CN100472672C - High voltage resistant overcurrent protection element and manufacturing method thereof - Google Patents

Abstract

The overcurrent protection element of the invention comprises a chemically cross-linked Positive Temperature Coefficient (PTC) substrate and two electrode foils. The manufacturing method of the overcurrent protection element comprises the following steps: a. providing a polymer mixture having PTC characteristics, which contains a first polymer having a functional group X, a second polymer having a functional group Y, and conductive particles, heating the mixture to a temperature higher than the softening point of the polymers, and kneading the mixture to give a polymer mixture having the characteristics of a crystalline thermoplastic; b. pressing the polymer mixture into a flaky polymer substrate; c. stacking and arranging the flaky polymer substrates into a laminated stacked polymer layer; d. attaching two electrode foils to the upper and lower surfaces of the layered stacked polymer layers; e. and hot-pressing the upper and lower electrode foils and the layered stacked polymer layer between the upper and lower electrode foils to generate in-situ chemical crosslinking reaction of the functional group X and the functional group Y so as to form a chemically crosslinked PTC substrate. The chemically cross-linked PTC substrate of the present invention can withstand high voltages of about 600 volts.

Description

High voltage overcurrent protection element and manufacturing method thereof

technical field

The invention relates to a high voltage overcurrent protection element and its manufacturing method, in particular to a high voltage overcurrent protection element with positive temperature coefficient (Positive Temperature Coefficient; PTC) characteristics and its manufacturing method.

Background technique

The resistance value of conventional PTC elements responds quite sensitively to temperature changes. When the PTC element is in normal use, its resistance can maintain the lowest value so that the circuit can operate normally. However, when the temperature rises to a critical temperature due to overcurrent or overtemperature, its resistance value instantly jumps to a high resistance state (for example, above 10 ⁴ ohm) and the excessive current is counteracted in reverse to achieve protection purpose of batteries or circuit components. Since the PTC element can effectively protect electronic products, it has been seen that the PTC element is integrated in various circuit elements to prevent damage from overcurrent.

US patents US 5,227,946 and US 5,195,013 disclose PTC elements, wherein the polymer contained therein is subjected to radiation to enhance its physical and electrical properties. Thereby, the high voltage withstand characteristic of the PTC element can be improved.

However, polymers irradiated by radiation are often accompanied by degradation, which breaks the original polymer into small molecules and loses the original physical and electrical properties. In addition, if cobalt 60 (Co ⁶⁰ ) gamma rays are used to irradiate, it takes a considerable amount of time to irradiate because of its low energy, which reduces throughput. If electron beam (E-beam) is used for irradiation, high heat is often generated to cause internal stress, and the manufacturing process is not easy to control, which affects the yield and quality, and its manufacturing cost is relatively high.

Contents of the invention

The object of the present invention is to provide a high-voltage overcurrent protection element and its manufacturing method, wherein the PTC polymer is linked by chemical cross-linking. In this way, not only the high-voltage-resistant characteristics of the overcurrent protection element can be improved, but also the disadvantages of cracking and internal stress easily caused by cross-linking by radiation irradiation can be avoided.

To achieve the above purpose, the present invention discloses a high voltage overcurrent protection element, which includes a chemically cross-linked PTC substrate and two electrode foils. The chemically cross-linked PTC substrate utilizes at least one sheet-shaped polymer substrate to be stacked and arranged to form a one-layer stacked polymer layer, and then undergoes a thermal compression step to chemically cross-link the at least one sheet-shaped polymer substrate. combined to form. The two electrode foils can be connected to a power source to allow current to flow through the chemically cross-linked PTC substrate.

A part of the chemical cross-linking process is first performed to form the sheet-like polymer substrate, which includes two steps: (1) mixing and (2) pressing. Regarding mixing, at first a first polymer, a second polymer, conductive carbon black, and other fillers (for example: magnesium hydroxide, Talc, etc.) are sent into a batch mixer for mixing, and passed Controlling the process conditions of mixing: temperature, rotating speed and time (for example, controlling the operating temperature of mixing above the softening point of the polymer), so as to limit the reaction rate of the first polymer and the second polymer, This forms a polymer mixture which is a copolymer with a first degree of crosslinking and has the characteristics of a crystalline thermoplastic.

The first polymer may be selected from one of the following: urea formaldehyde resin (urea formaldehyde), melamine resin (melamine resin), bismaleimide triazine resin (bismaleimide triazine), silicone plastic (silicone plastics) , random copolymer of ethylene and glycidyl methacrylate, and grafted or copolymerized polymers containing epoxy groups. Wherein the functional group X of the first polymer is selected from one of the following groups: amino group, aldehyde group, alcohol group, epoxy group and halogen group.

The second polymer may be selected from one of the following: ethylene acrylic acid copolymer (ethylene acrylic acid copolymer), acrylic acid grafted polyethylene (acrylic acid grafted polyethylene), maleic anhydride grafted or copolymerized polyethylene (maleic acid grafted polyethylene). anhydride grafted polyethylene ormaleic anhydride copolymerized polyethylene), maleic anhydride grafted polypropylene or maleic anhydridecopolymerized polypropylene, phenolic resin, unsaturated polyester resin and unsaturated polyester resin Sulfur resin (polysulfide resin). Wherein, the functional group Y of the second polymer is selected from one of the following: acid group, acid anhydride group and phenol group.

After compounding, a pressing step is carried out, and the polymer mixture is hot-pressed at a higher operating temperature to form a sheet-like polymer substrate having a sheet shape with a second degree of crosslinking. The operating temperature of the thermal pressing step is between 120°C and 250°C, and the operating time is between 0.5 hours and 24 hours, and the operating temperature and time are the same as those of the first polymer and the second polymer The composition is related to the reaction temperature. Wherein, because the temperature of forming the sheet-like polymer substrate is relatively high, the second degree of crosslinking will be greater than the first degree of crosslinking. The thickness of the sheet-like polymer substrate can be changed according to requirements, and it can be between 0.1 mm and 4 mm. Each sheet-like polymer substrate can exhibit similar resistivity (resistivity) after being processed under appropriate process conditions, and sheet-like polymer substrates with different resistances can also be prepared through different formulations, and the sheet-like polymer substrate Only a partial degree of chemical crosslinking (ie, the second degree of crosslinking) is present in the substrate.

After the part of the chemical cross-linking process is completed, at least one sheet of polymer substrates is stacked and arranged for thermocompression bonding, and then the upper and lower electrode foils are combined to perform another thermocompression bonding step to form a chemically crosslinked substrate. PTC substrate. The two steps of thermocompression bonding can also be changed to one stage, that is, a plurality of sheet-like polymer substrates are stacked and arranged and combined with upper and lower electrode foils to complete one-time pressing. In the present invention, the total thickness of the chemically cross-linked PTC substrates is less than 10 mm, and the number of sheet-shaped polymer substrates is between 2 and 10.

In addition, in order to make the chemically cross-linked PTC substrate have better high-pressure resistance properties, chemical cross-linking reaction control agents and modifiers can be added when mixing polymers, such as:

(1) Initiator (initiator) includes: anionic (anionic) initiator (for example: piperidine, phenol and 2-ethyl-4-methyl-imidazole), cationic (cationic) initiator (for example: borontrifluoride, BF ₃ -amine complex , PF ₅ and trifluoromethanesulfonic acid, etc.);

(2) Catalysts include: ammonium salt (for example: ethyl triphenylammonium bromide), phosphonium salt (for example: triethyl methylphosphonium acetate), metal alkoxides (for example: aluminumisopropoxide) , latent (latent) catalyst (for example: crystalline amine or core-shellpolymer with amine core, high dissociation temperature peroxide and azocompound, etc.);

(3) Dispersion agents include: polyethylene wax, stearic acid, zinc stearate, low molecular weight acrylate copolymer, etc.;

(4) Coupling agent (coupling agent) includes: aminosilane, epoxysilane, mercaptosilane, etc.;

(5) Flame retardants include: halogen or phosphorus flame retardant compounds, metal hydroxide compounds (eg: Al ₂ (OH) ₃ , Mg(OH) ₂ ), metal oxides (eg: ZnO, Sb ₂ O ₃ etc.);

(6) Plasticizers include: dibasic ester (for example: dimethyl succinate, dibutyl phthalate, dimethyl glutarate and dimethyl adipate, etc.);

(7) Organic or inorganic fillers include: polymer fluoride powder, talc, kaolin, SiO2 _, etc.;

(8) Antioxidants such as: pentaerythrityl-tetrakis [3-(3,5-di-tertbutyl-4-hydroxy-phenyl)-propionate] and the like.

In order to further strengthen the degree of chemical crosslinking of the chemically crosslinked PTC substrate, it may be followed by the step of thermal compression bonding. The chemically cross-linked PTC substrate is subjected to a heat treatment step, usually after 1 to 48 hours of heat treatment, wherein the maximum temperature of the heat treatment does not exceed 270°C, and the temperature of the heat treatment step depends on the functional group X and the functional group Y It depends on the reaction temperature, which is usually higher than the operating temperature of thermocompression.

Subsequently, the chemically crosslinked PTC substrate can be cut into smaller areas by conventional die punching or saw cutting with a diamond knife to form a chemically crosslinked PTC chip . The sawing method can avoid the stress concentration area (that is, the burr) caused by the punching process around the PTC substrate, thereby avoiding the degradation of the high-voltage resistance characteristic.

Finally, the metal terminal is connected to the upper and lower electrode foils by reflowing to form a high voltage overcurrent protection element.

The above-mentioned high voltage and overcurrent protection elements comprising chemically cross-linked PTC substrates all have high voltage resistance characteristics. If the electrode foil of the high-voltage overcurrent protection element is connected to a power supply, the voltage difference measured by the chemically cross-linked PTC substrate per 2mm thickness can reach up to 600 volts, that is, the chemically cross-linked PTC substrate per 2mm thickness The bottom can withstand a voltage of about 600 volts, and the thicker the chemically cross-linked PTC substrate can withstand a higher voltage.

Compared with the manufacturing method of the high-voltage overcurrent protection element manufactured by conventional radiation irradiation (radiation), the present invention has the following advantages: (1) Because the effect of chemical crosslinking is achieved by adopting the thermocompression method, there will be no damage caused by radiation irradiation. The phenomenon of breaking and aging of polymer bonds causes the PTC substrate to become stronger due to the chemical cross-linking reaction; (2) The time required for the chemical cross-linking reaction of the material by thermal compression is much less than that of the conventional high-voltage-resistant The material must go through the time required for high-dose radiation (>50Mrad), so the production speed can be greatly increased; (3) radiation radiation is often shielded by other objects so that the problem of uneven irradiation occurs, and the present invention can completely eliminate this problem Problem; (4) Electron beam (E-beam) radiation irradiation produces regional high heat, causing material damage, so the control range of material temperature is very narrow (<85 ℃) during irradiation, but the process condition of the material used in the present invention is not Limited by this temperature, the variation of the material quality affected by the temperature can also be greatly reduced; (5) the present invention has better cross-linking uniformity than radiation irradiation of the material, and the current density in the element under high voltage is also lower. More uniform, so that the electrical characteristics of high voltage resistance are also better.

Description of drawings

1, 2 and 3 show the high voltage overcurrent protection element and its manufacturing method of the present invention.

Detailed ways

An embodiment of the overcurrent protection device and its manufacturing method of the present invention will be described below with the aid of figures.

FIG. 1 is a sheet-like polymer substrate 10, which is manufactured through a part of chemical cross-linking process (including two steps of mixing and pressing). First, 3.85 grams of a first polymer (comprising 8% of a copolymer of glycidyl methylacrylate (glycidyl methylacrylate, GMA for short) and polyethylene), a second polymer (comprising 0.9% maleic anhydride) Branched polyethylene (maleic anhydride graftedpolyethylene)) 1.65 grams, carbon black RU43015.4 grams, magnesium hydroxide 11.55 grams, Talc6.60 grams and HDPE15.95 grams are added in a batch mixer for mixing, and by controlling The process conditions of kneading: temperature 160° C., rotation speed 60 rpm and time 9 minutes, to form a polymer mixture with the first degree of crosslinking and the characteristics of crystalline thermoplastics. After mixing, the polymer mixture was hot-pressed under the operating conditions of 150°C, 1200 psi, and 0.1 hour to form a sheet-like polymer substrate 10 with a thickness of 1.2 cm and a second degree of crosslinking. That is, first mix the first polymer, the second polymer, the chemical crosslinking reaction control agent and the modifying agent, and control the process conditions (such as temperature, rotation speed, time) to limit the first The reaction rate of the polymer and the second polymer to form a partially reacted (with a first degree of crosslinking) polymer mixture, and then extrude a sheet-like polymer substrate with a second degree of crosslinking through a hot pressing process 10.

Afterwards, the three sheet-like polymer substrates 10 are stacked and arranged to form a layered stacked polymer layer 30 (refer to FIG. 2 ), and 1 ounce of nickel foil is combined as the upper and lower electrode foils 20 at the same time. Under the condition of 0.1 hour, carry out another thermal pressing to form a chemically cross-linked PTC substrate 15 (see FIG. 3 ). Wherein the upper and lower electrode foils 20 are in close and direct physical contact with the layered stacked polymer layer 30, and an in situ chemical crosslinking reaction of the functional group X and the functional group Y occurs. In this embodiment, the total thickness of the chemically cross-linked PTC substrate 40 and the upper and lower electrode foils 20 is 3.6 mm. Subsequently, the chemically cross-linked PTC substrate 40 is cut into PTC chips with a length of 12.4 cm and a width of 7.9 cm by means of saw cutting with a diamond knife, and then the metal terminals can be connected to the upper, The lower electrode foil 20 forms a high voltage overcurrent protection element 1 .

In order to further strengthen the degree of chemical crosslinking of the chemically crosslinked PTC substrate 40, the chemically crosslinked PTC substrate 40 can be subjected to a heat treatment step of 10 hours at 150° C., and the chemically crosslinked PTC after the heat treatment The substrate 40 can pass the high voltage withstand test under the conditions of a voltage of 600 volts and a current of 3 amperes, with power on for 1 second and then power off for 60 seconds.

The technical content and technical features of the present invention have been disclosed above, but those skilled in the art can still make various replacements and modifications based on the teaching and disclosure of the present invention without departing from the spirit of the present invention. Therefore, the protection scope of the present invention should not be limited to the contents disclosed in the embodiments, but should include various replacements and modifications that do not depart from the present invention, and are covered by the following claims.

Claims (12)

1. the manufacture method of a high voltage withstanding over current protection element is characterized in that comprising the following step:

At least one macromolecule mixture is provided, it is heated to second polymer and the conduction powder that first polymer, with functional group X has functional group Y more than the described polymer softening point and carries out mixing, it is one of following that the functional group X that described first polymer is had is selected from: amino, aldehyde radical, alcohol radical, epoxy radicals and halogen, the functional group Y that described second polymer is had are selected from one of following: acidic group, anhydride group and phenolic group.Wherein said macromolecule mixture has positive temperature coefficient (PTC) characteristic and has the characteristic of crystalline thermoplastic plastics;

Described macromolecule mixture is manufactured plurality of sheet-like macromolecule substrate through process for pressing;

Described plurality of sheet-like macromolecule substrate stacked arrangement is become a stratiform pile up polymeric layer;

Two electrode foils are connected in layered upper and lower surface of piling up polymeric layer; With

Described two electrode foils of hot pressing and the layered polymeric layer that piles up therebetween, described two electrode foils are contacted with the layered tight also direct physical of polymeric layer of piling up, and original place (in situ) chemical crosslink reaction of generation functional group X and functional group Y, to form a chemical crosslinking PTC substrate.

2. the manufacture method of high voltage withstanding over current protection element according to claim 1 is characterized in that described first polymer is selected from: the high molecular polymer that contains epoxy radicals grafting or combined polymerization.

3. the manufacture method of high voltage withstanding over current protection element according to claim 1 is characterized in that described second polymer is selected from: maleic anhydride grafting or combined polymerization polyethylene, maleic anhydride grafting or combined polymerization polypropylene.

4. the manufacture method of high voltage withstanding over current protection element according to claim 1; it is characterized in that described macromolecule mixture has one first crosslinking degree; described sheet macromolecule substrate has one second crosslinking degree, and wherein said second crosslinking degree is greater than described first crosslinking degree.

5. the manufacture method of high voltage withstanding over current protection element according to claim 1 is characterized in that described macromolecule mixture is pressed into the operating temperature of described sheet macromolecule substrate step between 120 ℃ to 250 ℃ through process for pressing.

6. the manufacture method of high voltage withstanding over current protection element according to claim 1 is characterized in that described macromolecule mixture is pressed into the operating time of described sheet macromolecule substrate step between 0.5 hour to 24 hours through process for pressing.

7. the manufacture method of high voltage withstanding over current protection element according to claim 1, the thickness that it is characterized in that described sheet macromolecule substrate between 0.1mm between the 4mm.

8. the manufacture method of high voltage withstanding over current protection element according to claim 1, the number that it is characterized in that described sheet macromolecule substrate is between 2 to 10.

9. the manufacture method of high voltage withstanding over current protection element according to claim 1 is characterized in that comprising in addition a heat treatment step of strengthening the crosslinking degree of described chemical crosslinking PTC substrate.

10. the manufacture method of high voltage withstanding over current protection element according to claim 9, the operating time that it is characterized in that described heat treatment step, operating temperature is the highest to be no more than 270 ℃ between 1 to 48 hour.

11. the manufacture method of high voltage withstanding over current protection element according to claim 1 is characterized in that comprising in addition one with the pluralize sawing step of a chemical crosslinking PTC chip of described chemical crosslinking PTC substrate sawing.

12. the manufacture method of high voltage withstanding over current protection element according to claim 11 is characterized in that described sawing step utilizes the die-cut or diamond cutter sawing of mould.

Images