JP2017133928A - Shunt resistor, manufacturing method of the same, and current detector using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the reliability of a junction between a resistive element and an electrode, in a shunt resistor suitable for highly-accurate current detection and a current detector using the shunt resistor.SOLUTION: A shunt resistor includes: at least two first lands which are formed on a substrate, and which make current flow; and a wire-like resistive element which connects the first lands and which is made of a metal material for a resistive element.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shunt resistor and the like.

  Conventionally, a shunt resistor for detecting a circuit current has been manufactured by, for example, forming an electrode on a plate-like metal alloy and mounting it on a substrate by soldering. If it does in this way, the crack of the solder of a mounting part may generate | occur | produce by the repetitive stress by a heat cycle etc. In particular, when a shunt resistor whose base material is a plate-like metal alloy is mounted on a ceramic substrate, cracks are likely to occur in the solder mounting portion because the difference in linear expansion between the two is large.

  As a shunt resistor not using solder, Patent Document 1 describes a technique using an aluminum wire as a resistor.

Japanese Utility Model Publication No. 4-42705

  However, aluminum, which is the material of the aluminum wire shown in Patent Document 1, has a problem that it is not suitable for high-precision current detection, such as low resistivity and high temperature coefficient of resistance (TCR).

  An object of the present invention is to provide a shunt resistor suitable for high-precision current detection and a current detection device using the same, by improving the reliability of the junction between the resistor and the electrode.

  According to one aspect of the present invention, at least two first lands formed on a substrate and through which a current flows, and a wire-shaped resistor made of a metal material for a resistor that connects between the first lands, A shunt resistor is provided.

  It is preferable that a metal film made of a metal material different from the metal material is formed on a side surface of the wire-shaped resistor. The metal material different from the metal material is an electrode material having similar characteristics such as a thermal expansion coefficient with respect to the first land. This facilitates the connection of the wire-like resistor to the first land, and increases the reliability against changes with time.

  It is preferable that the conductor resistance of the metal film is 20 times or more than the conductor resistance of the wire-shaped resistor. In general, the resistivity of the metal film is low. However, if the thickness of the metal film is reduced and the conductor resistance is set to 20 times or more, the resistance value fluctuation of the resistor can be suppressed.

  The metal film may be formed intermittently along the wire-like resistor. For example, the influence of the conductor resistance of the metal film can be further reduced by performing the metal film only on the wire bonding scheduled region.

  The metal material for the resistor is preferably any one of a NiCr alloy, a CuNi alloy, a CuMn alloy, a CuTi alloy, a CuNiTi alloy, and a CuNiSi alloy. On the other hand, the metal film is preferably any one of Au, Ag, Ni, and Cu or an alloy containing these.

  The present invention is also a current detection device including the shunt resistor described above and a voltage detection terminal drawn from the first land.

  Here, at least two second lands different from the first lands are provided on the substrate, and the first lands and the second lands are wire-shaped as the voltage detection terminals. They can be connected by wiring.

  ADVANTAGE OF THE INVENTION According to this invention, the reliability of the junction part of a resistor and a land in a shunt resistor can be improved.

It is a figure which shows one structural example of the shunt resistor by the 1st Embodiment of this invention, Fig.1 (a) is sectional drawing, FIG.1 (b) is a top view which shows a wire bonding position, 1 (c) is a plan view of the shunt resistor. FIG. 2A is a flowchart showing an example of a manufacturing process of the shunt resistor according to the first embodiment of the present invention. FIG. 2B is a flowchart showing a manufacturing process example (main part) of the shunt resistor according to the second embodiment of the present invention. It is a perspective view which shows the example of 1 structure of the electric current detection apparatus using the shunt resistor technique by the 1st Embodiment of this invention. FIG. 4 is a diagram showing an example of a four-terminal current detection device that performs voltage extraction from an electrode using an Al wire instead of the wiring of FIG. FIG. 5A to FIG. 5C are perspective views showing modifications of the shunt resistor of this embodiment. It is a figure which shows the modification of the cross-sectional shape of a wire-shaped resistor. It is a figure which shows one structural example of the wire-shaped resistor used for the shunt resistor by the 2nd Embodiment of this invention. It is a figure which shows one structural example of the wire-shaped resistor used for the shunt resistor by the 3rd Embodiment of this invention. It is a figure which shows a mode that the wire-shaped resistor by the 3rd Embodiment of this invention is wire-bonded to an electrode. It is the 4th Embodiment of this invention, Comprising: It is a figure which shows an example of the application form of the wire shunt resistor using a wire-shaped resistor. FIG. 10A is a perspective view seen from the front surface side, and FIG. 10B is a perspective view seen from the back surface side.

  The inventor of the present invention studied that a metal material for a resistor (resistance alloy) is formed into a wire shape to form a resistor of a shunt resistor. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
1A and 1B are diagrams showing a configuration example of a shunt resistor according to a first embodiment of the present invention. FIG. 1A is a sectional view of the shunt resistor, and FIG. 1B is a wire bonding position. FIG. 1C is a plan view of the shunt resistor. FIG. 2A is a flowchart showing an example of the manufacturing process of the shunt resistor.

The shunt resistor shown in FIG. 1 (a) is formed by wire bonding or the like between a pair of electrodes (lands) 3, 5 made of Cu, Al, etc., formed on the substrate 1, and the electrodes 3, 5. And a wire-shaped resistor 7 made of a metal material for a resistor (resistance alloy or the like) suspended between the electrodes 3 and 5. The substrate 1 is a printed circuit board such as FR4, a ceramic substrate, a metal substrate, or the like, on which a wiring pattern including electrodes 3 and 5 is formed. As shown in FIG. 1 (c), both ends of the wire-like resistor 7, respectively, are connected to the electrodes 3 at the position P ₁ and the electrode 5 on the position P ₂ Metropolitan on the electrode 3. Both ends of the wire-like resistor 7 and the surfaces of the electrodes 3 and 5 can be connected (bonded) by pressure welding, ultrasonic waves, or the like to be electrically connected. As the resistance alloy, a nichrome alloy, a copper nickel alloy, a copper manganese alloy, a copper titanium alloy, a copper nickel silicon alloy, or the like can be used.

As shown in FIG. 1 (b), the connection position between the ends and the electrodes 3 of the wire-like resistor 7, for example, by changing the P ₁₂ to P _12x, the length of the wire-like resistor 7 The resistance value of the resistor can be adjusted by adjusting the length in the arrangement direction of the electrodes 3 and 5.

  As shown in FIG. 2A, the manufacturing process is started (step S1: Start), and the substrate 1 is prepared in step S2. In step S <b> 3, electrodes 3 and 5 are formed on the substrate 1. In step S4, for example, by using a wire bonding technique, the electrodes 3 and 5 are connected by the wire-like resistor 7 to complete the shunt resistor (End: step S5).

  Wire bonding can be performed, for example, by applying a known wedge bonding apparatus. For example, the tip of the wedge of the wedge bonding apparatus is ultrasonically vibrated, and a bonding wire is pressed against an object (electrode) to be bonded to be bonded by at least one of an ultrasonic wave and a load. A wedge bonding device usually uses a rotating table (which aligns the direction of wire tension and the direction of ultrasonic vibration) and an XY table (bonding head or sample that moves the tool up and down and moves the wire). Composed. You may perform wire bonding using another well-known apparatus.

  FIG. 3 is a perspective view showing a configuration example of a four-terminal current detection device using the shunt resistor technique described above. As shown in FIG. 3, on the substrate 1, in addition to the configuration shown in FIG. 1, connection pads 3a and 5a connected to the electrodes 3 and 5 by wirings are provided. In the connection pads 3a and 5a, the current between the electrodes 3 and 5 via the wire-like resistor 7 can be detected by, for example, probe measurement.

  Thus, the wire-like resistor 7 is wire-bonded to the electrodes 3 and 5 to form a shunt resistor. Then, by extracting voltage from the electrodes 3a and 5a by wiring, a four-terminal current detection device can be formed.

  In addition, as shown in FIG. 4, instead of wiring, voltage extraction is performed to the electrodes 3a and 5a by using Al wires 11a and 11b, thereby realizing a four-terminal current detection device using a shunt resistor. Also good.

  In the structure of FIG. 4, the wire-like resistor 7 and the Al wires 11 a and 11 b are made of different materials, but the wires 11 a and 11 b may be made of the same material as the wire-like resistor 7. . In that case, the distance between the electrodes 3 and 5 and the connection pads 3a and 5a, that is, the wire length is shortened, the wire thickness is increased, or a wire whose resistance is reduced by a metal plating film described later is used. You may do it. 3 and 4, the electrodes 3 and 5 are formed on the substrate for bonding, but the electrodes 3 and 5 may be formed on other components for bonding.

  At this time, it is preferable to use electrodes as thick as possible (for example, a copper foil having a thickness of 200 μm) as the electrodes 3 and 5 for bonding so that the potential difference becomes uniform.

  As described above, according to the embodiment of the present invention, it is possible to provide a shunt resistor that does not use solder mounting and a current detection device that uses the shunt resistor.

  FIG. 5 is a perspective view showing a modification of the shunt resistor of the present embodiment. Various desired resistance values can be obtained by using the material, thickness, and number of the wire-shaped resistors 7 as variables. Further, the resistance value of the shunt resistor can be finely adjusted by changing the position where the wire-like resistor 7 is connected to the electrodes 3 and 5 or changing the height.

FIG. 5A shows an example in which the resistance is reduced by forming a plurality of wire-like resistors 7 in parallel. FIG. 5 (b) finely adjusts the length of the wire by finely adjusting the position of wire bonding by shifting in the direction orthogonal to the arrangement direction of the electrodes 3, 5 like P ₂ and P ₃ . It is a figure which shows the example which changes resistance value. FIG. 5C shows an example in which the resistance value is adjusted by adjusting the thickness of the wire-like resistor 7. In the figure, the wire-like resistor 7 is exemplarily thinned to reduce its diameter. It is a figure which shows the example which performed high resistance by. In addition, the length of the wire between the bonding positions may be adjusted by changing the height of the suspended wire.

  FIG. 6 is a diagram illustrating an example of changing the cross-sectional shape of the wire-shaped resistor. In a shunt resistor, it is often necessary to reduce the resistance value of the resistor and pass a large amount of current. With a wire-like shunt resistor, there is a possibility of fusing by a large current. Therefore, it is preferable to reduce the current density (increase the cross-sectional area) even with the same diameter so that no problem occurs even when a large current is applied.

  For example, the cross-sectional shape can be changed as necessary. Various cross-sectional shapes can be produced by a processing method (profile processing) in which the resistance material is drawn through a die called a die.

  6A, the cross section 7c of the wire-like resistor 7 is circular, and in FIG. 6B, the cross-section 7d of the wire-like resistor 7 is rectangular. If the diameter is the same, more current can flow in the rectangular cross section than in the circular cross section.

  Thus, by selecting the wire-shaped resistor 7 having a different cross section, the resistance value of the shunt resistor can be changed or the current density can be adjusted. The cross section of the resistance wire can be processed into a cross-sectional shape such as a round shape, a square shape, a hexagonal shape or more, if necessary (selected according to the allowable current amount).

  As described above, according to the present embodiment, the reliability of the junction between the resistor and the electrode in the shunt resistor suitable for highly accurate current detection can be increased. There is an advantage that it is easy to cope with various resistance values by devising the shape of the wire, the position of wire bonding, etc. in the process of wire bonding to the electrode.

  Unlike ordinary shunt resistors, wire-shaped alloy shunt resistors are not used by soldering, but are connected by direct bonding, which causes the conventional problem of cracks in the solder joints. Can be resolved.

  Accordingly, a highly reliable resistor or an electronic component including the resistor can be provided. In particular, even a shunt resistor having a large difference in linear expansion from a metal alloy and used in an aluminum substrate or a ceramic substrate has an effect of improving the connection reliability.

(Second Embodiment)
In the second embodiment of the present invention, an example is shown in which processing is performed on the surface of the wire-shaped resistor (side surface of the wire). In general, the resistor material is difficult to bond. Therefore, the following measures were taken to ensure mountability.

  In the present embodiment, as shown in FIG. 7, the wire-like resistor 7 is formed so that wire bonding (connection to the electrode) can be easily performed on the metal electrodes (3, 5) such as Cu and Al to be connected. A metal film made of an electrode material having characteristics such as a thermal expansion coefficient close to that of the electrodes (3, 5) to be connected to the side surface (surface) in the extending direction of, for example, is plated to form a plating film (plating film) 21 Forming. Hereinafter, although the case where the plating film 21 is used as a metal film is demonstrated as an example, the formation method is not limited to plating. As a forming method, electrolytic plating, electroless plating, sputtering, vapor deposition, electrodeposition, or the like can be used.

  As the plating film 21, for example, an easy bonding material such as Au, Ag, Ni, or Cu can be plated. An alloy containing these may be used, and Ni-P or the like may be used. The film thickness is preferably 0.1 μm or less.

  As shown in FIG. 2B, which is an example of the plating process, processing is started (Step S11: Start), and a wire-like resistor (resistance material wire) 7 is prepared in Step S12. In step S13, a plating film 21 made of Au or the like is applied to the surface of the wire-like resistor 7, and the process proceeds to step S4 in FIG. 1A (step S14, end).

  When the plating film 21 is formed, the thickness of the plating film 21 is reduced so that the resistance of the material is 10 times higher than the resistance of the resistance material (resistance alloy) constituting the wire-like resistor 7. It is preferable to adjust so that.

  By making the specific resistance of the coating portion of the resistance material due to the plating film 21 so as to be high, fluctuations in the resistance value due to the plating film 21 can be suppressed. The thickness of the plating film 21 is preferably 0.1 μm or less, for example.

Below, the examination result about the film thickness of plating is shown. Table 1 shows the specific resistivity ρ of the plating material and the value of TCR, and Table 2 shows Cu-Mn-Ni-based materials such as manganin (CuMn ₁₂ Ni) and Cu-Mn as examples of resistance materials. The specific resistance ρ of the Sn system, for example, the trade name zeranin (CuMn ₇ Sn), and the TCR value are shown.

  Table 3 shows the calculated values of the thickness of the coating (plating film) 21, the conductor resistance magnification, the combined resistivity, and the combined TCR when a metal coating is formed on the manganin wire (0.1 mmφ) that is a resistor. It is a table | surface which shows. Calculation is made for the case where the coating (plating film) 21 is Cu, Ni, Au, or Ag. The conductor resistance magnification indicates how many times the resistance value of the coating film (plating film) 21 is with respect to the core material (resistor). The synthetic conductor resistance indicates a resistance value of a wire composed of a core material (resistor) and a coating (plating film) 21. The composite TCR is the TCR of the wire.

  From Table 3, in the area indicated by hatching, that is, in the thickness area of the coating (plating film) 21 in which the conductor resistance magnification is 20 or more, the composite TCR suitable for use in current detection is excellent with a synthetic TCR of 200 ppm / ° C. or less. It can be seen that the correct value is obtained.

  Table 4 shows values obtained by calculating the conductor resistance magnification, the combined resistivity, and the combined TCR when Cu, Ni, Au, and Ag are plated on the surface of the geranin wire 7 (0.1 mmφ) that is a resistor. From Table 4, in the area indicated by hatching, that is, in the thickness area of the coating (plating film) 21 where the conductor resistance magnification is 20 or more, the composite TCR suitable for use in current detection is plated with a synthetic TCR of 200 ppm / ° C. or less. It is possible to obtain a plated wire resistance material having a good value with suppressed influence.

  As shown in Table 1, since the resistivity of the metal material of the plating film 21 is lower than the resistivity of the metal material of the resistor 7, in order to fully utilize the characteristics of the resistor, the resistance It is preferable that the plating film 21 having a low rate value has a small thickness. As shown in Table 1, Ni having a high resistivity can be used as a resistor for a highly accurate current detection device even if it has a certain thickness.

  Tables 5 and 6 are tables showing the diameter dependence of the manganin wire 7 when Cu plating is applied to the surface of the manganin wire 7. Table 5 is a table showing values of TCR and the like when 0.5 mmφ and Table 6 are 1.0 mmφ. From these tables, it is understood that when the Cu plating is applied to the surface of the manganin wire 7, the conductor resistance of the metal film is preferably 20 times or more than the conductor resistance of the wire-like resistor. If the resistance ratio of the thin metal film to the resistance of the wire-shaped resistor (conductor resistance ratio) is 20 times or more (in the case of 0.5 mmφ, the plating thickness is 0.2 μm or less. In the case of 1.0 mmφ) Thickness of 0.4 μm or less), and a synthetic TCR value of 200 ppm / ° C. or less is obtained, so that the influence of the metal film (plating material) on the resistance value and the TCR value can be suppressed. Further, when temperature characteristics are required, the conductor resistance magnification is 40 times or more, and a plating thickness of 0.1 μm or less, or 0.2 μm or less, at which the synthetic TCR is obtained at about 100 ppm / ° C. or less is suitable.

  It can also be seen that the thicker the plated film 21, the better the synthetic TCR value is 200 ppm / ° C. or less as the diameter of the wire-like resistor 7 is larger. In addition, the thinner the plating film 21 is, the better the value is obtained in terms of characteristics. However, if the thickness is too thin, the effect of facilitating wire bonding is difficult to obtain, so a certain thickness is required. For example, if the plating thickness is 0.005 μm or more, an effect that wire bonding is easy can be obtained.

  According to the present embodiment, it is possible to facilitate wire bonding by forming the metal film on the surface of the wire-shaped resistor. Moreover, environmental resistance characteristics can be improved.

  Note that the plating region on the surface of the wire-shaped resistor does not necessarily have to be a region around the entire surface of the wire-shaped resistor, and may be, for example, a half-circle region or a quarter-circle region. . For example, after the plating process is performed over the entire circumference, the plating film in the half circumference area may be removed.

(Third embodiment)
In the example in which the third embodiment of the present invention performs processing on the surface of the wire-shaped resistor (surface along the wire) in the second embodiment, among the linear resistors, for example, This is an example in which a low resistivity metal film is formed only in a region for connecting to an electrode by wire bonding.

  FIG. 8 is a side view showing a configuration example of a wire-shaped resistor according to the present embodiment. As shown in FIG. 8, for example, the plating film 21 is formed by performing plating only on a region where wire bonding is to be performed on the surface of the wire-like resistor 7. In other areas, the surface of the resistance material is exposed. This plating film 21 can also be used as a mark when determining a region to be connected to the electrode before wire bonding.

  FIG. 8 shows an example in which the plating film 21 is formed intermittently. It is preferable that the area for applying the plating film 21 to be connected to the electrode is widened with a certain margin. The positions where the plating film 21 is formed need not necessarily be at equal intervals. For example, you may make it adjust according to the position of the electrode which performs wire bonding. It is possible to adjust the resistance value by adjusting the length of the resistor by adjusting the distance between the electrodes and the plating film forming position.

  FIG. 9 is a diagram illustrating a state in which the wire-shaped resistor according to the present embodiment is wire-bonded to the electrode. As shown in FIG. 9, the tip 31 of the wedge tool of the wedge bonding apparatus is brought into contact with the electrode 5 on the substrate 1, and the region covered with the plating film 21 is adhered to the electrode 5. The position where the plating film 21 is formed may be determined in advance in consideration of the distance between the electrodes 3 and 5, or wire bonding so that the plating film 21 can be bonded to the electrode 3 at the position where the plating film 21 is formed. May be performed. The plating area may be formed longer with a margin.

  As described above, the conductor combined resistance and the composite TCR studied in the second embodiment are plated by performing metal plating only on the region where wire bonding is performed among the linear resistors. The influence of the film can be further reduced. Accordingly, the plating film 21 can be thickened to improve the connectivity with the electrodes 3 and 5.

  The area where the surface plating is formed is not necessarily performed only on the area where the plating process is to be performed on the surface of the wire-like resistor, but in the area other than the area where the plating process is scheduled after the plating process is performed over the entire circumference. The plating may be removed.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
FIG. 10 is a diagram showing an example of an application form of a shunt resistor using a wire-shaped resistor according to the fourth embodiment of the present invention. FIG. 10 is a diagram illustrating an example of use of the large current detection device, in which FIG. 10A is a perspective view illustrating an example of a front surface structure, and FIG.

  As shown in FIG. 10, the large current detection device according to the present embodiment includes, for example, an inorganic high heat conductive base material (such as a ceramic substrate) 1 of about 10 mm square and a pair of electrodes formed on the high heat conductive base material 1. And a resistor having at least one wire-like resistor 7 (three in the figure) formed between the current terminals 3 and 5. Furthermore, the large current detection device according to the present embodiment includes voltage detection terminals 3a and 5a formed on the high thermal conductive substrate 1, an amplifier 61 for amplifying a voltage signal, and a voltage connected to the output of the amplifier 61. And a signal terminal 51. The voltage signal terminal 51 includes a power supply voltage supply terminal 51a (Vcc), a signal output terminal 51b (Vout), and a ground terminal 51c (GND).

  Note that the current terminals 3 and 5 and the voltage signal terminal 51 are preferably configured as a block-like terminal formed from the front surface of the substrate 1 to the back surface of the substrate 1 so as to be able to handle a large current.

  Thus, according to the present embodiment, a large current detection device suitable for integration can be provided at low cost.

  Further, the difference in linear expansion can be absorbed by forming the shunt of the shunt resistor by the wire bonding process. Reliability is increased by forming the shunt by wire bonding instead of soldering. The resistance value can be finely adjusted by adjusting the length of the wire during wire bonding.

  As described above, when fabricating a shunt resistor by bonding a resistance wire to the electrode portion, bonding may be performed to the electrode prepared in the component shape, or bonding may be performed directly to the land pattern of the substrate to be used. You can go. At this time, it is preferable to use an electrode (for example, a 200 μm copper foil) as thick as possible so that the potential difference becomes uniform.

A four-terminal shunt resistor can be realized by directly performing voltage extraction bonding with a wire made of aluminum or the like from an electrode to which a resistor is bonded.
The present invention also includes a manufacturing method for manufacturing a shunt resistor or the like.

  In the above-described embodiment, the configuration and the like illustrated in the accompanying drawings are not limited to these, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  Each component of the present invention can be arbitrarily selected, and an invention having a selected configuration is also included in the present invention.

  The present invention is applicable to resistors.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 3, 5 ... Electrode (1st land), 3a, 5a ... Four terminal structure electrode (connection pad: 2nd land), 7 ... Wire-shaped resistor, 21 ... Plating film (plating) Film).

Claims (8)

At least two first lands formed on the substrate and carrying a current;
A shunt resistor having a wire-like resistor made of a metal material for a resistor connecting the first lands.   The shunt resistor according to claim 1, wherein a metal film made of a metal material different from the resistor is formed on the wire-shaped resistor.   The shunt resistor according to claim 2, wherein the conductor resistance of the metal film is 20 times or more than the conductor resistance of the wire-shaped resistor.   The shunt resistor according to claim 2 or 3, wherein the metal film is formed intermittently along the wire-shaped resistor.   The metal material for the resistor is any one of a NiCr alloy, a CuNi alloy, a CuMn alloy, a CuTi alloy, a CuNiTi alloy, and a CuNiSi alloy. Shunt resistor as described in.   The shunt resistor according to any one of claims 2 to 4, wherein the metal film is any one of Au, Ag, Ni, and Cu or an alloy containing these. A shunt resistor according to any one of claims 1 to 6,
A current detection device comprising: a voltage detection terminal drawn from the first land. On the substrate, provided with at least two second lands different from the first lands,
The current detection device according to claim 7, wherein the first land and the second land are connected by a wire-like wiring as the voltage detection terminal.

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