JPH06310301A - Chip resistor - Google Patents

Abstract

PURPOSE:To make the allowable electric power of a resistor large so as to be capable of being mounted on an electric circuit to which large electric power is applied by a method wherein a resistor film is formed of tungsten. CONSTITUTION:A resistor paste obtained by adding and mixing a proper kinder and a proper solvent with tungsten powder is printed in advance so as to be coated on a ceramic green sheet to be used as an insulating substrate 1 by a screen printing method or the like. Then the ceramic green shut is fixed at a temperature of about 1600 deg.C and changed into the insulating substrate 1, a resistor film 2 which is composed of tungsten is simultaneously applied to, and formed on, the insulating substrate 1. Aluminum oxide or a material of the same quality as the insulating substrate 1 is added to the inside of the resistor film 2 within a range of 5 to 50wt.%. Thereby, the title resistor can be mounted on an electric circuit to which large electric power is applied.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in chip resistors.

[0002]

2. Description of the Related Art Conventionally, a chip resistor as an electronic component mounted on an electric circuit board generally has an insulating base made of an electrically insulating material such as an aluminum oxide sintered body, and a bottom surface via the side surface from the upper surface of the insulating base. Silver that has been deposited and distributed over
It is composed of a pair of electrodes made of a metal material such as silver-palladium, and a resistor film made of a resistance material such as ruthenium oxide deposited between the pair of electrodes on the upper surface of the insulating base. The pair of electrodes led out to the bottom surface are connected to a predetermined wiring conductor of the electric circuit board via a brazing material such as solder, and the resistor film is electrically connected to the wiring conductor to be mounted on the circuit board.

For the pair of electrodes, a metal paste obtained by adding and mixing an appropriate binder and a solvent to silver powder or silver-palladium powder is applied to the upper surface, side surface and bottom surface of the insulating substrate by a conventionally known screen printing method. By applying a predetermined pattern and a predetermined thickness by printing.
By baking at a temperature of 0 ° C., the insulating substrate is deposited from the upper surface to the side surface to the bottom surface.

Similarly to the pair of electrodes, for the resistor film, a resistor paste obtained by adding and mixing a ruthenium oxide powder with an appropriate binder and solvent is applied to the upper surface of the insulating substrate by a conventionally known screen printing method. By a predetermined pattern,
It is applied by printing to a predetermined thickness, and then baked at a temperature of about 850 ° C. to form a film between the pair of electrodes on the upper surface of the insulating substrate.

[0005]

However, since the ruthenium oxide used in this conventional chip resistor is a material having low withstand power, various electronic components of recent years are downsized and the mounting density on the electric circuit board is reduced. When the area of the resistor film is narrowed in order to reduce the overall shape in response to the increasing movement, the allowable power of the chip resistor is greatly reduced to 0.125 watts or less, and as a result, large power is applied. However, it has a drawback that it cannot be mounted on an electric circuit.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to provide a small chip resistor having a large allowable power and mountable in an electric circuit to which a large power is applied. It is in.

[0007]

According to the present invention, there is provided a chip resistor having a resistance film deposited on an upper surface of an insulating substrate, wherein the resistance film is made of tungsten. Is.

[0008]

In the chip resistor of the present invention, the resistor film is made of tungsten, which has a high withstand power, so that the chip resistor has a small overall shape, and the allowable power is 0. It can be set to a large value of 5 watts or more, and as a result, it can be mounted on an electric circuit to which a large amount of power is applied.

[0009]

The present invention will now be described in detail with reference to the accompanying examples.

FIG. 1 shows an embodiment of the chip resistor of the present invention, in which 1 is an insulating substrate and 2 is a resistor film. The insulating substrate 1 is a substantially rectangular flat plate made of an electrically insulating material such as an aluminum oxide sintered body. For example, when it is made of an aluminum oxide sintered body, it is suitable as a raw material powder such as alumina, silica, calcia, and magnesia. A wide area of ceramic green sheet (ceramic green sheet) is obtained by adding and mixing various binders and solvents to form a slurry and forming it into a sheet by the conventionally known doctor blade method or calender roll method. , High temperature (about 1600)
It is manufactured by firing at (° C.) to obtain a ceramic plate having a large area and dividing the ceramic plate having a large area into small sections which become the insulating substrate 1.

Further, the resistor film 2 deposited on the upper surface of the insulating substrate 1 is made of tungsten, and since the tungsten has high power resistance, even if the area of the resistor film 2 becomes small. The allowable power can be set to a high value of 0.5 watt or more, and as a result, it can be mounted on an electric circuit to which a large amount of power is applied.

The resistor film 2 made of tungsten is predetermined on the ceramic green sheet to be the insulating substrate 1 by a screen printing method, which is well known in the art, with a resistor paste obtained by mixing tungsten powder with an appropriate binder and a solvent. It is printed and applied to the thickness (2.0 to 20 μm),
When the ceramic green sheet is fired at a temperature of 1600 ° C. to form the insulating substrate 1, the ceramic green sheet is simultaneously deposited and formed on the upper surface of the insulating substrate 1.

If the resistor film 2 is formed by adding aluminum oxide or a material of the same quality as that of the insulating substrate 1, the resistor film 2 is formed when the resistor film 2 is formed on the insulating substrate 1. It can be firmly adhered to the upper surface of the insulating base 1. Therefore, it is preferable to add aluminum oxide or the same material as the insulating substrate 1 to the inside of the resistor film 2.

Further, when aluminum oxide or the same material as the insulating substrate 1 is added to the resistor film 2, if the amount of the added aluminum oxide or the same material as the insulating substrate 1 exceeds 50% by weight, the resistor film 2 is added. Of the chip resistor may be lost, and the function as a chip resistor may be lost. If it is less than 5% by weight, the effect of firmly depositing the resistor film 2 on the insulating substrate 1 is reduced. Therefore, when aluminum oxide or the same material as the insulating substrate 1 is added to the resistor film 2, the aluminum oxide or the insulating substrate 1 to be added is added.
It is preferable to set the amount of the same quality material as 5 to 50% by weight.

A pair of connection electrodes 3a, 3b for connecting to an electric circuit are formed on the upper surface of the insulating substrate 1 so as to be connected to both ends of the resistor film 2, and the pair of connection electrodes is formed. 3a and 3b are connected to the wiring conductor of the electric circuit board through a brazing material such as solder.

The pair of connection electrodes 3a and 3b are made of tungsten similarly to the resistor film 2, and a ceramic green sheet which becomes an insulating substrate 1 is a metal paste obtained by adding and mixing an appropriate binder and solvent to tungsten powder. By printing and coating in advance on a predetermined position on the upper surface, the upper surface of the insulating substrate 1 is adhered and formed so as to be connected to both ends of the resistor film 2.

When the same metal paste as the pair of connection electrodes 3a, 3b is used as the resistor paste for the resistor film 2, the resistor film 2 is formed on the ceramic green sheet as the insulating substrate 1. Since the resistor paste can be printed and applied at the same time when the resistor paste is applied by printing, it is preferable to use the same metal paste as the resistor 2 as the metal paste for the pair of connection electrodes 3a and 3b. .

The pair of connection electrodes 3a and 3b are coated on their surfaces with a metal having a good wettability with respect to a brazing material such as nickel, tin or silver.
When 3b is joined to the wiring conductor of the electric circuit board via a brazing material such as solder, the joining is extremely strong.

The metal such as nickel, tin, silver, etc. is formed on the surface of the connection electrodes 3a, 3b made of tungsten by a well-known electrolytic plating method, electroless plating method, or the like. Layered to a thickness of 0 μm.

Thus, according to the chip resistor of the present invention,
The connection electrodes 3a and 3b are connected to a predetermined wiring conductor of the electric circuit board via a brazing material such as solder, and the resistor film 2 is electrically connected to the wiring conductor to be mounted on an electric circuit.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the resistor film 2 is as shown in FIG. If the insulating film 1 is covered with an overcoat material 4 made of ceramics such as aluminum oxide or the like, glass, epoxy resin or the like, the resistor film 2 will come into contact with moisture contained in the atmosphere and the resistor film 2 will be exposed. It is possible to effectively prevent the occurrence of corrosion and the variation in the electric resistance value of the resistor 2. Therefore, the surface of the resistor film 2 is an overcoat material 4 made of ceramics, glass, resin or the like.
It is preferable to coat with.

The surface of the resistor 2 is overcoated 4
If a metal such as nickel, tin or silver is deposited on the surfaces of the connection electrodes 3a and 3b by an electrolytic plating method or an electroless plating method, a metal such as nickel, tin or silver is applied to the resistor 2 It is also possible to selectively adhere to the surfaces of the connection electrodes 3a and 3b without adhering to the surfaces thereof.

Further, if the overcoat material 4 is made of the same ceramic material as the insulating substrate 1, the ceramic green sheet which becomes the insulating substrate 1 has the resistor paste which becomes the resistor film 2 and the connecting electrodes 3a and 3b. When the metal paste and the ceramic paste to be the overcoat material 4 are sequentially applied by printing, and then baked at a high temperature of about 1600 ° C., the insulating substrate 1 has the resistor film 2, the connection electrodes 3a and 3b.
Since it is possible to simultaneously form the overcoat material 4 and the overcoat material 4, it is preferable that the overcoat material 4 is formed of the same material as the insulating substrate 1.

[0024]

According to the chip resistor of the present invention, since the resistor film is made of tungsten, which has a high withstand power, the chip resistor can be downsized in its entirety and the area of the resistor film can be reduced. The electric power can be set to a large value of 0.5 watt or more, and as a result, it can be mounted on an electric circuit to which a large electric power is applied.

[Brief description of drawings]

FIG. 1 is a perspective view showing an implementation of a chip resistor of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 1 ... Insulating substrate 2 ... Resistor film

Claims (2)

[Claims] 1. A chip resistor in which a resistor film is deposited on an upper surface of an insulating substrate, wherein the resistor film is formed of tungsten. 2. The chip resistor according to claim 1, wherein the resistor film made of tungsten contains 5 to 50% by weight of aluminum oxide or a composition having the same quality as the insulating substrate.