Overcurrent protection element

Abstract

The present application relates to the technical field of electronic components, and in particular to an overcurrent protection component, which overcomes the problems of poor conductivity, slow response and poor self-protection when used by welding of the prior art. The component has a core material, which comprises a top surface, a bottom surface opposite to the top surface, two side surfaces between the top surface and the bottom surface, and two end surfaces; a first conductive layer is formed on the top surface of the core material, and a second conductive layer is formed on the bottom surface of the core material; an encapsulation layer encapsulates the first conductive layer and the second conductive layer, and encapsulates at least one of the side surfaces; a first end electrode is electrically connected to the first conductive layer, and a second end electrode is electrically connected to the second conductive layer.

Description

Technical Field

[0001] This invention relates to the field of electronic components technology, and in particular to an overcurrent protection element. Background Technology

[0002] A thermistor is a temperature-sensitive protective component. It can generally be divided into positive temperature coefficient thermistors (PTC) and negative temperature coefficient thermistors (NTC). Its characteristic is that it exhibits different resistance values ​​at different temperatures. Thermistors are generally connected in series in the circuit. Using thermistors can effectively suppress the surge current at startup, and after suppressing the surge current, the continuous action of the current is used to ensure that electronic equipment is protected from damage. This is the simplest and most effective measure.

[0003] PPTC (Polymeric Positive Temperature Coefficient) is an abbreviation for a polymer positive coefficient temperature resistance resistor. In the domestic electronic overcurrent and overvoltage protection industry, PPTC is commonly referred to as a resettable fuse. The device has soldered electrodes at both ends, and the middle is a PPTC composite material formed by polymer and conductive filler. A single PPTC is cut from a large sheet of material. This manufacturing process determines that existing PPTCs have some performance defects, which are explained below using two publicly available prior art documents:

[0004] Chinese Patent Publication No. CN2470923Y, published on January 9, 2002, discloses a surface-mount electrical device, which ultimately requires a layered structure (the form of the layered structure is shown in the appendix of this document). Figure 1 The two ends of a single device form an electrical connection structure, so through holes need to be drilled on the large plate material beforehand at the corresponding cut ends (the drilling locations are shown in the appendix of the literature). Figure 2 A) After drilling, the through-hole portion is metallized to form a top-to-bottom conductive structure (the conductive state is still shown in the appendix of this document). Figure 2 A) After the cutting, the length of the half-hole arc is less than 50% of the total length on the end face. This results in the electrode and the middle thin plate resistor element only achieving a small area of ​​conduction, which reduces the conductivity and heat conduction of the element and prolongs the overcurrent protection response time. In addition, the thin plate resistor element exposed on the end face of the element is easily corroded by solvents such as flux and board cleaner when the element is soldered onto the circuit board.

[0005] To address the aforementioned deficiencies, another technical document offers an improvement. Chinese Patent Publication No. CN105976954A, published on September 28, 2016, discloses an overcurrent protection element. This element eliminates the need for drilling and, after slitting, coats the end faces with a conductive mixture, thus forming a first electrical connector and a second electrical connector at both ends. See the appendix of this document. Figure 1 The upper and lower planes of the component, excluding the electrodes, are covered with a solder resist insulating layer, which is formed before slitting. Left and right polymer coating layers are also formed on both sides of the component (see appendix of this document). Figure 4 However, this structure still has some defects: First, the electrical connectors are made of a conductive composite material, which has poor conductivity. Second, there are seams between the electrical connectors and the electrodes and PPTC composite material. The reliability of the electrical connection is poor due to thermal expansion and contraction during manufacturing and use. Moreover, the electrical connectors are applied later, which further exacerbates this defect. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide an overcurrent protection element that overcomes the problems of poor conductivity, slow response, and poor self-protection when used in welding of such elements.

[0007] The technical solution adopted by the present invention to solve its technical problem is: an overcurrent protection element having a core material, the core material comprising a top surface, a bottom surface opposite to the top surface, two side surfaces located between the top surface and the bottom surface, and two end surfaces;

[0008] A first conductive layer is formed on the top surface of the core material, and a second conductive layer is formed on the bottom surface of the core material;

[0009] An encapsulation layer covers the first conductive layer and the second conductive layer, and encapsulates at least one of the said sides;

[0010] A first terminal electrode is electrically connected to the first conductive layer, and a second terminal electrode is electrically connected to the second conductive layer.

[0011] A preferred encapsulation structure is that the encapsulation layer is a continuous structure and annularly encapsulates the first conductive layer, the second conductive layer, a first side surface, and a second side surface.

[0012] The encapsulation layer can be another structure, which includes a first encapsulation layer, a second encapsulation layer, a third encapsulation layer and a fourth encapsulation layer, respectively covering the first conductive layer, the second conductive layer, the first side surface and the second side surface, and having joints between the first encapsulation layer, the second encapsulation layer, the third encapsulation layer and the fourth encapsulation layer.

[0013] The encapsulation layer can also have another structure, which includes a first encapsulation layer, a second encapsulation layer, a third encapsulation layer and a fourth encapsulation layer, respectively covering the first conductive layer, the second conductive layer, the first side surface and the second side surface, and the first encapsulation layer, the third encapsulation layer and the fourth encapsulation layer are continuous structures, and the second encapsulation layer has a joint with the third encapsulation layer and the fourth encapsulation layer.

[0014] The encapsulation layer can also have another structure, which includes a first encapsulation layer, a second encapsulation layer, a third encapsulation layer and a fourth encapsulation layer, respectively covering the first conductive layer, the second conductive layer, the first side surface and the second side surface, and the second encapsulation layer is a continuous structure with the third encapsulation layer and the fourth encapsulation layer, and the first encapsulation layer has a joint with the third encapsulation layer and the fourth encapsulation layer.

[0015] Specifically, the first conductive layer and the second conductive layer comprise metal foil, metal coating, or metal plating.

[0016] Furthermore, the first conductive layer and the second conductive layer comprise copper foil, nickel foil, nickel-plated copper foil, tin-plated copper foil, or nickel-plated stainless steel.

[0017] Specifically, the core material is partially exposed after the first conductive layer and the second conductive layer are patterned and hollowed out.

[0018] Specifically, the first conductive layer and the second conductive layer include a break portion, wherein one break portion is 0-10 mm away from the first end face and the other break portion is 0-10 mm away from the second end face.

[0019] Specifically, a first insulating sheet is formed on the first conductive layer, and a second insulating sheet is formed on the second conductive layer.

[0020] Specifically, in order to increase the adhesion and conductivity of the electrodes on the component, a third conductive layer is formed on the surface of the first insulating sheet and extends between the first end electrode and the first end face and continues to extend to the surface of the second insulating sheet; a fourth conductive layer is formed on the surface of the second insulating sheet and extends between the second end electrode and the second end face and continues to extend to the surface of the first insulating sheet.

[0021] Specifically, the first end electrode and the second end electrode are "L" shaped and extend from the first and second end faces to a portion of the bottom surface, respectively.

[0022] Specifically, the first end electrode and the second end electrode are U-shaped and extend from the first and second end faces to a portion of the top surface and a portion of the bottom surface, respectively.

[0023] Specifically, the first terminal electrode and the second terminal electrode are any one of a copper layer, a nickel layer, or a tin layer, or any combination of two or three of them.

[0024] Specifically, the encapsulation layer comprises any one or any combination of two or more of the following: polyimide, prepreg, solder resist ink, silicone resin, fluoropolymer, epoxy resin, or polyolefin.

[0025] Specifically, the first insulating sheet and the second insulating sheet comprise any one or any combination of two or more of the following: polyimide, prepreg, solder resist ink, silicone resin, fluorinated resin, epoxy resin, or polyolefin.

[0026] Specifically, the core material includes an upper core material and a lower core material that are combined.

[0027] The beneficial effects of this invention are:

[0028] 1. The end electrode is a wrapped electrode, which can be further used as an electroplating electrode, printing electrode, spraying electrode, vapor deposition electrode or magnetron sputtering electrode. The electrode has good conductivity and responds quickly when in use.

[0029] 2. The encapsulation layer forms partial or complete encapsulation except for the terminal electrodes. The encapsulation layer can resist static electricity and prevent moisture from penetrating into the component and affecting the component's reliability. In addition, when the component is assembled on the circuit board, it can resist the corrosion of chemical solvents such as flux and board cleaning solvents.

[0030] Third, the increased solderable area when components are mounted on the circuit board improves both soldering performance and electrical connection. It also enhances electrical and thermal conductivity, further accelerating the response time of overcurrent protection components. Attached Figure Description

[0031] Figure 1 This is a perspective view of the present invention;

[0032] Figure 2 This is a cross-sectional view of the present invention;

[0033] Figure 3 yes Figure 2 The first structural diagram at the AA section;

[0034] Figure 4 yes Figure 2 The second structural diagram at the AA section;

[0035] Figure 5 yes Figure 2 The third structural diagram at the AA section;

[0036] Figure 6 yes Figure 2 The fourth structural diagram at the AA section;

[0037] Figure 7 yes Figure 2 BB section view;

[0038] Figure 8 Therefore Figure 6 Example: A schematic diagram of the overlapping structure is shown;

[0039] Figure 9This is a schematic diagram of the structure of the present invention having a third and fourth conductive layer;

[0040] Figure 10 This is a schematic diagram of the L-shaped terminal electrode structure of the present invention;

[0041] Figure 11 This is a schematic diagram of the core material having a composite structure in this invention.

[0042] In the figure: 1. Core material, 2. First conductive layer, 3. Second conductive layer, 4. Encapsulation layer, 4-1. First encapsulation layer, 4-2. Second encapsulation layer, 4-3. Third encapsulation layer, 4-4. Fourth encapsulation layer, 5. First end electrode, 6. Second end electrode, 7. First insulating sheet, 8. Second insulating sheet, 9. Third conductive layer, 10. Fourth conductive layer. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the invention in a schematic manner, and therefore only show the components relevant to the invention.

[0044] An overcurrent protection element, with the external shape shown in the attached figure. Figure 1 As shown in the following description, the length direction refers to both ends, the width direction refers to both sides, and the thickness direction refers to the top and bottom. The internal structural forms are as shown in the attached figure. Figures 2 to 11 As shown, a core material 1 is provided. The core material 1 includes a top surface, a bottom surface opposite the top surface, two side surfaces located between the top and bottom surfaces, and two end surfaces. The core material 1 is a rectangular body. The core material 1 is composed of a polymer substrate and a conductive material dispersed in the polymer substrate. Specifically, the polymer substrate is one or a mixture of more than one of the following: polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polytrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, chlorinated polyethylene, oxidized polyethylene, polyvinyl chloride, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polystyrene, polycarbonate, polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, polyoxymethylene, phenolic resin, maleic anhydride-grafted polyethylene, polypropylene, polyvinylidene fluoride, epoxy resin, ethylene-vinyl acetate copolymer, polymethyl methacrylate, and ethylene-acrylic acid copolymer. The conductive material is one or a mixture of more than one of the following: carbon black, metal carbide, and metal.

[0045] As attached Figure 2 A first conductive layer 2 is formed on the top surface of the core material 1 and extends to the first end face; a second conductive layer 3 is formed on the bottom surface of the core material 1 and extends to the second end face; the two conductive layers may not extend to each end face.

[0046] An encapsulation layer 4 covers the first conductive layer 2 and the second conductive layer 3, and encapsulates at least one side. The encapsulation structure of the encapsulation layer 4 has four types, namely:

[0047] Figure 3 The first structure shown is that the encapsulation layer 4 is a continuous structure and annularly encapsulates the first conductive layer 2, the second conductive layer 3, a first side surface, and a second side surface.

[0048] Figure 4 The second structure shown is that the encapsulation layer 4 includes a first encapsulation layer 4-1, a second encapsulation layer 4-2, a third encapsulation layer 4-3, and a fourth encapsulation layer 4-4, which respectively cover the first conductive layer 2, the second conductive layer 3, the first side surface, and the second side surface, and there are joints between the first encapsulation layer 4-1, the second encapsulation layer 4-2, the third encapsulation layer 4-3, and the fourth encapsulation layer 4-4;

[0049] Figure 5 The third structure shown is that the encapsulation layer 4 includes a first encapsulation layer 4-1, a second encapsulation layer 4-2, a third encapsulation layer 4-3, and a fourth encapsulation layer 4-4, which respectively cover the first conductive layer 2, the second conductive layer 3, the first side surface, and the second side surface. The first encapsulation layer 4-1, the third encapsulation layer 4-3, and the fourth encapsulation layer 4-4 are continuous structures, and the second encapsulation layer 4-2, the third encapsulation layer 4-3, and the fourth encapsulation layer 4-4 have joints.

[0050] Figure 6 The fourth structure shown is that the encapsulation layer 4 includes a first encapsulation layer 4-1, a second encapsulation layer 4-2, a third encapsulation layer 4-3, and a fourth encapsulation layer 4-4, which respectively cover the first conductive layer 2, the second conductive layer 3, the first side surface, and the second side surface. The second encapsulation layer 4-2, the third encapsulation layer 4-3, and the fourth encapsulation layer 4-4 are continuous structures, and the first encapsulation layer 4-1, the third encapsulation layer 4-3, and the fourth encapsulation layer 4-2 have joints.

[0051] The aforementioned joint may be an attachment Figure 4 , 5 The docking form shown in Figure 6 can also be as shown in the appendix. Figure 8 The attached image shows Figure 6 The fourth structure is an example of a modified overlapping form, which includes: a) the first sealing layer 4-1 covering part of the third sealing layer 4-3 and part of the fourth sealing layer 4-4; b) the second sealing layer 4-2 covering part of the third sealing layer 4-3 and part of the fourth sealing layer 4-4; c) the third sealing layer 4-3 covering part of the first sealing layer 4-1 and part of the second sealing layer 4-2; d) the fourth sealing layer 4-4 covering part of the first sealing layer 4-1 and part of the second sealing layer 4-2.

[0052] See appendix Figure 2 A first end electrode 5 is formed on the first end face and electrically connected to the first conductive layer 2, and a second end electrode 6 is formed on the second end face and electrically connected to the second conductive layer 3.

[0053] The first conductive layer 2 and the second conductive layer 3 comprise metal foil, metal coating, or metal plating. That is, the first conductive layer 2 and the second conductive layer 3 may be copper foil, electroplated layer, metal plating, or printed metal layer, respectively, wherein the copper foil may be nickel-plated copper foil.

[0054] After the first conductive layer 2 and the second conductive layer 3 are patterned and hollowed out, part of the core material 1 is exposed.

[0055] For example, see attached Figure 2 The first conductive layer 2 and the second conductive layer 3 include disconnected portions, wherein one disconnected portion is 0-10 mm away from the first end face (h2), and the other disconnected portion is 0-10 mm away from the second end face (h1), preferably h1 and h2 are 1-5 mm. The cross-sectional structure of one disconnected portion along the width direction of the component is shown in the attached figure. Figure 7 The width of the disconnected part is 0.05 to 5 mm.

[0056] A first insulating sheet 7 is formed on the first conductive layer 2, and a second insulating sheet 8 is formed on the second conductive layer 3.

[0057] A third conductive layer 9 is formed on the surface of the first insulating sheet 7, extends between the first end electrode 5 and the first end face, and continues to extend to the surface of the second insulating sheet 8. A fourth conductive layer 10 is formed on the surface of the second insulating sheet 8, extends between the second end electrode 6 and the second end face, and continues to extend to the surface of the first insulating sheet 7. The structures of the third conductive layer 9 and the fourth conductive layer 10 are shown in the attached figure. Figure 9 The third conductive layer 9 and the fourth conductive layer 10 are roughly U-shaped. The third conductive layer 9 and the fourth conductive layer 10 can be electroplated copper layers. The electroplated layer can achieve excellent contact conductivity. The electroplated layer itself is integral. Therefore, the setting of the third conductive layer 9 and the fourth conductive layer 10 is equivalent to adding conductive layers between the first end electrode 5 and the second end electrode 6 and the core material 1 to improve conductivity and increase contact reliability by contacting the end electrode with another integral U-shaped conductive element.

[0058] The terminal electrodes can be as follows: Figure 2 The structure shown has a first end electrode 5 and a second end electrode 6 that are "U" shaped and extend from the first and second end faces to a portion of the top face and a portion of the bottom face, respectively.

[0059] The terminal electrode can also be as shown in the attached figure. Figure 10 Another structure shown is that the first end electrode 5 and the second end electrode 6 are "L" shaped and extend from the first and second end faces to part of the bottom face, respectively.

[0060] The first terminal electrode 5 and the second terminal electrode 6 are any one of copper, nickel, or tin layers, or any combination of two or three of them.

[0061] The encapsulation layer 4 is made of any one or a combination of two or more of the following: polyimide, prepreg, solder resist ink, silicone resin, fluoropolymer, epoxy resin, or polyolefin.

[0062] The first insulating sheet 7 and the second insulating sheet 8 are made of any one or a combination of two or more of the following: polyimide, prepreg, solder resist ink, silicone resin, fluorine resin, epoxy resin, or polyolefin.

[0063] To enable the thermistor to possess various electrical properties, the core material 1 can consist of an upper core material and a lower core material combined in phase, as shown in the attached figure. Figure 11 As shown, the upper and lower core materials have their own conductive layers on their adjacent upper and lower surfaces, which are separated by an insulating sheet. The upper and lower core materials are arranged in parallel between the two end electrodes. The upper surface of the upper core material and the lower surface of the lower core material are electrically connected to the first end electrode 5, and the lower surface of the upper core material and the upper surface of the lower core material are electrically connected to the second end electrode 6. The position of the disconnection on the conductive layer is set according to the electrical connection requirements, that is, the upper and lower disconnections are located at the same end, while the two middle disconnections are located at the other end. Furthermore, different polymer substrates and / or conductive materials are used in the upper and lower core materials respectively.

[0064] In addition, if the material of the encapsulation layer 4 is the same as that of the polymer substrate in the core material 1, or if the encapsulation layer 4 is well integrated with the side of the core material 1, for example, if the polymer substrate of the core material 1 is polyvinylidene fluoride, then the material of the encapsulation layer 4 is a fluorinated resin.

[0065] The following comparison of four sets of data from two pairs under different encapsulation conditions using different core materials illustrates the effectiveness of the thermistor of this invention in resisting environmental shock:

[0066] Table 1: Four Example Situations

[0067]

[0068]

[0069] Table 2: Double 85 Test Data Table

[0070] Comparative Example 1 Example 1 Comparative Example 2 Example 2 R0(mΩ) 146.3 144.7 74.5 77.9 R1 (Dual 85, 1000hr) 270.7 169.3 156.5 98.2 R1 / R0 1.85 1.17 2.1 1.26

[0071] In the table, R0 represents the initial resistance (room temperature), R1 is maintained for 1000 hours in an environment with 85% humidity and 85 degrees Celsius, and R0 / R1 refers to the double 85% change rate. The smaller the value of the double 85% change rate, the less impact it is on the extreme environment.

[0072] As can be seen from Table 2, the encapsulation structure of the present invention enables the overcurrent protection element to withstand extreme environmental impacts better.

[0073] The following will explain some other design principles of the present invention:

[0074] Because this invention aims to overcome some of the defects caused by the process of cutting components from a whole sheet of material, while also needing to retain as many processes as possible during the overall board fabrication, a break is provided on each of the first and second conductive layers. A small portion of the conductive layer is left on the adjacent end face of the break. This is because there will be positional errors if the break is made after the entire conductive layer is laminated. To facilitate the making of the break and to ensure that the conductive layer can be exposed on the adjacent end face of an adjacent component during cutting, and to ensure sufficient electrical connection between the electrode and the conductive layer when the electrode is plated.

[0075] In addition, for clarity, the thickness of the product has been increased in the attached diagram. The first and second conductive layers are relatively thin, and the first and second insulating sheets are thin sheets made of fiber fabric and insulating resin composite and cured. The insulating sheets are heat-pressed onto the conductive layers and can extend into the break portion, as shown in the attached diagram. Figure 2 As shown.

[0076] The above description is only a specific embodiment of the present invention. Various examples and illustrations do not constitute a limitation on the substantive content of the present invention. Those skilled in the art can make modifications or variations to the above-described specific embodiments after reading the specification without departing from the substance and scope of the invention.

Claims

1. An overcurrent protection element, comprising a core material, characterized in that: The core material includes a top surface, a bottom surface opposite to the top surface, two side surfaces located between the top surface and the bottom surface, and two end surfaces, the two side surfaces being a first side surface and a second side surface, and the two end surfaces being a first end surface and a second end surface. A first conductive layer is formed on the top surface of the core material, and a second conductive layer is formed on the bottom surface of the core material; An encapsulation layer covers the first conductive layer and the second conductive layer, and encapsulates at least one of the said sides; A first terminal electrode is electrically connected to the first conductive layer, and a second terminal electrode is electrically connected to the second conductive layer; The encapsulation layer includes a first encapsulation layer, a second encapsulation layer, a third encapsulation layer, and a fourth encapsulation layer, which respectively cover the first conductive layer, the second conductive layer, the first side surface, and the second side surface. The first encapsulation layer, the third encapsulation layer, and the fourth encapsulation layer are continuous structures, and the second encapsulation layer has a joint with the third encapsulation layer and the fourth encapsulation layer. The first conductive layer and the second conductive layer include a break portion, wherein one break portion is 0~10mm away from the first end face and the other break portion is 0~10mm away from the second end face; A first insulating sheet is formed on the first conductive layer, and a second insulating sheet is formed on the second conductive layer; A third conductive layer is formed on the surface of the first insulating sheet and extends between the first end electrode and the first end face and continues to extend to the surface of the second insulating sheet. A fourth conductive layer is formed on the surface of the second insulating sheet and extends between the second end electrode and the second end face and continues to extend to the surface of the first insulating sheet.

2. The overcurrent protection element according to claim 1, characterized in that: The first conductive layer and the second conductive layer comprise metal foil, metal coating, or metal plating.

3. The overcurrent protection element according to claim 1, characterized in that: The first conductive layer and the second conductive layer comprise nickel-plated copper foil.

4. The overcurrent protection element according to claim 1, characterized in that: The first end electrode and the second end electrode are "L" shaped and extend from the first and second end faces to a portion of the bottom surface, respectively.

5. The overcurrent protection element according to claim 1, characterized in that: The first end electrode and the second end electrode are U-shaped and extend from the first and second end faces to a portion of the top surface and a portion of the bottom surface, respectively.

6. The overcurrent protection element according to claim 1, characterized in that: The first end electrode and the second end electrode are any one of a copper layer, a nickel layer, or a tin layer, or any combination of two or three of them.

7. The overcurrent protection element according to claim 1, characterized in that: The encapsulation layer comprises any one or any combination of two or more of the following: polyimide, prepreg, solder resist ink, silicone resin, fluoropolymer, epoxy resin, or polyolefin.

8. The overcurrent protection element according to claim 1, characterized in that: The first insulating sheet and the second insulating sheet comprise any one or any combination of two or more of the following: polyimide, prepreg, solder resist ink, silicone resin, fluorinated resin, epoxy resin, or polyolefin.

9. The overcurrent protection element according to claim 1, characterized in that: The core material comprises an upper core material and a lower core material combined together.

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