JP3522092B2 - Method for producing polymer PTC element - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing a PTC element using a thermoplastic polymer.

[0002]

2. Description of the Related Art A polymer PTC element having a positive resistance-temperature characteristic is known in which a member obtained by dispersing and mixing a conductive substance in a polymer is used as an element body and its resistance rapidly increases when the temperature is raised to a certain temperature. There is.

As shown in FIG. 2 (A), this polymer PTC element has a structure in which electrodes 2 are fixed to both surfaces of an element body 1. As a method for producing this polymer PTC element, a polymer and a conductive substance are dispersed and mixed to be formed into a plate shape such as a long plate shape, and a metal plate as an electrode member is thermocompression bonded to both surfaces thereof, or a metal plate is formed. Instead of the above, a method is known in which electrodes are formed on both surfaces of the element body 1 by electroless plating and electroplating to form a material, and the material on which the electrodes are formed is punched into a specific shape to form a polymer PTC element. There is.

[0004]

However, in order to obtain a specific shape of a plate-shaped material, the polymer PT is punched out.
In the method of manufacturing the C element, as shown in FIG.
There is a problem that the heat-bonded electrode 2 peels off at the end of the element as indicated by 9 due to the stress applied to the end during punching. As described above, when the electrode 2 peels off at the end of the element, the initial resistance value varies, and the intermittent load is applied to increase the resistance value, and the resistance value also increases due to thermal aging or thermal shock. There was a problem to do.

As another method for producing a polymer PTC element, there is known a method in which a joint surface of either the electrode 2 or the element body 1 made of a metal plate is formed into a rough surface and thermocompression bonding is performed by hot pressing or the like. However, even with this method, the problem of peeling of the electrode 2 at the element end portion at the time of punching a plate-shaped material with an electrode cannot be solved, and there remains a problem that there is a large variation in the initial resistance value.

In view of the above problems, the present invention provides a polymer P
To provide a method for producing a polymer PTC element capable of eliminating peeling of an electrode at an end portion of a TC element, thereby reducing an increase or variation in initial resistance value and an increase in resistance value due to thermal aging or thermal shock. To aim.

[0007]

In order to achieve this object, a method for producing a polymer PTC element according to the present invention has a plate-like shape made of a thermoplastic polymer and a composition in which a conductive substance is dispersed and mixed in the polymer. Electrodes are formed on the front and back surfaces of an element body having a positive resistance temperature characteristic by a metal plate or plating to make a material, and the material is punched into a predetermined element shape, and the punched material is hot pressed to form an element body. It is characterized in that the electrodes are thermocompression bonded (Claim 1).

In the method for producing a polymer PTC element according to the present invention, preferably, the hot press-compression bonding conditions are: press pressure: 25.5 kgf / cm ^{2 to} 63.5 kgf /
cm ² , temperature: 150 ° C to 300 ° C, holding time: 5 minutes to
20 minutes (claim 2).

[0009]

In the present invention, the polymer PTC element is punched into a predetermined shape and then the electrode is thermocompression-bonded to the element body by hot pressing again. This heating softens the resin to some extent, and the electrode at the end of the element is punched out. Even if any deformation occurs, it is corrected to a flat surface, so even if peeling occurs between the element body and the electrode, the electrode will re-adhere to the element body and the edge peeling will be repaired. To be done.

[0010]

FIG. 1 shows a polymer PT according to the invention.
It is a flowchart showing an example of a manufacturing method of a C element. Reference numeral 3 is a long plate shape in which an electrode 2 is formed on the front and back surfaces of an element body 1 in which a conductive substance is dispersed and mixed in a thermoplastic polymer, by heat-bonding or plating (electroless plating after electroless plating) of a metal plate. It is a material that is formed into an equal plate. As the polymer, for example, a thermoplastic resin such as polyvinylidene fluoride or polyethylene is used. Further, carbon black, tungsten carbide or the like is used as the conductive material. Further, as the electrode 2, copper or nickel is used when using a metal plate, and tin plating, nickel plating, or the like is used when using plating. The polymers, conductive materials and electrodes used in the present invention are not limited to the above examples.

A chip-shaped polymer PTC element 7 is obtained by punching the long plate-shaped material 3 thus formed into a predetermined shape and size such as a circle or a polygon by a punching device 4. Thereafter, the polymer PTC element 7 is heated by the hot press device 5 including the upper device 5a and the lower device 5b.
And press from above and below. It should be noted that smoothed press plates 6a and 6b are respectively provided on the upper and lower pressing surfaces of the hot pressing device 5 which face each other, and the thermocompression bonding work is performed. By performing this thermocompression bonding work, a polymer PTC element 8 in which peeling of the end portion of the polymer PTC element 7 is eliminated is obtained.

In order to confirm the effect of the present invention, polyvinylidene fluoride is used as the polymer, tungsten carbide is used as the conductive material, and nickel formed by electroless and electrolytic plating is used as the electrode 2. 10 mm, the thickness of the body 1 is 0.24 mm,
The thickness of the electrode 2 is 0.03 mm, and the hot pressing conditions (pressing pressure, temperature, holding time) are variously changed, and the initial resistance value, the resistance variation (R value) and the heat shock cycle test (temperature atmosphere of −40 ° C. Left for 30 minutes, +85
A test in which the test piece was left standing for 30 minutes in a temperature atmosphere of ° C.) The change in resistance value was evaluated 500 times. The results are shown in Table 1. Ten samples were tested and measured for each sample, and the R value indicating the variation in resistance was calculated by the following calculation. _R = R _nMAX -R nMIN (provided that R _nMAX, R _Nmin is the maximum resistance of 10 samples measured, respectively, the minimum value)

In Table 1, the sample No. 1 to 5 have a temperature of 200 ° C., a holding time of 10 minutes, and a pressing load of the hot pressing device 5 (hereinafter referred to as F) of 10 kgf (pressing pressure per unit area acting on the polymer PTC element 7 (hereinafter referred to as “pressing pressure”). Let P be this) = 12.7 kgf / cm ² )
To press load F = 60 kgf (P = 76.4 kgf /
Each test result when changed to cm ² ) is shown. (Below margin)

[0014]

[Table 1]

This sample No. As can be seen from the test results of 1 to 5, the press load F = 20 kgf (press pressure P = 25.5 kgf / cm ² ) to the press load F = 50.
In the range up to kgf (pressing pressure P = 63.5 kgf / cm ² ), the initial resistance value is low, the resistance variation is small, and the resistance value change by the heat shock test is small, but the pressing load F is 10 kgf (pressing force). Pressure P =
If it is too low (12.7 kgf / cm ² ), the initial resistance value, the resistance variation, and the resistance value change after the heat shock test become large. If the pressing load F is as high as 60 kgf (pressing pressure P = 76.4 kgf / cm ² ), the element body 1 protrudes from the electrode 2 and measurement becomes impossible. Therefore, the pressing pressure P applied to the polymer PTC element 7
Is preferably 25.5 kgf / cm ^{2 to} 63.5 k
It is gf / cm ² .

Sample No. In Nos. 6 to 9, the press load F was 35 kgf, the heat press holding time was 10 minutes, and the temperature was 1
It is a measurement result of each value when changing to 00 ° C, 150 ° C, 300 ° C, and 350 ° C. When the heat pressing temperature is 100 ° C., the initial resistance value, the resistance variation, and the resistance value change after the heat shock test are larger than those at 150 ° C. and 300 ° C. Further, when the hot press temperature reaches 350 ° C., the element body protrudes and measurement becomes impossible. Therefore, the hot pressing temperature is preferably 150 ° C to 300 ° C.
Is.

Sample No. 10 to 13 are measurement results of respective values when the press load F was 35 kgf, the hot press temperature was 200 ° C., and the hot press holding time was changed to 3 minutes, 5 minutes, 20 minutes, and 25 minutes. When the heat pressing time is 3 minutes, the initial resistance value, the resistance variation, and the resistance value change after the heat shock test are larger than those when the heat pressing time is 5 minutes or 20 minutes. Further, when the holding time reaches 25 minutes, the element body protrudes and measurement becomes impossible. Therefore, the hot pressing temperature is preferably 5 minutes to 20 minutes.

Sample No. 14 is a conventional example which does not perform hot pressing as in the present invention. * Sample No. within the above-mentioned suitable range without the mark. Nos. 2 to 4, 7 to 9, 11, and 12 are Nos. Compared with the sample of No. 14, the resistance value is about 1/5 lower, the resistance variation is about 40% or less (about 3/5 or less), and the resistance value change after the heat shock test is also compared with the conventional example, About 1/3
Became smaller.

[0019]

According to the present invention, it is possible to manufacture a polymer PTC element having a low initial resistance value, a small resistance value variation, and a small resistance value change due to thermal shock or the like.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for producing a polymer PTC element according to the present invention.

FIG. 2A is a side view of a conventional polymer PTC element,
(B) is a partially enlarged sectional view for explaining the problem.

[Explanation of symbols]

1: body, 2: electrode, 3: material, 4: punching device,
5: hot press machine, 6a, 6b: press plate, 7: polymer PTC element after punching, 8: polymer PTC element after hot pressing

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-153402 (JP, A) JP-A-9-69416 (JP, A) JP-A-8-298201 (JP, A) JP-A-8- 148305 (JP, A) JP 63-29901 (JP, A) JP 62-106602 (JP, A) JP 61-260606 (JP, A) JP 61-59701 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01C ^7/ 02-7/22

Claims (2)

(57) [Claims] 1. An electrode is formed by a metal plate or plating on the front and back surfaces of a plate-shaped element body having a positive resistance temperature characteristic which is made of a thermoplastic polymer and a composition in which a conductive substance is dispersed and mixed in the polymer. A method for producing a polymer PTC element, characterized in that the material is punched out into a predetermined element shape, and then the punched element is hot pressed to thermocompress the element body and the electrodes. 2. The hot press bonding condition according to claim 1, wherein the press pressure is 25.5 kgf.
/ Cm ^{2 to} 63.5 kgf / cm ² , temperature: 150 ° C. to 3
A method for producing a polymer PTC element, wherein the temperature is 00 ° C. and the holding time is 5 minutes to 20 minutes.