JP7404426B2 - Current detection resistor and method for manufacturing current detection resistor - Google Patents

Description

The present invention relates to a current detection resistor and a method for manufacturing a current detection resistor.

As a current detection resistor mounted on a circuit board via solder, it has a main body part formed of a metal plate and has a predetermined resistance value, and a main body part connected to both ends of the main body part. A resistor having a soldering part for soldering the part onto a circuit board is disclosed (see Patent Document 1).

JP2009-206290A

In the resistor described in Patent Document 1, a resistor material such as copper-nickel, nickel-chromium, or copper-manganese-nickel is used as the metal material for the main body. However, in copper-manganese-nickel-based resistor materials that are commonly used as resistor materials, manganese (Mn) in the component is easily oxidized at high temperatures, and as the oxidation progresses, the resistance value changes greatly.

For this reason, in copper manganese nickel based resistor materials, a temperature of about 170 to 180° C. is set as the upper limit temperature at which fluctuations in resistance can be kept within an allowable range.

On the other hand, in recent years, with the spread of electric vehicles and the increasing functionality of electronic devices, there has been an increasing demand for higher power and higher heat resistance for circuit boards on which electronic components are mounted. In particular, the development of semiconductor elements that operate at high temperatures, such as SiC and GaN, which are called wide-gap power semiconductors, is progressing.

Accordingly, current detection resistors mounted on circuit boards are also required to have specifications that allow them to be used at temperatures higher than the above temperature, for example, in a temperature range of 200° C. or higher.

An object of the present invention is to provide a current detection resistor that suppresses a large change in resistance value in a high temperature region, and a circuit board on which the current detection resistor is mounted.

As a result of extensive research, the present inventors have focused on the fact that an alloy of nickel, chromium, and molybdenum has high heat resistance, and have completed the present invention.

A current detection resistor as an aspect of the present invention is formed from a plate of a resistor material, and the resistor material includes an alloy of nickel, chromium, and molybdenum, and the total mass ratio of the alloy is Contains 63% by mass or more and 70% by mass or less of chromium, 8% by mass or more and 22% by mass or less of the molybdenum, and changes in resistance after 1000 hours at 200°C. The ratio is within ±0.50%.

According to this aspect, by using an alloy of nickel, chromium, and molybdenum that has high heat resistance as the resistor material, it is possible to suppress a change in resistance value from increasing in a high temperature range.

FIG. 1 is a plan view illustrating an example of a current detection resistor according to an embodiment of the present invention. FIG. 2 is a side view of the current detection resistor shown in FIG. 1. FIG. 3 is a diagram illustrating a method of manufacturing a current detection resistor according to this embodiment. FIG. 4 is a diagram illustrating a circuit board on which a current detection resistor is mounted.

[Description of current detection resistor]
A current detection resistor according to an embodiment of the present invention will be explained in detail using FIGS. 1 to 4.

<Structure of current detection resistor>
FIG. 1 is a plan view illustrating an example of a current detection resistor according to this embodiment. Moreover, FIG. 2 is a side view of the current detection resistor shown in FIG. 1.

The current detection resistor 1 is a plate-shaped shunt resistor made of a resistor material containing an alloy of nickel (Ni), chromium (Cr), and molybdenum (Mo).

The current detection resistor 1 includes a main body portion 11 , a first connection portion 12 , a second connection portion 13 , a first standing portion 14 , and a second standing portion 15 .

The main body portion 11 has a rectangular shape and is arranged at a predetermined distance from the mounting surface of the circuit board.

One end of the first connecting portion 12 is connected to the mounting surface. Further, the other end of the first connecting portion 12 is connected to the main body portion 11 via the first standing portion 14 . One end of the second connecting portion 13 is connected to the mounting surface. Further, the other end of the second connecting portion 13 is connected to the main body portion 11 via the second upright portion 15 . The first upright portion 14 and the second upright portion 15 connect the end of the main body portion 11 to the first connection portion 12 and the second connection portion 13 so as to separate the main body portion 11 from the mounting surface.

In this embodiment, as shown in FIG. 2, the first connection part 12 and the second connection part 13 include a mounting surface plating layer 16 formed on the surface facing the mounting surface, and a mounting surface plating layer 16 formed on the surface facing the mounting surface. It has a plating layer 17 for bonding formed on the opposite surface of the plating layer 17 for bonding, and an end surface electrode 18 formed continuously from the plating layer 16 for the mounting surface and the plating layer 17 for bonding. Note that the end surface electrode 18 may be omitted.

The current detection resistor 1 can be formed by pressing a plate made of a resistor material.

<Resistor material>
In this embodiment, the resistor material forming the current detection resistor 1 includes an alloy of nickel, chromium, and molybdenum, and the total mass ratio of this alloy is 63% by mass or more and 70% by mass or less of nickel, chromium It contains 8% by mass or more and 22% by mass or less of molybdenum, and 8% by mass or more and 25% by mass or less of molybdenum.

From the viewpoint of improving the heat resistance of the resistor, the molybdenum content should be higher. However, since molybdenum has high hardness and is brittle, when the content of molybdenum becomes excessive, the workability of the resistor material decreases. Therefore, the molybdenum content is set to 8% by mass or more and 25% by mass or less.

Furthermore, the resistor material may contain 6% by mass or less of at least one of tungsten (W) and manganese (Mn) based on the total mass ratio of the alloy. When the resistor material contains at least one of tungsten and manganese in an amount of 6% by mass or less based on the total mass ratio of the alloy, heat resistance can be ensured without increasing the content of molybdenum in the resistor material.

When using a commercially available product as the above resistor material, DSALOY625 (manufactured by Daido Steel Co., Ltd.) containing 22% by mass of chromium, 8% by mass of molybdenum, and 70% by mass of nickel; DSALOY22 (manufactured by Daido Steel Co., Ltd.) containing 13% by mass of chromium, 3% by mass of tungsten, and 63% by mass of nickel; (manufactured by Tokushu Steel Co., Ltd.) can be suitably used.

Among these, DSALOY242, which contains 8% by mass of chromium, 25% by mass of molybdenum, and 67% by mass of nickel, is preferably used because of its small change in resistance value and low temperature coefficient of resistance (TCR). .

[Method of manufacturing current detection resistor]
FIG. 3 is a diagram illustrating a method of manufacturing a current detection resistor according to this embodiment. The method for manufacturing a current detection resistor includes an alloy of nickel, chromium, and molybdenum, and the total mass ratio of the alloy is 63% to 70% by mass of nickel, 8% to 22% by mass of chromium, A resistor material containing 8% by mass or more and 25% by mass or less of molybdenum is pressed into a predetermined shape.

When the above-mentioned resistor material is heated to 200°C or higher, the resistance value changes greatly over a predetermined period while the temperature is rising, and after the predetermined period has elapsed, the resistance of the resistor material decreases. It has the behavior that the value converges at a specific point. In this resistor material, the Vickers hardness of the resistor material is 200 HV or more and 240 HV or less when the change in resistance value converges at a specific point.

Therefore, in this manufacturing method, the resistance element obtained by press processing is treated to have a Vickers hardness of 200 HV or more and 240 HV or less, thereby making it possible to manufacture a resistor material with small fluctuations in resistance value. can.

Specifically, as shown in FIG. 3, before pressing the above-mentioned alloy of nickel, chromium, and molybdenum into a predetermined shape, the resistor material is subjected to a first process so that the Vickers hardness of the resistor material is 220 HV or more and 290 HV or less. Perform the first process. Subsequently, the resistor material is pressed, and a second treatment is performed to reduce the Vickers hardness of the resistor obtained by pressing by 15% to 25%.

As the second treatment, heat treatment can be used in which the resistor after press working is exposed to a temperature of 175° C. or higher for 200 hours or more. As an example, it is preferable to perform a treatment of exposing to 200° C. or higher for 250 hours. Thereby, a resistor having a Vickers hardness of 200 HV or more and 240 HV or less can be obtained.

In this way, by pre-treating the resistor material so that the Vickers hardness is 200 HV or more and 240 HV or less, it is possible to enhance the effect of suppressing a large change in resistance value.

[Circuit board]
FIG. 4 is a diagram illustrating a circuit board on which a current detection resistor according to an embodiment of the present invention is mounted.

The circuit board 100 according to the present embodiment includes an insulating substrate 110 and a circuit pattern 120 formed on the insulating substrate 110, and the current detection resistor 1 described above has a first connection portion 12 and a second connection portion. 13 is a circuit board connected to the circuit pattern 120 by wire bonding 130 or solder mounting electrodes 140.

In this embodiment, a glass epoxy substrate, a metal substrate, or a ceramic substrate can be used as the insulating substrate 110. Among these, it is preferable to use a ceramic substrate from the viewpoint of high heat resistance. In this embodiment, at least one material selected from the group consisting of aluminum oxide, silicon nitride, and aluminum nitride can be used as the ceramic substrate.

The thickness of the ceramic substrate can be 0.1 mm or more and 1.0 mm or less. From the viewpoint of the strength of the substrate, the thickness of the ceramic substrate is preferably 0.1 mm or more. Further, from the viewpoint of heat dissipation, the thickness is preferably 1.0 mm or less.

Copper (Cu), which is generally used as an electrode for connecting the circuit pattern 120 and the current detection resistor 1, has low heat resistance and is easily oxidized. Therefore, in this embodiment, nickel-based plating and gold-based plating can be used to improve heat resistance. Among these, nickel-tungsten plating, nickel-phosphorus plating, nickel-tungsten/gold plating, nickel-phosphorus/gold plating, nickel/gold plating, etc. are preferably used.

[Other embodiments]
Although the embodiments of the present invention have been described above, the above embodiments merely show a part of the application examples of the present invention, and the purpose is to limit the technical scope of the present invention to the specific configuration of the above embodiments. isn't it. For example, the shape of the current detection resistor 1 according to this embodiment is not limited to that illustrated in FIG. 1 .

A current detection resistor according to an embodiment of the present invention was manufactured, and its heat resistance and resistance characteristics were evaluated. The preparation method and evaluation method of the specimen are as follows.

[Preparation of specimen]
<Example 1>
As a nickel-chromium-molybdenum alloy (hereinafter referred to as Ni-Cr-Mo alloy), DSALOY625 (manufactured by Daido Steel Co., Ltd., 22Cr- 8Mo-70Ni) was processed into a plate shape, and then the resistor shown in FIGS. 1 and 2 was fabricated. The dimensions of each part are as follows.

Ld=5.0mm
Lc=3.2mm
d=0.2mm

<Example 2>
As a Ni-Cr-Mo alloy, DSALOY22 (manufactured by Daido Steel Co., Ltd., 21Cr-13Mo-3W-63Ni and A specimen was prepared in the same manner as in Example 1, except that the following materials were used.

<Example 3>
Except for using DSALOY242 (manufactured by Daido Steel Co., Ltd., written as 8Cr-25Mo-67Ni) containing 8% by mass of chromium, 25% by mass of molybdenum, and 67% by mass of nickel as the Ni-Cr-Mo alloy. A specimen was prepared in the same manner as in Example 1.

<Comparative example>
A specimen was produced in the same manner as in Example 1 except that a copper manganese nickel based resistor material was used instead of the Ni--Cr--Mo alloy.

[Measuring method]
<Volume resistivity>
Since the width and thickness of the main body 11 of the sample are constant, the cross-sectional area of the main body 11 is uniformly S (cm ² ) along the longitudinal direction of the main body 11 . Therefore, the volume resistivity ρ of the resistor material is determined by the voltage V between the first connection part 12 and the second connection part 13, the current I, the cross-sectional area S (cm ² ), and the difference between the first connection part 12 and the second connection part 13. It is calculated from the length Ld (cm) between the second connecting portions 13 using the following formula.
ρ=(V/I)×(S/Ld) [ ^10-6 Ω・cm]
In this measurement, the allowable range of volume resistivity ρ is 120 to 150 [10 ⁻⁶ Ω·cm].

<Measurement of temperature coefficient of resistance (TCR)>
The temperature coefficient of resistance (TCR) represents the rate of change in internal resistance value due to temperature change of a resistor, and is calculated by the following formula.
Temperature coefficient of resistance (ppm/℃) = (R-Ra)/Ra÷(T-Ta)×1000000
Here, Ra: resistance value at reference temperature, Ta: reference temperature, R: resistance value in steady state, T: temperature at which the steady state is reached.
In this example, Ta=25°C and T=100°C. In addition, based on the product specifications, the allowable range of TCR was set to ±100 ppm/°C. The measurement results are shown in Table 1.

<Heat resistance test: Rate of change in resistance value of resistor>
The specimens of Examples 1 to 3 and Comparative Example were subjected to a heat-standing test in which they were heated to 200°C and maintained at 200°C for a predetermined period of time, and changes in resistance values due to differences in standing time were measured.
The rate of change in resistance value is calculated by the following formula.

Resistance value change rate (%) = {(Rh-Ra)/Ra}×100
Here, Ra is the resistance value before the heat exposure test, and Rh is the resistance value after a predetermined time has elapsed in the heat exposure test. The results are shown in Table 1.
In this measurement, the rate of change in resistance value is allowed to be within the range of ±0.50% even after 1000 hours.

<Vickers hardness>
Vickers hardness can be measured according to Japanese Industrial Standard JIS Z2244:2009 (Vickers hardness test - test method). A hardness meter (for example, Micro Vickers hardness meter HMV-G21: Shimadzu Corporation) is used to measure the Vickers hardness. Vickers hardness can be measured, for example, under the conditions of a test temperature of 25° C., a test force of 100 gf, a diamond indenter approach speed of 20 μm/s, and a test force retention time of 10 seconds. It is desirable that the surface of the test piece be smoothed using a polishing machine (for example, automatic polishing machine Rana-3: IMT) or the like to remove dirt and the like.

[result]
Table 1 shows the heat resistance test, volume resistivity, temperature coefficient of resistance (TCR), heat resistance test, and Vickers hardness.

In Examples 1 to 3 in which the heat resistance test was conducted, the rate of change in resistance value of the specimens was generally within the range of 0 to 0.20% or 0 to 0.40%. Therefore, it can be seen that when the Ni-Cr-Mo alloy according to this embodiment is used as a resistor material, the rate of change in resistance value of the resistor material can be stabilized even at a high temperature of 200°C. These rates of change in resistance value are considered to be sufficiently low and good values, but in all examples, the rate of change in resistance value was significantly observed for 250 hours from the start of heating. I know that there is. Furthermore, it can be seen that the rate of change in resistance value remains flat after approximately 250 hours.

From the above, if heat treatment is performed under the conditions of 200°C/250 hours in advance, the change in resistance value of the resistor material will be stabilized, and the current detection resistor can be attached to the circuit board while the rate of change is small. can be implemented in

From this, the current detection resistor according to the present embodiment includes an alloy of nickel, chromium, and molybdenum, and the total mass ratio of the alloy is 63% by mass or more and 70% by mass or less of nickel, and 8% by mass of chromium. According to a resistor material containing molybdenum in an amount of 8% to 25% by mass, stabilization of the resistance value can be achieved at a high level in a higher temperature range.

1 Current detection resistor 11 Main body 12 First connection portion 13 Second connection portion 14 First standing portion 15 Second standing portion 16 Plating layer for mounting surface 17 Plating layer for bonding 100 Circuit board 110 Insulating substrate 120 Circuit pattern 130 wire bonding

Claims (8)

A current detection resistor,
Formed from a plate of resistor material,
The resistor material includes an alloy of nickel, chromium, and molybdenum,
The nickel is 63% by mass or more and 70% by mass or less in the total mass ratio of the alloy,
The chromium is 8% by mass or more and 22% by mass or less,
Containing the molybdenum in an amount of 8% by mass or more and 25% by mass or less,
The rate of change in resistance value after 1000 hours at 200°C is within ±0.50%,
Resistor for current detection. The current detection resistor according to claim 1,
The Vickers hardness of the resistor material is 200 HV or more and 240 HV or less,
Resistor for current detection. The current detection resistor according to claim 2,
a main body portion having a rectangular shape, facing the mounting surface and disposed at a predetermined distance from the mounting surface;
a first connection part connected to the mounting surface;
a second connection part connected to the mounting surface,
the first connection portion and the second connection portion include a plating layer;
Resistor for current detection. The current detection resistor according to any one of claims 1 to 3,
The resistor material has a heat resistance of 200° C. or more,
Resistor for current detection. A method of manufacturing a current detection resistor, the method comprising:
Including an alloy of nickel, chromium, and molybdenum, the total mass ratio of the alloy is 63% to 70% by mass of nickel, 8% to 22% by mass of chromium, and 8% to 25% by mass of molybdenum. % by mass or less, and the rate of change in resistance after 1000 hours at 200 ° C. is pressed into a predetermined shape .
A method of manufacturing a current detection resistor. A method for manufacturing a current detection resistor according to claim 5, comprising:
After the press working, a treatment is performed so that the Vickers hardness of the resistor material is 200 HV or more and 240 HV or less,
A method of manufacturing a current detection resistor. A method for manufacturing a current detection resistor according to claim 5 or 6, comprising:
Before the press working, a treatment is performed so that the Vickers hardness of the resistor material is 220 HV or more and 290 HV or less,
A method of manufacturing a current detection resistor. A method for manufacturing a current detection resistor according to any one of claims 5 to 7, comprising:
a first heat treatment performed before the press working;
A method of manufacturing a current detection resistor, comprising: a second heat treatment performed after the press working.

Images