CN101026029B - Overcurrent protection element - Google Patents
Overcurrent protection element Download PDFInfo
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- CN101026029B CN101026029B CN200610008303A CN200610008303A CN101026029B CN 101026029 B CN101026029 B CN 101026029B CN 200610008303 A CN200610008303 A CN 200610008303A CN 200610008303 A CN200610008303 A CN 200610008303A CN 101026029 B CN101026029 B CN 101026029B
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Abstract
This invention relates to an overcurrent protection element including two foils and a pile of PTC material layers set between the two foils and the material layer contains a macromolecular polymer backing and a conductive filling, and the backing includes at least a first crystallized macromolecular polymer(such as LDPE) and a second crystallized macromolecular polymer (such as PVDE), in which, the melting point of the second is higher than the first one for 50deg.C at least, said conductive filling is made of metal particles or oxygen-free ceramic powder with the selected volume resistivity smaller than 500mOhm.cm scattered in the backing, and the volume resistivity of the PTC material layer is smaller than 0.1Ohm.cm, when the resistance is increased to 1000 times that of the initial value R1, the temperature detracting the melting point of the first polymer is 15deg,C.
Description
Technical field
The present invention relates to a kind of over-current protecting element, more specifically, relate to an over-current protecting element that is applied to low load (low load) environment.
Background technology
Owing to have positive temperature coefficient (Positive Temperature Coefficient; PTC) resistance of the conducing composite material of characteristic has the sharp characteristic of variations in temperature reaction, can be used as the material of current sensing element, and has been widely used on over-current protecting element or the circuit element at present.Because the resistance of PTC conducing composite material under normal temperature can be kept utmost point low value, makes circuit or battery be able to normal operation.But when circuit or battery generation overcurrent (over-current) or when crossing the phenomenon of high temperature (over-temperature), its resistance value can be brought up to a high resistance state (at least 10 moment
4More than the ohm), and with excessive current reversal payment, to reach the purpose of protection battery or circuit element.
Generally speaking, the PTC conducing composite material is made up of the polymer and the conductive filler of one or more crystallinity of signing an undertaking, and described conductive filler is dispersed in the described polymer.Described polymer is generally polyolefin polymers, for example: polyethylene; And conductive filler the most widely uses with carbon black.
Overcurrent protection with battery; because of protection must be provided when lower temperature; so its PTC conducing composite material selects for use the lower polymer of fusing point (for example low density polyethylene (LDPE) (LDPE)) as base material; make it when lower temperature, reach the triggering temperature, avoid battery and explode or burn because of overheated.
Yet, the PTC conducing composite material that LDPE constitutes polymeric substrate through long-term the use after, it has the resistance high phenomenon of wafing gradually.The thermal shock (thermal shock) that for example is placed on temperature range-40 ℃～+ 85 ℃ is after 100 circulations (cycle), its resistance will be increased by initial 10m Ω suddenly to more than 1 Ω, be that resistance can't be replied initial value, and the incompatible electric device that is used for low load such as battery.
Though be known in and add high density polyethylene (HDPE) (HDPE) among the LDPE and can improve the bad problem of above-mentioned resistance reproducibility; yet the phenomenon of dissolving each other is arranged because of the fusing point close (being about 105 ℃ and 130 ℃ respectively) of LDPE and HDPE; make that triggering temperature compares obviously higher (as shown in Figure 1) with the PTC conducing composite material that with LDPE is polymeric substrate merely; promptly improve the triggering temperature of PTC conducing composite material, thereby forfeiture low-temperature protection characteristic.Therefore, probably have and burn or danger such as blast if be applied to lithium ion battery.
In summary, form the situation of facing a difficult choice between temperature in improving the resistance reproducibility and reducing to trigger, and need to break through required in a hurry for low load applications.
Summary of the invention
Main purpose of the present invention provides a kind of over-current protecting element; by owing to add the higher crystalline polymer polymer of a fusing point in the PTC conducing composite material; make described over-current protecting element have excellent resistance and reply reproducibility, and still remain with the defencive function that low temperature triggers (trip).
In order to achieve the above object, the present invention discloses a kind of over-current protecting element, it comprises two tinsels and and is stacked at ptc layer between described two tinsels. and described ptc layer mainly comprises a high molecular polymer base material and a conductive filler. and described high molecular polymer base material comprises one first crystalline polymer polymer and one second crystalline polymer polymer at least, the fusing point of the wherein said second crystalline polymer polymer deducts the fusing point of the described first crystalline polymer polymer greater than 50 ℃, be that both fusing points differ by more than 50 ℃. in one embodiment of this invention, the described first crystalline polymer polymer is LDPE (about 105 ℃ an of fusing point), and the second crystalline polymer polymer can be fluoropolymer, as poly-inferior ethene (the polyvinylidine fluoride that fluoridizes; PVDF) (about 165 ℃ of fusing point).Described conductive filler is for selecting metallic particles (for example nickel powder) or the anaerobic ceramic powders (for example titanium carbide (TiC) or tungsten carbide (TiW)) of volume resistance value less than 500m Ω-cm, and it intersperses among in the described high molecular polymer base material.The initial volume resistance value of described ptc layer is less than 0.1 Ω-cm, and when the resistance of ptc layer was increased to 1000 times of initial resistance Ri, its temperature deducted the fusing point of the described first crystalline polymer polymer less than 15 ℃.
In addition, described ptc layer is that its resistance is less than 100 times of initial resistance after-40 to+85 ℃ the thermal shock circulation 100 times through temperature.The described first crystalline polymer polymer accounts for the percentage by weight of ptc layer less than 20%.The described again second crystalline polymer polymer accounts for the percentage by weight of ptc layer between 1-10%.
The selected LDPE of ptc layer in the embodiment of the invention can form with traditional Z iegler-Natta catalyst or with the Metallocene polymerization catalyst, also can form via vinyl monomer and other monomer (for example: butylene (butene), hexene (hexene), octene (octene), acrylic acid (acrylic acid) or vinylacetate (vinyl acetate)) combined polymerization.
In addition, can add non-conducting filler in the ptc layer, the inorganic compound that flame retardant effect or arc resistant effect are for example arranged, for example: zinc oxide, antimony oxide, aluminium oxide, silica, calcium carbonate, magnesium sulfate, barium sulfate and the compound (for example: magnesium hydroxide, aluminium hydroxide, calcium hydroxide, barium hydroxide etc.) that contains hydroxy (OH).Its particle size of this non-conducting filler mainly between 0.05 μ m between the 50 μ m, and its weight ratio is between 1% to 20%.
For example with the application of lithium ion battery, the safety when protecting it to overcharge, the over-current protecting element of its use must just can have the reaction of triggering at lower temperature, and must possess good resistance answer or reproducibility.Over-current protecting element of the present invention can overcome the difficult shortcoming that reaches simultaneously of above-mentioned two essential condition, and application of hanging down load and the function that has low-temperature protection simultaneously concurrently can be provided.
Description of drawings
Fig. 1 adds and does not add temperature and the resistance graph of a relation of HDPE for conventional PTC composite material;
The demonstrate over-current protecting element of one embodiment of the invention of Fig. 2; And
Fig. 3 adds and does not add temperature and the resistance graph of a relation of PVDF for the PTC composite material.
Embodiment
Below putting up with the PVDF that adds different proportion is example, by reproducing and hang down characteristics such as triggering temperature with the resistance that over-current protecting element of the present invention is described.
Table one shows the constituent of ptc layer, wherein low density polyethylene (LDPE) (LDPE) is to be selected from platform to mould the model Taisox 6330F product that company produces, high density polyethylene (HDPE) (HDPE) is to be selected from platform to mould model Taisox 8010 products that company produces, PVDF then is selected from the model Kynar740 product that ElfAutochem company produces, and titanium carbide (TiC) then is selected from the model 22R-0601 product of InframatAdvanced Materials company.Experimental group 1,2 and 3 is added the PVDF of Different Weight percentage, and it is respectively 2.27%, 4.17% and 3.35%; Comparative group 1 and 2 do not add PVDF.
Table one
The fusing point of LDPE is about 105 ℃, and the fusing point of HDPE then is about 130 ℃, and the fusing point of PVDF is about 165 ℃.Titanium carbide is as conductive filler, its volume resistance value is about 150 Ω-cm, it also can be substituted by other metal or anaerobic pottery conductive filler with the volume resistance value of at least 500 Ω-below the cm so that composite ptc material can reach the volume resistance value that is lower than 0.1 Ω-cm.So with (generally greater than 0.1 Ω-cm) compare, metal or anaerobic pottery conductive filler can effectively reduce resistance value to the volume resistance value, and are suitable for the application of low load electronic product as the ptc material of conductive filler with carbon black.
In each above-mentioned experimental group and the ratio shown in the comparative group places steel bowl earlier and stir with measuring spoon after, add model and be in batch formula muller of Hakke-600 and mix.The feeding temperature that mixes is set at 210 ℃, and the rotating speed of initial stage mixing roll is made as 40rpm, blanking after then being increased to 70rpm after 3 minutes and continuing mixing 12 minutes, and form a conducing composite material with ptc characteristics.
It is that steel plate, interior thickness are in the mould of 0.4mm that above-mentioned conducing composite material is inserted skin with upper and lower symmetric mode, the upper and lower not imperial release cloth of one deck iron of respectively putting of described mould.With the first preheating of described conducing composite material 8 minutes, 2 minutes (operating pressure 100kg/cm of pressing again
2, temperature is 200 ℃), and form a ptc layer.Described ptc layer is cut into 20 * 20cm
2Square, and put a tinsel pressing be once again in ptc layer is upper and lower.Afterwards, first preheating 5 minutes, 2 minutes (operating pressure 50kg/cm of pressing again
2, temperature is 200 ℃) and form a tinsel (for example nickel plating Copper Foil) respectively in the upper and lower surface of described ptc layer.Then; PTC chip with the die-cut formation 3.4 * 4.1mm of mould; again with reflow assembling processing procedure; with the upper and lower metal forming of PTC chip respectively via tin cream upper and lower each electrode slice (for example nickel sheet, copper sheet or the sheet metal formed by its alloy) that combines; formation one axle type (axial leaded) PTC element as shown in Figure 2, over-current protecting element 10 promptly of the present invention.Particularly, described over-current protecting element 10 comprises a ptc layer 14, two tinsels 12 and two electrode slices 16.Described ptc layer 14 is stacked between two tinsels 12, and two electrode slices 16 then connect the surface of two tinsels 12 respectively.
Temperature (be defined as and trigger temperature) when initial resistance, volume resistance, the resistance of measuring described ptc layer 14 bounces up 1000 times of initial resistance Ri and in the resistance value of temperature behind 40 ℃～100 ℃ thermal shocks 100 times, its result as shown in Table 2.Wherein the associated electrical resistance is measured with little ohmer four-wire type method, and volume resistance value (ρ) can get according to formula (1) calculating:
Wherein R is the resistance value (Ω) of ptc layer 14, and A is the area (cm of ptc layer 14
2), L is the thickness (cm) of ptc layer 14.
Table two
The PTC composition of consolidated statement one and the experimental data of table two can get following result:
1. the temperature when resistance being bounced up 1000 times of initial resistivity value Ri is defined as the triggering temperature of PTC element.Add some PVDF experimental group 1,2 and 3 its trigger temperature and be respectively 108 ℃, 105 ℃ and 108 ℃, fusing point (the about 105 ℃) homogeneous phase of itself and LDPE is worse than in 5 ℃.In addition, by by adding different PVDF ratios, can will trigger Numerical Control that temperature deduct the LDPE fusing point for less than 15 ℃, and have the value in the practical application.See conversely, do not add the comparative group 1 of PVDF, it triggers temperature about 121 degree that rise sharply, and its function as the low temperature overcurrent protection that significantly detracts.Though comparative group 2 is not added PVDF yet, the ratio that HDPE compares with LDPE is very low, so it triggers obviously rising of temperature.Yet it is behind-40 ℃ to+85 ℃ thermal shocks, and its resistance needing to be unsuitable for the low load of high electric current to use by originally 0.0088 Ω 1.201 Ω that rise sharply.
2. above-mentioned experimental group and comparative group because the low resistance of all adding (titanium carbide of about 150 Ω-cm) is as conductive filler, thus the volume resistance value of corresponding ptc layer all less than 0.1 Ω-cm, its with compare and can significantly reduce as conductive filler with carbon black.
3. comparative group 2 is because add the cause of HDPE, although through-40 ℃ to+85 ℃ thermal shocks after, but its resistance only be increased to 0.213 Ω and still be in the scope of application by 0.0056 Ω, yet its triggering temperature has risen to 121 ℃ and can't be used for low-temperature protection.See the experimental group 1,2 and 3 of adding PVDF conversely, not only the resistance value behind its thermal shock is less than 100 times of its initial resistivity value (experimental group 1,2 and 3 actual multiple are all less than 30 times), and it triggers temperature and the fusing point of LDPE and differs all in 15 ℃ with interior (experimental group 1,2 and 3 actual temperature are worse than in 5 ℃ mutually).
In sum, the present invention utilizes and adds PVDF and can significantly lower the resistance value behind thermal shock and increase useful life, and it produces the problem that triggers increase in temperature also can not add HDPE as routine the time, and the protection still can provide low temperature the time.But the crystalline polymer polymer that the present invention adds does not limit and uses PVDF, and other has the high molecular polymer of similar characteristics, is also contained by the present invention.
Technology contents of the present invention and technical characterstic disclose as above, yet the those skilled in the art still may be based on teaching of the present invention and announcement and made all substitutions and modifications that do not deviate from spirit of the present invention.Therefore, protection scope of the present invention should be not limited to the content that embodiment discloses, and should comprise the various substitutions and modifications of the present invention that do not deviate from, and is contained by appending claims.
Claims (10)
1. over-current protecting element comprises:
Two tinsels; And
One PTC material layer is stacked between described two tinsels, and it comprises:
(1) one high molecular polymer base material, it comprises one first crystalline polymer polymer and one second crystalline polymer polymer at least, and the fusing point of the described second crystalline polymer polymer is higher than at least 50 ℃ of the fusing points of the described first crystalline polymer polymer; With
(2) one conductive fillers intersperse among in the described high molecular polymer base material, and its volume resistance value is less than 500 μ Ω-cm;
The volume resistance value of wherein said ptc layer is less than 0.1 Ω-cm, and the temperature when its resistance increases to 1000 times of initial resistance deducts the fusing point of the described first crystalline polymer polymer less than 15 ℃.
2. over-current protecting element according to claim 1 is that the resistance of its ptc layer is less than 100 times of its initial resistance after-40 to 85 ℃ the thermal shock circulation 100 times through temperature.
3. over-current protecting element according to claim 1, the wherein said first crystalline polymer polymer accounts for the percentage by weight of described ptc layer less than 20%.
4. over-current protecting element according to claim 1, the wherein said second crystalline polymer polymer is a fluoropolymer.
5. over-current protecting element according to claim 4, wherein said fluoropolymer is fluoridized inferior ethene for gathering.
6. over-current protecting element according to claim 1, the wherein said first crystalline polymer polymer is a low density polyethylene (LDPE).
7. over-current protecting element according to claim 1, the wherein said second crystalline polymer polymer accounts for the percentage by weight of described ptc layer between 1-10%.
8. over-current protecting element according to claim 1, wherein said conductive filler are metallic particles or anaerobic ceramic powders.
9. over-current protecting element according to claim 1, wherein said conductive filler are nickel powder or titanium carbide.
10. over-current protecting element according to claim 1, it comprises two electrodes that are connected to described two tinsel surfaces in addition.
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| CN200610008303A CN101026029B (en) | 2006-02-17 | 2006-02-17 | Overcurrent protection element |
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| CN200610008303A CN101026029B (en) | 2006-02-17 | 2006-02-17 | Overcurrent protection element |
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| CN102617955B (en) * | 2011-01-26 | 2015-11-25 | 聚鼎科技股份有限公司 | Overcurrent protection and preparation method thereof |
| CN102832604B (en) * | 2011-06-16 | 2015-01-21 | 聚鼎科技股份有限公司 | Over-current protection element |
| CN106328326A (en) * | 2015-06-30 | 2017-01-11 | 瑞侃电子(上海)有限公司 | Positive-temperature-coefficient circuit protection device capable of being subjected to reflow soldering |
| CN106898446A (en) * | 2017-04-18 | 2017-06-27 | 上海长园维安电子线路保护有限公司 | Over-current protecting element |
| US10822513B1 (en) * | 2019-04-26 | 2020-11-03 | 1-Material Inc | Electrically conductive PTC screen printable ink composition with low inrush current and high NTC onset temperature |
| TWI705464B (en) * | 2019-12-20 | 2020-09-21 | 聚鼎科技股份有限公司 | Over-current protection device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1283304A (en) * | 1997-12-15 | 2001-02-07 | 泰科电子有限公司 | Electrical device |
| JP2004193193A (en) * | 2002-12-09 | 2004-07-08 | Nec Tokin Corp | High polymer ptc element |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1283304A (en) * | 1997-12-15 | 2001-02-07 | 泰科电子有限公司 | Electrical device |
| JP2004193193A (en) * | 2002-12-09 | 2004-07-08 | Nec Tokin Corp | High polymer ptc element |
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