JP2963671B2 - Chip resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a chip resistor.

[0002]

2. Description of the Related Art Generally, a conventional chip resistor includes an insulating substrate 101 made of ceramic, glass or the like as shown in FIG.
And a resistor 105 formed of a Ni—Cr thin film on the insulating substrate 101 by using a sputtering technique or a vapor deposition technique,
An electrode (not shown) formed of a Cu—Ni thin film is provided at both ends of the resistor 105. As an electrode, copper of a low resistance metal is desirable, but an alloy with nickel is mainly used to impart weather resistance. Then, after the surface of the resistor 105 is covered with a resin protective film 106, both ends and the bottom surface of the insulating substrate 101 are also connected to the circuit board S by solder 109 via a Ni-Cr thin film or a Cu thin film or Cu- N
An electrode (not shown) made of an i-thin film is provided.
Solder is plated on the plating film.

In a chip resistor, its reliability largely depends on how stably the resistor is in close contact with the insulating substrate. In this regard, Ni-C vacuum-deposited as described above
The metal thin film such as r is sufficient to adhere to the ceramic and obtain a general-purpose resistance value of 10Ω-1MΩ.

[0004]

As an application of the chip resistor, for example, there is a load resistor for detecting a current flowing through a hard disk of a computer. In order to reduce the error in the detection value or to increase the detectable current value among them, the resistance value is 0.02Ω-10Ω on a 1.25 mm × 2.0 mm size substrate, There is a demand for a low-resistance high-power performance of 0.1 W or more. In addition, when it is also required to reduce the temperature coefficient of the resistor, the metals that can be used as the resistor are limited, and the only way to reduce the resistance is to increase the thickness.

However, when a resistor is to be provided by a vacuum deposition method as in the above-mentioned conventional chip resistor, a long deposition time is required to obtain a thick film, and (2) It is difficult to mass-produce industrially for the reason that the replacement life of a consumable such as a metal target to be a thin film material is shortened. In addition, despite the fact that the resistor itself generates heat and is therefore limited in power, no special heat radiating means is provided in the above-mentioned conventional chip resistor.

Therefore, a first object of the present invention is to provide a low-resistance chip resistor suitable for mass production. A second object is to provide a chip resistor capable of realizing a much higher allowable power than before.

[0007]

Means for Solving the Problems To achieve the above object, the inventor departed from the stereotype that "the resistor should be vacuum-deposited" and formed the resistor by plating. That is, a chip resistor according to the present invention is mounted on a circuit board and connected, and in a chip resistor which generates a predetermined resistance value, a bonding resistor formed of a thin film on the insulating substrate and a bonding layer formed on the insulating substrate. A plated resistor on the layer.

According to the present invention, since the thin film bonding layer exists between the insulating substrate and the resistor, the resistor is firmly bonded to the insulating substrate. Since the resistor itself is formed by plating, the thickness can be easily increased to reduce the resistance value, and the material can be selected from various metals that can be plated. Therefore, when it is desired to reduce the temperature coefficient of resistance, it is preferable to select a nickel alloy such as Ni-P as the resistor. In addition, since there is a thin-film bonding layer, an insulating substrate such as a ceramic such as alumina, aluminum nitride, or silicon nitride, or an insulating film such as a silicon oxide film on the surface of a metal having excellent heat dissipation properties such as copper or aluminum is also used as an insulating substrate. Various applications, such as those having, are applicable.

The resistor of the present invention also includes a resistor in which a bonding layer is extended to a connection portion with a circuit board, and a surface of the bonding layer at the connection portion is plated with a high thermal conductive film connected to a resistor. According to this configuration, the heat generated by the resistor is quickly dissipated to the circuit board through the highly heat conductive film. The high thermal conductive coating preferably comprises copper Cu or a Cu alloy. In this case, since Cu has poor solder resistance, it is desirable to cover this with a nickel Ni film.

[0010] As a bonding layer corresponding to the connection portion,
Not only one layer but also two or more layers may be used. In particular, the first layer is made of a Nichrome Ni-Cr alloy which is firmly bonded to the insulating substrate, and the copper Cu or copper nickel Cu which is firmly bonded to Ni-Cr and firmly bonded to the resistor is further formed thereon.
It is preferable to provide a Ni alloy as the second layer.

Further, the resistor according to the present invention is provided at both ends of the resistor.
A pair of electrodes is provided, and the
And an isolated island electrode are provided so as to be in contact with the resistor.
It is also characterized by According to this configuration, the current flowing between the electrodes at both ends of the resistor passes through the island electrode halfway.
Since the island electrode is a conductor having a lower resistance than the resistor, the amount of heat generated at that portion is negligibly smaller than the amount of heat generated by the resistor. Therefore, the heat-generating portion is substantially divided by the island electrodes, and the heat generated in each portion is quickly dissipated through the nearby electrodes. These electrodes are preferably provided on the bonding layer by plating before the resistor is plated, in order to reduce the resistance of the electrodes themselves and to dissipate heat more quickly.

[0012]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a main part of a chip resistor (hereinafter, simply referred to as a “resistor”) according to the embodiment, and FIG. 2 is a plan view of the same.

The resistor 10 includes an insulating substrate 1 made of alumina ceramic, and a Ni-type substrate provided on the surface of the insulating substrate 1.
Cr first bonding layer 21 and Cu-N formed thereon
i of the second bonding layer 22 and 4 to 30
Electrodes 41, 42, 43 plated with Cu to a thickness of μm
And a resistor 5 Ni-P plated to a thickness of 3 to 20 μm so as to cover the second bonding layer 22 and the electrodes 41, 42, 43. The thicknesses of the electrode and the resistor are appropriately set according to the target resistance value. Each bonding layer is formed by a thin film technique such as sputtering, vapor deposition, or ion plating.
However, the first bonding layer may be made of only Cr. Further, the second bonding layer may be made of only Cu or Ni. Electrodes 41, 4 at both ends
3 is conductively connected to an external circuit, but has a central island electrode 42
Are electrically isolated except that they are connected via the resistor 5.

The resistor 10 has a low resistance and a small temperature coefficient of resistance because the resistor 5 is made of Ni-P formed sufficiently thick by plating. When a voltage is applied between the electrodes 41 and 43, the current passes through the island electrode 42 halfway as indicated by the arrow. Since the island electrode 42 is a conductor made of Cu, the amount of heat generated at that portion is negligibly smaller than the amount of heat generated by the resistor 5. Therefore, the island electrode 4
There is no heat generating portion in the two portions, and the heat generating portion is substantially divided by the island electrodes, and the heat generated in each portion is quickly dissipated through the nearby electrodes. Only the resistor portion 51 sandwiched between the electrodes substantially functions as a resistor.

The resistance of the resistor 10 is generally adjusted by dissolving the resistor by a laser trimming method. In this example, particularly, only the central portion 52 of the resistor 5 and the corresponding portions of the bonding layers 21 and 22 are simultaneously dissolved and removed, so that the resistor is divided at the time of resistance adjustment as shown in FIG.
As a result, the resistor is divided into four parts in addition to the division by the island electrodes 42, and the heat generation part is dispersed. After the resistance adjustment, an epoxy resin 6 is applied to the surface of the resistor 5 and cured to prevent mechanical damage, as shown in FIG. However, the surfaces corresponding to the electrodes 41 and 43 at both ends are exposed for conductive connection with the circuit board. In general, the resistor 10 is not manufactured by itself alone. Up to this stage, a large number of thin films are simultaneously formed and plated on a large-sized insulating substrate. And are individually split along the groove.

Next, as shown in FIG. 5, the resistor 10 has a first bonding layer 31 of a Ni—Cr thin film provided on a side surface of the insulating substrate 1 for surface mounting on a circuit board S, and a Cu
A thin film second bonding layer 32 is provided. Then, a Cu film 7 having a thickness of 18 to 30 μm and Ni films 8 and 3 having a thickness of 3 to 7 μm are formed on the second bonding layer and the exposed resistor 5.
The solder coating 91 having a thickness of not less than μm is sequentially barrel-plated. Thus, the resistor 10 is completed.

The resistor 10 is used by connecting it to the circuit board S with solder 92. The Ni film 8 serves as a barrier layer that prevents the solder 92 from reacting with the Cu film 7 when the resistor 10 is soldered to the circuit board S. The heat generated by the resistor during use is quickly dissipated to the circuit board S through the high thermal conductivity Cu electrodes 41 and 43 and the Cu film 7. Therefore, the deterioration of the resistor is prevented in combination with the dispersion of the heat generating portion as described above. Conventionally, 1.25 mm × 2.
A resistor with a board size of 0 mm has a rated allowable power of 0.1
Although it was up to W, according to the configuration of this example, it is sufficiently allowable up to 0.25 W with the same substrate size.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A resistor having the structure shown in FIGS. 1 to 5, having a thickness of 0.4 mm on an insulating substrate 1 and a length in a current direction.
Ten pieces having a length of 0 mm and a length of 1.25 mm in a different direction were prepared. The thickness of the resistor 5 is 10 μm,
The thickness of 1, 42, 43 was 20 μm, and the thickness of the Cu film 7 was 10 μm.

A cycle of putting these ten resistors in a constant temperature layer at a temperature of 70 ° C., applying a rated DC voltage of 0.158 volts, energizing for 90 minutes, and disconnecting for 30 minutes was repeated.
The rate of change of the resistance value was measured. FIG. 7 is a graph showing the average of the measurement results over time. As is clear from the graph, the resistor of this example had almost no deterioration of the resistor.

[0020]

As described above, the chip resistor of the present invention has a low resistance and is excellent in heat dissipation as described above, so that even if power exceeding the rated allowable power of the conventional resistor of the same size is used, the resistance can be reduced. There is no deterioration. Therefore, for example, it is suitable for detecting a large current of a hard disk.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an intermediate body of a chip resistor according to an embodiment.

FIG. 2 is a plan view showing an intermediate body of the chip resistor according to the embodiment.

FIG. 3 is a plan view illustrating a method of adjusting the resistance value of the chip resistor according to the embodiment.

FIG. 4 is a plan view showing the chip resistor of the embodiment.

FIG. 5 is a cross-sectional view showing a state where the chip resistor of the embodiment is mounted on a circuit board.

FIG. 6 is a sectional view showing a conventional chip resistor.

FIG. 7 is a graph showing a measurement result of a resistance change rate of the chip resistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,101 Insulating substrate 21,22,31,32 Bonding layer 41,42,43 Electrode 5,105 Resistor 6,106 Protective film 7 High thermal conductive film 8,108 Ni film 91,92,109 Solder S Circuit board

Continuation of the front page (56) References JP-A-8-138902 (JP, A) JP-A-8-22903 (JP, A) JP-A-3-80501 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) H01C 7/00

Claims (6)

(57) [Claims] A chip resistor mounted and connected to a circuit board and producing a predetermined resistance value, comprising: an insulating substrate; a bonding layer formed on the insulating substrate in a thin film;
Together and a plated resistor on the bonding layer, a pair of electrodes are provided on both ends of the resistor, the pair
In the middle of the electrodes, the isolated island electrode contacts the resistor
Characterized in that the chip resistor is provided by a conductor having a lower resistance than the resistor. 2. The chip resistor according to claim 1, wherein the resistor is made of a nickel alloy such as nickel phosphorus Ni-P. 3. The chip according to claim 1, wherein the bonding layer extends to a connection portion with the circuit board, and the surface of the bonding layer at the connection portion is plated with a high thermal conductive film connected to a resistor. Resistor. 4. A bonding layer corresponding to the connection portion is made of a nickel chromium Ni—Cr alloy, and a first layer closely adhered to an insulating substrate and copper Cu or copper nickel Cu—Ni thereon.
And a second layer made of a copper alloy.
The chip resistor according to any one of the above. Wherein said pair of electrodes and the island electrodes, according to claim 1 is provided by plating before plating the resistor
A chip resistor according to claim 1. 6. The chip resistor according to claim 3, wherein the high thermal conductive film is made of copper Cu or a Cu alloy and is covered with a nickel Ni film.