JP2002231506A - Ptc device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PTC device which is high in stability, reproducibility and reliability for repetitive use, and to provide its manufacturing method. SOLUTION: The PTC device 10 is equipped with a device body 12 composed of a crystalline high molecular component and conductive filler dispersed in it, and electrodes 14A and 14B bonded on the surface of the device body 12. The joint faces 14a and 14b of the electrode 14A and 14B joined to the device body 12 are previously subjected to an electrochemical surface treatment. By this setup, joints between the device body 12 and the electrodes 14A and 14B can be improved in bonding strength, so that the PTC device 10 can be improved in thermal resistance and set stable in resistance change for a service in a long term.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive temperature characteristic in which a resistance value rises abruptly when a temperature reaches a predetermined temperature (hereinafter referred to as a switching temperature) region, that is, a so-called PTC (Position) characteristic.
live Temperature Coefficie
nt) The present invention relates to a PTC element made of a conductive composition exhibiting characteristics and a method for producing the same.

[0002]

2. Description of the Related Art Hitherto, an electric circuit protection element has been used to prevent an overcurrent flowing when an abnormality occurs in an electric device / electronic device. In particular, electric circuit protection elements used in electric and electronic equipment, including secondary batteries,
An organic conductive composition in which a carbon-based conductive filler is dispersed in a crystalline polymer matrix is used.

[0003] In such an organic conductive composition, while the temperature is lower than the crystal melting point of the crystalline polymer matrix, the carbon-based conductive filler is present only in the non-crystalline region of the crystalline polymer matrix. It has a low resistivity due to a conductive mechanism that takes a chain structure and allows electrons to move through a carbon-based conductive filler. On the other hand, when the temperature increases and the crystalline polymer matrix begins to melt, the volume of the crystalline polymer matrix increases, so the distance between the carbon-based conductive fillers in the crystalline polymer matrix increases, As a result, the destruction of the conductive path proceeds and the resistance increases.

By applying the above operation principle, an electric circuit protection element has a low resistance at room temperature, and the resistance increases as the temperature rises, thereby limiting the current, particularly, the resistance rapidly increases at a desired switching temperature. PT consisting of conductive composition
C element is used.

[0005]

However, in the above-mentioned conventional PTC element, there is a problem that a change in resistance becomes large as the switching operation is repeated. In addition, P having good conductivity with the above conductive composition
In order to obtain a TC element, it is necessary to increase the filling of the conductive filler. However, when such a filling of the conductive filler is performed, the bonding to the element body is performed while the switching operation is repeated. Since the electrodes used are easily peeled off from the element body, sufficient reliability for long-term use (repeated use) cannot be obtained.

Therefore, a technical problem of the present invention is to provide a highly reliable P having good stability and reproducibility against repeated use.
An object of the present invention is to provide a TC element and a method for manufacturing the same.

[0007]

In order to achieve the above object, according to the present invention, a conductive composition containing a crystalline polymer component and a conductive filler is sandwiched between electrodes subjected to electrochemical surface treatment. Thus, the element body and the electrode are joined by thermocompression bonding. By this electrochemical surface treatment, a strong chemical bond between the polymer and the metal, which has not been obtained conventionally, can be obtained.

[0008] For this reason, even if the content of the crystalline polymer component is relatively reduced by performing high filling of the conductive filler,
A good adhesion state between the element body and the electrode can be maintained, and the element characteristics can be stabilized, so that a PTC element having good conductivity can be obtained. As a result, even if the switching operation is repeatedly performed, the electrodes do not peel off from the element body, and an overcurrent protection element or the like with a small increase in resistance and high reliability as compared with the related art can be provided.

That is, a PTC element according to claim 1 includes an element body in which a conductive filler is dispersed in a crystalline polymer component;
PTC having an electrode joined to the surface of the element body
An element, wherein at least a bonding surface of the electrode with the surface of the element body is subjected to an electrochemical surface treatment.

In the PTC element according to the present invention, the surface of the electrode to be joined to the element body is subjected to the electrochemical surface treatment by the general formula (1):

[0011]

Embedded image (Wherein R represents OR ′, SR ′, NHR ′, or (R ′) ₂ , where R ′ represents an alkyl group, a phenyl group, a phenylalkyl group, an alkylphenyl group, or a cycloalkyl group; M is H, Na, Li, K,
1 / 2Ba, 1 / 2Ca, aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines, or aliphatic quaternary ammonium salts) as the electrodeposition solution. The conductive foil as an anode, a platinum material,
A triazine thiol treatment using a titanium material or a carbon material as a cathode is performed, and a bonding surface between the element body and the electrode has a strong chemical bond.

According to a third aspect of the present invention, there is provided a method of manufacturing a PTC element, comprising the steps of: subjecting a conductive filler to a surface treatment with a coupling agent; Kneading the conductive composition to produce an electroconductive composition, performing an electrochemical surface treatment on at least a bonding surface of the electrode bonded to the surface of the electroconductive composition, and bonding the pair of electrodes. A step of sandwiching the conductive composition between surfaces and performing thermocompression bonding.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a PTC element, wherein the surface of the electrode to be joined to the element body is subjected to the electrochemical surface treatment by the general formula (1):

[0014]

Embedded image (Wherein R represents OR ′, SR ′, NHR ′, or (R ′) ₂ , where R ′ represents an alkyl group, a phenyl group, a phenylalkyl group, an alkylphenyl group, or a cycloalkyl group; M is H, Na, Li, K,
1 / 2Ba, 1 / 2Ca, aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines, or aliphatic quaternary ammonium salts) as the electrodeposition solution. The conductive foil as an anode, a platinum material,
A triazine thiol treatment using a titanium material or a carbon material as a cathode is performed, and a bonding surface between the element body and the electrode has a strong chemical bond.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a PTC element according to an embodiment of the present invention.

As shown in FIG. 1, a PTC element 10 of the present embodiment has an element body 12 made of a conductive composition described later.
And electrodes 14A and 14 made of a conductive foil, which will be described later, provided on the opposing first surface 12A and second surface 12B of the element body 12 with the element body 12 interposed therebetween.
B.

The conductive composition constituting the element body 12 is as follows:
For example, it is manufactured by dispersing a conductive filler such as a metal-based filler in a crystalline polymer component such as a polyethylene type high adhesive resin. As the conductive foil constituting the electrodes 14A and 14B, for example, a metal foil is used, and at least the bonding surfaces of the electrodes 14A and 14B with the opposing first surface 12A and the second surface 12B of the element body 12 are electrochemical. The surface is subjected to an organic plating treatment, that is, a structure having a strong chemical bond.

Here, the above-mentioned organic plating treatment is performed by the following general formula (1):

[0020]

Embedded image (Wherein R represents OR ′, SR ′, NHR ′, or (R ′) ₂ , where R ′ represents an alkyl group, a phenyl group, a phenylalkyl group, an alkylphenyl group, or a cycloalkyl group; M is H, Na, Li, K,
1 / 2Ba, 1 / 2Ca, aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines, or aliphatic quaternary ammonium salts) as the electrodeposition solution. The conductive foil as an anode, a platinum material,
Triazine thiol treatment using a titanium material or a carbon material as a cathode is exemplified.

In the method of manufacturing the PTC element 10 according to the present embodiment, first, the conductive filler is subjected to a surface treatment with a coupling agent, and the conductive filler, the crystalline polymer component, and the cross-linking thereof are performed. The composition is kneaded with an agent to produce a conductive composition constituting the element body 12. Next, an electrochemical surface treatment is performed on at least the bonding surfaces of the conductive foils to be the electrodes 14A and 14B bonded to the surface of the conductive composition, and the conductive composition is applied between the bonding surfaces of the conductive foils. Insert and thermocompression. The PTC element 10 of the present embodiment can be manufactured through the above steps.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the PTC element of the present invention and a method for manufacturing the same will now be described in detail.

First, an adhesive polyolefin (trade name: M
(ODIC-AP), 100 parts by weight, 525 parts by weight of TiC filler (product of Nippon Shinkin) surface-treated with a coupling agent (trade name: KR-TTS), and a crosslinking agent for adhesive polyolefin and TiC filler (product) Name: Perhexin 25B) and 5 parts by weight were homogeneously kneaded at 150 ° C. for 15 minutes to produce a conductive composition.

Next, the surface of the copper foil having a thickness of 20 μm bonded to the surface of the conductive composition is treated with triazine thiol,
The above conductive composition is sandwiched between two copper foils, and the thickness is 300
After applying pressure and spreading to 200 μm,
Heat cured for minutes. Then, the conductive composition to which the copper foil was bonded was cut into a ring shape having an outer diameter of 10 mmφ and an inner diameter of 6 mmφ to produce a PTC element.

A lead wire was attached to the PTC device of the present invention, and the bonding strength (g) between the copper foil and the conductive composition was measured. As a comparative product, a similar PTC element was manufactured using a copper foil that had not been treated with triazinethiol, a lead wire was attached, and the bonding strength (g) between the copper foil and the conductive composition was measured. Table 1 shows the results.

[0026]

[Table 1] As is clear from the measured values shown in Table 1, the bonding strength of the comparative product was 20 g to 200 g, whereas the bonding strength of the product of the present invention was as high as 1000 g to 3000 g. Accordingly, the copper foil and the conductive composition, that is, the electrodes 14A and 14B and the element body 12 are hardly peeled off, and sufficient reliability for long-term use (repeated use) can be obtained.

A lead wire is attached to the PTC element of the present invention, and the initial resistance value (mΩ) when a voltage of 60 V is applied and when exposed to an atmosphere of 120 ° C.
A life test was performed by measuring the resistance value (mΩ) after the elapse of 0 hour. As a comparative product, a similar PTC element was manufactured using a copper foil not treated with triazine thiol, a lead wire was attached thereto, and a voltage of 60 V was applied.
Initial resistance value (mΩ) when exposed to an atmosphere of 20 ° C
After 100 hours, the resistance value (mΩ) was measured, and a life test was performed. The results are shown in Tables 2 and 3.

[0028]

[Table 2]

[Table 3] As is clear from the measured values shown in Table 2, the resistance value of the comparative product after a lapse of 100 hours when a voltage of 60 V was applied increased from the initial resistance value of 20 mΩ to 50 mΩ, whereas that of the present invention product The resistance value after 100 hours has hardly changed from the initial resistance value of 20 mΩ to 22 mΩ. According to the present invention, the resistance change rate is small, and excellent stability and reproducibility for long-term use (repeated use) can be obtained. Can be.

As is clear from the measured values shown in Table 3, 100% of the comparative product when exposed to an atmosphere of 120 ° C.
The resistance value after the elapse of time is 25 m from the initial resistance value of 20 mΩ.
While the resistance value of the product of the present invention after 100 hours has not changed at all from the initial resistance value of 20 mΩ to 20 mΩ, the resistance change rate is extremely small according to the present invention,
Excellent stability and reproducibility for long-term use (repeated use) can be obtained.

Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to these embodiments, and is applicable to other embodiments within the scope of the invention described in the claims. You.

For example, in the above-described embodiment, an adhesive polyolefin was used as the main component of the conductive composition, a TiC filler was used as the conductive filler, and a copper foil was used as the conductive foil. It is not something to be done. As a main component of the conductive composition, besides high-density polyethylene type, polypropylene type and low-density polyethylene type can be used. As the conductive filler, in addition to TiC, WC, W ₂ C, Zr
One, two or more of C, VC, NbC, TaC, and Mo ₂ C can be used. Further, as the conductive foil, a nickel foil or the like can be used in addition to the copper foil.

In the above-described embodiment, 525 parts by weight of a TiC filler whose surface was treated with a coupling agent and 5 parts by weight of a crosslinking agent were mixed with 100 parts by weight of the adhesive polyolefin to form a conductive composition. However, with respect to 100 parts by weight of the adhesive polyolefin, the conductive filler to be surface-treated with the coupling agent is in the range of 300 to 550 parts by weight, and the crosslinking agent is in the range of 0.01 to 100 parts by weight. The effect is obtained.

The reason why the conductive filler is in the range of 300 to 550 parts by weight with respect to 100 parts by weight of the adhesive polyolefin is that if it is blended within this range, good conductive properties can be obtained in a uniformly dispersed system. This is because the property can be obtained. In addition, the reason for setting the crosslinking agent in the range of 0.01 to 100 parts by weight with respect to 100 parts by weight of the adhesive polyolefin is that the addition within this range can promote the reaction and efficiently cause the crosslinking reaction. Because you can do it.

[0034]

As described above, according to the present invention,
P with excellent heat resistance and stable resistance value change even after long-term use
A TC element can be provided. Therefore, P of the present invention
With the TC element, it is possible to obtain an overcurrent protection element or the like having stable element characteristics requiring large switching power.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a PTC element according to an embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 PTC element 12 Element main body 12A First surface of element main body 12 12B Second surface of element main body 12 14A Electrode 14B Electrode 14a Bonding surface of electrode 14A to first surface 12A of element main body 12B Element at electrode 14B Bonding surface of main body 12 to second surface 12B

Claims (4)

[Claims] 1. A PTC element having an element main body in which a conductive filler is dispersed in a crystalline polymer component, and an electrode joined to a surface of the element main body, wherein at least the element main body in the electrode is provided. A PTC element, wherein a bonding surface with the surface is subjected to an electrochemical surface treatment. 2. The PTC element according to claim 1, wherein
The surface of the electrode that is to be bonded to the element body is subjected to the following general formula (1) as the electrochemical surface treatment: (Wherein R is OR ′, SR ′, NHR ′, or (R ′) ₂ , where R ′ represents an alkyl group, a phenyl group, a phenylalkyl group, an alkylphenyl group, or a cycloalkyl group; M is H, Na, Li, K,
1 / 2Ba, 1 / 2Ca, aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines, or aliphatic quaternary ammonium salts) as the electrodeposition solution. The conductive foil as an anode, a platinum material,
A PTC element having a structure in which a triazine thiol treatment using a titanium material or a carbon material as a cathode is performed, and a bonding surface between the element body and the electrode has a strong chemical bond. 3. A step of subjecting the conductive filler to a surface treatment with a coupling agent, and kneading the conductive filler, a crystalline polymer component, and a crosslinking agent thereof to produce a conductive composition. A step of performing an electrochemical surface treatment on at least a bonding surface of an electrode bonded to the surface of the conductive composition, and sandwiching the conductive composition between the bonding surfaces of the pair of electrodes. A method for producing a PTC element, comprising a step of thermocompression bonding. 4. The method of manufacturing a PTC device according to claim 3, wherein the surface of the electrode that is to be joined to the device body is subjected to the electrochemical surface treatment by the general formula (1): (Wherein R is OR ′, SR ′, NHR ′, or (R ′) ₂ , where R ′ represents an alkyl group, a phenyl group, a phenylalkyl group, an alkylphenyl group, or a cycloalkyl group; M is H, Na, Li, K,
1 / 2Ba, 1 / 2Ca, aliphatic primary amines, aliphatic secondary amines, aliphatic tertiary amines, or aliphatic quaternary ammonium salts) as the electrodeposition solution. The conductive foil as an anode, a platinum material,
A method for producing a PTC element, wherein a triazine thiol treatment using a titanium material or a carbon material as a cathode is performed, and a bonding surface between the element body and the electrode has a strong chemical bond.