JP2008047681A - Ptc element, and battery protecting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PTC element wherein, when its electrode plate is joined to a terminal plate by welding, etc., its main body can be so prevented from deteriorating thermally, and its electrode plate and the terminal plate can be so connected with each other easily without using any clad plate that it can exhibit its intrinsic function effectively. <P>SOLUTION: The PTC element 2 has its main body 4 whose resistance value is increased with its temperature rise in a predetermined temperature region, and has a pair of first and second electrode plates 10, 12 joined respectively to the front and rear surfaces of its main body 4. Hereupon, a first-terminal joining film 14 containing aluminum is formed on at least a portion of the externally exposed surface of the first electrode plate 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PTC element used for the purpose of protecting a battery or an electronic circuit from an overcurrent, and a battery protection system having the PTC element.

  A PTC (positive temperature coefficient) element has a characteristic that the resistance value of the element increases when the temperature of the element rises in a predetermined temperature region. In particular, when the temperature of the PTC element reaches the melting temperature of the polymer, the resistance of the PTC element increases rapidly. Such a property is called a PTC characteristic.

  The PTC element is incorporated in an electric circuit such as an electronic device. If an excessive current flows in the circuit for some reason during use of the electronic device, the temperature of the electronic device rises, and the temperature of the PTC element itself rises accordingly. When the temperature of the PTC element reaches the melting temperature of the polymer, the resistance value of the PTC element increases rapidly. As a result, the PTC element blocks excess current in the electric circuit. Therefore, it is possible to prevent the electrical device from being damaged due to excessive current.

  Thus, the PTC element is used as a safety protection device against overheating and excessive current. Specifically, the PTC element is incorporated in a circuit (protection circuit) for protecting a secondary battery that is a power source of the mobile phone from overcurrent. When an excessive current flows during charging or discharging of the secondary battery, the PTC element cuts off the current and protects the secondary battery.

  An example of such a PTC element is a structure in which an element body (polymer positive temperature coefficient resistor) in which conductive particles are dispersed in a polymer material (crystalline polymer) is sandwiched between electrode plates (or metal foils). There is known a polymer PTC element having a thickness (see Patent Document 1).

  Conventionally, the polymer PTC element is manufactured by the following method. First, a polymer (such as high-density polyethylene) containing a conductive filler such as metal particles and carbon black is extruded to form an element body. Next, the polymer PTC element is completed by thermocompression bonding the electrode plate to the front and back surfaces of the element body.

  When this polymer PTC element is incorporated in a predetermined protective circuit, it is usually bonded via a clad plate between the electrode plate and the battery electrode terminal. This joining is performed by soldering, welding, or the like.

  The clad plate is obtained by joining different kinds of metals. In the above case, the clad plate is obtained by joining nickel or a nickel alloy constituting an electrode plate of an element and an aluminum material constituting a terminal plate. When such a clad plate is used, joining of the clad plate, the electrode plate of the element, and the battery electrode terminal can be performed with the same kind of metals, so that the joining becomes easy.

  However, when soldering, welding, or the like, it is necessary to heat at least a part of the clad plate, the electrode plate of the element, and the battery electrode terminal to a high temperature. Since the electrode plate (or metal foil) of the polymer PTC element is very thin, heat applied to the electrode plate of the element during soldering and welding is immediately conducted to the element body. As a result, the element body becomes high temperature and may be thermally deteriorated (softened or melted). When the element body is softened or melted, the dispersibility of the conductive particles in the polymer becomes locally non-uniform. In a polymer PTC element that has undergone such a thermal history, the resistance value at room temperature (room temperature resistance value) is greatly increased compared to that before this thermal history.

  Furthermore, if the temperature is repeatedly increased and decreased with respect to such a polymer PTC element, the room temperature resistance value of the polymer PTC element becomes higher. In such a polymer PTC element having a high room temperature resistance value, the power consumption increases.

  As described above, the increase in the room temperature resistance value of the polymer PTC element due to heating when the electrode plate of the element and the battery electrode terminal are joined is reduced when the battery is mounted on a small device such as a mobile phone. It leads to problems such as conversion.

In addition, since the clad plate is interposed to join the element electrode plate and the battery electrode terminal, it is difficult to reduce the thickness and weight of the entire circuit.
International Publication No. 2004/023499 Pamphlet

  The present invention has been made in view of such a situation, and an object thereof is to prevent the element body from being thermally deteriorated when the electrode plate and the terminal plate are joined by welding or the like, and without using a clad plate. It is an object of the present invention to provide a PTC element that can easily connect an electrode plate and a terminal plate and can effectively exhibit the original function of the element. Another object of the present invention is to provide a battery protection system capable of realizing a reduction in thickness and weight as the entire protection circuit.

In order to achieve the above object, the PTC element according to the present invention includes:
An element body whose resistance value increases as the temperature rises in a predetermined temperature range;
A PTC element having a pair of first and second electrode plates bonded to the front and back surfaces of the element body,
A first terminal bonding film containing aluminum is formed on at least a part of the surface of the first electrode plate exposed to the outside.

  Preferably, the element body is a conductive polymer having a positive temperature coefficient.

  In the PTC element according to the present invention, the first terminal bonding film containing aluminum is directly formed on the first electrode plate. By doing so, the first electrode plate and other electrode terminals (for example, secondary battery terminals) can be easily used by spot welding or the like without bonding the clad plate to the first electrode plate. Can be connected.

  Without using a clad plate, the electrode plate on which the first terminal bonding film of the PTC element is formed can be easily bonded to an electrode terminal of a secondary battery, etc., thereby reducing the thickness and weight of the entire protection circuit. Can be realized.

  The method for forming the first terminal bonding film is not particularly limited, and for example, various thin film forming methods can be used. Specifically, sputtering deposition, plasma spraying, ultrasonic bonding, or the like can be used.

Preferably, the first electrode plate includes a first element joining piece joined to the element body, and a first terminal joining piece formed integrally with the first element joining piece,
The first terminal bonding film is formed on the surface of the first terminal bonding piece.

  Since the first terminal bonding film is formed on the first terminal bonding piece and the first terminal bonding film and the element body are separated from each other, spot bonding or the like is used in bonding the first electrode plate and the electrode terminal. The generated heat is difficult to conduct to the element body. Therefore, thermal deterioration of the element body can be prevented.

  As a result, the PTC element according to the present invention can maintain high sensitivity, reduce power consumption during normal use, and protect the electronic device by cutting off the current when necessary. The original function can be effectively demonstrated.

  Further, when heat is applied to the entire PTC element during use, the metal (nickel or nickel alloy) constituting the first terminal joining piece is different from the metal (metal containing aluminum) constituting the first terminal joining film. Therefore, distortion due to a difference in thermal expansion may occur. Even in such a case, since the first terminal bonding film is not formed on the first element bonding piece, it is possible to effectively prevent the first electrode plate and the element body from being separated due to the above-described distortion. Can do.

  Preferably, the thickness of the first terminal bonding film is 3 to 100 μm, more preferably 5 to 50 μm. If the thickness of the first terminal bonding film is too thin, it is difficult to form a thin film such as sputtering, and spot welding may be difficult. Moreover, when the thickness of the first terminal bonding film is too thick, it tends to be difficult to efficiently form the thin film.

Preferably, the element bonding surface of the first element bonding piece is in direct contact with the surface of the element body, and an element bonding uneven part is formed on the element bonding surface,
An uneven portion for film bonding is formed on the surface of the first electrode plate on which the first terminal bonding film is formed.

  By forming unevenness on the element bonding surface, the bonding strength between the first electrode plate and the element body is improved, and by forming unevenness on the surface on which the first terminal bonding film is formed, the first electrode plate and the first electrode plate Bonding strength with the one-terminal bonding film is improved. In addition, since the element bonding surface of the first element bonding piece is in direct contact with the surface of the element body, a work such as brazing becomes unnecessary, and the manufacturing cost can be reduced.

  Preferably, the element bonding uneven part and the film bonding uneven part are simultaneously formed on one surface of the first electrode plate. By forming the uneven part for element bonding and the uneven part for film bonding on one surface of the first electrode plate, the process for forming the uneven part can be performed efficiently.

  Preferably, a protective film is formed on the exposed surface of the element body which is not covered with the first and second electrode plates. The protective film preferably has an oxygen barrier property. By configuring the protective film, it is possible to prevent deterioration of the element body.

  In the present invention, metal foil may be laminated on the front and back surfaces of the element body, and the first and second electrode plates may be bonded to each metal foil.

The battery protection system according to the present invention includes:
A PTC element according to any of the above,
A battery electrically connected to the first electrode plate of the PTC element;
And a protection circuit electrically connected to the second electrode plate of the PTC element.

  In the battery protection system according to the present invention, since the clad plate is not used, the overall protection system can be reduced in thickness and weight.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a cross-sectional view showing a main part of a PTC element according to an embodiment of the present invention,
2 is a perspective view of the PTC element shown in FIG.
FIG. 3 is a cross-sectional view of an essential part showing a use state of a PTC element according to another embodiment of the present invention,
FIG. 4 is a cross-sectional view of a PTC element according to another embodiment of the present invention.
Overall configuration of polymer PTC element

  First, as an embodiment of the PTC element according to the present invention, a polymer PTC element for protecting a secondary battery cell used as a power source of a mobile phone will be described.

A polymer PTC element 2 shown in FIG. 1 is incorporated between a secondary battery cell 32 which is a power source of a mobile phone and a protection circuit 30 for protecting the secondary battery cell 32 from overcurrent. The polymer PTC element 2 cuts off the current between the protection circuit 30 and the secondary battery cell 32 when an overcurrent that cannot be controlled by the protection circuit 30 flows during charging or discharging of the secondary battery cell 32. Thus, the secondary battery cell 32 is protected.
Below, the whole structure of a polymer PTC element is demonstrated first.

  A polymer PTC element 2 shown in FIG. 1 and FIG. 2 includes an element body 4 made of a conductive polymer having a positive resistance temperature characteristic (PTC characteristic). The element body 4 has front and back surfaces (a first surface 6 and a second surface 8 facing each other). A first electrode plate 10 and a second electrode plate 12 are joined to the first surface 6 and the second surface 8, respectively. As a result, the element body 4 is disposed so as to be sandwiched between the first electrode plate 10 and the second electrode plate 12.

  A first terminal bonding film 14 containing aluminum is formed with a thickness t0 on at least a part of the surface exposed to the outside of the first electrode plate 10. Preferably, the thickness t0 is 3 to 100 μm, more preferably 5 to 50 μm, and still more preferably 10 to 50 μm. A method for forming the first terminal bonding film 14 is not particularly limited, but in the present embodiment, the first terminal bonding film 14 is formed by a sputtering method.

  Since the first terminal bonding film 14 is made of a metal containing aluminum, the first terminal bonding film 14 can be easily connected to the electrode terminal 34 made of an aluminum material by spot welding or the like. Further, since the electrode plate of the element body and the electrode terminal of the battery can be connected without using a clad plate, the entire system can be reduced in thickness and weight.

  In the present embodiment, the first electrode plate 10 includes a first element joining piece 10a joined to the element body 4 and a first terminal joining piece 10b formed integrally with the first element joining piece 10a. And have.

  As shown in FIG. 2, the first terminal bonding piece 10b is formed to be narrower than the first element bonding piece 10a. When the width of the first element bonding piece 10a is W2 and the width of the first terminal bonding piece 10b is W1, preferably W1 / W2 = 0.5 to 1.0, more preferably 0.76 to 1.0. It is.

  The first terminal bonding film 14 may be formed on the first element bonding piece 10a, but is preferably formed only on the first terminal bonding piece 10b, and the distal end side of the first terminal bonding piece 10b. It is preferable to be formed. When the width of the first terminal bonding film 14 is W0, W0 / W1 = 0.5 to 1.0 is more preferable, and 0.56 to 1.0 is particularly preferable. Further, when the length of the first terminal bonding film 14 is L0 and the length of the first terminal bonding piece 10b is L1, L0 / L1 is more preferably 0.41 to 1.0, particularly preferably. Is 0.59 to 1.0.

  In addition, the element bonding surface 10c of the first element bonding piece 10a is in direct contact with the first surface 6 of the element body 4, and the element bonding surface 10c is uneven. Further, the terminal bonding surface 10d of the first terminal bonding piece 10b with the first terminal bonding film 14 is flatter than the element bonding surface 10c.

  The unevenness formed on the element bonding surface 10c is for strengthening thermocompression bonding with the element body 4, and the formation method is not particularly limited, but, for example, roughening treatment by forming a plating film is preferable. . A large number of nodular protrusions can be formed on the element bonding surface 10c of the first element bonding piece 10a by the roughening treatment by the plating film formation. This nodule-like protrusion is a convex part with a difference in unevenness of about 5 to 15 μm and a narrowed middle part or base part with respect to the head, and thermocompression bonding between the element body 4 and the element bonding surface 10c of the element bonding piece 10a. Strength can be improved.

  In addition, as a method of forming the unevenness formed on the element bonding surface 10c, in addition to the roughening treatment by plating film formation, the surface roughening treatment by acid machining, etching treatment, blast treatment, cutting, etc. Other processes are exemplified. The terminal bonding surface 10d of the first electrode plate 10 may be formed by forming a concavo-convex shape on the entire surface of one surface of the first electrode plate 10 and then performing a flattening process by pressing or the like. Alternatively, a portion other than the element bonding surface 10c may be masked to form irregularities only on the element bonding surface 10c.

  The first terminal bonding piece 10b on which the first terminal bonding film 14 is formed is spot-welded to the electrode terminal shown in FIG. 1, and the electrode terminal is electrically connected to the battery.

  Although the second electrode plate 12 is not particularly limited, in the present embodiment, the second electrode plate 12 has the same shape as the first electrode plate as shown in FIG. 2 terminal joining piece 12b. The second electrode plate 12 is made of nickel or a nickel alloy similarly to the first electrode plate 10, and the terminal plate 16 is connected to the second terminal joining piece 12b. The thickness of the terminal board 16 is usually about 100 to 300 μm.

  Further, the element bonding surface 12c of the second element bonding piece 12a in the second electrode plate 12 is formed with unevenness similar to the element bonding surface 10c, and is in direct contact with the second surface 8 of the element body.

  It is preferable that the surface 12d of the second electrode plate 12 other than the element bonding surface 12c of the second element bonding piece 12a does not have the unevenness formed on the element bonding surface 12c and is a flat surface. The method for forming irregularities on the element bonding surface 12c in the second electrode plate 12 and the method for flattening the surface 12d other than the element bonding surface 12c form a partially irregular surface on the first electrode plate 10. It is the same as the method.

  As shown in FIG. 1, a protective film 3 is formed on the surface of the element body 4 on the side surface not surrounded by the electrode plates 10 and 12 as necessary. By forming the protective film 3, it is possible to suppress the oxidation of the element body 4 due to oxygen in the atmosphere and to prevent the element body 4 from being deteriorated. The type of the protective film 3 is not particularly limited as long as it has a function of shielding oxygen, and examples thereof include an epoxy resin, EVOH (ethylene-vinyl alcohol copolymer, PVA (polyvinyl alcohol), and the like.

The shape of the element body 4 is not particularly limited, and examples thereof include a rectangular parallelepiped type and a cylindrical type. When the shape of the element body 4 is a rectangular parallelepiped, the dimensions of the element body 4 are about 3 to 5 mm in length, 2 to 5 mm in width, and about 0.5 to 1.0 mm in thickness.
Method for manufacturing polymer PTC element 2

Next, a manufacturing method of the polymer PTC element 2 will be described.
(1) Element body 4
The element body 4 is generally composed of a resin composition (conductive polymer) including a polymer (polymer compound such as a thermosetting resin or a thermoplastic resin) as main components and conductive particles. The element body 4 may include both a thermosetting resin and a thermoplastic resin as a polymer.

  First, a polymer compound (thermosetting resin, thermoplastic resin, etc.), conductive particles (metal powder, carbon black, etc.), a low molecular organic compound, a reaction initiator for cross-linking the polymer compounds, etc. Weigh and knead to adjust the PTC composition. The kneading method is not particularly limited, and examples thereof include a kneader, an extruder, and a mill. Further, as the conductive particles to be contained in the PTC composition, only conductive particles having a predetermined particle diameter are classified using a sieve or the like. Next, this PTC composition is shape | molded and the element main body 4 (FIG. 1) is obtained.

  Although it does not specifically limit as a thermosetting resin, An epoxy resin, a polyimide resin, unsaturated polyester resin, a silicon resin, a polyurethane resin, a phenol resin, etc. are mentioned. Preferably, an epoxy resin is used as the thermosetting resin. By using an epoxy resin, the polymer PTC element can have a sufficient resistance change amount and heat resistance. As for the molecular weight of the thermosetting resin, the weight average molecular weight Mw is usually about 300 to 10,000. Said thermosetting resin may be used independently and multiple types of resin may be used. Moreover, you may use the compound which has a structure where different kinds of thermosetting resins were bridge | crosslinked.

  Although it does not specifically limit as a thermoplastic resin, Preferably, a crystalline polymer is used. The melting point of the thermoplastic resin is not particularly limited, but is preferably about 70 to 200 ° C. By using a resin having a melting point within this range, it is possible to prevent the thermoplastic resin from melting, flowing, and deformation of the element body during the operation of the polymer PTC element.

  Specific thermoplastic resins include polyolefins such as polyethylene, copolymers such as ethylene-vinyl acetate copolymer, vinyl halides such as polyvinyl chloride, polyvinyl fluoride, and polyvinylidene fluoride, and vinylidene polymers, 12-nylon, and the like. Polyamide, polystyrene, polyacrylonitrile, thermoplastic elastomer, polyethylene oxide, polyacetal, thermoplastic modified cellulose, polysulfones, polymethyl (meth) acrylate, and the like.

  Although the weight average molecular weight Mw of a thermoplastic resin is not specifically limited, Preferably, it is 10000-5 million. These thermoplastic resins may be used alone or a plurality of types of resins may be used. Moreover, you may use the compound which has a structure where different types of thermoplastic resins were bridge | crosslinked.

  Although it does not specifically limit as electroconductive particle contained in the element main body 4, Metal powder, carbon black, etc. are illustrated. Preferably, metal powder is used as the conductive particles. As the metal powder, a powder mainly composed of nickel is preferably used. The average particle diameter of the metal powder is preferably 0.1 μm or more, and more preferably about 0.5 to 4.0 μm.

  In the element body 4, the content of the conductive particles in the resin composition is preferably 20 to 80% by mass with respect to the entire resin composition. By setting the content of the conductive particles within this range, the room temperature resistance value during non-operation can be sufficiently lowered, and a large resistance change amount can be obtained. Furthermore, variation in element resistance can be sufficiently reduced.

  The resin composition constituting the element body 4 further includes, for example, a low-molecular organic compound such as wax, oil, fatty acid, and higher alcohol in addition to the above-described thermosetting resin, thermoplastic resin, and conductive particles. But you can. As a result, it is possible to increase the resistance change amount accompanying the temperature rise of the element body 4.

  The element body 4 may include a base material that has a gap inside and can fill the gap with the resin composition. Such a substrate is not particularly limited as long as it can play the above role, and examples thereof include woven fabrics, nonwoven fabrics, and continuous porous bodies.

  The element body 4 is irradiated with an electron beam as necessary. By this electron beam irradiation, the reaction initiator functions and the cross-linking reaction between the polymers is promoted. The energy source for the crosslinking reaction is not limited to electron beams, and gamma rays, ultraviolet rays, heat, and the like are also used. What is necessary is just to adjust suitably the acceleration voltage and electron beam irradiation amount of the electron beam to irradiate according to the kind of high molecular compound contained in the element main body 4, or the dimension of an element main body. The electron beam irradiation may be performed after the electrode plates 10 and 12 are joined.

(2) Formation and thermocompression bonding of the first metal plate 10 and the second electrode plate 12 The first metal plate 10 and the second metal plate 12 are formed by punching and molding a nickel metal plate or nickel alloy plate having a predetermined thickness. . On the element bonding surface 10c of the first metal plate 10 and the element bonding surface 12c of the second metal plate 12, irregularities for strengthening thermocompression bonding with the element body 4 are formed by the method described above.

Next, the first electrode plate 10 and the second electrode plate 12 are thermocompression bonded to the front and back surfaces (the first surface 6 and the second surface 8) of the element body 4 by a hot press machine or the like. Although the heating temperature at the time of thermocompression bonding depends on the material of the element body 4, it is preferably about 130 to 180 ° C. The pressure during thermocompression bonding is preferably about 1 × 10 ^{6 to} 3 × 10 ⁶ Pa.

  At the time of thermocompression bonding, the element main body 4 is slightly crushed in the thickness direction due to pressure and may protrude slightly to the side of the electrode plates 10 and 12, but unnecessary portions can be easily removed.

(3) Formation of the first terminal bonding film 14 Next, or before and after, the first terminal bonding film 14 made of aluminum is formed on the first terminal bonding piece 10b by sputtering. The conditions are background vacuum: 1E-3 Pa, process gas: Ar, gas pressure during sputtering: 0.5-2 Pa, DC sputtering, voltage 300-800V.

(4) Formation of the protective film 3 Next, the protective film 3 is formed on the exposed side surface of the element body 4 that is not surrounded by the electrode plates 10 and 12 as necessary. A method for forming the protective film 3 is not particularly limited, and examples thereof include a method in which the above-described resin is applied and dried.
In this way, as shown in FIG. 2, the polymer PTC element 2 according to this embodiment is completed.
Assembly method of polymer PTC element 2

  As shown in FIG. 1, the polymer PTC element 2 is incorporated between the secondary battery cell 32 and the protection circuit 30. In order to connect the polymer PTC element 2 as shown in FIG. 1, for example, first, the first terminal bonding film 14 formed on the first terminal bonding piece 10b of the first electrode plate in the element 2 and the secondary battery Spot welding is performed in contact with the electrode terminal 34 of the cell 32. When a gap is formed between the element 2 and the secondary battery cell 32, the spacer 36 or the like is disposed between the element 2 and the secondary battery cell 32.

  Next, or before and after that, the terminal plate 16 connected to the protection circuit 30 is joined to the second terminal joining piece 12b of the second electrode plate 12 by spot welding.

  In the polymer PTC element 2 according to the present embodiment, the first terminal bonding film 14 is formed on the first terminal bonding piece 10b. The first terminal joining piece 10b does not have a portion that directly contacts the element body 4. Therefore, the heat generated when the first electrode plate 10 and the electrode terminal 34 of the secondary battery cell 32 are joined by spot welding or the like is not easily transmitted to the element body 4, thereby preventing thermal deterioration of the element body 4. be able to.

  Since the thermal degradation of the element body 4 can be prevented, the polymer PTC element 2 according to the present embodiment can maintain high sensitivity. Furthermore, during normal use, power consumption can be reduced, and when necessary, the original function of protecting the secondary battery cell 32 by cutting off the current can be effectively exhibited. .

  In addition, since the first terminal bonding film 14 is not formed on the first element bonding piece 10a, the first terminal bonding film 14 and the first terminal bonding piece 10b in which different metals are bonded to each other are distorted by heat. Even if it occurs, the first electrode plate 10 and the element body 4 do not peel off due to the influence.

  Furthermore, in the present embodiment, since the electrode plate of the PTC element and the electrode terminal of the battery cell can be joined without using the clad plate, the circuit as a whole can meet demands for reduction in thickness and weight. Is possible.

  Further, in the battery protection system having the polymer PTC element 2, the protection circuit 30, and the secondary battery cell 32 according to the present embodiment, even if an excessive current flows or an impact or pressure acts, the battery Can be effectively protected.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in FIG. 3, one surface of the first electrode plate 10 of the PTC element according to the present invention is entirely roughened. With such a configuration, not only the thermocompression bonding strength between the element bonding surface 10c and the element body 4 is improved, but also the first terminal bonding surface 10d is roughened. The bonding strength when forming can also be improved. In addition, since only one surface of the first electrode plate 10 has to be roughened as a whole, it can be processed efficiently.

  Also, in FIG. 4, metal foils 60 such as nickel are laminated on the front and back surfaces of the PTC element body 4 according to the present invention, and the first metal plate 10 and the second electrode plate with respect to each metal foil 60. 12 may be bonded via the solder layer 62. The metal foil 60 is made of a metal such as nickel or an alloy, and after the metal foil is hot-pressed on both surfaces of the sheet-like element body 4, it is integrated with the element body 4 by punching it out to a predetermined dimension. can do. The thickness of the metal foil 60 is thinner than the thickness of the electrode plates 10 and 12, and is generally 25-30 μm.

  Further, by configuring the second electrode plate as shown in FIG. 4, it is possible to make it difficult for heat generated at the time of joining to the terminal plate by spot welding or the like to be transmitted to the element body 4. In addition, since the second electrode plate 12 is bent and disposed, even if an impact is applied to the joint between the second electrode plate 12 and the terminal plate 16 due to dropping or the like, the second electrode plate 12 is provided. The bent portion 12e effectively absorbs the impact. Therefore, the joint part between the 2nd electrode board 12 and the terminal board 16 does not remove | deviate. The bent portion 12e of the second electrode plate 12 has a shape such as a substantially U-shaped cross section, a substantially V-shaped cross section, and a substantially U-shaped cross section.

  Even if pressure acts on the polymer PTC element 2 due to thermal expansion of the secondary battery cell 32, the bent portion 12e in the second electrode plate 12 effectively absorbs displacement due to the pressure, and the element body 4 No pressure is applied to the, and the function of interrupting excess current can be effectively exhibited.

  Further, the first electrode plate 10 may not have the first terminal joining piece 10b. That is, the first terminal bonding film 14 may be formed only on the first element bonding piece 10a.

  In these embodiments, the same effects as those of the above-described embodiments can be obtained.

  The polymer PTC element 2 according to the present invention is used not only as an overcurrent protection element for the secondary battery cell 32 but also as a self-control heating element, a temperature sensor, a current limiting element, an overcurrent protection element, and the like. It is possible.

  In the present invention, the method for producing the polymer PTC element 2 is not particularly limited. For example, as in the above-described embodiment, the polymer PTC element 2 is manufactured as follows without joining the element body 4, the first electrode plate 10, and the second electrode plate 12 to each other alone. Also good. That is, the sheet-like element body constituting the element body 4 after cutting and the pair of sheet-like electrodes that respectively constitute the first electrode plate 10 and the second electrode plate 12 after cutting are unnecessary after thermocompression bonding. Individual polymer PTC elements 2 may be formed by punching out the parts with a press. In that case, the efficiency of the manufacturing process of the polymer PTC element 2 can be improved by joining the assembly of parts constituting the polymer PTC element 2 at a time.

FIG. 1 is a cross-sectional view of a principal part showing a usage state of a PTC element according to an embodiment of the present invention. FIG. 2 is a perspective view of the PTC element shown in FIG. FIG. 3 is a cross-sectional view of a principal part showing a usage state of a PTC element according to another embodiment of the present invention. FIG. 4 is a cross-sectional view of a PTC element according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Polymer PTC element 3 ... Protective film 4 ... Element main body 10 ... 1st electrode plate 10a ... 1st element joining piece 10b ... 1st terminal joining piece 10c ... Element joining surface 10d ... Terminal joining surface 12 ... 2nd electrode plate 12a 2nd element bonding piece 12b ... 2nd terminal bonding piece 12c ... Element bonding surface 12d ... Surface other than element bonding surface 12c 12e ... Bent part 14 ... 1st terminal bonding film 16 ... Terminal board 30 ... Protection circuit 32 ... 2 Secondary battery cell 34 ... Secondary battery electrode terminal 60 ... Metal foil 62 ... Solder layer

Claims (9)

An element body whose resistance value increases as the temperature rises in a predetermined temperature range;
A PTC element having a pair of first and second electrode plates bonded to the front and back surfaces of the element body,
A PTC element, wherein a first terminal bonding film containing aluminum is formed on at least a part of a surface exposed to the outside of the first electrode plate.   The PTC element according to claim 1, wherein the element body is a conductive polymer having a positive temperature coefficient. The first electrode plate has a first element joining piece joined to the element body, and a first terminal joining piece molded integrally with the first element joining piece;
The PTC element according to claim 1, wherein the first terminal bonding film is formed on a surface of the first terminal bonding piece.   The PTC element according to claim 1, wherein the first terminal bonding film has a thickness of 3 to 100 μm. The element bonding surface of the first element bonding piece is in direct contact with the surface of the element body, and an element bonding uneven part is formed on the element bonding surface,
The PTC element according to any one of claims 1 to 4, wherein an uneven portion for film bonding is formed on a surface of the first electrode plate on which the first terminal bonding film is formed.   The PTC element according to claim 5, wherein the element bonding uneven part and the film bonding uneven part are simultaneously formed on one surface of the first electrode plate.   The PTC element according to claim 1, wherein a protective film is formed on an exposed surface of the element body that is not covered with the first and second electrode plates.   The PTC element according to any one of claims 1 to 7, wherein metal foils are laminated on the front and back surfaces of the element body, and the first and second electrode plates are bonded to each metal foil. . A PTC element according to any one of claims 1 to 8,
A battery electrically connected to the first electrode plate of the PTC element;
And a protection circuit electrically connected to the second electrode plate of the PTC element.

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