TWI434300B - Over-current protection device - Google Patents

Description

Overcurrent protection component

The present invention relates to an overcurrent protection component, and more particularly to an overcurrent protection component having a low resistance value and excellent resistance reproducibility.

Since the resistance of the conductive composite material having positive temperature coefficient (PTC) characteristics is sensitive to temperature changes, it can be used as a material of current sensing elements, and has been widely used as an overcurrent protection element or circuit element. on. Since the resistance of the PTC conductive composite at normal temperatures can be maintained at a very low value, the circuit or battery can operate normally. However, when an over-current or over-temperature phenomenon occurs in a circuit or battery, the resistance value is instantaneously increased to a high resistance state (at least 10 ² Ω or more), and excess current is generated. Reduced for the purpose of protecting the battery or circuit components.

In general, a PTC conductive composite is composed of one or more crystalline polymers and conductive fillers, which are uniformly dispersed in the polymer. The polymer is typically a polyolefin based polymer such as polyethylene and the electrically conductive filler is typically carbon black. However, carbon black can provide a lower conductivity, which does not meet the need for low resistance.

The present invention provides an overcurrent protection element having an excellent low resistance value by adding a conductive carbonized ceramic filler having a specific particle size distribution and a conductive carbon black filler in the crystalline high molecular polymer. And resistance reproducibility.

An overcurrent protection component according to an embodiment of the invention comprises a two metal foil and a layer of PTC material. The PTC material layer is stacked between the two metal foils and has a volume resistance value of 0.07 to 0.32 Ω-cm. The PTC material layer comprises (i) a crystalline high molecular polymer; (ii) a conductive carbonized ceramic filler having a volume resistivity of less than 0.1 Ω-cm; and (iii) a conductive carbon black filler having a ratio of 1 to a conductive carbonized ceramic filler : between 90 and 1:4. The conductive carbonized ceramic filler and the conductive carbon black filler are dispersed in the crystalline high molecular polymer. The resistance reproducibility R100/Ri ratio of the PTC material layer is between 3 and 20.

In one embodiment, the metal foil contains a nodule protruding rough surface and is in direct physical contact with the PTC material layer. The conductive carbonized ceramic filler may be in the form of a powder, and the particle size is mainly between 0.01 μm and 100 μm, and preferably the particle size is between 0.1 μm and 50 μm. The conductive carbonized ceramic filler has a volume resistance value of less than 0.1 Ω-cm and is uniformly dispersed in the crystalline high molecular polymer. The crystalline high molecular polymer may be selected from the group consisting of high density polyethylene, low density polyethylene, polypropylene, polyvinyl chloride or polyvinyl fluoride.

In one embodiment, the conductive carbon black filler used in the present invention has a particle size mainly between 15 nm and 75 nm, and the weight ratio thereof added to the PTC material is between 1% and 20%.

Since the volume resistivity of the conductive carbonized ceramic filler is low (less than 0.1 Ω-cm), the PTC material mixed by the present invention can achieve a volume resistance value of less than 0.32 Ω-cm.

The overcurrent protection component of the present invention, wherein the two metal foils can be joined to the other metal electrode sheets by soldering or by spot welding into an assembly, usually an axis. An elemental-leaded, radial-leaded, terminal, or surface mount component. In the overcurrent protection component of the present invention, the upper and lower metal foils can be connected to a power source to form a conductive circuit, and the PTC material layer operates under an overcurrent condition to achieve the function of the protection circuit.

The conductivity of the conductive composite is determined by the type and content of the conductive filler. In recent years, consumer electronics have increased their proportion over a prolonged service life for reusable batteries (such as lithium batteries) or single-use batteries (such as carbon-zinc batteries). Since carbon black can provide a lower electrical conductivity than metal or ceramic fillers, the present invention incorporates a conductive carbonized ceramic filler to increase electrical conductivity. However, since the conductive carbonized ceramic filler forms a conductive path in a stacked manner, when the crystalline polymer in the composite material is heated and recrystallized, the conductive path of the ceramic filler in the material is reduced, causing the conductive composite material to repeatedly occur. When an over-current or over-temperature event occurs, the resistance of the trip is too high, thus shortening the life of the battery.

Since the surface of the carbon black is uneven, and the adhesion to the polyolefin-based polymer is better, it has better electrical resistance. In order to effectively reduce the resistance value of the overcurrent protection component after repeated tripping, and maintain the low volume resistance of the conductive composite material, the present invention simultaneously adds conductive carbonized ceramic powder and carbon black to the crystalline high molecular polymer material. The powder, by virtue of the preferred electrical resistance of the carbon black filler, and the high electrical conductivity of the electrically conductive carbonized ceramic powder, allows the overcurrent protection component to simultaneously perform both functions.

The components of the overcurrent protection device of the present invention are described below, including Embodiments 1 to 8, Comparative Example 1 to Comparative Example 4, and related fabrication processes.

The composition and weight (unit: gram) of the PTC material layer used in the overcurrent protection element of the present invention are shown in Table 1. Among them, LDPE-1 is a low-density crystalline polyethylene (density: 0.924 g/cm ³ , melting point: 113 ° C); HDPE-1 is a high-density crystalline polyethylene (density: 0.943 g/cm ³ , melting point: 125 ° C) HDPE-2 is a high-density crystalline polyethylene (density: 0.961 g/cm ³ , melting point: 131 ° C); non-conductive filler is made of boron nitride (BN), aluminum nitride (AlN), alumina (Al ₂ O ₃ ) or magnesium hydroxide (Mg(OH) ₂ ). Carbon black (Carbon black) and titanium carbide (TiC) are used for the conductive filler. In the embodiment of the invention, the weight ratio of the conductive carbon black filler to the conductive carbonized ceramic filler (TiC) is between 1:90 and 1:4. The crystalline polymer has a weight percentage of the PTC material layer of about 10% to 20%. The weight percentage of the conductive carbon black filler to the PTC material layer is between 1% and 20%, or preferably between 6% and 18%. The conductive carbonized ceramic filler accounts for between 65% and 90% by weight of the PTC material layer, or preferably between 66% and 83%.

The production process is as follows: the batch temperature of the batch mixer (Haake-600) is set at 160 ° C, the feeding time is 2 minutes, and the feeding procedure is the weight shown in Table 1, and the quantitative crystalline polymer polymerization is added. Stir for a few seconds, then add conductive carbonized ceramic filler titanium carbide powder (with a particle size between 0.1μm and 50μm) and/or carbon black powder (with a particle size between 15nm and 75nm) And a non-conductive filler of boron nitride, aluminum nitride, aluminum oxide or magnesium hydroxide (having a particle size ranging from 0.1 μm to 30 μm). The speed of the chain mixer rotation was 40 rpm. After 3 minutes, the rotation speed was increased to 70 rpm, and the mixture was further mixed for 7 minutes to be discharged, thereby forming a conductive composite material having PTC characteristics.

The above conductive composite material is placed in a lower symmetrical manner into a steel sheet having a thickness of 0.33 mm and a thickness of 0.2 mm in the middle, and a layer of Teflon stripping cloth is placed on the upper and lower sides of the mold, and the pre-pressing pressure is 50 kg. /cm ² , the temperature is 180 °C. After the exhausting, the pressing is performed for 3 minutes, the pressing pressure is controlled at 100 kg/cm ² , the temperature is 180 ° C, and then the pressing action is repeated once, the pressing time is 3 minutes, and the pressing pressure is controlled. 150 kg/cm ² and a temperature of 180 ° C, after which a PTC material layer 11 was formed as shown in FIG. In one embodiment, the PTC material layer 11 has a thickness greater than 0.1 mm, preferably greater than 0.2 mm or 0.3 mm.

The PTC material layer 11 is cut into a square of 20×20 cm ² , and the two metal foils 12 are directly physically contacted with the upper surface of the PTC material layer 11 by pressing, which is attached to the surface of the PTC material layer 11 . The metal foil 12 is sequentially covered in a lower symmetrical manner. The gold

The foil 12 has a nodule protruding rough surface and is in direct physical contact with the PTC material layer 11. Next, a special cushioning material, a Keflon release cloth, and a steel plate are pressed to form a multilayer structure 10. The multilayer structure was further pressed, the pressing time was 3 minutes, the operating pressure was 70 kg/cm ² , and the temperature was 180 °C. Thereafter, an annular wafer-shaped overcurrent protection element 10' having an outer diameter of 16 mm and an inner diameter of 10 mm is die-cut by a die, and the two metal electrode sheets 22 are vertically connected to the two by solder paste by reflow soldering. On the metal foil 12, a shaft-shaped overcurrent protection element 20 is formed as shown in FIG. Table 2 below shows the test characteristics of the overcurrent protection components.

The volume resistance value (ρ) of the PTC material layer 11 can be calculated according to the formula (1):

Where R is the resistance value (Ω) of the PTC material layer 11, A is the area (cm ² ) of the PTC material layer 11, and L is the thickness (cm) of the PTC material layer 11. R in the formula (1) is substituted with the Ri (Ω) value (0.0035 Ω) of the first embodiment of the second embodiment, and A is 122.46 mm ² ((=8×8×3.14)-(5×5×3.14) 10 ^-2 cm ² ) Substituting, L is substituted by 0.3 mm, and ρ = 0.1428 Ω-cm can be obtained. In the same manner, ρ=0.2408 Ω-cm of the second embodiment, ρ=0.2571 Ω-cm of the third embodiment, ρ=0.1714 Ω-cm of the fourth embodiment, and ρ=0.3183 Ω-cm of the fifth embodiment are obtained. ρ = 0.1387 Ω-cm in the sixth embodiment, ρ = 0.1714 Ω-cm in the seventh embodiment, and ρ = 0.2 Ω-cm in the eighth embodiment. The volume resistance values were all smaller than ρ=0.3469 Ω-cm of Comparative Example 2 in which only carbon black was added. As can be seen from Table 2, the volume resistance value of the embodiment of the present invention is between 0.07 and 0.32 Ω-cm, preferably between 0.1 and 0.3 Ω-cm or more preferably between 0.12 and 0.28 Ω-cm. between.

The resistance values R10, R100, and R300 of the current protection element 20 in the state of being triggered 10 times, 100 times, and 300 times are also shown in Table 2. The following description will be made using the resistance reproducibility of triggering 100 times. The resistance reproducibility is based on the R100/Ri ratio as the comparison reference, where R100 is the resistance value that triggers 100 times, and Ri is the initial resistance value. The values of the first to eighth embodiments show that the resistance reproducibility R100/Ri of the present invention is between 3 and 20, preferably between 4 and 16, and optimally between 5 and 13. However, in Comparative Example 1, the resistance reproducibility R100/Ri ratio of the element using the titanium carbide filler alone was up to 67.1 after being triggered 100 times, and the addition of aluminum nitride or boron nitride was not added to the comparative examples 3 and 4 except for the titanium carbide. For carbon black, the R100/Ri ratio is greater than 40. It is apparent that the present invention can effectively improve the poor reproducibility of the resistance of the ceramic filler alone. In Comparative Example 2, carbon black was used as the conductive filler alone, and its initial resistance was 8.5 mΩ. The initial resistance value Ri of the embodiment of the present invention was less than 8 mΩ, or preferably less than 7 mΩ. It is obvious that the addition of the ceramic filler to the present invention can effectively reduce the initial resistance. Therefore, Examples 1 to 8 (using a carbonized ceramic filler plus carbon black) have better electrical resistance reproducibility than Comparative Examples 1, 3, and 4 (without carbon black). And Examples 1 to 8 (using a carbonized ceramic filler plus carbon black) have lower initial resistance values and volume resistance values than Comparative Example 2 (carbon black only).

In addition to the materials listed above, the PTC material layer may be provided with a crystalline polyolefin polymer (eg, high density polyethylene, medium density polyethylene, low density polyethylene, polyethylene wax, ethylene polymer, polypropylene, Polyvinyl chloride or polyvinyl fluoride, etc., a copolymer of an olefin monomer and an acrylic monomer (for example, an ethylene-acrylic acid copolymer, an ethylene-acrylic acid copolymer) or an olefin A copolymer of a monomer and a vinyl alcohol monomer (for example, an ethylene-vinyl alcohol copolymer), and the like, and one or more polymer materials may be selected. The low density polyethylene can be polymerized by a conventional Ziegler-Natta catalyst or with a Metallocene catalyst, or via an ethylene monomer with other monomers (eg, butene, hexene, octene, Acrylic acid or vinyl acetate is copolymerized.

The above conductive carbonized ceramic filler may also include tungsten carbide, vanadium carbide, boron carbide, tantalum carbide, tantalum carbide, tantalum carbide, zirconium carbide, chromium carbide or molybdenum carbide. The shape of the conductive carbonized ceramic filler comprises a crushed shape, a polygonal shape, a spherical shape or a sheet shape, and the particle size is between 0.1 μm and 50 μm.

Further, when the PTC material reaches a volume resistance value lower than 1 Ω-cm, it is often impossible to withstand a voltage higher than 12 V because of a low resistance value. Therefore, in order to improve the withstand voltage, in the fifth to eighth embodiments, a non-conductive filler mainly composed of an inorganic compound is added to the PTC material, and the thickness of the PTC material layer is controlled to be greater than 0.1 mm, so that the low resistance PTC material can withstand A voltage of 28V or less, or preferably a voltage of 6V to 28V, or an optimum voltage of 12V to 28V, and a current of 50 amps or less.

In the present invention, the overcurrent protection element has excellent volume resistance value and resistance reproducibility by adding a conductive carbonized ceramic filler having a specific particle size distribution and a conductive carbon black filler in the crystalline high molecular polymer, and the embodiment A non-conductive filler may be added to have a withstand voltage characteristic.

The technical and technical features of the present invention have been disclosed as above, and those skilled in the art can still make various substitutions and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be construed as being limited by the scope of the appended claims

10, 10’. . . Current protection component

11. . . PTC material layer

12. . . Metal foil

20. . . Current protection component

twenty two. . . Metal electrode

1 is a schematic diagram of an overcurrent protection component according to an embodiment of the present invention;

2 is a schematic diagram of an overcurrent protection component according to another embodiment of the present invention.

10. . . Current protection component

11. . . PTC material layer

12. . . Metal foil

Claims (17)

An overcurrent protection component comprising: a two metal foil; and a layer of PTC material stacked between the two metal foils and having a volume resistance value of 0.07 to 0.32 Ω-cm, comprising: (i At least one crystalline high molecular polymer; (ii) a conductive carbonized ceramic filler interspersed in the crystalline high molecular polymer, the particle size of which is between 0.1 μm and 50 μm, and the volume resistivity is less than 0.1 Omega-cm; and (iii) a conductive carbon black filler, dispersed in the crystalline high molecular polymer, wherein the weight ratio of the conductive carbon black filler to the conductive ceramic filler is between 1:90 and 1:4; Wherein the resistance reproducibility R100/Ri ratio of the PTC material layer is between 3 and 20, Ri is the initial resistance value, and R100 is the resistance value after 100 times of triggering. The overcurrent protection component according to claim 1, wherein the conductive carbonized ceramic filler accounts for 65% to 90% by weight of the PTC material layer, and the conductive carbon black filler accounts for 1% to 20% by weight of the PTC material layer. %. The overcurrent protection component according to claim 1, wherein the conductive carbonized ceramic filler accounts for 66% to 83% by weight of the PTC material layer, and the conductive carbon black filler accounts for 6% to 18% by weight of the PTC material layer. %. The overcurrent protection component according to claim 1, wherein the PTC material layer has a volume resistance value of between 0.1 and 0.3 Ω-cm. The overcurrent protection element according to claim 1, wherein the resistance reproducibility R100/Ri ratio of the PTC material layer is between 4 and 16. The overcurrent protection element according to claim 1, wherein the crystalline high molecular polymer is selected from the group consisting of a polyolefin polymer, a copolymer of an olefin monomer and an acrylic monomer, and an olefin monomer. Copolymers of vinyl alcohol monomers and combinations thereof. The overcurrent protection element according to claim 1, wherein the crystalline high molecular polymer is selected from the group consisting of high density polyethylene, medium density polyethylene, low density polyethylene, polyethylene wax, ethylene polymer, polypropylene, poly Vinyl chloride, polyvinyl fluoride, ethylene-acrylic acid copolymers, ethylene-acrylic acid co-polymers, ethylene-vinyl alcohol copolymers, and combinations thereof. The overcurrent protection component according to claim 1, wherein the conductive carbonized ceramic filler is selected from the group consisting of tungsten carbide, vanadium carbide, titanium carbide, boron carbide, tantalum carbide, tantalum carbide, tantalum carbide, zirconium carbide, chromium carbide, and molybdenum carbide. And their combinations. The overcurrent protection element according to claim 1, wherein the conductive carbonized ceramic filler outer shape comprises a crushed shape, a polygonal shape, a spherical shape or a sheet shape. The overcurrent protection element according to claim 1, wherein the conductive carbon black filler has a particle size ranging from 15 nm to 75 nm. The overcurrent protection component of claim 1, wherein the conductive carbon black filler is between 1% and 20% by weight of the PTC material layer. The overcurrent protection component of claim 1, wherein the PTC material layer further comprises a non-conductive filler. The overcurrent protection component of claim 12, wherein the non-conductive filler is selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, magnesium hydroxide, or a combination thereof. The overcurrent protection element of claim 12, wherein the non-conductive filler has a particle size between 0.1 μm and 30 μm. The overcurrent protection component of claim 12 is capable of withstanding a voltage of 12V to 28V and capable of withstanding a current of 50 amps or less. The overcurrent protection component of claim 1, wherein the PTC material layer has a thickness greater than 0.1 mm. The overcurrent protection component according to claim 1, further comprising a two metal electrode sheet, the two metal electrode sheets being respectively connected to the two metal foil sheets.