TWI726245B - Overcurrent protection device - Google Patents

Abstract

An overcurrent protection device includes a first electrode, a second electrode, and a positive temperature coefficient multilayer structure including a first polymer layer, a second polymer layer, and a third polymer layer. The first polymer layer is joined to the first electrode and has a first polymer substrate made of a first polymer composition. The second polymer layer has perforations and has a second polymer substrate made of a second polymer composition. The third polymer layer is joined to the second electrode and has a third polymer substrate made of a third polymer composition. The overcurrent protection device of the present invention has both low initial resistance and sufficient peel strength.

Description

Overcurrent protection device

The present invention relates to an overcurrent protection device, in particular to an overcurrent protection device comprising three polymer layers, and the polymer substrates of the polymer layers are made of different polymer compositions.

Referring to FIG. 1, since the positive temperature coefficient (PTC) overcurrent protection device has a PTC effect, it can be used as a circuit protection device 1. The conventional circuit protection device 1 includes a PTC polymer layer 11 and two electrodes 12 attached to two opposite surfaces of the PTC polymer layer 11. The PTC polymer layer 11 includes a crystalline region and an amorphous region. The polymer substrate and a particulate conductive filler are dispersed in the amorphous region of the polymer matrix and form a continuous conductive path for electrically connecting the electrodes 12. The PTC effect refers to a phenomenon in which when the temperature of the crystalline region is increased to its melting point, the crystals in the crystalline region begin to melt, thereby generating a new amorphous region. When the new amorphous region is increased to the extent that it merges into the original amorphous region, the conductive path of the particulate conductive filler will be transformed into discontinuity and the resistance of the PTC polymer layer 11 will be greatly increased, causing the There is no electrical conduction between the electrodes 12.

The circuit protection device 1 is suitable for protecting electronic equipment, and the material of the polymer substrate is selected based on the operating current and operating voltage of the electronic equipment. The polymer substrate of the PTC polymer layer 11 is usually made of a polyolefin It is made of the composition of the base. However, the circuit protection device 1 may have unsatisfactory conductivity due to the low adhesion between the PTC polymer layer 11 and the electrodes 12.

US Patent 6,238,598 describes a PTC polymer blend composition and a circuit protection device. The PTC polymer blend composition includes a non-grafted polyolefin, a grafted polyolefin, and a conductive particulate material. The circuit protection device includes a PTC element including the PTC polymer blend composition, and two electrodes connected to opposite sides of the PTC element. With the grafted polyolefin contained in the PTC polymer blending composition, the circuit protection device has better electrical stability, and the degree of adhesion between the PTC element and the electrodes is better.

However, the volume resistance of the circuit protection device described in the aforementioned US Patent No. 6,238,598 is not less than 0.15 ohm-cm. If the grafted polyolefin is excluded from the PTC polymer blending composition, the volume resistance can be reduced to close to 0.1 ohm-cm, but the peeling strength between the PTC element and the electrodes will decrease accordingly To 0.4 kg/cm ² , the PTC element and the electrodes can be easily separated, causing malfunction or damage to the circuit protection device.

Therefore, an overcurrent protection device with good electrical conductivity and good fit is still to be developed.

Therefore, one objective of the present invention is to provide an overcurrent protection device that can overcome at least one of the above-mentioned disadvantages of the prior art.

Therefore, the overcurrent protection device of the present invention includes a first electrode, a second electrode and a positive temperature coefficient (PTC) multilayer structure.

The positive temperature coefficient multilayer structure is disposed between the first electrode and the second electrode, and includes a first polymer layer, a second polymer layer, and a third polymer layer.

The first polymer layer is joined to the first electrode. The first polymer layer has a first polymer substrate and a first particulate conductive filler dispersed in the first polymer substrate. The polymer substrate is made of a first polymer composition.

The second polymer layer is joined to the first polymer layer, and the second polymer layer has a second polymer substrate and a second particulate conductive filler dispersed in the second polymer substrate. The second polymer substrate is made of a second polymer composition, and the second polymer layer has at least one perforation.

The third polymer layer is joined and disposed between the second polymer layer and the second electrode, and the third polymer layer has a third polymer substrate and a dispersion in the third polymer substrate The third particulate conductive filler, the third polymer substrate is made of a third polymer composition.

The second polymer composition contains a non-grafted polyolefin and substantially no grafted polyolefin.

The first polymer composition and the third polymer composition each contain a grafted polyolefin.

Therefore, another object of the present invention is to provide an overcurrent protection device including a first electrode, a second electrode and a positive temperature coefficient multilayer structure.

The positive temperature coefficient multilayer structure is disposed between the first electrode and the second electrode, and includes a first polymer layer, a second polymer layer, and a third polymer layer.

The first polymer layer is joined to the first electrode. The first polymer layer has a first polymer substrate and a first particulate conductive filler dispersed in the first polymer substrate. The polymer substrate is made of a first polymer composition.

The second polymer layer is joined to the first polymer layer, and the second polymer layer has a second polymer substrate and a second particulate conductive filler dispersed in the second polymer substrate. The second polymer substrate is made of a second polymer composition.

The third polymer layer is joined and disposed between the second polymer layer and the second electrode, and the third polymer layer has a third polymer substrate and a dispersion in the third polymer substrate The third particulate conductive filler, the third polymer substrate is made of a third polymer composition.

The second polymer composition contains a non-grafted polyolefin and substantially no grafted polyolefin.

The first polymer composition and the third polymer composition each contain a grafted polyolefin.

The effect of the present invention is that the overcurrent protection device of the present invention has both low initial resistance and sufficient peel strength.

The content of the present invention will be described in detail below:

Preferably, the aperture range of the perforation is 0.8-1.2 mm.

Preferably, the second polymer layer has a plurality of perforations and the perforation density ranges from 4-16 holes/cm ² .

Preferably, the first polymer composition and the third polymer composition each contain a polyolefin grafted with an unsaturated carboxylic anhydride.

Preferably, at least one of the first polymer composition and the third polymer composition further contains a non-grafted polyolefin.

Preferably, the non-grafted polyolefin is high density polyethylene.

Preferably, the total weight of the first polymer composition is 100 wt%, and the content of the grafted polyolefin of the first polymer composition ranges from 25 to 100 wt%.

Preferably, the total weight of the third polymer composition is 100 wt%, and the content of the grafted polyolefin of the third polymer composition ranges from 25 to 100 wt%.

Preferably, the first particulate conductive filler, the second particulate conductive filler and the third particulate conductive filler are each selected from carbon black powder, metal powder, conductive ceramic powder or a combination thereof. More preferably, the first particulate conductive filler, the second particulate conductive filler and the third particulate conductive filler are all carbon black powder.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same numbers.

Referring to FIG. 2, a first embodiment of the overcurrent protection device of the present invention includes a first electrode 2, a second electrode 4, and a positive temperature coefficient ( PTC) Multilayer structure 3.

The positive temperature coefficient multilayer structure 3 includes a first polymer layer 31, a second polymer layer 32 and a third polymer layer 33.

The first polymer layer 31 is joined to the first electrode 2, and the first polymer layer 31 has a first polymer substrate and a first particulate conductive filler dispersed in the first polymer substrate, The first polymer substrate is made of a first polymer composition.

The second polymer layer 32 is joined to the first polymer layer 31. The second polymer layer 32 has a second polymer substrate and a second particulate conductive material dispersed in the second polymer substrate. Filler, the second polymer substrate is made of a second polymer composition. Furthermore, the second polymer layer 32 may further have at least one perforation 320. The aperture (d) of the perforation 320 ranges from 0.8 to 1.2 mm, and its area ranges from 0.5026 to 1.1310 mm ² .

The third polymer layer 33 is joined and disposed between the second polymer layer 32 and the second electrode 4, and the third polymer layer 33 has a third polymer substrate and a dispersion in the third polymer layer. The third particulate conductive filler in the substrate, and the third polymer substrate is made of a third polymer composition.

The second polymer composition contains a non-grafted polyolefin and substantially no grafted polyolefin.

Further, the non-grafted polyolefin of the second polymer composition is high density polyethylene (HDPE).

In some specific embodiments of the present invention, the second polymer layer 32 is disposed between the first polymer layer 31 and the third polymer layer 33. It may have a multi-layer structure and may have a plurality of self The first polymer layer 31 extends in the direction of the third polymer layer 33 to be stacked with layered portions. The layered portions of the second polymer layer 32 can be made of the same or different materials.

The first polymer composition and the third polymer composition each contain a grafted polyolefin.

Further, the first polymer composition and the third polymer composition each contain a polyolefin grafted with an unsaturated carboxylic anhydride. Therefore, the overcurrent protection device including the above-mentioned positive temperature coefficient multilayer structure can be called a cocktail type overcurrent protection device.

In some embodiments of the present invention, the first polymer composition further contains a non-grafted polyolefin. The non-grafted polyolefin of the first polymer composition may be high density polyethylene.

In some embodiments of the present invention, the third polymer composition further contains a non-grafted polyolefin. The non-grafted polyolefin of the third polymer composition may be high density polyethylene.

In some specific embodiments of the present invention, the total weight of the first polymer composition is 100 wt%, and the content of the grafted polyolefin of the first polymer composition ranges from 25 to 100 wt% . Taking the total weight of the third polymer composition as 100 wt%, the content of the grafted polyolefin in the third polymer composition ranges from 25 to 100 wt%.

Examples of the first particulate conductive filler, the second particulate conductive filler, and the third particulate conductive filler include carbon black powder, metal powder, conductive ceramic powder, or a combination thereof.

In some specific embodiments of the present invention, the first particulate conductive filler, the second particulate conductive filler, and the third particulate conductive filler are all carbon black powders.

Referring to FIGS. 3 and 4, a second embodiment of the overcurrent protection device of the present invention is shown in the diagram. The overcurrent protection device of the second embodiment is similar to the first embodiment, but the difference is that in the second embodiment, the second polymer layer 32 has a plurality of perforations 320 and the perforation density ranges from 4-16. Hole/cm ² .

The present invention will be further described with reference to the following examples, but it should be understood that these examples are for illustrative purposes only and should not be construed as limitations to the implementation of the present invention.

Example

＜Example 1 (E1) ＞

10 g HDPE (purchased from Taiwan Plastics Industry Co., Ltd., product model: HDPE9002) as non-grafted polyolefin, and 10 g of HDPE grafted with maleic anhydride (MA-g-HDPE, purchased from DuPont, product model : MB100D) As a polyolefin grafted with unsaturated carboxylic anhydride, it is used as the first polymer composition of the first polymer layer 31 and the third polymer composition of the third polymer layer 33. 30 g carbon black powder (purchased from Columbian Chemicals Co., product model: Raven 430UB, DBP/D of 0.95, bulk density of 0.53 g/cm ³ ) is used as the first polymer layer 31 and the third polymer layer 33 granular conductive filler. 20 g HDPE (purchased from Taiwan Plastics Industry Co., Ltd., product model: HDPE9002) is used as the second polymer composition of the second polymer layer 32. 30 g of carbon black powder (available from Columbian Chemicals Co., product model: Raven 430UB) is used as the particulate conductive filler of the second polymer layer 32. Table 1 shows the formulation ratio of the above polymer composition and carbon black powder.

The above polymer composition was mixed with carbon black powder in a mixer (brand: Brabender), and the ingredients were mixed at a temperature of 200°C and a stirring speed of 30 rpm for 10 minutes to obtain three mixtures. . Then, under the conditions of a hot pressing temperature of 200°C and a hot pressing pressure of 80 kg/cm ² , the mixture was placed in a mold for hot pressing for 4 minutes to form a first polymer layer 31 with a thickness of 0.12 mm. , The second polymer layer 32 and the third polymer layer 33. The first polymer layer 31 and the third polymer layer 33 are attached to two opposite surfaces of the second polymer layer 32.

Then, two pieces of nickel-plated copper foil (as the first electrode 2 and the second electrode 4) are attached to the first polymer layer 31 and the third polymer layer 33 opposite to the second polymer layer. 32 on the surface, and hot press at 200 ℃ and 80 kg/cm ² for 4 min to form a PTC polymer laminate with a thickness of 0.42 mm. After cutting the PTC polymer laminate into multiple small pieces with an area of 8 mm × 8 mm, each small piece was irradiated with Co-60 γ rays with a total radiation dose of 150 kGy to form multiple examples 1 (E1) The test sample.

＜Example 2 To 4 (E2-E4) ＞

The process conditions of the test samples of Examples 2 to 4 (E2-E4) are similar to those of Example 1. The difference lies in the HDPE and MA-g-HDPE of the first polymer composition and the third polymer composition The amount of usage changed as shown in Table 1.

＜Example 5 To 8 (E5-E8) ＞

The process conditions of the test samples of Examples 5 to 8 (E5-E8) are similar to those of Examples 1 to 4, respectively. The difference lies in stacking the first polymer layer 31, the second polymer layer 32, and the Before the third polymer layer 33, the second polymer layer 32 is formed with a plurality of perforations 320 (each perforation has a hole diameter of 1.0 mm and an area of 0.7854 mm ² ), and the perforation density is 9 holes/cm ² .

＜Comparative example 1 (CE1) ＞

The process conditions of the test sample of Comparative Example 1 (CE1) are similar to those of Example 1. The difference is that the test sample of Comparative Example 1 does not have the first polymer layer 31 and the third polymer layer 33, and the second polymer layer The thickness of the object layer 32 is 0.36 mm, and two pieces of nickel-plated copper foil are attached to two opposite surfaces of the second polymer layer 32 respectively.

＜Comparative example 2 And 3 (CE2 And CE3) ＞

The process conditions of the test samples of Comparative Examples 2 and 3 (CE2 and CE3) are similar to those of Examples 1 and 2, respectively. The difference is that the test samples of Comparative Examples 2 and 3 do not have the second polymer layer 32 and the The third polymer layer 33, the thickness of the first polymer layer 31 is 0.36 mm, and two pieces of nickel-plated copper foil are attached to the two opposite surfaces of the first polymer layer 31, respectively.

＜Comparative Example 4 (CE4) ＞

The process conditions of the test sample of Comparative Example 4 (CE4) are similar to those of Example 1. The difference is that in the test sample of Comparative Example 4, the first polymer composition, the second polymer composition, and the third The polymer composition is composed of HDPE and carbon black powder, and the usage amount of HDPE and carbon black powder is changed as shown in Table 1.

＜Comparative Example 5 (CE5) ＞

The process conditions of the test sample of Comparative Example 5 (CE5) are similar to those of Example 1. The difference is that in the test sample of Comparative Example 5, the first polymer composition, the second polymer composition, and the second polymer composition Table 1 shows the changes in the usage amount of HDPE, MA-g-HDPE and carbon black powder of the tripolymer composition.

Performance Testing

[ Initial resistance test (Initail resistance at room temperature test)]

In each example and each comparative example, 10 samples were tested using a micro-ohmmeter. The initial resistances of the test samples of E1-E8 and CE1-CE5 at 25°C were measured, and the average values are shown in Table 2.

The results show that the initial resistance of E1 is lower than CE2 and CE5, and the initial resistance of E2 is lower than CE3, which indicates that by including the second polymer layer 32, the resistance of the overcurrent protection device can be effectively reduced. In addition, the results show that the initial resistance of E5 is lower than E1, the initial resistance of E6 is lower than E2, the initial resistance of E7 is lower than E3, and the initial resistance of E8 is lower than E4. The perforation 320 can reduce the resistance of the overcurrent protection device. 【Table 2】

[ Peel strength test (Peel strength test)]

Ten samples were tested for peel strength in each example and each comparative example. Clamp the first electrode 2 and the second electrode 4 with a tensile machine, stretch the first electrode 2 and the second electrode 4 at a speed of 2 mm/s, and record the test samples of E1-E8 and CE1-CE5 The average value of the peel strength is shown in Table 2.

The results show that the peel strength of E1-E8 is greater than 1.5 kg/cm ² , and the initial resistance and peel strength of E2 and E6 are both low. Although the initial resistances of CE1 and CE4 are also low, their peel strength is less than 0.4 kg/cm ² , which means that the first electrode 2 and the second electrode 4 are easily separated from the polymer layer.

In summary, by including the first polymer layer 31, the second polymer layer 32, and the third polymer layer 33 each made of a specific polymer composition, the overcurrent protection device has both low initial resistance and Sufficient peel strength.

[ Resistance at different temperatures ]

In each example and each comparative example, 10 samples were tested for resistance at 25-185°C. The resistance of the test samples of E1-E8 and CE1-CE5 were gradually measured from 25°C to 185°C at a heating rate of 2°C/min. The average value of the resistance at 140°C is shown in Table 2, and E6 and The relationship between temperature and resistance of the test sample of CE1 is shown in Figure 5.

The results show that the average value of the resistance of the test samples of CE1, CE3 and CE4 at 140°C is lower than that of E2 and E6. In addition, the results show that the resistance of the test samples of E6 and CE1 at 25°C is equivalent, but the resistance of E6 at 140°C is higher than that of CE1.

[ Toggle cycle test (Switching cycle test)]

For each embodiment and each comparative example, 10 samples were tested in a switching cycle. The test samples of E1-E8 and CE1-CE5 were turned on for 60 seconds with a voltage of 16 Vdc and a current of 100 A, and then turned off for 60 seconds, so that 6000 switching cycles were performed. Measure the resistance (Ri and Rf) of each test sample before the start and after 6000 cycles, and determine the average resistance change rate of each example and each comparative example [(Rf-Ri)/Ri×100%], And calculate the switching cycle pass ratio of each embodiment and each comparative example (n/10×100%, n represents the number of test samples that passed the switching cycle test without burning). The results of the switching cycle test are shown in Table 2.

The results show that all test samples of E1-E8 passed the switching cycle test (the switching cycle pass rate was 100%). The switching cycle pass rate of the test samples of CE1, CE3 and CE4 is only 20%-30% and their resistance at 140℃ is also low, which means that the test samples of CE1, CE3 and CE4 are easily damaged under a voltage of 16 Vdc . In addition, the average resistance change rate of E1-E8 test samples is significantly lower than CE1-CE5.

[ Aging test (Aging test)]

Ten samples were subjected to aging test for each example and each comparative example. Apply a voltage of 16 Vdc and a current of 100 A to the test samples of E1-E8 and CE1-CE5 for 1000 hours. Measure the resistance (Ri and Rf) of each test sample before and after 1000 hours of application, and determine the average resistance change rate [(Rf-Ri)/Ri×100%] of each example and each comparative example, And calculate the aging pass rate of each embodiment and each comparative example (n/10×100%, n represents the number of test samples that passed the aging test without being burnt). The results of the aging test are shown in Table 2.

The results show that all test samples of E1-E8 have passed the aging test (aging pass rate is 100%). The aging pass rate of the test samples of CE1, CE3 and CE4 is only 10%-20% and their resistance at 140°C is also low, which means that the test samples of CE1, CE3 and CE4 are easily damaged under a voltage of 16 Vdc. In addition, the average resistance change rate of E1-E8 test samples is significantly lower than CE1-CE5.

In summary, by including the first polymer layer 31, the second polymer layer 32, and the third polymer layer 33 each made of a specific polymer composition, the overcurrent protection device of the present invention has both low The initial resistance and sufficient peel strength can indeed achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to This invention patent covers the scope.

1: Current protection device 11: PTC polymer layer 12: Electrode 2: First electrode 3: Positive temperature coefficient multilayer structure 31: First polymer layer 32: Second polymer layer 320: Perforation 33: Third polymer layer 4: second electrode

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, in which: [Figure 1] is a schematic cross-sectional view of an existing over-current protection device; [Figure 2] is the over-current protection of the present invention An exploded perspective view of the first embodiment of the device; [Figure 3] is a schematic cross-sectional view of the second embodiment of the overcurrent protection device of the present invention; [Figure 4] is an exploded perspective view of the second embodiment ; And [Figure 5] is a temperature-resistance graph of the test samples of Example 6 and Comparative Example 1.

2: The first electrode

3: Positive temperature coefficient multilayer structure

31: The first polymer layer

32: second polymer layer

320: perforation

33: third polymer layer

4: second electrode

Claims (14)

An overcurrent protection device, comprising: a first electrode and a second electrode; and a positive temperature coefficient multilayer structure, arranged between the first electrode and the second electrode, the positive temperature coefficient multilayer structure comprising: a first electrode A polymer layer joined to the first electrode, the first polymer layer has a first polymer substrate and a first particulate conductive filler dispersed in the first polymer substrate, the first polymer The substrate is made of a first polymer composition, a second polymer layer is joined to the first polymer layer, and the second polymer layer has a second polymer substrate and a dispersed The second particulate conductive filler in the second polymer substrate, the second polymer substrate is made of a second polymer composition, the second polymer layer has a plurality of perforations, and the perforations The pore size range is 0.8-1.2mm and the perforation density range is 4-16 holes/cm ² , and a third polymer layer is joined and disposed between the second polymer layer and the second electrode, and the third The polymer layer has a third polymer substrate and a third particulate conductive filler dispersed in the third polymer substrate, and the third polymer substrate is made of a third polymer composition Wherein, the second polymer composition is a non-grafted polyolefin; and wherein, the first polymer composition and the third polymer composition are each a grafted polyolefin or the grafted polyolefin The combination of the polyolefin and the non-grafted polyolefin. The overcurrent protection device according to claim 1, wherein the first polymer composition and the third polymer composition are each a polyolefin grafted with an unsaturated carboxylic anhydride or the unsaturated carboxylic anhydride grafted The combination of the polyolefin and the non-grafted polyolefin. The overcurrent protection device according to claim 1, wherein at least one of the first polymer composition and the third polymer composition is one of the grafted polyolefin and the non-grafted polyolefin combination. The overcurrent protection device according to any one of claims 1 or 3, wherein the non-grafted polyolefin is high-density polyethylene. The overcurrent protection device according to claim 1, wherein the total weight of the first polymer composition is 100% by weight, and the content of the grafted polyolefin of the first polymer composition ranges from 25 to 100% by weight %. The overcurrent protection device according to claim 1, wherein, based on the total weight of the third polymer composition being 100% by weight, the content of the grafted polyolefin of the third polymer composition is in the range of 25-100% by weight %. The overcurrent protection device according to claim 1, wherein the first particulate conductive filler, the second particulate conductive filler and the third particulate conductive filler are each selected from carbon black powder, metal powder, conductive Ceramic powder or a combination thereof. The overcurrent protection device according to claim 7, wherein the first particulate conductive filler, the second particulate conductive filler and the third particulate conductive filler are all carbon black powder. An overcurrent protection device, comprising: a first electrode and a second electrode; and A positive temperature coefficient multilayer structure is disposed between the first electrode and the second electrode, the positive temperature coefficient multilayer structure includes: a first polymer layer joined to the first electrode, the first polymer layer having A first polymer substrate and a first particulate conductive filler dispersed in the first polymer substrate, the first polymer substrate is made of a first polymer composition, and a second The polymer layer is joined to the first polymer layer. The second polymer layer has a second polymer substrate and a second particulate conductive filler dispersed in the second polymer substrate. The polymer substrate is made of a second polymer composition, and a third polymer layer is joined and disposed between the second polymer layer and the second electrode, and the third polymer layer has A third polymer substrate and a third particulate conductive filler dispersed in the third polymer substrate, the third polymer substrate is made of a third polymer composition; wherein, the The second polymer composition is a non-grafted polyolefin; and wherein, the first polymer composition and the third polymer composition are each a grafted polyolefin or the grafted polyolefin and The combination of non-grafted polyolefins. The overcurrent protection device according to claim 9, wherein the non-grafted polyolefin of the second polymer composition is high-density polyethylene. The overcurrent protection device according to claim 9, wherein the first polymer composition and the third polymer composition are each an unsaturated carboxylic anhydride The grafted polyolefin or the combination of the unsaturated carboxylic anhydride grafted polyolefin and the non-grafted polyolefin. The overcurrent protection device according to claim 9, wherein at least one of the first polymer composition and the third polymer composition is one of the grafted polyolefin and the non-grafted polyolefin combination. The overcurrent protection device according to claim 9, wherein the total weight of the first polymer composition is 100% by weight, and the content of the grafted polyolefin of the first polymer composition ranges from 25 to 100% by weight %. The overcurrent protection device according to claim 9, wherein, based on the total weight of the third polymer composition being 100% by weight, the content of the grafted polyolefin of the third polymer composition is in the range of 25-100 wr %.

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