JP2018018960A - Shunt resistor - Google Patents

Abstract

An object of the present invention is to provide a shunt resistor capable of stabilizing the resistance value. A shunt resistor according to the present invention includes a resistor 11 made of metal and a pair of electrodes 12a and 12b connected to both ends of the resistor 11. The pair of electrodes 12a and 12b are respectively terminal portions 13a and 13b for attaching the mounting substrate 20 provided below the resistor 11 and extending in the direction in which the resistor 11 is positioned; A pair of electrodes 12a and 12b are formed on a part of the lower part of the side surface 15 of the pair of legs 14a and 14b located in the direction away from the resistor 11. A first metal layer 16 having better solder wettability and a covering layer 17 having poorer solder wettability than the first metal layer 16 and provided in a portion where the first metal layer 16 is not formed are provided. [Selection drawing] Fig. 1

Description

  The present invention relates to a shunt resistor having a high resistance and a low resistance value of 1Ω or less used for detecting a current value of various electronic devices.

  As shown in FIG. 5, this type of conventional shunt resistor includes a resistor 1 made of a plate-like metal and a pair of electrodes 2 formed on both ends of one surface of the resistor 1. Each of the pair of electrodes 2 has leg portions 3 that are bent downward from the resistor 1, and a mounting solder layer is formed on the pair of leg portions 3 to be mounted on the mounting substrate. I was trying to do it.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

Japanese Patent Laid-Open No. 2004-22658

  In the above conventional shunt resistor, the position of the solder layer for mounting formed on the pair of leg portions 3 cannot be specified, so the location where the solder layer for mounting is formed is not stable, and thus the resistance value is not stable. It had the problem that.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a shunt resistor capable of stabilizing the resistance value.

  In order to achieve the above object, the present invention stands a pair of electrodes with respect to a mounting board mounting terminal portion extending in a direction of a resistor provided below the resistor and the mounting board. And a first metal layer formed on a part of the lower portion of the side surface of the pair of leg portions, the solder metal being better in wettability than the pair of electrodes. And a coating layer that is provided at a location where no solder is formed and has poorer solder wettability than the first metal layer.

  As described above, the shunt resistor of the present invention is formed on a part of the lower portion of the pair of legs standing up with respect to the mounting substrate in the direction away from the resistor, and is wetted by the solder from the pair of electrodes. The first metal layer is formed in a place where the first metal layer is not formed, and the coating layer having poorer solder wettability than the first metal layer is provided. By doing so, it is possible to stabilize the location where the mounting solder layer is formed, and thereby to produce an excellent effect that the resistance value can be stabilized.

The side view of the shunt resistor in one embodiment of the present invention Side view showing the mounted state of the shunt resistor Side view of another example of the shunt resistor Side view of another example of the shunt resistor Side view of a conventional shunt resistor

  FIG. 1 is a side view of a shunt resistor according to an embodiment of the present invention, and FIG. 2 is a view showing a state in which the shunt resistor is mounted on a mounting substrate.

  As shown in FIGS. 1 and 2, the shunt resistor according to one embodiment of the present invention includes a resistor 11 made of metal, and a pair of electrodes 12 a and 12 b connected to both ends of the resistor 11. The pair of electrodes 12 a and 12 b are provided below the resistor 11 and extend in the direction in which the resistor 11 is positioned, and the mounting substrate 20 mounting terminal portions 13 a and 13 b are attached to the mounting substrate 20. Leg portions 14a and 14b that stand and connect the resistor 11 and the terminal portions 13a and 13b are provided.

  Further, the side surface 15 of the pair of leg portions 14a and 14b located in the direction away from the resistor 11 has a first metal layer 16 formed on a part of the lower portion thereof and having better solder wettability than the pair of electrodes 12a and 12b. A coating layer 17 is formed at a location where the first metal layer 16 is not formed and has poorer solder wettability than the first metal layer 16.

  In the above configuration, the resistor 11 is made of a plate-like or foil-like metal such as copper nickel, manganin, nickel chrome, or the like. The resistor 11 may be provided with one or a plurality of trimming grooves (not shown) by punching or the like, thereby adjusting the resistance value. Further, a protective film (not shown) for protecting the resistor 11 may be formed around the resistor 11.

  Further, the pair of electrodes 12 a and 12 b is formed of a metal plate separate from the resistor 11, and is made of a metal such as copper having a conductivity lower than that of the resistor 11. The pair of electrodes 12a and 12b are connected to both ends of the resistor 11, and the resistor 11 and the pair of electrodes 12a and 12b are brought into contact with each other in a state of abutting each other, and laser welding or brazing is performed. Are joined by. Note that the tip portion may be divided into two to form four terminals.

  The tip portions of the pair of electrodes 12a and 12b are bent downward to be provided with terminal portions 13a and 13b and leg portions 14a and 14b, respectively. One electrode 12a is provided with one terminal portion 13a and one leg portion 14a, and the other electrode 12b is provided with the other terminal portion 13b and the other leg portion 14b, and the terminal portions 13a and 13b are provided with leg portions. A pair of parts 14a and 14b are provided.

  The terminal portions 13a and 13b are a part of the pair of electrodes 12a and 12b, are provided below the resistor 11, and are formed to attach the shunt resistor to the mounting substrate 20. The pair of terminal portions 13 a and 13 b are positioned in parallel with the mounting substrate 20, and the lower surfaces thereof are connected to the mounting substrate 20. Further, the pair of terminal portions 13a and 13b extend in the direction in which the resistor 11 is located, and the tip portions thereof are opposed to each other so as to be substantially U-shaped as a whole.

  The leg portions 14a and 14b are a part of the pair of electrodes 12a and 12b. The leg portions 14a and 14b are erected upward from the outer ends of the pair of terminal portions 13a and 13b. Is standing up. Furthermore, it is perpendicular to the mounting substrate 20 and connects the resistor 11 and the terminal portions 13a and 13b.

Further, the first metal layer 16 is formed on the lower portion of the side surface 15 at a position away from the resistor 11 of the pair of leg portions 14a and 14b. The first metal layer 16 is also formed on the lower surfaces of the terminal portions 13a and 13b, and is continuous from the lower surfaces of the terminal portions 13a and 13b to the side surfaces 15 of the pair of leg portions 14a and 14b. The first metal layer 16 may also be formed on the side surfaces 13c of the tip portions of the terminal portions 13a and 13b facing each other. The first metal layer 16 has a pair of legs 14a and 14b.
It is provided from the lower end of the side surface 15 to the middle of the side surface 15 of the pair of leg portions 14a, 14b, and is not formed on the entire side surface 15 of the pair of leg portions 14a, 14b.

  The first metal layer 16 is made of a material having better solder wettability than the pair of electrodes 12a and 12b, tin and gold can be used, and the first metal layer 16 is formed by plating this metal.

  Here, in order to stabilize the formation location of the first metal layer 16, the length of the first metal layer 16 in the vertical direction (the first metal layer 16 and the covering layer 17 from the lower ends of the pair of leg portions 14a and 14b). It is necessary to stabilize the distance to the boundary 16a. For this reason, there is a method of masking a predetermined area on an unnecessary portion when plating tin or the like. Moreover, you may dip with the terminal parts 13a and 13b down.

  The covering layer 17 is provided at a location where the first metal layer 16 is not formed at the upper part of the side surface 15 of the pair of leg portions 14 a and 14 b, and is made of a material having poorer solder wettability than the first metal layer 16. Has been. As the coating layer 17, a metal oxide obtained by oxidizing copper, which is a material of the pair of leg portions 14a and 14b (the pair of electrodes 12), can be used. After the first metal layer 16 is formed by plating on the lower part of the side surface 15 of the pair of leg portions 14a, 14b, the other portions of the side surface 15 of the pair of leg portions 14a, 14b are covered with heat treatment or left to stand naturally. Layer 17 is formed. In this way, the coating layer 17 can be easily formed. In FIG. 1 and FIG. 2, the coating layer 17 is provided only on the side surface 15 of the pair of leg portions 14a and 14b, but is also formed on other portions of the pair of electrodes 12a and 12b.

  The coating layer 17 may be formed by applying a resin. In this case, the first metal layer is formed after the resin is applied in advance to the portion where the first metal layer 16 is not formed or after the first metal layer 16 is formed. A resin is applied to a portion where 16 is not formed.

  The side surfaces 15 of the pair of leg portions 14 a and 14 b are covered with a first metal layer 16 at the bottom and a coating layer 17 at the top. The length of the first metal layer 16 (the distance from the lower end of the pair of leg portions 14a and 14b to the boundary 16a between the first metal layer 16 and the covering layer 17) is equal to the side surface 15 of one leg portion 14a and the other side. The side surfaces 15 of the leg portions 14b are substantially equal.

  In FIG. 2, the land 21 and the shunt resistor of the mounting substrate 20 are mounted via a mounting solder layer 22 formed by tin plating. The mounting solder layer 22 is formed on the first metal layer 16 having good solder wettability, but is not formed on the coating layer 17 having poor solder wettability. As a result, the mounting solder layer 22 goes up only to the upper end 16a of the first metal layer 16 (the boundary between the first metal layer 16 and the covering layer 17). Therefore, the current enters the shunt resistor from the upper end 16a of the first metal layer 16, and when the position of the upper end 16a is stabilized, the distance through which the current flows becomes constant. The mounting solder layer 22 is also formed on the first metal layer 16 on the lower surfaces of the terminal portions 13a and 13b.

  In addition, it is preferable that the vertical length of the first metal layer 16 is 1/2 to 2/3 with respect to the vertical length of the side surface 15 of the pair of leg portions 14a and 14b. If the length is shorter than 1/2, the position of the upper end 16a where the current flows in and out becomes low, and the resistance value cannot be lowered. If the length is longer than 2/3, the amount of the mounting solder layer 22 increases, and the thermal stress cannot be absorbed. Problems such as cracks in the mounting solder layer 22 occur.

  As shown in FIG. 3, a second metal layer 18 having a solder wettability worse than that of the first metal layer 16 may be formed as the coating layer 17.

That is, the second metal layer 18 is formed between the first metal layer 16 and the legs 14a and 14b, and a part of the second metal layer 18 is exposed from the first metal layer 16 and the exposed second metal layer. 18 becomes the coating layer 17. As the second metal layer 18, nickel, iron, or zinc can be used.

  The location where the mounting solder layer 22 is formed can be stabilized by the second metal layer 18 having poor solder wettability. Further, it is not necessary to form a metal oxide.

  Furthermore, when the length of the first metal layer 16 is substantially equal to the length of the land 21 of the mounting substrate 20, the angle of the mounting solder layer 22 (fillet) becomes 45 °, which is preferable.

  In the shunt resistor according to the embodiment of the present invention, the pair of leg portions 14a and 14b that stand up with respect to the mounting substrate 20 has a side surface 15 positioned in a direction away from the resistor 11 and a part of the lower portion thereof. A first metal layer 16 that is formed and has better solder wettability than the pair of electrodes 12a and 12b, and a coating that is provided on the side surface 15 where the first metal layer 16 is not formed and has poorer solder wettability than the first metal layer 16 Since the layer 17 is provided, the formation location of the first metal layer 16 can be stabilized, whereby the formation location of the mounting solder layer 22 can be stabilized, and thereby the resistance value can be stabilized. An effect is obtained.

  That is, since the mounting solder layer 22 is formed on the first metal layer 16 but not on the covering layer 17, the length in the vertical direction from the lower end of the first metal layer 16 is as described above. If it prescribes | regulates using a mask, the location where the solder layer 22 for mounting will connect to a pair of leg parts 14a and 14b is specified. The place where the current flows from the mounting solder layer 22 to the pair of legs 14a and 14b (the pair of electrodes 12a and 12b) is the upper end of the first metal layer 16 (the boundary between the first metal layer 16 and the covering layer 17) 16a. Therefore, the place where the current flows to the pair of legs 14a and 14b is constant, and as a result, the distance through which the current flows is constant, and the resistance value can be prevented from varying.

  If the location where the solder layer for mounting 22 is connected to the pair of legs 14a and 14b varies, the resistance value fluctuates. However, since the shunt resistor of the present invention has a low resistance value, the fluctuation of the resistance value is The effect on the resistance value is large.

  Note that the pair of terminal portions 13a and 13b may be extended from the direction away from the resistor 11 as shown in FIG. 4 instead of extending in the direction in which the resistor 11 is located.

  At this time, the mounting solder layer 22 is also formed on the other side surface (inner surface) 15a located in the direction approaching the resistor 11 of the pair of leg portions 14a and 14b. The current flows from the mounting solder layer 22 to the pair of leg portions 14a and 14b (the pair of electrodes 12a and 12b) through the inner surface 15a. Therefore, if the first metal layer 16 and the coating layer 17 having poorer solder wettability than the first metal layer 16 are formed on the inner surface 15a and the formation position of the first metal layer 16 is stabilized, the resistance value is stabilized. Can be made.

  In FIG. 4, the pair of leg portions 14 a and 14 are perpendicular to the pair of terminal portions 13 a and 13 b (mounting substrate 20), but the pair of leg portions 14 a and 14 are paired with the pair of terminal portions. You may arrange | position so that it may become diagonal with respect to 13a, 13b.

  The shunt resistor according to the present invention has an effect that the resistance value can be stabilized, and particularly by being applied to a high-power shunt resistor used for detecting a current value of various electronic devices. It will be useful.

DESCRIPTION OF SYMBOLS 11 Resistor 12a, 12b A pair of electrode 13a, 13b Terminal part 14a, 14b Leg part 15 Side surface of leg part 16 1st metal layer 17 Covering layer 18 2nd metal layer 20 Mounting board 21 Land 22 Mounting solder layer

Claims (6)

A resistor composed of metal and a pair of electrodes connected to both ends of the resistor, each of the pair of electrodes being provided below the resistor and extending in a direction in which the resistor is located; A terminal part for mounting the mounting board; and a leg part that stands up with respect to the mounting board and connects the resistor and the terminal part, and is a direction away from the resistor of the pair of leg parts A first metal layer that is formed on a part of the lower part of each side surface and has better solder wettability than the pair of electrodes, and the first metal layer that is provided in a place where the first metal layer is not formed. A shunt resistor with a coating layer with poorer solder wettability. A resistor made of metal and a pair of electrodes connected to both ends of the resistor, each of the pair of electrodes being provided below the resistor and extending away from the resistor A terminal part for mounting the mounting board; and a leg part that stands up with respect to the mounting board and connects the resistor and the terminal part; and the pair of leg parts near the resistor. A first metal layer formed on a part of the lower side of each of the side surfaces and having better solder wettability than the pair of electrodes, and provided at a place where the first metal layer is not formed, from the first metal layer A shunt resistor with a coating layer with poor solder wettability. The shunt resistor according to claim 1, wherein the covering layer is an oxide of a metal constituting the pair of electrodes. A second metal layer having poorer solder wettability than the first metal layer is formed between the first metal layer and the leg, and a part of the second metal layer is exposed from the first metal layer. The shunt resistor according to claim 1, wherein the exposed second metal layer is the covering layer. The shunt resistor according to claim 1, wherein a length of the first metal layer is substantially equal to a length of a land of the mounting substrate. The shunt resistor according to any one of claims 1 and 2, wherein the length of one of the first metal layers and the other of the first metal layers in the vertical direction is substantially equal.

Images