JP6149288B2 - Shunt resistor module - Google Patents

Description

  The present invention relates to a shunt resistor module, and more particularly to a heat dissipation structure of a shunt resistor module.

  A shunt resistor is used to detect the current in the circuit. For example, it is used for detection of disconnection or short circuit in a power module. Such a shunt resistor is formed by connecting a low-resistance resistor (shunt resistor) of, for example, 1 mΩ or less between a pair of terminals (electrodes). In a shunt resistor used for a power module, for example, a current of 100 A or more may flow. For this reason, even if it is a low resistance resistor, a shunt resistor becomes high temperature by Joule heat. When the shunt resistor becomes high temperature, it may affect current detection characteristics and the like, and may also affect the shunt resistor module including the shunt resistor, and appropriate cooling is necessary.

  A cooling structure of a conventional shunt resistor is shown in FIG. The shunt resistor 10 shown in FIG. 3 employs a hat-shaped member 11 as a shunt resistor. The internal space partitioned by the hat-shaped member 11 and the substrate 12 is filled with an epoxy resin 13 that is insulative and has good thermal conductivity. (For example, refer to Patent Document 1).

Utility Model Registration No. 3067213

  However, the shunt resistor disclosed in Patent Document 1 described above has a structure in which the inside of a hat-shaped member is filled with resin. The thermal conductivity of the resin is generally much inferior to that of metal, and is not necessarily sufficient for improving the heat dissipation characteristics of the shunt resistor. In addition, the resin filled in the hat-shaped member is likely to be deteriorated by heat, and there is a great concern that the heat radiation characteristics are deteriorated due to aging.

    The present invention has been made in view of the above problems, and an object of the present invention is to provide a shunt resistor module including a shunt resistor that improves heat dissipation characteristics and has little deterioration of heat dissipation characteristics due to changes over time.

In order to solve the above problems, some embodiments of the present invention provide the following shunt resistor module. That is, the shunt resistor module of the present invention is a shunt resistor module including at least a substrate having a wiring layer formed on one surface and a shunt resistor mounted on the substrate, and the shunt resistor is a shunt resistor. A resistor, and a pair of terminals that support the shunt resistor so as to be spaced apart from one surface of the substrate, and the one surface of the substrate is disposed between the pair of terminals, and the shunt A heat conductor made of metal that extends toward the resistor and has a front end surface that maintains a predetermined gap with respect to the shunt resistor, the front end surface being more than a junction between the terminal and the wiring layer; characterized in that forming the curved surface Oite at a position close to the shunt resistor, from both ends toward the central portion protrudes into the shunt resistor side.

  An insulator is disposed in the gap between the thermal conductor and the shunt resistor.

  A region partitioned by the thermal conductor, the shunt resistor, and the pair of terminals is filled with a resin.

  The outside of the shunt resistor is covered with resin.

  The front end surface of the heat conductor has a shape approximate to the planar shape of the shunt resistor.

  The thermal conductor is bonded to the substrate via a solder layer.

  According to the shunt resistor module of the present invention, the heat generated in the shunt resistor is quickly propagated toward the substrate from the front end surface of the heat conductor facing the one surface of the shunt resistor through a predetermined gap. The By forming a heat conductor with high thermal conductivity extending from the substrate toward the shunt resistor, the shunt resistor is generated in the shunt resistor as compared with the case where the entire interior of the shunt resistor is filled with resin. The Joule heat can be radiated efficiently. As a result, it is possible to realize a shunt resistor module that prevents the shunt resistor from becoming high temperature and prevents the current detection characteristics from deteriorating due to high temperature.

It is sectional drawing which shows an example of the shunt resistance module provided with the shunt resistor of this invention. It is sectional drawing which shows the example of a shape of a heat conductor. It is sectional drawing which shows the conventional shunt resistor.

  Hereinafter, an embodiment of a shunt resistor module according to the present invention will be described with reference to the drawings. The present embodiment is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

  FIG. 1 is a cross-sectional view showing an example of the shunt resistor module of the present invention. The shunt resistor module 20 includes at least a substrate 21 on which a wiring layer 22 having a predetermined pattern is disposed, and a shunt resistor 23. The shunt resistor 23 is a pair of shunt resistors 24 disposed at a predetermined interval with respect to the one surface 21 a of the substrate 21, and a pair of shunt resistors 24 that support the shunt resistor 24 while being separated from the one surface 21 a of the substrate 21. Terminals 25 and 26 are provided. On one surface 21 a of the substrate 21, a heat conductor 27 is formed that extends between the terminals 25 and 26 and extends toward the shunt resistor 24. Further, a heat sink 29 that dissipates heat generated from an electronic component including the shunt resistor 23 mounted on the substrate 21 is joined to the other surface 21b of the substrate 21. Note that an insulating layer 21 c made of an oxide film or the like of the substrate 21 is formed between the one surface 21 a side of the substrate 21 and the heat conductor 27.

  The shunt resistor 23 is disposed, for example, between the wiring layer 22a on the current inflow side and the wiring layer 22b on the outflow side. The shunt resistor 24 is, for example, a rectangular parallelepiped whose outer shape is formed of a low-resistance resistor having a resistance of 1 mΩ or less.

  The terminals 25 and 26 are entirely formed of a good conductor, for example, copper, silver, aluminum, and the like, and are composed of joint portions 25a and 26a and standing portions 25b and 26b, respectively. The joint portions 25a and 26a are arranged in parallel to the one surface 21a of the substrate 21, and are joined to the wiring layers 22a and 22b by, for example, solder.

  The standing portions 25 b and 26 b of the terminals 25 and 26 are formed integrally with the joint portions 25 a and 26 a at one end side, extend substantially perpendicular to the one surface 21 a of the substrate 21, and further extend horizontally toward the shunt resistor 24. The shunt resistor 24 is supported between the other end sides. Thereby, the flat shunt resistor 24 is supported in parallel with a predetermined interval with respect to the one surface 21 a of the substrate 21. By disposing the shunt resistor 24 in a three-dimensional manner away from the one surface 21a of the substrate 21, the mounting space for the shunt resistor 23 can be reduced.

  In addition, the junction parts 25a and 26a which comprise the terminals 25 and 26, and the standing parts 25b and 26b should just be integrally formed by the mutually same member. Moreover, although the joining parts 25a and 26a are extended in the direction which mutually approaches from the standing parts 25b and 26b, the shape extended in the direction which mutually separates from the standing parts 25b and 26b, what is called a hat shape may be sufficient.

  The heat conductor 27 is formed of, for example, a metal block whose outer shape is a rectangular parallelepiped. One surface 27 a of the heat conductor 27 is joined to one surface 21 a of the substrate 21 via a heat conductive material, for example, a solder layer 28, and the other surface (hereinafter referred to as a tip surface) 27 b is one surface of the shunt resistor 24. Facing 24a. The entire heat conductor 27 is formed of a material having excellent heat conductivity, such as copper, silver, aluminum, iron, nickel, or an alloy thereof. In particular, it is preferably formed from copper or a copper alloy having excellent thermal conductivity.

  A predetermined gap Δt is maintained between the front end surface 27 b of the heat conductor 27 and the one surface 24 a of the shunt resistor 24. This gap Δt is preferably set to a distance that maintains the insulation between the thermal conductor 27 and the shunt resistor 24 and efficiently absorbs the heat of the shunt resistor 24. For example, the gap Δt is the distance between the front end surface 27 b of the heat conductor 27 and the one surface 24 a of the shunt resistor 24.

  The front end surface 27b of the heat conductor 27 is formed to have a shape that approximates the planar shape of the shunt resistor 24, for example, a rectangle that is the same size as the one surface 24a of the shunt resistor 24 or that extends wider than that. It is preferable.

  A region partitioned by the thermal conductor 27, the shunt resistor 24, and the terminals 25, 26, that is, an internal space of the shunt resistor 24 having a substantially rectangular cross section is filled with resin, and the first resin body 31 is formed. Forming. The first resin body 31 is also formed between the front end surface 27b of the heat conductor 27 and the one surface 24a of the shunt resistor 24 facing each other with a predetermined gap Δt. Thereby, the insulation between the heat conductor 27 and the shunt resistor 24 is further improved. The first resin body 31 may not be interposed between the front end surface 27b of the heat conductor 27 and the one surface 24a of the shunt resistor 24, and an air layer may be used.

  The outside of the shunt resistor 24 is covered with resin to form a second resin body 32. The second resin body 32 may be the same member as the first resin body 31 filled in the internal space of the shunt resistor 24 or may be a different member. The first resin body 31 and the second resin body 32 only need to be formed from a resin material having excellent heat resistance and insulation.

  The operation of the shunt resistor module 20 configured as described above will be described. The shunt resistor 23 that constitutes the shunt resistor module 20 detects a current that flows between the wiring layer 22a and the wiring layer 22b that are bonded to the bonding portions 25a and 26a, respectively. At this time, when the current flowing through the shunt resistor 24 has a large current value such as 100 A or more, Joule heat is generated in the shunt resistor 24.

  The heat generated in the shunt resistor 24 is promptly directed from the front end surface 27b of the heat conductor 27 facing the one surface 24a of the shunt resistor 24 through a narrow gap Δt toward the one surface 27a of the heat conductor 27. Propagate. Then, heat is radiated from the heat sink 29 via the substrate 21. By forming the heat conductor 27 having a high thermal conductivity extending from the substrate 21 toward the shunt resistor 24, the entire interior of the shunt resistor is filled with a resin having a low thermal conductivity as in the prior art. In comparison, Joule heat generated in the shunt resistor 24 can be efficiently propagated toward the heat sink 29 to be dissipated. Thereby, the shunt resistor 24 whose outer surface is covered with the second resin body 32 can be prevented from becoming high temperature, and the shunt resistor module 20 can be realized in which current detection characteristics are prevented from deteriorating due to high temperature.

  In addition, by covering the entire outer surface of the shunt resistor 24 with the second resin body 32, heat generated in the shunt resistor 24 is diffused around the shunt resistor 24, and other electrons mounted on the substrate 21. It is possible to prevent the parts from being heated to a high temperature.

  FIG. 2 is a cross-sectional view showing a shape example of the heat conductor in the shunt resistor module of the present invention. In the following description, the same members as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. In the shunt resistor module 40 shown in FIG. 2A, the tip surface 47b of the heat conductor 47 formed on the substrate 21 via the solder layer 28 is formed by combining a plurality of inclined surfaces having a larger surface area than the flat surface. It is said. Thereby, the heat generated in the shunt resistor 24 can be more efficiently received from the one surface 24a of the shunt resistor 24 and propagated toward the heat sink 29, and the heat dissipation of the shunt resistor 24 can be further enhanced. It becomes possible. 2A is, for example, the distance between the one surface 24a of the shunt resistor 24 and the top where the inclined surfaces constituting the tip surface 47b of the heat conductor 47 intersect.

  In the shunt resistor module 50 shown in FIG. 2B, the front end surface 57b of the heat conductor 57 formed on the substrate 21 is a curved surface having a larger surface area than the flat surface. Thereby, the heat generated in the shunt resistor 24 can be more efficiently received from the one surface 24a of the shunt resistor 24 and propagated toward the heat sink 29, and the heat dissipation of the shunt resistor 24 can be further enhanced. It becomes possible. 2B is, for example, the distance between one surface 24a of the shunt resistor 24 and the top of the curved surface constituting the tip surface 57b of the heat conductor 57.

  In addition to the embodiments described above, for example, it is also preferable to form the heat conductor so that the front end face faces one side of the shunt resistor and both sides of the other side.

  20, 40, 50 ... shunt resistor module, 21 ... substrate, 22 ... wiring layer, 23 ... shunt resistor, 24 ... shunt resistor, 25, 26 ... terminal, 27, 47, 57 ... thermal conductor, 29 ... heat sink .

Claims (6)

A shunt resistor module comprising at least a substrate having a wiring layer formed on one surface and a shunt resistor mounted on the substrate,
The shunt resistor has a shunt resistor and a pair of terminals that support the shunt resistor with being spaced from one surface of the substrate.
A heat conductor made of metal that is disposed on one surface of the substrate between the pair of terminals, extends toward the shunt resistor, and maintains a predetermined gap with respect to the shunt resistor. With
The tip surface that forms a curved surface Oite at a position close to the shunt resistor than the junction, from both ends toward the central portion projecting to the shunt resistor side of the wiring layer and the terminal Features a shunt resistor module.   The shunt resistor module according to claim 1, wherein an insulator is disposed in the gap between the thermal conductor and the shunt resistor.   The shunt resistor module according to claim 1 or 2, wherein a region partitioned by the heat conductor, the shunt resistor, and the pair of terminals is filled with resin.   The shunt resistor module according to any one of claims 1 to 3, wherein an outer side of the shunt resistor is covered with a resin.   5. The shunt resistor module according to claim 1, wherein a front end surface of the heat conductor has a shape approximate to a planar shape of the shunt resistor. 6.   The shunt resistor module according to claim 1, wherein the thermal conductor is bonded to the substrate via a solder layer.

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