JP4189005B2 - Chip resistor - Google Patents

Description

  The present invention relates to a chip resistor for current detection.

  It is well known to use a resistor (hereinafter referred to as a shunt resistor) having a very small resistance value of about milliohm for detecting a large current. In the detection of the large current I (A) using this shunt resistor, the high current I (A) is passed through the shunt resistor R (Ω) having a known low resistance value and a small variation in resistance value. The voltage drop V (V) across the shunt resistor at the time is measured, and the current value I (A) is calculated using I = V / R.

  An example of a shunt resistor is shown in FIG. The shunt resistor 1000 includes a metal resistance portion 1400 and two electrode portions 1100. For the resistance portion 1400, for example, a metal alloy such as a Cu—Ni alloy (for example, CN49R) is used. The electrode 1100 is subjected to solder plating 1200 in consideration of solderability.

  Here, the characteristics of the shunt resistor include a temperature coefficient of resistance (TCR: Temperature Coefficient of Resistance) and a change in resistance value before and after use when the shunt resistor is used for a long time under a predetermined condition (for example, 1000 hours) ( Life test).

  Here, the temperature coefficient of resistance (TCR) is obtained by the equation (1), and the resistance value change ΔR / R before and after the 1000 hour life test is evaluated by using the equation (2).

TCR = ((R ₁ −R ₀ ) / R ₀ ) × (1 / (T ₁ −T ₀ )) (1)
R1: resistance value at the measurement temperature _{T 1 (Ω), T 1} : Measurement temperature R0: the resistance value at the reference temperature _{T 0 (Ω), T 0} : a reference temperature _{ΔR / R = (R 1000 -R} 0) / R 0 (2)
R ₁₀₀₀ : Resistance value after a life test of 1000 hours (Ω)
R ₀ : resistance value before life test (Ω)
Further, in order to mount the shunt resistor on a printed wiring board or the like, it is necessary to make the shunt resistor smaller and to have a structure suitable for high-density mounting.

  By the way, in order to accurately measure a large current using a shunt resistor, it is necessary to make it as close as possible to the set temperature coefficient of resistance, which is a characteristic of the shunt resistor, or to reduce the temporal change in resistance during use. is there. Further, it is necessary to improve the voltage (V) -current (I) characteristics by reducing a change in resistance value with respect to the current when a large current is passed.

  In the shunt resistor 1000 shown in FIG. 7, in order to obtain a predetermined resistance value, several notches indicated by 1300 are made in the resistance portion 1400 using a laser processing machine or the like. This notch 1300 is necessary for resistance adjustment, but causes the characteristics of the shunt resistor 1000 to deteriorate.

An object of the present invention is that the measurement accuracy of the current to provide a chip resistor which is suitable for high-density mounting coincide with high small.

In order to achieve the above object, a chip resistor of the present invention has the following configuration. That is, the resistor has no side notch, and the pair of electrodes is a thick metal plate having an electric resistance smaller than that of the resistor , and each electrode of the pair of electrodes is formed on the substrate , respectively . The entire surface of the surface to be bonded to the resistor opposite to the substrate bonding surface to be bonded is laminated and clad bonded so that the entire surface of the resistor does not protrude from the same surface of the resistor. The bonding surface of the resistor protrudes toward the substrate on which the chip resistor is mounted by the thickness of the thick metal plate, and the surface of each electrode of the pair of electrodes is formed between the resistor and the electrode. solder layer by bonding surface and the only the substrate bonding surfaces of said pair of electrodes so that the surface of each electrode, except the substrate bonding surfaces of the solder film is formed remains exposed molten solder material of the electrode Is formed It is characterized by.

  For example, at least one surface of the resistor of the chip resistor is exposed.

According to the present invention, it is possible to provide a chip resistor which is suitable for high-density mounting with a small measurement accuracy of the current is rather high.

  Hereinafter, a shunt resistor 100 and a method for manufacturing the shunt resistor 100 according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

  Note that the alloy composition used as the resistor of the shunt resistor described in this embodiment is an example, and unless otherwise specified, the scope of the present invention is limited only to them. Instead, it is determined according to the required characteristics and specifications of the shunt resistor to be manufactured.

[Structure of shunt resistor]
FIG. 1 shows a shunt resistor 100 according to the present embodiment soldered onto a conductor pattern of a substrate 140. The shunt resistor 100 includes 110 metal resistors and electrodes 121 and 122 which are connection terminals.

  The shunt resistor 100 has a structure in which two rectangular parallelepiped electrodes 121 and 122 are joined to a resistor 110 having one rectangular parallelepiped shape as shown in FIG. The thickness of the resistor is about 100 to 1000 μm. Moreover, the thickness of each electrode is about 10-300 micrometers. Further, a solder film of about 2 to 10 μm is formed on the surface of each electrode.

  The shunt resistor 100 is designed to easily dissipate heat. For example, an aluminum substrate is used as the substrate 140 for mounting on a printed wiring board or the like, and the substrate 140 is also connected to a heat sink or the like. It has become.

  That is, since heat generated in the shunt resistor 100 when high current is measured is transmitted in the direction of the substrate 140, the junction surface between the shunt resistor 100 and the substrate 140 is important. The electrodes 121 and 122 which are the joint surfaces with the substrate 140 are made of copper thick plates having good heat conduction, and have a large joint area.

  Further, a current when measuring a high current flows from the pattern of the substrate 140 to the resistor 110 via one electrode 121 of the shunt resistor 100 and further flows from the resistor 110 to another one electrode 122. Further, the voltage drop between the electrode 121 and the electrode 122 when a high current is passed, that is, across the shunt resistor 100 is measured. Therefore, the shunt resistor 100 having the structure of FIG. 1 can be used with a large current.

  As the material for the resistor 110, for example, a Cu—Ni alloy (CN49R, etc.), various metal alloys shown in FIG. 4 and various noble metal alloys are used, and specific resistance, TCR, change in resistance value, etc. determined according to specifications are used. A metal alloy or a noble metal alloy suitable for the various characteristics is appropriately selected from FIG. 4 and used. In addition to FIG. 4, for example, manganese / copper / nickel alloy may be used.

  In addition, as shown in FIG. 4, when a noble metal alloy is used, a resistor 110 having an extremely low electric resistance of about 2 to about 7 μΩ · cm is obtained. For example, these noble metal alloys are used as the resistor 110. When used, the resistance value of the shunt resistor 100 having the structure shown in FIG. 1 is about 0.04 to 0.15 mΩ.

  As a material for the electrodes 121 and 122, a copper material (for example, about 1.5 μΩ · cm) whose electrical resistance is smaller than that of the resistor 110 is used, and the resistor 110 and the electrode 121 or the resistor 110 and the electrode 122 are used. Are joined by clad joining. The electrode surfaces of the two electrodes 121 and 122 are designed to have a large electrode area so that heat is easily transferred in the direction of the substrate 140 in order to easily dissipate heat generated when measuring a high current. It is characterized by using a copper plate with good thermal conductivity and a large bonding area.

  In addition, on the surfaces of the electrodes 121 and 122, in order to improve the solderability to the conductor pattern of the substrate, for example, films 131 and 132 of a molten solder material (Sn: Pb = 9: 1) or a lead-free solder material are provided. Is formed. Since the molten solder material has a diffusion layer between the copper electrode 121 or 122, the bonding strength and electrical reliability of the electrode are improved.

  The feature of the shunt resistor 100 is that the resistor 110 has a simple structure consisting of a flat plate, and there is no notch 1300 as seen in the conventional shunt resistor 1000. Since there is no cut in the resistor 110 in this way, the current path when a large current flows is stabilized, and the resistance value change (ΔR / R) can be suppressed to about 0.1% or less, and the cut is not generated. The change in resistance value can be reduced to about 1 / several 10 to 1/200 compared to the change in resistance value (ΔR / R) in a certain case to 20%.

  Further, when a noble metal alloy having an extremely low electric resistance of about 2 to 7 μΩ · cm is used for the resistor 110, the resistance value of the shunt resistor 100 is about 0.04 to 0.15 mΩ, so that a high current measurement is performed. A shunt resistor suitable for the above can be obtained.

[Production method of shunt resistor]
Next, a manufacturing method of the shunt resistor 100 will be described below with reference to FIGS. FIG. 2 shows an example of a manufacturing method of the shunt resistor 100, and FIG. 3 shows each material used in each manufacturing process of FIG. 2 and the shape of the shunt resistor 100 to be manufactured. .

  In FIG. 2, for example, a copper material having a specific resistance of about 1.5 μΩ · cm is selected as the copper alloy 230 of the electrode material, and is processed into a predetermined dimension in the material processing 240 step.

  Further, as the resistance material alloy 210, for example, selected from various metal alloys and various precious metal alloys having a predetermined specific resistance shown in FIG. To be processed.

  Next, the copper material 120 shown in FIG. 3 and the resistor 110 shown in FIG. Since the interface between the resistor 110 and the electrode 120 in the bonded body 310 is firmly bonded by the diffusion layer, the bonding strength and electrical reliability between the resistor 110 and the electrode 120 are improved.

  Next, part of the electrode 120 is removed so that the joined body 310 becomes a joined body having a predetermined shape indicated by 320 in FIG. For example, using a cutting device, the central portion 123 of the electrode 120 shown by 320 in FIG. 3 is removed until the resistor 110 is exposed, and the electrode 120 is divided into 121 and 122. The thickness of the electrode 121 and the electrode 122 is about 10 to 300 μm. The thickness of the resistor 110 is about 100 to 1000 μm.

  Next, in the joined body 320, a solder film of about 2 to 10 μm indicated by 131 and 132 is formed on the surfaces of the electrode 121 and the electrode 122 in the molten solder processing 270 step, and the joined body 330 is obtained. As the solder used at this time, for example, a molten solder material (Sn: Pb = 9: 1) or a lead-free solder material is used.

  Since a diffusion layer is formed between the molten solder material and the copper electrode 120, the molten solder material 131 and the electrode 121, and the molten solder material 132 and the electrode 122 are firmly bonded. Therefore, the bonding strength at these interfaces is high and the electrical reliability is improved, and further, the shunt resistor 100 can be soldered to the conductor pattern of the aluminum substrate 140 via the molten solder materials 131 and 132.

  Next, the joined body 330 is cut into a predetermined length using a laser processing machine, a press processing machine, a wire electric discharge machine, a disk cutting machine, or the like in a cutting process 280 step, and has a predetermined dimension indicated by 340. For example, a thickness of about 0.1 to 20 mm is obtained.

  Next, the bonded body 340 is adjusted to have a predetermined resistance value in the resistance adjustment 290 step. That is, while measuring the resistance value of the bonded body 350, a part of the side surface portion or the surface portion of the bonded body 350 is removed by using a sandblasting method or various cutting machines such as a laser processing machine. As a result, the shunt resistor 100 having a predetermined resistance value is obtained.

[Characteristics of shunt resistor]
An example of the resistance value of the shunt resistor manufactured using the various metal alloys and the various noble metal alloys shown in FIG. 4 will be described below. For example, when the noble metal alloy having a low resistance of about 2 to about 7 μΩcm shown in FIG. 4 is used, the resistance value of the shunt resistor having the structure shown in FIG. 1 is about 0.05 to 0.14 mΩ. A shunt resistor having a value is obtained.

  FIG. 5 shows, as an example, the TCR value of the shunt resistor 100 manufactured by the present manufacturing method of FIG. 2 using CN49, which is a Cu—Ni-based alloy, as the resistor 110 and the change in resistance value after a life test of 1000 hours. . FIG. 5 also shows the TCR value of the shunt resistor 1000 manufactured by the conventional method shown in FIG. 7 and the change in resistance value after a 1000 hour life test as a comparison. As shown in FIG. 5, the shunt resistor 100 manufactured by this manufacturing method has a TCR value of about 1/3 or less and a change in resistance value of 1/20 to 1/30 or less compared to the conventional product. It can be seen that the characteristics are improved.

  Here, the TCR value of CN49, which is a Cu—Ni alloy, is about 50 ppm / ° C., which is very close to the TCR value of the shunt resistor 110. From this, it can be said that the shunt resistor 110 manufactured by this manufacturing method is a manufacturing method that can substantially reproduce the original TCR value of the Cu—Ni-based alloy (CN49). In addition, it can be said that the shunt resistor 1000 manufactured by the conventional manufacturing method works as an inhibiting factor that the resistance adjusting cut 1400 cannot express the original TCR value of the Cu—Ni alloy (CN49).

  Although not shown in FIG. 5, each of the metal alloys or base metal alloys shown in FIG. 4 is used as the resistor 110 of the shunt resistor 100 as the resistor 110, and the resistance value after a life test of 1000 hours. Made a change. As a result, the same TCR value and resistance value change value as those in FIG. 5 were obtained. From these facts, the shunt resistor 100 manufactured by the manufacturing method of FIG. 2 using each metal alloy or each base metal alloy shown in FIG. 4 as the resistor 110 has an excellent TCR value and resistance value change value. I understand that

  FIG. 6 shows the results of measuring the voltage (V) -current (I) characteristics of the shunt resistor 100 according to the present embodiment shown in FIG. 5 and the conventional shunt resistor 1000. From the result of FIG. 6, the change in the resistance value accompanying the increase in the current value of the shunt resistor 100 in which the resistor 110 is not cut can be suppressed to 0.1% or less, and excellent voltage (V) −current ( I) Characteristics were obtained.

  On the other hand, in the shunt resistor 1000 having many notches in the resistor, the resistance value increases by several percent to 20% as the current value increases, and the resistance value changes greatly when a large current is passed. This is because the current path is not stable when there is a cut. From this, it can be seen that in order to reduce the change in the resistance value of the shunt resistor when a large current is passed, a shape without a cut is desirable.

  As described above, according to the present embodiment, when a shunt resistor is manufactured, a low resistance material such as a noble metal alloy is used as a resistor, and a shunt resistor is not further cut into the resistor without making a resistance adjustment cut. By manufacturing the capacitor, a shunt resistor having a low resistance change rate and a current path suitable for high current measurement can be provided.

It is a schematic structure figure of the shunt resistor which is one embodiment of the present invention. It is a figure which shows the preparation methods of a shunt resistor. It is a figure which shows the shape of the joined body in each manufacturing process of a shunt resistor. It is a figure which shows the kind of resistor. It is the figure which compared the TCR value of a shunt resistor, and the resistance value change after a lifetime test. It is the figure which compared the VI characteristic of a shunt resistor. It is a schematic structural diagram of a conventional shunt resistor with a notch.

Explanation of symbols

100 Shunt Resistor 110 Resistor 121 Electrode 122 Electrode 131 Molten Solder Material 132 Molten Solder Material 140 Substrate

Claims (2)

A resistor made of a plate-like resistance alloy;
A pair of electrodes;
The resistor has no cut from the side,
Said pair of electrodes is a thick plate of metal electrical resistance is smaller than the resistor, the electrodes of the pair of electrodes is bonded substrate bonding surface to be bonded to the substrate, respectively and the resistor opposite are stacked so as not to protrude out from and the same plane on the same surface of the entire said resistor surface being planks thickness of the said metal from the joint surface of the resistor with the cladding bonded Only protrudes on the side of the substrate mounting the chip resistor,
Surface of each electrode of the pair of electrodes, remains the surface of the respective electrode except for the substrate bonding surfaces of the solder layer is formed of the bonding surface and the electrode of the electrode and the resistor is exposed As described above , the chip resistor is characterized in that a solder film made of a molten solder material is formed only on each substrate bonding surface of the pair of electrodes .   The chip resistor according to claim 1, wherein at least one surface of the resistor is exposed.

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