JPH10208913A - Formation of thick film resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make even distribution components in screen-printed thick-film resistor paste by drying and baking the paste by giving ultrasonic vibrations to the paste after the paste is screen-printed on an insulating substrate. SOLUTION: Thick-film resistor paste 2 composed of conductive particles, insulating particles, a resin, and an organic solvent is screen-printed on an alumina substrate 1 on which electrodes 9 are formed. After the screen printing, the substrate 1 is supported by a stainless steel net 5 in an ultrasonic cleaning device 3 containing water 4 so that the lower surface of the substrate 1 may be dipped in the water 4 while the paste 2 has fluidity and ultrasonic vibrations are applied to the substrate 1. Then the paste 2 is dried by passing the substrate 1 through a drying furnace belt and a thick film resistor is finally formed by baking the paste 2 in a baking furnace belt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a resistor component such as a chip resistor or a collective resistor.
The present invention relates to a method for forming a thick film resistor.

[0002]

2. Description of the Related Art Conventionally, in the manufacturing process of a resistor component such as a chip resistor or a collective resistor, a method of screen printing a thick film resistor paste is widely used. In this method, Ag or a conductive paste of Ag and Pd is screen-printed and fired on an insulating substrate including an insulating ceramic substrate such as an alumina substrate to provide electrodes. Next, a thick film resistor paste is screen-printed on the insulating substrate, dried, and fired to form a thick film resistor.

The distribution of the resistance value of the thick film resistor is wide and cannot be used as a resistor part. Therefore, a cut is made in the thick-film resistor by laser light called laser trimming, the resistance value is increased, and the distribution of the resistance value is corrected within a predetermined resistance value range.

[0004]

In general, a thick film resistor paste comprises a solid component such as conductive particles and insulating particles, and a component called a vehicle comprising a resin and an organic solvent. The screen-printed thick film resistor paste volatilizes the organic solvent in the drying process, and solid components are fixed on the insulating substrate by the resin. In the subsequent firing step, the resin decomposes and burns, leaving only the solid components. The solid component is sintered or melted and solidified to form a thick film resistor.

The more uniform the internal structure of the thick film resistor, the narrower the distribution of the resistance of the thick film resistor and the better the electrical characteristics of the thick film resistor. For this reason, thick film resistor pastes are carefully manufactured so that the solid components are evenly dispersed in the vehicle. However, in order to form a thick-film resistor having a narrow distribution of resistance values, it is important that this uniformly dispersed state is maintained even after screen printing on an insulating substrate.

However, a screen widely used for screen printing of a thick film resistor paste is made of a mesh constituted by stainless steel or nylon wires and an emulsion covering a portion other than a printing pattern of the mesh.

In screen printing, a thick film resistor paste is applied to an insulating substrate through a gap between wires of a mesh in a portion where there is no emulsion. For this reason, the thick film resistor paste is not directly applied to the portion where the mesh wire contacts the printed pattern of the insulating substrate. The thick film resistor paste applied through the gaps between the mesh wires flows by leveling into a portion of the insulating substrate where the mesh wires are in contact with the printed pattern, and the thick film resistor paste is applied to the entire printed pattern.

The thick film resistor paste flowing into the portion where the mesh wire contacts the printed pattern of the insulating substrate due to leveling has a phenomenon that the amount of the vehicle component is large and the solid component is easily reduced. This phenomenon is particularly likely to occur in a thick film resistor paste containing a large amount of an organic solvent. For this reason, in the screen-printed thick film resistor paste, there are a portion having a large amount of the vehicle component and a small amount of the solid component, and a portion having a small amount of the vehicle component and a large amount of the solid component, and are locally nonuniform. The non-uniformity of the components of this screen-printed thick film resistor paste is not completely uniform even after firing, and causes a wide distribution of the resistance value of the thick film resistor after firing and a cause of deterioration of electrical characteristics. Becomes

Laser trimming also deteriorates the electrical characteristics of the thick-film resistor. The larger the trimming ratio, which is the ratio between the target resistance value after laser trimming and the fired resistance value, the greater the degree of deterioration. There is a possibility that the reliability as a component may be impaired. If importance is placed on the reliability as a resistor part and a thick film resistor having a large trimming rate among the thick film resistors after firing is discarded, productivity and economic efficiency deteriorate.

Therefore, the components of the screen-printed thick film resistor paste are uniform, the resistance of the thick film resistor after firing is close to the target resistance after laser trimming, and the distribution of the resistance is narrow. desired.

According to the method of the present invention, the non-uniform component in the thick film resistor paste after screen printing is made uniform,
The purpose of the present invention is to narrow the distribution of the resistance value of a thick film resistor after firing, to improve the reliability of resistor components such as chip resistors and collective resistors, and to improve the productivity of the resistor components. With the goal.

[0012]

In order to solve the above-mentioned problems, according to the method of the present invention, a thick film resistor paste is screen-printed on an insulating substrate, followed by applying ultrasonic vibration, drying and firing. The step of applying ultrasonic vibration before the drying and firing steps, which is a feature of the method of the present invention, makes the components in the thick-film resistance paste after screen printing uniform, and as a result, the thick-film resistance after firing. The internal structure of the body becomes uniform. A thick-film resistor having a uniform internal structure has a uniform resistance value at any portion inside, and the distribution of the resistance value of the thick-film resistor is narrow.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, an ultrasonic vibration is applied to a thick-film resistance paste after screen printing for the purpose of equalizing non-uniform components of the thick-film resistance paste after screen printing. . Ultrasonic vibration is used to disperse a solid phase such as powder into a liquid phase, or to be used in ultrasonic cleaning, etc. Again, the components before screen printing are in a uniform state.

The method of applying vibration by ultrasonic waves is, for example, a method in which water is placed on an ultrasonic cleaner, a net or a belt is placed so as to be in contact with the water surface, and an insulating substrate on which a thick film resistor paste is screen-printed is placed. Fill the ultrasonic cleaner with water,
There is a method in which a sponge is placed in water so that the upper surface of the sponge comes out of the water surface, and an insulating substrate on which a thick film resistor paste is screen-printed is placed on the upper surface of the sponge.

The time for applying ultrasonic vibration is 100
When a W ultrasonic cleaner is used, it is sufficiently effective to vibrate for 10 seconds.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a method of applying an ultrasonic vibration to a screen-printed insulating substrate according to the method of the present invention. FIG. 2A is a cross-sectional view of the screen printed insulating substrate. FIG. 2B is a cross-sectional view of the insulating substrate after leveling. FIG. 2C is a cross-sectional view of the insulating substrate after being subjected to ultrasonic vibration.

A conductor paste of Ag and Pd is screen-printed and baked in advance, and a thick-film resistor paste 2 is applied to the electrodes 9 and 9 on the 96% alumina substrate 1 on which the electrodes 9 are formed.
The screen printing was performed so that the distance between the thick film resistors was 1.0 mm and the width of the thick film resistor was 1.0 mm. The screen printing was performed on a stainless steel screen 7 having a wire diameter of 30 μm, a 250 mesh, and an emulsion 8 having a thickness of 10 μm.
The thick film resistor paste 2 includes a commercially available thick film resistor paste having a nominal sheet resistance of 100Ω and a nominal sheet resistance of 10Ω.
Two types of 0 kΩ thick film resistor paste were used. FIG.
According to (a), screen printed alumina substrate 1
The upper thick film resistor paste 2 is cut into small pieces through the gaps between the wires of the screen 7. According to FIG. 2B after leveling, the thick film resistor paste 2 on the alumina substrate 1
A portion 2a having a large amount of the vehicle component and a small amount of the solid component and a portion 2b having a small amount of the vehicle component and a large amount of the solid component are formed.

Next, while the fluidity of the thick film resistor paste 2 remains, the alumina substrate 1 is filled with water 4 in a 100 W ultrasonic cleaner 3 so that the lower surface of the alumina substrate 1 It was supported by a stainless steel net 5 so as to be immersed, and vibration by ultrasonic waves was applied. The time to apply vibration is 10 seconds,
Three conditions of 60 seconds and 300 seconds were set. According to FIG. 2C after the application of the ultrasonic vibration, a thick film resistor paste 2 having uniform components on the alumina substrate 1 can be obtained.

After applying ultrasonic vibration, the alumina substrate 1 was passed through a belt drying furnace having a peak temperature of 150 ° C. and a peak time of 5 minutes to dry the thick film resistor paste 2. Then, finally, firing was performed in a belt firing furnace at a peak temperature of 850 ° C. and a peak time of 9 minutes to form a thick film resistor.

A thick film resistor paste having a nominal area resistance value of 100Ω and a thick film resistor paste having a nominal area resistance value of 100 kΩ are made into 50 thick film resistors for each of the three conditions of ultrasonic vibration time, The measured resistance value and the distribution of the resistance value were evaluated. The distribution of the resistance value was evaluated by a value called a coefficient of variation. The variation coefficient is a value obtained by dividing the standard deviation of the resistance value by the average value. The smaller the value of the variation coefficient, the narrower the distribution of the resistance value.

Table 1 shows the average value and the coefficient of variation of the resistance values of Examples 1, 2, and 3 using a commercially available thick film resistor paste having a nominal area resistance of 100 Ω. Table 2 shows the average values of the resistance values and the values of the coefficient of variation of Examples 5, 6, and 7 using the commercially available thick film resistor paste. For comparison, Tables 1 and 2 also show the average value and the coefficient of variation of the resistance values of Comparative Examples 4 and 8, which were dried and fired without applying ultrasonic vibration. Note that the comparative example also has 50 samples.

[0023]

[Table 1]

[0024]

[Table 2]

As can be seen from Tables 1 and 2, the thick film resistors of Examples 1, 2, 3, 5, 6, and 7, which were subjected to ultrasonic vibration after screen printing, dried and fired, The coefficient of variation of the resistance value is smaller and the resistance value distribution is narrower than the thick film resistors of Comparative Examples 4 and 8 to which no vibration is applied. In particular, in the case of a thick film resistor paste having a small nominal sheet resistance, the effect of the vibration by the ultrasonic wave is large.

[0026]

According to the method of the present invention, the distribution of the resistance of the thick film resistor after firing can be narrowed, and the reliability of the resistor component using this thick film resistor can be improved. further,
The productivity of resistor parts can be improved.

The method of the present invention can be applied to not only a thick film resistor paste but also an electrode paste. In particular, the internal electrodes and the like of the multilayer ceramic capacitor need to be thin and the film must be fired uniformly, and the method of the present invention is effective.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a method of applying an ultrasonic vibration to a screen-printed insulating substrate according to the method of the present invention.

FIG. 2A is a cross-sectional view of a screen printed insulating substrate. FIG. 2B is a cross-sectional view of the insulating substrate after leveling. FIG. 2C is a cross-sectional view of the insulating substrate after being subjected to ultrasonic vibration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Thick film resistor paste 3 Ultrasonic cleaner 4 Water 5 Net 6 Ultrasonic oscillator 7 Screen 8 Emulsion 9 Electrode

Claims (2)

[Claims] 1. A method for forming a thick-film resistor on a substrate, comprising the following steps. (A) A first step of screen-printing a thick film resistor paste composed of conductive particles, insulating particles, resin and an organic solvent on a substrate. (B) A second step of applying ultrasonic vibration to the substrate. (C) a third step of drying the substrate. (D) A fourth step of firing the substrate. 2. A method for forming an electrode on a substrate, comprising the following steps. (A) A first step of screen-printing a conductive paste comprising conductive particles, a resin, and an organic solvent on a substrate. (B) A second step of applying ultrasonic vibration to the substrate. (C) a third step of drying the substrate. (D) A fourth step of firing the substrate.