RESISTANCE ALLOY FOR USE IN SHUNT RESISTOR, USE OF RESISTANCE ALLOY IN SHUNT RESISTOR, AND SHUNT RESISTOR USING RESISTANCE ALLOY
20230326631 · 2023-10-12
Inventors
Cpc classification
H01C7/00
ELECTRICITY
C22F1/00
CHEMISTRY; METALLURGY
International classification
Abstract
Provided is a current detection resistor, such as a shunt resistor, wherein a. low specific resistance and a small thermal electromotive force with respect to copper are achieved, while maintaining a low TCR. A resistance alloy for use in a current detection shunt resistor includes 4.5 to 5.5 mass % of manganese, 0.05 to 0.30 mass % of silicon, 0.10 to 0.30 mass % of iron, and a balance being copper, and has a specific resistance of 15 to 25 μΩ.Math.m.
Claims
1. A resistance alloy for use in a current detection shunt resistor, the resistance alloy comprising 4.5 to 5.5 mass % of manganese, 0.05 to 0.30 mass % of silicon, 0.10 to 0.30 mass % of iron, and a balance being copper, and having a specific resistance of 15 to 25 μΩ.Math.cm.
2. The resistance alloy according to claim 1, having a TCR less than or equal to 100×10.sup.−6/K.
3. The resistance alloy according to claim 1, having a thermal electromotive force with respect to copper within ±1 μV/K.
4. Use of the resistance alloy according to claim 1 in a resistive body of a shunt resistor for use in a current detection device.
5. A current detection shunt resistor comprising a resistive body and an electrode, wherein the resistive body is formed of a resistance alloy comprising 4.5 to 5.5 mass % of manganese, 0.05 to 0.30 mass % of silicon, 0.10 to 0.30 mass % of iron, and a balance being copper, and having a specific resistance of 15 to 25 μΩ.Math.cm.
Description
BRIEF DESCRIPTION OF DRAWINGS
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DESCRIPTION OF EMBODIMENTS
[0049] The inventors, by additionally including an appropriate amount of Fe in a resistance material using a Cu—Mn—Si based alloy such as described in Patent Literature 2, can achieve a low specific resistance (such as 15 to 25 μΩ.Math.cm) while keeping a low TCR (such as less than or equal to 100×10.sup.−6/K).
[0050] Further, the composition and the like may be adjusted to have a small thermal electromotive force with respect to copper.
[0051] In the following, resistance alloys for use in shunt resistors according to the embodiments of the present invention, and a shunt resistor using the same, for example, will be described with reference to the drawings.
[0052] First, the inventors' considerations concerning the present invention will be briefly explained.
[0053] 1) As the focus of the inventors, it is important to mix and use a resistance alloy that shows a negative TCR in the resistive body, to compensate for the contribution of the large positive TCR of copper used in the electrodes. However, there are few reports concerning resistance alloys having a large negative TCR.
[0054] 2) While copper-nickel alloys having low TCR and excellent long-term stability are present, such alloys have a large thermal electromotive force of 40 μV/K with respect to copper. Thus, in a shunt resistor for use in a current detection device with large current flows, the detection accuracy decreases due to the Peltier effect.
[0055] 3) As an example of an alloy having a negative TCR, there is a nickel-chromium based alloy. However, the nickel-chromium based alloy has a specific resistance greater than or equal to two-fold compared to copper-nickel alloys and copper-manganese alloys. Accordingly, it is difficult to achieve a reduced resistance of the shunt resistor.
[0056] In the present embodiment, a resistance alloy for a resistive body that makes it possible to achieve a low specific resistance (such as 15 to 25 μΩ.Math.cm) is provided.
[0057] Further, the results of adjustment of the alloy composition and the like to have a low TCR (less than or equal to 100×10.sup.−6/K) and a sufficiently small thermal electromotive force with respect to copper (less than or equal to 1.0 μV/K) are indicated.
First Embodiment
[0058] An embodiment of the present invention will be described below in concrete terms.
[0059] An alloy of the present embodiment is a resistance alloy having a low TCR, and is a quaternary alloy composed of copper-manganese-silicon-iron. The resistance alloy can be used as the resistance material of a shunt resistor.
[0060]
[0061] Herein, the mass fraction of copper is shown on the axis on the upper-left side, and the mass fraction of silicon+iron is shown on the axis on the upper-right side. Meanwhile, the mass fraction of manganese is shown on the axis on the bottom side.
[0062]
[0063] A representative value of manganese is 5.0 mass %. A representative value of silicon is 0.15 mass %. A representative value of iron is 0.2 mass %. The balance is copper.
[0064]
[0065] As illustrated in
[0066] Next, an example of an evaluation sample manufacturing process will be briefly described: [0067] 1) Raw materials are weighed. [0068] 2) The materials of 1) are dissolved. [0069] 3) Using a cold rolling mill, a hoop material of a predetermined thickness is obtained. [0070] 4) In a vacuum gas replacement furnace, heat treatment is performed in an N.sub.2 atmosphere at 500 to 700° C. for 1 to 2 hours. [0071] 5) From the hoop material, an evaluation element with the shape shown in
[0073] The mass fraction of each of the alloy components in the region R is adjusted with respect to each other such that the resistance alloy has the following characteristics (appropriate conditions).
Appropriate Conditions
[0074] 1) The specific resistance is greater than or equal to 15 μΩ.Math.cm and less than or equal to 25 μΩ.Math.cm.
[0075] 2) The TCR with reference to 25° C. is less than or equal to 100×10.sup.−6/K (from 0 to approximately 100×10.sup.−6/K) at 100° C.
[0076] 3) Thermal electromotive force with respect to copper is within +10 μV/K.
[0077] Thus, in the present invention, in order to solve the problems, a resistance alloy is provided that has a low specific resistance (about 20 μΩ.Math.cm: in a range of 15 to 25 μΩ.Math.cm), a low TCR (less than or equal to 100×10.sup.−6/K), and a small thermal electromotive force with respect to copper (within ±1 μV/K).
[0078] As used herein, the term “small-sized” with reference to a shunt resistor means those with a chip size of less than or equal to 6.3×3.1 mm. Also, the term “low resistance” means that the resistance of the product is 0.5 mΩ or less.
Detailed Description Regarding Resistance Alloy Sample
[0079] Various resistance alloys were prepared as shown below.
[0080] The compositions and characteristics of the resistance alloys are shown in Table 1.
TABLE-US-00001 TABLE 1 Thermal electromotive force with respect to Specific TCR copper Composition (mass %) resistance (100° C./25° C.) (0-100° C.) Cu Mn Fe Si (μΩ .Math. cm) (×10.sup.−6/K) (μV/K) Example 1 Bal. 5 0.2 0.1 20.0 84 0.11 Example 2 Bal. 5 0.2 0.2 20.8 77 0.09 Sample 1 Bal. 4.5 0 0 17.2 132 0.87 Sample 2 Bal. 5 0 0 18.9 99 0.95 Sample 3 Bal. 5.5 0 0 20.7 76 1.04 Sample 4 Bal. 5 0.2 0 19.9 87 −0.32 Sample 5 Bal. 5 0.5 0 20.9 76 −1.06 Sample 6 Bal. 5 1 0 21.2 82 −1.43 Sample 7 Bal. 5 0 1 26.9 43 −0.50 Comparative Cu-14Ni 20 325 −27 example 1 (Cu-Ni alloy) Comparative Cu-7Mn-2.3Sn 29 −2 0.10 example 2 (Cu-Mn-Sn alloy)
[0081] Table 1 shows the compositions ant electrical characteristics (specific resistance, TCR, and thermal electromotive force with respect to copper) of the resistance alloys (Examples 1 and 2) according to the present embodiment and the resistance alloys including Comparative Example 1 (Cu—14Ni) and Comparative Example 2 (Cu—Mn—Sn alloy). Table 1 further includes Sample 1 to Sample 7 for the purpose of verifying and determining a composition range (content range) of the resistance alloy of the present invention.
[0082] With respect to the specific resistance of the resistance material, for the samples of Examples 1, 2, values (15 to 25 μΩ.Math.cm) equivalent to those of Comparative Examples 1, 2, which are commercially available materials, were obtained. The thermal electromotive force with respect to copper (0 to 100° C.) is less than or equal to 0.2 μV/K, and sufficiently satisfies the appropriate condition.
[0083] By considering the data of Table 1, particularly the values of Examples 1, 2 and Samples 1 to 7, the following can be seen.
1) Maintaining a Low Specific Resistance while Adjusting Other Performances
[0084] Compared to the results for Samples 1 to 3 that include neither Fe nor Si, the CuMn alloy makes it possible to achieve the appropriate conditions (characteristics requirements) with respect to the specific resistance and TCR characteristics of the present invention. However, the thermal electromotive force with respect to copper may exceed 1 μV/K. Accordingly, it is necessary to add an element that lowers the thermal electromotive force with respect to copper, without adversely affecting (increasing) the TCR.
2) Regarding Improvements of TCR and the Like, and Influence of Addition of Fe
[0085] If another element, such as Fe herein, is added to the CuMn alloy, the TCR decreases but the specific resistance tends to increase. Accordingly, in order to evaluate the effect of decreasing the TCR, it is necessary to consider both the specific resistance and the TCR.
[0086]
[0087]
[0088] As illustrated in
[0089] Further, in the Cu—5Mn—Fe alloys, it can be evaluated that the TCR increases (deteriorates) as the Fe composition increases. In particular, the TCR sharply increases as the Fe composition exceeds 0.5 mass % and reaches 1.0 mass %.
[0090] Note, however, that the TCR does not sharply increase as long as the Fe composition is less than 0.5 mass %, such as about 0.2 mass %.
[0091] In any of the ranges, the TCR is less than or equal to 100×10.sup.−6/K.
[0092]
[0093] As will be seen from Sample 4 (Fe: 0.2 mass %), even if the amount of Fe added is small, there is the effect of greatly lowering the thermal electromotive force with respect to copper. Further, it can be seen that, from the values of Samples 2 and 4-6, by adding 0.1 to 0.3 mass % of Fe, the thermal electromotive force with respect to copper falls within the range of about ±0.5 μV/K. In addition, as will also be seen from
[0094] Thus, in the Cu—Mn alloys, if the resistance alloy has 0.10 to 0.30 mass % of iron added thereto, the thermal electromotive force with respect to copper can be kept within ±1 μV/K and the TCR less than or equal to 100×10.sup.−6/K.
3) Regarding Influence of Si Addition
[0095] If the composition of the Cu—Mn based alloy material is nearly 100% Cu, it can be expected that oxidation of Cu will become a problem. Accordingly, it is also important to suppress oxidation of Cu.
[0096] Using the evaluation element of
[0097]
[0098]
[0099] It can be seen from the XRD data (
[0100] This phenomenon is presumed to be based on the Cu-oxidation suppressing effect due to an Si oxide being formed on the material surface of the resistance alloy by the addition of Si.
[0101]
[0102] As illustrated in
Detailed Description of the Effectiveness of the Present Invention
[0103] In the following, the effectiveness of the present invention is described in detail.
[0104] The present invention provides a resistance alloy for a current detection shunt resistor, the resistance alloy having 4.5 to 5.5 mass % of Mn, 0.10 to 0.30 mass % of Fe, 0.05 to 0.30 mass % of Si, and the balance being Cu.
[0105] The resistance alloy has a specific resistance in the range of 15 to 25 μΩ.Math.cm.
[0106] Further, the resistance alloy has a TCR less than or equal to 100×10.sup.−6/K (25-100° C.).
[0107] Further, the resistance alloy has a thermal electromotive force with respect to copper within ±1 μV/K.
[0108] With such characteristics, the resistance alloy is suitable for a small-sized and low-resistance shunt resistor, and a low TCR value can also be achieved. The current detection accuracy of a current detection device using the shunt resistor is improved, and the space required for the current detection device can be reduced by a reduction in size of the shunt resistor.
Second Embodiment
[0109] Next, a second embodiment of the present invention will be described.
[0110] The shunt resistor A illustrated in
[0111] The resistive body 11 and the electrodes 15a, 15b may be joined by electron beam (EB) welding, laser beam (LB) welding, and the like. The shunt resistor A illustrated in
[0112] To confirm the effect of using the resistance alloy of the present invention in a shunt resistor product, a shunt resistor was fabricated using the resistive body of each of Example 1 and Comparative Example 2.
TABLE-US-00002 TABLE 2 Size Resistive Overall Overall Resistive body Resistance TCR length width body length thickness value (100° C./25° C.) (mm) (mm) (mm) (mm) (mΩ) (ppm/K) Resistor using 6.3 3.15 2 1 0.2 310 Comparative example 2 Resistor using 6.3 3.15 3 1 0.2 240 material of Example 1
[0113] Table 2 compares Comparative Example 2 and Example 1, and shows size, resistance value, and TCR.
[0114] The outer size of the shunt resistor was 6.3 mm×3.1 mm, the thickness of the resistive body was 1 mm, and the rated resistance value of the shunt resistor was 0.2 mΩ.
[0115] As shown in Table 2, in the shunt resistor using the resistance alloy of Example 1, compared to when the resistance alloy of Comparative Example 2 is used, the specific resistance can be reduced, although the rated resistance value is the same. Accordingly, the length of the resistive body can be increased from 2 mm to 3 mm. Thus, the TCR can be reduced as described with reference to
[0116] In the shunt resistor according to the present embodiment, freedom of design of the shunt resistor can be ensured by using a resistive body having a relatively high specific resistance.
[0117] Further, by using the resistance alloy having a relatively high specific resistance, the contribution of the TCR of Cu used in the electrodes relative to the entire resistor can be reduced. Accordingly, a shunt resistor taking advantage of the characteristics of the resistance alloy can be provided.
[0118] Herein, in the present embodiment, the TCR of the resistance material is adjusted to be on the negative side. Thus, the TCR of the resistor to which the copper electrodes have been joined can be reduced.
[0119] For the shunt resistor A structured and dimensioned as illustrated in
Third Embodiment
[0120] Next, a third embodiment of the present invention will be described. This is an example of manufacture in which an elongated joined material comprising a resistive body and electrodes joined together is prepared and then punched and cut. In this way, it is possible to mass-produce relatively small-sized shunt resistors.
[0121] In the following, an example of such manufacturing process is described.
[0122] As illustrated in
[0123] As illustrated in
[0124] As illustrated in
[0125] The resistance value may be adjusted by the difference in thickness of the resistance material 21 and the electrode material 25a, 25b. Further, a step (Δh.sub.2) may be formed, as will be described below with reference to
[0126] Next, as illustrated in
[0127] Then, as illustrated in
[0128] Note that, as illustrated in
[0129] The shunt resistor according to the present embodiment has a specific resistance in the range of 15 to 25 μΩ.Math.cm.
[0130] Further, the resistance alloy has a TCR less than or equal to 100×10.sup.−6/K (25-100° C.).
[0131] Further, the resistance alloy has a thermal electromotive force with respect to copper within ±1 μV/K. Further, the thermal electromotive force with respect to copper may be within ±0.5 μV/K, or even within ±0.2 μV/K.
[0132] With the above characteristics, the resistance alloy is suitable for small-sized and low-resistance shunt resistors, and a low TCR value can also be achieved. The current detection accuracy of a current detection device using the shunt resistor is improved, and the space required by the current detection device can be reduced by reduction in size of the shunt resistor.
[0133] In the foregoing embodiments, the illustrated configurations and the like are not limiting and may be modified, as appropriate, within a range in which the effects of the present invention can be obtained. Other modifications may also be made and implemented without departing from the scope of the purpose of the present invention.
[0134] The constituent elements of the present invention may be optionally selectively added or omitted, and an invention having an optionally selectively added or omitted configuration is also included in the present invention.
INDUSTRIAL APPLICATION
[0135] The present invention may be utilized as an alloy for a resistor.
[0136] All publications, patents and patent applications cited in the present description are incorporated herein by reference in their entirety.