JPH0414202A - V2o3 base ceramic resistor element - Google Patents

Abstract

PURPOSE:To enable the hysteresis and the cracking due to thermal shock to be restrained by mixing a ceramic with a resin. CONSTITUTION:The title V2O3 base ceramic resistor element comprising a ceramic displaying the PTC characteristics mixed with a resin can relieve the thermal stress during Mott's scattering process of the resin contained in the porous part of the ceramic so that the cracking may be avoided to enhance the thermal shock resistance. Furthermore, since the thermal stress can be relieved easily and evenly by the existence of the resin, the metal transition phenomenon can be made even thereby enabling the hysteresis to be reduced notably. Consequently, the title element can be used as a control element of high current and power.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is based on ■, 0. PTC whose main component is ceramics
Regarding resistor elements, especially by suppressing the occurrence of hysteresis crank, large currents can be achieved.

V2O that can be used as a limiting element for large voltages
, concerning the structure of a system resistor element.

(Prior art) V2O-based semiconductor ceramics, which are generally used in resistor elements with positive resistance temperature characteristics (PTC), utilize the so-called Motto transition, which transitions from a conductor to an insulator at a certain temperature. It is.

Although this V'tOz-based resistor element has a rate of change in PTC characteristics that is about two orders of magnitude lower than that of the BaTi0z-based one, it has a small specific resistance of about 10 Ω1, so it has a large current density and a large i
It is expected to be used as an overcurrent protection device for high current and high power applications.

[Problem that the invention seeks to solve]

However, when measuring the PTC characteristics of the conventional V2O3 ceramic resistor element described above, there is a problem in that the hysteresis phenomenon, so-called hysteresis, is large, in which different resistance characteristic curves are drawn for the outward path when the temperature rises and the return path when the temperature falls.

This hysteresis is the difference between the temperature indicating the reference resistance value when the temperature rises in an overcurrent state and the temperature when the temperature returns to the reference resistance value after being released and cooled. For example, as shown in the hysteresis characteristic shown in the figure, 172 of the logarithm of the resistance of the PTC curve a during temperature rise is set as the half resistance value C (reference resistance value).
As, for the temperature that shows the half resistance value C when the temperature rises,
The temperature at which the equivalent resistance C occurs on PTC curve b during cooling is approximately 3
The temperature decreases by as much as 0°C, and as described above, the hysteresis of conventional V, ○ type resistor elements reaches a maximum of 20 to 30°C.

In addition, the conventional V2O ceramic resistor element described above has the following characteristics:
When the temperature rises rapidly due to self-heating, the temperature distribution within the element becomes non-uniform, and the temperature difference tends to cause cracks, leading to problems such as low thermal shock resistance. For this reason, there are significant practical restrictions in employing the conventional V2O type resistor element as a limiting element for large currents and large voltages, and improvements in this are required.

An object of the present invention is to provide a VtOs-based ceramic resistor element that can be used as an overcurrent protection element by suppressing the occurrence of cracks due to the above-mentioned hysteresis and thermal shock.

[Means for solving problems]

The inventors of the present invention conducted repeated studies to suppress the above-mentioned hysteresis and cracking, and found that since the structure of VtOs ceramics is porous, the metal transition phenomenon becomes uneven when the temperature rises or falls. Moreover, it has been found that thermal stress during the transition increases, resulting in increased hysteresis, making cracks more likely to occur.

From this result, we came up with the idea that by mixing a resin with the VtOs ceramics and curing it, it is possible to make the metal-insulator transition phenomenon uniform and reduce cranking, and we have completed the present invention.

Therefore, the present invention is characterized in that, in a resistor element made of V2O-based ceramics, a resin is mixed with ceramics that exhibit PTC characteristics.

Here, it is preferable to employ a thermosetting resin as the resin, and the amount added thereof may be appropriately set to such an extent that it does not affect the resistance temperature characteristics.

Further, the present invention can be applied to both a laminated type in which ceramic layers and internal electrodes are alternately laminated, and a single plate type.

[Effect]

According to the V8O ceramic resistor element of the present invention, since a resin is mixed with the ceramic exhibiting PTC characteristics, the thermal stress at the time of Mott transition is alleviated by the resin present in the porous portion of the ceramic. , it is possible to prevent the occurrence of cracks and improve thermal shock resistance. Moreover, since the presence of the resin facilitates thermal stress relaxation to proceed uniformly, the metal transition phenomenon can be made uniform, and hysteresis can be significantly reduced. As a result, it can be used as a limiting element for large currents and large powers, meeting the above requirements.

〔Example〕

The present invention will be explained in detail below.

First, a manufacturing method for obtaining a VtOs ceramic resistor element according to an embodiment of the present invention will be described.

■ First, V20299. Omo1%, Cr, 0.1゜0go1%, Sbg 03 , B It Os , P
One or more types of bsOs are blended, toluene is added as a solvent, and the mixture is ground in a ball mill for about 24 hours to obtain ceramic raw material powder.

(2) Next, after removing the solvent and drying the ceramic raw material powder, it is fired in an ArHt atmosphere at 1000°C for 4 hours, and then in an H2 atmosphere at 1500°C for 5 hours.

(2) After the above firing, toluene is added as a solvent again, and the mixture is pulverized in a ball mill for about 24 hours, followed by removal of the solvent and drying to obtain a ceramic powder.

(2) Next, 10 g of methacrylate resin is added to 90 g of the above ceramic powder and mixed, followed by pressurization and heat molding in a press to obtain a disc-shaped sintered body.

■ After that, Ag or Ag-P is applied to both sides of the sintered body.
After printing the conductive paste consisting of d, it is baked to form an electrode film. In this way, the single-plate resistor element of this example is manufactured.

Next, the effects of this embodiment will be explained.

■20 of this example. According to the series ceramic resistor element,
Since a resin is added to and mixed with the ceramic powder, and the mixture is pressurized and heated, the resin relieves the thermal stress during metal transition, thereby preventing the occurrence of cranks and improving the thermal shock resistance accordingly.

Moreover, since the presence of the resin facilitates thermal stress relaxation to proceed uniformly, hysteresis when the temperature rises and falls can be reduced, and as a result, it can be used as a limiting element for large currents and large voltages.

The table shows the results of characteristic tests conducted to confirm the effects of this example.

In this test, V
O0. A ceramic resistor element was employed, and the resistivity (Ωai), PTC magnification (%), and hysteresis ('C) of this resistor element were measured. For comparison, similar measurements were also performed on a conventional sample in which no resin was mixed.

In the table, Nal, 3. 5 is the sample of this example, FkL2
．． 4°6 shows a conventional sample.

As is clear from the table, all of the conventional samples in which no resin was mixed had a hysteresis temperature difference of 10 to 15°C, which was insufficient as an overcurrent limiting element. On the other hand, all of the samples of this example had a hysteresis of 8 to 8.
The temperature difference is 5°C, which shows that the temperature difference has become significantly smaller.

In addition, in terms of resistivity, compared to the 2-4 ohm mouth of the conventional sample, the sample of this example has almost the same characteristics as the 2-3 ohm country. Furthermore, the PTC magnification is 70
-100%, the sample of this example has a larger value of 90-120%.

〔Effect of the invention〕

As described above, according to the V2O3 ceramic resistor element according to the present invention, since resin is mixed into the ceramic, thermal stress at the time of moft transition can be alleviated, cracking can be prevented, and thermal shock resistance can be improved. This has the effect of significantly reducing hysteresis and allowing it to be used as a limiting element for large currents and large powers.

4,

[Brief explanation of the drawing]

The figure shows the conventional V2 Hysteresis of system resistor elements FIG.

Claims (1)

[Claims] (1) A V_2O_3-based ceramic resistor element comprising a V_2O_3-based ceramic having resistance-temperature characteristics that transforms from a conductor to an insulator at a predetermined temperature, the V_2O_3-based ceramic resistor element being characterized in that a resin is mixed with the ceramic.