JP4497142B2 - PTC element and battery protection system - Google Patents

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 constituting the element body, 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. And when the temperature of a PTC element reaches the melting temperature of the polymer which comprises an element main body, the resistance value of a PTC element will increase 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 the polymer PTC element is incorporated in a predetermined protection circuit, the electrode plate is joined to a terminal plate electrically connected to the protection circuit. This joining is conventionally performed by soldering, welding, or the like.

  When performing soldering, welding, etc., it is necessary to heat at least a part of the electrode plate and the terminal plate 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 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 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.

  Further, when the element main body is directly exposed to the atmosphere, there is a problem that the element main body is oxidized by oxygen in the atmosphere. When the element body is oxidized, the room temperature resistance value of the polymer PTC element at room temperature is greatly increased as compared with that before the element body is oxidized. Further, the oxidation of the element body is promoted by the above-described heating by soldering, welding or the like.

  Furthermore, if the temperature rise and fall of the polymer PTC element whose element body is thermally deteriorated or oxidized is repeated, 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 leads to problems such as waste of power or shortening of battery life when mounted on a small device such as a mobile phone.

  As a method for preventing the oxidation of the element body and the accompanying increase in the room temperature resistance value of the polymer PTC element, forming a protective film on the exposed surface of the element body that is not covered with the electrode plate can be mentioned. The protective film is formed by applying a resin having a function of shielding oxygen to the exposed surface of the element body.

In such a conventional protective film forming method, when the resin is applied to the exposed surface of the element body, the resin is applied to the surface of the electrode plate joined to the element body (the portion where the resin should not be applied). However, it becomes a problem that it is covered with a protective film. When a protective film is formed on the surface of the electrode plate, a step is formed there. When joining the terminal plate to the electrode plate, this step (because a protective film is interposed between the electrode plate and the terminal plate) causes a bonding failure. In addition, if the resin that should be applied to the element body is applied to the surface of the electrode plate, the coating thickness of the resin on the exposed surface of the element body may be reduced. As a result, there is a possibility that oxidation of the element body cannot be sufficiently prevented.
International publication WO2004 / 023499

  The present invention has been made in view of such a situation, and the object thereof is to prevent oxidation of the element body, and when the electrode plate and the terminal plate are joined by welding or the like, the element body is thermally deteriorated. It is an object of the present invention to provide a PTC element that can prevent the formation of a protective film on the surface of an electrode plate. Another object of the present invention is to provide a battery protection system capable of effectively protecting a battery when an excessive current flows.

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 protective film is formed on the exposed surface of the element body that is not covered with the first and second electrode plates,
At least the first electrode plate of the first and second electrode plates has a protruding portion that protrudes outward from an element joint surface with the element body. Preferably, the protrusion protrudes outward from the element bonding surface in the same plane as the element bonding surface.

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

  In the PTC element according to the present invention, it is possible to prevent the element body from being oxidized by oxygen in the atmosphere by forming a protective film on the exposed surface of the element body. Further, by preventing oxidation of the element body, it is possible to prevent an increase in the room temperature resistance value of the polymer PTC element at room temperature. Further, the element body can be protected from an external impact by the protective film. That is, the mechanical strength of the element body can be improved by the protective film.

   In the PTC element according to the present invention, at least the first electrode plate of the first and second electrode plates has a protrusion. Therefore, when the resin (protective film forming resin) is applied to the exposed surface of the element body, and the protective film is formed, the resin that tries to go around from the exposed surface of the element body to the surface of the first electrode plate protrudes. Obstructed by the department. That is, the resin is prevented from being applied to the surface of the first electrode plate (the side to which the terminal plate is joined). Therefore, the protective film is not formed on the surface of the first electrode plate (the side to be joined to the terminal plate), and the first electrode plate and the terminal plate can be favorably joined.

  Furthermore, by preventing the resin that should be originally applied to the exposed surface of the element body from being applied to the surface of the first electrode plate (the surface that the resin should not be originally applied), The coating thickness of the resin on the exposed surface can be made sufficient. As a result, it is possible to effectively prevent the element body from being oxidized.

  Further, in the PTC element according to the present invention, the first electrode plate has the protruding portion, so that heat accompanying the joining process (soldering or welding) between the first electrode plate and the terminal plate is transmitted from the protruding portion to the atmosphere. Heat can be dissipated inside. As a result, compared with a case where the first electrode plate has no protrusion, heat conduction to the element body is suppressed, and thermal deterioration of the element body can be prevented.

  Further, in the PTC element according to the present invention, the first electrode plate has the protruding portion, so that when the element main body and the first electrode plate are joined, positioning between the two becomes easy. That is, even when a positional deviation of about the dimension of the protruding portion or less occurs during positioning, the element body and the first electrode plate can be satisfactorily bonded without exposing the front and back surfaces of the element body to the outside. it can.

  As described above, since the oxidation and thermal deterioration of the element body can be prevented, the PTC element according to the present invention can reduce power consumption during normal use, and if necessary, The original function of protecting the electronic device by cutting off the current can be effectively exhibited.

  Preferably, a terminal plate for connecting to a predetermined circuit and the first electrode plate are bonded at a terminal bonding portion located at a portion where the terminal plate and the first electrode plate overlap, and the terminal bonding portion The protrusion is located in the vicinity of.

  Since the protrusion is positioned in the vicinity of the terminal joint portion of the first electrode plate, the resin is applied from the exposed surface of the element body to the periphery of the terminal joint portion when the protective film forming resin is applied to the exposed surface of the element body. I can't go around. Therefore, it can prevent that resin is apply | coated to the junction part vicinity. As a result, the first electrode plate and the terminal plate can be satisfactorily bonded without being interposed in the resin (protective film) at the terminal bonding portion.

  Preferably, the first electrode plate has a rectangular shape, and the protruding portion is positioned along two opposite sides (two sides opposed in the rectangle) of the first electrode plate. More preferably, the protrusion is located on the outer periphery of the first electrode plate.

  When the protrusion is positioned along the two opposite sides of the first electrode plate, the resin is applied from the exposed surface of the element body to the exposed surface of the element body from the two sides. It is possible to prevent wrapping around the surface of the first electrode plate (terminal junction side). Moreover, even if resin is applied to the exposed surface of the element body from the two sides where the protrusions are not formed in the first electrode plate, the resin is not separated from the two sides where the protrusions are not formed. It wraps around below the protrusions located on the two sides (element body side). Therefore, it is possible to prevent the resin from wrapping around from the exposed surface of the element body to the surface of the first electrode plate (terminal junction side).

  In addition, since the protrusion is positioned on the outer periphery (four sides) of the first electrode plate, the resin is exposed to the exposed surface of the element body even when the resin is applied to any side surface (exposed surface) of the element body. Thus, it is possible to reliably prevent the first electrode plate from entering the surface (terminal joint side).

  Preferably, the tip of the protrusion is bent toward the element body.

  The tip of the protrusion is bent toward the element body, so that when the resin is applied to the exposed surface of the element body, a small amount of resin wraps around the protrusion (on the terminal joint portion side of the first electrode plate). Even in this case, the resin is held only at the tip (bent portion) of the protruding portion. Therefore, the resin does not wrap around the entire upper surface of the protruding portion (the terminal joint portion side of the first electrode plate). Therefore, it is possible to prevent the resin from flowing from the exposed surface of the element body to the surface of the first electrode plate.

  Preferably, a recess is formed on the surface of the protruding portion on the element body side.

  Since the concave portion is formed on the surface of the projecting portion on the element body side, the resin is held inside the concave portion when the resin is applied to the exposed surface of the element body. In other words, the concave portion serves as an anchor that prevents the resin from entering the surface of the first electrode plate. Thus, the recess can prevent the resin from flowing from the exposed surface of the element body to the surface of the first electrode plate.

  Preferably, a concavo-convex portion for adhesion of a protective film is formed on the surface of the protrusion on the element body side.

  By forming the protective film adhesion uneven portion on the surface of the element main body side of the protruding portion, the resin is held in the protective film adhesion uneven portion when the resin is applied to the exposed surface of the element main body. Therefore, the resin can be prevented from flowing from the exposed surface of the element body to the surface of the first electrode plate.

  Preferably, an element bonding uneven part is formed on the element bonding surface of the first electrode part, and the element bonding uneven part is continuous with the protective film uneven part.

  By forming the concave / convex portion for element bonding on the element bonding surface of the first electrode plate, the bonding strength between the first electrode plate and the element body is improved. In addition, since the element bonding surface of the first electrode plate is in direct contact with the surface of the element body, work such as brazing is not required, and the manufacturing cost can be reduced. Moreover, the uneven | corrugated part for element joining and the uneven | corrugated part for protective films are continuously formed in the same process by forming the uneven | corrugated part for element bonding and the uneven | corrugated part for protective films simultaneously by the same process. In this way, the manufacturing cost can be reduced.

  Preferably, the terminal plate is composed of a nickel terminal plate mainly containing nickel.

  By using the terminal plate mainly composed of nickel, the strength of joining (spot welding) with the first electrode plate mainly composed of nickel can be improved.

  Preferably, the second electrode plate is bonded to a clad plate in which two or more kinds of plate materials are laminated.

  When the second electrode plate is made of a material different from that of the battery electrode, a clad plate is interposed between the second electrode plate and the battery electrode. By spot welding, the second electrode plate and the side surface of the clad plate having the same material as the second electrode plate are joined, and the side surface of the clad plate having the same material as the battery electrode is joined to the battery electrode. As a result, the connection between the second electrode plate and the battery electrode is facilitated as compared with the case where no clad plate is used.

  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 protection circuit electrically connected to the first electrode plate of the PTC element;
A battery electrically connected to the second electrode plate of the PTC element.

  In the battery protection system according to the present invention, even when an excessive current flows, the battery can be effectively protected. In addition, since the battery protection system includes the PTC element that has no thermal deterioration and has a low room temperature resistance value, the power consumption of the battery protection system and the entire electronic device having the battery protection system can be reduced.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a cross-sectional view of a principal part showing a use state (battery protection system) of a PTC element according to an embodiment of the present invention.
2 is a cross-sectional view of the PTC element shown in FIG.
FIG. 3 is an enlarged view of the II part shown in FIG.
FIG. 4 is an external view of a polymer PTC element according to an embodiment of the present invention viewed in the IV direction of FIG. 2, and shows the positional relationship between the first electrode plate, the terminal joint, the protective film, and the element body. Schematic,
5A and 5B are schematic views showing a method of applying a resin for forming a protective film on the exposed surface of the element body in the manufacturing process of the polymer PTC element according to an embodiment of the present invention;
FIG. 6 is a cross-sectional view showing a bent tip of a protruding portion of a PTC element according to another embodiment of the present invention,
FIG. 7 is a cross-sectional view showing a recess formed on the surface on the element body side in the protruding portion of the PTC element according to another embodiment of the present invention,
FIG. 8 is a cross-sectional view showing a protective film adhesion uneven part and an element joining uneven part formed on the surface of the element body side in the protruding part of the PTC element according to another embodiment of the present invention,
FIG. 9 is a schematic diagram showing a positional relationship among a first electrode plate, a terminal joint, a protective film forming resin, and an element body in a polymer PTC element according to another embodiment of the present invention,
FIG. 10 is a cross-sectional view of a PTC element according to another embodiment of the present invention.

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

  The polymer PTC element 2 shown in FIG. 1 is incorporated between a secondary battery cell 32 that is a power source of a mobile phone and a protection circuit 30 (predetermined circuit) 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. The first surface 6 of the element body 4 is bonded to the element bonding surface 5 of the first electrode plate 10. Thus, the element body 4 is disposed so as to be sandwiched between the first electrode plate 10 and the second electrode plate 12.

  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.

  The first electrode plate 10 is spot-welded to the terminal plate 16 at a terminal joint portion 9 (see FIG. 4) located at a portion where the terminal plate 16 and the first electrode plate 10 overlap. Terminal plate 16 is electrically connected to protection circuit 30. The first electrode plate 10 is made of nickel or a nickel alloy, and the terminal plate 16 is also made of a nickel terminal plate (a plate mainly containing nickel) that can be easily joined in spot welding with the first electrode plate 10. . Although the thickness of the 1st electrode plate 10 is not specifically limited, Usually, it is about 100-300 micrometers. The thickness of the terminal board 16 is not particularly limited, but is usually about 100 to 300 μm.

  The second electrode plate 12 is spot welded to a clad plate 18 in which two or more kinds of plate materials are laminated. The second electrode plate 12 is made of nickel metal or nickel alloy. Although the thickness of the 2nd electrode plate 12 is not specifically limited, Usually, it is about 100-300 micrometers. The length of the 2nd electrode plate 12 is not specifically limited, It designs freely according to a use.

  The clad plate 18 is composed of a laminated plate of a nickel layer 20 and an aluminum layer 22. The nickel layer 20 in the clad plate 18 is joined to the second electrode plate 12 made of nickel metal or nickel alloy by spot welding or the like. Further, the aluminum layer 22 in the clad plate 18 comes into contact with the electrode terminal 34 of the secondary battery cell 32 and is joined by spot welding or the like.

  The thickness of the clad plate 18 is not particularly limited, but is usually about 100 to 300 μm. The length of the clad plate 18 is not particularly limited and can be freely designed according to the application.

  The electrode terminal 34 of the secondary battery cell 32 is generally made of an aluminum material and is easily bonded to the aluminum layer 22 in the clad plate 18.

  In the present embodiment, as shown in FIGS. 1 and 2, a protective film 3 is formed on the exposed surface of the element body 4 that is not covered with the first electrode plate 10 and the second electrode plate 12. 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. Further, by preventing oxidation of the element body, it is possible to prevent an increase in the room temperature resistance value of the polymer PTC element at room temperature. Moreover, the element main body 4 can be protected from an external impact by the protective film 3.

  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 epoxy resin, EVOH (ethylene-vinyl alcohol copolymer), PVA (polyvinyl alcohol), and the like.

The thickness _{t 0} of the protective film 3 shown in FIG. 3 is not particularly limited, about 10 to 200 [mu] m. If the thickness t ₀ is too thin, the protective film 3 cannot sufficiently prevent the element body 4 from being oxidized. When the thickness t ₀ is too thick, the resin of the other to form a protective film 3, the surface of the first electrode plate 10 is likely to be applied to the (terminal plate 16 side to be joined). Therefore, these problems can be prevented by setting the thickness t ₀ within the above range.

  In the present embodiment, at least the first electrode plate 10 of the first electrode plate 10 and the second electrode plate 12 shown in FIGS. 1 and 2 protrudes outward from the element joint surface 5 with the element body 4. Part 7.

  By having the protrusion 7, when the resin is applied to the exposed surface of the element body 4 to form the protective film 3, the surface of the first electrode plate 10 (the terminal plate 16 is bonded to the exposed surface of the element body 4. The resin which is going to go around to the side is hindered by the protrusion 7. That is, it is possible to prevent the resin from being applied to the surface of the first electrode plate 10. Therefore, the protective film 3 is not formed on the surface of the first electrode plate 10, and the first electrode plate 10 and the terminal plate 16 can be adhered and bonded satisfactorily.

The protrusion height W ₀ of the protrusion 7 shown in FIG. 3 is not particularly limited, but is preferably about 20 to 500 μm with respect to the end of the element bonding surface 5 (the surface of the element body 4).

If the protruding height W ₀ is too small, the resin cannot be sufficiently prevented from flowing from the exposed surface of the element body 4 to the surface of the first electrode plate 10. On the other hand, if the protrusion height W ₀ is too large, when the protective film 3 is formed on the exposed surface of the element body 4, air may be taken in between the exposed surface and the protective film (resin for use). . When air is taken in in this way, oxidation of the element body 4 cannot be prevented by the protective film. Therefore, these problems can be prevented by setting the protrusion height W ₀ within the above range.

  As shown in FIG. 4, the protrusion 7 is preferably located in the vicinity of the terminal joint 9.

  When the protrusion 7 is positioned in the vicinity of the terminal joint 9 in the first electrode plate 10, the resin is exposed to the element body when the resin for forming the protective film 3 is applied to the exposed surface 4 a of the element body. It does not wrap around the terminal joint 9 from the surface 4a. That is, it is possible to prevent the resin from being applied near the terminal joint 9. As a result, the first electrode plate 10 and the terminal plate 16 can be satisfactorily adhered and bonded (spot welded) without being blocked by the protective film 3 in the terminal bonding portion 9.

  When there is no protrusion 7 near the terminal joint 9, the protective film 3 is formed in the vicinity of the terminal joint 9, and a step is generated between the protective film 3 and the surface of the first electrode plate 10. If the first electrode plate 10 and the terminal plate 16 are to be joined at the stepped portion, they cannot be brought into close contact with each other due to the step, resulting in poor bonding. Therefore, this problem can be prevented by positioning the protrusion 7 in the vicinity of the terminal joint 9.

  Preferably, the protrusion 7 is located on the outer periphery of the first electrode plate 10. In other words, it is preferable that the area of the first electrode plate 10 is larger than the area of the first surface of the element body, and the first surface of the element body is completely covered by the first electrode plate 10.

  The protrusion 7 is positioned on the outer periphery (four sides of the rectangle) of the first electrode plate 10, so that the resin is exposed to the element body 4 even when the resin is applied to any side surface of the element body 4. It is possible to reliably prevent the surface 4a from entering the surface of the first electrode plate 10.

  In addition, since the area of the first electrode plate 10 is larger than the area of the first surface of the element body 4, the element body 4 with respect to the first electrode plate 10 when the element body 4 and the first electrode plate 10 are joined. It is easy to perform positioning. That is, even if there is a slight deviation in positioning between the element body 4 and the first electrode plate 10 during bonding, a part of the first surface of the element body 4 is exposed to the outside. Problems can be prevented.

Manufacturing Method of Polymer PTC Element 2 Next, a manufacturing method of the polymer PTC element 2 shown in FIGS.

(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 and flowing and the element body 4 from being deformed during the operation of the polymer PTC element.

  The thermoplastic resin is not particularly limited, but 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- Examples thereof include polyamide such as nylon, 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.

(Formation and thermocompression bonding of the first electrode plate 10 and the second electrode plate 12)
The first metal plate 10 and the second metal plate 12 are formed by punching a nickel metal plate or nickel alloy plate having a predetermined thickness.

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 body 4 may be slightly crushed in the thickness direction due to pressure, and may protrude slightly to the side of the first electrode plate 10 and the second electrode plate 12, but unnecessary portions should be easily removed. Can do.

(Formation of protective film 3)
Next, the protective film 3 is formed on the exposed surface of the element body 4 that is not covered with the first electrode plate 10 and the second electrode plate 12. 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 as described below.

  First, the plate 50 shown in FIG. 5A is immersed in a liquid reservoir (not shown) filled with resin. Next, by lifting the plate 50 from the liquid reservoir, the protective film forming resin 3 a adheres to the surface of the plate 50.

  Next, the tip of the application rod 52 is pressed against the resin 3 a attached to the surface of the plate 50. As a result, the resin 3 a adheres to the tip of the application rod 52.

  Next, as shown in FIG. 5B, the tip of the application bar 52 to which the resin 3 a is attached is pressed against the exposed surface of the element body 4. By performing this pressing operation on the entire exposed surface of the element body 4, the resin 3 a is applied to the entire exposed surface of the element body 4. Next, the resin 3a applied to the exposed surface of the element body 4 is dried to form the protective film 3 shown in FIGS.

  Note that the dimension of the tip of the application bar 52 pressed against the element body 4 is preferably equal to or smaller than the dimension of the exposed surface (side surface) of the element body 4. If the dimension of the tip of the application bar 52 is too large, the resin 3a may be applied to the surface of the first electrode plate 10. Therefore, such a problem can be prevented by setting the size of the tip of the application bar 52 to be equal to or less than the size of the exposed surface (side surface) of the element body 4.

  In this way, as shown in FIGS. 1 and 2, the polymer PTC element 2 according to the present embodiment is completed.

Assembling Method of Polymer PTC Element 2 The polymer PTC element 2 is assembled between the secondary battery cell 32 and the protection circuit 30 as shown in FIG. In order to connect the polymer PTC element 2 as shown in FIG. 1, for example, first, the second electrode plate 12 in the element 2 is spot-welded to the nickel layer 20 side of the clad plate 18.

  Next or before and after that, the aluminum layer 22 on the clad plate 18 is spot-welded in contact with the electrode terminals 34 of the secondary battery cells 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, the terminal plate 16 connected to the protection circuit 30 is spot-welded and joined to the first metal plate 10 at the terminal joining portion 9 (see FIG. 4).

  Thus, as shown in FIG. 1, the battery protection system 1 having the polymer PTC element 2, the protection circuit 30, and the secondary battery cell 32 is completed.

  In the polymer PTC element 2 according to this embodiment, as shown in FIGS. 1 and 2, the protective film 3 is formed on the exposed surface of the element body 4 that is not covered with the first electrode plate 10 and the second electrode plate 12. The

  By forming the protective film 3 on the exposed surface of the element body 4, the element body 4 can be prevented from being oxidized by oxygen in the atmosphere. Further, by preventing the element body 4 from being oxidized, an increase in the room temperature resistance value of the polymer PTC element 2 at room temperature can be prevented.

   In the polymer PTC element 2 according to this embodiment, at least the first electrode plate 10 of the first electrode plate 10 and the second electrode plate 12 has the protruding portion 7. Therefore, as shown in FIGS. 5A and 5B, when the resin 3a is applied to the exposed surface of the element body 4 to form a protective film, the exposed surface of the element body 4 will wrap around the surface of the first electrode plate 10. The protrusion 7 prevents the resin 3a. Therefore, it is possible to prevent the resin 3a from being applied to the surface of the first electrode plate 10 (the side to which the terminal plate is bonded). As a result, a protective film is not formed on the surface of the first electrode plate 10, and the first electrode plate 10 and the terminal plate 16 can be satisfactorily bonded as shown in FIG.

  Further, by preventing the resin that should be originally applied to the exposed surface of the element body 4 from being applied to the surface of the first electrode plate 10 (the surface that should not be originally coated with the resin), the element The covering thickness of the protective film 3 on the exposed surface of the main body 4 can be made sufficient. As a result, it is possible to effectively prevent the element body 4 from being oxidized. Moreover, the element main body 4 can be protected from an external impact by the protective film 3.

  In addition, since the first electrode plate 10 has the protruding portion 7, heat accompanying the joining process (soldering or welding) between the first electrode plate 10 and the terminal plate 16 is radiated from the protruding portion 7 to the atmosphere. Can be made. As a result, compared to the case where the first electrode plate 10 does not have the protrusion 7, heat conduction to the element body 4 is suppressed, and thermal deterioration of the element body 4 can be prevented.

  Moreover, when the 1st electrode plate 10 has the protrusion part 7, when joining the element main body 4 and the 1st electrode plate 10, positioning becomes easy. That is, even if a positional deviation of about the dimension of the protrusion 7 or less occurs during positioning, the element body 4 and the first electrode plate 10 are not exposed to the outside without exposing the first surface 6 of the element body 4 to the outside. Good bonding can be achieved.

  As described above, since the oxidation and thermal deterioration of the element body 4 can be prevented, the PTC element 2 according to the present embodiment can reduce power consumption and is necessary during normal use. In this case, the original function of protecting the electronic device by cutting off the current can be effectively exhibited.

  Further, in the battery protection system 1 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, 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.

  Further, as shown in FIG. 6, the tip of the protruding portion 7 may be bent toward the element body. Even in this case, the same effect as the above-described embodiment can be obtained.

  Since the tip of the projecting portion 7 is bent toward the element body side, when the resin is applied to the exposed surface of the element body 4, the resin is temporarily above the projecting portion 7 (the terminal plate in the first electrode plate 10 Even when it is a small amount of wrap around the joining side), the resin is held only at the tip (bent part) of the protrusion 7. Therefore, the resin does not wrap around the entire upper surface of the protruding portion and the vicinity of the terminal joint portion of the first electrode plate 10.

  Further, as shown in FIG. 7, a recess 72 may be formed on the surface of the protrusion 7 on the element body side. Even in this case, the same effect as the above-described embodiment can be obtained.

  Since the concave portion 72 is formed on the surface of the protruding portion 7 on the element main body side, the resin (protective film 3) is held in the concave portion 72 when the resin is applied to the exposed surface of the element main body 4. . In other words, the recess 72 serves as an anchor that prevents the resin from entering the surface of the first electrode plate 10. That is, the recess 72 can prevent the resin from flowing from the exposed surface of the element body 4 to the surface of the first electrode plate 10.

  In addition, as shown in FIG. 8, a protective film adhesion uneven portion 82 may be formed on the surface of the protruding portion 7 on the element body side. Even in this case, the same effect as the above-described embodiment can be obtained.

  By forming the protective film adhesion uneven portion 82 on the surface of the element body side of the protruding portion 7, the resin (protective film 3) becomes the protective film adhesion unevenness when the resin is applied to the exposed surface of the element body 4. The part 82 is difficult to hold and is held. Therefore, the resin can be prevented from flowing from the exposed surface of the element body 4 to the surface of the first electrode plate 10.

  Preferably, the element bonding uneven part 82 a is formed on the element bonding surface of the first electrode part 10, and the element bonding uneven part 82 a is continuous with the protective film uneven part 82.

  By forming the element bonding uneven portion 82 a on the element bonding surface 5 of the first electrode plate 10, the bonding strength (thermocompression strength) between the first electrode plate 10 and the element body 4 is improved. In addition, since the element bonding surface 5 of the first electrode plate 10 is in direct contact with the surface of the element body 4, a work such as brazing becomes unnecessary, and the manufacturing cost can be reduced. Further, by forming the element bonding uneven part 82a and the protective film uneven part 82 simultaneously in the same process, the element bonding uneven part 82a and the protective film uneven part 82 are continuous. Also in this case, the manufacturing cost can be reduced.

  In addition to the roughening process by plating film formation, the method for forming the protective film uneven part 82 and the element bonding uneven part 82a includes machines such as press treatment, surface treatment with acid, etching treatment, blast treatment, and cutting. Examples thereof include a roughening process by processing and other processes.

  In the above-described embodiment, as shown in FIG. 4, the protruding portion 7 is located on the outer periphery of the rectangular first electrode plate 10. However, as shown in FIG. 9, the protruding portion 7 is not connected to the first electrode. The plate 10 may be positioned along two opposing sides (sides 92 and 94). Even in this case, the same effect as the above-described embodiment can be obtained.

  Since the protruding portion 7 is positioned along the sides 92 and 94, when the resin is applied to the exposed surface of the element body 4 from the sides 92 and 94, the resin is removed from the exposed surface of the element body 4. It is possible to prevent wrapping around the surface of the one electrode plate 10. Further, even if resin is applied to the exposed surface of the element body 4 from the two sides (sides 96 and 98) where the protruding portion 7 is not formed in the first electrode plate 10, the resin 3 a forms the protruding portion 7. From the side of the sides 96 and 98 that are not provided, the wire wraps around below the protruding portion 7 (side of the element body 4) located along the sides 92 and 94. Therefore, the resin 3a can be prevented from wrapping around from the exposed surface of the element body 4 to the surface of the first electrode plate 10 (in the vicinity of the terminal plate bonding portion 9).

  The second electrode plate 12 of FIGS. 1 and 2 may have a protruding portion that protrudes outward from the element joint surface between the second electrode plate 12 and the element body 4. Even in this case, the same effect as the above-described embodiment can be obtained.

  That is, the resin that tries to go around from the exposed surface of the element body 4 to the surface of the second electrode plate 12 is blocked by the protrusion. Therefore, it is possible to prevent the resin from being applied to the surface of the second electrode plate 10 (the side to which the clad plate 18 is bonded). As a result, the protective film 3 is not formed on the surface of the second electrode plate 12, and the second electrode plate 12 and the clad plate 18 can be adhered and bonded satisfactorily.

  Further, the coating thickness of the protective film 3 on the exposed surface of the element body 4 can be made sufficient. As a result, it is possible to effectively prevent the element body 4 from being oxidized. Moreover, the element main body 4 can be protected from an external impact by the protective film 3.

  Furthermore, in spot welding of the second electrode plate 12 and the clad plate 18, heat conduction to the element body 4 is suppressed, and thermal deterioration of the element body 4 can be prevented.

  Moreover, when the 2nd electrode plate 12 has a protrusion part, when joining the element main body 4 and the 2nd electrode plate 12, positioning becomes easy.

  Further, as shown in FIG. 10, in the polymer PTC element 2, the entire surface of the second electrode plate 12 and the clad plate 18 may overlap. Even in this case, the same effect as the above-described embodiment can be obtained. The method for joining the second electrode plate 12 and the clad plate 18 is not particularly limited, and examples include spot welding.

  Moreover, as shown in FIG. 10, the metal foil 60 may be formed in the front and back of the element main body 4 (polymer layer which consists only of conductive polymers). The element body 4 can be formed, for example, by hot pressing the metal foil 60 on both surfaces of a sheet-like polymer layer and then punching it out to a predetermined dimension. The first electrode plate 10 and the metal foil 60 are joined via a solder layer 62. Further, the nickel layer 20 of the clad plate 18 and the metal foil 60 are joined via a solder layer 62. That is, in FIG. 10, the clad plate 18 functions as the second electrode plate. Even in this case, the same effect as the above-described embodiment can be obtained. The thickness of the metal foil 60 is thinner than the thickness of the first electrode plate 10 and is generally about 25 to 30 μm.

FIG. 1 is a cross-sectional view of a principal part showing a usage state (battery protection system) of a PTC element according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the PTC element shown in FIG. FIG. 3 is an enlarged view of a portion II shown in FIG. 2, and is a cross-sectional view of the main part showing details of the protrusion. FIG. 4 is an external view of a polymer PTC element according to an embodiment of the present invention viewed in the IV direction of FIG. 2, and shows the positional relationship between the first electrode plate, the terminal joint, the protective film, and the element body. FIG. FIG. 5A is a schematic view showing a method for applying a resin for forming a protective film on an exposed surface of an element body in a manufacturing process of a polymer PTC element according to an embodiment of the present invention. FIG. 5B is a schematic view showing a method of applying a protective film-forming resin to the exposed surface of the element body in the manufacturing process of the polymer PTC element according to one embodiment of the present invention. FIG. 6 is a cross-sectional view showing a bent tip of a protruding portion of a PTC element according to another embodiment of the present invention. FIG. 7 is a cross-sectional view showing a recess formed on the surface on the element body side in the protruding portion of the PTC element according to another embodiment of the present invention. FIG. 8 is a cross-sectional view showing the protective film adhesion irregularity and the element bonding irregularity formed on the surface of the element body side in the protruding portion of the PTC element according to another embodiment of the present invention. FIG. 9 is a schematic view showing a positional relationship among a first electrode plate, a terminal joint, a protective film forming resin, and an element body in a polymer PTC element according to another embodiment of the present invention. FIG. 10 is a cross-sectional view of a PTC element according to another embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Battery protection system 2 ... Polymer PTC element 3 ... Protective film 4 ... Element main body 5 ... Element joint surface 7 ... Projection part 10 ... 1st electrode board 12 ... 2nd electrode board 16 ... Terminal board 18 ... Cladding board 30 ... Protection Circuit 32 ... Secondary battery cell 34 ... Electrode terminal 60 ... Metal foil 62 ... Solder layer

Claims (12)

An element body having a size of 0.5 to 1.0 mm in thickness and having a resistance value that increases with a temperature rise 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,
On the exposed surface of the element body that is not covered with the first and second electrode plates, a protective film is formed with a thickness of 10 to 200 μm ,
At least the first electrode plate of said first and second electrode plates, the elements bonding surface between the element body, have a protruding portion that protrudes outward along the outer periphery, projecting height of the projecting portion The PTC element is characterized by being 20 to 500 μm with respect to the end of the element bonding surface .   The PTC element according to claim 1, wherein the element body is a conductive polymer having a positive temperature coefficient. A terminal plate for connecting to a predetermined circuit and the first electrode plate are joined at a terminal joining portion located at a portion where the terminal plate and the first electrode plate overlap,
The protective film that tries to go around from the exposed surface of the element body to the surface of the first electrode plate is blocked by the protrusion,
The PTC element according to claim 1, wherein the projecting portion is located in the vicinity of the terminal joint portion. The first electrode plate has a rectangular shape;
The PTC element according to any one of claims 1 to 3, wherein the protrusion is located along two opposing sides of the first electrode plate. Tip of the protrusion, the element is bent to the main body, the thickness of said protective film, according to claim 1-4, characterized in that larger than the projection height of the projecting portion The PTC element according to any one of the above. In the device body side of a surface of the projecting portion, Ri recesses formed tear, PTC element according to any one of claims 1 to 5, wherein the protective film in the recess is digging, that is held, characterized in Rukoto . Wherein the device body side surface of the projecting portion, PTC element according to any one of claims 1 to 6, characterized in that the uneven portion protective film adhesion is are formed. An element bonding uneven part is formed on the element bonding surface of the first electrode plate,
The PTC element according to claim 7 , wherein the uneven part for bonding an element is continuous with the uneven part for protective film. The terminal plate, PTC element according to any one of constituted claims 3-8 in the nickel terminal plate including mainly nickel. The PTC element according to any one of claims 1 to 9 , wherein the second electrode plate is bonded to a clad plate in which two or more kinds of plate materials are laminated. The front and back surfaces of the element body, the metal foil Yes laminated, PTC element according to any one of claims 1 to 10, for each metal foil, said first and second electrode plates are joined . The PTC element according to any one of claims 1 to 11 ,
A protection circuit electrically connected to the first electrode plate of the PTC element;
A battery protection system comprising: a battery electrically connected to the second electrode plate of the PTC element.

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