Resistor and method for manufacturing the same

Abstract

To protect a resistive element of a resistor without using a resin protective film and to suppress variation in its characteristics.SOLUTION: A resistor 10 includes a resistive element 12 and electrodes 14 and 16 provided on the resistive element 12, and the resistor 12 includes an oxide film 18 on its surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resistor and a method for making a resistor. [Background technology]

[0002] Patent Document 1 discloses a resistor for detecting a current, in which electrodes are joined to each end of a resistive element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-057009 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this resistor, there is a risk that solder or other foreign matter may adhere to the resistor, for example, when solder creeps up the electrodes to the resistor during mounting, etc. Therefore, a protective film made of resin or the like is formed to prevent the adhesion of solder and other foreign matter.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to protect a resistor without using a resin protective film and to suppress fluctuations in characteristics. [Means for solving the problem]

[0006] A resistor according to one embodiment of the present invention is a resistor including a resistive body and an electrode provided on the resistive body, The resistor has an upper surface, a lower surface, both side surfaces and both end surfaces, and the lower surface of the resistor faces the mounting surface on which the resistor is mounted and is exposed. It has an oxide film on its surface. Effect of the Invention

[0007] According to one embodiment of the present invention, the resistor has an oxide film on its surface, so that, for example, even if solder approaches the resistor along the electrodes, the oxide film prevents the solder from adhering to the resistor.

[0008] Even if the solder that has flowed down the electrodes reaches the resistor, an oxide film is present between the solder and the resistor, which prevents the solder from coming into direct contact with the resistor. This makes it possible to suppress fluctuations in resistance value compared to when the solder passes over the joint position between the resistor and the electrodes and comes into direct contact with the resistor.

[0009] In this way, the resistor is protected by the oxide film on its surface, which makes it possible to maintain the resistance characteristics for a long period of time. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a resistor according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of a main part of the resistor according to the first embodiment. [Diagram 3] FIG. 3 is an explanatory diagram showing a method for manufacturing the resistor according to the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing a method for manufacturing the resistor according to the second embodiment. [Diagram 5] FIG. 5 is an explanatory diagram showing a method for manufacturing the resistor according to the third embodiment. [Figure 6] FIG. 6 is an explanatory diagram showing a method for manufacturing the resistor according to the fourth embodiment. [Figure 7] FIG. 7 is a perspective view of a resistor according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First embodiment A resistor 10 according to a first embodiment will be described in detail with reference to Figures 1 and 2. Figure 1 is a perspective view of the resistor 10 according to the first embodiment. Figure 2 is a cross-sectional view of a main part of the resistor 10 according to the first embodiment.

[0012] The resistor 10 includes a resistive body 12, a first electrode 14 provided at one end of the resistive body 12, and a second electrode 16 provided at the other end of the resistive body 12. In the resistor 10, the first electrode 14, the resistive body 12, and the second electrode 16 are joined in this order.

[0013] The resistor 10 is mounted on a circuit board or the like not shown in Fig. 1. For example, the electrodes 14, 16 of the resistor 10 are connected by solder to lands formed on a wiring pattern of the circuit board. As an example, the resistor 10 is used as a current detection resistor (shunt resistor).

[0014] In this embodiment, the direction in which the first electrode 14 and the second electrode 16 are aligned (the longitudinal direction of the resistor 10) is defined as the X direction, the first electrode 14 side is defined as the +X direction, and the second electrode 16 side is defined as the -X direction. The width direction of the resistor 10 is defined as the Y direction, the front side of the paper in Fig. 1 is defined as the +Y direction, and the back side of the paper in Fig. 1 is defined as the -Y direction. Furthermore, the thickness direction of the resistor 10 is defined as the Z direction, the direction toward the circuit board is defined as the -Z direction, and the direction away from the circuit board is defined as the +Z direction. The X direction, Y direction, and Z direction are perpendicular to each other.

[0015] In addition, the mounting surface of resistor 10 means the surface of resistor 10 that faces the circuit board when resistor 10 is mounted on the circuit board, and includes the surfaces of first electrode 14, resistive body 12, and second electrode 16 that face the circuit board.

[0016] The resistor 12 is formed in a rectangular parallelepiped (or cube) shape. The resistor 12 has an oxide film 18 on its surface. More specifically, as shown in Fig. 1 and Fig. 2, the oxide film 18 is formed on a top surface 12A, both side surfaces 12B and 12C, and a bottom surface 12D of the resistor 12, and the resistor 12 is covered with the oxide film 18. In addition, the end surfaces 12E and 12F of the resistor 12 joined to the electrodes 14 and 16 do not have the oxide film 18.

[0017] The resistor 12 is made of a metal for a resistor. The metal for a resistor includes manganese (Mn). The resistor material for forming the resistor 12 is determined according to the application, and a material having a low resistance to a high resistance is used.

[0018] From the viewpoint of detecting a large current with high accuracy, the resistor 12 of this embodiment is preferably made of a resistor material having a low resistivity and a low temperature coefficient of resistance (TCR).

[0019] [Resistor material] A specific description will be given of the resistor material forming the resistor 12. The resistor material contains copper (Cu) and manganese (Mn) and is made of a Cu-Mn based alloy.

[0020] The surface of the resistor 12 made of this resistance material is modified to form a manganese oxide film 18. The oxide film 18 contains manganese oxide such as MnO or Mn3O4. It is preferable that the resistor 12 does not have the oxide film 18 on the bonding surfaces to be bonded to the electrodes 14, 16.

[0021] The resistor material contains manganese in an amount of 6% by mass to 35% by mass inclusive, based on the total mass ratio of the resistor material. If the manganese content is less than 6% by mass, it is difficult to form the manganese oxide film 18, and it is possible that the oxide film 18 may not have a sufficient thickness.

[0022] Furthermore, if the manganese content exceeds 35 mass %, the volume resistivity of the resulting resistor material will be higher than the required value, and the resistor material will become hard and its workability will decrease.

[0023] In addition to copper and manganese, resistor materials may also include aluminum, tin, nickel, chromium, and the like.

[0024] Resistor materials are required to be versatile and easy to form manganese oxide films. In addition, resistor materials are required to be easy to design to the required volume resistivity and temperature coefficient of resistance (TCR). As an example of a resistor material that satisfies these requirements, a Cu-Mn-Sn-based resistor material can be used.

[0025] The thickness of the oxide film 18 formed on the surface of the resistor material can be 70 nm or more.

[0026] There is no particular limitation on the thickness of the oxide film 18, but if the thickness of the oxide film 18 is less than 70 nm, it becomes difficult to ensure the desired resistance to deterioration of the resistor surface due to use of the resistor 12 made using the resistor material.

[0027] Although there is no upper limit to the thickness of the oxide film 18, peeling may occur depending on the thickness of the oxide film 18. For this reason, it is preferable that the thickness of the oxide film 18 does not exceed 2000 nm.

[0028] In addition, from the viewpoint of suppressing the influence of the formation of the oxide film 18 on the resistance temperature characteristics of the resistive material, the thickness of the oxide film 18 is preferably 1% or less of the total thickness of the resistor material. By reducing the thickness of the oxide film 18, the temperature coefficient of resistance (TCR) of the resistive material can be reduced to, for example, 100 ppm / °C or less, and the characteristics as a fixed resistor can be satisfied.

[0029] According to the above resistor material, since the manganese oxide film 18 is formed on the surface of the resistor material containing copper and manganese, the heat resistance of the resistor material can be improved. This makes it possible to increase the upper limit of the usable temperature of the resistor 10 using the resistor material. In turn, it makes it possible to increase the rated power of the resistor 10.

[0030] 1, the first electrode 14 includes a body 20 joined to the resistor 12, and a leg 22 formed integrally with the body 20 and extending toward the circuit board. The second electrode 16 includes a body 24 joined to the resistor 12, and a leg 26 formed integrally with the body 24 and extending toward the circuit board.

[0031] The first electrode 14 and the second electrode 16 are configured to contain a metal having a lower resistivity than the resistor 12. From the viewpoint of ensuring stable detection accuracy, the first electrode 14 and the second electrode 16 are preferably made of a conductive material having good electrical conductivity and thermal conductivity.

[0032] As an example, copper (Cu), a copper-based alloy, or the like can be used as the first electrode 14 and the second electrode 16. Of the copper materials, it is preferable to use oxygen-free copper (C1020). The first electrode 14 and the second electrode 16 can be the same as each other.

[0033] Body portion 20 of first electrode 14 has an end face having substantially the same shape as the end face in the +X direction of resistor 12. The end face of body portion 20 of first electrode 14 is joined to the end face in the +X direction of resistor 12 in an abutting state.

[0034] Body portion 24 of second electrode 16 has an end face having substantially the same shape as the end face in the -X direction of resistor 12. The end face of body portion 24 of second electrode 16 is joined to the end face in the -X direction of resistor 12 in an abutting state.

[0035] The leg 22 of the first electrode 14 extends in the -Z direction from the mounting surface of the resistor 10, i.e., the circuit board side of the body 20. The leg 22 of the first electrode 14 is shorter in the X direction than the body 20. The +X direction side of the leg 22 of the first electrode 14 forms the same plane as the +X direction side of the body 20.

[0036] The leg 26 of the second electrode 16 extends in the -Z direction from the mounting surface of the resistor 10, i.e., the circuit board side of the body 24. The leg 26 of the second electrode 16 has a length in the X direction shorter than that of the body 24. The side surface of the leg 26 of the second electrode 16 in the -X direction forms the same plane as the side surface of the body 24 in the -X direction.

[0037] The joint between the resistor 12 and the first electrode 14 and the joint between the resistor 12 and the second electrode 16 are joined by welding or the like, and are also joined to each other by, for example, clad bonding (solid-state bonding). That is, each of the joint surfaces is a diffusion bonded surface where metal atoms of the resistor 12 and the first electrode 14 are diffused into each other, and a diffusion bonded surface where metal atoms of the resistor 12 and the second electrode 16 are diffused into each other.

[0038] The resistor 10 is mounted on the circuit board so that the legs 22 and 26 protrude toward the circuit board, so that the resistor 10 is mounted on the circuit board with the resistive element 12 spaced apart from the circuit board.

[0039] The portion of the body 20 of the first electrode 14 that protrudes in the −X direction is a protrusion 30, and the protrusion 30 is joined to the resistor 12. Similarly, the portion of the body 24 of the second electrode 16 that protrudes in the +X direction is a protrusion 32, and the protrusion 32 is joined to the resistor 12.

[0040] In order to keep the length L (see FIG. 1) of resistor 10 in the X direction constant, the length of protrusion 30 in the X direction (length L1 of body 20, see FIG. 1) or the length of protrusion 32 in the X direction (length L2 of body 24 in the X direction, see FIG. 1) is adjusted as desired. In this case, the length L0 (see FIG. 1) of resistor 12 in the X direction can be adjusted as L0=L-(L1+L2).

[0041] Therefore, the resistance value of the resistor 10 can be adjusted as desired without changing the dimension L of the resistor 10 or the shape of each of the legs 22, 26. Alternatively, even if the amount of protrusion of each of the protrusions 30, 32 is increased without changing the dimension L of the resistor 10, the distance between the legs 22, 26 can be secured, so that the design freedom of the resistor 10 can be increased while securing the distance between the lands.

[0042] Here, the ratio of the length L0 of resistor 12 in the longitudinal direction (X direction) of resistor 12, the length L1 of first electrode 14 in the X direction, and the length L2 of second electrode 16 in the X direction can be set arbitrarily. However, from the viewpoint of reducing the resistance value while suppressing an increase in the temperature coefficient of resistance (TCR), it is preferable that L1:L0:L2=1:2:1 or close to 1:2:1.

[0043] Furthermore, from the viewpoint of increasing heat dissipation and decreasing the resistance value, it is preferable that the ratio of the length L0 of the resistive element 12 to the length L (=L1+L0+L2) of the resistor 10 is 50% or less.

[0044] The length L of the resistor 10 in the X direction is, for example, 3.2 mm or less, and the resistance value of the resistor 10 is, for example, adjusted to 2 mΩ or less.

[0045] In order to make the resistor 10 suitable for use in a high-density circuit board, the length L of the resistor 10 in the X direction can be 3.2 mm or less, and the length (width) W of the resistor 10 in the Y direction can be 1.6 mm or less (product standard 3216 size).

[0046] The size of the resistor 10 can be applied to the product standard 2012 size (L: 2.0 mm, W: 1.2 mm), the product standard 1608 size (L: 1.6 mm, W: 0.8 mm), and the product standard 1005 size (L: 1.0 mm, W: 0.5 mm). The advantage of forming the protective film of this embodiment is large in these small sizes or smaller sizes, but this embodiment may be applied to larger sizes.

[0047] The length L of resistor 10 may be set to a size equal to or larger than the above product standard 1005 size from the viewpoint of ease of handling in the manufacturing method described below, for example, from the viewpoint of preventing breakage of the resistor base material on which resistor 10 is based.

[0048] The resistance value of resistor 10 can be adjusted to 2 mΩ or less in any of the above sizes from the viewpoint of realizing a small size and low resistance, and can be adjusted to 0.5 mΩ or less as an example. The low resistance here is a concept including a resistance value lower than the resistance value expected from the dimensions of a general resistor (for example, a resistor of the type disclosed in JP 2002-57009 A).

[0049] The resistor 10 has chamfered corners P, which are edges extending in the Y direction. The radius of curvature of the corners P is preferably R=0.1 mm or less.

[0050] [Explanation of resistor manufacturing method] FIG. 3 is an explanatory diagram showing a method for manufacturing the resistor 10 of the first embodiment.

[0051] This manufacturing method includes a preparation step (a) of preparing materials, a joining step (b) of joining the materials, and a processing step (c) of processing the shape. The manufacturing method also includes a singulation step (d) of cutting the processed intermediate material into individual resistors 10, and an adjustment step (e) of adjusting the resistance value of the resistor 10 using a laser.

[0052] In the preparation step (a) of preparing materials, a resistor base material 40 which is the base material of the resistor 12, an electrode body base material 42 which is the base material of the first electrode 14, and an electrode body base material 44 which is the base material of the second electrode 16 are prepared. The resistor base material 40 and each of the electrode body base materials 42, 44 are long rectangular wire materials.

[0053] From the viewpoints of the size, resistance value and workability of the resistor 10, it is preferable to use a Cu--Mn alloy as the resistor base material 40 and to use oxygen-free copper (C1020) as the material for each of the electrode base materials 42, 44.

[0054] In the joining process (b) for joining the materials, the resistor base material 40 is placed between the electrode base materials 42, 44, and pressure is applied in the arrangement direction of the base materials 40, 42, 44 to join them together to form a resistor base material 46.

[0055] That is, in the joining step (b), so-called clad joining (solid-state joining) is performed between dissimilar metal materials. The joining surfaces between the clad-joined electrode body base materials 42, 44 and resistor body base material 40 become diffusion-joined surfaces in which the metal atoms of both materials are diffused into each other.

[0056] This makes it possible to firmly bond the joint surfaces of the resistor base material 40 and each of the electrode base materials 42, 44 to each other without performing conventional welding using an electron beam, etc. Furthermore, good electrical characteristics can be obtained at the joint surfaces of the resistor base material 40 and each of the electrode base materials 42, 44.

[0057] In the processing step (c), the resistor base material 46 obtained by clad bonding is inserted into and passes through an insertion hole 50 of a die 48 .

[0058] The through hole 50 of the die 48 is formed in a tapered shape that becomes smaller in diameter from the entrance to the exit. The through hole 50 is formed in a rectangular shape with the corners machined into a chamfered shape.

[0059] By passing the resistor base material 46 through the die 48 having such a shape, it is possible to compress and deform the resistor base material 46 in all directions. As a result, the cross-sectional shape of the resistor base material 46 becomes a shape that follows the cross-sectional shape of the insertion hole 50 of the die 48.

[0060] In this processing step (c), a drawing method is applied in which the resistor base material 46 is pulled out by a gripper when the resistor base material 46 passes through a die 48.

[0061] In the processing step (c), a plurality of dies 48 having insertion holes 50 of different sizes may be prepared, and the drawing process may be performed by passing the material through the plurality of dies 48 in stages.

[0062] A rectangular protrusion (not shown) is formed on the inner surface of the insertion hole 50 of the die 48, and a rectangular groove 52 that continues in the drawing direction is formed in the resistor base material 46 that passes through the insertion hole 50 by the protrusion.

[0063] When the resistor base material 46 is individually cut, the rectangular groove 52 forms a recess surrounded by the resistor 12 , the body 20 and leg 22 of the first electrode 14 , and the body 24 and leg 26 of the second electrode 16 .

[0064] In the singulation process (d), resistors 10 are cut out from resistor base material 46 to have a designed length W in the Y direction.

[0065] In the singulation process (d), it is preferable to cut the resistor base material 46 from the surface 52a where the rectangular groove 52 is formed to the opposite surface 52b. This causes metal burrs to extend upward from the upper surface of the resistor 10, and no burrs extending in the -Z direction (see FIG. 1) (burrs extending toward the circuit board) are generated in the legs 22, 26. This allows the resistor 10 to be reliably mounted on the circuit board.

[0066] Through the above steps, individual resistors 10 can be obtained from the resistor base material 46. Furthermore, in the adjustment step (e), the resistive element 12 is trimmed by laser irradiation to set the resistance value of the resistor 10 to a desired resistance value.

[0067] The trimmed resistor 10 is then subjected to a heat treatment to form an oxide film 18 on the surface of the resistor element 12. This heat treatment constitutes a forming step for forming the oxide film 18 on the surface of the resistor element 12. The above-mentioned adjustment step (e) may be performed after the heat treatment. Considering that the resistance value varies due to the heat treatment, it is preferable to trim the resistance value after the heat treatment step. In that case, a manganese oxide film is formed at the trimmed portion irradiated with a laser, which is preferable. The heat treatment will be specifically described below.

[0068] <Heat treatment (forming process)> The process of forming an oxide film on the resistive element 12 of the resistor 10 according to this embodiment will be described.

[0069] In this heat treatment, it is desired to form an oxide film 18 on the resistive element 12 of the resistor 10. However, it is not desired to oxidize the electrodes 14, 16. For this reason, the heat treatment is performed in a low oxygen concentration state.

[0070] In this process, a resistor 10 having a resistor 12 made of a resistive material containing copper and manganese is subjected to a heat treatment in a low-oxygen atmosphere at a temperature capable of oxidizing the resistor material for a predetermined period of time.

[0071] It is known that, in the electrode material and resistor material used in this embodiment, under a predetermined oxygen concentration condition, the oxidation reaction of the resistor material proceeds preferentially over the oxidation reaction of the electrode material.

[0072] In this embodiment, after evacuation, the atmosphere is replaced with nitrogen, thereby making it possible to obtain a preferable oxygen concentration condition.

[0073] A vacuum is a state in which the atmosphere is filled with gas at a pressure lower than the atmospheric pressure of normal air, so the oxygen concentration can be reduced. In addition, when the reaction system is purged with nitrogen, a certain amount of oxygen remains because it is usually difficult to completely remove oxygen and replace it with nitrogen.

[0074] In the case of a resistor 10 having a resistor 12 made of a resistor material containing copper and manganese as in this embodiment, it is preferable to apply a nitrogen atmosphere in which the oxygen concentration of the reaction system is 5 ppm or more and 30 ppm or less, from the viewpoint of oxidizing the resistor material.

[0075] In addition, the formation of the oxide film is thought to depend on the amount of heat applied. Therefore, when trying to obtain a desired film thickness, a long time is required if the temperature is low, but a short time is sufficient if the temperature is high.

[0076] Therefore, as an example, the temperature condition can be 400° C. or more and 800° C. or less, and the heat treatment time can be 10 minutes or more and 300 minutes or less.

[0077] If the temperature condition of the heat treatment is less than 400°C, it takes a long time to form a manganese oxide film of a thickness sufficient to ensure the desired resistance to deterioration of the resistor surface due to use of the resistor material.

[0078] Also, if the temperature condition of the heat treatment exceeds 800° C., although a thick oxide film can be formed, the resistor material may become soft, resulting in reduced workability.

[0079] The time condition of the heat treatment can be 10 minutes or more and 300 minutes or less depending on the temperature. If the heat treatment time is short at the same temperature, it is not possible to form a film thickness that can ensure the desired resistance against deterioration of the resistor surface. Also, if the heat treatment time exceeds 300 minutes, the oxide film becomes too thick and the temperature coefficient of resistance (TCR) becomes higher than the required value.

[0080] Although the oxide film grows even when the temperature is below 400°C, the reaction time increases, making it more difficult to carry out in practice. When the temperature is above 800°C, the desired film thickness can be obtained in a shorter time, but the resistor material may be deformed.

[0081] The terms "temperature condition" and "time condition" used in this embodiment are defined as follows. That is, "temperature condition" refers to the temperature reached by heating at a predetermined heating rate. The temperature condition "400°C or more and 800°C or less" refers to this reached temperature. Furthermore, "time condition" refers to the time for which the reached temperature is maintained. The heat treatment time condition "10 minutes or more and 300 minutes or less" refers to this retention time.

[0082] By carrying out the above heat treatment, it is possible to form a manganese oxide film 18 having a thickness of 70 nm or more on the surface of the resistor 12. The manganese oxide film 18 can improve the resistance of the surface of the resistor 12 to deterioration.

[0083] As a method for improving the resistance of the resistor 12 to surface deterioration, for example, a method of adding tin and / or aluminum in addition to copper and manganese and performing heat treatment has been proposed. In this proposal, an oxide film of tin and / or aluminum can be formed on the surface of the resistor 12.

[0084] However, in the case of resistor 12 made of an alloy containing tin and / or aluminum in addition to copper and manganese, the tin and / or aluminum may form spots inside resistor 12. In this case, under a required temperature that is higher than before, the resistance value may become unstable, or cracks may occur in the spots due to differences in thermal stress.

[0085] In response to this, the inventors have focused on oxide films such as MnO, Mn3O4, MnO2, and Mn2O3, and as a result of extensive investigation, have found that, among the above-mentioned manganese oxide films, MnO and Mn3O4 in particular contribute to preventing deterioration of resistor 12, which appears as discoloration of resistor 12.

[0086] An oxide film 18 of manganese, which is a component of resistor 12, is formed on the surface of resistor 12. This makes it possible to suppress the fluctuation in resistance value caused by deterioration of resistor 12, compared to the case where other metals such as tin and / or aluminum are added in addition to copper and manganese. In particular, it is considered important for preventing deterioration of resistor 12 that MnO or Mn3O4 is present in manganese oxide film 18.

[0087] Furthermore, the oxide film 18 obtained by the method for manufacturing the resistor 10 according to this embodiment not only improves the resistance against deterioration of the surface of the resistor 12 formed using a resistor material, but also has the advantage that the oxide film 18 is stable and does not peel off even when the resistor 12 is bent or cut, thereby increasing the degree of freedom in plastic processing of the resistor 12.

[0088] <Effects of this embodiment> Next, the effects of this embodiment will be described.

[0089] The resistor 10 of this embodiment includes a resistive element 12 and electrodes 14, 16 provided on the resistive element 12, and the resistive element 12 has an oxide film 18 on its surface.

[0090] According to the above configuration, resistor 12 has an oxide film 18 on its surface. Therefore, even if solder approaches resistor 12 along electrodes 14, 16, oxide film 18 prevents solder from adhering to resistor 12.

[0091] This makes it possible to prevent the surface of resistor 12 from being covered with resin or the like, and to prevent solder from directly adhering to resistor 12 .

[0092] Even if the solder that has flowed along the electrodes 14, 16 reaches the resistor 12, the oxide film 18 is interposed between the solder and the resistor 12. This prevents the solder from being directly connected to the resistor 12. This makes it possible to suppress fluctuations in the resistance value, compared to the case where the solder is directly connected to the center of the resistor rather than to the joint between the resistor 12 and the electrodes 14, 16.

[0093] Resistor element 12 is protected by surface oxide film 18. This prevents the characteristics of resistor 12 from changing, making it possible to maintain the resistance characteristics for a long period of time.

[0094] Therefore, resistor 12 can be protected without using a resin protective film, and fluctuations in characteristics can be suppressed.

[0095] In the resistor 10 of this embodiment, the resistive element 12 is made of a metal for a resistor, and each of the electrodes 14 and 16 is made of a metal having a lower resistivity than the resistive element 12 .

[0096] In the resistor 10 of this embodiment, the metal for the resistive element contains manganese, and a manganese oxide film 18 is formed on the surface of the resistor element 12.

[0097] According to this configuration, the metal for the resistor that forms the resistor 12 contains manganese. Therefore, as an example, it is possible to form an oxide film 18 by heat treating the resistor 12. In addition, the manganese oxide film 18 is formed on the surface of the resistor 12. Therefore, the effect of suppressing adhesion of solder to the resistor 12 is enhanced.

[0098] In the resistor 10 of this embodiment, the oxide film 18 contains MnO or Mn3O4.

[0099] This configuration enhances the effect of preventing solder from adhering to resistor 12.

[0100] Furthermore, according to the resistor manufacturing method of this embodiment, a manufacturing method of a resistor 10 having a resistive element 12 and each electrode 14, 16 provided on the resistive element 12 includes at least a formation step (heat treatment) of subjecting the resistive element 12 to heat treatment to form an oxide film 18 on the surface of the resistive element 12.

[0101] This configuration makes it possible to provide a resistor 10 in which an oxide film 18 is formed on the surface of the resistive element 12. In this resistor 10, even if solder approaches the resistive element 12 along the electrodes 14, 16, the oxide film 18 prevents the solder from adhering to the resistive element 12.

[0102] Even if the solder that has flowed along the electrodes 14, 16 reaches the resistor 12, the oxide film 18 is interposed between the solder and the resistor 12. This prevents the solder from being directly connected to the resistor 12. This makes it possible to suppress fluctuations in the resistance value of the resistor 10, compared to a case in which the solder is directly connected to the center of the resistor 12 closer to the joint positions of the resistor 12 and the electrodes 14, 16.

[0103] Resistor 12 is protected by oxide film 18 on the surface thereof. This suppresses changes in the characteristics of resistor 12, making it possible to maintain the resistance characteristics of resistor 12 for a long period of time.

[0104] Moreover, according to the method for manufacturing the resistor 10 of this embodiment, the forming step (heat treatment) forms the oxide film 18 on the surface of the resistive element 12 by subjecting the resistor 10 to heat treatment.

[0105] This configuration eliminates the need to remove the oxide film 18 formed on the electrode junctions of the resistor 12, as occurs when manufacturing the resistor 10 by joining the electrodes 14, 16 to the resistor 12 on which the oxide film 18 is formed. This makes it possible to reduce the number of manufacturing steps.

[0106] According to the manufacturing method of the resistor 10 of the present embodiment, the resistor 12 containing copper and manganese is subjected to a heat treatment in an atmosphere having an oxygen concentration of 30 ppm or less at 400° C. or more and 800° C. or less for 10 minutes or more and 300 minutes or less.

[0107] This allows the oxide film 18 to be formed on the surface of the resistor 12. In addition, since the heat treatment is performed in an atmosphere with an oxygen concentration of 30 ppm or less, the formation of an oxide film on the surfaces of the electrodes 14, 16 is suppressed even when the resistor 10 is heat treated.

[0108] Moreover, according to the method for manufacturing the resistor 10 of this embodiment, the oxygen concentration is 5 ppm or more and 30 ppm or less.

[0109] Furthermore, according to the method for manufacturing the resistor 10 of this embodiment, the heat treatment is performed in a nitrogen atmosphere with an oxygen concentration of 30 ppm or less.

[0110] This further enhances the effect of suppressing the formation of oxide films on the electrodes 14, 16.

[0111] Second Embodiment The resistor 100 according to the second embodiment will be described with reference to Fig. 4. Note that the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description will be omitted. Only the parts different from the first embodiment will be described.

[0112] 4 is an explanatory diagram showing a method for manufacturing the resistor 100 of the second embodiment. The resistor 100 of the second embodiment differs from the first embodiment in that the resistor 100 is formed using a resistor material having an oxide film 18 formed on the entire outer surface.

[0113] This manufacturing method includes an oxide film forming process (a-2), an oxide film removing process (b-2), a bonding process (c-2), and a singulation process (d-2). Note that a description of an adjustment process for adjusting the resistance value performed after the singulation process (d-2) is omitted.

[0114] In the oxide film forming step (a-2), a resistor base material 102 which is the base material of the resistor 12 is subjected to a heat treatment to form an oxide film 18 on the surface of the resistor base material 102. The material of the resistor base material 102 and the heat treatment method are the same as those in the first embodiment.

[0115] In the oxide film removing step (b-2), the oxide film 18 formed on both side surfaces 102E and 102F of the resistor base material 102 is removed. One method for removing the oxide film 18 is cutting.

[0116] In the bonding process (c-2), the electrode base materials 104, 106 are placed on the respective side surfaces 102E, 102F of the resistor base material 102 from which the oxide film 18 has been removed. In this state, pressure is applied in the arrangement direction of the base materials 102, 104, 106 to bond the base materials 102, 104, 106 together to form a resistor base material 108.

[0117] The base materials 102, 104, and 106 are joined by so-called clad joining (solid-state joining) between dissimilar metal materials, laser welding, electron beam welding, etc. The material of each of the electrode base materials 104 and 106 is the same as that in the first embodiment.

[0118] In the singulation process (d-2), the resistor base material 108 is cut to form the resistors 100. The cutting method is the same as in the first embodiment.

[0119] The resistor 100 according to this embodiment can also achieve the same effects as those of the first embodiment.

[0120] Third embodiment A resistor 120 according to the third embodiment will be described with reference to Fig. 5. Note that the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description will be omitted. Only the parts that differ from the first embodiment will be described.

[0121] 5 is an explanatory diagram showing a method for manufacturing the resistor 120 according to the third embodiment. The resistor 120 according to the third embodiment is different from the others in that the resistor 120 is formed using a resistive element 12 that is individualized and has an oxide film 18 formed on the surface.

[0122] This manufacturing method includes an oxide film forming step (a-3), an oxide film removing step (b-3), and a bonding step (c-3). Note that a description of an adjustment step for adjusting the resistance value, which is performed after the bonding step (c-3), is omitted.

[0123] In the oxide film forming step (a-3), the resistor elements 12 that have been individually cut in advance are subjected to a heat treatment to form an oxide film 18 on the entire outer surface of the resistor elements 12. The material of the resistor elements 12 and the heat treatment method are the same as those in the first embodiment.

[0124] The oxide film removing step (b-3) removes the oxide film 18 formed on both end faces 12E, 12F of the resistor 12. One method for removing the oxide film 18 is cutting.

[0125] In the bonding process (c-3), the electrodes 14, 16 are disposed on the respective end faces 12E, 12F of the resistor 12 from which the oxide film 18 has been removed. In this state, the first electrode 14 and the resistor 12 are bonded, and the second electrode 16 and the resistor 12 are bonded to form the resistor 120.

[0126] Examples of the joining method include laser welding, electron beam welding, etc. The materials of the electrodes 14, 16 are the same as those in the first embodiment.

[0127] The resistor 120 according to this embodiment can also achieve the same effects as those of the first embodiment.

[0128] (Fourth embodiment) A resistor 140 according to the fourth embodiment will be described with reference to Fig. 6. Note that the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description will be omitted. Only the parts that differ from the first embodiment will be described.

[0129] 6 is an explanatory diagram showing a manufacturing method of a resistor 140 according to the fourth embodiment. The resistor 140 according to the fourth embodiment is different from the others in that the first electrode 14 and the second electrode 16 are formed by cutting an electrode base material 144 laminated on a resistor base material 142.

[0130] This manufacturing method includes a preparation step (a-4) of preparing a plate-shaped resistor base material 142, a joining step (b-4) of joining a plate-shaped electrode base material 144 to the resistor base material 142, and a cutting step (c-4) of cutting the electrode base material 144. The manufacturing method also includes a cutting step (d-4) of cutting the cut resistor base material 148, and an oxide film forming step (e-4) of forming an oxide film 18 on the resistor 12 of the cut resistor 140. Note that a description of an adjustment step of adjusting the resistance value performed after the oxide film forming step (e-4) will be omitted.

[0131] In the preparation step (a-4), a plate-shaped (strip-shaped) resistor base material 142 is formed. The material of the resistor base material 142 is the same as that in the first embodiment.

[0132] In the bonding process (b-4), a plate-shaped electrode base material 144 is placed on the resistor base material 142. In this state, pressure is applied to both base materials 142, 144 in the stacking direction to bond the two base materials 142, 144 together to form a bonded base material 146.

[0133] The bonding between the two base materials 142, 144 is performed by so-called clad bonding (solid-state bonding) between dissimilar metal materials. The material of the electrode base material 144 is the same as that of the first embodiment.

[0134] In the cutting step (c-4), the center of the electrode base material 144 is cut to form a resistor base material 148. In the resistor base material 148, a first electrode 14 is formed on one side of the cut portion, and a second electrode 16 is formed on the other side.

[0135] In the cutting process (d-4), the resistor base material 148 is cut to a predetermined length to form the resistors 140. The cutting method is, for example, the same as that in the second embodiment.

[0136] In the oxide film forming process (e-4), the cut resistors 140 are heat-treated to form an oxide film 18 only on the surface of the resistor element 12. The heat treatment method is the same as in the first embodiment.

[0137] The resistor 140 according to this embodiment can also achieve the same effects as those of the first embodiment.

[0138] Fifth embodiment A resistor 160 according to the fifth embodiment will be described with reference to Fig. 7. Note that the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description will be omitted. Only the parts that differ from the first embodiment will be described.

[0139] 7 is a perspective view of a resistor 150 according to the fifth embodiment. A resistor 160 according to the fifth embodiment differs from the other embodiments in that a plurality of resistive elements 166 are disposed at a distance between a first electrode 162 and a second electrode 164.

[0140] The first electrode 162 and the second electrode 164 are made of the same material as in the first embodiment. Each of the electrodes 162, 164 is formed in a square plate shape, and a circular through hole 168, 170 is formed in the center of each of the electrodes 162, 164.

[0141] A plurality of resistors 166 are provided between the electrodes 162, 164, and the number of resistors 166 can be set arbitrarily. The resistors 166 are arranged at equal intervals on concentric circles centered on the through holes 168, 170, and each end of each resistor 166 is joined to the corresponding electrode 162, 164 by, for example, welding. In this way, the resistors 166 are connected in parallel.

[0142] Each resistor 166 is formed in a cylindrical shape, and is made of the same material as in the first embodiment. An oxide film 18 is formed on the peripheral surface of each resistor 166 by the above-mentioned heat treatment.

[0143] The shape of each of the electrodes 162, 164 is not limited to a rectangle, but may be a polygon such as a triangle, or a circle. The shape of the through holes 168, 170 is not limited to a circle, but may be a polygon such as a rectangle.

[0144] The resistor 160 according to this embodiment can achieve the same effects as those of the first embodiment. In this embodiment, the oxide film 18 is formed on the peripheral surfaces of all the resistor elements 166, but the oxide film may be formed on only the peripheral surfaces of some of the resistor elements 166 depending on the usage environment of the resistor.

[0145] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. EXAMPLES

[0146] The resistor 10 according to the first embodiment was subjected to heat treatment under various conditions, and the state of oxide film formation on the surfaces of the electrodes 14, 16 and the resistive element 12 of the obtained resistor 10 was evaluated.

[0147] A Cu-Mn-Sn based resistive material was used as the resistive material constituting the resistor 12 of the resistor 10. That is, the resistive material contains, in terms of the total mass ratio of the resistive material, 10 to 12 mass % of manganese, 1 to 4 mass % of nickel, and 84 to 89 mass % of copper.

[0148] The resistors 10 were subjected to heat treatment in an atmosphere with an oxygen concentration of 30 ppm or less, at a predetermined temperature of 200° C. to 800° C., for a predetermined time of 1 hour (60 minutes) to 5 hours (300 minutes). The surfaces of the electrodes 14, 16 and the resistive element 12 of the heat-treated resistors 10 were then observed. The results are shown in Table 1.

[0149] The oxide film formed was determined to be either "Mn3O4" or "MnO" using an X-ray analyzer. [Table 1]

[0150] As shown in Table 1, in the resistor 10 that was subjected to a heat treatment at 200° C. for 5 hours, the oxide film 18 was not formed on the resistive element 12 and the electrodes 14 and 16 .

[0151] Furthermore, the formation of a manganese oxide film 18 (Mn3O4) was confirmed on the resistive element 12 of the resistor 10 that had been subjected to heat treatment at 400°C for 1 hour, heat treatment at 400°C for 3 hours, and heat treatment at 400°C for 5 hours. On the other hand, the formation of an oxide film was not confirmed on the electrodes 14, 16 of the resistor 10 that had been subjected to heat treatment at 400°C for 1 hour, heat treatment at 400°C for 3 hours, and heat treatment at 400°C for 5 hours.

[0152] Furthermore, the formation of a manganese oxide film 18 (MnO) was confirmed on the resistive element 12 of each of the resistors 10 that had been subjected to heat treatment at 600°C for 1 hour, heat treatment at 600°C for 3 hours, and heat treatment at 600°C for 5 hours. On the other hand, the formation of an oxide film was not confirmed on the electrodes 14, 16 of the resistors 10 that had been subjected to heat treatment at 600°C for 1 hour, heat treatment at 600°C for 3 hours, and heat treatment at 600°C for 5 hours.

[0153] In addition, the resistor 10 that underwent heat treatment at 800°C for 1 hour and heat treatment at 800°C for 3 hours both showed the formation of a manganese oxide film 18 (MnO) on the resistive element 12. On the other hand, the electrodes 14, 16 of the resistor 10 that underwent heat treatment at 800°C for 1 hour and heat treatment at 800°C for 3 hours both showed no formation of an oxide film.

[0154] By forming the oxide film 18 on such a resistor 12, the resistor 12 is protected, and it is expected that changes in the characteristics of the resistor 10 are suppressed.

[0155] Then, each resistor 10 with manganese oxide film 18 formed on resistive element 12 was mounted on a circuit board, and each electrode 14, 16 of each resistor 10 was soldered to a land of a wiring pattern, and the state of adhesion of the solder to resistor 12 was visually observed. As a result, it was found that the effect differed depending on the state of formation of oxide film 18.

[0156] Specifically, in resistors 10 that were subjected to heat treatment at 600°C for 5 hours (resistors prepared for the experiment) and heat treatment at 800°C for 1 hour, the effect of suppressing adhesion of solder to the resistor element 12 was extremely good.

[0157] This is considered to be related to the thickness of the formed oxide film 18. From this result, when the heat treatment is performed at a lower temperature, the oxide film 18 can be made to have a desired thickness by performing the heat treatment for a long time.

[0158] Moreover, when the heat treatment is performed at a higher temperature, it is possible to shorten the heat treatment time required to form the oxide film 18 with a desired thickness. On the other hand, if the heat treatment time is too long, the formation of the oxide film 18 on each of the electrodes 14, 16 is promoted, so the heat treatment time is preferably set within a predetermined time. [Explanation of symbols]

[0159] 10, 100, 120, 140, 150, 160 resistors 12, 166 Resistor 14, 162 First electrode 16, 164 Second electrode 18 Oxide film

Claims

1. A resistor comprising a resistive body and an electrode provided on the resistive body, The resistor has an upper surface, a lower surface, both side surfaces, and both end surfaces, a lower surface of the resistor body facing a mounting surface on which the resistor is mounted, being exposed, and having an oxide film on the surface of the lower surface of the resistor body; resistor.

2. 2. The resistor of claim 1 , The resistor is configured to include a resistor metal, The electrode is configured to include a metal having a lower resistivity than the resistor. resistor.

3. 3. The resistor of claim 2, the metal for the resistor comprises manganese; The manganese oxide film is formed on the surface of the resistor. resistor.

4. 3. The resistor of claim 2, The oxide film includes MnO or Mn3O4. resistor.

5. A method for manufacturing a resistor comprising: a resistive element; and an electrode provided on the resistive element, the resistive element having an upper surface, a lower surface, both side surfaces and both end surfaces, the lower surface of the resistive element facing a mounting surface on which the resistor is mounted and exposed, and an oxide film on a surface of the lower surface of the resistive element, comprising: A forming step of forming an oxide film on a surface of the resistor by performing a heat treatment on the resistor. How resistors are manufactured.

6. A method for manufacturing a resistor according to claim 5, comprising the steps of: The forming step includes subjecting the resistor to the heat treatment to form the oxide film on the surface of the resistor. How resistors are manufactured.

7. A method for manufacturing a resistor according to claim 5 or 6, comprising the steps of: The resistor containing copper and manganese is subjected to the heat treatment in an atmosphere having an oxygen concentration of 30 ppm or less at 400° C. or more and 800° C. or less for 10 minutes or more and 300 minutes or less. How resistors are manufactured.

8. A method for manufacturing a resistor according to claim 7, comprising the steps of: The oxygen concentration is 5 ppm or more and 30 ppm or less. How resistors are manufactured.

9. A method for manufacturing a resistor according to claim 7 or 8, comprising the steps of: The heat treatment is performed in a nitrogen atmosphere having an oxygen concentration of 30 ppm or less. How resistors are manufactured.

Images