CN111863362A - Manufacturing method of over-current protection element with reliable weather resistance - Google Patents
Manufacturing method of over-current protection element with reliable weather resistance Download PDFInfo
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- CN111863362A CN111863362A CN202010844380.2A CN202010844380A CN111863362A CN 111863362 A CN111863362 A CN 111863362A CN 202010844380 A CN202010844380 A CN 202010844380A CN 111863362 A CN111863362 A CN 111863362A
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- H01—ELECTRIC ELEMENTS
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- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/02—Apparatus or processes specially adapted for manufacturing resistors adapted for manufacturing resistors with envelope or housing
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- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
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Abstract
The invention belongs to the technical field of electronic components, and particularly relates to a manufacturing method of an overcurrent protection element with reliable weather resistance. In the prior art, the low-resistance thermistor can be used as a conductive substrate by optimizing the manufacturing process of the high-weather-resistance reliable overcurrent protection element, and the side surface of the low-resistance thermistor is coated with the moisture-proof insulating encapsulating layer, so that the high-weather-resistance overcurrent protection element has good moisture-proof capability and side surface insulating capability and stable weather resistance. And because the manufacturing method of the low-resistance thermistor is ingenious, the whole overcurrent protection element has the advantages of good consistency and stable and reliable performance.
Description
Technical Field
The invention belongs to the technical field of electronic components, and particularly relates to a manufacturing method of an overcurrent protection element with reliable weather resistance.
Background
A Polymer Positive Temperature Coefficient (PPTC) overcurrent protection element (PPTC for short) refers to a characteristic that a resistor reacts sensitively to Temperature change in a certain Temperature range, and when a current or a Temperature rises, a resistance value gradually increases, and a loop current decreases, so as to achieve an overcurrent protection effect; when the current or the temperature returns to normal, the resistance value returns to the low resistance state, and the device can be continuously used. The element can be used as a material for sensing current or temperature, is widely applied to an over-current or over-temperature protection circuit, and relates to the fields of automobile application, industrial control application, household appliance application, computer portable equipment application, mobile phone Bluetooth and other consumer electronics.
The polymer PPTC patch structure product is shown in figure 1 and comprises an electrode A1 ', an electrode B2 ', a PPTC composite material 3 ', a PP layer 4 ' and a PPTC copper foil 5 '; in the prior art, four sides of a PPTC composite material 3 'in a polymer PPTC patch structure product are exposed to the air, a conductive filler in the PPTC composite material 3' is easily oxidized or the PPTC composite material 3 'is corroded by moisture, and the like, and the longer the PPTC composite material 3' is exposed to the air, the higher the resistance of the product is, the more the normal rated working current characteristics of the product are affected, and the performance of the product, such as the normal service life, is affected.
In addition, the general process flow of the self-healing fuse in the prior art is as follows: firstly, polymer and a conductive object are processed in an open mill mode or in a mixing mode to form a compound, then the compound is pressed to form a PPTC (polymer PTC) chip, and finally the PPTC chip is punched and cut or processed into the self-recovery fuse through a PCB. The procedure is relatively simple, but the consistency is poor. The Polymer PTC (PPTC) material is compounded and processed by one or more conductive particles, one or more crystalline or semi-crystalline polymer materials and various additives, and the existing compound processing mode mainly selects open mill type processing or mixing processing, and then is crushed into particles or granulated; this mill processing mode is open, needs the artifical incessant packing of manual work to mix, and it is inhomogeneous to have the packing, and the material inside and the pollution risk are wrapped up in to the moisture. Non-uniform packing can lead to poor resistivity uniformity and unstable performance. The mixing processing mode is mixing in a closed chamber, but has the defects of inaccurate internal temperature control and poor mixing uniformity, and finally causes uneven distribution of the resistance value of the material.
In the process of pressing and processing the composite into the PPTC chip, electrode copper foils are covered on the upper surface and the lower surface of the PPTC composite material which is processed through compounding through a press; when in pressing, a special buffer material, namely Teflon demoulding cloth is needed, and the special buffer material and the steel plate form a multilayer structure. The process has the problems of poor thickness consistency and poor mixing uniformity of the composite material, so that the resistance distribution is not uniform enough. The reason for poor thickness consistency is that the multi-layer structure is formed by laminating and pressing a buffer material, Teflon demoulding cloth and a steel plate, and the defects of multiple positioning of lamination, large accumulated tolerance, uneven pressure and the like exist. The defects of the two processes cause the resistance value of the polymer self-recovery fuse (PPTC) to be uneven and the performance to be unstable.
The invention aims to provide a manufacturing method of an overcurrent protection element with reliable weather resistance, which takes a low-resistance thermistor as a conductive substrate, and the side surface of the thermistor is coated with a moisture-proof insulating encapsulating layer, so that the overcurrent protection element has good moisture-proof capability and side surface insulating capability and stable weather resistance. And because the manufacturing method of the low-resistance thermistor is ingenious, the whole overcurrent protection element has the advantages of good consistency and stable and reliable performance.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, the manufacturing method of the overcurrent protection element with reliable weather resistance is provided, and the overcurrent protection element takes a low-resistance thermistor as a conductive substrate, and a moisture-proof insulating encapsulating layer is coated on the side surface of the thermistor, so that the overcurrent protection element has good moisture-proof capability and side surface insulating capability, and is stable in weather resistance. And because the manufacturing method of the low-resistance thermistor is ingenious, the whole overcurrent protection element has the advantages of good consistency and stable and reliable performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
the manufacturing method of the over-current protection element with reliable weather resistance comprises the following steps:
firstly, mixing a polymer and a conductive substance together in a double-screw granulator by adopting a double-screw granulation processing mode and granulating to form a mixture;
secondly, melting and extruding the mixture obtained in the first step by adopting a single-screw extrusion processing technology in a single-screw extrusion molding machine to form a PPTC sheet material, and forming the sheet material between an upper electrode copper foil and a lower electrode copper foil to form a PPTC chip;
thirdly, performing electron beam irradiation treatment on the PPTC chip formed in the second step;
fourthly, stamping the PPTC chip, forming a low-resistance thermistor through a PCB (printed Circuit Board) processing technology, etching inner-layer circuits on an upper electrode copper foil and a lower electrode copper foil, sequentially laying a PP (polypropylene) layer and an outer-layer copper foil on the upper surface of the upper electrode copper foil, sequentially laying the PP layer and the outer-layer copper foil on the lower surface of the lower electrode copper foil, and performing vacuum lamination;
fifthly, etching an outer layer circuit on the outer layer copper foil to enable the outer layer copper foil to form a first electrode and a second electrode at two ends of the PP layer respectively, then forming a first groove and a second groove at two ends of the element main body respectively by adopting a drilling process, and then connecting the upper electrode copper foil and the first electrode by the first groove and connecting the lower electrode copper foil and the second electrode by the second groove through a treatment process of cleaning, removing glue, depositing copper and plating tin;
and sixthly, sealing the four side surfaces of the element main body by adopting a sealing process, and then performing thermocuring treatment, so that the low-resistance thermistor exposed in the air is completely encapsulated, but the first groove and the second groove are completely remained and are not encapsulated, and an encapsulating layer is formed. The upper surface and the lower surface of the whole product are not enveloped by the encapsulating layer, so that the welding strength of the product can be ensured.
As an improvement of the manufacturing method of the high-weather-resistance reliable overcurrent protection element, in the first step, the mass ratio of the polymer to the conductive substance is (2-10): (90-98). According to the volume ratio, the conductive substance accounts for 2-3 times of the polymer powder.
In the first step, the polymer is at least one of polyethylene, polyvinyl chloride, chlorinated polyethylene butadiene-acrylonitrile copolymer, polytetrafluoroethylene, polycarbonate, polyvinyl fluoride, maleic anhydride grafted polyethylene and polypropylene; the conductive substance is at least one of titanium carbide, vanadium carbide, zirconium carbide, tungsten carbide, niobium carbide, molybdenum carbide, titanium boride, vanadium boride, zirconium boride, niobium boride and titanium nitride.
As an improvement of the manufacturing method of the high-weather-resistance reliable overcurrent protection element, the particle size of the conductive substance is between 0.01 and 20 microns.
As an improvement of the manufacturing method of the overcurrent protection element with high weather resistance and reliability, the specific process of the twin-screw granulation processing in the first step is as follows: the polymer and the conductive substance are premixed and then added into the self-temperature-control heating material cylinder from the feeding port, the polymer and the conductive substance are uniformly mixed by the double screws and then extruded out of the discharging die head to form a mixture, and moisture is discharged through an exhaust hole and a vacuumizing hole which are formed in the self-temperature-control heating material cylinder in the mixing process.
As an improvement of the manufacturing method of the overcurrent protection element with high weather resistance and reliability, eight automatic temperature control heating material cylinders are arranged, wherein the temperature in the first automatic temperature control heating material cylinder farthest from the discharge die head is 120-150 ℃, the temperature from the second automatic temperature control heating material cylinder to the eighth automatic temperature control heating material cylinder is 235-275 ℃, and the temperature of the discharge die head is 235-275 ℃; the vacuum degree of the vacuumizing port is less than 500 Psi; the rotating speed of the double screws is 8-15 rpm. Because the density fall of the material is large, if the material is processed by adopting an early open mixing type or mixing type, the material is not well mixed, so that the resistance consistency of the material is poor, and the material is easy to wrap moisture or impurities to pollute the risk; the invention mixes the polymer and the conductive material uniformly, the gas is discharged through the vacuum-pumping port during the extrusion process, the moisture in the material can be discharged through the vent hole and the vacuum-pumping port during the processing process, the polymer material is ensured to have no moisture, the degree of automation is high, the discharging is stable, the mixing is uniform, and the material performance is stable.
As an improvement of the manufacturing method of the overcurrent protection element with high weather resistance and reliability, in the second step, the specific process of melt extrusion is as follows: adding the mixture obtained in the first step into a self-temperature-control heating high-wear-resistance material cylinder from a feeding area, heating the mixture by a high-wear-resistance single screw rod, and extruding the mixture from a forming die head to form a PPTC sheet material, wherein moisture is discharged through an exhaust hole and a vacuum exhaust port which are arranged on the self-temperature-control heating high-wear-resistance material cylinder in the mixing process;
the specific process for forming the sheet material between the upper electrode copper foil and the lower electrode copper foil comprises the following steps: and automatically laminating an upper electrode copper foil and a lower electrode copper foil on the upper surface and the lower surface of the PPTC sheet material respectively through an upper roller and a lower roller so as to form the PPTC chip.
As an improvement of the manufacturing method of the high-weather-resistance reliable overcurrent protection element, eight self-temperature-control heating high-wear-resistance material cylinders are arranged, wherein the temperature in the first self-temperature-control heating high-wear-resistance material cylinder farthest away from the forming die head is 120-150 ℃, the temperature from the second self-temperature-control heating high-wear-resistance material cylinder to the eighth self-temperature-control heating high-wear-resistance material cylinder is 235-275 ℃, and the temperature of the forming die head is 235-275 ℃; the vacuum degree of the vacuum exhaust port is less than 500 Psi; the temperature of the upper roller and the lower roller is 180-220 ℃; the rotating speed of the roller is set to be between 2 and 5 scales. And gas is included or released in the extrusion process and is discharged through the vacuumizing port, so that the polymer composite material is ensured to have no water vapor. The process has high automation degree, a vacuumizing function, moisture removal, high roller precision and capability of ensuring the thickness consistency of the rolled PPTC chip.
As an improvement of the manufacturing method of the high-weather-resistance reliable overcurrent protection element, the thickness of the PPTC chip is 0.18-2.5 mm, the width is 200-300 mm, and the length is 300-500 mm.
As an improvement of the manufacturing method of the overcurrent protection element with high weather resistance and reliability, in the sixth step, the material of the encapsulation layer is at least one of epoxy resin, polyamide resin, silicone rubber and inorganic rubber.
As an improvement of the manufacturing method of the high-weather-resistance reliable overcurrent protection element, the invention integrates the requirements of material density, material thickness, electron beam energy and irradiation dose, and the specific parameters in the electron beam irradiation treatment of the third step are defined as follows: the lamination is controlled to be 1-3 layers, the energy of an electron beam is 2-10 Mev, the electron beam current is selected to be 5-20 mA, the speed of a trolley is controlled to be 4-20 m/min, and the irradiation dose is 30-150 kGy (which can be realized by multiple times of irradiation). In the invention, according to the volume ratio, the conductive substance accounts for more than 3 times of the polymer powder; the density drop between the conductive substance and the polymer is large, and the conductive substance is easy to settle or overflow in the polymer due to gravity factor in the molten or expanded state of the high polymer material, so that the PTC positive temperature effect is weakened; the cross-linking property of the internal high molecular structure of the PPTC chip which is not subjected to electronic irradiation is unstable, so that the heat resistance and the aging resistance of the PPTC composite material are poor, the resistance change is unstable after a long time, the resistance change rate is high, the PPTC effect is poor, and the service life of the PPTC is greatly shortened; therefore, the PPTC chip can enhance the cross-linking of the macromolecular structure by carrying out electron irradiation, enhance the positive temperature effect of the PPTC, enhance the heat resistance and the ageing resistance, and ensure the service life and the safety of the PPTC. By reasonably controlling the lamination quantity, the electron beam energy control, the electron beam flow control and the irradiation trolley speed, the uniformity of the irradiation absorbed dose of the PPTC chip is finally achieved, and the heat resistance and the ageing resistance of the PPTC chip are improved.
In the prior art, the low-resistance thermistor can be used as a conductive substrate by optimizing the manufacturing process of the high-weather-resistance reliable overcurrent protection element, and the side surface of the low-resistance thermistor is coated with the moisture-proof insulating encapsulating layer, so that the high-weather-resistance overcurrent protection element has good moisture-proof capability and side surface insulating capability and stable weather resistance. And because the manufacturing method of the low-resistance thermistor is ingenious, the whole overcurrent protection element has the advantages of good consistency and stable and reliable performance. In addition, the element main body of the invention has double-sided welding surfaces, so that the front and the back of the element are not needed to be distinguished during processing and use, the processing and detection are convenient, the processing production efficiency is improved, and the installation cost is reduced.
Drawings
Fig. 1 is a schematic structural diagram of an overcurrent protection device in the prior art.
Fig. 2 is a schematic perspective view of embodiment 1 of the present invention.
Fig. 3 is a schematic cross-sectional structure diagram of embodiment 1 of the present invention.
Fig. 4 is an exploded view of an element body in example 1 of the present invention.
FIG. 5 is a schematic view of the structure of a twin-screw pelletizer used in the first step of the present invention.
FIG. 6 is a schematic view showing the structure of the apparatus used in the second step of the present invention.
Fig. 7 is a schematic cross-sectional view of embodiment 19 of the present invention.
Fig. 8 is an exploded view of an element body in example 19 of the present invention.
FIG. 9 shows the results of the test in which the products obtained in comparative example 11 and comparative example 12 and the products obtained in example 1 and example 19 were placed in a high-temperature and high-humidity environment of 85 ℃ and 85% RH, respectively, and maintained for 1000 hours.
Detailed Description
Example 1
As shown in fig. 2 to 4, the overcurrent protection element provided in this embodiment includes an element main body 20 having a first recess 18 and a second recess 19 at two ends thereof, respectively, and an encapsulating layer 25 disposed on a side surface of the element main body 20 except the first recess 18 and the second recess 19, where the element main body 20 includes a low-resistance thermistor 21, PP layers 22 disposed on upper and lower surfaces of the low-resistance thermistor 21, and a first electrode 23 and a second electrode 24 disposed on the PP layers 22, and a manufacturing method of the overcurrent protection element at least includes the following steps:
firstly, mixing a polymer and a conductive substance together in a double-screw granulator by adopting a double-screw granulation processing mode and granulating to form a mixture;
secondly, melting and extruding the mixture obtained in the first step by adopting a single-screw extrusion processing technology in a single-screw extrusion molding machine to form a PPTC sheet material 26, and forming the sheet material between an upper electrode copper foil and a lower electrode copper foil to form a PPTC chip;
thirdly, performing electron beam irradiation treatment on the PPTC chip formed in the second step;
fourthly, stamping the PPTC chip, forming a low-resistance thermistor 21 through a PCB processing technology, etching inner-layer circuits on the upper electrode copper foil 15 and the lower electrode copper foil 16, sequentially laying a PP layer 22 and an outer-layer copper foil on the upper surface of the upper electrode copper foil 15, sequentially laying the PP layer 22 and the outer-layer copper foil on the lower surface of the lower electrode copper foil 16, and performing vacuum lamination to enable the upper electrode copper foil 15, the PP layer 22 and the outer-layer copper foil to be tightly fused together, and tightly fusing the lower electrode copper foil 16, the PP layer 22 and the outer-layer copper foil together, wherein the PP layer 22 is an insulating material, effectively separates the upper electrode copper foil 15 from the outer-layer copper foil, and separates the lower electrode copper foil 16 from the outer-layer copper foil.
Fifthly, etching an outer layer circuit on the outer layer copper foil to enable the outer layer copper foil to form a first electrode 23 and a second electrode 24 at two ends of the PP layer 22 respectively, then forming a first groove 18 and a second groove 19 at two ends of the element main body 20 respectively by adopting a drilling process, and enabling the first groove 18 to connect the upper electrode copper foil 15 with the first electrode 23 and enabling the second groove 19 to connect the lower electrode copper foil 16 with the second electrode 24 through a treatment process of cleaning, removing glue, depositing copper and plating tin;
sixthly, sealing the four sides of the element main body 20 by adopting a sealing process, and then performing heat curing treatment, so that the low-resistance thermistor 21 exposed in the air is completely encapsulated, but the first groove 18 and the second groove 19 are well remained and are not encapsulated, and an encapsulating layer is formed. Finally, the high-reliability polymer overcurrent protection element which has a double-sided welding surface, is coated with the moisture-proof insulating encapsulating layer on the side surface, has excellent weather resistance and good moisture resistance, is insulated on the side surface and can prevent other elements and parts from being processed and assembled from touching the short circuit risk is prepared.
In the first step, the mass ratio of the polymer to the conductive substance is 7: 93, the polymer is polyethylene, the conductive substance is titanium carbide, and the particle size of the conductive substance is between 0.01 and 20 μm.
The structure of the twin-screw granulator used in the first step is shown in fig. 5, and comprises a main motor 1, 8 self-temperature-control heating material cylinders 2 which are combined into a gun barrel, wherein equidirectional twin screws are arranged in the gun barrel and connected with the main motor 1, the first material cylinder 2 is connected with the main motor 1, the second material cylinder 2 is provided with a feeding opening 3, the fourth material cylinder 2 is provided with an exhaust hole 4, the seventh material cylinder 2 is provided with a vacuum pumping opening 5, and the eighth material cylinder 2 is connected with a discharge die head 6.
The specific process of the twin-screw granulation processing in the first step comprises the following steps: after the polymer and the conductive substance are premixed, the polymer and the conductive substance are added into a second self-temperature-control heating material cylinder 2 from a feeding port 3, after the temperature of each temperature zone reaches, a main motor is started, the polymer and the conductive substance are uniformly mixed by double screws and then are extruded from a discharging die head 6 and granulated (a cutter is arranged on the discharging die head 6 and is cut into particles), a mixture is formed, and in the mixing process, moisture is discharged through an exhaust hole 4 and a vacuumizing port 5 which are arranged on the self-temperature-control heating material cylinder 2.
The temperature in the first self-temperature-control heating material cylinder 2 farthest from the discharging die head 6 is 120 ℃, the temperature from the second self-temperature-control heating material cylinder 2 to the eighth self-temperature-control heating material cylinder 2 is 250 ℃, and the temperature of the discharging die head 6 is 250 ℃; the vacuum degree of the vacuumizing port is less than 500 Psi; the twin screw was rotated at 10 rpm.
The equipment used in the second step is shown in fig. 6, and comprises a main motor 7 and 8 self-temperature-control heating high-wear-resistance material cylinders 8, wherein the first cylinder 8 is connected with the main motor 7, the second cylinder 8 is provided with a feeding area 14, the fourth cylinder 8 is provided with an exhaust hole 10, the seventh cylinder 8 is provided with a vacuum exhaust port 11, a high-wear-resistance single screw rod is arranged in the cylinder 8 and connected with the main motor 7, the eighth cylinder 8 is connected with a forming die head 9, and one side of the forming die head 9 is provided with an upper roller 12 and a lower roller 13;
in the second step, the melt extrusion process comprises the following specific steps: adding the mixture obtained in the first step into a self-temperature-control heating high-wear-resistance material cylinder 8 from a feeding area, starting a main motor 7 when the temperature of each temperature area is raised to a set temperature range, starting feeding and extruding, heating the mixture by a high-wear-resistance single screw rod, and extruding the mixture from a forming die head 9 to form a PPTC sheet material, wherein in the mixing process, moisture is discharged through an exhaust hole 10 and a vacuum exhaust hole 11 which are arranged on the self-temperature-control heating high-wear-resistance material cylinder 8;
the specific process for forming the sheet material 17 between the upper electrode copper foil 15 and the lower electrode copper foil 16 is as follows: an upper electrode copper foil 15 and a lower electrode copper foil 16 are respectively and automatically coated on the upper surface and the lower surface of a PPTC sheet material 17 through an upper roller 12 and a lower roller 13, so that a PPTC chip is formed.
The temperature in the first self-temperature-control heating high-wear-resistance material cylinder 8 farthest from the molding die head 9 is 120 ℃, the temperature from the second self-temperature-control heating high-wear-resistance material cylinder 8 to the eighth self-temperature-control heating high-wear-resistance material cylinder 8 is 270 ℃, and the temperature of the molding die head is 270 ℃; the vacuum degree of the vacuum exhaust port is less than 500 Psi; the temperature of the upper roller and the lower roller is 200 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.255 mm.
The specific parameters in the electron beam irradiation treatment in the third step are as follows: the lamination is controlled to be 1-3 layers, the energy of an electron beam is 2-10 Mev, the electron beam current is selected to be 5-20 mA, the speed of a trolley is controlled to be 4-20 m/min, and the irradiation dose is 30-150 kGy.
Processing the PPTC chip 21 obtained in the third step into a patch low-resistance thermistor (self-recovery fuse) with the chip size of 3.25mm, the width of 2.58mm and the thickness of 0.58mm by a PCB (printed circuit board); the resistance value of the low-resistance thermistor was measured and the consistency of the resistance values was confirmed, and the results are shown in Table 1.
Example 2
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 4: 96. the polymer is polyvinyl chloride, the conductive substance is vanadium carbide, and in the first-step double-screw granulation process, the temperature in a first self-temperature-control heating material cylinder farthest from a discharge die head is 115 ℃, the temperature from a second self-temperature-control heating material cylinder to an eighth self-temperature-control heating material cylinder is 240 ℃, and the temperature of the discharge die head is 240 ℃; the vacuum degree of the vacuumizing port is less than 500 Psi; the twin screw was rotated at 12 rpm. In the second step, in the specific process of melt extrusion, the temperature in the first self-temperature-control heating high-wear-resistance material barrel farthest from the forming die head is 115 ℃, the temperature from the second self-temperature-control heating high-wear-resistance material barrel to the eighth self-temperature-control heating high-wear-resistance material barrel is 260 ℃, and the temperature of the forming die head is 260 ℃; the vacuum degree of the vacuum exhaust port is less than 500 Psi; the temperature of the upper roller and the lower roller is 190 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.262 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm, the width of 2.58mm and the thickness of 0.60mm through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 5: 95. in the specific process of the first-step double-screw granulation processing, the temperature in a first self-temperature-control heating material cylinder farthest from a discharge die head is 125 ℃, the temperature from a second self-temperature-control heating material cylinder to an eighth self-temperature-control heating material cylinder is 260 ℃, and the temperature of the discharge die head is 260 ℃; the vacuum degree of the vacuumizing port is less than 500 Psi; the twin screw was rotated at 11 rpm. In the second step, in the specific process of melt extrusion, the temperature in the first self-temperature-control heating high-wear-resistance material cylinder farthest from the forming die head is 125 ℃, the temperature from the second self-temperature-control heating high-wear-resistance material cylinder to the eighth self-temperature-control heating high-wear-resistance material cylinder is 270 ℃, and the temperature of the forming die head is 270 ℃; the vacuum degree of the vacuum exhaust port is less than 500 Psi; the temperature of the upper roller and the lower roller is 195 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.264 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm, the width of 2.58mm and the thickness of 0.585mm through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 3: 97. in the specific process of the first-step double-screw granulation processing, the temperature in a first self-temperature-control heating material cylinder farthest from a discharge die head is 125 ℃, the temperature from a second self-temperature-control heating material cylinder to an eighth self-temperature-control heating material cylinder is 255 ℃, and the temperature of the discharge die head is 255 ℃; the vacuum degree of the vacuumizing port is less than 500 Psi; the twin screw was rotated at 9 rpm. In the second step, in the specific process of melt extrusion, the temperature in the first self-temperature-control heating high-wear-resistance material barrel farthest from the forming die head is 125 ℃, the temperature from the second self-temperature-control heating high-wear-resistance material barrel to the eighth self-temperature-control heating high-wear-resistance material barrel is 265 ℃, and the temperature of the forming die head is 265 ℃; the vacuum degree of the vacuum exhaust port is less than 500 Psi; the temperature of the upper roller and the lower roller is 205 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.268 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm, the width of 2.58mm and the thickness of 0.592mm through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 6: 94. the polymer is polycarbonate, the conductive substance is niobium carbide, and the temperature of the upper roller and the lower roller is 200 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.273 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm, the width of 2.58mm and the thickness of 0.612mm through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 8: 92. the polymer is polyvinyl fluoride, the conductive substance is molybdenum carbide, and the temperature of the upper roller and the lower roller is 200 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.261 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm in length, 2.58mm in width and 0.586mm in thickness through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 9: 91. the polymer is maleic anhydride grafted polyethylene, the conductive substance is titanium boride, and the temperature of the upper roller and the lower roller is 200 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.269 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm in length, 2.58mm in width and 0.604mm in thickness through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
Unlike example 1, in the first step, the mass ratio of the polymer to the conductive substance was 10: 90. the polymer is polypropylene, the conductive substance is titanium nitride, and the temperature of the upper roller and the lower roller is 200 ℃; the rotating speed of the roller is set to be 2-5 scales so as to form a PPTC chip with the thickness of 0.270 mm.
And processing the PPTC chip obtained in the third step into a patch low-resistance thermistor with the chip size of 3.25mm in length, 2.58mm in width and 0.608mm in thickness through a PCB.
The rest is the same as embodiment 1, and the description is omitted here.
Examples 9 to 18
Different from the embodiment 1, the thicknesses of the low-resistance thermistor of the patch are 0.601mm, 0.594mm, 0.598mm, 0.603mm, 0.591mm, 0.599mm, 0.588mm, 0.592mm and 0.595mm in sequence, and the rest is the same as the embodiment 1 and is not repeated.
Example 19
Unlike embodiment 1, as shown in fig. 7 and 8, the present embodiment provides an overcurrent protection element in which two low-resistance thermistors 21 are provided, and the two low-resistance thermistors 21 are connected in parallel. The arrangement of the two low-resistance thermistors 21 is to obtain a lower resistance value and a larger rated working current characteristic, the side surface area of the low-resistance thermistor exposed in the air can be increased due to the lamination of the multi-layer chip structure, and the protection of the encapsulating layer needs to be completed in place to ensure that the low-resistance thermistor has excellent weather resistance, environmental stability and good moisture resistance.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
The preparation method adopts the prior preparation process: firstly, polyethylene and titanium carbide are mixed according to the weight ratio of 7: 93, the particle size of the titanium carbide is between 0.01 and 20 microns, then the compound is pressed to form a PPTC (polymer PTC) chip, and finally the PPTC chip is punched and processed into a patch low-resistance thermistor with the chip size of 3.25mm, the width of 2.58mm and the thickness of 0.265mm through PCB (printed Circuit Board). The resistance value of the low-resistance thermistor of the chip is measured (self-recovery fuse), and the consistency of the resistance value is calculated, and the obtained result is shown in table 1.
Comparative examples 2 to 10
Unlike comparative example 1, the low-resistance thermistors of the patch were 0.605mm, 0.599mm, 0.588mm, 0.607mm, 0.592mm, 0.599mm, 0.601mm, 0.593mm, and 0.598mm in this order, and the rest was the same as in example 1 and thus, the description thereof is omitted. The resistance value of the low-resistance thermistor of the patch is calculated, and the resistance consistency is calculated, and the obtained result is shown in table 1.
Comparative example 11
Unlike embodiment 1, the low-resistance thermistor in the overcurrent protection element is a resistor manufactured by a manufacturing method in the prior art, and is not provided with an encapsulating layer.
Comparative example 12
Unlike in example 19, the low-resistance thermistor in the overcurrent protection element was a resistor manufactured by a manufacturing method in the related art, and was not provided with an encapsulating layer.
Table 1: test results of low resistance thermistors in examples 1, 9 to 18 and comparative examples 1 to 10.
As can be seen from table 1, the low-resistance thermistor of the chip manufactured by the manufacturing method of the present invention has good resistance distribution uniformity and can achieve lower resistance characteristics.
The products obtained in comparative examples 11 and 12 and the products obtained in example 1 and example 19 were placed in a high temperature and high humidity environment of 85 ℃ and 85% RH for 1000 hours, and the test results are shown in FIG. 9; the resistance values of examples 1 and 19 were not greatly varied, substantially within 10%; the resistance values of the comparative examples 11 and 12 are relatively large in variation, and the resistance value is increased by nearly 5 times; the invention has the advantages of excellent weather resistance, good moisture resistance and obvious environmental stability. In a word, the weather-proof reliability of the product is obviously improved.
Appropriate changes and modifications to the embodiments described above will become apparent to those skilled in the art from the disclosure and teachings of the foregoing description. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (9)
1. The manufacturing method of the over-current protection element with reliable weather resistance is characterized by comprising an element main body and an encapsulating layer, wherein a first groove and a second groove are respectively formed in two ends of the element main body, the encapsulating layer is arranged on the side face of the element main body except the first groove and the second groove, the element main body comprises a low-resistance thermistor, PP layers arranged on the upper surface and the lower surface of the low-resistance thermistor, and a first electrode and a second electrode which are arranged on the PP layers, and the manufacturing method at least comprises the following steps:
firstly, mixing a polymer and a conductive substance together in a double-screw granulator by adopting a double-screw granulation processing mode and granulating to form a mixture;
secondly, melting and extruding the mixture obtained in the first step by adopting a single-screw extrusion processing technology in a single-screw extrusion molding machine to form a PPTC sheet material, and forming the sheet material between an upper electrode copper foil and a lower electrode copper foil to form a PPTC chip;
thirdly, performing electron beam irradiation treatment on the PPTC chip formed in the second step;
fourthly, stamping the PPTC chip, forming a low-resistance thermistor through a PCB (printed Circuit Board) processing technology, etching inner-layer circuits on an upper electrode copper foil and a lower electrode copper foil, sequentially laying a PP (polypropylene) layer and an outer-layer copper foil on the upper surface of the upper electrode copper foil, sequentially laying the PP layer and the outer-layer copper foil on the lower surface of the lower electrode copper foil, and performing vacuum lamination;
fifthly, etching an outer layer circuit on the outer layer copper foil to enable the outer layer copper foil to form a first electrode and a second electrode at two ends of the PP layer respectively, then forming a first groove and a second groove at two ends of the element main body respectively by adopting a drilling process, and then connecting the upper electrode copper foil and the first electrode by the first groove and connecting the lower electrode copper foil and the second electrode by the second groove through a treatment process of cleaning, removing glue, depositing copper and plating tin;
and sixthly, sealing the four side surfaces of the element main body by adopting a sealing process, and then performing thermocuring treatment, so that the low-resistance thermistor exposed in the air is completely encapsulated to form an encapsulating layer, but the first groove and the second groove are well reserved and are not encapsulated.
2. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 1, comprising: in the first step, the mass ratio of the polymer to the conductive substance is (2-10): (90-98); in the first step, the polymer is at least one of polyethylene, polyvinyl chloride, chlorinated polyethylene butadiene-acrylonitrile copolymer, polytetrafluoroethylene, polycarbonate, polyvinyl fluoride, maleic anhydride grafted polyethylene and polypropylene; the conductive substance is at least one of titanium carbide, vanadium carbide, zirconium carbide, tungsten carbide, niobium carbide, molybdenum carbide, titanium boride, vanadium boride, zirconium boride, niobium boride and titanium nitride; the particle size of the conductive substance is between 0.01 and 20 μm.
3. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 1, comprising: the specific process of the twin-screw granulation processing in the first step comprises the following steps: the polymer and the conductive substance are premixed and then added into the self-temperature-control heating material cylinder from the feeding port, the polymer and the conductive substance are uniformly mixed by the double screws and then extruded out of the discharging die head to form a mixture, and moisture is discharged through an exhaust hole and a vacuumizing hole which are formed in the self-temperature-control heating material cylinder in the mixing process.
4. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 3, wherein: the number of the self-temperature-control heating material cylinders is eight, wherein the temperature in the first self-temperature-control heating material cylinder farthest from the discharge die head is 110-130 ℃, the temperature from the second self-temperature-control heating material cylinder to the eighth self-temperature-control heating material cylinder is 220-270 ℃, and the temperature of the discharge die head is 220-270 ℃; the vacuum degree of the vacuumizing port is less than 500 Psi; the rotating speed of the double screws is 8-15 rpm.
5. The method for manufacturing a weather-resistant reliable overcurrent protection element according to claim 3 or 4, characterized in that: in the second step, the melt extrusion process comprises the following specific steps: adding the mixture obtained in the first step into a self-temperature-control heating high-wear-resistance material cylinder from a feeding area, heating the mixture by a high-wear-resistance single screw rod, and extruding the mixture from a forming die head to form a PPTC sheet material, wherein moisture is discharged through an exhaust hole and a vacuum exhaust port which are arranged on the self-temperature-control heating high-wear-resistance material cylinder in the mixing process;
the specific process for forming the sheet material between the upper electrode copper foil and the lower electrode copper foil comprises the following steps: and automatically laminating an upper electrode copper foil and a lower electrode copper foil on the upper surface and the lower surface of the PPTC sheet material respectively through an upper roller and a lower roller so as to form the PPTC chip.
6. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 5, wherein: the number of the material barrels for self-temperature-control heating high-wear-resistance materials is eight, wherein the temperature in the first material barrel for self-temperature-control heating high-wear-resistance materials farthest away from the forming die head is 110-130 ℃, the temperature from the second material barrel for self-temperature-control heating high-wear-resistance materials to the eighth material barrel for self-temperature-control heating high-wear-resistance materials is 235-275 ℃, and the temperature of the forming die head is 235-275 ℃; the vacuum degree of the vacuum exhaust port is less than 500 Psi; the temperature of the upper roller and the lower roller is 180-220 ℃; the rotating speed of the roller is set to be between 2 and 5 scales.
7. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 1, comprising: the specific parameters in the electron beam irradiation treatment in the third step are as follows: the lamination is controlled to be 1-3 layers, the energy of an electron beam is 2-10 Mev, the electron beam current is selected to be 5-20 mA, the speed of a trolley is controlled to be 4-20 m/min, and the irradiation dose is 10-150 kGy.
8. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 1, comprising: and in the sixth step, the material of the encapsulating layer is at least one of epoxy resin, polyamide resin, silicon rubber and inorganic rubber.
9. The method for manufacturing a weather-resistant and reliable overcurrent protection element according to claim 1, comprising: the thickness of the PPTC chip is 0.18-2.5 mm, the width is 200-300 mm, and the length is 300-500 mm.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114300208A (en) * | 2021-12-24 | 2022-04-08 | 杭州光之神科技发展有限公司 | Preparation method of heat dissipation insulating protective layer of piezoresistor |
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