JPS63153805A - Manufacture of voltage nonlinear resistance element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a voltage nonlinear resistance element using a sintered body containing titanium oxide (Ti(h)) as a main component.

Voltage nonlinear resistance elements are unique in that the resistance value changes nonlinearly depending on the applied voltage applied between the electrodes provided on the sintered body, and the resistance value rapidly decreases in the range where the applied voltage exceeds the varistor voltage. It has the following characteristics. Taking note of this characteristic, voltage nonlinear resistance elements are widely used as a means for noise prevention in small DC motors associated with audio equipment, protection of relay contacts, and discharge absorption in color TV cathode ray tube circuits.

Depending on the structure, shape, etc. of the equipment to which the voltage nonlinear resistance element is attached, the voltage nonlinear resistance element may be formed by attaching electrodes 2. 3, and a lead wire 4.5 is soldered onto the electrode 2.3, or as shown in FIGS. A common electrode 8 and divided electrodes 9a, 9b, and 9c are provided on both sides of a sintered body 7 formed in an annular shape with a common electrode 8 and divided electrodes 9a, 9b, and 9c, respectively.
, 9b, and 9c are electrically connected to a commutator piece or the like of a small DC motor through lead wires.

Incidentally, as conventional voltage nonlinear resistance elements, those based on tin oxide (Snow), iron oxide (Fezo3), silicon carbide (SiC), etc. are known.

Among these, the sintered body itself of the SnO type and Fe2O type is a linear resistor, and by adding a special electrode to it, a potential barrier is formed between the sintered body and the electrode. This gives it varistor characteristics. In addition, since SiC-based materials obtain varistor characteristics at the contact surfaces between SiC particles, any electrode is not particularly selected.

However, the conventional voltage nonlinear resistance element described above is
It involves manufacturing difficulties such as forming electrodes and molding sintered bodies, which increases the price, tends to cause deterioration of nonlinearity over time, and furthermore, the varistor voltage is high, making it difficult to use small DC for low voltage. It has drawbacks such as not being suitable for applications such as motor noise prevention.

In order to improve these conventional drawbacks, titanium oxide (Ti02) is the main component, and titanium oxide (Ti02) is sintered by adding small amounts of oxides of semiconductor elements (antimony, niobium, tantalum, etc.) and bismuth oxide. A system of voltage nonlinear resistance elements has been proposed.

In this titanium oxide-based voltage nonlinear resistance element, the sintered body itself exhibits excellent voltage nonlinearity as shown by curve Ll in Figure 3, and the varistor voltage is also low. As long as we focus on voltage nonlinearity, it is ideal for low-voltage applications such as noise prevention in small DC motors.

However, when the contact between the sintered body and the electrode becomes a non-ohmic contact, a rectification characteristic as shown in curve L2 in Fig. 3 occurs between the sintered body and the electrode, resulting in a non-linear voltage between the electrodes. The characteristics become blunt, such as a curve that is a combination of curve L2 and curve L2, resulting in a drawback that the excellent voltage nonlinearity of the sintered body itself, shown by curve L1, cannot be effectively utilized.

Therefore, the present invention provides a titanium oxide-based voltage nonlinear resistance element that can fully utilize the excellent varistor properties of the sintered body itself, has strong adhesive strength to the sintered body, is highly corrosion resistant, and has low material costs. It is an object of the present invention to provide a manufacturing method that allows a voltage nonlinear resistance element having an inexpensive electrode structure to be easily manufactured in a highly accurate pattern without damaging a sintered body.

In order to achieve the above object, the present invention provides a method for manufacturing a voltage nonlinear resistance element having an ohmic contact electrode mainly composed of nickel on a sintered body mainly composed of titanium oxide. a step of applying electroless plating containing nickel as a main component to substantially the entire surface of the electrode, a step of applying an etching resist to an electrode formation area on the surface of the electroless plating to specify an electrode pattern, and a step of applying the etching resist. The method is characterized by comprising a step of etching away electroless plating outside the region, a step of removing the etching resist, and a heat treatment step of converting the electroless plating remaining on the sintered body into an ohmic contact electrode. .

That is, the present invention provides a voltage nonlinear resistance element having the structure shown in FIGS. 1 and 2, for example, in which titanium oxide is the main component and oxides of semiconductor elements (antimony, niobium, tantalum, etc.) and If a normal electrode is applied to a sintered body containing a small amount of bismuth, the electrode will become a non-ohmic contact and the excellent varistor properties of the sintered body itself cannot be fully demonstrated, so an ohmic contact electrode is used as the electrode. This gives the sintered body its own excellent varistor properties.

The ohmic contact electrode may also be made of an In-Ga alloy. However, In-Ga alloy is very expensive and is not suitable for mass production. Furthermore, in order to attach the In-Ga alloy to the sintered body, rubbing or ultrasonic brazing must be performed, and the adhesion of the electrode to the sintered body is weak and accidents such as electrode peeling are likely to occur. Furthermore, the In--Ga alloy has a low melting point, which causes many problems when soldering lead wires.

Therefore, in the present invention, electroless plating is used to provide an ohmic contact electrode on a sintered body containing titanium oxide as a main component, and an ohmic contact electrode containing nickel as a main component is provided on the sintered body.

The nickel-based ohmic contact electrode
It is significantly cheaper than those made of N-Ga alloys and is highly suitable for mass production. Therefore, according to the present invention, the adhesion between the sintered body and the electrode is very strong, it is difficult to cause interfacial peeling of the electrode, and the deterioration over time is also small. Voltage nonlinear resistance elements can be manufactured.

Next, Fig. 4 (aI) to (a4) and (b+) to (b4
), a method for manufacturing a voltage nonlinear resistance element according to the present invention will be specifically described. This example is shown in Fig. 2(A).
, shows a specific example of obtaining a titanium oxide-based voltage nonlinear resistance element having the split electrode structure shown in (B), but it can be similarly applied to other shapes and structures. .

First, titanium oxide (Ti02) is the main component, and niobium oxide (Nb20s) and bismuth oxide (Bi20s) are added to it.
A composition to which a small amount of is added is baked at a temperature of 1380°C,
After creating an annular sintered body 7 having holes 6, as shown in FIG.
As shown in (a) and (bl), the entire surface of this sintered body 7 is electroless plated with nickel as the main component. For electroless plating of nickel, the sintered body is immersed in a tin chloride solution and a palladium chloride solution to form the electrode forming area 10a.
After activating ~10d, it is immersed in a plating solution consisting of nickel chloride, sodium hypophosphite, and sodium citrate, and electroless nickel-phosphorus plating is applied at a temperature of 80 to 90°C.

Next, as shown in FIGS. 4(a2) and 4(b2), etching resists lla to lid are applied to the electrode forming areas 10a to 10d on the surface of the electroless plating by means such as screen printing. Identify the electrode pattern. Broadcoat (trade name) is effective as the etching resists lla to lid.

Next, this sintered body 7 is immersed in an etching solution, and the electroless plating other than the areas coated with the etching resists lla to lid is etched away.

As an etching solution, acetic acid, nitric acid, and acetone are mixed in 1 part.
Using a mixture in the ratio of =1=1, etching is performed at a temperature of approximately 40°C. As a result, Fig. 4 (a,)
, (b), the electrode formation region 10 of the sintered body 7
a to 10d, electroless plating layers and etching resists lla to t, which become the electrode 8, divided electrodes 9a, 9b, and 9c;
tct is obtained.

Next, the etching resists lla to lid are removed using an alkaline solution or an organic solvent, and the etching resists lla to lid are removed using an alkaline solution or an organic solvent.
) and (b4), a sintered body 7 having electrodes 8 mainly composed of nickel and divided electrodes 98 to 9c on both sides is obtained. Next, by heat-treating this at a temperature of around 300° C., a voltage nonlinear resistance element having stable ohmic contact electrode 8 and divided electrodes 98 to 9c can be obtained.

Ohmic contact electrodes 8.9a to 9c thus obtained
has very strong adhesion to the sintered body 7 and excellent corrosion resistance. Furthermore, compared to those using In--Ga alloys, the cost of electrode materials is much lower and mass production is possible.

In addition, by applying electroless plating to almost the entire surface of the sintered body and then applying etching resist to the surface of the electroless plating to specify the electrode pattern, there is no possibility of damaging the base of the sintered body. do not have.

Furthermore, since the etching resist can be easily applied in a highly accurate pattern using a screen printing method or the like, even a complicated electrode pattern can be easily formed with high accuracy.

In addition, in order to obtain a stable ohmic contact electrode, it is necessary to provide an electrode consisting of 98 to 80% by weight of nickel and 2 to 20% by weight of phosphorus, but the composition ratio of nickel and phosphorus is determined by the plating solution. It is controlled by the hydrogen ion concentration (PI()), and in solutions above PHIO the proportion of phosphorus is 2% by weight.
Hereinafter, when the pH is below 2, the proportion of phosphorus is 20% by weight or more. Therefore, in order to obtain a good ohmic contact electrode, it is necessary to set the hydrogen ion concentration PH of the plating solution in the range of P)I-2 to 10.

As described above, the present invention provides a method for manufacturing a voltage nonlinear resistance element having an ohmic contact electrode mainly composed of nickel on a sintered body mainly composed of titanium oxide.
a step of applying electroless plating containing nickel as a main component to substantially the entire surface of the sintered body; a step of applying an etching resist to an electrode formation area on the surface of the electroless plating to specify an electrode pattern; It consists of a step of etching away the electroless plating in areas other than the area where the resist has been applied, a step of removing the etching resist, and a heat treatment step of converting the electroless plating remaining on the sintered body into an ohmic contact electrode. Because of this feature, the following effects can be obtained.

(a) The voltage nonlinearity of the sintered body itself can be fully utilized, and the adhesive force between the sintered body and the ohmic contact electrode is very strong, making it difficult for electrode peeling to occur. Furthermore, a voltage nonlinear resistance element having electrodes with excellent corrosion resistance and less deterioration over time can be manufactured with good mass productivity.

(b) After electroless plating is applied to almost the entire surface of the sintered body, an etching resist is applied to the surface of the electroless plating to specify the electrode pattern. will not damage.

(C) Since the etching resist can be easily applied in a highly accurate pattern by screen printing or the like, even a complicated electrode pattern can be easily formed with high accuracy.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the basic structure of a voltage nonlinear resistance element, Fig. 2 (A) and (B) are front and rear views of other examples, and Fig. 3 is a main component composed of titanium oxide. Figures 4 (ax) to (a4) are diagrams explaining the manufacturing method according to the present invention; Figure 4 (bl) ~
(b4) is (DI - DI
) to (D4-D4). F... Sintered body 8... Electrodes 9a, 9b, 9C... Divided electrodes Figure 1 Figure 2 (A) (8) Figure 3

Claims (1)

[Claims] (1) In a method for manufacturing a voltage nonlinear resistance element having an ohmic contact electrode mainly composed of nickel on a sintered body mainly composed of titanium oxide, substantially the entire surface of the sintered body is coated mainly with nickel. A step of applying electroless plating as a component, a step of applying an etching resist to the electrode formation area on the surface of the electroless plating to specify an electrode pattern, and etching the electroless plating other than the area where the etching resist is applied. manufacturing a voltage nonlinear resistance element, comprising a step of removing the etching resist, a step of removing the etching resist, and a heat treatment step of converting the electroless plating remaining on the sintered body into an ohmic contact electrode. Method.