Copper alloy material, resistive body, and resistor

Abstract

According to the present invention, a copper alloy material for resistance is at least 10.0 mass% but no more than 14.0 mass% Mn, at least 1.0 mass% but no more than 4.0 mass% Ni, and at least 0.3 mass% but less than 1.0 mass% Al, the remainder being Cu and unavoidable impurities.

Description

Copper alloy material, resistor, and resistor

[0001] The present disclosure relates to a copper alloy material, a resistor, and a resistor.

[0002] In the automotive field, with the recent trend of electrification, various types of electronic devices are being installed and their numbers are increasing. As a result, the number of mounting points for current control components in inverters, batteries, etc. is increasing, and the amount of resistors used in current sensors for this purpose is also increasing. The copper alloy material used for the resistor in a resistor is required to have stability in resistance temperature behavior, that is, a low temperature coefficient of resistance (TCR). To meet this characteristic, Cu-Mn-based alloys are widely used.

[0003] For example, Patent Document 1 shows a copper alloy strip that has a stable resistance even when the environmental temperature changes and has good solder mountability. In Patent Document 1, a copper alloy strip having a composition containing 3% by mass or more and 20% by mass or less of manganese, with the balance being copper and unavoidable impurities, is shown. By Auger electron spectroscopy, the ratio of the Mn content to the Cu content (surface [Mn / Cu] ratio) measured in the surface layer region defined by the surface and the position 0.05 μm in the depth direction from the surface is less than 0.030 in terms of mass ratio. This copper alloy strip has less Mn on its surface and has high adhesion to solder. On the other hand, since Mn is present abundantly at a total of 3% by mass or more inside, it has been shown to have a low temperature coefficient of resistance (TCR).

[0004] Incidentally, in Cu-Mn alloys, when the alloy is held at a high temperature for a long time, Mn segregates and oxidizes on the material surface, forming a Mn oxide film and a layer with a reduced Mn concentration on the material surface. This phenomenon increases the temperature coefficient of resistance (TCR) at the material surface, thus increasing the overall temperature coefficient of resistance (TCR) of the material. As a result, it is known that the temperature coefficient of resistance (TCR) of the material fluctuates before and after being held at a high temperature for a long time. To suppress this property fluctuation, a method of adding Al as a sacrificial oxide element may be employed. For example, Patent Document 2 shows a Cu alloy material that may contain Al in addition to 7.0% by mass to 20.0% by mass of Mn. Patent Document 2 shows that since Al forms oxides more readily than Mn, the oxidation resistance can be improved by preferentially forming Al oxides on the surface rather than Mn, which is more likely to segregate on the surface. Furthermore, Patent Document 2 indicates that the amount of Al is preferably 1.0% by mass or more and 3.0% by mass or less, that when the amount of Al is less than 1.0% by mass, the effect of Al is small, and when the amount of Al exceeds 3.0% by mass, the TCR of the Cu alloy material becomes undesirably large.

[0005] Furthermore, Patent Document 3 indicates that copper-manganese alloy materials are prone to oxidation due to segregation of manganese on the surface of the alloy material, and that when this alloy material is used as a resistor, oxidation of the resistor surface and the resulting change in resistance value become problematic. Patent Document 3 also states that conventional measures to solve this problem (such as limiting the operating temperature range to an upper limit of 140°C, or forming a protective film on the surface of the resistor) are insufficient to prevent oxidation of the resistor surface over long periods of use. Patent Document 3 then proposes a resistor alloy material that maintains or improves the electrical properties of copper-manganese alloys and improves oxidation resistance, characterized by having 6 wt% to 12 wt% manganese, 1 wt% to 3 wt% aluminum, 2 wt% to 3 wt% tin, and the remainder being copper.

[0006] Patent No. 6800387 Patent No. 6471494 Patent No. 4974544

[0007] Incidentally, when using copper alloy materials to manufacture components such as resistors and then soldering them onto a circuit board, the copper alloy material needs to have good solder wettability. Furthermore, when pouring the molten copper alloy ("molten alloy") into a mold, for example, high fluidity of the molten alloy (hereinafter simply referred to as "molten alloy flowability") is required. However, until now, a copper alloy material that possesses both a reduced temperature coefficient of resistance (TCR) and these desirable properties has not been realized.

[0008] This disclosure has been made in view of the above circumstances, and one of its objectives is to realize a copper alloy material that has a small temperature coefficient of resistance (TCR), which indicates the fluctuation of resistance due to changes in ambient temperature, and has good solder wettability and molten alloy flowability. Another objective is to realize a resistor containing the copper alloy material and a resistor device containing the resistor. In this specification, "resistance" means electrical resistance.

[0009] One aspect of the present invention is a copper alloy material for resistance, comprising Mn: 10.0% by mass or more and 14.0% by mass or less, Ni: 1.0% by mass or more and 4.0% by mass or less, and Al: 0.3% by mass or more and less than 1.0% by mass, with the remainder being Cu and unavoidable impurities.

[0010] Aspect 2 of the present invention is the copper alloy material according to Aspect 1, wherein the maximum wetting stress (Fmax) of the Sn solder measured by meniscography is 2.0 mN or more.

[0011] Aspect 3 of the present invention is a copper alloy material according to aspect 1 or 2, wherein the copper alloy material is melted in a nitrogen atmosphere and the molten alloy is held at 1350°C, and the resulting ingot is poured into a Cu mold that is groove-shaped and elongated with a width of 12 mm to 14 mm and an inclination angle of 5°, and the ratio L / M of length L (mm) to mass M (g) is greater than 1.6.

[0012] Aspect 4 of the present invention is a copper alloy material according to aspect 1 or 2, wherein the Al content is 0.3% by mass or more and 0.9% by mass or less.

[0013] Aspect 5 of the present invention is the copper alloy material according to aspect 3, wherein the Al content is 0.3% by mass or more and 0.9% by mass or less.

[0014] Aspect 6 of the present invention is a copper alloy material according to aspect 1 or 2, wherein the absolute value of the temperature coefficient of resistance (TCR) at 20°C to 50°C is 20 ppm / K or less.

[0015] Embodiment 7 of the present invention is a copper alloy material according to any one of Embodiments 3 to 5, wherein the absolute value of the temperature coefficient of resistance (TCR) at 20°C to 50°C is 20 ppm / K or less.

[0016] Embodiment 8 of the present invention is a resistor comprising the copper alloy material described in Embodiment 1 or 2.

[0017] Embodiment 9 of the present invention is a resistor comprising the copper alloy material described in any one of Embodiments 3 to 7.

[0018] Aspect 10 of the present invention is a resistor comprising the resistor described in Aspect 8.

[0019] Aspect 11 of the present invention is a resistor comprising the resistor described in Aspect 9.

[0020] According to this disclosure, it is possible to provide a copper alloy material having a low temperature coefficient of resistance (TCR) and good solder wettability and flowability of molten alloy, a resistor containing the copper alloy material, and a resistor equipped with the resistor.

[0021] This is a schematic perspective view of the apparatus used to evaluate the flowability of the molten alloy in the example. This is a diagram illustrating the method for evaluating the flowability of the molten alloy in the example. This is a graph showing the relationship between solder wettability and the flowability of the molten alloy in the example.

[0022] Conventional technologies have considered an Al content of 1.0 to 3.0 mass% to be desirable from the viewpoint of temperature coefficient of resistance (TCR) and processability. However, the inventors have confirmed that an Al content of 0.3 mass% or more is sufficient to exhibit oxidation resistance and reduce the temperature coefficient of resistance (TCR). On the other hand, when the Al content is 1.0 mass% or more, the formation of an oxide film on the alloy surface by Al is promoted more than necessary, resulting in a decrease in the flowability and solder wettability of the molten alloy. Poor flowability of the molten alloy makes it easier to entrap oxides during casting, leading to a higher likelihood of casting defects in the ingot and raising concerns about a decrease in ingot quality. Furthermore, if casting defects are likely to occur in the ingot, there is a possibility that hot-rolled cracks may occur in the subsequent hot-working process. In addition, if the solder wettability of the copper alloy material is low, there is a concern that the resistor may detach when mounted on a substrate after being processed using the copper alloy material.

[0023] In this disclosure, by setting the amount of Al in the copper alloy material to an appropriate range of 0.3 mass% to less than 1.0 mass%, the sacrificial oxidation effect due to Al addition acts appropriately, thereby suppressing segregation and oxidation of Mn on the material surface even when held at high temperatures, making it possible to obtain a Cu-Mn-based copper alloy material with good solder wettability and molten alloy flowability.

[0024] First, the chemical composition of the copper alloy material of this disclosure will be described.

[0025] [Mn: 10.0% by mass or more and 14.0% by mass or less] When Cu contains 10.0% by mass or more of Mn, the TCR in the temperature range near room temperature decreases, and the temperature fluctuation of the volume resistivity of the material can be suppressed. Therefore, the amount of Mn should be 10.0% by mass or more. On the other hand, if the amount of Mn exceeds 14.0% by mass, the volume resistivity of the material becomes too high, so the amount of Mn should be 14.0% by mass or less. The amount of Mn is preferably 11.0% by mass or more, and preferably 13.0% by mass or less.

[0026] [Ni: 1.0 mass% or more and 4.0 mass% or less] By including 1.0 mass% or more of Ni in Cu, the absolute value of the material's thermoelectric voltage relative to copper can be reduced, and the voltage generated when a temperature gradient occurs in the resistor is reduced, thereby maintaining the resistor's performance. On the other hand, if the amount of Ni is too high, the material's thermoelectric voltage relative to copper becomes negatively large, and the volume resistivity of the material also becomes too high. From these viewpoints, the amount of Ni should be 1.0 mass% or more and 4.0 mass% or less. The amount of Ni should be 1.0 mass% or more, and preferably 3.0 mass% or less.

[0027] [Al: 0.3% by mass or more and less than 1.0% by mass] When Cu contains 0.3% by mass or more of Al, Al is preferentially oxidized over Mn when the material is held at a high temperature for a long time. This suppresses segregation and oxidation of Mn on the surface, and reduces changes in the properties of the material due to oxidation. On the other hand, if Al is contained at 1.0% by mass or more, as described above, the solder wettability of the copper alloy material and the flowability of the molten alloy decrease. From these viewpoints, the amount of Al should be 0.3% by mass or more and less than 1.0% by mass. The amount of Al is preferably 0.3% by mass or more and 0.9% by mass or less, and more preferably 0.3% by mass or more and 0.7% by mass or less.

[0028] [The remainder is Cu and unavoidable impurities] In one preferred embodiment, the remainder consists of Cu and unavoidable impurities. As unavoidable impurities, the inclusion of trace elements introduced depending on the raw materials, materials, manufacturing equipment, etc., is permissible as long as it does not significantly affect the TCR or volume resistivity. If the total amount of unavoidable impurities exceeds 0.5% by mass, there is a possibility that the volume resistivity will become too high. Therefore, it is preferable that the total amount of unavoidable impurities be 0.5% by mass or less, for example, the total amount of Pb, Fe, Sn, Zn, Cr, Mg, P, S, and Si as unavoidable impurities is 0.5% by mass or less.

[0029] The shape of the copper alloy material of this disclosure is not limited and may be plate-shaped, sheet-shaped, rod-shaped, or wire-shaped. When the copper alloy material of this disclosure is used, for example, in a resistor, the copper alloy material of this disclosure may be plate-shaped, i.e., a copper alloy plate. When the copper alloy material of this disclosure is a copper alloy plate, the plate thickness may be, for example, 3.0 mm to 0.05 mm.

[0030] As described above, the copper alloy material of this disclosure exhibits suppressed fluctuations in the temperature coefficient of resistance (TCR) even when held at high temperatures for extended periods, and also shows good solder wettability and good flowability of the molten alloy. These properties of the copper alloy material of this disclosure are described in detail below.

[0031] (1) Temperature coefficient of resistance (TCR) In this disclosure, a small temperature coefficient of resistance means that the absolute value of the temperature coefficient of resistance (TCR) measured by the method described in the examples below, at 20°C to 50°C, is 20 ppm / K or less. Preferably, the absolute value of the temperature coefficient of resistance (TCR) at 20°C to 50°C is 10 ppm / K or less.

[0032] (2) Solder wettability Good solder wettability means that the maximum wetting stress (Fmax) of the Sn solder measured by the meniscography method is 2.0 mN or more, as described in the examples below. The maximum wetting stress (Fmax) is preferably 2.5 mN or more, and more preferably 3.0 mN or more.

[0033] (3) Flowability of molten alloy A good flowability of molten alloy means that, as described in the examples below, a copper alloy material is melted in a nitrogen atmosphere and the molten alloy, held at 1350°C, is poured into a Cu mold that is groove-shaped and elongated with a width of 12 mm to 14 mm and an inclination angle of 5°, and the ratio of length L (mm) to mass M (g) of the ingot obtained is greater than 1.6. The L / M is preferably 2.0 or more, more preferably 2.5 or more.

[0034] The copper alloy material of this disclosure only needs to satisfy a predetermined chemical composition, and its manufacturing method is not limited. When manufacturing a copper alloy sheet, for example, as the copper alloy material of this disclosure, it can be manufactured by the following method. First, a copper alloy ingot with a predetermined chemical composition is obtained, and the copper alloy ingot is heated to 700°C to 900°C and then hot-rolled to obtain a hot-rolled sheet. Next, the hot-rolled sheet is used to perform cold-rolling to obtain a cold-rolled sheet of the desired thickness. If the rolled material hardens during cold-rolling and becomes difficult to roll, an intermediate annealing step of heating to 800°C to 400°C may be provided to soften the material. After that, the cold-rolled sheet can be subjected to finish annealing (strain-relieving annealing) by heating to, for example, 800°C to 400°C to obtain a copper alloy sheet.

[0035] The copper alloy material of this disclosure is for resistive applications. The resistor of this disclosure comprises, and preferably comprises, the copper alloy material of this disclosure for resistive applications. The copper alloy material of this disclosure may be used for electrical and electronic components, for example, in resistors. Examples of resistors include shunt resistors used in current sensors such as inverters and batteries. The resistor only needs to have the resistive element. The resistor may, for example, have an insulator and electrodes in addition to the resistive element.

[0036] The present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited by the following examples, and can be implemented with appropriate modifications to the extent that it is consistent with the spirit described above and below, and all such modifications are included within the technical scope of the present disclosure.

[0037] 1. Preparation of Copper Alloy Sheets Copper alloy ingots (45 mm thick) with the chemical composition shown in Table 1 (where "residue" in Table 1 refers to Cu and unavoidable impurities; the same applies to Tables 2 and 3) were prepared in a cryptol furnace. The obtained copper alloy ingots were heated at 700°C to 900°C for 30 to 300 minutes, then hot-rolled until the thickness was approximately 20 mm to 15 mm, and then water-cooled to obtain hot-rolled sheets. After that, the hot-rolled sheets were surface-machined to remove surface oxide scale. Next, cold-rolling was performed to obtain cold-rolled sheets with a thickness of approximately 2 mm (for TCR measurement) or approximately 0.4 mm (for solder wettability measurement). If the rolled material hardened during cold-rolling and became difficult to roll, an intermediate annealing process was performed by heating to 800°C to 400°C to soften the material, and then cold-rolling was performed again to produce cold-rolled sheets of the above thicknesses. Subsequently, the cold-rolled sheets were subjected to finish annealing (also known as "strain-relieving annealing") using an electric furnace in an air atmosphere (for TCR measurement) or a salt bath furnace (for solder wettability measurement) to obtain copper alloy sheets with a thickness of approximately 2 mm (for TCR measurement) or approximately 0.4 mm (for solder wettability measurement).

[0038] 2. Evaluation of properties Using the obtained copper alloy plates, the temperature coefficient of resistance (TCR), solder wettability, and molten alloy flowability were evaluated as shown below.

[0039] (Temperature Coefficient of Resistance (TCR)) Samples with dimensions of approximately 180 mm to 250 mm in length, 4 mm in width, and 2 mm in thickness were taken from the obtained copper alloy plates. Then, while controlling the sample temperature in a constant temperature bath (Julabo DDBC26, Julabo FP52SL), the resistance value R of the sample at 20°C was measured using a resistance meter (HIOKI RM3543) with the four-terminal method. ２０℃ (mΩ) and the resistance value R at 50°C ５０℃ (mΩ) was measured. Then TCR = {(R ５０℃ -R ２０℃ ) / R ２０℃} × {1 / (50 (°C) - 20 (°C))} × 10 ６The temperature coefficient of resistance (TCR) between 20°C and 50°C was calculated using the given formula. A low TCR was defined as having an absolute value of 20 ppm / K or less in the temperature range between 20°C and 50°C. The results are shown in Table 1.

[0040] (Solder Wetability) A sample with dimensions of approximately 30 mm in length, 10 mm in width, and 0.4 mm in thickness was taken from the obtained copper alloy plate. Using this sample, a solder wettability test was performed by measuring the maximum wetting stress (Fmax) using the meniscography method. The details of the measurement are as follows. The solder and flux used for the measurement were Sn-3Ag-0.5Cu (units are in mass%) and Solbond R100-40 (inactive rosin flux) manufactured by MacDermid Performance Solutions, respectively. For evaluation, samples that had been electrolytically degreased and then pickled with sulfuric acid were used. For electrolytic degreasing, Pakuna Erector F-155B manufactured by YUKEN Industries was used as the degreasing solution. The solder wettability test was performed using a solder checker manufactured by RHESCA, with measurement conditions of a solder bath temperature of 265°C and a material immersion rate of 25 mm / sec. The immersion depth was set to 12 mm and the immersion time to 5 seconds. In the solder wettability test, a maximum wetting stress (Fmax) of 2.0 mN or higher, measured by the meniscography method, was evaluated as good solder wettability. The results are shown in Table 2.

[0041] (Fluidity of Molten Alloy) The fluidity of the molten alloy was evaluated using a small melting device. First, about 50 g of a copper alloy plate prepared in the same manner as the copper alloy plate for TCR measurement was placed in a carbon crucible and melted in an electric furnace with a nitrogen flow to obtain a molten alloy. Then, after maintaining the temperature of the molten alloy at 1350 °C in the electric furnace, as shown in Fig. 1, the molten alloy was poured from the carbon crucible 1 into a Cu mold (Cu cooling tray) 2 having a groove shape with a width of 12 mm to 14 mm and a long shape and an inclination angle of 5°, and a long alloy ingot 3 with a width of about 12 mm to 14 mm was produced. Then, the length L (mm) and mass M (g) of the alloy ingot 3 were measured, and the ratio L / M of the length to the mass was determined. In the measurement of the length L, as shown in Fig. 2, the length was measured at the 1 / 4 position, 1 / 2 position, and 3 / 4 position of the width W of the alloy ingot 3, and the average value thereof was taken as the length L of the alloy ingot. In this example, when this L / M exceeds 1.6, it was evaluated that the fluidity of the molten alloy is good. Preferably, it is when L / M is 2.0 or more. The results are shown in Table 3.

[0042]

[0043]

[0044]

[0045] The results in Tables 1-3 are discussed. Samples No. 3-6 satisfied the specified chemical composition, and the sacrificial oxidation effect due to Al addition acted appropriately. As a result, even when held at high temperatures for a long time, the fluctuation in resistance was suppressed, the temperature coefficient of resistance (TCR) was small, and good solder wettability was observed. Samples No. 3 and 4 also showed good molten metal flowability. As shown in Figure 3, the evaluation results of solder wettability for No. 1-8 shown in Table 2 and the evaluation results of molten metal flowability for No. 1-4, 7, and 8 shown in Table 3 are indicated by ◆ or ■ (in Figure 3, the unit of Al amount wt.% is synonymous with mass%), and the molten metal flowability of the alloy showed a similar trend to that of solder wettability. This is thought to be because the sacrificial oxidation effect due to Al addition acts appropriately on the molten metal flowability of the alloy, similar to the trend of solder wettability. Furthermore, from the trend in Figure 3, sample No. Regarding the flowability of samples 5 and 6, as indicated by the diamond symbols in Figure 3, a similar trend to that of solder wettability is observed. As a result, it is considered that the flowability of samples No. 5 and 6, like that of samples No. 3 and 4, shows an L / M ratio greater than 1.6.

[0046] In contrast, as shown in Table 1, Nos. 1 and 2, when the Al content was low, the variation in the temperature coefficient of resistance (TCR) became large. Also, as shown in Table 2, Nos. 7 and 8, when the Al content was excessive, good solder wettability was not observed. Furthermore, as shown in Table 3, Nos. 7 and 8, when the Al content was excessive, good molten alloy flowability was also not observed.

[0047] This application is accompanied by a priority claim based on Japanese Patent Application No. 2024-232755 and a priority claim based on Japanese Patent Application No. 2025-114247. Japanese Patent Applications No. 2024-232755 and No. 2025-114247 are incorporated herein by reference.

[0048] 1. Carbon crucible 2. Cu mold (Cu cooling tray) 3. Alloy ingot

Claims

1. A copper alloy material for resistance, comprising Mn: 10.0% by mass or more and 14.0% by mass or less, Ni: 1.0% by mass or more and 4.0% by mass or less, and Al: 0.3% by mass or more and less than 1.0% by mass, with the remainder being Cu and unavoidable impurities.

2. The copper alloy material according to claim 1, wherein the maximum wetting stress (Fmax) of the Sn solder measured by meniscography is 2.0 mN or more.

3. The copper alloy material according to claim 1 or 2, wherein the copper alloy material is melted in a nitrogen atmosphere and the molten alloy is held at 1350°C, and the resulting ingot is poured into a Cu mold that is groove-shaped and elongated with a width of 12 mm to 14 mm and an inclination angle of 5°, and the ratio L / M of length L (mm) to mass M (g) is greater than 1.

6.

4. The copper alloy material according to claim 1 or 2, wherein the Al content is 0.3% by mass or more and 0.9% by mass or less.

5. The copper alloy material according to claim 3, wherein the Al content is 0.3% by mass or more and 0.9% by mass or less.

6. The copper alloy material according to claim 1 or 2, wherein the absolute value of the temperature coefficient of resistance (TCR) at 20°C to 50°C is 20 ppm / K or less.

7. The copper alloy material according to claim 3, wherein the absolute value of the temperature coefficient of resistance (TCR) at 20°C to 50°C is 20 ppm / K or less.

8. A resistor comprising the copper alloy material according to claim 1 or 2.

9. A resistor comprising the copper alloy material described in claim 3.

10. A resistor comprising the resistor described in claim 8.

11. A resistor comprising the resistor described in claim 9.

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