Surface mount low resistance polymer positive temperature coefficient component and method of production thereof

Abstract

The application discloses a surface-mounted low-resistance polymer positive temperature coefficient component and a production method thereof. The component comprises a PTC chip composed of a PPTC material and an electrode; and a shell with a layered structure. The shell comprises a base plate with a chip hole in the center, and the PTC chip is embedded in the chip hole; the upper and lower surfaces of the base plate are respectively provided with a cover plate integrated with the base plate, and the outer surface of each cover plate is attached with a first conductive film; a conductor is arranged in the blind hole of each surface to connect the first conductive film with the electrode of the PTC chip; the first conductive film is attached to one end of the cover plate and extends to the other end; an insulating cover plate is arranged outside the first conductive film; second conductive films are arranged at the left and right ends of the outer layer of the insulating cover plate, and the outer surface of the second conductive film is provided with a solder pad; and each end of the shell is connected through a conductive end head between layers from top to bottom. The position of the blind hole can be changed, the miniaturization of the product can be met, the insulating cover plate increases the mechanical properties and weather resistance of the product.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of overcurrent and temperature protection electronic component materials, and particularly relates to a surface-mounted low-resistance polymer positive temperature coefficient component and a production method thereof. BACKGROUND

[0002] The polymer positive temperature coefficient component, also known as a positive temperature coefficient thermistor (PPTC for short), is composed of a high polymer material with crystallization characteristics, conductive fillers and non-conductive fillers. The fillers are uniformly dispersed in the high polymer material. The high polymer material is usually polyolefin (such as polyethylene, polypropylene or a copolymer of ethylene and propylene), fluorine-containing polyolefin (such as polyvinylidene fluoride, ethylene / tetrafluoroethylene copolymer) and the like; the conductive fillers are usually carbon black, metal powder (such as copper, nickel and the like) or metal ceramic powder (such as titanium carbide or tungsten carbide).

[0003] The positive temperature coefficient component made of the PPTC composite material has a rapid response to current and temperature, is widely used in overcurrent and overtemperature protection devices of a circuit, and is used in series in the circuit. When the circuit is normally working, the current flowing through the component is low, and the temperature is also low. The component presents a low resistance state, and does not affect the normal working of the circuit. However, when overcurrent or overtemperature caused by a circuit fault occurs, the temperature of the component will suddenly rise, causing the resistance of the component to rapidly change from low resistance to high resistance (the logarithmic ratio of high resistance / low resistance is 4 or more, which is also called PPTC strength). The voltage is fully loaded on the component, so that the circuit presents an almost open circuit state, thereby achieving the purpose of protecting the circuit. When the fault is eliminated, the temperature of the component decreases, and the resistance value of the component can also return to a low resistance state. Therefore, the positive temperature coefficient component has been widely applied to the overcurrent and overtemperature protection fields of communication equipment, automotive electronics, computers, household and industrial control electrical equipment and the like.

[0004] The traditional positive temperature coefficient component has a relatively large size, a relatively stable structure and a mature process. The thermal effects (such as the temperature of reflow soldering, coating heat curing and injection molding) in assembly and application have relatively small influences on the material and structure of the product, and the influences of environmental factors such as temperature and humidity in the environment are also relatively small. Therefore, the performance and reliability of the component are relatively good.

[0005] However, the development of emerging markets requires more and more small-sized PTC components, and the components should be suitable for surface mounting process, easy to assemble and reduce the space requirement, which puts forward higher requirements for the design and manufacturing technology of PTC components. First, if the small-sized PTC components adopt the structure similar to that of large-sized PTC components, the stability of the structure is poor, and the thermal effect (such as the temperature of reflow soldering, coating heat curing, injection molding) in assembly and application can easily cause structural deformation, thereby affecting the performance of the product. Secondly, due to the relatively small size, the temperature and humidity of the PTC component can easily affect the material and structure of the product, thereby causing a sharp decline in the long-term reliability of the product; especially for low resistivity carbide, nitride and some metal powder conductive filler made PPTC composite material, because it is more susceptible to environmental factors (temperature, humidity, solvent, chemicals, air, etc.), the PTC component made of it is more sensitive to environmental factors (temperature, humidity, solvent, chemicals, air, etc.), especially tungsten carbide, titanium carbide and other ceramic conductive materials are easily affected by environmental factors such as temperature and humidity, and their conductive properties will be affected, thereby affecting the conductive properties and reliability of the PPTC material. Therefore, in order to obtain relatively high performance and reliability, PPTC, especially small-sized PPTC components using ceramic conductive materials as fillers, need to isolate PPTC material from the external environment.

[0006] Chinese patent document CN102610341A discloses a surface-mounted polymer PTC element, which is embedded in the insulating boss of the PTC chip gap portion by passing the left and right end heads through the upper and lower cover plates, without directly contacting the PTC chip and without etching the upper and lower plates on both sides of the PTC chip, so that the arc resistance is greatly improved; but the core material of the PPTC of this patent is exposed to the outside, and is not isolated from the external environment, so that some ceramic conductive materials such as tungsten carbide and titanium carbide are easily affected by environmental factors such as temperature and humidity, and their conductive properties will be affected, thereby affecting the conductive properties and reliability of the PPTC material.

[0007] Chinese patent document CN101312087A discloses a surface-mounted overcurrent and overtemperature protection element; comprising a PTC chip composed of a high-molecular composite conductive material, two electrode plates arranged on the upper and lower surfaces of the PTC chip; the PTC chip is wrapped in a shell, the shell is a layered structure, comprising: an inner layer composed of a substrate, a central hole of the substrate for accommodating the PTC chip; an intermediate layer composed of two upper and lower cover plates, respectively covering the upper and lower surfaces of the substrate, the outer surface of each cover plate is attached with a first conductive film, and the first conductive films on the two cover plates are respectively electrically connected with the two electrode plates of the PTC chip; an outer layer composed of two left and right solder pads and a solder mask between the two solder pads, the two solder pads are respectively electrically connected with the first conductive films on the two cover plates. However, the blind hole of the product can only be located between the two solder pads, which will limit the processability of the product, especially when the product of such structure is miniaturized, the solder pads will occupy most of the product space, and the process and processability of the blind hole will be more difficult; in order to ensure the realization and reliable connection of the blind hole, the isolation layer (i.e. the cover plate) is usually thin, so the sealing effect of the whole product is reduced, and the mechanical properties of the product are also weak, the sealing of the product will be damaged when affected by some thermal mechanical effects, and the reliability and weather resistance of the whole product will also be affected. SUMMARY

[0008] The purpose of the present application is to provide a new type of surface-mounted low-resistance polymer positive temperature coefficient device, which uses a unique packaging method to isolate the PPTC material from the external environment, to solve the problems of structural thermal stability and environmental factors (temperature, humidity, solvent, chemicals, air, etc.) causing the reliability of the product to decrease.

[0009] The purpose of the present application is achieved by using the following technical solutions.

[0010] The surface-mounted low-resistance polymer positive temperature coefficient device of the present application comprises: a PTC chip composed of a PPTC high-molecular composite conductive material and upper and lower electrodes; the PTC chip is wrapped in a shell, and the shell is a layered structure; comprising: a substrate with a chip hole in the center, the PTC chip is embedded in the chip hole of the substrate; the upper and lower surfaces of the substrate 1 are respectively provided with an upper cover plate and a lower cover plate which are solidified as a whole, the outer surfaces of the upper and lower cover plates are attached with a first conductive film; each surface is provided with a blind hole passing through the upper and lower cover plates and the first conductive film to the electrode outer surface of the PTC chip on the surface, and a conductive body is arranged in the blind hole to connect the first conductive film with the upper and lower electrodes of the PTC chip.

[0011] Characterized in that the first conductive film of the upper cover plate is attached to the left end of the upper cover plate and extends to at least more than 1 / 2 and not more than 2 / 3 of the right end of the upper cover plate, the first conductive film of the lower cover plate is attached to the right end of the lower cover plate and extends to at least more than 1 / 2 and not more than 2 / 3 of the left end of the lower cover plate, insulating cover plates are respectively arranged outside the first conductive films of the upper and lower cover plates, second conductive films are respectively attached to the left and right ends of the outer layers of the insulating cover plates of the upper and lower cover plates, and solder pads are arranged on the outer surfaces of the second conductive films; and each end of the shell is connected by a conductive end head between the layers from top to bottom.

[0012] Preferably, the conductive body is composed of a metal plating layer in the blind hole.

[0013] Preferably, the first conductive film and the second conductive film are both composed of a metal foil.

[0014] Preferably, each of the left and right ends of the shell is provided with a through hole, and the end head is located in the through hole.

[0015] Preferably, the end head is in the shape of a semicircular hole, a semi-elliptical hole, a rectangular hole or a square hole, and is composed of a metal plating layer.

[0016] Preferably, the solder pad is composed of 2-5 layers of metal plating layers.

[0017] Preferably, the substrate, the cover plate and the insulating cover plate are all composed of a semi-cured composite resin plate, which is cured in a hot pressing process.

[0018] Preferably, the semi-cured composite resin plate is made of one of phenolic resin, epoxy resin, polyimide resin, polytetrafluoroethylene resin, bismaleimide triazine resin, thermosetting polyphenyl ether resin and polyester resin.

[0019] A production method of a surface-mounted low-resistance polymer positive temperature coefficient device, characterized in that it comprises the following steps:

[0020] (1) a high-molecular PPTC composite conductive material and a metal foil electrode plate are compounded and pressed into a sheet, which is then divided into small pieces of a specified shape to obtain PTC chips;

[0021] (2) a semi-cured composite resin plate with the same thickness as the PTC chip is taken, a chip hole is punched in the plate according to a specified arrangement mode, the chip hole is adapted to the size and shape of the PTC chip, and a substrate is obtained;

[0022] (3) Put the PTC chip into the chip hole of the substrate; then put one or more semi-cured composite resin plates on the upper and lower surfaces of the substrate to form upper and lower cover plates, and then respectively stack a layer of metal foil to form a first conductive film; and then hot-press and composite together to form a composite sheet;

[0023] (4) In the upper and lower surfaces of the composite sheet, corresponding to the positions of the PTC chip, respectively punch a plurality of blind holes according to a certain arrangement, and the depth of the blind holes is just enough to penetrate the cover plate to reach the surface of the PTC chip, thereby forming blind holes on the cover plate;

[0024] (5) Copper is plated on the inner wall of the blind hole, and the copper plating layer of the blind hole connects the two side plates of the PTC chip and the first conductive film, respectively;

[0025] (6) Remove the excess metal foil of the upper and lower first conductive films, respectively;

[0026] (7) Put one or more semi-cured composite resin plates on the upper and lower surfaces to form upper and lower insulating cover plates; then respectively stack a layer of roughened metal foil with the rough surface facing inward, and then hot-press and composite together to form a composite sheet; during the hot-pressing process, the semi-cured composite resin plate flows into the blind hole and the etched place of the first conductive film, thereby filling the vacancy;

[0027] (8) Process through holes at corresponding positions of the left and right ends of the composite sheet;

[0028] (9) Etch the upper and lower metal foils to form the shape of a second conductive film;

[0029] (10) Copper is plated on the surface of the through hole and the second conductive film, the upper and lower second conductive films are connected and conductive, and nickel-tin or nickel-gold is further electroplated on the second conductive film to form upper and lower pads, thereby obtaining a composite sheet;

[0030] (11) Cut the composite sheet obtained in step (10) according to the specified unit to obtain the final product.

[0031] Preferably, the metal foil is a copper foil or a silver foil.

[0032] Preferably, in the step (2) and step (8), the punching method is drilling, stamping or laser cutting; in the step (6), the method for removing the excess metal foil is etching, laser cutting or mechanical cutting.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] In the present application, since the upper and lower cover plates and the substrate are all semi-cured composite resin plates of the same material, they will be cured and combined to form an integrated structure during the hot pressing process, realizing complete wrapping of the six surfaces of the PTC chip and burying the PTC chip in the composite resin. The PTC chip is not only provided with stable mechanical strength, but also completely isolated from the external environment, so that the PTC material is not affected by the environmental temperature and humidity, the weather resistance is greatly improved, and the performance is stable and the reliability is high.

[0035] Moreover, unlike the Chinese patent document CN101312087A, the blind hole can only be located between two pads, which will limit the miniaturization of the product. The position of the blind hole for connecting the first conductive film and the electrode of the PTC chip in the present application can be set at any position of the PTC chip, and the positions of the upper and lower blind holes do not have to be corresponding, which will not be affected by the shape and position of the pad, and also increases the area and conductive safety of the first conductive film. Considering the blind hole process capability, the structure of the present application can meet the miniaturization demand of the product. At the same time, the present application also sets the upper and lower insulating cover plates and the second conductive film, which can further increase the mechanical properties and weather resistance of the product, and ensure that the product still has sufficient mechanical properties after miniaturization.

[0036] In addition, the PTC chip of the present application is connected with the external electrode through the blind hole, not the via hole; it is suitable for small size surface mount PPTC device, and can be used for overcurrent, overtemperature protection, temperature indication and temperature switch; compared with the traditional device, it has the same high performance but the size is significantly reduced, the unique packaging mode provides stable and high reliability performance, can be reflow soldered and is not affected by environmental factors; therefore, it can meet the application demand of higher reliability requirement of industry and automobile level. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a structural exploded view of the positive temperature coefficient device of the present application.

[0038] Figure 2 It is a combined structure schematic diagram of the positive temperature coefficient device of embodiment 1.

[0039] Figure 3 It is a structure schematic diagram of the upper and lower insulating cover plates.

[0040] Figure 4 It is a combined structure schematic diagram of the positive temperature coefficient device of embodiment 2. DETAILED DESCRIPTION

[0041] Those skilled in the art of the present technology should recognize that the embodiments are only used to illustrate the present application, and are not used as a limitation of the present application, and as long as the embodiments are changed and modified within the scope of the present application, they can be within the scope of the claims of the present application.

[0042] As Figures 1-2 shown. A surface-mounted low-resistance polymer positive temperature coefficient component includes the following parts: a PTC chip 2 composed of a core material made of a high-molecular composite conductive material and metal electrode plates attached to the upper and lower surfaces; the PTC chip 2 is wrapped in a shell, which is a layered structure and includes:

[0043] A substrate 1 made of a semi-cured composite resin plate has a chip hole 101 in the center, and the PTC chip 2 is embedded in the chip hole 101;

[0044] An upper cover plate 11 and a lower cover plate 21 made of a semi-cured composite resin plate cover the upper and lower surfaces of the substrate 1 and the PTC chip 2 respectively, and are integrated with the substrate 1 after curing; a first upper conductive film 12 made of a metal foil is attached to the left end of the upper surface of the upper cover plate 11 and extends to at least more than 1 / 2 and not more than 2 / 3 of the upper cover plate 11 to the right; a first lower conductive film 22 made of a metal foil is attached to the right end of the lower surface of the upper cover plate 12 and extends to at least more than 1 / 2 and not more than 2 / 3 of the lower cover plate 12 to the left;

[0045] An upper blind hole 31 and a lower blind hole 32 are respectively provided at positions corresponding to the PTC chip 2 on the upper cover plate 11, the first upper conductive film 12, the lower cover plate 21 and the first lower conductive film 22; the upper blind hole 31 penetrates the first upper conductive film 12 and the upper cover plate 11 to the upper surface of the PTC chip 2; the lower blind hole 32 penetrates the first lower conductive film 22 and the lower cover plate 21 to the lower surface of the PTC chip 2; a conductive body composed of a metal plating layer is provided on the inner wall of the upper blind hole 31 to connect the first upper conductive film 12 and the upper electrode plate of the PTC chip 2; a conductive body composed of a metal plating layer is provided on the inner wall of the lower blind hole 32 to connect the first lower conductive film 22 and the lower electrode plate of the PTC chip 2;

[0046] An upper insulating cover plate 13 and a lower insulating cover plate 23 made of a semi-cured composite resin plate cover the upper surface of the first upper conductive film 12 and the lower surface of the first lower conductive film 22 respectively;

[0047] A second upper conductive film 14 made of a metal foil is attached to the left and right ends of the upper surface of the upper insulating cover plate 13, and an upper solder pad 15 is provided on the upper surface thereof; a second lower conductive film 24 made of a metal foil is attached to the left and right ends of the lower surface of the lower insulating cover plate 23, and a lower solder pad 25 is provided on the lower surface thereof;

[0048] The left end of the shell is connected between each layer from top to bottom by a conductive left end 41, and the right end is connected between each layer from top to bottom by a conductive right end 51.

[0049] Preferably, asFigure 1 and 3 As shown in FIG. 1, the lower boss 131 of the upper insulating cover plate 13 is fastened to the right end of the upper cover plate 11 and the first upper conductive film 12, and the lower cylinder 132 is inserted into the upper blind hole 31; the upper boss 231 of the lower insulating cover plate 23 is fastened to the left end of the lower cover plate 21 and the first lower conductive film 22, and the upper cylinder 232 is inserted into the lower blind hole 32.

[0050] Preferably, as shown in FIG. 1, the left and right ends of the shell are each provided with a through hole. The left through hole 3 passes through the left end of the upper pad 15, the second upper conductive film 14, the upper insulating cover plate 13, the first upper conductive film 12, the upper cover plate 11, the substrate 1, the lower cover plate 21, the lower insulating cover plate 23, the second lower conductive film 24 and the lower pad 25 from top to bottom, and the inner wall is provided with a conductive left end head 31 connected in the up-down direction. Figure 1 and 3 As shown in FIG. 1, the left and right ends of the shell are each provided with a through hole. The left through hole 3 passes through the left end of the upper pad 15, the second upper conductive film 14, the upper insulating cover plate 13, the first upper conductive film 12, the upper cover plate 11, the substrate 1, the lower cover plate 21, the lower insulating cover plate 23, the second lower conductive film 24 and the lower pad 25 from top to bottom, and the inner wall is provided with a conductive left end head 31 connected in the up-down direction.

[0051] Preferably, as shown in FIG. 1, the left and right ends of the shell are each provided with a through hole. The left through hole 3 passes through the left end of the upper pad 15, the second upper conductive film 14, the upper insulating cover plate 13, the first upper conductive film 12, the upper cover plate 11, the substrate 1, the lower cover plate 21, the lower insulating cover plate 23, the second lower conductive film 24 and the lower pad 25 from top to bottom, and the inner wall is provided with a conductive left end head 31 connected in the up-down direction. Figure 4 As shown in FIG. 1, the left and right ends of the shell are each provided with a through hole. The left through hole 3 passes through the left end of the upper pad 15, the second upper conductive film 14, the upper insulating cover plate 13, the first upper conductive film 12, the upper cover plate 11, the substrate 1, the lower cover plate 21, the lower insulating cover plate 23, the second lower conductive film 24 and the lower pad 25 from top to bottom, and the inner wall is provided with a conductive left end head 31 connected in the up-down direction.

[0052] Embodiment 1

[0053] The surface-mounted low-resistance polymer positive temperature coefficient device described above can be manufactured by the following method:

[0054] (1) The high-molecular PTC composite conductive material is pressed into a sheet with a thickness of 0.05-0.50 mm, and then copper foils with a thickness of 0.035 mm are attached to the upper and lower surfaces of the sheet by using a flat hot press to form a composite sheet with a thickness of 0.12-0.64 mm. After chemical or electronic irradiation crosslinking, the PTC chip is obtained by using a scribing machine, laser cutting or stamping;

[0055] (2) A semi-solid composite resin plate with the same thickness as the PTC chip is taken, and a chip hole is punched according to the specified arrangement by drilling or stamping. The size and shape of the chip hole are adapted to those of the PTC chip, and the substrate is obtained.

[0056] (3) Put the PTC chip into the chip hole of the substrate; cover one or more semi-cured composite resin plates on the upper and lower surfaces of the substrate to form upper and lower cover plates; then stack a layer of roughened metal foil as the upper and lower first conductive films, with the rough surface facing inwards, and then hot-press and combine them together, with the semi-cured composite resin plates of the upper and lower cover plates and the substrate being fused and solidified into one body under the hot-pressing to form a composite sheet;

[0057] (4) At the positions corresponding to the center of the PTC chip on the upper and lower surfaces of the composite sheet, use a drilling machine to punch a plurality of blind holes according to a certain arrangement, with the depth of the blind holes being just enough to penetrate the cover plates to reach the surface of the PTC chip, forming upper and lower blind holes;

[0058] (5) Copper is plated on the inner wall of the blind hole, and the two side plates of the PTC chip are connected to the first conductive film through the copper plating layer in the hole, with the thickness of the copper plating being 0.02-0.05 mm;

[0059] (6) Use etching method to etch away the excess 1 / 3 of the metal foil of the upper and lower first conductive films;

[0060] (7) Cover one or more semi-cured composite resin plates on the outer surface of the first conductive film to form upper and lower insulating cover plates; then stack a layer of roughened metal foil, with the rough surface facing inwards, and then hot-press and combine them together to form a composite sheet; during the hot-pressing process, as shown in FIG. 5, the semi-cured composite resin plates flow into the blind holes and the etched-away parts of the first conductive film to fill the gaps; Figure 3

[0061] (8) Use drilling or stamping method to process circular or elliptical through holes at the corresponding positions of the left and right ends of the composite sheet;

[0062] (9) Use etching method to etch the shape of the second conductive film on the upper and lower metal foils;

[0063] (10) Copper is plated in the through holes and on the surface of the second conductive film to connect and conduct the upper and lower second conductive films, and nickel-tin or nickel-gold is further electroplated on the second conductive film to form upper and lower solder pads, obtaining a composite sheet;

[0064] (11) Cut the composite sheet obtained in step (10) into specified units to obtain the final product, as shown in FIG. 6. Figure 2

[0065] Example 2

[0066] The steps (1)-(7) of this example are the same as those of Example 1 and are omitted.

[0067] (8) Use drilling or stamping method to process long strip-shaped through holes at the corresponding positions of the left and right ends of the composite sheet;​​

[0068] (9) Using an etching method, the shape of the second conductive film is etched on the upper and lower metal foils;

[0069] (10) Copper is plated inside the through hole and on the surface of the second conductive film to connect the upper and lower second conductive films and continue to electroplate nickel-tin or nickel-gold on the second conductive film to form upper and lower pads, thus obtaining a composite board.

[0070] (11) Cut the composite board obtained in step (10) into specified units to obtain the final product, such as... Figure 4 As shown, there are no through holes at either end of the entire shell, and the two ends are straight.

Claims

1. A surface-mount low-resistance polymer positive temperature coefficient component, comprising: A PTC chip composed of PPTC polymer composite conductive material and upper and lower electrodes; The PTC chip is encased in a shell, which has a layered structure and includes: a substrate with a centrally located chip hole, in which the PTC chip is embedded; an upper cover plate and a lower cover plate integrally formed therewith on the upper and lower surfaces of the substrate, respectively; a first upper conductive film and a first lower conductive film respectively attached to the outer surfaces of the upper and lower cover plates; an upper blind hole penetrating the first upper conductive film and the upper cover plate to the upper surface of the PTC chip, and a lower blind hole penetrating the first lower conductive film and the lower cover plate to the lower surface of the PTC chip; conductors are provided in the upper and lower blind holes to connect the first upper conductive film and the first lower conductive film to the upper and lower electrodes of the PTC chip respectively. The first upper conductive film extends from the left end to the right end to more than 1 / 2 but not more than 2 / 3 of the upper cover plate, and the first lower conductive film extends from the right end to the left end to more than 1 / 2 but not more than 2 / 3 of the lower cover plate. An upper insulating cover plate and a lower insulating cover plate are respectively provided on the upper surface of the first upper conductive film and the lower surface of the first lower conductive film; the second upper conductive film is attached to the left and right ends of the upper surface of the upper insulating cover plate, and an upper pad is provided on its upper surface; the second lower conductive film is attached to the left and right ends of the lower surface of the lower insulating cover plate, and a lower pad is provided on its lower surface; the left and right ends of the shell are connected from top to bottom through conductive left and right ends respectively. The lower boss of the upper insulating cover plate is fastened to the right end of the upper cover plate and is flush with the thickness of the first upper conductive film, with its lower column inserted into the upper blind hole; the upper boss of the lower insulating cover plate is fastened to the left end of the lower cover plate and is flush with the thickness of the first lower conductive film, with its upper column inserted into the lower blind hole. The substrate, upper cover plate, lower cover plate, upper insulating cover plate, and lower insulating cover plate are all made of semi-cured composite resin plates, which are cured during hot pressing.

2. The surface-mount low-resistance polymer positive temperature coefficient component according to claim 1, characterized in that, The conductor is composed of metal plating in the upper and lower blind holes.

3. The surface-mount low-resistance polymer positive temperature coefficient component according to claim 1, characterized in that, The first upper conductive film, the first lower conductive film, the second upper conductive film, and the second lower conductive film are all made of metal foil.

4. The surface-mount low-resistance polymer positive temperature coefficient component according to claim 1, characterized in that, The left end of the housing is provided with a left through hole, and its inner wall is provided with a conductive left end head for vertical connection; the right end is provided with a right through hole, and its inner wall is provided with a conductive right end head for vertical connection; the left end head and the right end head are semi-circular, semi-elliptical, rectangular or square holes, and are made of metal plating.

5. The surface-mount low-resistance polymer positive temperature coefficient component according to claim 1, characterized in that, The upper and lower pads are each composed of 2 to 5 layers of metal plating.

6. The surface-mount low-resistance polymer positive temperature coefficient component according to claim 1, characterized in that, The semi-cured composite resin board is made from one of the following: phenolic resin, epoxy resin, polyimide resin, polytetrafluoroethylene resin, bismaleimide triazine resin, thermosetting polyphenylene ether resin, and polyester resin.

7. The method for manufacturing a surface-mount low-resistance polymer positive temperature coefficient device according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) After the polymer PPTC composite conductive material and the metal foil electrode plate are combined, they are pressed into sheets and then divided into small pieces of a specified shape to obtain PTC chips; (2) Take a semi-cured composite resin board with the same thickness as the PTC chip, and punch out chip holes according to the specified arrangement. The chip holes are adapted to the size and shape of the PTC chip to obtain a substrate; (3) Place the PTC chip into the chip hole of the substrate; then cover the upper and lower sides of the substrate with one or more semi-cured composite resin plates to form upper and lower cover plates, and then stack a layer of metal foil to form a first conductive film; then hot press them together to form a composite sheet. (4) On the upper and lower surfaces of the composite sheet, at positions corresponding to the PTC chip, several blind holes are drilled in a certain arrangement. The depth of the blind holes is such that they just penetrate the cover plate and reach the surface of the PTC chip, thus forming blind holes on the cover plate. (5) Copper is plated on the inner wall of the blind hole, and the copper plating of the blind hole connects the two electrode plates of the PTC chip to the first conductive film respectively. (6) Remove the excess metal foil from the upper and lower first conductive films respectively; (7) Cover the upper and lower surfaces with one or more semi-cured composite resin boards to form upper and lower insulating cover plates; then stack a layer of roughened metal foil with the rough side of the metal foil facing inward, and then hot press them together to form a composite sheet; during the hot pressing process, the semi-cured composite resin board flows into the blind hole and the place where the first conductive film is etched away, filling the gap. (8) Process through holes at the corresponding positions on the left and right ends of the composite sheet; (9) Using an etching method, the shape of the second conductive film is etched on the upper and lower metal foils; (10) Copper is plated inside the through hole and on the surface of the second conductive film to connect the upper and lower second conductive films and continue to electroplate nickel-tin or nickel-gold on the second conductive film to form upper and lower pads, thus obtaining a composite board. (11) Cut the composite board obtained in step (10) into specified units to obtain the final product.

8. The production method according to claim 7, characterized in that, The metal foil is either copper foil or silver foil.

9. The production method according to claim 7, characterized in that, In steps (2) and (8), the drilling method is drilling, punching or laser cutting; in step (6), the method of removing excess metal foil is etching, laser cutting or mechanical cutting.

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