CN103258607A - Overcurrent protection element - Google Patents
Overcurrent protection element Download PDFInfo
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- CN103258607A CN103258607A CN2012100374354A CN201210037435A CN103258607A CN 103258607 A CN103258607 A CN 103258607A CN 2012100374354 A CN2012100374354 A CN 2012100374354A CN 201210037435 A CN201210037435 A CN 201210037435A CN 103258607 A CN103258607 A CN 103258607A
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Abstract
The invention relates to an overcurrent protection element, which comprises two metal foils and a PTC material layer, wherein the PTC material layer is laminated between the two metal foils, has a volume resistivity value of less than 0.4 omega-cm, and comprises (1) a crystallinity high molecule polymer and (2) an electrically conductive ceramic filler, the electrically conductive ceramic filler is dispersed in the crystallinity high molecule polymer and has a hexagonal closely-stacked structure, and the electrically conductive ceramic filler content is 70-95% of the weight of the PTC material layer, and resistance reproducibility of the material can be effectively increased with the electrically conductive ceramic filler.
Description
Technical field
The present invention relates to a kind of thermistor element, more particularly to a kind of over-current protecting element.
Background technology
Due to positive temperature coefficient (Positive Temperature Coefficient；PTC) the resistance versus temperature change of the conducing composite material of characteristic is with the sharp characteristic of reaction, can as current sensing element material, be widely used at present on over-current protecting element or circuit element.Because the resistance of PTC conducing composite materials at a normal temperature can maintain extremely low value, enable circuit or battery normal operation.But, when circuit or battery generation overcurrent (over-current) or the phenomenon of high temperature (over-temperature) excessively, its resistance value can be improved to a high resistance state (at least 10 moment2More than Ω), and by excessive current reduction, to reach the purpose of protection battery or circuit element.
In general, PTC conducing composite materials are constituted by having crystalline polymer and conductive filler, the conductive filler is dispersed among the polymer.The polymer is generally polyolefin polymers, for example：Polyethylene, and traditional conductive filler is generally carbon black, conductivity ceramics and metal dust etc..
Because general conductivity ceramics filler forms conductive path in a stacked fashion, when the crystalline polymer polymer in the composite is because of overcurrent (over-current) or crosses cooling after high temperature (over-temperature) is heated, produce macromolecule recrystallization phenomenon, the mode for causing ceramic packing to stack is changed, so that conductive path is reduced, the resistance of the conducing composite material is caused when bearing overcurrent (over-current) repeatedly or bearing high temperature (over-temperature) triggering (trip) reaction repeatedly, resistance is difficult to return back to initial value, that is, produce the problem of resistance repeatability ratio (trip jump) is too high.
The content of the invention
It is an object of the invention to provide a kind of over-current protecting element, still there is preferably repeatability after triggering (trip) reaction, to extend the life-span that battery is used.
The present invention provides a kind of over-current protecting element, by the conductivity ceramics filler that specific structure is added in crystalline polymer polymer, the over-current protecting element is had excellent low-resistance value and resistance repeatability.
Effectively to reduce resistance value of the over-current protecting element after triggering (trip) repeatedly, and the volumetric resistivity value of the conducing composite material is maintained to be less than 0.4 Ω-cm, the present invention is using the conductivity ceramics filler with given stack structure.The conductivity ceramics filler of the present invention is the tightly packed crystal of six sides (Hexagon close-packed；HCP) structure, this Close stack mode has more conductive path so that electric conductivity preferably, and can effectively promote the resistance repeatability of material.
The over-current protecting element of one embodiment of the invention includes two tinsels and a ptc layer.Ptc layer is stacked between two tinsel, and its volumetric resistivity value is less than 0.4 Ω-cm.Ptc layer includes (i) crystalline polymer polymer；And (ii) intersperses among the conductivity ceramics filler among the crystalline polymer polymer.Conductivity ceramics filler is six side's close-packed structures, and accounts for the percentage by weight of the ptc layer between 70% to 95%.
In one embodiment, conductivity ceramics filler can be powdered, and particle size is main between 0.01 μm to 100 μm, and preferable particle size is between 0.1 μm to 50 μm.Conductivity ceramics filler can be molybdenum carbide, tungsten carbide or its mixture.
In one embodiment, the crystalline polyolefin polymers of ptc layer selection tool (including ethene polymers, polypropylene, or poly- fluorine compounds, such as high density polyethylene (HDPE), medium density polyethylene, low density polyethylene (LDPE), Tissuemat E, polypropylene, polyvinyl chloride or polyvinyl fluoride etc.), co-polymer (the sour co-polymer of such as ethene-acryl of olefin monomer and acryl class monomer, ethene-acryl fat co-polymer) or the co-polymer (such as ethylene vinyl alcohol copolymer compound) of olefin monomer and vinyl alcohol monomer, and can be from one or more polymeric materials.Low density polyethylene (LDPE) can be formed with traditional Ziegler-Natta catalyst or with Metallocene polymerization catalysts, also can be via vinyl monomer and other monomers (for example：Butylene (butene), hexene (hexene), octene (octene), acrylic acid (acrylic acid) or vinylacetate (vinyl acetate)) combined polymerization forms.
The present invention uses the closelypacked conductivity ceramics filler of six sides, after repeatedly being triggered through 300 times, by resistance repeatability ratio (trip jump) R300/Ri controls less than or equal to 25.Wherein Ri is starting resistance, and R300 is the resistance value measured after returning back to room temperature one hour after triggering 300 times.
Because ptc layer has at a fairly low volumetric resistivity value, the area of PTC chips (ptc layer i.e. needed for over-current protecting element of the invention) can be contracted to be less than 50mm2, and remain able to reach the low-resistance purpose of element, more PTC chips may finally be produced from every ptc layer of commensurate's area, making the cost of production reduces.
The over-current protecting element of the present invention; wherein two tinsel by tin cream (solder) through reflow or by spot welding mode can be bonded into an assembly (assembly) with another two metal electrode film, be typically into the element of monaxon (axial-leaded), plug-in type (radial-leaded), terminal type (terminal) or surface adhesion type (surface mount).The over-current protecting element of the present invention; tinsel can be connected in power supply and form a galvanic circle (circuit) (in another embodiment above and below being wherein somebody's turn to do; power supply then can be connected in by two metal electrode film and a galvanic circle is formed); ptc layer is acted under the situation of overcurrent, and reaches the function of protective loop.
Brief description of the drawings
Fig. 1 is the schematic diagram of the over-current protecting element of one embodiment of the invention；And
Fig. 2 is the schematic diagram of the over-current protecting element of another embodiment of the present invention.
Wherein, description of reference numerals is as follows：
10 overcurrent protection elements
11 ptc layers
12 tinsels
20 overcurrent protection elements
22 metal electrode films
Embodiment
For the above and other technology contents of the present invention, feature and advantage can be become apparent, it is cited below particularly go out related embodiment, and coordinate accompanying drawing, be described in detail below：
Illustrate the composition of over-current protecting element of the present invention, including embodiment one to 14, comparative example one to four, and relative production process below.
The composition of ptc layer used in over-current protecting element of the present invention and weight (unit：G) as shown in Table 1.
Table one
Wherein LDPE-1 is low-density crystallinity polyethylene (density：0.924g/cm3, fusing point：113℃)；HDPE-1 is high density crystallinity polyethylene (density：0.943g/cm3, fusing point：125℃)；HDPE-2 is high density crystallinity polyethylene (density：0.961g/cm3, fusing point：131℃).In embodiment one to 14, conductivity ceramics filler includes molybdenum carbide (Mo2C) or tungsten carbide (WC), and the magnetic materials such as iron (Fe), cobalt (Co), nickel (Ni) or vanadium (V) can further be added.In addition, fire retardant magnesium hydroxide (Mg (OH) can be added on demand2).Conductive carbonized ceramic packing external form can be broken shape, multiangular, spherical or sheet.Conductivity ceramics filler in comparative example one to four is to select face-centered cubic (Face-Centered Cubic；FCC) zirconium carbide (ZrC) or titanium carbide (TiC) of structure etc..The effect of the conductivity ceramics filler of the present invention is mainly so that crystalline polymer polymer and conductivity ceramics filler have preferable associativity and stackability, cooled down with reducing after the crystalline polymer in composite is heated, cause the conductivity ceramics filler in material to rearrange because recrystallizing phenomenon, in turn result in the problem of path is reduced.The addition of magnetic material can further strengthen mentioned effects in embodiment, but only be the necessary material composition of another option of the invention and non-invention.Conductivity ceramics filler accounts for the percentage by weight of ptc layer between 70~95%, and it also can be 75%, 80%, 85%, 90% or 92%.The percentage by weight that magnetic material accounts for the ptc layer is less than 15%, especially less than 10% or 8%.
Manufacturing process is as follows：Batch kneading machine (Haake-600) feeding temperature is scheduled on 160 DEG C, feed time is 2 minutes, feeding schedule is the weight as shown in table one, add quantitative crystalline polymer polymer, the several seconds is stirred, conductivity ceramics powder, (its particle size is between 0.1 μm to 50 μm) magnetic material, fire retardant etc. is added.The rotating speed of kneading machine rotation is 40rpm.After 3 minutes, its rotating speed is improved to 70rpm, continues blanking after kneading 7 minutes, and forming one has the conducing composite material of ptc characteristicses.
Above-mentioned conducing composite material is inserted into outer layer as steel plate using symmetric mode up and down, interior thickness is in 0.33mm and 0.2mm mould, mould respectively puts the not imperial release cloth of one layer of iron, first precompressed 3 minutes, precompressed operating pressure 50kg/cm up and down2, temperature is 180 DEG C.Pressed after exhaust, pressing time is 3 minutes, and pressing pressure is controlled in 100kg/cm2, temperature is 180 DEG C, and one step press action is repeated afterwards, and pressing time is 3 minutes, and pressing pressure is controlled in 150kg/cm2, temperature is 180 DEG C, forms a ptc layer 11 afterwards, as shown in Figure 1.In one embodiment, the thickness of the ptc layer 11 (is more than 0.1mm or is preferably greater than 0.2mm) for 0.3mm.
The ptc layer 11 is cut into 20 × 20cm2Square, recycle pressing by the direct brought into physical contact of two tinsel 12 in the upper and lower surface of the ptc layer 11, it is with symmetric mode up and down sequentially to cover tinsel 12 in the surface of ptc layer 11.Then, the not imperial release cloth of dedicated buffering material, iron and steel plate are pressed and a sandwich construction is formed.The sandwich construction is pressed again, and pressing time is 3 minutes, and operating pressure is 70kg/cm2, temperature is 180 DEG C.Afterwards, the wafer-like over-current protecting element 10 to form 2.8mm × 3.5mm is punched with mould.
In one embodiment, two metal electrode films 22 can be vertically connected with two tinsel 12 with tin cream (solder paste) by reflow mode again, the over-current protecting element 20 of shaft-like formula (axial) be made, as shown in Figure 2.Also the element of plug-in type (radial-leaded), terminal type (terminal) or surface adhesion type (surface mount) can be optionally made in practical application.
Following table two shows every test characteristic of over-current protecting element.
The volumetric resistivity value (ρ) of ptc layer 11 can be calculated and obtained according to formula (1)：
Wherein R is the resistance value (Ω) of ptc layer 11, and A is the area (cm of ptc layer 112), L is the thickness (cm) of ptc layer 11.R in formula (1) is substituted into Ri (Ω) value (0.0064 Ω) of the embodiment one of table two, A is with 9.8mm2Substitute into, L is substituted into 0.3mm (=0.03cm), you can try to achieve the Ω-cm of ρ=0.0209.Ω-the cm of the volumetric resistivity value ρ of embodiment two=0.016 and the volumetric resistivity value of other embodiment can equally be calculated.The data of consolidated statement two, volumetric resistivity value ρ is less than 0.4 Ω-cm, especially less than 0.3 Ω-cm, 0.1 Ω-cm, 0.08 Ω-cm or 0.05 Ω-cm.
Resistance repeatability is tested under conditions of 6V voltages and 50mA electric currents is applied, and the resistance repeatability of element start is also shown in table two.Resistance ratio R300/Ri after embodiment one to 14 is triggered in 300 times is respectively less than 25, and in addition to embodiment three, embodiment seven, embodiment 12~14, R300/Ri can further be less than 20；Resistance ratio R100/Ri after being triggered as 100 times is respectively less than 18, and major part embodiment R100/Ri is smaller than 15, even less than 12.The resistance ratio R300/Ri of comparative example one to four is all higher than 27 in table two, it is clear that the present invention is from the conductivity ceramics filler of HCP structures, and the conductive path of this stack manner, which is configured, causes electric conductivity preferably, can effectively promote the resistance repeatability of material.
Table two
Titanium carbide or zirconium carbide in comparative example are stacked as FCC configuration, and the resistance repeatability ratio of its corresponding PTC-element is obviously not as molybdenum carbide and the resistance of the HCP structures of tungsten carbide reproduce sex expression.The conductive characteristic of molybdenum carbide is about 97m Ω-cm, and density is 9.16g/cm3, Vickers hardness is 1800HV50；The conductive characteristic of tungsten carbide about 97m Ω-cm, density is 15.63g/cm3, Vickers hardness is 2200HV50.The electrical conductivity of molybdenum carbide is higher, and density is relatively low, and hardness is relatively low, therefore has the advantage of highly conductive, lightweight and easy processing compared to tungsten carbide.Molybdenum carbide and tungsten carbide are used as conductivity ceramics filler simultaneously in embodiment nine and ten, although its volumetric resistivity value is in all embodiments and not least, but resistance repeatability ratio R 300/Ri≤15 and R100/Ri≤10 show quite excellent resistance repeatability.In practical application, the weight ratio of molybdenum carbide/tungsten carbide can be between 0.5~1.5, or between 0.8~1.2.
The over-current protecting element of the present invention; by the conductivity ceramics filler and at least crystalline high molecular polymer for adding a tool specific size distribution; understood via the result of table two; the over-current protecting element of the present invention really can reach the expected purpose with excellent initial resistivity value (in addition to embodiment 12 and 13, Ri is respectively less than 10m Ω) and resistance repeatability.
The technology contents and technical characterstic of the present invention have revealed that as above, but those of ordinary skill in the art are still potentially based on teachings of the present invention and announcement and make a variety of replacements and modification without departing substantially from spirit of the present invention.Therefore, protection scope of the present invention should be not limited to the content disclosed in embodiment, and should include various replacements and modification without departing substantially from the present invention, and be covered by following right.
Claims (20)
1. a kind of over-current protecting element, it is characterised in that including：
Two tinsels；And
One ptc layer, is stacked between two tinsel, and volumetric resistivity value is less than 0.4 Ω-cm, and the ptc layer is included：Crystalline polymer polymer and conductivity ceramics filler among the crystalline polymer polymer is interspersed among, wherein the conductivity ceramics filler is six side's close-packed structures, and its percentage by weight in the ptc layer is between 70% to 95%.
After 2. over-current protecting element according to claim 1, the wherein over-current protecting element are triggered repeatedly through 300 times, its resistance repeatability ratio is less than or equal to 25.
3. over-current protecting element according to claim 2, wherein the resistance repeatability ratio are tested under conditions of 6V voltages and 50mA electric currents is applied.
4. over-current protecting element according to claim 1, wherein the conductivity ceramics filler include molybdenum carbide, tungsten carbide or its mixture.
5. over-current protecting element according to claim 1, the wherein ptc layer also include magnetic material.
6. over-current protecting element according to claim 5, the wherein magnetic material are selected from iron, cobalt, nickel, vanadium or its mixture.
7. over-current protecting element according to claim 5, the wherein magnetic material are less than 15% in the percentage by weight of the ptc layer.
After 8. over-current protecting element according to claim 1, the wherein over-current protecting element are triggered repeatedly through 100 times, its resistance repeatability ratio is less than or equal to 18.
9. over-current protecting element according to claim 1, wherein the conductivity ceramics filler are the mixture of molybdenum carbide and tungsten carbide, and after 300 times repeatedly triggering, its resistance repeatability ratio is less than or equal to 15.
10. over-current protecting element according to claim 9, wherein after being triggered repeatedly through 100 times, its resistance repeatability ratio is less than or equal to 10.
11. over-current protecting element according to claim 9, wherein molybdenum carbide compared to tungsten carbide weight ratio between 0.5 to 1.5.
12. the thickness of over-current protecting element according to claim 1, the wherein ptc layer is more than 0.1mm.
13. the starting resistance of over-current protecting element according to claim 1, the wherein ptc layer is less than 10m Ω.
14. over-current protecting element according to claim 1, wherein the crystalline polymer polymer are polyolefin polymers.
15. over-current protecting element according to claim 14, the wherein polyolefin polymers include ethene polymers, polypropylene or poly- fluorine compounds.
16. over-current protecting element according to claim 14, the wherein polyolefin polymers include high density polyethylene (HDPE), medium density polyethylene, low density polyethylene (LDPE), Tissuemat E, polypropylene, polyvinyl chloride or polyvinyl fluoride.
17. over-current protecting element according to claim 1, the wherein particle size of the conductive carbonized ceramic packing are between 0.1 μm to 50 μm.
18. the area of over-current protecting element according to claim 1, the wherein ptc layer is less than 50mm2。
19. magnesium hydroxide is also included in over-current protecting element according to claim 1, the wherein ptc layer.
20. the volumetric resistivity value of over-current protecting element according to claim 1, the wherein ptc layer is less than 0.1 Ω-cm.
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Cited By (3)
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| CN105321640A (en) * | 2014-07-30 | 2016-02-10 | 聚鼎科技股份有限公司 | positive temperature coefficient element |
| TWI557756B (en) * | 2014-09-29 | 2016-11-11 | 聚鼎科技股份有限公司 | Positive temperature coefficient composition and over-current protection device containing the same |
| CN116162302A (en) * | 2022-12-30 | 2023-05-26 | 上海维安电子股份有限公司 | Polymer-based conductive composite and overcurrent protection element |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105321640A (en) * | 2014-07-30 | 2016-02-10 | 聚鼎科技股份有限公司 | positive temperature coefficient element |
| CN105321640B (en) * | 2014-07-30 | 2018-05-18 | 聚鼎科技股份有限公司 | Positive temperature coefficient element |
| TWI557756B (en) * | 2014-09-29 | 2016-11-11 | 聚鼎科技股份有限公司 | Positive temperature coefficient composition and over-current protection device containing the same |
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| CN106158174B (en) * | 2014-09-29 | 2018-07-27 | 聚鼎科技股份有限公司 | Positive temperature coefficient material and overcurrent protection element containing same |
| CN116162302A (en) * | 2022-12-30 | 2023-05-26 | 上海维安电子股份有限公司 | Polymer-based conductive composite and overcurrent protection element |
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