 3, on the other hand, shows another example of a resistor with a desired resistance value RSOLL = 400 pQ. The diagram shows that for this target resistance value RSOLL, a required slot depth t = 0.35 mm is required.

[0053] 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 a. For example, in this embodiment, the slot flank angle a can be increased from an initial value a = 80° to a final value a = 86°.

[0054] The diagram according to Figure 2 thus shows an example where the temperature coefficient TCR of the resistance value R is initially greater than zero and then must be reduced accordingly by increasing the slot flank angle.

[0055] It should be noted that in practice, the slot depth t and the slot flank angle a are not set sequentially. Instead, a pair of values ​​is defined that includes both the slot flank angle a and the slot depth t, and this combination determines both the desired resistance value RSOLL and the desired temperature coefficient TCR~0 of the resistance value R.

[0056] The following describes the flow diagram shown in Figure 4, which serves to explain the manufacturing process according to the invention.

[0057] In a first step S1, a target value RSOLL is specified for the desired resistance value R of the current-sensing resistor 1. In a further step S2, the customer specifies a particular printed circuit board design with a specific grid spacing of the solder pads.

[0058] 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.

[0059] In the next step S4, a pair of values ​​for the slot depth t and the slot flank angle a is calculated, whereby this pair of values ​​is calculated such that the finished current measuring resistor 1 has a resistance value R~Rson and a temperature coefficient TCR~0.

[0060] 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.

[0061] In a further step S6, a resistance material layer 2 made of a resistance material (e.g. Zeranin®) is then provided.

[0062] 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.

[0063] In the next step S8, the groove 4 is then introduced into the conductor material layer 3 and into the resistance material layer 2, with the previously defined values ​​of groove width b, groove depth t and groove flank angle a. The finished current-sensing resistor 1 then has a resistance value RWRSOLL and a temperature coefficient TCR~0.

[0064] 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. List of reference numerals

[0065] 1 Current measuring resistor 3 Copper conductor material layer

[0066] 2 Resistance material layer

[0067] 4 groove

[0068] 5, 6 connection parts

[0069] 7 Slot flank a Slot flank angle relative to the plane of the conductor material layer b Slot width d Total thickness of the current-sensing resistor

[0070] RSOLL Target value for the resistance value R of the current-sensing resistor t Slot depth TCR Temperature coefficient of the resistance value R of the current-sensing resistor

Claims

REQUIREMENTS 1. Resistor (1), in particular a low-resistance current-sensing resistor, comprising a) a conductor material layer (3) made of a conductor material, in particular copper, b) a resistance material layer (2) made of a resistance material, wherein the resistance material layer (2) is joined with the conductor 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 (a) 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 projects into the resistance material layer (2), characterized in that d) the groove flank angle (a) 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 in that the groove flank angle (a) is less than 90°, 88°, 86°, 84°, 82°, 80°, 77° or 75°.

3. Resistor (1) according to one of the preceding claims, characterized in that a) the resistor (1) has a predetermined setpoint (RSOLL) of the resistance value (R), b) the resistor (1) has a predetermined actual value of the resistance value (R), and c) the slot flank angle (a) and the slot depth (t) are matched such that c) 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) the actual value of the resistance value (R) is equal to the predetermined setpoint (RSOLL) with a deviation of at most 5%, 2%, 1% or 500%.

4. Resistor (1) according to one of the preceding claims, characterized in that a) the conductor material is copper, a copper alloy, aluminum or an aluminum alloy and / or b) the conductor material has a lower specific electrical resistance (1) than the resistor material, and / or c) that the resistor (1) has a resistance value (R) of at most 10 mΩ, 1 mΩ, 500 pΩ, 250 pΩ, 100 pΩ, and / or d) that the resistive material layer (2) has a layer thickness of at most 5 mm, 4 mm, 3 mm or 2 mm, and / or e) that the conductive material layer (3) has a layer thickness of at most 5 mm, 2 mm, 1 mm or 0.5 mm, and / or f) that the conductive material layer (3) is thinner than the resistive material layer (2), and / or g) that the slot flank angle (a) is the same or different on both slot flanks of the slot (4), and / or h) that the conductive material has a specific electrical resistance (1) of less than 0.5 mm² 2 / m, 0.2 -mm 2 / m, 0.1 -mm 2 / m, 0.05 mm 2 / m or 0.03 mm 2 / m, and / or i) that the resistance material is a resistance alloy, in particular 11) a copper-manganese alloy, in particular a copper-manganese-nickel alloy or a copper-manganese-aluminium alloy or a copper-manganese-tin alloy, or 12) a nickel-chromium alloy, in particular a nickel-chromium-aluminium-silicon alloy, or 13) a copper-nickel alloy, or 14) a copper-silver alloy, or 15) a nickel-copper alloy, or 16) 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) providing a conductor material layer (3) made of a conductor material, in particular of copper, b) providing a resistance material layer (2) made of a resistance material, c) joining the resistance material layer (2) with the conductor material layer (3), in particular by roll cladding, and d) producing a groove (4) with a specific groove width (b), a specific groove depth (t) and a specific groove flank angle (a) 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 connection parts (5, 6) and extends into the resistance material layer (2), characterized in that the groove depth (t) and the groove flank angle (a) are determined depending on the desired resistance value (RSOLL) 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 method according to claim 5, characterized by the following steps: a) specifying a target value (RSOLL) for the resistance value (R) of the resistor (1), b) adjusting the groove flank angle (a) and the groove depth (t) such that b1) 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 (RSOLL) with a deviation of at most 5%, 2%, 1% or 500%.

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