JPS6317502A - Ptc 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] [Object of the Invention] (Industrial Application Field) The present invention relates to a PTC resistor, and more specifically, a PTC resistor that has low electrical resistance during normal energization and has excellent thermal shock resistance. Regarding.

(Prior art) In recent years, BaTiO3 and BaTi0. Metal oxides, such as those containing small amounts of additives, have been used as ceramic PTC resistors. This B a T i O
The specific resistance of the S-based ceramic PTC resistor decreases from about 101 to 102 (0,1) to 10 Ω due to a rise in temperature.
It increases rapidly and is used as a thermistor. However, BaTiO3-based ceramic PTC resistors have specific resistances in the range of 101 to 10Ω, m).
Because it has TC characteristics, it has been difficult to use it in thermistors for overcurrent prevention, etc., which require PTC characteristics lower than the TC characteristics.

Therefore, ceramic P other than B a T i Oa group
The main component of the TC resistor is V2O, and Cr
.

V2O, ceramic PTC resistors containing small amounts of additives such as Afi have been considered. This v, 0° ceramic PTC resistor has a specific resistance of 104 (
Because it has an extremely low fluctuation range, rapidly increasing from about Ω, am) to about 1 (Ω, am), it is used in overcurrent prevention thermistors that require PTC characteristics with low resistivity. By the way, the following method has been considered as one way to take out the electrodes of this V2O-based PTC resistor. That is, the electrode and ■20. This is a method of brazing Ag with ceramics via an active element (for example, Ti, Zr, etc.) at the interface. By using this method, it is possible to obtain a good electrical bond, and a relatively good bond mechanically as well.

However, the above v20. The coefficient of thermal expansion of ceramic is 5~
8X10''' fideg-1 is smaller than metals such as Cu, so when these metals are used for electrodes, stress due to the difference in thermal expansion coefficient may cause Ag
During cooling after brazing or during temperature rise after completion of the device, cracks may occur at the electrode joints, electrodes may peel off, etc.

For this reason, V such as MO or W is used as an electrode material.
, O, A method of joining metals that exhibit a coefficient of thermal expansion unlike ceramics has been devised, and a stronger electrode has been obtained than when using Cu or the like.

e・ However, in V2O3 ceramic, its PTC
It is known that the lattice constant of the crystal changes as the resistance changes, and as a result, the thermal expansion of V, O, and ceramics causes discontinuous contraction or expansion. When the temperature of a PTC resistor using V2O3 ceramic increases rapidly, such as when a large current is applied, stress is generated at the electrode bonding surface due to this discontinuous dimensional change as the element operates. When a hard metal such as MoyW is used for the plate, if the thickness of the Ag solder layer is insufficient, this stress cannot be absorbed or relaxed, and the electrode may peel off.

(Problems to be Solved by the Invention) As mentioned above, in a PTC resistor in which a metal electrode is bonded to a V2O ceramic, due to the difference between the steady thermal expansion coefficients of V and O and the thermal expansion coefficient of the metal. Two types of electrode interfacial stress are generated: the interfacial stress caused by this, and the sudden interfacial stress caused by discontinuous contraction or expansion of V, O, during device operation, which creates a strong electrode bond to V2O1 ceramics. Conduct, electric.

In order to obtain a mechanically stable PTC resistor, it is necessary to prevent or alleviate the occurrence of these two interface stresses.

[Structure of the invention]

(Means for Solving the Problems) In view of the above problems, the inventors conducted intensive studies on the materials and configurations of electrodes to be bonded to V, O, and ceramics, and as a result, they came up with the following invention. .

That is, the present invention provides (Vx-xXx)gos (where 0
≦x≦0.02. X is Fe, Ni
, Co, Cu.

A PTC resistor in which Mo or W is attached as an electrode plate using Ag wax to a PTC resistor element containing 20% by weight or less of at least one kind of Sn and 20% by weight or less of at least one selected from W and Mo. Ag in the body
P characterized in that the wax layer has a thickness in the range of 0.01 to 2.0 m and also functions as a stress buffer layer.
A PT which is a TC resistor and whose stress buffer layer is 1/3 or less of the thickness of an electrode plate made of Mo or W.
It is a C resistor.

Here, X is V, O, or an additive that generates the PTC resistance characteristic of ceramic, and if X exceeds 0.02, the PTC resistance characteristic disappears. Also Fa.

At least one selected from Ni, Co, Cu, and Sn is V2O, an additive that improves the sinterability of ceramic,
If the amount added exceeds 20% by weight, the rate of change in resistance in the PTC resistance characteristics of the V2O3 ceramic decreases, which is undesirable.

Here, Fe, Co, and Ni are added to the V2O3 ceramic.

It is also effective to add at least one selected from Cu and Sn, and further add 20% by weight or less of at least one selected from Mo and W.

At least one selected from Mo and W has the effect of improving the sintered structure such as v and 0° ceramic grain size, improving the mechanical strength of the ceramic, and reducing discontinuous dimensional changes during device operation. If the amount added exceeds 20% by weight, this effect will not be achieved and the sinterability of the sintered body will also deteriorate, which is not desirable.

(effect) The thin stress buffering layer of the present invention is made of Ag wax.

Since its constituent material is made of a metal that is more flexible than Mo and W, ■, 0. It absorbs the sudden dimensional change when the PTC resistance of ceramics changes, thereby alleviating the stress generated at the electrode interface. In addition, its thickness is sufficiently thinner than that of the MO or W plate that is the electrode base, and
, Because it is firmly bonded to W, the thermal expansion at its surface, that is, the bonding interface with V203 ceramic, is
The base material is Mo.

■20.Shows the same behavior as W, such as when Cu or Ag is used alone as an electrode plate. Since it shows no difference in thermal expansion coefficient from ceramic, it does not generate thermal stress over a wide temperature range before and after the PTC resistance change. Therefore, the thickness of the Ag wax layer is 0.01 m.
~2.0 wm and M o .

The thickness must be 173 or less than the thickness of the W plate. If it is thinner than this, it will not be effective as a stress buffer layer, and if it is thicker than this, the coefficient of thermal expansion at the bonding interface with the V801 ceramic will decrease. v20. This is undesirable because the value is larger than that of ceramic, and furthermore, it forms a bimetal with the Mo and W plates, causing warping of the electrode and generating large interfacial stress.

(Example) The present invention will be described in detail below based on examples.

V, O, Cr, 03. SnO,, WO3 powder (vI
＋＋9S? Cra,,,,,)=o,+5%S
n (Cr content: approximately 0.3 mol %), and pulverized and mixed in a wet ball mill for 45 hours. The resulting mixture was heated at 600°C in a stream of H8 for 2 hours and then at 100°C.
After being reduced by holding at 0° C. for 3 hours, the mixture was pulverized by wet ball milling in acetone for 5 hours.

After drying, it was press-molded and sintered at 1350 to 1500°C for 4 hours to obtain a v203 ceramic sintered body with a size of 10φ×100.

This sintered body and a 1 m'' thick Mo plate were laminated using Ag brazing material containing 504 t of active metal as shown in FIG. 1, and vacuum brazing was performed to obtain a v203 PTC resistor.

This is referred to as Example 1, and further 100. Example 2 was obtained by laminating a brazing material as shown in FIG. 1 using a brazing material containing an active metal of "g".

Similarly, the thickness of the brazing material containing active metal was set to 300 μs, and Ag brazing material containing active metal was laminated in the configuration shown in Fig. 1.
Comparative example 1 using brazing material. Also, 1m+t Mo board and 1,
Comparative Example 2 was obtained in which a brazing material containing 0 m'' of active metal was used to form a laminated brazing material as shown in FIG.

Among these PTC resistors, Examples 1, 2, and 3 and Comparative Example 1 did not cause peeling or cracking of the electrode part even after cooling after bonding, but electrode peeling occurred at this point in Comparative Example 2. did.

The remaining PTC resistor was inserted into a short circuit with a current capacity of 200 OA, and 50 Hz half-wave current was applied to examine the impact resistance. As a result, in Examples 1 and 2.3, cracks in the electrode portion did not occur and electrode peeling was not generated and the electrodes were sound, but in Comparative Example 1, the PTC resistor was destroyed due to electrode peeling.

〔Effect of the invention〕

As described above, the stress buffer layer according to the present invention includes V and O.

This method relieves stress caused by dimensional changes accompanying changes in PTC resistance of ceramic, and provides a PTC resistor with excellent thermal shock resistance.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are cross-sectional views showing the configurations of an example of the present invention and a comparative example. 1... Mo board 2... Brazing material 3... v
203 Ceramic 4...Active metal brazing agent Patent attorney Yudo Ken Chika Kikuo Takehana Diagram 1 procedural amendment (method) 1. Indication of the case Patent Application No. 1983-1601118 2. Name of the invention PTC resistor 3. Relationship with the case of the person making the amendment Patent applicant (307) Toshiba Corporation 4, Agent 1-1 Shibaura-chome, Minato-ku, Tokyo 105 Toshiba Corporation Head Office September 30, 1986 ( Shipping date) 6. Subject to correction

Claims (1)

[Claims] (V_1_-_xX_x)_2O_3 (0≦x≦
0.02; In a PTC resistor with Mo or W attached as an electrode plate, the thickness of the Ag wax layer is 0.0
A PTC resistor having a thickness of 1 to 2.0 mm and less than 1/3 of the thickness of an electrode plate made of Mo or W.