JPS59111291A - Method of forming electrode of honeycomb heater - 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 Technical Field The present invention relates to a method for forming electrodes of a honeycomb heater for reinforcing electrode portions of a ceramic semiconductor sandwiched between power supply plates when constructing the honeycomb heater.

BACKGROUND ART Conventionally, when constructing a honeycomb heater, it has been known that a metal spraying method in which metal is sprayed at a high temperature is suitable for forming electrodes on a surface of a ceramic semiconductor having a large number of through holes. Publication No. 54-30133). However, with this metal spraying, the electrode surface is extremely rough, so when a power supply plate holding a ceramic semiconductor is brought into contact with the electrode surface, the contact resistance becomes large, and in devices such as honeycomb heaters that constantly carry a large current, the power supply is difficult. A localized high-temperature zone phenomenon occurs at the part that contacts the plate, causing electrode burning.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for forming electrodes of a honeycomb heater that reinforces the electrode surface in order to eliminate such drawbacks.

That is, in the electrode forming method according to the present invention, the surface portion of the electrode that contacts the power supply plate is made of silver or chromium.

It is coated with a highly conductive metal such as aluminum.

This will be explained below based on the illustrated embodiments.

The illustrated honeycomb heater has a ceramic semiconductor l formed in the shape of a disk, and electrodes 2a, 2b are formed on each side of the ceramic semiconductor l, which is provided with a large number of through holes located on both sides thereof.

This ceramic semiconductor 1 has electrodes 2a and 2b from both sides.
It is supported under pressure by a metal power supply plate 3.4 made of stainless steel or the like, which is arranged so as to be in contact with the power supply plate 3.4. These power supply plates 3 and 4 are arranged facing each other with an insulating space between them, and are made electrically conductive by fixing an electric wire connected to a power source to terminal boards 3a and 4a protruding from their side edges with screws. Further, these power supply plates 3 and 4 are provided with holes that allow ventilation through the ceramic semiconductor l, and the edges of the holes are in contact with the electrodes 2a and 2b on the peripheral surface of the ceramic semiconductor l. There is.

The electrodes 2a and 2b are formed of metal layers such as copper, zinc, and aluminum. To form this layer, a thermal spraying method is applied in which the metal is heated to a high temperature and sprayed, and the metal is heated to a temperature of 10° to 60°.
By performing oblique thermal spraying at a certain angle, it is possible to form a desirable electrode that does not adhere to the side surface of the through hole. This electrode 2a,
2b, a coating 5 made of highly conductive metal is formed on the portion that contacts the power supply plate 3.4. In the illustrated embodiment, a ring-shaped coating 5 is provided on the peripheral surface of the ceramic semiconductor l with which the aperture edge of the power supply plate 3.4 comes into contact. Highly conductive metals that form it include silver, chromium, aluminum, etc., and by screen printing it, the electrode 2
It can be formed as a surface coating of a, 2b. Further, the coating 5 may be provided only on the portion that contacts the power supply plates 3.4, or may be formed so as to protrude from the edges of the openings of the power supply plates 3, 4 by about 1 mm. ceramic semiconductor l
The electrodes 2a and 2b are formed by metal spraying, and the coating 5 is formed by screen printing, followed by baking. The baking process is carried out at a temperature that does not oxidize the metal forming the electrodes 2a, 2b and the coating 5, specifically, 450'O to 600'O.
It is sufficient to heat for about 10 minutes at a temperature of 0'0. By performing this baking/single treatment, it is possible to not only improve the adhesion strength of the coating 5, but also to improve the adhesion strength of the sprayed electrodes 2a and 2b to the ceramic semiconductor 1, and to reduce the specific resistance by half. can.

In the honeycomb heater configured like this, the power supply plate 3.4
The voltage supplied to the electrodes 2a,
2b can be energized. Since the metal coating 5 is made of a metal with good conductivity, the contact resistance with the power supply plates 3.4 can be reduced to several tenths, and the contact area of the power supply plates 3, 4 can be reduced. Even if the amount is reduced, good conductivity can be maintained, so a large ventilation area can be obtained. Note that the power supply plate 3.4 can be attached to the insulating base frame 6 while holding the ceramic semiconductor weight therebetween. This insulating base frame 6 can be made of heat-resistant resin, and the bending wind 3b of the power supply plate 3 is inserted into the slit 7) 8a provided on the plate surface and engaged with the protrusion 6b in the slit Ba. By stopping them, the power supply plates 3, 4 and the ceramic semiconductor 1 can be fixedly attached.

Effects of the Invention As described above, according to the method of forming an electrode according to the present invention, since a highly conductive metal coating is interposed in the part of the sprayed electrode that contacts the power supply plate, the contact resistance with the electrode is reduced. This makes it possible to maintain good conductivity and prevent burnout of the ceramic semiconductor.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a honeycomb heater to which the electrode forming method according to the present invention is applied, Fig. 2 is a sectional view showing a semiconductor portion of the honeycomb heater to which the same method is applied, and Fig. 3 is a part of the semiconductor portion. It is an enlarged sectional view. l Two-handed conductor, 2a, 2b: electrode, 3, 4: power supply plate, 5:
Metal coating with good conductivity.

Claims (2)

[Claims] (1) By forming electrodes by spraying metal on a surface of semiconductor porcelain that has many through holes, and sandwiching the electrode surface of the semiconductor porcelain between the perforated edges of opposing power supply plates, \\In constructing the Nicum heater. A method for forming an electrode for a nicham heater, characterized in that at least the surface portion of the electrode that contacts the power supply plate is coated with a highly conductive metal such as silver, chromium, or aluminum. (2) The method according to claim 1, wherein after the highly conductive metal is attached by screen printing, the electrode is burnt at a temperature that does not oxidize the metal.・Method for forming electrodes of Nikum heater.