Resistors

Abstract

This resistor is provided with: a resistor body having a first surface and a second surface facing opposite sides in the thickness direction; a protective film disposed on the first surface and having an electric insulation property; and a pair of electrodes arranged apart from each other in a first direction orthogonal to the thickness direction and contacting the resistor body. The protective film has a first outer edge and a second outer edge that are separated from each other in the first direction and extend in a second direction orthogonal to both the thickness direction and the first direction. The resistor body has a first slit and a second slit passing through from the first surface to the second surface and extending in the second direction. The first slit is located closest to the first outer edge, and the second slit is located closest to the second outer edge. When viewed along the thickness direction, a first interval between the first outer edge and the first slit and a second interval between the second outer edge and the second slit both have a length of 15% or more of the dimension of the protective film in the first direction.

Description

[Technical Field]

[0001] The present disclosure relates primarily to resistors used for current sensing. [Background technology]

[0002] Conventionally, resistors having a resistive element made of a metal plate have been known. Such resistors are mainly used for current detection. Patent Document 1 discloses an example of a resistor having a resistive element made of a metal plate. The resistor includes a resistive element and a pair of electrodes formed on both ends of a surface of the resistive element facing one side in the thickness direction.

[0003] In recent years, resistors with a resistive element made of a metal plate have been required to have lower resistance values ​​in order to improve the accuracy of current detection. Meanwhile, as disclosed in Patent Document 1, slits are sometimes provided in the resistor to adjust the resistor's resistance value. In this case, it has been confirmed that providing a slit close to one of the pair of electrodes of the resistor results in a relatively high temperature coefficient of resistance (TCR) value of the resistor. It has also been confirmed that the lower the resistance value of the resistor, the higher the TCR value tends to be. The higher the TCR value, the greater the fluctuation in the resistor's resistance value due to heat generation from the resistive element during use, which reduces the accuracy of current detection using the resistor. Therefore, in resistors with slits provided in the resistor, it is necessary to suppress an increase in the TCR value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-225602 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above circumstances, an object of the present disclosure is to provide a resistor capable of suppressing an increase in the temperature coefficient of resistance. [Means for solving the problem]

[0006] A resistor according to one aspect of the present disclosure includes a resistive element having a first surface and a second surface facing opposite each other in a thickness direction, an electrically insulating protective film disposed on the first surface, and a pair of electrodes spaced apart in a first direction perpendicular to the thickness direction and in contact with the resistive element. The protective film has first and second outer edges spaced apart in the first direction and extending in a second direction perpendicular to both the thickness direction and the first direction. The resistive element has first and second slits penetrating from the first surface to the second surface and extending in the second direction, the first slit being located closest to the first outer edge, and the second slit being located closest to the second outer edge. When viewed along the thickness direction, a first distance between the first outer edge and the first slit and a second distance between the second outer edge and the second slit are both 15% or more of the dimension of the protective film in the first direction.

[0007] Preferably, the first interval and the second interval are equal to each other when viewed along the thickness direction.

[0008] Preferably, each of the pair of electrodes has a bottom portion located on the opposite side of the protective film from the resistor in the thickness direction, and each of the bottom portions of the pair of electrodes includes a portion that overlaps with a part of the protective film when viewed along the thickness direction.

[0009] Preferably, the protective film is made of a material containing synthetic resin.

[0010] Preferably, the protective film contains a filler made of a material containing ceramics.

[0011] Preferably, when viewed along the thickness direction, the first slit overlaps the bottom of one of the pair of electrodes, and when viewed along the thickness direction, the second slit overlaps the bottom of the other of the pair of electrodes.

[0012] Preferably, when viewed along the thickness direction, the first gap and the second gap each have a length that is 30% or less of the dimension of the protective film in the first direction.

[0013] Preferably, the resistor has a pair of first end faces connected to both the first surface and the second surface and spaced apart from each other in the first direction, each of the pair of electrodes has a side portion connected to one of the bottom portions of the pair of electrodes and standing up in the thickness direction, and each of the side portions of the pair of electrodes is in contact with one of the pair of first end faces.

[0014] Preferably, the resistor further includes an insulating plate disposed on the second surface and made of a material containing synthetic resin. The resistor element has a pair of second end faces connected to both the first surface and the second surface and spaced apart in the second direction, and the pair of second end faces are covered by the insulating plate.

[0015] Preferably, each of the side portions of the pair of electrodes is in contact with the insulating plate.

[0016] Preferably, the first slit extends in the second direction from one of the pair of second end faces, and the second slit extends in the second direction from the other of the pair of second end faces.

[0017] Preferably, a portion of the insulating plate penetrates into the first slit and the second slit in the thickness direction.

[0018] Preferably, each of the first slit and the second slit has a pair of side walls spaced apart from each other in the first direction, and each of the pair of side walls includes a portion recessed in the first direction.

[0019] Preferably, the resistor has a protrusion protruding from one of the pair of second end faces in the second direction, the protrusion being connected to one of the pair of first end faces, and one of the bottoms of the pair of electrodes being in contact with the protrusion.

[0020] Preferably, the resistor has a plurality of grooves recessed from the first surface and extending in a predetermined direction, and the protective film is engaged with the plurality of grooves.

[0021] Preferably, the resistor further includes a pair of intermediate layers located between the resistive element and the bottoms of the pair of electrodes in the thickness direction, each of the pair of intermediate layers having a covering portion that covers a part of the protective film, and each of the bottoms of the pair of electrodes being in contact with one of the covering portions of the pair of intermediate layers.

[0022] Preferably, when viewed along the thickness direction, the first outer edge and the second outer edge are located between the pair of first end faces, the first surface includes a first region and a second region that are not covered by the protective film or the pair of intermediate layers, the first region being located between the first outer edge and one of the pair of first end faces that is closest to the first outer edge, and the second region being located between the second outer edge and one of the pair of first end faces that is closest to the second outer edge, and each of the first region and the second region is in contact with one of the bottoms of the pair of electrodes.

[0023] According to the above-described configuration of the resistor, it is possible to suppress an increase in the temperature coefficient of resistance.

[0024] Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a plan view of a resistor according to a first embodiment. [Figure 2] 2 is a plan view of the resistor shown in FIG. 1, seen through an insulating plate. [Figure 3] FIG. 2 is a bottom view of the resistor shown in FIG. [Figure 4] FIG. 4 is a bottom view corresponding to FIG. 3, showing a pair of electrodes in perspective. [Figure 5] 5 is a bottom view corresponding to FIG. 4, showing through a pair of intermediate layers. [Figure 6] FIG. 2 is a right side view of the resistor shown in FIG. [Figure 7] FIG. 2 is a front view of the resistor shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 2. [Figure 9] FIG. 9 is a partially enlarged view of FIG. 8. [Figure 10] FIG. 9 is a partially enlarged view of FIG. 8. [Figure 11] FIG. 9 is a partially enlarged view of FIG. 8. [Figure 12] 2A to 2C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. [Figure 13] 2A to 2C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. [Figure 14] 2A to 2C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. [Figure 15] 2A to 2C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. [Figure 16] 2A to 2C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. [Figure 17] 2A to 2C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. [Figure 18] 2 is a graph showing the temperature coefficient of resistance of the resistor shown in FIG. 1 and a resistor of a comparative example. [Figure 19] FIG. 10 is a plan view of a resistor according to a second embodiment, seen through an insulating plate. [Figure 20] 20 is a bottom view of the resistor shown in FIG. 19, showing a pair of electrodes. [Figure 21] FIG. 20 is a front view of the resistor shown in FIG. 19. [Figure 22]FIG. 22 is a cross-sectional view taken along line XXII-XXII in FIG. [Figure 23] 20A to 20C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. 19. [Figure 24] 20A to 20C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. 19. [Figure 25] 20A to 20C are cross-sectional views illustrating a manufacturing process of the resistor shown in FIG. 19. DETAILED DESCRIPTION OF THE INVENTION

[0026] Various embodiments of the present disclosure are described below with reference to the accompanying drawings.

[0027] A resistor A10 according to a first embodiment will be described with reference to FIGS. 1 to 11. The resistor A10 is a shunt resistor used for current detection. The resistor A10 has a main resistance value of 5 mΩ. The resistor A10 is surface-mounted on the wiring boards of various electronic devices. The resistor A10 includes a resistive element 10, an insulating plate 20, a protective film 30, a pair of intermediate layers 40, and a pair of electrodes 50. For ease of understanding, FIG. 2 shows a perspective view of the insulating plate 20. For ease of understanding, FIG. 4 shows a perspective view of the pair of electrodes 50. In FIG. 5, the perspective view of the pair of intermediate layers 40 and the pair of electrodes 50 are shown. In these figures, the perspective view of the pair of intermediate layers 40 and the pair of electrodes 50 is indicated by imaginary lines (chain double-dashed lines).

[0028] In the description of the resistor A10, the direction along the thickness of the resistor A10 is referred to as the "thickness direction z." A direction perpendicular to the thickness direction z is referred to as the "first direction x." A direction perpendicular to both the thickness direction z and the first direction x is referred to as the "second direction y." The "thickness direction z," "first direction x," and "second direction y" also apply to the description of the resistor A20 described below. As shown in FIG. 1, the resistor A10 is rectangular when viewed along the thickness direction z. The first direction x corresponds to the longitudinal direction of the resistor A10. The second direction y corresponds to the lateral direction of the resistor A10.

[0029] Resistor element 10 is the functional core of resistor A10. Resistor element 10 is a metal plate. The material of the metal plate is, for example, a copper (Cu)-manganese (Mn)-nickel (Ni) alloy (Manganin: registered trademark) or a copper-manganese-tin (Sn) alloy (Zeranin: registered trademark). The thickness of resistor element 10 is 50 μm or more and 150 μm or less.

[0030] As shown in FIGS. 7 and 8, the resistor 10 has a first surface 10A, a second surface 10B, a pair of first end surfaces 10C, and a pair of second end surfaces 10D. The first surface 10A faces in one direction in the thickness direction z. The second surface 10B faces the opposite side from the first surface 10A. Therefore, the first surface 10A and the second surface 10B face opposite sides in the thickness direction z. The pair of first end surfaces 10C are spaced apart from each other in the first direction x. Each of the pair of first end surfaces 10C is connected to both the first surface 10A and the second surface 10B. The pair of second end surfaces 10D are spaced apart from each other in the second direction y. Each of the pair of second end surfaces 10D is connected to both the first surface 10A and the second surface 10B.

[0031] As shown in FIGS. 2 and 8, the resistor 10 has a first slit 111 and a second slit 112. The first slit 111 and the second slit 112 are provided to adjust the resistance value of the resistor 10 to a predetermined value. The first slit 111 and the second slit 112 are spaced apart from each other in the first direction x. Each of the first slit 111 and the second slit 112 penetrates the resistor 10 from the first surface 10A to the second surface 10B. The first slit 111 extends in the second direction y from one of the pair of second end surfaces 10D. The second slit 112 extends in the second direction y from the other of the pair of second end surfaces 10D.

[0032] As shown in FIG. 9, the first slit 111 has a pair of side walls 11A. Although not shown, the second slit 112 also has a pair of side walls 11A similar to the first slit 111. The pair of side walls 11A are spaced apart from each other in the first direction x. Each of the pair of side walls 11A is connected to both the first surface 10A and the second surface 10B. Each of the pair of side walls 11A includes a portion that is concave in the first direction x.

[0033] As shown in FIGS. 5 and 10, the resistor 10 includes a plurality of grooves 12, which, together with the first slits 111 and the second slits 112, are provided to adjust the resistance of the resistor 10 to a predetermined value. The grooves 12 are recessed from the first surface 10A and extend in a predetermined direction. In the example of resistor A10, each of the grooves 12 extends in the second direction y. The grooves 12 are located between the first slits 111 and the second slits 112 in the first direction x. As shown in FIG. 10, the maximum width bmax of each of the grooves 12 is smaller than the minimum width Bmin (see FIG. 9) of each of the first slits 111 and the second slits 112.

[0034] 2, 4, and 7, the resistor 10 has four protrusions 14. When viewed along the thickness direction z, the four protrusions 14 are located at the four corners of the resistor 10. Each of the four protrusions 14 protrudes from one of the pair of second end faces 10D in the second direction y. Each of the four protrusions 14 is connected to one of the pair of first end faces 10C.

[0035] The shape of resistor 10 is point-symmetric when viewed along the thickness direction z. Point symmetry in this case means that when resistor 10 is divided into two sections by a boundary N that passes through the center C of resistor 10 shown in Figure 2 and extends in the second direction y, one section and the other section are in a point-symmetric relationship with respect to the center C.

[0036] As shown in FIG. 8, the insulating plate 20 is disposed on the second surface 10B of the resistor 10. The insulating plate 20 is made of a material containing synthetic resin. In the example of the resistor A10, the insulating plate 20 is a synthetic resin sheet containing epoxy resin. As shown in FIGS. 1 and 7, the pair of second end surfaces 10D of the resistor 10 are covered with the insulating plate 20. As shown in FIGS. 1, 6, and 8, the insulating plate 20 has a pair of end surfaces 20A. The pair of end surfaces 20A face opposite each other in the first direction x and are spaced apart from each other in the first direction x. Each of the pair of end surfaces 20A is flush with one of the pair of first end surfaces 10C. As shown in FIG. 8, a portion of the insulating plate 20 penetrates the first slits 111 and the second slits 112 of the resistor 10 in the thickness direction z.

[0037] As shown in FIG. 8, the protective film 30 is disposed on the first surface 10A of the resistor 10. The protective film 30 is made of an electrically insulating material containing synthetic resin. In the example of resistor A10, the protective film 30 is made of a material containing epoxy resin. As shown in FIGS. 9 and 10, the protective film 30 contains filler 31. The filler 31 is made of a material containing ceramic. The ceramic is preferably alumina (Al2O3) or boron nitride (BN) with a relatively high thermal conductivity. The protective film 30 covers a portion of the first surface 10A and a portion of the insulating plate 20 that penetrates the first slit 111 and the second slit 112 of the resistor 10. As shown in FIG. 10, the protective film 30 engages with the grooves 12 of the resistor 10.

[0038] As shown in FIGS. 2, 5, and 8, the protective film 30 has a first outer edge 30A and a second outer edge 30B. The first outer edge 30A and the second outer edge 30B are spaced apart from each other in the first direction x and extend in the second direction y. The first outer edge 30A is located closest to the first slit 111 of the resistor 10. The second outer edge 30B is located closest to the second slit 112 of the resistor 10. When viewed along the thickness direction z, a first distance L1 between the first outer edge 30A and the first slit 111 and a second distance L2 between the second outer edge 30B and the second slit 112 are both 15% to 30% of the dimension L0 of the protective film 30 in the first direction x. The first distance L1 refers to the shortest distance from the boundary between the pair of side walls 11A of the first slit 111 and the first surface 10A of the resistor 10 to the first outer edge 30A. Similarly, the second distance L2 refers to the shortest distance from the boundary between the pair of side walls 11A of the second slit 112 and the first surface 10A to the second outer edge 30B. Note that the dimension L0 is equal to the distance between the first outer edge 30A and the second outer edge 30B. When viewed along the thickness direction z, the first distance L1 and the second distance L2 are equal to each other.

[0039] 2, the first distance L1 and the second distance L2, which are equal to 15% of the dimension L0 of the protective film 30 in the first direction x, are indicated as the first distance L1min and the second distance L2min, respectively. Additionally, the first distance L1 and the second distance L2, which are equal to 30% of the dimension L0 of the protective film 30 in the first direction x, are indicated as the first distance L1max and the second distance L2max, respectively.

[0040] As shown in FIGS. 4, 5, and 8, the first outer edge 30A and the second outer edge 30B of the protective film 30 are located between the pair of first end faces 10C of the resistor 10 when viewed along the thickness direction z. The first face 10A of the resistor 10 includes a first region 131 and a second region 132 that are not covered by either the protective film 30 or the pair of intermediate layers 40. The first region 131 is located between the first outer edge 30A and one of the pair of first end faces 10C that is closest to the first outer edge 30A. The second region 132 is located between the second outer edge 30B and one of the pair of first end faces 10C that is closest to the second outer edge 30B.

[0041] As shown in FIG. 8 , the pair of intermediate layers 40 are located between the resistor 10 and the bottoms 51 (described in detail later) of the pair of electrodes 50 in the thickness direction z. The pair of intermediate layers 40 are spaced apart from each other in the first direction x. The pair of intermediate layers 40 are conductive. In the resistor A10, the pair of intermediate layers 40 are made of a material that is conductive and contains a synthetic resin. The pair of intermediate layers 40 contain metal particles. The metal particles contain silver (Ag). In the example of the resistor A10, the synthetic resin contained in the pair of intermediate layers 40 is an epoxy resin. The electrical resistivity of the pair of intermediate layers 40 is approximately 10 times that of the resistor 10. Therefore, the electrical resistivity of the pair of intermediate layers 40 is greater than that of the resistor 10.

[0042] As shown in FIGS. 4 and 8 , each of the pair of intermediate layers 40 has a covering portion 41 and an extending portion 42. The covering portion 41 is located on the opposite side of the protective film 30 from the resistor 10 in the thickness direction z. The covering portion 41 covers a portion of the protective film 30. The extending portion 42 extends from one of the covering portions 41 of the pair of intermediate layers 40 toward one of the pair of first end faces 10C of the resistor 10. The extending portion 42 is in contact with the first surface 10A of the resistor 10. This provides electrical continuity between the pair of intermediate layers 40 and the resistor 10.

[0043] As shown in FIGS. 2, 4, and 8, each of the pair of intermediate layers 40 includes a first layer 40A and a second layer 40B. The first layer 40A has an extension 42 and is in contact with the first surface 10A of the resistor 10. The dimension of the first layer 40A in the thickness direction z is approximately uniform throughout. The second layer 40B has a covering portion 41. The second layer 40B is in contact with either of the first layers 40A of the pair of intermediate layers 40. The second layer 40B is configured to cover a portion of the first layer 40A.

[0044] 4, a notch 421 is formed in each of the extending portions 42 of the pair of intermediate layers 40. The notch 421 is recessed from one of the pair of first end faces 10C in the first direction x. Either the first region 131 or the second region 132, each including a pair of protrusions 14 of the resistor 10, is exposed from the notch 421.

[0045] 11 , each of the first layers 40A of the pair of intermediate layers 40 has an intervening portion 43 extending from the extending portion 42 toward the protective film 30. The intervening portion 43 includes a portion located between the resistor 10 and the protective film 30. As a result, each of the opposite ends of the protective film 30 in the first direction x is configured to cover one of the first layers 40A of the pair of intermediate layers 40. The intervening portion 43 is in contact with both the resistor 10 and the protective film 30.

[0046] As shown in FIGS. 1 to 3, 6, and 8, the pair of electrodes 50 are spaced apart from each other in the first direction x. Each of the pair of electrodes 50 is in contact with the resistor 10. This allows the pair of electrodes 50 to be electrically connected to the resistor 10. Each of the pair of electrodes 50 is made up of a plurality of metal layers. In the example shown in resistor A10, the plurality of metal layers are formed by laminating a copper layer, a nickel layer, and a tin layer in order from the side closest to the resistor 10.

[0047] As shown in FIG. 3 and FIGS. 6 to 8 , each of the pair of electrodes 50 has a bottom 51. The bottom 51 is located on the opposite side of the protective film 30 from the resistor 10 in the thickness direction z. The bottom 51 of the pair of electrodes 50 includes a portion that overlaps with a part of the protective film 30 when viewed along the thickness direction z. As shown in FIG. 2 , the first slit 111 of the resistor 10 overlaps with the bottom 51 of one of the pair of electrodes 50 when viewed along the thickness direction z. In addition, the second slit 112 of the resistor 10 overlaps with the bottom 51 of the other of the pair of electrodes 50 when viewed along the thickness direction z.

[0048] 6 and 8, each of the bottom portions 51 of the pair of electrodes 50 contacts both the covering portion 41 and the extending portion 42 of one of the pair of intermediate layers 40. In addition, as shown in Fig. 7 and 8, each of the bottom portions 51 of the pair of electrodes 50 contacts either the first region 131 or the second region 132 of the resistor 10 and two protrusions 14 adjacent to either of the pair of first end faces 10C of the resistor 10.

[0049] As shown in FIGS. 1 to 3 and 6 to 8 , each of the pair of electrodes 50 has a side portion 52. The side portion 52 is connected to one of the bottom portions 51 of the pair of electrodes 50 and stands upright in the thickness direction z. Each of the side portions 52 of the pair of electrodes 50 contacts one of the pair of first end faces 10C of the resistor 10. In addition, each of the side portions 52 of the pair of electrodes 50 contacts one of the pair of end faces 20A of the insulating plate 20.

[0050] Next, an example of a method for manufacturing the resistor A10 will be described with reference to Figures 12 to 17. The cross-sectional positions shown in Figures 12 to 17 are the same as the cross-sectional position shown in Figure 8.

[0051] First, as shown in FIG. 12 , a substrate 82 is thermocompression-bonded to a resistor 81 having a first surface 81A and a second surface 81B facing opposite each other in the thickness direction z. The resistor 81 is formed by connecting a plurality of resistor elements 10 of a resistor A10 in a first direction x and a second direction y. The first surface 81A corresponds to the first surface 10A of the resistor element 10. The second surface 81B corresponds to the second surface 10B of the resistor element 10. The substrate 82 is formed by connecting a plurality of insulating plates 20 of the resistor A10 in a first direction x and a second direction y. First, a plurality of slits 811 are formed in the resistor 81, penetrating from the first surface 10A to the second surface 81B. The plurality of slits 811 correspond to the first slits 111 and the second slits 112 of the resistor element 10. The plurality of slits 811 are formed by wet etching. Next, the substrate 82 is thermocompression-bonded to the second surface 81B by lamination pressing. When the substrate 82 is thermocompression bonded to the second surface 81B, parts of the substrate 82 penetrate into the multiple slits 811 in the thickness direction z. Finally, with a probe for measuring the resistance value of the resistor 81 in contact with the first surface 10A, multiple grooves 812 recessed from the first surface 10A are formed in the resistor 81. The multiple grooves 812 correspond to the multiple grooves 12 in the resistor 10. The multiple grooves 12 are formed, for example, by laser irradiation. When the resistance value of the resistor 81 reaches a predetermined value, the formation of the multiple grooves 812 is completed.

[0052] Next, as shown in FIG. 13, the first layers 40A of the pair of intermediate layers 40 are formed to cover a portion of the first surface 81A of the resistor 81. To form the first layers 40A of the pair of intermediate layers 40, a material containing silver particles and epoxy resin is applied to the first surface 81A by screen printing. At this time, the material is applied while being spaced apart from each other in the first direction x. Thereafter, the material is thermally cured to form the first layers 40A of the pair of intermediate layers 40.

[0053] 14, a protective film 30 is formed to cover a portion of the first surface 81A of the resistor 81 and a portion of the base material 82 that penetrates into the multiple slits 811 of the resistor 81. First, a material containing epoxy resin is applied by screen printing to a portion of the first surface 81A so as to completely cover the portion of the base material 82 that penetrates into the multiple slits 811. At this time, each of both ends of the material in the first direction x is arranged to cover one of the first layers 40A of the pair of intermediate layers 40. Thereafter, the material is thermally cured to form the protective film 30.

[0054] Next, as shown in FIG. 15, the second layer 40B of the pair of intermediate layers 40 is formed to cover a portion of the protective film 30. First, a material containing silver particles and epoxy resin is applied to the protective film 30 by screen printing. At this time, the material is applied while being spaced apart from each other in the first direction x. At the same time, each spaced apart portion of the material is made to cover a portion of one of the first layers 40A of the pair of intermediate layers 40. The material is then thermally cured to form the second layer 40B of the pair of intermediate layers 40.

[0055] Next, as shown in FIG. 16 , the resistor 81 and the substrate 82 are cut along cutting lines CL with a dicing blade to separate them into individual pieces each including a protective film 30 and a pair of intermediate layers 40 (first layer 40A and second layer 40B). The individual pieces become the components of the resistor A10 excluding the pair of electrodes 50. That is, the resistor 81 separated into individual pieces becomes the resistors 10 of the resistor A10. In addition, the substrate 82 separated into individual pieces becomes the insulating plate 20 of the resistor A10. Note that the pair of first end faces 10C of the resistor 10 are the cut surfaces of the resistor 81 that appear in this process. In addition, the pair of end faces 20A of the insulating plate 20 are the cut surfaces of the substrate 82 that appear in this process.

[0056] Finally, as shown in FIG. 17, a pair of electrodes 50 are formed in contact with the resistor 10. The pair of electrodes 50 are formed by electrolytic barrel plating of a copper layer, a nickel layer, and a tin layer, in that order. Each of the pair of intermediate layers 40 is covered by one of the bottom portions 51 of the pair of electrodes 50. Each of the bottom portions 51 of the pair of electrodes 50 contacts either the first region 131 or the second region 132 of the resistor 10 and the protective film 30. In addition, each of the pair of first end faces 10C of the resistor 10 and a portion of each of the pair of end faces 20A of the insulating plate 20 are covered by one of the side portions 52 of the pair of electrodes 50. Next, the pair of electrodes 50 is heat-treated at a temperature of 170°C for two hours. This improves the bonding strength between each of the bottom portions 51 of the pair of electrodes 50 and the resistor 10. Through the above steps, the resistor A10 is manufactured.

[0057] Next, the function and effect of the resistor A10 will be described.

[0058] The resistor A10 includes a resistive element 10, a protective film 30 disposed on a first surface 10A of the resistive element 10, and a pair of electrodes 50 spaced apart in a first direction x and in contact with the resistive element 10. The resistive element 10 has a first slit 111 and a second slit 112. The protective film 30 has a first outer edge 30A located closest to the first slit 111 and a second outer edge 30B located closest to the second slit 112. In the resistor A10, when viewed along the thickness direction z, a first distance L1 between the first outer edge 30A and the first slit 111 and a second distance L2 between the second outer edge 30B and the second slit 112 are both 15% or more of a dimension L0 of the protective film 30 in the first direction x.

[0059] FIG. 18 shows the resistance variation coefficient (unit: 10 ) of the resistor A10 and the resistor of the comparative example when the temperature of the resistor 10 is varied in the range of 20° C. or more and 60° C. or less. -618 shows the temperature (°C) of the protective film 30 in the first direction x. In FIG. 18, the length of each of the first slits 111 and the second slits 112 in Comparative Example-1 is equal to the length of each of the first slits 111 and the second slits 112 in the resistor A10-1. Similarly, the length of each of the first slits 111 and the second slits 112 in Comparative Example-2 is equal to the length of each of the first slits 111 and the second slits 112 in the resistor A10-2. In each of Comparative Examples-1 and -2, when viewed along the thickness direction z, the first distance L1 between the first outer edge 30A and the first slit 111 and the second distance L2 between the second outer edge 30B and the second slit 112 are both less than 15% of the dimension L0 of the protective film 30 in the first direction x.

[0060] 18, the resistance variation coefficient of resistor A10-1 is reduced by approximately 50% compared to that of Comparative Example 1. Similarly, the resistance variation coefficient of resistor A10-2 is reduced by approximately 50% compared to that of Comparative Example 2. Therefore, resistor A10 makes it possible to suppress an increase in the temperature coefficient of resistance.

[0061] Furthermore, in the resistor A10, when viewed along the thickness direction z, the first distance L1 between the first outer edge 30A and the first slit 111 and the second distance L2 between the second outer edge 30B and the second slit 112 are both 30% or less of the dimension L0 of the protective film 30 in the first direction x. If the distance between the first slit 111 and the second slit 112 is too close, the temperature rise in the region of the resistive element 10 sandwiched between the first slit 111 and the second slit 112 becomes significant during use of the resistor A10. This condition causes fluctuations in the resistance value of the resistor A10. Therefore, by adopting this configuration, excessive temperature rise in the region of the resistive element 10 sandwiched between the first slit 111 and the second slit 112 is prevented, thereby suppressing fluctuations in the resistance value of the resistor A10 due to temperature rises in the resistive element 10.

[0062] In the resistor A10, when viewed along the thickness direction z, the first slit 111 overlaps the bottom portion 51 of one of the pair of electrodes 50. Similarly, the second slit 112 overlaps the bottom portion 51 of the other of the pair of electrodes 50. In the resistor 10, the resistance value is locally higher in the regions adjacent to each of the first slit 111 and the second slit 112 in the second direction y compared to other regions. Therefore, when the resistor A10 is in use, the temperature of the region becomes higher than the other regions. Therefore, by adopting this configuration, heat generated from the region is transferred to the pair of bottom portions 51, preventing an excessive temperature rise in the region.

[0063] The resistor 10 has a plurality of grooves 12 recessed from the first surface 10A and extending in a predetermined direction. The protective film 30 is engaged with the plurality of grooves 12. This creates an anchor effect in the protective film 30 with respect to the resistor 10, thereby improving the bond between the resistor 10 and the protective film 30.

[0064] The protective film 30 contains filler 31 made of a material containing ceramics. This increases the mechanical strength of the protective film 30. Furthermore, by selecting a ceramic with a relatively high thermal conductivity, such as alumina or boron nitride, as the ceramic, the thermal conductivity of the protective film 30 can be increased. This further improves the heat dissipation of the resistor A10.

[0065] The insulating plate 20 is made of a material containing synthetic resin. This allows the substrate 82 to be thermocompression bonded to the second surface 81B of the resistor 81 by lamination pressing in the process shown in FIG. 11 . Furthermore, a portion of the insulating plate 20 penetrates the first slit 111 and the second slit 112 in the thickness direction z. This creates an anchor effect of the insulating plate 20 with respect to the resistor 10, thereby improving the bonding between the resistor 10 and the insulating plate 20. Furthermore, each of the first slit 111 and the second slit 112 has a pair of side walls 11A spaced apart in the first direction x. Each of the pair of side walls 11A has a portion that is concave in the first direction x. This enhances the anchor effect of the insulating plate 20 with respect to the resistor 10, thereby further improving the bonding between the resistor 10 and the insulating plate 20.

[0066] The insulating plate 20 has a pair of end surfaces 20A that face opposite each other in the first direction x and are spaced apart from each other in the first direction x. Each of the side portions 52 of the pair of electrodes 50 contacts one of the pair of end surfaces 20A. This allows the dimension of each of the side portions 52 of the pair of electrodes 50 in the thickness direction z to be longer. When the resistor A10 is mounted on a wiring board, a solder fillet is formed on each of the side portions 52 of the pair of electrodes 50. Therefore, this configuration further increases the volume of the solder fillet, thereby further improving the mountability of the resistor A10 on a wiring board.

[0067] The resistor A10 further includes a pair of intermediate layers 40 that have a covering portion 41 that covers a portion of the protective film 30 and are spaced apart from each other in the first direction x. The pair of intermediate layers 40 are electrically connected to the resistive element 10. In the resistor A10, the pair of intermediate layers 40 are made of thin metal films. Each of the covering portions 41 of the pair of intermediate layers 40 is located between the protective film 30 and one of the bottom portions 51 of the pair of electrodes 50. This allows the bottom portions 51 of the pair of electrodes 50 that cover a portion of the protective film 30 to be formed by electrolytic barrel plating in the process shown in FIG. 16 .

[0068] The first outer edge 30A and the second outer edge 30B of the protective film 30 are located between the pair of first end faces 10C of the resistor 10 when viewed along the thickness direction z. The first face 10A of the resistor 10 has a first region 131 and a second region 132 that are not covered by either the protective film 30 or the pair of intermediate layers 40. Each of the first region 131 and the second region 132 contacts one of the bottoms 51 of the pair of electrodes 50. This allows current flowing through the resistor 10 to easily flow from the first region 131 and the second region 132 to the bottoms 51 of the pair of electrodes 50 during use of the resistor A10. This shortens the length of the current path in the resistor A10, thereby suppressing fluctuations in the resistance value of the resistor A10.

[0069] The resistor 10 has a protrusion 14 protruding in the second direction y from one of the pair of second end faces 10D. The protrusion 14 is connected to one of the pair of first end faces 10C. This allows the cutting line CL to be set using the protrusion 14 as a target in the process shown in FIG. 15 . The protrusion 14 also enlarges the area of ​​either the first region 131 or the second region 132 of the resistor 10. This improves the bond between the resistor 10 and one of the bottom portions 51 of the pair of electrodes 50. When the pair of electrodes 50 are formed by electrolytic barrel plating in the process shown in FIG. 16 , this improved bond makes it less likely that defects will occur in one of the bottom portions 51 of the pair of electrodes 50.

[0070] The shape of the resistor A10 is point-symmetric when viewed along the thickness direction z. This ensures that the resistance value of the resistor A10 is constant regardless of the polarity of the pair of electrodes 50. Therefore, when mounting the resistor A10 on a wiring board, it is not necessary to check the polarity of the pair of electrodes 50.

[0071] In the resistor A10, the pair of intermediate layers 40 are made of a material containing a synthetic resin containing metal particles. This allows the protective film 30 and the pair of intermediate layers 40 to be made of the same material, improving the bond between the protective film 30 and the covering portions 41 of the pair of intermediate layers 40. Furthermore, the pair of intermediate layers 40 have conductive physical properties, allowing the pair of intermediate layers 40 to be electrically connected to the resistor 10.

[0072] In the resistor A10, the electrical resistivity of the pair of intermediate layers 40 is greater than the electrical resistivity of the resistor 10. As a result, when the resistor A20 is in use, the current flowing through the resistor 10 is less likely to flow through the pair of intermediate layers 40. Therefore, fluctuations in the resistance value of the resistor A20 due to the influence of the pair of intermediate layers 40 can be suppressed.

[0073] A resistor A20 according to the second embodiment will be described with reference to Figs. 19 to 22. In these figures, elements that are the same as or similar to those of the resistor A10 described above are given the same reference numerals, and duplicated explanations will be omitted. Note that Fig. 19 shows a perspective view of the insulating plate 20. Fig. 20 shows a perspective view of the pair of electrodes 50. In Fig. 20, the perspective view of the pair of electrodes 50 is indicated by imaginary lines.

[0074] In the resistor A20, the configuration of the pair of intermediate layers 40 differs from that of the resistor A10 described above.

[0075] In the resistor A20, the pair of intermediate layers 40 are made of a metal thin film. The metal thin film is made of, for example, a nickel-chromium (Cr) alloy. As shown in FIGS. 19, 20, and 22, each of the pair of intermediate layers 40 has a coating portion 41 and an extension portion 42. The coating portion 41 is located on the opposite side of the protective film 30 from the resistor 10 in the thickness direction z. The coating portion 41 covers a portion of the protective film 30. The extension portion 42 extends from one of the coating portions 41 of the pair of intermediate layers 40 toward one of the pair of first end faces 10C of the resistor 10. The extension portion 42 is in contact with the first surface 10A of the resistor 10. This provides electrical continuity between the pair of intermediate layers 40 and the resistor 10. Note that in the resistor A20, each of the pair of intermediate layers 40 does not include the first layer 40A or the second layer 40B. This allows each of the pair of intermediate layers 40 to be integrated.

[0076] Next, an example of a method for manufacturing the resistor A20 will be described with reference to Figures 12, 16, 17, and 23 to 25. The cross-sectional positions shown in Figures 23 to 25 are the same as the cross-sectional position shown in Figure 22.

[0077] 12, a base material 82 is thermocompression bonded to a resistor element 81 having a first surface 81A and a second surface 81B facing opposite sides in the thickness direction z. Note that this step is the same as the step in the method for manufacturing the resistor A10, and therefore a description thereof will be omitted.

[0078] 23, a protective film 30 is formed to cover a part of the first surface 81A of the resistor 81 and a part of the base material 82 that penetrates into the plurality of slits 811 of the resistor 81. The protective film 30 is formed by applying a material containing epoxy resin by screen printing to a part of the first surface 81A so as to completely cover the part of the base material 82 that penetrates into the plurality of slits 811, and then thermally curing the material.

[0079] Next, as shown in FIG. 24 , a metal thin film 83 is formed so as to overlap the entire first surface 81A of the resistor 81 and the entire protective film 30 when viewed along the thickness direction z. To form the metal thin film 83, first, a mask layer 89 is formed so as to cover part of the first surface 81A of the resistor 81 and part of the protective film 30. The mask layer 89 is formed by screen printing. After the mask layer 89 is formed, the metal thin film 83 is formed. The metal thin film 83 is made of a nickel-chromium alloy. The metal thin film 83 is formed by a sputtering method. In this process, the entire mask layer 89 is covered with the metal thin film 83.

[0080] 25, the mask layer 89 and a portion of the thin metal film 83 covering the mask layer 89 are removed (lifted off). This step forms a pair of intermediate layers 40 that cover a portion of the first surface 81A of the resistor 81 and a portion of the protective film 30. That is, the pair of intermediate layers 40 are made of the thin metal film 83 that remains on the protective film 30, etc.

[0081] 16, the resistor 81 and the substrate 82 are cut along cutting lines CL with a dicing blade to separate them into individual pieces each including the protective film 30 and a pair of intermediate layers 40. Note that this step is the same as the step in the method for manufacturing the resistor A10, and therefore a description thereof will be omitted.

[0082] Finally, a pair of electrodes 50 are formed in contact with the resistor 10, as shown in Fig. 17. This step is the same as the step in the method for manufacturing the resistor A10, and therefore a description thereof will be omitted. By going through the above steps, the resistor A20 is manufactured.

[0083] Next, the function and effect of the resistor A20 will be described.

[0084] The resistor A20 includes a resistive element 10, a protective film 30 disposed on a first surface 10A of the resistive element 10, and a pair of electrodes 50 spaced apart in the first direction x and in contact with the resistive element 10. The resistive element 10 has a first slit 111 and a second slit 112. The protective film 30 has a first outer edge 30A located closest to the first slit 111 and a second outer edge 30B located closest to the second slit 112. In the resistor A10, when viewed along the thickness direction z, a first distance L1 between the first outer edge 30A and the first slit 111 and a second distance L2 between the second outer edge 30B and the second slit 112 are both 15% or more of the dimension L0 of the protective film 30 in the first direction x. Therefore, the resistor A20 also makes it possible to suppress an increase in the temperature coefficient of resistance.

[0085] The present disclosure is not limited to the above-described embodiments, and the specific configurations of the components of these embodiments can be freely modified in various ways. [Explanation of symbols]

[0086] A10,A20:Resistor 10: Resistor 10A: First side 10B: 2nd side 10C: 1st end surface 10D: 2nd end surface 111: First slit 112: Second slit 11A: Side wall 12: Groove 131:First area 132:Second area 14: Protrusion 20: Insulating plate 20A: End face 30:Protective film 30A: First outer edge 30B: Second outer edge 31: Filler 40: Middle class 40A: 1st layer 40B: 2nd layer 41: Covering part 42: Stretching part 421: Notch 43: Interposition part 50: Electrode 51: Bottom 52: Side 81: Resistor 81A: Side 1 81B: 2nd side 811: Slit 812: Groove 82: Base material 83: Metal thin film 89: Mask layer L1, L1min, L1max: First interval L2, L2min, L2max: Second interval L0: Dimensions C: Center N: Boundary Bmin, bmax: width CL: Cutting line z: thickness direction x: 1st direction y: Second direction

Claims

1. a resistor having a first surface and a second surface facing opposite to each other in a thickness direction; a protective film disposed on the first surface, the protective film having electrical insulation properties and made of a material containing a synthetic resin; a pair of electrodes arranged apart from each other in a first direction perpendicular to the thickness direction and in contact with the resistor; the protective film has a first outer edge and a second outer edge that are spaced apart from each other in the first direction and extend in a second direction perpendicular to both the thickness direction and the first direction; the resistor has a first slit and a second slit penetrating from the first surface to the second surface and extending in the second direction; the first slit is located closest to the first outer edge, the second slit is located closest to the second outer edge, When viewed in the thickness direction, a first interval between the first outer edge and the first slit and a second interval between the second outer edge and the second slit each have a length that is 15% or more of a dimension of the protective film in the first direction, each of the pair of electrodes has a bottom portion located on an opposite side of the protective film to the resistor in the thickness direction; the bottom portion of each of the pair of electrodes includes a portion overlapping a portion of the protective film when viewed in the thickness direction, When viewed in the thickness direction, a distance between the bottom portions of the pair of electrodes is smaller than each of the first distance and the second distance; the resistor has a pair of first end faces connected to both the first surface and the second surface and spaced apart from each other in the first direction; Each of the pair of electrodes has a side portion that is individually connected to the bottom portion of the pair of electrodes and stands up in the thickness direction, the side portions of each of the pair of electrodes are in contact with the pair of first end surfaces, an insulating plate disposed on the second surface and made of a material including a synthetic resin; the resistor has a pair of second end faces connected to both the first surface and the second surface and spaced apart from each other in the second direction; the pair of second end surfaces are covered with the insulating plate, each of the first slit and the second slit has a first opening that opens from the first surface and a second opening that opens from the second surface and is connected to the first opening; a dimension of each of the first slit and the second slit in the first direction is smallest at a boundary between the first opening and the second opening, The second opening bulges out toward both sides in the first direction, the insulating plate recesses into each of the first slit and the second slit and is in contact with the protective film.

2. The resistor according to claim 1 , wherein the first interval and the second interval are equal to each other when viewed in the thickness direction.

3. 3. The resistor according to claim 1, wherein the protective film is made of a material containing a synthetic resin.

4. 4. The resistor according to claim 3, wherein the protective film contains a filler made of a material including ceramics.

5. When viewed in the thickness direction, the first slit overlaps with the bottom portion of one of the pair of electrodes, The resistor according to claim 1 , wherein the second slit overlaps with the bottom portion of the other of the pair of electrodes when viewed in the thickness direction.

6. The resistor according to claim 5 , wherein, as viewed in the thickness direction, each of the first interval and the second interval has a length that is 30% or less of a dimension of the protective film in the first direction.

7. A resistor as described in any one of claims 1 to 6, wherein the side portions of each of the pair of electrodes are in contact with the insulating plate.

8. The first slit extends in the second direction from one of the pair of second end faces, The resistor according to claim 1 , wherein the second slit extends in the second direction from the other of the pair of second end faces.

9. The resistor has a protrusion protruding from one of the pair of second end faces in the second direction, the protrusion is connected to one of the pair of first end surfaces, 9. The resistor according to claim 1, wherein one of said bottom portions of each of said pair of electrodes is in contact with said projection.

10. The resistor has a plurality of grooves recessed from the first surface and extending in a predetermined direction, 10. The resistor of claim 1, wherein the protective film is in engagement with the plurality of grooves.

11. The semiconductor device further includes a pair of intermediate layers located between the resistor and the bottom portions of the pair of electrodes in the thickness direction, each of the pair of intermediate layers has a covering portion that covers a part of the protective film; 11. The resistor according to claim 1, wherein the bottom portions of the pair of electrodes are individually in contact with the covering portions of the pair of intermediate layers.

12. When viewed in the thickness direction, the first outer edge and the second outer edge are located between the pair of first end faces, the first surface includes a first region and a second region exposed from the protective film and each of the pair of intermediate layers; the first region is located between the first outer edge and one of the pair of first end faces that is closest to the first outer edge, the second region is located between the second outer edge and one of the pair of first end faces that is closest to the second outer edge, The resistor of claim 11 , wherein each of the first region and the second region individually contacts the bottom portion of each of the pair of electrodes.

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