Multilayer resistor, and manufacturing method for multilayer resistor

Abstract

To prevent solder wetting on a resistor formed of a high specific resistance material, that can be used in the applications for large current detection.SOLUTION: A multilayer resistor includes a resistor having a plate shape and including a first flat surface and a second flat surface in a thickness direction, and a first electrode formed on the first flat surface and a second electrode formed on the second flat surface. The resistor includes a metal body formed of an electroconductive metal material, and an insulating particle formed of an insulating material. The insulating particle includes a first insulating particle with a particle diameter of 5 μm or more. At the implementation on a printed board, an end surface of the resistor is exposed and the second electrode is connected through the solder.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a stacked resistor for sensing current and a method for making the same. [Background technology]

[0002] Patent Document 1 discloses a resistor having a disk-shaped resistive element having a first plane and a second plane in the thickness direction, a first electrode formed on the first plane, and a second electrode formed on the second plane. This resistor is a vertical resistor in which current flows vertically.

[0003] The above-mentioned vertical resistor uses a resistor made of a resistive material having a structure in which a three-dimensional mesh-like metal body surrounds insulating particles, thereby achieving a high specific resistance that is suitable for use in detecting large currents while maintaining a low height. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-035851 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the resistive material disclosed in Patent Document 1, the resistor and the electrodes form a plate-shaped laminated structure. The resistor and the electrodes are each formed thin. Therefore, when the resistor and one of the electrodes are mounted on a printed circuit board using solder, the solder is likely to wet and rise to the end faces of the electrodes and the resistor.

[0006] If the solder that has wetted up one electrode and the end face of the resistor reaches the other electrode, a short circuit may occur, resulting in a defective product.

[0007] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to prevent solder from wetting onto a resistor made of a high resistivity material that is applicable to large current detection applications while having a low profile. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a multilayer resistor having a plate-shaped resistive element having a first plane and a second plane in the thickness direction, a first electrode formed on the first plane, and a second electrode formed on the second plane, wherein the resistive element is composed of a metal body made of a conductive metal material and insulating particles made of an insulating material, the insulating particles including first insulating particles having a particle size of 5 μm or more, and the multilayer resistor is configured such that, when mounted on a printed circuit board, an end face of the resistive element is exposed and the second electrode is connected to the printed circuit board via solder. Effect of the Invention

[0009] According to one embodiment of the present invention, it is possible to prevent solder from wetting onto a resistor made of a high resistivity material that is applicable to large current detection applications while having a low profile. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing the structure of the multilayer resistor according to this embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the multilayer resistor taken along line II-II in FIG. [Diagram 3] FIG. 3 is an enlarged schematic diagram illustrating a cross section near the boundary between the resistor and the first electrode. [Figure 4] FIG. 4 is an enlarged schematic diagram illustrating a cross section of the resistor near its end face (region S shown in FIG. 2). [Diagram 5] FIG. 5 is a schematic diagram illustrating a circuit board as an example of mounting a resistor. [Figure 6] FIG. 6 is a schematic diagram illustrating a resistor mounted on a circuit board. [Figure 7]FIG. 7 is a perspective view illustrating a resistor as a first modified example of this embodiment. [Figure 8] FIG. 8 is a perspective view illustrating a resistor as a second modified example of this embodiment. [Figure 9] FIG. 9 is an explanatory diagram illustrating a plating apparatus for forming a strike plating layer, a base electrode layer, a first electrode, and a second electrode on a resistance material by plating. [Figure 10] FIG. 10 is a schematic diagram illustrating a resistor mounted on a circuit board as a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Multilayer resistors] The structure of the multilayer resistor 1 of this embodiment will be described with reference to the drawings.

[0012] The resistor 1 is a resistor for detecting a current, and is called a current detection resistor or a shunt resistor. The resistor 1 is mounted in, for example, a power module, and used for detecting a large current.

[0013] FIG. 1 is a perspective view showing the structure of a multilayer resistor 1 (hereinafter, referred to as resistor 1) according to this embodiment, and FIG. 2 is a cross-sectional view of resistor 1 taken along line II-II in FIG.

[0014] In this embodiment, the resistor 1 is formed in a plate shape and includes a resistive element 11 made of a resistive material, a first electrode 21, and a second electrode 22.

[0015] The resistor 11 has a first plane 11A and a second plane 11B in the thickness direction. A first electrode 21 is formed on the first plane 11A. Also, a second electrode 22 is formed on the second plane 11B.

[0016] That is, the resistor 1 has a laminated structure in which a first electrode 21, a resistive body 11, and a second electrode 22 are laminated in this order.

[0017] In the resistor 1 according to this embodiment, a current path is formed in the thickness direction D shown in Figures 1 and 2. Therefore, the current path is shorter than the current path of a general shunt resistor. In the resistor 1, the thickness h of the resistor 11 is formed to be thin in order to realize miniaturization (particularly, low height).

[0018] The resistivity (volume resistance) of resistor 11 in this embodiment needs to be set to a value greater than the resistivity of an alloy alone used as a resistive material in a typical shunt resistor, which is about 50 μΩ·cm to 100 μΩ·cm.

[0019] <Electrode> The first electrode 21 and the second electrode 22 are electrodes for passing a current in the thickness direction of the resistor 11, and are formed using a metal material having high conductivity. In this embodiment, the first electrode 21 and the second electrode 22 can generally be formed using a metal material capable of forming an electrode. As an example of such a metal material, it is preferable to use copper (Cu).

[0020] In this embodiment, in order to form a thin electrode with low resistivity, it is effective to form the electrode by a plating method. The plating method can obtain a resistance value equivalent to that of a single metal, so-called bulk metal, and can form the electrode itself thinner than a method in which a bulk metal body is bonded to a resistor body by welding or the like.

[0021] In this embodiment, as an example, copper is used as the metal material from the viewpoints of good electrical conductivity and reducing the height of the resistor 1, and the thickness T1 of the first electrode 21 and the thickness T2 of the second electrode 22 can both be formed to 30 μm to 150 μm by copper plating.

[0022] In particular, in this embodiment, the thickness T2 of the second electrode 22 connected to the printed circuit board 101 (FIG. 5) can be designed to be thinner than the thickness T1 of the first electrode 21 located above the resistor 11.

[0023] In other words, since the thickness T2 of the second electrode 22 connected to the printed circuit board 101 (Figure 5) can be made thin, the thickness T1 of the first electrode 21 located above the resistive element 11 can be made thick without changing the height of the resistor as a whole.

[0024] <Resistor> In this embodiment, the resistive material 11a constituting the resistor 11 and realizing high resistivity is a resistive material 11a having a structure in which metal bodies are connected in a three-dimensional mesh shape around unmelted insulating particles.

[0025] The resistive material 11a in this embodiment is characterized in that it has a larger resistivity than the resistors of general shunt resistors because a current path is formed by three-dimensional mesh-like metal bodies formed between insulating particles.

[0026] Furthermore, the resistive material 11a in this embodiment has the advantage that, by using insulating particles with a large particle size, a three-dimensional mesh structure having a thin and long current path due to the metal body is easily formed between the insulating particles.

[0027] In this specification, the "grain size" refers to a value determined from a cross-sectional SEM image of the resistor 11 (resistance material 11a).

[0028] In this embodiment, the thickness h of the resistor 11 is required to be set to, for example, several mm (millimeters) or less so as to reduce the self-inductance value of the resistor 1. From the viewpoint of reducing the height, the thickness h of the resistor 11 is, for example, 0.2 mm.

[0029] In this embodiment, in order to facilitate mounting on a wiring pattern or a power semiconductor, the length R of one side of the resistor 11 can be set to be larger than the thickness h of the resistor 11. The length R of one side of the resistor 11 is required to be several mm. From the viewpoint of miniaturization, the length R of one side of the resistor 11 can be, for example, 3 to 6 mm. Note that FIG. 1 shows the structure of the resistor 1 having a quadrangular shape as an example. The planar shape of the resistor 1 can be a rectangle, a square, a polygon, a circle, or the like.

[0030] Furthermore, resistive material 11a constituting resistor 11 is required to be a resistive material that can be designed to have a resistivity within the range of 200 μΩ·cm (microohm centimeters) to 300,000 μΩ·cm.

[0031] In this embodiment, the resistivity of resistor 11 is preferably set within a range of 200 μΩ·cm to 1500 μΩ·cm, so that even if the inter-electrode distance is designed to be short in response to a design requirement to reduce the height of the product, the resistance value required for resistor 1 as a large current detection resistor can be achieved.

[0032] Fig. 3 is an enlarged schematic diagram illustrating a cross section near the boundary between resistor 11 and first electrode 21. Fig. 4 is an enlarged schematic diagram illustrating a cross section near the end face of resistor 11 (region S shown in Fig. 2).

[0033] The resistive material 11a constituting the resistor 11 contains metal bodies and insulating particles, which will be described below.

[0034] (metal body) A typical resistive material for a shunt resistor can be used as the metal body applicable to the resistive material 11a. From the viewpoint of ensuring the stability of the resistive characteristics, it is preferable to use a metal material suitable for detecting a large current, for example, an alloy in which the rate of change in the resistance value of the resistive material 11 due to the temperature change is small.

[0035] Specific examples include at least one alloy selected from resistance materials such as nichrome, Manganin (registered trademark), Zeranin (registered trademark), and copper-nickel. In particular, it is preferable to use nichrome from the viewpoint of ensuring the resistance value of the resistance material. Also, it is preferable to use Manganin (registered trademark) from the viewpoint of processability.

[0036] In this manner, depending on the resistance value of the resistive material and the workability, the metal body of the resistive material 11a can be formed using at least one selected from the group consisting of nichrome, copper manganese, and copper nickel.

[0037] Nichrome is a Ni-Cr based alloy or an alloy containing it as the main component, copper manganese is a Cu-Mn based alloy or an alloy containing it as the main component, and copper nickel is a Cu-Ni based alloy or an alloy containing it as the main component. Manganin (registered trademark) is a Cu-Mn-Ni based alloy or an alloy containing it as the main component, and Zeranin (registered trademark) is a Cu-Mn-Sn based alloy or an alloy containing it as the main component.

[0038] From the viewpoint of forming a good three-dimensional mesh structure, it is preferable to use particles having an aspect ratio of 1.0 to 2.0 as the metal powder before sintering when forming the resistance material 11a, and it is preferable for the metal body to be particles having a particle size of 0.5 μm to 20 μm.

[0039] The ratio of the metal bodies contained in the resistance material 11a is 30 vol% or more and 80 vol% or less. If the ratio of the metal bodies is less than 30 vol%, the resistance material 11a cannot secure a sufficient current path and does not function as a resistance material. On the other hand, if the ratio of the metal bodies exceeds 80 vol%, the resistivity of the resistance material 11a decreases to a value almost equal to the resistivity of the metal bodies alone.

[0040] (insulating particles) As insulating particles applicable to the resistance material 11a, ceramic materials having excellent heat resistance as well as insulating properties can be used. For example, from the viewpoint of suppressing the occurrence of cracks due to thermal stress, at least one ceramic material selected from the group consisting of aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), and zirconia (ZrO2) can be used. Hereinafter, aluminum oxide and aluminum nitride are referred to as alumina and aluminum nitride, respectively.

[0041] Among the above-mentioned ceramic materials, it is preferable to use alumina, which is widely used as an insulating material, from the viewpoint of heat dissipation and heat cycle durability. In addition, in applications requiring higher heat dissipation, it is preferable to select aluminum nitride, which has high thermal conductivity, and in applications requiring high heat cycle durability, it is preferable to select silicon nitride.

[0042] In order to form a good current path in the three-dimensional mesh structure of the metal body formed between the insulating particles, the insulating particles are preferably mainly approximately spherical. The insulating particles may contain ellipsoidal insulating particles within a range that does not impede the formation of the current path. The insulating particles may also contain a predetermined proportion of flaky particles.

[0043] In this embodiment, the insulating particles include first insulating particles having a particle size of 5 μm or more. The insulating particles may also include second insulating particles having a particle size of less than 5 μm. When the second insulating particles are included, they are preferably mixed such that the sum of the cross sections of the first insulating particles in the cross section of resistor 11 is greater than the sum of the cross sections of the second insulating particles.

[0044] In this embodiment, the insulating particles preferably have an average particle size of 10 μm or less. In this specification, the term "average particle size" refers to the number average particle size per unit cross section obtained from a cross-sectional SEM image as described above.

[0045] The average particle size of the insulating particles is more preferably 2 μm to 9 μm. If the average particle size is less than 2 μm, the number of first insulating particles having a particle size of 5 μm or more will be relatively small, so that the density of the sintered body formed of the insulating particles and the metal body will decrease, resulting in unstable resistance characteristics.

[0046] Furthermore, when the average particle size exceeds 9 μm, the number of first insulating particles having a particle size of 5 μm or more increases, making it difficult for a three-dimensional mesh structure of the metal body to be formed between the insulating particles, resulting in unstable resistance characteristics. When high precision in the resistance characteristics is not required, the average particle size of the insulating particles can be set to a range exceeding 9 μm, but even in this case, it is preferable to set it to 15 μm or less.

[0047] From the above viewpoints, the average particle size of the insulating particles is set to the above range. Furthermore, by setting the average particle size of the insulating particles to the above range, the average particle size of the insulating particles is reflected in the surface roughness of the resistive material 11a, and an uneven surface with a surface roughness Ra of 2 μm to 9 μm, expressed by the arithmetic mean roughness, is obtained on the resistive material 11a.

[0048] In this embodiment, from the viewpoint of forming a good current path through the metal body in the resistor 11, the amounts of the metal body, the first insulating particles and the second insulating particles are set so that the ratio of the sum of the areas of the first insulating particles having a particle size of 5 μm or more to the total cross-sectional area of ​​the resistor 11 is 15% or more and 50% or less.

[0049] If the proportion of the total area of ​​the first insulating particles in the cross-sectional area of ​​resistor 11 is 50% or more, resistor 11 will not be able to secure a sufficient current path of a three-dimensional mesh structure, and will no longer function as a resistive material.

[0050] On the other hand, if the proportion of the total area of ​​the first insulating particles in the cross-sectional area of ​​resistor 11 is less than 15%, the resistivity of resistive material 11a decreases to a value almost equal to the resistivity of the metal body alone.

[0051] In this embodiment, in a resistive material formed from a mixed insulating particle, in which first insulating particles having a particle size of 5 μm or more and second insulating particles having a particle size of less than 5 μm are mixed such that the average particle size of the insulating particles is 10 μm or less and there are more first insulating particles than second insulating particles, and a metal body, the area ratio of the insulating particles to the metal body in the cross section of the resistor can be treated as being approximately equal to the volume ratio of the insulating particles to the metal body in the mixture of the insulating particles and the metal body.

[0052] In other words, when the mixing ratio of the metal body and the insulating particles is metal body:insulating particles=50:50, the ratio of the sum of the areas of the metal bodies to the sum of the areas of the insulating particles in the entire cross-sectional area of ​​resistor 11 will also be approximately the same.

[0053] [Effects of multilayer resistors] In the resistor 1 according to this embodiment, the end faces of the first electrode 21 and the second electrode 22 are smoother than the end faces of the resistive body 11. For this reason, the end faces of the first electrode 21 and the second electrode 22 are more easily wetted by solder.

[0054] 4, the resistive material 11a constituting the resistor 11 is in a state in which insulating particles are scattered and surrounded by a matrix of metal bodies. Therefore, protrusions corresponding to the particle size of the insulating particles are formed on the end faces of the resistor 11. The metal bodies constituting the resistive material 11a are exposed to the air and tend to become inactive.

[0055] For these reasons, by including the first insulating particles having a particle size of 5 μm or more as the insulating particles, it is possible to obtain an effect of suppressing the wetting up of solder by the protrusions of the insulating particles on the end faces of resistor 11. In this case, it is preferable that the average particle size of the insulating particles is 10 μm or less (surface roughness Ra=5 to 9 μm).

[0056] Furthermore, by using an alloy that is insulating and difficult to be wetted by solder as the insulating particles, the effect of preventing solder wetting can be further improved.

[0057] [Manufacturing method of multilayer resistors] Next, a method for manufacturing the resistor 1 will be described below. The method for manufacturing the resistor 1 includes a method for manufacturing a resistive material and a method for manufacturing a resistor using the obtained resistive material.

[0058] <Method of manufacturing resistor material> A method for producing the resistive material 11a in this embodiment will be described.

[0059] The manufacturing method of the resistive material 11a includes a mixing step of mixing a conductive metal powder (metal powder) and an insulating powder (insulator powder) having insulating properties, and a sintering step of sintering the mixed powder obtained by mixing while applying pressure by a uniaxial pressing method at a predetermined temperature.

[0060] In this embodiment, the insulating powder is a mixture of first insulating particles having an average particle size of 10 μm or less, and second insulating particles having a particle size of less than 5 μm, and the first insulating particles are mixed in greater amounts than the second insulating particles.

[0061] The metal powder used is a powder of a metal having a melting point lower than that of the insulating powder. The metal powder is preferably granulated so that the particle size of the metal powder is equal to or smaller than that of the insulating powder.

[0062] In the mixing process, the metal powder is weighed out so that the proportion of the metal powder is 30 vol% or more and 80 vol% or less by total volume, and the insulating powder is weighed out so that the proportion of the insulating powder is the remainder. The two powders are then mixed uniformly and granulated.

[0063] In the sintering process, for example, the container for the mixed powder is evacuated and the mixed powder is pressurized. The higher the pressing pressure, the easier it is to ensure a current path in the resulting resistor material 11a. For this reason, it is preferable to set the pressing pressure to be high.

[0064] Moreover, the firing temperature for sintering is lower than the melting point of the metal powder, and is preferably set to a temperature approximately 15% lower than the melting point of the metal powder.

[0065] In the manufacturing method of the resistive material 11a described above, the mixed powder of insulating powder and metal powder is heated to a predetermined temperature lower than the melting point of the metal powder, and sintered under pressure. This allows the resistive material 11a to be obtained in which the metal bodies formed between the insulating particles are formed in a three-dimensional mesh shape. The resistive material 11a having such a structure can achieve high resistivity.

[0066] Next, the sintered body (bulk body) of the resistance material obtained by the above process is sliced ​​to a predetermined thickness to obtain the resistance material 11a.

[0067] In the slicing step, a wire saw is preferably used. In the slicing process using a wire saw, a roller around which the wire is wound is rotated to run the wire, and the wire is applied to the sintered body while a slurry containing an abrasive is interposed, to cut out thin plate-shaped pieces of the resistance material.

[0068] When the sintered body is cut by the wire, the metal bodies contained in the resistance material are cut by the wire saw, while some of the insulating particles are ejected from the cut surface by the wire and removed, while others remain on the cut surface.

[0069] Therefore, on the cut surface, insulating particles surrounded by metal bodies in a matrix are scattered, and irregularities corresponding to the particle size of the insulating particles are formed.

[0070] Metal layers that become the first electrode 21 and the second electrode 22 are formed on the surface of the thin-plate resistive material piece by plating. That is, in the thin-plate resistive material piece, the first electrode 21 is formed on the surface that becomes the first plane 11A, and the second electrode 22 is formed on the surface that becomes the second plane 11B.

[0071] The obtained plate-like laminated structure can be diced, for example, using a dicing blade to separate it into chip-like pieces of a predetermined size. By using a dicing blade, it is possible to separate it into pieces while leaving unevenness due to insulating particles on the end faces. The resistor 1 can be manufactured by the above process.

[0072] [Example of mounting on a circuit board] Fig. 5 is a schematic diagram illustrating an example of a circuit board 100 on which a resistor 1 is mounted. Fig. 6 is a schematic diagram illustrating an enlarged view of a main portion of the resistor 1 on the circuit board 100.

[0073] The circuit board 100 shown in FIG. 5 is, for example, a power module that processes high voltage and large current, and the resistor 1 functions as a current detection resistor that detects large current.

[0074] The circuit board 100 is a printed circuit board 101 made of an insulating material. Current wiring 111 and 112 that constitute a circuit are formed on the printed circuit board 101. In addition, current detection wiring 113 and 114 connected to an IC for current detection are also formed.

[0075] 6, the resistor 1 is mounted by soldering at a predetermined location of the current wiring 111. An example of soldering the resistor 1 will be described.

[0076] First, the solder paste 30 is printed at a predetermined location on the current wiring 111. Thereafter, with the second electrode 22 of the resistor 1 mounted on the solder paste 30 of the current wiring 111, the solder paste 30 is melted and solidified under predetermined mounting conditions.

[0077] As a result, a solder fillet 31 is formed between the second electrode 22 and the current wiring 111 , and the resistor 1 is mounted on the printed circuit board 101 .

[0078] The first electrode 21 of the resistor 1 is connected to the other current wiring 112 by a lead wire 121 .

[0079] The first electrode 21 of the resistor 1 is connected to a current detection wiring 113 by a bonding wire 131. The current detection wiring 111 to which the second electrode 22 of the resistor 1 is connected is connected to a current detection wiring 114 by a bonding wire 132.

[0080] In the circuit board 100 as described above, the resistor 1 can detect a large current flowing through the circuit.

[0081] [Effects of mounting multilayer resistors on circuit boards] As described above, in the resistor 1 according to this embodiment, the solder fillet 31 creeps up the end face of the second electrode 22 but does not reach the end face of the resistive element 11.

[0082] This is because the insulating particles contained in the resistive material 11a are exposed at the end face of the resistor 11 and a protrusion is formed by the insulating particles. Therefore, even if there is variation in the amount of solder paste applied or the dimensions of the connection portion in the current wiring 111, the creeping up of the solder fillet can be suppressed.

[0083] This makes it possible to prevent the solder fillet from creeping up to the end face of the first electrode 21 formed on the upper side of the resistor element 11. This makes it possible to prevent the resistor 1 from being short-circuited.

[0084] In addition, in a multilayer resistor in which electrodes are formed on the surface of the resistor by plating, such as the resistor 1 of this embodiment, when the electrodes and the current detection wiring are connected by wire bonding, the electrodes may not be sufficiently durable against wire bonding due to their thinness.

[0085] In addition, the thin electrodes result in a large potential distribution in the electrodes. Therefore, even if the wire bonding connection position is misaligned to an extent that the error is small, it can affect the current detection accuracy. However, if the electrodes are made thick to meet the durability requirements during wire bonding, the height of the resistor 1 increases, which hinders the reduction in height.

[0086] In contrast, in the resistor 1 of this embodiment, the solder does not wet up the resistive element 11, so the thickness of the second electrode 22, which is on the printed circuit board 101 side and connected to the current wiring 111 by solder, can be made thinner.

[0087] Therefore, the thickness of the first electrode 21 can be increased without changing the overall height of the resistor 1. Furthermore, since the thickness of the first electrode 21 can be increased, the potential distribution inside the first electrode 21 can be alleviated, and durability in wire bonding can be improved.

[0088] In the resistor 1 according to this embodiment, as an example, the thickness T2 of the second electrode 22 on the printed circuit board 101 side can be set to 30 μm, and the thickness T1 of the upper first electrode 21 can be set to 170 μm. This ensures current detection accuracy equivalent to that when electrodes each having a thickness of 100 μm are used, and improves the durability of the wire bonding of the upper first electrode 21.

[0089] The insulating particles constituting the resistive material 11a include second insulating particles having a particle size of less than 5 μm, and the ratio of the total cross section of the first insulating particles to the cross section of the resistor 11 is 15% or more and 50% or less. Such a resistive material 11a provides a good current path.

[0090] In the resistor 1, the first insulating particles are more numerous than the second insulating particles. In other words, since there are many first insulating particles with a particle size of 5 μm or more, a three-dimensional mesh structure of thin and long metal bodies is easily formed between the first insulating particles. Therefore, the resistance characteristics can be stabilized.

[0091] The metal bodies in the resistive material 11a are formed in a three-dimensional mesh shape so as to surround the insulating particles, which makes it easier to form thin and long current paths inside the resistive material 11a, and therefore makes it easier to stabilize the resistance characteristics.

[0092] Furthermore, the current path of the three-dimensional mesh structure is less likely to be broken due to temperature changes or application of high voltage, and the influence on the resistivity of the entire resistance material 11a is suppressed. Therefore, the resistivity of the resistance material 11a can be made larger than the resistivity of the metal body alone, and the resistance characteristics of the resistance material 11a can be stabilized.

[0093] According to the present embodiment, the conductive metal body of the resistance material 11a is formed using at least one metal powder selected from the group consisting of nichrome, copper manganese, and copper nickel. These metal powders are alloys used for current detection, and the change in resistance value due to temperature change is small. Therefore, by using these alloys, it is easy to ensure the resistance value required for current detection and the increase in TCR can be suppressed.

[0094] Furthermore, according to this embodiment, the insulating particles are formed using at least one insulating powder selected from the group consisting of alumina, aluminum nitride, silicon nitride, and zirconia. These insulating powders are ceramic materials, have a low thermal expansion coefficient, and are used as substrate materials. By using these insulating powders, the thermal stress of the resistor 11 made of the resistance material 11a can be made closer to the thermal stress of the substrate. Therefore, the occurrence of cracks due to heat cycles between the resistor 11 and the substrate can be suppressed.

[0095] In addition, according to the present embodiment, the metal body of the resistance material 11a is formed into a three-dimensional mesh structure, so that the TCR can be stabilized and kept within the allowable range of 100 ppm or less. Therefore, it is possible to suppress the deterioration of detection accuracy when detecting a current using the resistor 1.

[0096] Furthermore, it is possible to design the resistivity of the resistive material 11a to be within the range of 200 μΩ·cm to 30,000 μΩ·cm, inclusive, which makes it possible to ensure a resistance value required for detecting a large current, even in the case of a so-called vertical resistor 1 having a short current path as shown in FIG.

[0097] In addition, according to the present embodiment, a conductive metal is used in powder form, and the metal powder is mixed with insulating particles and granulated. This makes it easy to interpose the metal body in the gaps between the insulating particles, and when sintered, it becomes easy to form a three-dimensional mesh-like metal body in the resistance material 11a.

[0098] Furthermore, according to this embodiment, many current paths are formed in the resistor 11 while avoiding the insulating particles. Therefore, the resistivity of the resistor 11 can be increased and the resistance characteristics of the resistor 11 can be stabilized.

[0099] [Modification of resistor] <Variation 1> FIG. 7 is a perspective view illustrating a resistor 2 as a first modified example of this embodiment.

[0100] In the resistor 2 according to this embodiment, the solder does not wet up the resistive element 11, so the thickness of the second electrode 22 on the printed circuit board 101 side and connected to the current wiring 111 by solder can be made thin. This allows the thickness of the first electrode 310 to be made thick. This increases the degree of freedom in designing the resistor.

[0101] In the first modified example, by making the first electrode 310 thicker, a structure can be realized in which the first electrode 310 is divided into a first portion 311 and a second portion 312 by a slit 313 formed along the longitudinal direction of the resistor 2.

[0102] 7, when the resistor 2 has an electrode shape as shown in FIG. 7, the first portion 311 of the first electrode 310 can be connected to the current detection wiring by wire bonding when the resistor 2 is mounted on a circuit board. Since the first portion 311 is separated from the second portion 312, the current measurement portion can be set at a position away from the main flow of the current flowing through the resistor 11. This improves the accuracy of current detection.

[0103] <Variation 2> FIG. 8 is a perspective view illustrating a resistor 3 as a second modified example of this embodiment.

[0104] In the resistor 3 shown as the second modified example, the first electrode 410 is thickened so that the first electrode 410 is divided into a first portion 411 and a second portion 412 by an L-shaped slit 413.

[0105] According to the resistor 3, when mounted on a circuit board, the first portion 411 of the first electrode 410 can be connected to the current detection wiring by wire bonding. This allows the current measurement portion to be set at a position away from the main flow of the current flowing through the resistor 11. This improves the accuracy of current detection.

[0106] [Other embodiments] Although the present embodiment has been described above, the above embodiment merely shows one application example of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configuration of the above embodiment.

[0107] The resistor 1 in this embodiment may be in the shape of a plate, and may be in the shape of a disk, a square corner, or a rectangular corner.

[0108] For example, in the above embodiment, the first electrode 21 and the second electrode 22 of the resistor 1 are shown to have the same area and size, but the first electrode 21 and the second electrode 22 may be formed to have either the area or the size different from each other. Also, the first electrode 21 and the second electrode 22 may have a through hole.

[0109] In addition, the method for forming the first electrode 21 and the second electrode 22 on both sides of the resistor 11 may be a vacuum deposition method, an ion plating method, a sputtering method, a vapor phase growth method, a cold spray method, or the like, in addition to a plating method.

[0110] In the resistive material 11a according to this embodiment, as the particle size of the insulating particles increases, a current path with a thin and long three-dimensional mesh structure can be formed. However, as the particle size of the insulating particles increases, the effect of unevenness caused by the insulating particles appearing on the surface of the resistive material 11a also increases, so that the adhesion between the first electrode 21 and the resistor 11 and the adhesion between the second electrode 22 and the resistor 11 tend to decrease. In such a case, the resistor 11 (first plane 11A) may be provided with a base electrode layer. Similarly, the second plane 11B of the resistor 11 may be provided with a base electrode layer.

[0111] The base electrode layer can be made of a material having a high affinity with the insulating particles. Examples of materials that can be used for the base electrode layer include nickel (Ni) and nickel-chromium alloys, which have a high affinity with the insulating particles.

[0112] Furthermore, a strike plating layer may be formed between the base electrode layer and the resistor 11. Nickel, titanium, silver, etc. may be used as a material for forming the strike plating layer.

[0113] Forming the base electrode layer and the strike plating layer can enhance the metallic activity of the metal body on the surface of the resistor 11. This can enhance the adhesion of the base electrode layer, and can prevent the base electrode layer from swelling or peeling after plating. EXAMPLES

[0114] A test specimen based on the resistor 1 according to the embodiment of the present invention was fabricated, and various measurements were performed to evaluate the resistor 1. A method for fabricating the test specimen and its evaluation will be described below.

[0115] [Making resistors] <Mixing / granulation> (insulating powder) As insulating particles applied to the resistance material 11a, the alumina powder contained first insulating particles having a particle size of 5 μm or more and second insulating particles having a particle size of less than 5 μm, and had an average particle size of 8 μm. Mixed insulating particles were prepared by mixing first insulating particles having a particle size of 5 μm or more and second insulating particles having a particle size of less than 5 μm so that the ratio of the total area of ​​the first insulating particles having a particle size of 5 μm or more to the total cross-sectional area at any position of the obtained resistor 11 was 15% or more and 50% or less. (metal body) Nichrome powder [powder having an average particle size of 4 μm produced by atomizing Evanome (registered trademark)] was used as the metal powder for producing the metal body of the resistance material 11a.

[0116] The mixed insulating particles and metal powder were mixed in a volume ratio of metal body:insulating particles=50:50, and mixed and granulated until both were uniformly mixed.

[0117] <Pressing and sintering> Next, the granulated mixed powder was placed in a carbon die with a diameter of 50 mm. Then, using a hot press machine (multipurpose high-temperature furnace Hi-Multi 5000: manufactured by Fuji Denpa Kogyo Co., Ltd.), the mixed powder in the carbon die was heated (hot pressed) to a specified temperature lower than the melting point of nichrome, and in this state, the mixed powder was sintered while being pressurized. The obtained specimen of the resistance material was a cylindrical sintered body with a diameter of 50 mm and a thickness of 200 mm.

[0118] The hot pressing conditions in the pressure and sintering process were as follows: Atmosphere: 20 Pa or less Press pressure: 20MPa~50MPa Sintering temperature: 1000℃~1200℃ ·Holding time: 10 to 30 minutes

[0119] The cylindrical sintered body of the resistance material obtained by the above steps was sliced ​​to 0.2 mm using a wire saw to obtain the resistance material 11a.

[0120] [Resistor manufacturing] Next, a first electrode 21 and a second electrode 22 were formed on a first plane and a second plane of the resistor element 11 obtained by the slicing process.

[0121] FIG. 9 is an explanatory diagram illustrating a plating apparatus 200 for forming the first electrode 21 and the second electrode 22 on a resistance material by plating.

[0122] The plating apparatus 200 includes a plating bath 201 in which a plating solution is stored, an anode electrode 202, and a cathode electrode 203.

[0123] A plating solution for forming electrodes was used to form a first electrode 21 and a second electrode 22 on the surface of the resistor 11. After the electrodes were formed, a test piece of the chip-shaped resistor 1 having a size of 5 mm×5 mm square and a thickness of 0.4 mm was produced using a dicing blade.

[0124] <Example> An electrode having a thickness of 30 μm was formed on one surface of the resistor 11. Also, an electrode having a thickness of 170 μm was formed on the other surface. <Comparative Example> An electrode having a thickness of 30 μm was formed on one surface of the resistor of the comparative example, in the same manner as in the example, and an electrode having a thickness of 170 μm was formed on the other surface.

[0125] <Implementation conditions> For each of the obtained laminates of the example and comparative example, the surface on which the 30 μm-thick electrode was formed was connected with a predetermined copper pattern formed on a printed circuit board by reflowing the solder in a nitrogen atmosphere.

[0126] [Evaluation method] <Surface roughness of resistor> The surface roughness of the resistor was measured by a laser microscope for shape analysis.

[0127] <Solder wettability measurement results> The solder wetting property was visually confirmed by observing the mounted product from diagonally above using a magnifying glass.

[0128] [result] <Surface roughness of resistor> The surface roughness Ra of the resistor of the example was 8 μm, while the surface roughness Ra of the resistor of the comparative example was less than 2 μm.

[0129] <Solder wettability measurement results> FIG. 10 is a schematic diagram illustrating a resistor 4 mounted on a printed circuit board 101 as a comparative example.

[0130] 10, in the resistor 4 of the comparative example, a solder fillet 223 is formed between the second electrode 222 and the current wiring 111, and the resistor 4 is mounted on the printed circuit board 101. In the resistive element 211 of the resistor 4 of the comparative example, no protrusions made of insulating particles are formed on the end faces.

[0131] As a result, depending on the amount of solder paste applied and the dimensions of the connection portion of the current wiring 111, the solder fillet 223 may creep up to the end face of the resistor 211 and the end face of the first electrode 221, causing a short circuit between the first electrode 221 and the second electrode 222.

[0132] In contrast, it was found that the test pieces of the examples did not wet out the solder and provided good electrical properties.

[0133] Therefore, it was found that a resistor containing insulating particles having first insulating particles with a particle size of 5 μm or more has a surface roughness Ra of 5 μm or more on the end face of the resistor, the end face of the resistor is exposed even after soldering, and solder wetting does not occur. [Explanation of symbols]

[0134] 1 resistor 11 Resistor 11a resistance material 11A 1st plane 11B 2nd plane 21 1st electrode 22 2nd electrode 30 Solder fillet 100 Circuit Board 101 Printed Circuit Board 111,112 Current wiring 113,114 Current detection wiring 121 Lead Wire 131,132 Wire bonding 200 Plating equipment 201 Plating bath 202 Anode electrode 203 Cathode Electrode 221 1st electrode 222 2nd electrode 223 Solder fillet

Claims

1. A multilayer resistor having a plate-like resistor element having a first plane and a second plane in a thickness direction, a first electrode formed on the first plane, and a second electrode formed on the second plane, the resistor is composed of a metal body made of a conductive metal material and insulating particles made of an insulating material; The insulating particles include first insulating particles having a particle size of 5 μm or more, When mounting on a printed circuit board, An end surface of the resistor is exposed, and the second electrode is connected to the printed circuit board via solder. Multilayer resistor.

2. 2. The multilayer resistor according to claim 1, The second electrode connected to the printed circuit board has a thickness smaller than a thickness of the first electrode. Multilayer resistor.

3. 2. The multilayer resistor according to claim 1, The insulating particles include second insulating particles having a particle size of less than 5 μm; a ratio of the total cross section of the first insulating particles to the cross section of the resistor is 15% or more and 50% or less; Multilayer resistor.

4. 4. The multilayer resistor according to claim 3, a sum of the areas of the first insulating particles in a cross section of the resistor is greater than a sum of the areas of the second insulating particles; Multilayer resistor.

5. A method for manufacturing a multilayer resistor having a plate-like resistor element having a first plane and a second plane in a thickness direction, a first electrode formed on the first plane, and a second electrode formed on the second plane, comprising the steps of: the resistor having the first plane and the second plane is made of insulating particles including first insulating particles made of an insulating material and having a particle size of 5 μm or more, and a metal body made of a conductive metal material; forming the first electrode and the second electrode on the resistor by a plating method to form a laminate; The laminate is diced to obtain a chip resistor. A method for manufacturing multilayer resistors.

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