JPS5816321B2 - Positive characteristic thermistor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive temperature coefficient thermistor device having an electrode that can be well adhered to a heat dissipating metal plate using a conductive adhesive.

PTC thermistor devices are widely used as self-regulating keepsakes, and methods for attaching PTC thermistor elements include spring pressure welding, soldering, and conductive adhesives.

This invention relates to an electrode for a positive temperature coefficient thermistor device using a conductive adhesive.

Generally, the electrodes of a positive temperature coefficient thermistor device are made by plating the entire surface of semiconductor porcelain with nickel using a nickel electrodeless plating method, and then heat-treating it at about 400° C. to obtain an ohmic contact nickel electrode.

However, in this case, since nickel is applied to the entire surface of the semiconductor porcelain, the outer peripheral surface of the semiconductor porcelain is ground off using a centerless grinder or the like, and a pair of electrodes are formed on both sides of the semiconductor porcelain to obtain a positive temperature coefficient thermistor element.

This positive temperature coefficient thermistor element is attached to the heat dissipation surface of the heat dissipation metal plate using a conductive adhesive.

FIG. 1 is a cross-sectional view of a conventional positive temperature coefficient thermistor device, in which a semiconductor ceramic 1 is electrolessly plated with nickel, and after heat treatment, the outer circumferential surface 1a of the semiconductor ceramic 1 is polished with a centerless grinder or the like to form a nickel electrode 213. A positive temperature coefficient thermistor element 4 is obtained.

A positive temperature coefficient thermistor device is constructed by adhesively fixing this positive temperature coefficient thermistor element 4 to a heat dissipating metal plate 5 with a conductive adhesive 6.

However, when the nickel electrode 3 of the PTC thermistor element 4 and the heat dissipating metal plate 5 are rubbed together so that no air bubbles remain between them, the conductive adhesive 6 is pushed out and the outer periphery of the PTC thermistor element 40 and the semiconductor porcelain 1 A nickel electrode 2 is attached to the surface 1a through a conductive adhesive 6 as shown in the figure.
and 3 may be shorted.

In order to eliminate such a short circuit accident, the thickness of the positive temperature coefficient thermistor element 40 and the semiconductor ceramic 1 may be increased accordingly, but this has the drawback that the positive temperature coefficient thermistor element 4 becomes large and expensive.

The present invention aims to provide a positive temperature coefficient thermistor device that eliminates the above-mentioned drawbacks.

That is, the present invention provides a configuration of the electrodes so that when a PTC thermistor element is adhesively fixed to a heat dissipating metal plate using a conductive adhesive, both electrodes of the PTC thermistor element are not short-circuited via the conductive adhesive. This is a positive temperature coefficient thermistor device with improved characteristics.

The invention will now be explained with reference to FIG.

FIG. 2 is a cross-sectional view of the positive temperature coefficient thermistor device of the present invention.
Electroless plating of nickel is applied to the semiconductor porcelain 11, and approximately 4
After heat treatment at 00°C, the electrode surface of only the circumferential end face 11a of one side of the semiconductor porcelain 110 is scraped off by sandblasting without polishing the outer peripheral surface of the semiconductor porcelain 11 to form asymmetrical nickel electrodes 12 and 13, thereby producing a positive temperature coefficient thermistor. A positive temperature coefficient thermistor device is constructed by bonding and fixing the positive temperature coefficient thermistor element 14 to a heat dissipating metal plate 15 with a conductive adhesive 16.

When bonding and fixing the PTC thermistor element 14 to the heat dissipating metal plate 15, the PTC thermistor element 140 and the semiconductor porcelain 11
If the nickel electrode 13 to which nickel adheres is adhered to the outer peripheral surface of the semiconductor ceramic 11, even if the conductive adhesive 16 adheres to the outer peripheral surface of the semiconductor ceramic 11, the positive temperature coefficient thermistor element can be bonded through the conductive adhesive 16. The nickel electrodes 12 and 13 of No. 14 will not cause a short circuit, thus eliminating the need for rework after bonding.

The distance between the nickel electrodes 12 and 13 is the same as that of the semiconductor porcelain 11.
The thickness is equal to or greater than that of

The positive temperature coefficient thermistor device described above uses a nickel electrode, but a two-layer electrode with silver added on top of nickel, which is commonly used, prevents deterioration of the electrode due to inrush current and is superior to the case of a nickel electrode. It is possible to obtain similar or better performance.

As shown above, the present invention provides a positive temperature coefficient thermistor device in which a nickel electrode or a nickel-silver electrode is provided in ohmic contact with a semiconductor porcelain by an electroless nickel plating method.

A positive temperature coefficient thermistor element is constructed by scraping an electrode along the circumferential end face of one side of the device to form a pair of asymmetrical electrodes, and the electrode is adhered to the outer peripheral surface of the semiconductor porcelain of the positive temperature coefficient thermistor element. This is a positive temperature coefficient thermistor device that is fixed to a heat dissipating metal plate using a conductive adhesive. There were cases where short-circuit phenomena occurred, which caused problems in terms of lifespan, but the positive temperature coefficient thermistor device of this invention maintains a constant gap between both electrodes even when using a conductive adhesive, and short-circuit phenomena do not occur during use. It is stable over a lifetime without causing any damage.

(b) Conventional positive temperature coefficient thermistor devices require a process of applying electroless plating to semiconductor porcelain, and polishing the outer peripheral surface of the semiconductor porcelain with a centerless grinder after heat treatment.
The positive temperature coefficient thermistor device of this invention requires electroless plating on semiconductor porcelain, and after heat treatment, a process of sandblasting one circumferential end surface of the semiconductor porcelain, and there is no difference in the number of steps between the two.

It has the following effects and has great industrial and practical value.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional PTC thermistor device, and FIG. 2 is a sectional view of a PTC thermistor device of the present invention. 11: Semiconductor porcelain, 11a Two semiconductor porcelain 110 circumferential end surfaces, 12, 13: Electrodes, 14: Positive temperature coefficient thermistor element, 1
5: Heat dissipation metal plate, 16: Conductive adhesive.

Claims (1)

[Claims] 1. In a positive temperature coefficient thermistor device in which a nickel-silver electrode is provided in ohmic contact with a nickel electrode by an electroless nickel plating method on semiconductor porcelain, one side of the semiconductor porcelain is scraped off along the circumferential end surface, and a pair of electrodes are removed. A positive temperature coefficient thermistor element is constructed by forming an asymmetrical electrode of the positive temperature coefficient thermistor element, and the electrode, which is resistant to adhering to the outer peripheral surface of the semiconductor ceramic of the positive temperature coefficient thermistor element, is adhesively fixed to a heat dissipating metal plate using a conductive adhesive. A positive characteristic thermistor device.