阅读说明：本技术 一种低阻高再现性ptc过电流保护元件 (Low-resistance high-reproducibility PTC (Positive temperature coefficient) overcurrent protection element ) 是由 高道华 夏坤 张锐 黄贺军 方勇 吴国臣 张伟 于 2021-08-20 设计创作，主要内容包括：本发明涉及一种低阻高再现性PTC过电流保护元件,具有可有效改善产品环境可靠性的功能,以高分子PTC复合片材为主的具有优异环境稳定性的低电阻表面贴装高分子PTC过电流保护元件,该保护元件的侧面,或保护元件侧面和一个正面具有涂覆层或镀层,使导电复合材料基层与外界环境隔离。本发明具有以下特点：1.元件的四个侧面的任意组合面包裹有包覆层,或镀层,一个正面可以包裹包覆层,也可以不包裹包覆层,使元件高分子PTC复合片材与环境隔离,从而提高了产品的电阻再现性；2.起电气连接作用的导电孔位于元件两侧,保证了元件具有良好的焊接性能3.具有不改变现有产品结构,可以完全采用目前的组装方式。(The invention relates to a low-resistance high-reproducibility PTC (positive temperature coefficient) overcurrent protection element, which has the function of effectively improving the environmental reliability of a product, wherein a high-molecular PTC composite sheet is mainly used, the low-resistance surface with excellent environmental stability is pasted with a high-molecular PTC overcurrent protection element, and the side surface of the protection element, or the side surface and the front surface of the protection element are provided with a coating layer or a plating layer, so that a conductive composite material base layer is isolated from the external environment. The invention has the following characteristics: 1. any combination surface of the four side surfaces of the element is coated with a coating layer or a plating layer, and one front surface can be coated with the coating layer or not coated with the coating layer, so that the element polymer PTC composite sheet is isolated from the environment, and the resistance reproducibility of the product is improved; 2. the conductive holes for electrical connection are located on both sides of the component, ensuring good welding performance of the component 3. the structure of the existing product is not changed, and the existing assembly mode can be completely adopted.)

1. A low-resistance high-reproducibility PTC over-current protection element has the function of effectively improving the environmental reliability of products, and adopts a surface-mounted PCT protection element with a surface packaging structure, and is characterized in that an encapsulating layer or a plating layer is added on the side surface of the over-current protection element or the side surface and the front surface of the over-current protection element, and the low-resistance high-reproducibility PTC over-current protection element comprises:

1) composite sheet material having at least one positive temperature coefficient of resistance effect, comprising:

(a) the conductive high molecular polymer composite material base layer with the resistance positive temperature coefficient effect consists of at least one polymer and at least one conductive filler which is dispersed in the polymer, has the volume resistivity of 0.1-100 m omega-cm and the particle size of 0.1-50 mu m, and is provided with a first surface and a second surface which are opposite;

(b) a first conductive electrode on a first surface of the conductive composite base layer;

(c) a second conductive electrode on a second surface of the conductive composite substrate;

2) the conductive holes are arranged on two sides of the element and comprise a first conductive hole and a second conductive hole,

the first conductive hole is electrically connected with one conductive electrode in each composite material sheet and is not electrically connected with the other corresponding conductive electrode;

a second conductive via which is not electrically connected to the conductive electrode in each composite material sheet which has been electrically connected to the first conductive via, and which is electrically connected to the conductive electrode in each composite material sheet which is not electrically connected to the first conductive via;

3) the first end electrode is positioned on two surfaces or the same surface of the outermost layer of the whole element, is connected with the first conductive hole, is used as a bonding pad, and is electrically connected with an external circuit one electrode after being welded into a circuit;

the second end electrode and the first end electrode are positioned on two surfaces or the same surface of the outermost layer of the whole element, are electrically isolated from the first end electrode, are connected with the second conductive hole, are used as a bonding pad and are welded into a circuit to electrically connect the element with the other electrode of an external circuit;

4) the insulating layer is attached between the first conductive electrode and the second conductive electrode on the non-identical composite material sheet, and between the conductive electrode on the outermost layer of the element and the terminal electrode, and is used for electrical isolation;

5) the side surface of the protective element, or the side surface and the front surface of the protective element are provided with a coating layer or a plating layer, so that the conductive composite material base layer is isolated from the external environment.

2. The low resistance, high reproducibility PTC overcurrent protection element according to claim 1, wherein the overcurrent protection element has a length of 5mm or less, a width of 4mm or less, and a thickness of 1.4mm or less.

3. A low resistance, high reproducibility PTC overcurrent protection element according to claim 1, wherein the coating is a nanoceramic coating, an alumina coating, a silica coating, or a metalloid oxide coating.

4. A low resistance high reproducibility PTC overcurrent protection element according to any one of claims 1 to 3,

an encapsulating layer or a plating layer is added on the side surface of the over-current protection element, so that the polymer PTC composite sheet is isolated from air, and the environmental reliability of the over-current protection element is improved;

the polymer PTC composite sheet consists of a first conductive electrode, a second conductive electrode and a polymer composite material base layer;

respectively etching an insulating groove on a first conductive electrode and a second conductive electrode by using a PCB (printed Circuit Board) etching processing technology for the polymer PTC composite sheet, then overlapping an upper insulating layer between the first conductive electrode and a metal foil, simultaneously overlapping a lower insulating layer between the second conductive electrode and another metal foil, forming a substrate after high-temperature lamination, forming an upper first end electrode, a lower first end electrode, an upper second end electrode, a lower second end electrode and an upper insulating groove and a lower insulating groove which are used for electrically isolating the first end electrode from the second end electrode outside the element by the steps of end electrode tinning, outer layer pattern etching, solder resist ink printing and the like for the substrate; after subsequent drilling, copper deposition and copper plating, a semicircular first conductive through hole for communicating the upper and lower first end electrodes with the second conductive electrode and a semicircular second conductive through hole for communicating the upper and lower second end electrodes with the first conductive electrode are formed; and then, wrapping four sides of the rectangular element with an encapsulation layer by adopting a side coating process to obtain the low-resistance high-reproducibility polymer PTC over-current protection element with two welding surfaces.

5. A low resistance high reproducibility PTC overcurrent protection element according to any one of claims 1 to 3,

the side and the front of the over-current protection element are both encapsulated with a plating layer, so that the polymer PTC composite sheet is isolated from air, and the environmental reliability of the over-current protection element is improved;

the polymer PTC composite sheet consists of a first conductive electrode, a second conductive electrode and a polymer composite material base layer;

respectively etching an insulating groove on a first conductive electrode and a second conductive electrode by using a PCB (printed Circuit Board) etching processing technology for the polymer PTC composite sheet, then overlapping an upper insulating layer on the first conductive electrode, simultaneously overlapping a lower insulating layer between the second conductive electrode and a lower metal foil, then forming a substrate after high-temperature lamination, forming a first end electrode and a second end electrode by the steps of end electrode tinning, outer layer pattern etching, solder resist ink printing and the like, and forming a semicircular first conductive hole for connecting the second conductive electrode and the first conductive end and a semicircular second conductive hole for connecting the first conductive electrode and the second conductive end by subsequent drilling, copper deposition and copper plating; and then, coating the encapsulation layers on one front surface and four side surfaces of the element by adopting a coating process to obtain the low-resistance high-reproducibility high-polymer PTC over-current protection element with one welding surface and high environmental reliability.

6. A low resistance high reproducibility PTC overcurrent protection element according to any one of claims 1 to 3,

an encapsulating layer is added on the side surface of the over-current protection element, so that the polymer PTC composite sheets connected in parallel are isolated from air, and the environmental reliability of the over-current protection element is improved;

the two polymer PTC composite sheets with the same structure are respectively provided with a first conductive electrode, a second conductive electrode and a polymer composite material base layer; wherein the content of the first and second substances,

the first layer of polymer PTC composite sheet is composed of a first polymer composite material base layer, and a first conductive electrode and a second conductive electrode attached to the upper surface and the lower surface of the first polymer composite material base layer; respectively etching the first conductive electrode and the second conductive electrode to form an insulating groove by the first layer of polymer PTC composite sheet through a PCB etching technology, and then overlapping the upper insulating layer between the first conductive electrode and the first metal foil;

the second layer of high molecular PTC composite sheet is composed of a first high molecular composite material base layer, and a first conductive electrode and a second conductive electrode attached to the upper surface and the lower surface of the first high molecular PTC composite sheet, the first conductive electrode and the second conductive electrode are respectively etched to form an insulating groove by the second layer of high molecular PTC composite sheet through a PCB etching technology, and then a lower insulating layer is overlapped between the second conductive electrode and a second metal foil;

an intermediate insulating layer is arranged between the second conductive electrode of the first layer of polymer PTC composite sheet and the first conductive electrode of the second layer of polymer PTC composite sheet;

then, forming a substrate after high-temperature pressing, wherein the substrate is subjected to end electrode tin plating, outer layer pattern etching and solder resist ink printing to form an upper end electrode, a lower end electrode, an upper end insulating groove, a lower end insulating groove and an insulating groove, wherein the upper end electrode, the lower end electrode, the upper end insulating groove and the lower end insulating groove are used for electrically isolating the first end electrode and the second end electrode outside the element; forming a semicircular first conductive hole for connecting the second conductive electrodes of the two polymer PTC composite sheets with the upper and lower first end electrodes and a semicircular second conductive hole for connecting the first conductive electrodes of the two polymer PTC composite sheets with the upper and lower second end electrodes through subsequent drilling, copper deposition and copper plating; and then, a side coating process is adopted to wrap four sides of the element with a packaging layer, so that the high-molecular PTC over-current protection element with two welding surfaces and high environmental reliability is prepared.

7. A low resistance high reproducibility PTC overcurrent protection element according to any one of claims 1 to 3, wherein an encapsulating layer or plating layer is added to the side and front surfaces of the overcurrent protection element to isolate the parallel polymer PTC composite sheets from air, thereby improving the environmental reliability of the overcurrent protection element;

the two polymer PTC composite sheets with the same structure are respectively provided with a first conductive electrode, a second conductive electrode and a polymer composite material base layer; wherein the content of the first and second substances,

the first layer of polymer PTC composite sheet is composed of a first polymer composite material base layer, and a first conductive electrode and a second conductive electrode attached to the upper surface and the lower surface of the first polymer PTC composite sheet, wherein the first conductive electrode and the second conductive electrode are respectively etched to form an insulating groove by a PCB etching technology, and then an upper insulating layer is superposed on the first conductive electrode;

the second layer of high molecular PTC composite sheet is composed of a first high molecular composite material base layer and a first conductive electrode and a second conductive electrode attached to the upper surface and the lower surface of the first high molecular PTC composite sheet, the first conductive electrode and the second conductive electrode are respectively etched to form an insulating groove by the second layer of high molecular PTC composite sheet through a PCB etching technology, and then a lower insulating layer is overlapped between the second conductive electrode and a metal foil;

an intermediate insulating layer is arranged between the second conductive electrode of the first layer of polymer PTC composite sheet and the first conductive electrode of the second layer of polymer PTC composite sheet; then, after high-temperature pressing, a substrate is formed, a first end electrode and a second end electrode are formed on the substrate through the steps of end electrode tin plating, outer layer pattern etching, solder resist ink printing and the like, and a semicircular first conductive hole for connecting the first end electrode and a second conductive electrode of the two polymer PTC composite sheets and a semicircular second conductive hole for connecting the second end electrode and the first conductive electrode of the two polymer PTC composite sheets are formed through subsequent drilling, copper deposition and copper plating; and then, a coating process is adopted to encapsulate layers on one front surface and four side surfaces of the element, so that the low-resistance high-reproducibility high-polymer PTC over-current protection element with one welding surface and high environmental reliability is obtained.

Technical Field

The invention relates to an electronic component taking a conductive high polymer composite material as a main material, in particular to a PTC (positive temperature coefficient) overcurrent protection element with low resistance and high reproducibility.

Background

The PTC material with positive temperature coefficient characteristic can maintain a lower resistance value at normal temperature and has the characteristic of sharp response to temperature change, namely, when overcurrent or overhigh temperature occurs in a circuit, the resistance of the PTC material can be instantly increased to a high resistance value, so that the circuit is in an open circuit state, and the purpose of protecting circuit elements is achieved. The polymer-based conductive composite material can be connected into a circuit as a material of a current sensing element. Overcurrent protection elements made of such materials have been widely used in electronic circuits.

In recent years, with the increasing power of smart devices, the requirements for PTC elements are also increasing, and PTC elements are required to have higher current, so that lower room temperature resistance products become the first choice for smart devices. At present, metal powder and metal carbide are generally adopted as conductive fillers for low-resistance products, and the metal powder and the metal carbide are exposed in the air for a long time and are easily oxidized or absorb moisture by the air, so that the abnormal lift and drag of a polymer PTC product are caused, and the use of intelligent equipment is influenced.

In the prior art, the material side of the surface-mounted component is exposed in the air, which causes the PTC product to be affected with damp after the component is placed in the air or used for a period of time, so that the resistance value is increased, and the service performance of the PTC product is seriously affected.

Disclosure of Invention

The invention aims to provide a low-resistance high-polymer PTC overcurrent protection element which can effectively increase the environmental reliability of a product, so that a PTC composite sheet is isolated from air, and the environmental reliability of the product is greatly improved.

The present invention is directed to a PTC overcurrent protection device that can effectively solve the above-mentioned problems by adding an encapsulating layer or a plating layer to the side and front surfaces of the overcurrent protection device to improve the environmental reliability of the overcurrent protection device.

A low resistance high reproducibility PTC over-current protection device having a function of effectively improving reliability of a product environment, wherein an encapsulating layer or a plating layer is added to a side surface of the over-current protection device, or a side surface and a front surface of the over-current protection device, comprising:

1) composite sheet material having at least one positive temperature coefficient of resistance effect, comprising:

(a) the conductive high molecular polymer composite material base layer with the resistance positive temperature coefficient effect consists of at least one polymer and at least one conductive filler which is dispersed in the polymer, has the volume resistivity of 0.1-100 m omega-cm and the particle size of 0.1-50 mu m, and is provided with a first surface and a second surface which are opposite;

(b) a first conductive electrode on a first surface of the conductive composite base layer;

(c) a second conductive electrode on a second surface of the conductive composite substrate;

2) the conductive holes are arranged on two sides of the element and comprise a first conductive hole and a second conductive hole,

the first conductive hole is electrically connected with one conductive electrode in each composite material sheet and is not electrically connected with the other corresponding conductive electrode;

a second conductive via which is not electrically connected to the conductive electrode in each composite material sheet which has been electrically connected to the first conductive via, and which is electrically connected to the conductive electrode in each composite material sheet which is not electrically connected to the first conductive via;

3) the first end electrode is positioned on two surfaces or the same surface of the outermost layer of the whole element, is connected with the first conductive hole, is used as a bonding pad, and is electrically connected with an external circuit one electrode after being welded into a circuit;

the second end electrode and the first end electrode are positioned on two surfaces or the same surface of the outermost layer of the whole element, are electrically isolated from the first end electrode, are connected with the second conductive hole, are used as a bonding pad and are welded into a circuit to electrically connect the element with the other electrode of an external circuit;

4) the insulating layer is attached between the first conductive electrode and the second conductive electrode on the non-identical composite material sheet, and between the conductive electrode on the outermost layer of the element and the terminal electrode, and is used for electrical isolation;

5) the side surface of the protective element, or the side surface and the front surface of the protective element are provided with a coating layer or a plating layer, so that the conductive composite material base layer is isolated from the external environment.

The invention has the structural characteristics that:

1. the side surface of the protection element, or the side surface and one front surface of the protection element are provided with an encapsulating layer or a plating layer, so that the high polymer material substrate of the element is isolated from the air environment, and the element has higher environmental reliability;

2. the conductive holes which play a role in electrical connection are positioned on the two sides of the element, so that the element is fully ensured to have good welding operability, and the element has good environmental performance;

3. the invention can normally produce single-layer PTC chip products, double-layer PTC chips or multilayer PTC chip products, and the products of the proposal have two structures of single welding surface and double welding surfaces. Thereby the element has better welding performance. The conductive holes are formed by processes such as laser drilling, mechanical drilling and the like, and the surfaces of the holes are adhered with conductive metal layers, and the shapes of the conductive holes can be any regular or irregular shapes.

On the basis of the scheme, the side coating is a nano ceramic coating, an aluminum oxide coating and silicon oxide

A metal oxide plating layer such as a plating layer or a non-metal oxide plating layer.

The polymer accounts for 10-85% of the volume fraction of the conductive composite material base layer, and is selected from one of polyethylene, polyvinyl chloride, polystyrene, polycarbonate, polyvinyl fluoride, maleic anhydride grafted polyethylene, polypropylene, polyvinylidene fluoride, ethylene-vinyl acetate copolymer, polymethyl methacrylate, ethylene-acrylic acid copolymer and a mixture thereof.

The conductive filler is selected from one of metal powder or conductive ceramic powder and a mixture thereof.

The conductive ceramic powder is selected from: one or more of metal nitride, metal carbide, metal boride and metal silicide.

The technical scheme adopted by the invention for realizing the purpose is as follows: the method comprises the steps of forming a composite sheet by a polymer composite material base layer and a first conductive electrode and a second conductive electrode which are tightly attached to two sides of the polymer material base layer, etching an insulating groove on the conductive electrode of the composite sheet by an inner layer pattern transfer etching technology, then stacking two insulating layers on two surfaces of the etched composite sheet, respectively covering metal foils, carrying out high-temperature lamination, and then carrying out subsequent steps of tinning an outer layer metal foil, etching an outer layer pattern, printing solder resist ink, curing solder resist ink, drilling, copper deposition, copper plating and the like on a laminated substrate and a subsequent packaging process on the side surface or the front surface and the side surface of an element to obtain the polymer PTC overcurrent protection element with excellent environmental stability.

In the process of manufacturing the circuit board, the invention adopts a side coating process or a plating process to add an encapsulating layer or a plating layer on the side of the overcurrent protection element lamination layer, so that the element high polymer material base layer is isolated from the air environment, and the environment reliability of the product is improved.

Drawings

FIG. 1 is a schematic perspective view of an embodiment 1 of the present invention;

FIG. 2: the cross section of the single-layer sheet in the embodiment 1 of the invention is shown schematically;

FIG. 3: embodiment 2 of the invention is a whole three-dimensional schematic diagram;

FIG. 4: embodiment 2 of the invention a single-layer sheet profile schematic;

FIG. 5: embodiment 3 of the invention a double-layer sheet profile diagram;

FIG. 6: embodiment 4 of the invention a double-layer sheet profile diagram;

FIG. 7: the relationship graph of the resistance of the embodiment 1 of the invention and the existing product in the high-temperature and high-humidity environment along with the change of the placing time;

description of the figures

1. 1 a-upper and lower first terminal electrodes;

2. 2 a-upper and lower second terminal electrodes;

3. 3a, 3 b-upper, lower, middle insulation layers;

4. 4 a-first conductive electrode;

5. 5 a-macromolecule conductive composite material base layer;

6. 6 a-second conductive electrode;

7-first conductive via;

8-second conductive via;

9-outer envelope layer of the element;

10. 10 a-upper and lower insulation slots.

Detailed Description

Preparing a polymer PTC composite sheet:

the conductive high molecular polymer composite material base layer with resistance positive temperature coefficient effect is prepared from high-density polyethylene and a polymer dispersed in the high-density polyethylene, wherein the volume resistivity of the polymer is 0.1-100 m omega-cm, and the particle size of the polymer is as follows:

0.1-50 μm conductive filler metal tungsten carbide, mixing the two in a high-speed mixer for 30min, granulating the mixture in a double-screw granulator at 180 ℃, cooling, crushing, extruding by a single-screw extruder, rolling, attaching electrode foils on the upper and lower surfaces of a polymer sheet, and pressing to form the conductive filler metal tungsten carbide with the area of 400cm²A polymer composite substrate 5 with a thickness of 0.3mm, heat-treating in a vacuum oven at 120 deg.C for 0.5 hr, and irradiating with gamma ray (Co)⁶⁰) Irradiating with a dose of 16 Mrad; then, a polymer PTC composite sheet was obtained.

Example 1

A low-resistance polymer PTC over-current protection element capable of effectively increasing the environmental reliability of a product is manufactured into a surface-mounted polymer PTC over-current protection element by adopting a printed circuit board process, and comprises a polymer PTC composite sheet, a terminal electrode, a conductive electrode, an insulating layer and a conductive through hole, wherein,

an encapsulating layer or a plating layer is added on the side surface of the over-current protection element, so that the polymer PTC composite sheet is isolated from air, and the environmental reliability of the over-current protection element is improved;

a polymer PTC composite sheet, which is composed of a first conductive electrode 4, a second conductive electrode 6 and a polymer composite material base layer 5;

etching insulation grooves on a first conductive electrode 4 and a second conductive electrode 6 respectively by using a high polymer PTC composite sheet through a PCB etching processing technology, then overlapping an upper insulation layer 3 between the first conductive electrode 4 and a metal foil, simultaneously overlapping a lower insulation layer 3a between the second conductive electrode 6 and another metal foil, forming a substrate after high-temperature lamination, forming an upper first end electrode 1, a lower first end electrode 1, an upper second end electrode 2, a lower second end electrode 2a and upper insulation grooves 10, 10a for electrically isolating the first end electrode 1, 1a and the second end electrode 2, 2a from the outside of the element through the steps of end electrode tinning, outer layer pattern etching, solder resist ink printing and the like; after subsequent drilling, copper deposition and copper plating, a semicircular first conductive through hole 7 which is communicated with the upper and lower first end electrodes 1 and 1a and the second conductive electrode 6 and a semicircular second conductive through hole 8 which is communicated with the upper and lower second end electrodes 2 and 2a and the first conductive electrode 4 are formed; and then, a side coating process is adopted to wrap four sides of the rectangular element with a sealing layer 9, so that the high-molecular PTC over-current protection element with two welding surfaces and high environmental reliability is prepared. As shown in fig. 1 and 2.

FIG. 7: the invention shows the outstanding stability of the high-temperature high-humidity environment compared with the existing product in the relationship graph of the resistance change along with the storage time in the high-temperature high-humidity environment.

Example 2

A low-resistance polymer PTC over-current protection element capable of effectively increasing the environmental reliability of a product is prepared by adopting a printed circuit board process to prepare a surface-mounted polymer PTC over-current protection element, which is similar to the embodiment 1,

the side and the front of the over-current protection element are added with an encapsulating layer or a plating layer, so that the polymer PTC composite sheet is isolated from air, and the environmental reliability of the over-current protection element is improved;

a polymer PTC composite sheet, which is composed of a first conductive electrode 4, a second conductive electrode 6 and a polymer composite material base layer 5;

etching an insulating groove on a first conductive electrode 4 and a second conductive electrode 6 respectively by using a high polymer PTC composite sheet material through a PCB etching processing technology, then overlapping an upper insulating layer 3 on the first conductive electrode 4, meanwhile, overlapping a lower insulating layer 3a between the second conductive electrode 6 and a lower metal foil, then forming a substrate after high-temperature lamination, forming a first end electrode 1 and a second end electrode 2 by the steps of end electrode tinning, outer layer pattern etching, solder resist ink printing and the like, forming a semicircular first conductive hole 7 for connecting the second conductive electrode 6 and the first conductive end 1 through subsequent drilling, copper deposition and copper plating, and forming a semicircular second conductive hole 8 for connecting the first conductive electrode 4 and the second conductive end 2; and then, a coating process is adopted to wrap the encapsulation layer 9 on one front surface and four side surfaces of the element, so that the high-molecular PTC over-current protection element with one welding surface and high environmental reliability is prepared. As shown in fig. 3 and 4.

Example 3

A low-resistance polymer PTC over-current protection element capable of effectively increasing the environmental reliability of a product, as shown in FIG. 5, a surface-mounted polymer PTC over-current protection element is manufactured by a printed circuit board process, which is similar to that of example 1 except that two layers of polymer PTC composite sheets are connected in parallel to further reduce the initial resistance, an intermediate insulating layer 3b is arranged between the two polymer PTC composite sheets, wherein,

an encapsulating layer or a plating layer is added on the side surface of the over-current protection element, so that the polymer PTC composite sheets connected in parallel are isolated from air, and the environmental reliability of the over-current protection element is improved;

two polymer PTC composite sheets with the same structure are respectively provided with a first conductive electrode 4, 4a, a second conductive electrode 6, 6a and a polymer composite material base layer 5, 5 a; wherein the content of the first and second substances,

the first layer of polymer PTC composite sheet is composed of a first polymer composite material base layer 5, and a first conductive electrode 4 and a second conductive electrode 6 attached to the upper surface and the lower surface of the first polymer composite material base layer; the first layer of polymer PTC composite sheet is etched into an insulating groove by a first conductive electrode 4 and a second conductive electrode 6 respectively through a PCB etching technology, and then an upper insulating layer 3 is superposed between the first conductive electrode 4 and a first metal foil;

the second layer of high molecular PTC composite sheet is composed of a first high molecular composite material base layer 5a, and a first conductive electrode 4a and a second conductive electrode 6a attached to the upper surface and the lower surface of the first high molecular PTC composite sheet, the first conductive electrode 4a and the second conductive electrode 6a are respectively etched to form an insulating groove by the second layer of high molecular PTC composite sheet through a PCB etching technology, and then the lower insulating layer 3a is overlapped between the second conductive electrode 6a and a second metal foil;

an intermediate insulating layer 3b is arranged between the second conductive electrode 6 of the first layer of polymer PTC composite sheet and the first conductive electrode 4a of the second layer of polymer PTC composite sheet;

then, forming a substrate after high-temperature pressing, wherein the substrate is subjected to the steps of terminal electrode tin plating, outer layer pattern etching, solder resist ink printing and the like to form an upper first terminal electrode 1, a lower first terminal electrode 1a, an upper second terminal electrode 2, a lower second terminal electrode 2a, an upper insulating groove 10, a lower insulating groove 10a and an insulating groove 10a, wherein the upper insulating groove and the lower insulating groove are used for electrically isolating the first terminal electrode and the second terminal electrode outside the element; after subsequent drilling, copper deposition and copper plating, second conductive electrodes 6 and 6a connected with the two polymer PTC composite sheets, semicircular first conductive holes 7 of the upper and lower first end electrodes 1 and 1a, and semicircular second conductive holes 8 connected with the first conductive electrodes 4 and 4a of the two polymer PTC composite sheets, the upper and lower second end electrodes 2 and 2a are formed; and then, a side coating process is adopted to wrap four sides of the element with a sealing layer 9, so that the high-molecular PTC over-current protection element with two welding surfaces and high environmental reliability is prepared. As shown in fig. 5.

In the embodiment, a plurality of layers of composite sheets can be connected in parallel and realized by adopting the same conduction mode, so that the aim of reducing the internal resistance of the product is fulfilled. The side surface is also wrapped with a sealing layer 9, so that the high-molecular PTC over-current protection element with two welding surfaces and high environmental reliability is prepared.

Example 4

A low-resistance polymer PTC over-current protection element capable of effectively increasing the environmental reliability of a product, as shown in FIG. 6, a surface-mounted polymer PTC over-current protection element is manufactured by a printed circuit board process, similar to that of example 2, except that two layers of polymer PTC composite sheets are connected in parallel to further reduce the initial resistance, an intermediate insulating layer 3b is arranged between the two polymer PTC composite sheets, wherein,

the side and the front of the over-current protection element are added with an encapsulating layer or a plating layer, so that the polymer PTC composite sheets connected in parallel are isolated from air, and the environmental reliability of the over-current protection element is improved;

two polymer PTC composite sheets with the same structure are respectively provided with a first conductive electrode 4, 4a, a second conductive electrode 6, 6a and a polymer composite material base layer 5, 5 a; wherein the content of the first and second substances,

the first layer of polymer PTC composite sheet is composed of a first polymer composite material base layer 5, and a first conductive electrode 4 and a second conductive electrode 6 attached to the upper surface and the lower surface of the first polymer composite material base layer, wherein the first conductive electrode 4 and the second conductive electrode 6 are respectively etched to form an insulating groove by the first layer of polymer PTC composite sheet through a PCB etching technology, and then an upper insulating layer 3 is superposed on the first conductive electrode 4;

the second layer of high molecular PTC composite sheet is composed of a first high molecular composite material base layer 5a and a first conductive electrode 4a and a second conductive electrode 6a attached to the upper surface and the lower surface of the first high molecular PTC composite sheet, the first conductive electrode 4a and the second conductive electrode 6a are respectively etched to form an insulating groove by the second layer of high molecular PTC composite sheet through a PCB etching technology, and then the lower insulating layer 3a is overlapped between the second conductive electrode 6a and a metal foil;

an intermediate insulating layer 3b is arranged between the second conductive electrode 6 of the first layer of polymer PTC composite sheet and the first conductive electrode 4a of the second layer of polymer PTC composite sheet;

then, forming a substrate after high-temperature pressing, wherein the substrate is subjected to the steps of terminal electrode tin plating, outer layer pattern etching, solder resist ink printing and the like to form a first terminal electrode 1 and a second terminal electrode 2, and then drilling, copper deposition and copper plating are carried out to form a semicircular first conductive hole 7 for connecting the first terminal electrode 1 and second conductive electrodes 6 and 6a of the two polymer PTC composite sheets and a semicircular second conductive hole 8 for connecting the second terminal electrode 2 and the first conductive electrodes 4 and 4a of the two polymer PTC composite sheets; and then, a coating process is adopted to wrap the encapsulation layer 9 on one front surface and four side surfaces of the element, so that the high-molecular PTC over-current protection element with one welding surface and high environmental reliability is prepared. As shown in fig. 6.

In the embodiment, a plurality of layers of composite sheets can be connected in parallel and realized by adopting the same conduction mode, so that the aim of reducing the internal resistance of the product is fulfilled.

After the prepared overcurrent protection element is placed in a long-term environment, compared with a comparative example without side surface encapsulation, in a high-temperature and high-humidity environment, the resistance of the overcurrent protection element is almost a horizontal straight line along with the change of the placing time, and the environmental stability is obviously improved, as shown in figure 7.

While the technical content and the technical features of the invention have been disclosed, those skilled in the art can make various substitutions and modifications based on the teaching and the disclosure of the invention without departing from the spirit of the invention. Accordingly, the scope of the present invention should not be limited to the embodiments disclosed, but should include various alternatives and modifications without departing from the invention, which are encompassed by the following claims.