JPS58223303A - Positive temperature coefficient porcelain semiconductor 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 positive characteristic ceramic semiconductor device.

Conventionally, this type of semiconductor element has a structure in which ohmic electrodes made of, for example, Ni are provided on the front and back surfaces of the semiconductor, and a cover electrode made of, for example, AgM is provided on the surface of the ohmic electrode to cover the entire area thereof.

According to such conventional devices, when electricity is applied, a portion of the semiconductor between the ohmic electrodes generates heat, and this heat generation often causes the semiconductor to crack.

On the other hand, the purpose of cover electrodes is to reduce the contact resistance when a terminal is brought into contact with an ohmic electrode, as well as to protect it. Because its surface area is larger than that of an ohmic electrode, there is often an electrical gap between the cover electrodes. This causes a problem of short circuit.

Therefore, the present invention sets the relationship between the insulation distance between the cover electrodes on the front and back surfaces of the semiconductor, the distance between the outer edge of the ohmic electrode and the outer edge of the semiconductor, and the relationship between the thickness of the semiconductor within a range expressed by a predetermined formula. (2) The purpose is to solve the above-mentioned problems by doing so.

The present invention will be explained in detail below using specific examples. First, in Figures 1 and 2, the structure of the semiconductor element is described. 1 is a disk-shaped positive characteristic ceramic semiconductor, 2 is an ohmic electrode with a perfect circular plane, and is formed by electroless Ni plating. ing. Reference numeral 3 denotes a cover electrode having a perfect circular plane, which is formed by applying and baking Ag paste. This cover electrode 3 has a larger surface area than the ohmic electrode 2, and is designed to cover the entire surface of the ohmic electrode 2.

Next, in the embodiment shown in FIG. and the outer edge of the semiconductor 1 on the front and back surfaces of the semiconductor 10.
Experimental data when 1+'2 is shown in FIGS. 3 and 4.

Figure 3 shows how the cracking incidence rate of semiconductor l changes depending on the relationship between I4 and t, and (3) the condition is 12V direct/i! Using the I power supply, turn on the power for 1 minute,
ON-OF F that immediately stops power supply for 1 minute after 1 minute.
The cycle was run for 1000 hours at 1.-tal. As is clear from FIG. 3, the results show that there is a cracking occurrence rate when L/l exceeds 31, and there is no cracking occurrence rate, which is a completely extreme result.

Therefore, it can be seen that L/L≦3ms is good.

On the other hand, Fig. 4 shows -1-7!1. This shows how the insulation resistance between the cover electrodes changes depending on the relationship of βχt. Conditions LSI: 24 V DC power supply, 80 V
An insulator made of barium titanate was placed at a high temperature of 395°C to 95% RI-1 and high humidity, and the electrical insulation resistance between the cover electrodes was measured. In addition, since the electrical insulation resistance between the cover electrodes cannot be measured using the above semiconductor I,
The above insulator was used instead of the semiconductor 1. Therefore, in the figure, t is the thickness of this insulator, and the material of the cover electrode is Ag. Note that no ohmic electrode was formed in this experiment.

From Figure 4, l11+I! > When +4 is '1m++ or more, (4) the insulation resistance is as large as 100MΩ and is stable.

On the other hand, it can be seen that when 11+βλ+L is less than 2 mm, the insulation resistance decreases and electrical short circuit between the electrodes becomes more likely. Therefore, 7! i ten meters! The relationship of χ1t is 7!1
→-7! It can be seen that +t≧21 is better.

In the present invention, in the case of FIG. 5 in which the cover electrode 3 is offset from the axis of the semiconductor 1, 11 refers to the dimensions in FIG.
(Same thing for β2). Further, the semiconductor 1 may have a rectangular shape as shown in FIG. 6, and in this case, 41. p2 is as shown. The cover electrodes 3 may not be arranged symmetrically on the front and back surfaces of the semiconductor 1, but may be shifted from each other.

Furthermore, since the ohmic electrode 2 generates heat in the semiconductor portion sandwiched between the ohmic electrodes, the semiconductor 1
Provided in symmetrical positions on the front and back sides of the This Ohmi-7 electrode 2
Regarding the above, if the cover electrode 3 in FIGS. 5 and 6 is an ohmic electrode, its βx (j!>) becomes L.

The present invention is suitable for all kinds of heat generating devices, such as fuel atomization promoting devices for internal combustion engines, hot air generators, and resistors (5).

In summary, the present invention has great practical effects in that it can eliminate cracks in the semiconductor and prevent electrical short circuits between electrodes on the front and back covers of the semiconductor.

[Brief explanation of drawings]

Fig. 1 is a plan view showing one embodiment of the present invention, and Fig. 2 is a plan view showing an embodiment of the present invention.
3 and 4 are characteristic diagrams for explaining the present invention in detail, and FIGS. 5 and 6 are plan views showing other embodiments of the present invention. l...Semiconductor, 2...Ohmic electrode, 3...Cover electrode. Representative Patent Attorney Takashi Okabe (6) -11=

Claims (1)

[Claims] Ohmic electrodes are provided on the front and back surfaces of the PTC ceramic semiconductor element at positions facing each other, and a cover electrode having a larger surface area than the ohmic electrode is provided on the surface of the ohmic electrode. A PTC ceramic semiconductor device having a structure in which the entire surface of the ohmic electrode is covered, wherein the distance between the outer edge of the ohmic electrode and the outer edge of the semiconductor is 1. and when the thickness of the semiconductor is t, L/
The ohmic electrodes are provided at symmetrical positions on the front and back surfaces of the semiconductor so as to satisfy the relationship L≦3, and the distance between the outer edge of the cover electrode and the raised edge of the semiconductor is 11 on the front and back surfaces of the semiconductor. ．． A positive characteristic ceramic semiconductor element, wherein the cover electrode is provided on the surface of the ohm') electrode so as to satisfy the 1 law relationship of 1+ez→-t≧2vsvs when t is closed. (1)