CN116130185A - Overcurrent protection element with high lightning-proof capability - Google Patents
Overcurrent protection element with high lightning-proof capability Download PDFInfo
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- CN116130185A CN116130185A CN202211593487.XA CN202211593487A CN116130185A CN 116130185 A CN116130185 A CN 116130185A CN 202211593487 A CN202211593487 A CN 202211593487A CN 116130185 A CN116130185 A CN 116130185A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/12—Overvoltage protection resistors
Abstract
The invention relates to a resistance positive temperature effect conductive composite material with high lightning strike resistance and an overcurrent protection element. The positive temperature effect electric conduction composite material comprises a polymer base material, an electric conduction filler and a heat conduction filler, wherein the polymer base material accounts for 20-75% of the volume fraction of the electric conduction composite material; the conductive filler accounts for 25-80% of the volume fraction of the conductive composite material; the heat conducting filler is preferably a rod-shaped heat conducting material with microcosmic structure, accounting for 0.1-70% of the volume fraction of the electric conducting composite material, and forms a heat conducting network in the electric conducting composite material. The heat conducting network formed by the heat conducting filler has ultrahigh heat conducting efficiency, and can relieve local overheating, so that the resistance positive temperature effect conductive composite material has higher capability of resisting outdoor lightning strokes in a circuit.
Description
Technical Field
The present invention relates generally to polymer-based resistive devices or apparatus having positive temperature coefficient resistivity, and more particularly to overcurrent protection elements having high lightning protection capability.
Background
The high-molecular PTC is a widely used overcurrent protection element, and when an abnormal increase in current occurs in a circuit, it can be switched from a low-resistance state to a high-resistance state in a short time by means of self-heating, thereby turning off the current in the circuit and protecting other elements in the circuit. In general, a high polymer-based PTC has an upper limit on voltage or current that can be borne, and when the voltage or current exceeds a certain threshold value, the PTC will burn on fire, thereby losing the protection function and even damaging the circuit, so that the high polymer-based PTC is generally only applied to a relatively stable circuit system. When the circuit is subjected to extreme conditions such as lightning stroke and the like, the circuit can usually last for tens of microseconds, and common components can allow the conditions to happen, but instantaneous high current is enough to cause the PTC to be locally mistakenly protected, so that burst damage occurs.
The research on the action mechanism of the macromolecule-based PTC shows that when the PTC acts, the inside of the chip does not uniformly heat, and the temperature of the inside is higher than the temperature of the surface, so that the PTC is non-uniformly heated. Under the general action condition, heat generated by a certain part can be diffused to an adjacent area and an external space, and heat accumulation can not occur, however, when the instantaneous current is too high, the heat generated by the part can possibly not reach and be diffused to other areas, and the accumulated instantaneous energy can cause bursting of heating points in the PTC. From the damage of the PTC after a lightning strike, the point of failure usually occurs only in a small part, which indicates that energy does accumulate at this weak location.
In order to prevent the PTC from being damaged by lightning strike, it is necessary to improve the heat conductive environment inside the PTC core to mitigate energy accumulation, and some heat conductive filler with good heat conductivity may be added. However, excessive use of the filler can raise the resistance, so that the action burning is easier to occur when lightning strike occurs, and the heat-conducting filler is less in use and is difficult to have the effect of dispersing heat. According to the invention, the heat conduction filler with good heat conductivity is selected, preferably the heat conduction filler with a microcosmic rod shape, a heat conduction network can be formed with a small amount of heat conduction filler, the reliability of the PTC in a lightning stroke simulating environment can be improved, and the PTC can be applied to circuits with lightning stroke risks.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a positive temperature coefficient of resistance composite material with lightning resistance.
Another object of the present invention is to provide an overcurrent protection element prepared by using the above-mentioned ptc-resistive composite material, which can be applied in a circuit scenario where there is a risk of lightning strike, and which can be used in a circuit without damaging the device when it is struck by lightning.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
a resistive positive temperature effect conductive composite material in which a composite film material of a thermally conductive filler, electrically conductive particles and a polymer capable of forming a thermally conductive network is present.
Wherein the conductive filler is used as a main conductive network and accounts for 25% -80% of the conductive composite material, and the conductive material comprises one or more of carbon black, graphite, conductive ceramic powder, metal powder and the like.
Wherein the high molecular material accounts for about 20% -75% of the conductive composite material, and comprises one or more materials of polyethylene, polyvinylidene fluoride, polypropylene, polytetrafluoroethylene, polyamide, polyimide, polycarbonate, polyethylene-propylene copolymer and the like.
Wherein the heat conducting filler accounts for about 0.1% -70% of the electric conducting composite material and is one or more materials of magnesium hydroxide, magnesium oxide, aluminum hydroxide, aluminum oxide, aluminum nitride, silicon carbide and the like, wherein the heat conducting filler with a bar-shaped microstructure is preferable.
The selected heat conducting filler can be dispersed in the electric conduction composite material to form a heat conducting network, so that the energy of the heat concentration point can be timely dispersed to a certain extent by utilizing the excellent heat conducting efficiency of the heat conducting network, and the device is protected from being damaged.
The conductive composites may contain other components such as antioxidants, radiation crosslinking agents (often referred to as radiation accelerators, crosslinking agents or crosslinking accelerators, e.g., triallyl isocyanurate), coupling agents, dispersants, stabilizers, nonconductive fillers (e.g., magnesium hydroxide, calcium carbonate), flame retardants, arc inhibitors, or other components. These components typically account for up to 15% of the total volume of the conductive composite.
The conductive composite material with high lightning stroke resistance and the overcurrent protection element prepared from the conductive composite material can be prepared according to the following method:
the polymer, the electrically conductive filler and the thermally conductive filler are put into a mixing device and melt-mixed at a temperature higher than the melting temperature of the polymer. The mixing apparatus may be an internal mixer, an open mill, a single screw extruder or a twin screw extruder. And then the melted and mixed polymer is processed into a sheet material through extrusion molding, compression molding or calendaring molding. In general, the thickness of the polymer sheet is 0.01 to 3.0mm, preferably 0.05 to 2.0mm, more preferably 0.1 to 1.0mm for the convenience of processing.
The forming method of the composite product is to compound metal electrode plates on two sides of a composite material sheet, and the method for compounding the metal electrode plates on two sides of the composite material sheet comprises the steps of die pressing the composite or directly compounding the electrode plates with the polymer sheet through a roller after the extrusion and in a molten state. Suitable materials for the metal electrode sheet include nickel, copper, aluminum, zinc and their composites, such as copper foil, nickel foil, single-sided nickel-plated copper foil, double-sided nickel-plated copper foil, and the like.
The stability of the ptc-resistive conductive composite can be generally improved by means of crosslinking and/or heat treatment. The crosslinking may be chemical crosslinking or irradiation crosslinking, for example, crosslinking accelerators, electron beam irradiation or Co 60 Irradiation is performed. The irradiation dose required for the overcurrent protection element is generally less than 100Mrad, preferably 1 to 50Mrad, more preferably 1 to 20Mrad. The heat treatment may be annealing, thermal cycling, high and low temperature alternation, for example +85℃/-40 ℃. The temperature environment for the annealing may be any temperature below the decomposition temperature of the polymer substrate, such as high temperature annealing above the melting temperature of the polymer substrate and below the polymerizationLow temperature annealing of the melt temperature of the substrate.
The resistive positive temperature effect conductive composite material provided by the invention can be prepared into the SMD patches of the encapsulation types such as 0201, 0402, 0805, 1206, 1812, 2920 and the like in a PCB processing mode. The PTC element manufactured by the method can improve the performance of the PTC element in a lightning stroke simulation experiment, such as an SMD patch packaged by 1812, and can bear the lightning stroke simulation experiment of 20 mu s/2kV when the resistance is 30mΩ.
Advantages of the PTC core of the present invention compared to existing polymer-based PTC core materials include:
(1) According to the invention, the heat conducting filler is utilized to form a heat conducting network in the core material, so that the heat of the weak point can be quickly conducted to other areas when the PTC element is struck by lightning, and the PTC element is protected from damage;
(2) The core material provided by the invention is easy to obtain, can be prepared by the existing processing technology, and has low cost and good effect.
Drawings
FIG. 1 is a schematic illustration of a conductive composite of the present invention;
fig. 2 is an SEM microstructure of the heat conductive filler 1 and the heat conductive filler 2, wherein the heat conductive filler 1 of fig. 2A is spherical and the heat conductive filler 2 of fig. 2B is rod-shaped.
Detailed Description
The invention provides a scheme capable of improving the reliability of the high polymer based PTC in a circuit scene with lightning stroke risk. The heat conducting filler which is easy to form a heat conducting network is added, so that the PTC core material has higher heat conducting efficiency, and heat generated by weak points of the PTC when the PTC is subjected to short lightning stroke can be rapidly dispersed to the periphery, thereby relieving energy accumulation of the weak points and ensuring that the PTC is not burnt and damaged.
The heat conductive fillers 1 and 2 in the examples are the same substances, and their heat conductivity coefficients are 33-36W/m.K, but the micro topography shapes are different. The thermal conductivity of the polyethylene/carbon black composite is typically 1W/m.K.
The invention will be further illustrated by the following specific examples
Example 1
An overcurrent protection element adopts a common PTC formula, and the components are shown in table 1:
in Table 1, the polymer was a high density polyethylene having a melting temperature of 134℃and a density of 0.953g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The conductive particles are furnace carbon black with the particle size of 30-34 nm, and no heat conducting filler is added.
The preparation method of the positive temperature coefficient composite material and the overcurrent protection element by taking the materials in the table 1 as the formula comprises the following steps: grinding the polymer, mixing the polymer with the conductive filler in a dry state in a mixer for 30min, adding the mixture into a double-screw extruder, and extruding and granulating after melt mixing at 180-220 ℃ to form the conductive composite material with positive temperature effect of resistance;
adding the conductive composite material granules with positive temperature effect of resistance into another double-screw extruder, extruding the conductive composite material into a conductive composite material sheet in a molten state through an extruder die head at 180-220 ℃, and tightly combining two metal electrode sheets which are vertically symmetrical through hot pressing and traction of a hot pressing roller, wherein the conductive composite material sheet is cut into a PTC core material with proper size; finally, the step of obtaining the product,
the composite PTC core is processed into a surface mount type overcurrent protection element, in this embodiment a small size 1812 package, by a series of PCB processes such as etching, lamination, drilling, copper deposition, tin plating, dicing, etc.
The surge testing method of the product comprises the following steps: and welding the overcurrent protection element on a PCB with a corresponding size in a reflow welding mode, welding two leads at two ends of the PCB, generating required high voltage through a lightning surge generating device, and adopting a waveform of 1.2/50-8/20 mu s and a waveform of L1-L2 (2Ω+18 mu F) for 30 s+/-5 times. Starting from 1kV, if the product does not burst, the test is restarted by +0.1KV until the product bursts, and recording the highest voltage when the product does not burst.
Initial resistance R 0 20.2mΩ, working resistance R against lightning surge 1 38.7mΩ, lightning strike rating 1.5kV.
Example 2
An overcurrent protection element has the composition shown in table 1:
in Table 1, the polymer was a high density polyethylene having a melting temperature of 134℃and a density of 0.953g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The conductive particles are furnace carbon black with the particle size of 30-34 nm and are microscopically spherical heat-conducting filler 1.
The preparation method of the positive temperature coefficient composite material and the overcurrent protection element by taking the materials in the table 1 as the formula comprises the following steps: grinding the polymer, mixing the polymer with the conductive filler and the heat-conducting filler 1 in a mixer in a dry state for 30min, adding the mixture into a double-screw extruder, and extruding and granulating after melt mixing at 180-220 ℃ to form the conductive composite material with the positive temperature effect of resistance;
adding the conductive composite material granules with positive temperature effect of resistance into another double-screw extruder, extruding the conductive composite material into a conductive composite material sheet in a molten state through an extruder die head at 180-220 ℃, and tightly combining two metal electrode sheets which are vertically symmetrical through hot pressing and traction of a hot pressing roller, wherein the conductive composite material sheet is cut into a PTC core material with proper size; finally, the step of obtaining the product,
the composite PTC core is processed into a surface mount type overcurrent protection element, in this embodiment a small size 1812 package, by a series of PCB processes such as etching, lamination, drilling, copper deposition, tin plating, dicing, etc.
The surge test method of the product was the same as in example 1.
Initial resistance R 0 21.8mΩ, working resistance R against lightning surge 1 40.2mΩ, lightning strike rating 1.7kV.
Example 3
The composition of the overcurrent protection element is shown in table 1, and the composition is the same as that of example 2, except that the added heat conducting filler has different microcosmic morphologies, and the heat conducting filler 1 and the heat conducting filler 2 are the same substance, but have different microcosmic morphologies.
In Table 1, the polymer was a high density polyethylene having a melting temperature of 134℃and a density of 0.953g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The conductive particles are furnace carbon black with the particle size of 30-34 nm and are bar-shaped heat conducting filler 2 in a microcosmic mode.
The preparation method of the positive temperature coefficient composite material and the overcurrent protection element by taking the materials in the table 1 as the formula comprises the following steps: grinding the polymer, mixing the polymer with the conductive filler and the heat-conducting filler 2 in a mixer in a dry state for 30min, adding the mixture into a double-screw extruder, and extruding and granulating after melt mixing at 180-220 ℃ to form the conductive composite material with the positive temperature effect of resistance;
adding conductive composite material granules with positive temperature effect of resistance into another double-screw extruder, extruding the conductive composite material into conductive composite material sheets in molten state through an extruder die head at 180-220 ℃, wherein two metal electrode sheets which are vertically symmetrical in the conductive composite material sheets are closely combined together through hot pressing by traction and hot pressing of a hot pressing roller, and the conductive composite material sheets are cut into PTC core materials with proper size; finally, the step of obtaining the product,
the composite PTC core is processed into a surface mount type overcurrent protection element, in this embodiment a small size 1812 package, by a series of PCB processes such as etching, lamination, drilling, copper deposition, tin plating, dicing, etc.
The surge test method of the product was the same as in example 1.
Initial resistance R 0 21.3mΩ, working resistance R against lightning surge 1 40.4mΩ, lightning strike rating 2.0kV.
Comparative example 1
The overcurrent protection element has the composition shown in table 1, and the ingredients of examples 2 and 3 are different from those of examples 1 to 3 in that no heat conductive filler is added, and the processing steps and the process requirements are the same as those of examples 1 to 3. The resulting surface mount over-current protection device is a small size 1812 package.
Initial resistance R 0 18.2mΩ, working resistance R against lightning surge 1 35.8mΩ, lightning strike rating 1.8kV.
Results and discussion:
example 1 is a general PTC formulation in which example 2 and example 3 are added with a thermally conductive filler 1 and a thermally conductive filler 2 having a spherical and rod-like microstructure, respectively, based on example 1, and comparative example 1 differs from example 1 in that 3 parts of a conductive filler is added in the same amount as in example 2 and example 3. From the comparison of example 1 and comparative example 1, it is known that the surge resistance of the product is closely related to the product resistance, and the lower the resistance is, the higher the lightning surge level is. Comparison of example 1 with example 1 and example 2 shows that the addition of the thermally conductive filler increases the electrical resistance of the product significantly.
As is clear from comparison of examples 1, 2 and 3, the resistances of the materials are not different, the influence of the increase of the resistance on the surge resistance level can be eliminated, the lightning surge resistance level of the product of the example 1 is 1.5kV, after the heat conducting filler is added, the lightning surge resistance level of the product of the example 2 is improved to 1.7kV, and the lightning surge resistance level of the product of the example 3 is further improved to 2.0kV. Further, in comparative example 3 and comparative example 1, the resistance of example 3 was higher, but the surge resistance was rather higher after the heat conductive filler was added. Therefore, the addition of the heat conducting filler can improve the lightning surge resistance level of the overcurrent protection element, and the improvement of the micro-morphology rod-shaped heat conducting filler on the lightning surge level is stronger than that of the micro-morphology spherical heat conducting filler, and the heat conducting filler is considered to be easier to form a heat conducting network because the specific surface area of the rod-shaped material is higher than that of the spherical material, so that the local instantaneous heat generated during lightning can be more effectively dispersed.
The disclosure and features of the present invention have been disclosed as being significant in the foregoing, it should be noted that the features of the present invention may be more pertinent than those disclosed herein. Accordingly, the scope of the present invention should not be limited to the disclosure of the embodiments, but should include various alternatives and modifications without departing from the invention, and be covered by the claims of the present invention.
Claims (8)
1. A resistive positive temperature effect conductive composite comprising a polymeric substrate and a conductive filler, characterized by: the heat conducting composite material also comprises a heat conducting filler with the heat conducting coefficient of 33-36W/m.K, wherein the heat conducting filler is uniformly dispersed in the heat conducting composite material to form a heat conducting network so as to lighten local overheating, resist instantaneous large current caused by outdoor lightning strike in a circuit and achieve overcurrent protection.
2. The resistive positive temperature effect conductive composite of claim 1, wherein: the conductive filler forms a conductive network on the polymer base material, and accounts for 25% -80% of the conductive composite material, and comprises one or more of carbon black, graphite, conductive ceramic powder, metal powder and the like.
3. The resistive positive temperature effect conductive composite of claim 1, wherein: the polymer base material is a high polymer material and accounts for 20% -75% of the conductive composite material, and comprises one or more of polyethylene, polyvinylidene fluoride, polypropylene, polytetrafluoroethylene, polyamide, polyimide, polycarbonate, polyethylene-propylene copolymer and the like.
4. The resistive positive temperature effect conductive composite of claim 1, comprising: the micro-morphology of the heat conducting filler is rod-shaped heat conducting filler, and the micro-morphology of the heat conducting filler accounts for 0.1% -70% of the heat conducting composite material, and the heat conducting filler comprises one or more materials of magnesium hydroxide, magnesium oxide, aluminum hydroxide, aluminum oxide, aluminum nitride and silicon carbide.
5. The resistive positive temperature effect conductive composite of claim 1, wherein: the conductive composite material also contains other additives, accounting for 15 percent of the total volume of the conductive composite material, including antioxidants, radiation crosslinking agents, crosslinking agents or crosslinking promoters, coupling agents, dispersing agents, stabilizers, non-conductive fillers, flame retardants, arc inhibitors or other components.
6. An overcurrent protection element prepared from the resistive positive temperature effect conductive composite material according to any one of claims 1 to 5, wherein the overcurrent protection element is formed by sandwiching a resistive positive temperature effect conductive composite material layer by two metal electrode sheets, and the metal electrode sheets are tightly combined with the conductive composite material having the resistive positive temperature effect.
7. A method of manufacturing an overcurrent protection element according to claim 6, comprising the steps of:
putting the polymer, the electric conduction filler and the heat conduction filler into mixing equipment, and carrying out melt mixing under the condition of being higher than the melting temperature of the polymer; then, the process is carried out,
processing the melted and mixed polymer into a sheet with the thickness of 0.01-3.0 mm through extrusion molding, compression molding or calendaring molding;
the method for compounding the metal electrode plates comprises the steps of molding the composite material sheet material or directly compounding the electrode plates with the polymer sheet material through a roller after the polymer sheet material is extruded and is still in a molten state; finally, the step of obtaining the product,
typically crosslinking and/or heat treatment improves the stability of the ptc resistive conductive composite sheet;
the SMD patch of the package type is prepared by a PCB processing mode.
8. The method of manufacturing an overcurrent protection element according to claim 7, wherein the manufacturing steps are as follows:
1) The polymer is 28wt% high density polyethylene with a melting temperature of 134 ℃ and a density of 0.953g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The conductive filler is 33wt% of furnace carbon black with the particle size of 30-34 nm; the microcosmic heat-conducting filler is 5wt% of the rod-shaped heat-conducting filler, the microcosmic heat-conducting filler 1 is spherical and the microcosmic heat-conducting filler 2 is different in microcosmic appearance;
2) Grinding the polymer, mixing the polymer with the conductive filler and the heat conductive filler in a mixer in a dry state for 30min, adding the mixture into a double-screw extruder, and extruding and granulating after melt mixing at 180-220 ℃ to form the conductive composite material with the positive temperature effect of resistance;
3) Adding the conductive composite material granules with positive temperature effect of resistance into another double-screw extruder, extruding the conductive composite material into a conductive composite material sheet in a molten state through an extruder die head at 180-220 ℃, and tightly combining two metal electrode sheets which are vertically symmetrical through hot pressing and traction of a hot pressing roller, wherein the conductive composite material sheet is cut into a PTC core material with proper size; finally, the step of obtaining the product,
4) The combined PTC core is processed into a surface mount small size 1812 packaged overcurrent protection element by PCB processes including etching, lamination, drilling, copper deposition, tin plating, dicing.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211593487.XA CN116130185A (en) | 2022-12-13 | 2022-12-13 | Overcurrent protection element with high lightning-proof capability |
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| CN202211593487.XA CN116130185A (en) | 2022-12-13 | 2022-12-13 | Overcurrent protection element with high lightning-proof capability |
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