Copper alloy materials, resistors and resistors

Abstract

The present invention provides a copper alloy material that suppresses fluctuations in the temperature coefficient of resistance (TCR) and exhibits good solder wettability and molten alloy flowability, a resistor containing the copper alloy material, and a resistor equipped with the resistor. [Solution] 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.

Description

Technical Field

[0001] The present disclosure relates to copper alloy materials, resistive elements, and resistors.

Background Art

[0002] In the automotive field, with the recent trend of electrification, various types of electronic devices are being installed and their numbers are increasing. For this reason, the number of mounting points of 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 resistive element in a resistor is required to have stability in resistance temperature behavior, that is, a low temperature coefficient of resistance (TCR). In order to satisfy this characteristic, Cu-Mn-based alloys are widely used.

[0003] For example, Patent Document 1 discloses 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 characterized in that the ratio of the Mn content to the Cu content (surface layer [Mn / Cu] ratio) measured by Auger electron spectroscopy in the surface layer region partitioned 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% 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 mass% or more and 3.0 mass% or less, that when the amount of Al is less than 1.0 mass%, the effect of Al is small, and when the amount of Al exceeds 3.0 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 containing 6 wt% to 12 wt% manganese, 1 wt% to 3 wt% aluminum, 2 wt% to 3 wt% tin, and the remainder being copper. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6800387 [Patent Document 2] Patent No. 6471494 [Patent Document 3] Patent No. 4974544 [Overview of the Initiative] [Problems that the invention aims to solve]

[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 requires good solder wettability. Furthermore, when pouring the molten copper alloy (referred to as "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 containing the resistor. In this specification, "resistance" means electrical resistance. [Means for solving the problem]

[0009] One aspect of the present invention is: A copper alloy material for resistance, 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, Al: Contains 0.3% by mass or more and less than 1.0% by mass. It is a copper alloy material consisting of Cu and unavoidable impurities.

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

[0011] Embodiment 3 of the present invention is a copper alloy material according to Embodiment 1 or 2, obtained by pouring an alloy melt that has been melted in a nitrogen atmosphere and held at 1350°C into a Cu mold having a groove shape with a width of 12 mm to 14 mm and a long shape and an inclination angle of 5°, and having a ratio L / M of length L (mm) to mass M (g) of more than 1.6.

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

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

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

[0015] Embodiment 7 of the present invention is the 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 or more and 50°C or less is 20 ppm / K or less.

[0016] Embodiment 8 of the present invention is a resistor including the copper alloy material according to Embodiment 1 or 2.

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

[0018] Embodiment 10 of the present invention is a resistor provided with the resistor according to Embodiment 8.

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

Advantages of the Invention

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

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view schematically showing an apparatus for evaluating the flowability of molten alloy conducted in an example. [Figure 2] It is a diagram for explaining a method for evaluating the flowability of molten alloy conducted in an example. [Figure 3] It is a graph showing the relationship between solder wettability and molten alloy flowability in an example.

Modes for Carrying Out the Invention

[0022] In the conventional technology, from the viewpoints of the temperature coefficient of resistance (TCR) and workability, an Al content of 1.0 to 3.0 mass% has been considered desirable. However, as confirmed by the present inventors, it has been confirmed that if the Al content is 0.3 mass% or more, the oxidation resistance effect can be sufficiently exerted and the temperature coefficient of resistance (TCR) can be reduced. 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, and it has been found that the flowability of the molten alloy and the solder wettability are deteriorated. When the flowability of the molten alloy is poor, it becomes easy to entrain oxides during casting, and casting defects are likely to occur in the ingot, raising concerns about a deterioration in ingot quality. Also, if casting defects are likely to occur in the ingot, there is a possibility that hot rolling cracks may occur in the subsequent hot working process. Furthermore, when the solder wettability of the copper alloy material is low, there is a concern that the resistor may peel off when mounted on a substrate after being processed into a resistor 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 Mn segregation and oxidation 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 mass% or more and 14.0 mass% or less] The inclusion of 10.0% by mass or more of manganese in Cu reduces the TCR in the temperature range near room temperature, thereby suppressing temperature fluctuations in the material's volume resistivity. Therefore, the amount of manganese should be 10.0% by mass or more. On the other hand, if the amount of manganese exceeds 14.0% by mass, the volume resistivity of the material becomes too high, so the amount of manganese should be 14.0% by mass or less. The amount of manganese 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 the Cu, the absolute value of the material's thermoelectric voltage relative to copper can be reduced, thereby lowering the voltage generated when a temperature gradient occurs in the resistor and maintaining its performance as a resistor. 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 perspectives, the amount of Ni should be between 1.0 mass% and 4.0 mass%. 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, less than 1.0% by mass] When copper contains 0.3% by mass or more of aluminum (Al), Al oxidizes preferentially over manganese (Mn) when the material is held at high temperatures for extended periods. This suppresses segregation and oxidation of Mn on the surface, thereby reducing property changes due to oxidation of the material. On the other hand, if Al is included 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 between 0.3% by mass and less than 1.0% by mass. Preferably, the amount of Al is between 0.3% by mass and 0.9% by mass, and more preferably between 0.3% by mass and 0.7% by mass.

[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 due to the conditions of raw materials, materials, manufacturing equipment, etc., is acceptable as long as it does not significantly affect the TCR or volume resistivity. If the total amount of unavoidable impurities exceeds 0.5 mass%, the volume resistivity may become too high. Therefore, it is preferable that the total amount of unavoidable impurities be 0.5 mass% or less, for example, the total amount of unavoidable impurities such as Pb, Fe, Sn, Zn, Cr, Mg, P, S, and Si is 0.5 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) at 20°C to 50°C, as measured by the method described in the examples below, 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, as measured by the meniscography method, is 2.0 mN or higher, as described in the examples below. The maximum wetting stress (Fmax) is preferably 2.5 mN or higher, and more preferably 3.0 mN or higher.

[0033] (3) Flowability of molten alloy The good flowability of the molten alloy means that, as described in the examples below, the ratio of length L (mm) to mass M (g) of the ingot obtained by melting a copper alloy material in a nitrogen atmosphere and holding the molten alloy at 1350°C, and then pouring the resulting ingot into a Cu mold that is 12 mm to 14 mm wide, elongated, and has an inclination angle of 5°, is greater than 1.6. The L / M ratio is preferably 2.0 or higher, and more preferably 2.5 or higher.

[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. [Examples]

[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. Fabrication of copper alloy plate 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 to a thickness of approximately 20 mm to 15 mm, and finally 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, making rolling difficult, 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 characteristics 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)) From the obtained copper alloy plates, samples with dimensions of approximately 180mm to 250mm in length, 4mm in width, and 2mm in thickness were taken. Then, while controlling the sample temperature in a constant temperature bath (Julabo DDBC26, Julabo FP52SL), the resistance value of the sample at 20°C was measured using a resistance meter (HIOKI RM3543) with a four-terminal method. 20℃ (mΩ) and the resistance value R at 50℃ 50℃ (mΩ) was measured. Then TCR={(R 50℃ -R 20℃ ) / R 20℃} × {1 / (50 (°C) - 20 (°C))} × 10 6 The temperature coefficient of resistance (TCR) between 20°C and 50°C was calculated using the given formula. A TCR with an absolute value of 20 ppm / K or less was considered small. The results are shown in Table 1.

[0040] (Solder wettability) From the obtained copper alloy plate, a sample with dimensions of approximately 30 mm in length, 10 mm in width, and 0.4 mm in thickness was taken. 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. For the solder wettability test, a solder checker manufactured by RHESCA was used, and the measurement conditions were a solder bath temperature of 265°C, a material immersion rate of 25 mm / sec., an immersion depth of 12 mm, and an immersion time of 5 sec. In the solder wettability test, a maximum wetting stress (Fmax) of 2.0 mN or higher, measured by the meniscography method, was considered to indicate good solder wettability. The results are shown in Table 2.

[0041] (Flowability of molten alloy) The flowability of the molten alloy was evaluated using a small melting apparatus. First, approximately 50 g of copper alloy plates, prepared in the same manner as the copper alloy plates used for TCR measurement, were placed in a carbon crucible and melted in an electric furnace with nitrogen flow to obtain molten alloy. Then, the temperature of the molten alloy was maintained at 1350°C in the electric furnace, and as shown in Figure 1, the molten alloy was poured from the carbon crucible 1 into a Cu mold (Cu cooling tray) 2, which was groove-shaped, elongated, and had a 5° inclination angle, with a width of 12 mm to 14 mm, to produce an elongated alloy ingot 3 with a width of approximately 12 mm to 14 mm. The length L (mm) and mass M (g) of the alloy ingot 3 were then measured, and the length-to-mass ratio L / M was determined. For the measurement of length L, as shown in Figure 2, the length was measured at the 1 / 4, 1 / 2, and 3 / 4 positions of the width W of the alloy ingot 3, and the average value of these measurements was taken as the length L of the alloy ingot. In this example, a L / M ratio greater than 1.6 was evaluated as indicating good flowability of the molten alloy. Preferably, L / M was 2.0 or higher. The results are shown in Table 3.

[0042] [Table 1]

[0043] [Table 2]

[0044] [Table 3]

[0045] The results in Tables 1-3 are discussed. Samples No. 3-6 met 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 with ◆ or ■. 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, similar to that of solder wettability. Furthermore, based on the trends shown in Figure 3, it is thought that the flowability of samples No. 5 and 6 also shows a similar trend to that of solder wettability, as indicated by the diamond symbols in Figure 3. As a result, it is thought that the flowability of samples No. 5 and 6, like that of samples No. 3 and 4, will also show 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. [Explanation of Symbols]

[0047] 1. Carbon fiber crucible 2 Cu molds (Cu cooling trays) 3. Alloy ingot

Claims

1. A copper alloy material for resistance, 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, Al: Contains 0.3% by mass or more and less than 1.0% by mass. A copper alloy material consisting of 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 maintained at 1350°C, and the molten alloy is poured into a Cu mold that is groove-shaped and elongated with a width of 12 mm to 14 mm and has 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 temperatures between 20°C and 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 temperatures between 20°C and 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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