JP2008041724A - Manufacturing method of overcurrent protecting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of an overcurrent-protecting element which improves the insulation properties by proper trip characteristics, when the temperature is raised higher than the room temperature by the short-circuiting of an electronic circuit, or the like. <P>SOLUTION: A sheet layer 1 is pinched by a pair of conductive plates 2, and the sheet layer 1 is formed of high molecular macromolecule matrix and a plurality of conductive particles contained in the high molecular macromolecule matrix. The surface of respective conductive particles is partially coated by an organic material that is different from the high polymer macromolecule matrix and moreover that does not have compatibility. The surface of respective conductive particles is partially coated by the organic material that is high in expansion coefficient, whereby superior trip characteristics can be obtained at short-circuiting of the electronic circuit, and can permit improvement in the insulation properties. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an overcurrent protection element that is built in an electric device / electronic device and protects a circuit or a component thereof.

  A conventional overcurrent protection element, although not shown, is formed by including a sheet layer in which conductive particles are blended in a polymer matrix and a pair of conductive plates sandwiching the sheet layer, and is a self-control heating element Or as a temperature sensor incorporated in an electronic circuit such as a cellular phone. As the polymer matrix of the sheet layer, polyethylene resin or the like is used, and as the conductive particles, carbon particles or graphite having a large conductivity, DBP oil absorption, large structure, etc. are used.

  Such an overcurrent protection element, when the temperature rises above room temperature due to a short circuit of an electronic circuit, etc., shows a trip characteristic and rapidly increases the resistance value, thereby restricting the overcurrent to be applied to the electronic circuit and its semiconductor element. Protect. Conversely, when the temperature decreases, the original resistance value is restored (see Patent Documents 1 and 2).

In addition, when this type of overcurrent protection element is connected in series to an electronic circuit, (1) the resistance value at room temperature is sufficiently low, and (2) the resistance value at room temperature and the change in resistance value during operation. It is required as a characteristic that the rate is sufficiently large and (3) the change in resistance value during repeated operation is small.
U.S. Pat. No. 3,243,753 JP 2005-197660 A

  The conventional overcurrent protection element is configured as described above, and the conductive particles are merely blended in the polymer matrix, so that it does not show a good trip characteristic when the electronic circuit is short-circuited, and improves the insulation. There is a problem that can not be.

  The present invention has been made in view of the above, and provides a method of manufacturing an overcurrent protection element that can improve insulation by good trip characteristics when the temperature rises above room temperature due to a short circuit of an electronic circuit or the like. The purpose is to do.

In the present invention, in order to solve the above problems, a plurality of conductive particles and an organic material are heated and kneaded at a temperature equal to or higher than the softening point of the organic material, and a part of each conductive particle is covered with the organic material. A plurality of conductive particles coated with a polymer matrix and a polymer matrix are pressure-kneaded to prepare a kneaded product. The kneaded product is formed into a sheet layer, and the sheet layer is sandwiched between a plurality of conductors and heated. And then irradiating the sheet layer and the plurality of conductors with radiation.
In addition, 10-30 wt% of organic materials can be blended with respect to the weight of the plurality of conductive particles, and the organic materials can be made incompatible with the polymer matrix.

Further, the polymer matrix can be a thermoplastic resin, and each conductive particle can be a carbon particle.
Further, the organic material can be modified elastomer EPR, SBR resin, or SBS resin.
Moreover, it is preferable to mix and knead | mix 36-57 wt% of several electroconductive particle with respect to the weight of a polymer matrix.

  The sheet layer is sandwiched between a plurality of conductors, and the sheet layer includes a polymer matrix and a plurality of conductive particles contained in the polymer matrix, and each conductive particle A part of the substrate may be covered with an organic material incompatible with the polymer matrix.

According to the present invention, when the temperature rises above room temperature due to a short circuit of an electronic circuit or the like, there is an effect that the insulating property can be improved by good trip characteristics.
Also, if the organic material is modified elastomer EPR, SBR resin, or SBS resin, when the temperature rises due to a short circuit of the electronic circuit, etc., the organic material expands and separates the conductive particles, so good trip characteristics are achieved. Obtainable.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, an overcurrent protection element in the present embodiment sandwiches a sheet layer 1 between a pair of conductive plates 2 to form a sheet layer. 1 is formed from a polymer matrix and a plurality of conductive particles contained in the polymer matrix, and the surface of each conductive particle is different from the polymer matrix and is not compatible with the organic material. So that it is partially covered.

  The sheet layer 1 is thinly formed into an arbitrary shape such as a plane rectangle, a polygon, a circle, or an ellipse. As the polymer matrix of the sheet layer 1, a thermoplastic resin is used, and specifically, a polyethylene resin, an EBA resin, or the like is used. Moreover, as each electroconductive particle, the electroconductive organic material, specifically, the cheap carbon particle which is excellent in electroconductivity is used.

  The organic material is a material that does not react with the polymer matrix after being covalently bonded to each conductive particle, specifically, a modified elastomer EPR (maleic acid modified EPR), SBR resin, or SBS having a high coefficient of thermal expansion. Resin or the like is used.

  For example, a pair of nickel foil and copper foil having the same size as the sheet layer 1 is used as the pair of conductive plates 2, and lead wires 3 for connecting an electronic circuit of a mobile phone are formed on the surface of each conductive plate 2. On the back surface of each conductive plate 2 that is connected and contacts the sheet layer 1, rough unevenness that exhibits an anchor effect is selectively formed by a roughening treatment.

  In the above, when manufacturing an overcurrent protection element, first, the polymer matrix, the conductive particles, and the organic material that is not compatible with the polymer matrix are separately pulverized separately by a pulverizer such as a jet mill. Are put into a batch type pressure kneader in which a plurality of conductive particles and an organic material are heated to a predetermined temperature, and the plurality of conductive particles and the organic material are heated to a temperature equal to or higher than the softening point of the organic material (for example, 180 And the surface of each conductive particle is partially covered with an organic material.

  At this time, the blending amount of the plurality of conductive particles and the organic material is adjusted so that each conductive particle can be partially coated with the organic material. Specifically, the organic material is blended in an amount of 10 to 30 wt%, preferably 12 to 28 wt%, based on the weight of the plurality of conductive particles. The blending amount of the organic material is set in the range of 10 to 30 wt%. When the amount is less than 10 wt, the trip characteristic is deteriorated. On the other hand, when it exceeds 30 wt, the conductivity is impaired and the resistance value is more than necessary. Because it rises to.

  In addition, it is necessary to pay attention to the fact that a plurality of conductive particles and an organic material are not simply heated and kneaded, and excellent insulation cannot be obtained unless heated and kneaded at a temperature higher than the softening point of the organic material. There is.

  When the surface of each conductive particle is partially covered with an organic material in this way, a polymer matrix is newly added to a pressure kneader and a plurality of conductive particles and the polymer matrix are pressure-kneaded to prepare a kneaded product. To do. At this time, the polymer matrix and the plurality of conductive particles are blended in an amount of 36 to 57 wt% with respect to the weight of the polymer matrix. The reason why the blending amount of the plurality of conductive particles is in the range of 36 to 57 wt% is that when the temperature falls outside this range, the original resistance value is not easily restored when the temperature is lowered, and the resistance value is not stable. is there.

  Next, the kneaded material is set on a calendering machine and formed into a thin sheet layer 1. The sheet layer 1 is sandwiched between a pair of conductive plates 2 and heated and pressed by a press molding machine. A pair of conductive plates 2 are irradiated with inexpensive γ-rays, electron beams, X-rays or the like using an electron beam crosslinking device to crosslink the polymer, and then lead wires 3 are connected to the surface of each conductive plate 2. Then, an overcurrent protection element can be manufactured.

  According to the above, the conductive particles are not simply blended in the polymer matrix, but the surface of each conductive particle is partially coated with an organic material having a high coefficient of thermal expansion. Swells to separate the conductive particles from each other, good trip characteristics can be obtained, and the insulation can be remarkably improved. In addition, since the surface of each conductive particle is not entirely coated with an organic material but is partially coated to expose the remainder, an excellent low resistance value can be obtained at room temperature.

  Note that the overcurrent protection element of the present embodiment may be used for a battery of a mobile phone, but is not limited to this, for example, an inverter, a fire alarm, an automobile, a switching power supply, a control device, etc. Can also be used.

Examples of the method for manufacturing an overcurrent protection element according to the present invention will be described below together with comparative examples.
Example 1
First, a polymer matrix (polyethylene: made by Idemitsu Petrochemical Co., Ltd., trade name 548B), 37.4 wt%, conductive particles (made by Colombian Carbon, trade name Raven410U), 56.6 wt%, and a polymer matrix and phase Insoluble organic materials (maleic acid-modified EPR: JSR, trade name: T-7741P) of 6.0 wt% were separately pulverized by a jet mill and adjusted to a particle size of 16 to 100 mesh.

  When pulverization is completed in this way, a plurality of conductive particles and an organic material are put into a batch type pressure kneader heated to a temperature of 180 ° C., and the plurality of conductive particles and the organic material are brought to a temperature higher than the softening point of the organic material. The surface of each conductive particle was partially covered with an organic material by heating and kneading for 30 minutes at a temperature.

Next, a polymer matrix was newly added into a heated pressure kneader, and a plurality of conductive particles and the polymer matrix were pressure-kneaded for 20 minutes at 180 ° C. to prepare a kneaded product. When the kneaded material was prepared, the kneaded material was set on a calendering machine to form a sheet layer having a thickness of 50 μm, and the sheet layer was sandwiched between a pair of conductive plates and heated and pressed by a press molding machine. As each conductive plate, a nickel foil having a roughness Ra of 2.0 μm and a thickness of 125 μm was used. The press molding machine was heated and pressed under the conditions of heating at 250 ° C. and pressing at 10 kgf / cm ² .

  The sheet layer integrated with a total thickness of 250 μm and the pair of conductive plates are irradiated with a 10 MRad electron beam by an electron beam cross-linking device to cross-link the polymer, and then lead wires are connected to the surface of each conductive plate. Thus, an overcurrent protection element was manufactured.

Example 2
Polymer matrix (polyethylene: Idemitsu Petrochemical Co., Ltd., trade name 548B) 34.4 wt%, conductive particles (Colombian Carbon, trade name Raven410U) 56.6 wt%, and organic material incompatible with polymer matrix ( Maleic acid-modified EPR: JSR, trade name: T-7741P) 9.0 wt% was separately pulverized by a jet mill and adjusted to a particle size of 16 to 100 mesh. The other parts were the same as in Example 1.

Example 3
Polymer matrix (polyethylene: Idemitsu Petrochemical, trade name 548B) 31.4 wt%, conductive particles (Colombian Carbon, trade name Raven410U) 56.6 wt%, and organic material incompatible with polymer matrix ( Maleic acid-modified EPR: JSR, trade name T-7741P) 12.0 wt% was separately pulverized by a jet mill and adjusted to a particle size of 16 to 100 mesh. The other parts were the same as in Example 1.

Example 4
Polymer matrix (polyethylene: Idemitsu Petrochemical Co., Ltd., trade name 548B) 28.4 wt%, conductive particles (Colombian Carbon, trade name Raven410U) 56.6 wt%, and organic material incompatible with the polymer matrix ( Maleic acid-modified EPR: JSR, trade name T-7741P) 15.0 wt% was separately pulverized by a jet mill to adjust the particle size to 16 to 100 mesh. The other parts were the same as in Example 1.

Example 5
Polymer matrix (polyethylene: Idemitsu Petrochemical Co., Ltd., trade name 548B) 26.4 wt%, conductive particles (Colombian Carbon, trade name Raven410U) 56.6 wt%, and organic material incompatible with the polymer matrix ( Maleic acid-modified EPR: JSR, trade name T-7741P) 17.0 wt% was separately pulverized by a jet mill and adjusted to a particle size of 16 to 100 mesh. The other parts were the same as in Example 1.

Comparative Example 1
First, a polymer matrix (polyethylene: made by Idemitsu Petrochemical Co., Ltd., trade name 548B), 38.4 wt%, conductive particles (made by Colombian Carbon, trade name Raven410U) 56.6 wt%, and a polymer matrix and phase Insoluble organic materials (maleic acid-modified EPR: JSR, trade name: T-7741P) of 5.0 wt% were separately pulverized by a jet mill to adjust the particle size to 16 to 100 mesh.

  When the pulverization is completed in this way, the polymer matrix, the conductive particles, and the organic material are mixed and stirred by a super mixer (manufactured by Kawata), and then put into a pressure kneader heated to a temperature of 180 ° C. A kneaded product was prepared by kneading organic materials.

Next, the prepared kneaded material was set on a calendering machine to form a sheet layer having a thickness of 50 μm, and the sheet layer was sandwiched between a pair of conductive plates and heated and pressed by a press molding machine. As each conductive plate, a nickel foil having a roughness Ra of 2.0 μm and a thickness of 125 μm was used. The press molding machine was heated and pressed under the conditions of heating at 250 ° C. and pressing at 10 kgf / cm ² .

  The sheet layer integrated with a total thickness of 250 μm and the pair of conductive plates are irradiated with a 10 MRad electron beam by an electron beam cross-linking device to cross-link the polymer, and then lead wires are connected to the surface of each conductive plate. Thus, an overcurrent protection element was manufactured.

Comparative Example 2
Polymer matrix (polyethylene: Idemitsu Petrochemical, trade name 548B) 23.4 wt%, conductive particles (Colombian Carbon, trade name Raven410U) 56.6 wt%, and organic material incompatible with polymer matrix ( Maleic acid-modified EPR: JSR, trade name T-7741P) 20.0 wt% was separately pulverized by a jet mill and adjusted to a particle size of 16 to 100 mesh. The other parts were the same as those in Comparative Example 1.

Comparative Example 3
A polymer matrix (polyethylene: Idemitsu Petrochemical, trade name 548B) 43.4 wt% and conductive particles (Colombian Carbon, trade name Raven410U) 56.6 wt% were separately pulverized by a jet mill, respectively. The particle size was adjusted to 100 mesh. The other parts were the same as those in Comparative Example 1.

Measuring the characteristics of the overcurrent protection element Connect one lead of the overcurrent protection element to a resistance measuring instrument to measure the initial resistance value, and place this overcurrent protection element in the oven to measure the temperature-resistance curve. Started. Specifically, the resistance value is measured by increasing the temperature sequentially from 20 ° C. every 10 ° C., and the temperature is increased to 160 ° C. (resistance value at the time of trip). The temperature was lowered to 20 ° C. and the measurement was continued. The resistance value when the temperature returned to 20 ° C. was called a relaxation resistance value.

  After manufacturing the overcurrent protection element and measuring the characteristics, Table 1 shows the composition of the conductive particles and the organic material, the initial resistance value, the 160 ° C. resistance value, the relaxation resistance value, and the relaxation rate.

  As is clear from Table 1, the overcurrent protection element of the example is a practically excellent element having a low initial resistance value, a high resistance value at 160 ° C. that is a resistance value at the time of trip, and a low relaxation resistance value. Confirmed.

  On the other hand, the overcurrent protection element of the comparative example has the same initial resistance value as that of the example in which the same amount of conductive particles is blended, but the resistance value at 160 ° C. is the resistance value at the time of trip. It is low and the relaxation rate is high, so it can be seen that it exceeds 120%, which is the generally used limit of relaxation rate. FIG. 2 is a graph of this, and according to FIG. 2, the PTC characteristics are shown to be good in the range following the embodiment, but the PTC characteristics rapidly deteriorate when deviating from the range. I can know.

  As described above, according to the embodiment, since the surface of each conductive particle is partially covered with an organic material having a large thermal expansion, when the temperature of the overcurrent protection element is increased, a plurality of conductive particles are not separated. It is possible to obtain a good trip state and maintain a value close to the initial resistance value when the resistance is relaxed, and a function as a good overcurrent protection element can be expected. There was found.

It is explanatory drawing which shows typically the overcurrent protection element in embodiment of the manufacturing method of the overcurrent protection element which concerns on this invention. It is a graph which shows the PTC characteristic of the overcurrent protection element in the Example of the manufacturing method of the overcurrent protection element which concerns on this invention.

Explanation of symbols

1 Sheet layer 2 Conductive plate 3 Lead wire

Claims (4)

  A plurality of conductive particles and an organic material are heated and kneaded at a temperature equal to or higher than the softening point of the organic material, and a part of each conductive particle is coated with the organic material. A kneaded product is prepared by pressure-kneading a molecular matrix, and the kneaded product is formed into a sheet layer, and the sheet layer is sandwiched between a plurality of conductors and heated and pressurized, and then the sheet layer and the plurality of conductors are formed. And a method of manufacturing an overcurrent protection element.   The method for producing an overcurrent protection element according to claim 1, wherein the organic material is blended in an amount of 10 to 30 wt% with respect to the weight of the plurality of conductive particles, and the organic material is incompatible with the polymer matrix.   The method for producing an overcurrent protection element according to claim 1 or 2, wherein the polymer matrix is a thermoplastic resin, and the conductive particles are carbon particles.   The method for producing an overcurrent protection element according to claim 1, 2, or 3, wherein the organic material is a modified elastomer EPR, SBR resin, or SBS resin.

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