CN102184816A - Suspended-fuse-wire-type surface-mount fuse and manufacturing method thereof - Google Patents

Abstract

The invention discloses a suspended fuse type surface mount fuse and a manufacturing method thereof. In the fuse, the exposed end of the fuse is bent to be placed close to the end face of the insulator, so that the end face electrode covers the exposed curved end of the fuse. On the general surface, for a new fuse that has just been manufactured, the entire curved end of the fuse is in contact with the end electrode. As long as the entire curved end of the fuse is in contact with the end-face electrode, the fuse and the end-face electrode can be connected, thereby ensuring the reliability of the connection between the fuse and the end-face electrode; The curved end outside the insulator is completely arranged in the end face electrode, which also ensures the protection of the fuse and prevents flashover of the molten fuse on the end face during blowing. By manufacturing multiple fuses on a large substrate at the same time, and then cutting and separating a single fuse, the batch processing of fuses is realized and the production efficiency is improved. The end face electrodes of the manufactured fuse cover the entire end face and the bending of the fuse end, to improve the solderability of the fuse on the PCB.

Description

Suspended fuse type surface mount fuse and manufacturing method thereof

technical field

The present invention relates to a floating fuse type surface mounting fuse, and also relates to a manufacturing method of the fuse.

Background technique

With the development of science and technology, electric/electronic products are increasingly diversified and complex, and the circuit protection components used are no longer simple glass tube fuses in the past, but have developed into a wide variety of new electronic components. As a new type of thin, light and small component, the surface mount fuse is suitable for the protection circuit of various electronic products with compact structure and small size, and its application field is very wide.

Suspended fuse type fuses and solid device type fuses are the two main types of small surface mount fuses. The floating fuse type small fuse is to suspend the fuse (wire) in the hollow shell. Both ends of the fuse are fixed in different ways with terminal electrodes. Since the heat transfer coefficient of air is much smaller than that of most solids, the floating fuse type fuse requires less energy to blow the fuse than the solid device type fuse, and its resistance can also be smaller.

The company's AirMatrix series of small fuses are suspended in a hollow housing with fuses (wires), which have the advantages of low resistance and low energy consumption, and can be produced quickly and in large quantities through corresponding manufacturing methods.

The reliability of the connection between the fuse (wire) and the terminal is an important indicator of the floating fuse type fuse. The traditional method of connecting and fixing the fuse to the terminal is to use solder to solder the two ends of the fuse to the two terminals. The disadvantage of this design is that the solder will form a low-melting point alloy with commonly used fuse materials, such as copper, when it melts. The formation of this low-melting point alloy will reduce the consistency of the fusing characteristics of the fuse. U.S. Patent US2010245025 (A1) discloses the structure of a new type of surface mount fuse that does not require soldering to connect the fuse to the terminal. The surface mount fuse includes a housing, two terminal metal caps, and an extension To the fuse outside the casing and the metal cap of the terminal, the fuse is bent on the outer surface of the metal cap of the terminal to form an electrical connection. When the fuse is soldered to the PCB board, the solder paste used for welding will fuse the fuse, the metal cap of the terminal and The PCB board is connected as a whole to ensure that there is no solder inside the fuse and that the fusing characteristics of the fuse are consistent. However, in this fuse, the terminal metal cap is used, and the fuse, the terminal metal cap and the PCB board are connected together by the solder paste used when soldering the PCB board. , which will lead to poor connection between the fuse and the end cap; and the welding of the fuse is directional, that is, the welding surface must be in the direction of the wire bending, which brings great inconvenience to production and processing; furthermore, the shell of the fuse It needs to be assembled one by one with the metal cap, the production efficiency is low, and the connection strength between the shell and the metal cap is difficult to guarantee. Another fuse is disclosed in US2010245025 (A1), which includes a glass shell and a fuse extending out of the shell. There is no solder inside the fuse, which can make the fusing characteristics of the fuse consistent, but the fuse is passed Those fixed by hot pressing or encapsulation or metallization also need to be assembled one by one, the production efficiency is low, and the outer shell is glass, which is easy to break.

Japanese patent publication JP2006-244948 discloses a method of manufacturing a floating fuse (wire) type surface mount fuse by laminating two layers of circuit boards. In the fuse made by this method, the two ends of the fuse extend to the end of the insulator In addition to the concave surface, the end surface of the insulator is provided with concave surface covering electrodes, and the two ends of the side of the insulator are provided with side terminal electrodes, and the side terminal electrodes of the corresponding ends are electrically connected with the concave surface covering electrodes, and the two ends of the fuse form a point with the concave surface covering electrodes. Contact, although the fuse avoids the use of metal caps and glass shells, and realizes mass production, and it is convenient to weld when soldering on the PCB board, but it cannot guarantee the reliability of the connection between the two ends of the fuse and the concave covering electrode through point contact. Especially when the fuse is subjected to cold and heat shocks, the difference in expansion and contraction between the fuse and the circuit board and electrodes can easily lead to connection failure. In addition, because the fuse of the fuse made by this method protrudes straight out of the end of the insulator Except for the concave surface of the fuse, the protection of the electrode covered by the concave surface cannot be obtained, and when the fuse is blown, the flashover may shoot out.

Contents of the invention

The first object of the present invention is to provide a floating fuse type surface mount fuse in which the two ends of the fuse extending outside the end faces of the insulator are bent and placed close to the corresponding end faces and covered by the end face electrodes. Hold the total surface of the curved end of the fuse, which not only ensures the reliability of the connection between the end of the fuse and the electrode on the end face; but also ensures the protection of the fuse and prevents the melted fuse from flying on the end face arc;

The second object of the present invention is to mass-process the manufacturing method of the floating fuse type surface mount fuse.

In order to achieve the above object, the present invention adopts following technical scheme:

The present invention firstly relates to a floating fuse type surface mount fuse, comprising

An insulator with an inner cavity, the insulator has a first cover plate and a second cover plate stacked on top of each other, grooves are opened on the opposite inner sides of the first cover plate and the second cover plate, and the first cover plate and the second cover plate are provided with grooves. The grooves of the cover plate and the second cover plate are closed to form the inner cavity;

Side terminal electrodes, the two ends of the outer surface of at least one of the first cover plate and the second cover plate are provided with the side terminal electrodes;

a fuse, the fuse is sandwiched between the first cover plate and the second cover plate, and the middle part of the fuse is suspended in the inner cavity, and both ends of the fuse are protruding beyond the end faces of said insulator;

End face electrodes, the end face electrodes are provided on both ends of the insulator, and the corresponding end face electrodes are electrically connected to the side end electrodes;

Both ends of the fuse exposed outside the insulator are bent, and the bent ends of the fuse are set close to the corresponding end faces of the insulator, and the end electrodes cover the curved ends of the fuse. Ends.

In the above fuse, the exposed end of the fuse is bent to be placed close to the end surface of the insulator, so that the end surface electrode covers the total surface of the exposed curved end of the fuse. For point contact, the contact area between the end of the fuse and the end electrode increases. For a new fuse that has just been manufactured, the entire curved end of the fuse is in contact with the end electrode. When the impact occurs, even if there is a difference in expansion and contraction between the fuse, the end electrode and the insulator, as long as the entire curved end of the fuse is in contact with the end electrode, the connection between the fuse and the end electrode can be made, thus ensuring the fuse. Reliable connection with the end face electrode; and in the fuse, the curved end of the fuse exposed outside the insulator is completely set in the end face electrode, which also ensures the protection of the fuse and prevents the melted fuse from being on the end face when the fuse is broken. Furthermore, the fuse can be made of low-melting-point metals, and there is no need to worry about the fuse being melted to the outside, and the fuse can also be made of non-corrosion-resistant materials, so there is no need to worry about the fuse, especially the fuse. The end faces are corroded.

Preferably, the end face electrode covers the entire end face of the insulator.

Further preferably, both ends of the insulator have a central concave surface and two side surfaces connected to the central concave surface, and the central concave surface extends from the outer surface of the first cover plate opposite to the inner surface to the On the outer side of the second cover plate opposite to the inner side, the curved end of the fuse is located in the corresponding middle concave surface and is arranged close to the concave surface, and the end electrode covers the middle concave surface , the side surfaces of the two sides and the curved end of the fuse, so that compared with the Japanese patent document mentioned in the background technology, only the concave surface has a covering electrode, and the fuse of the present invention increases the covering area of the end electrode , thus increasing the solderability of the fuse, making it easier for the fuse to climb tin when soldered on the PCB, and minimizing soldering failure.

Preferably, on the first cover plate and the second cover plate, the two ends of the outer surface opposite to the inner surface are respectively provided with the side terminal electrodes, and the first cover plate and the second cover plate The side end electrodes of the corresponding ends are electrically connected to the end face electrodes. In this way, when the fuse is soldered to the PCB, the side electrode on the first cover or the second cover can be attached to the PCB for soldering without considering the directionality.

Preferably, the opposite inner surfaces of the first cover and the second cover are bonded and fixed, and the fuse is fixed between the opposite inner surfaces of the first cover and the second cover by bonding.

A method for preparing a floating fuse type surface mount fuse, comprising the following steps:

(1) Prepare two substrates and fuses that will form the first cover and the second cover, process and form side electrode patterns on the side of at least one of the substrates, and process on the sides of the two substrates respectively A groove array is formed, and a perforation array is formed on the side surfaces of the two substrates respectively. On the substrate having both the side electrode pattern and the groove array, the side electrode pattern and the groove arrays are disposed on opposite sides, and the through holes pass through the side terminal electrode patterns;

(2) The two substrates are stacked and bonded, the fuse is sandwiched between the two substrates, and bonded on the opposite sides of the two substrates to ensure that the two substrates correspond to each other. The grooves of the two substrates are closed together to form a cavity array, and the corresponding through holes on the two substrates are directly connected to each other, and part of the fuse is suspended in the cavity, and part of the fuse is exposed in the through hole;

(3) Cutting the two superimposed and bonded substrates along the middle part of each perforation, cutting out the end faces of the first cover plate and the second cover plate, and cutting off the fuse, the first cover plate and the end faces of the second cover plate have the central concave surface formed by the perforation, and the two side surfaces connected to the central concave surface, and the two ends of the cut fuse are exposed on the first cover plate and the second cover plate. the outside of the corresponding central concave surface of the cover plate;

(4) Bend the exposed ends of the fuse so as to be close to the corresponding middle concave surface of the first cover or the second cover;

(5) Electroplating on the entire end faces of the first cover plate and the second cover plate and the curved end of the fuse to form end face electrodes, ensuring that the end face electrodes cover the first cover plate and the second cover plate The central concave surface of the cover plate, the side surfaces on both sides and the curved end of the fuse, and the end electrode is electrically connected to the side electrode;

(6) Carry out corresponding cutting according to the cavity array, that is, form a single fuse.

When using the above method to prepare the surface mount fuse of the present invention, the substrate is cut along the middle part of the perforation, and the fuse is cut off, and the fuse is bent close to the concave surface in the middle, and then electroplated, and the electroplated end electrode covers the entire end surface and the fuse. The curved end of the wire makes the connection between the fuse and the end electrode reliable, and by increasing the coverage area of the end electrode, the solderability of the fuse on the PCB board is improved; further, by simultaneously manufacturing multiple on a large substrate fuses, and then cut and separate individual fuses to realize batch processing of fuses and improve production efficiency.

Preferably, the bending at both ends of the fuse is formed by mechanical stamping or high-pressure air blowing.

Preferably, the cutting in the above step (3) is carried out inside the two superimposed and bonded substrates, without cutting to the edge of at least one end of the substrates. This cutting can fully expose the end faces of the first cover plate and the second cover plate, and cut off the fuse, but since the common substrate edge is left, the bending and electroplating operations after cutting can all be aimed at the stacked and bonded parts. The entire substrate is batched, that is, the bending of the end of the fuse on the entire substrate is realized in batches, and the electrode on the end face is electroplated to cover the entire end face and the curved end of the fuse.

Preferably, in the perforation array processing in the above step (1), two substrates are stacked to punch or drill holes. It is ensured that after the two substrates are stacked and bonded, the perforations are aligned without deviation.

Preferably, the side electrode patterns are formed on the sides of the two substrates, and part of the electrode material is removed from the circuit board with the electrode material on the surface to form the substrate provided with the side electrode patterns. There are side electrode patterns on both substrates, so that on the processed fuse, the two ends of the sides of the first cover plate and the second cover plate have side end electrodes, so that the fuse can be used without welding. Considering the directionality, that is, the side terminal electrodes on the first cover plate or the second cover plate can be attached to the PCB board for soldering.

Description of drawings

Accompanying drawing 1 is the perspective view of floating fuse type surface mount fuse among the present invention;

Accompanying drawing 2 is the end view of floating fuse type surface mount fuse among the present invention;

Accompanying drawing 3 is a cross-sectional view along the B-B direction of accompanying drawing 2, schematically drawing side end electrodes and end face electrodes;

Accompanying drawing 4 is the explanatory diagram for the longitudinal and transverse cutting of fuse array when manufacturing the suspended fuse type surface mount fuse of the present invention;

Accompanying drawing 5 is the longitudinal sectional view 1 of two substrates before cutting in the process of manufacturing the suspended fuse type surface mount fuse of the present invention after being stacked and bonded, and the fuse is sandwiched between the two substrates;

Accompanying drawing 6 is the longitudinal cross-sectional view II of two superimposed and bonded substrates cut along the middle part of the perforation and electroplated on the end surface electrodes in the process of manufacturing the floating fuse type surface mount fuse of the present invention.

Detailed ways

The structure and manufacturing method of the surface mount fuse of the present invention will be further described below in conjunction with the accompanying drawings.

In Fig. 1, a floating fuse type surface mount fuse includes an insulator 1 with an inner cavity, a fuse 10, a side end electrode 5, and an end face electrode 6, and the insulator 1 has a stacked first cover plate 2 and the second cover plate 3, the two ends of the outer surfaces of the first cover plate 2 and the second cover plate 3 are provided with side terminal electrodes 5, the first cover plate 2 and the second cover plate 3 are made of insulating materials, and the first cover plate 2 and the second cover plate 3 are made of insulating materials. Both the first cover plate 2 and the second cover plate 3 can use a circuit board substrate, and electrode materials such as copper foil can be adhered on the substrate to form side terminal electrodes 5, or a circuit board with electrode materials attached to the surface can be used to remove the electrode material by corrosion. Part of the electrode material on the circuit board is removed, and the corroded circuit board is the first cover plate 2 or the second cover plate 3 provided with side terminal electrodes 5, and the inner sides of the first cover plate 2 and the second cover plate 3 are opposite Both are provided with grooves 4, as shown in Figure 3, the grooves 4 of the first cover plate 2 and the second cover plate 3 are closed to form an inner cavity, and the middle part of the fuse 10 is suspended between the first cover plate 2 and the second cover plate 2. In the inner cavity between the two cover plates 3, both ends of the fuse 10 protrude from the two ends of the insulator 1. The middle large groove is opposite to the small groove on the edge of the groove, and the small groove connects the large groove and the outside world, so that when the middle part of the fuse 10 is suspended in the middle large groove, the fuse 10 passes through the small groove, so that both ends protrude from the insulator. 1 outside of both ends. When the first cover plate 2 and the second cover plate 3 are superimposed, they are fixed by adhesive, and the fuse 10 is also fixed in the small groove by adhesive, so that the fuse is fixed and sandwiched between the first cover plate 2 and the second cover plate 3 between. In addition to setting the fuse in the small groove of the second cover, there are other arrangements. For example, the groove of the first cover is set to include a large middle groove and small grooves on both sides, and the fuse is placed in the first cover. In the small groove, it can also realize that the fuse is clamped between the first cover plate and the second cover plate, or the grooves of the first cover plate and the second cover plate are all set to include a large groove in the middle and small grooves on both sides. In this way, when the first cover plate and the second cover plate are stacked, the large grooves and small grooves of the first cover plate and the second cover plate are closed together, and the fuse passes through the closed small groove to the outside of the insulator. And suspended in the large groove that closes up.

Both ends of the fuse 10 exposed outside the insulator 1 are bent, and the bent ends of the fuse are arranged close to the corresponding end faces of the insulator 1, and the two ends of the insulator 1 are provided with end face electrodes 6, and the end face electrodes 6 of the corresponding ends are 6 is electrically connected to the side electrode 5, and the end electrode 6 covers the curved ends of the fuse 10, as shown in Figure 1-3, which increases the contact area between the end electrode 6 and the fuse. When subjected to cold and heat shocks, even if there is a difference in expansion and contraction between the fuse, the end electrode and the insulator, resulting in no contact between the fuse 10 and the end electrode 6, as long as the end of the fuse 10 is in contact with the end electrode 6, it can be The connection between the fuse 10 and the end electrode 6 is made, thereby ensuring the reliability of the connection between the fuse 10 and the end electrode 6 .

When the fuse is welded on the PCB, since the two ends of the outer surfaces of the first cover plate 2 and the second cover plate 3 are provided with side terminal electrodes 5, the insulator 1 can be placed upright like this (that is, the second cover plate 3 is located Below the first cover plate 2) or upside down (that is, the first cover plate 2 is located below the second cover plate 3) for welding and fixing, both can realize that the PCB board is in phase with the fuse 10 through the side terminal electrode 5 and the end surface electrode 6 For electrical connection, of course, in other embodiments, side terminal electrodes can also be provided only at both ends of the outer surface of the first cover plate or the second cover plate. In FIG. 3 , the outer surface on which the side terminal electrodes 5 are set is opposite to the inner surface on which the groove 4 is provided.

In order to improve the solderability of the fuse on the PCB, it is necessary to increase the electrode material coverage area of the end electrode. In Figures 1 and 2, the end electrode 6 covers the entire end surface of the insulator 1, which facilitates soldering. , Minimize the phenomenon of welding failure, especially for larger surface mount fuses, where it is difficult to climb tin on the thicker end face, the end face electrode 6 is set to cover the entire end face, which significantly enhances the welding strength and reliability.

In Fig. 1, both ends of the insulator 1 have a central concave surface and two side surfaces connected to the central concave surface, and the central concave surface extends from the outer surface of the first cover plate 2 opposite to the inner surface to the second cover plate 3 and the inner surface. On the outer surface opposite to the side, the curved end of the fuse 10 is located in the corresponding intermediate concave surface and is placed close to the concave surface. Concave electrode 8 , planar electrode 7 covering both side surfaces connected to concave electrode 8 , and fuse covering electrode 9 covering the curved end of fuse 10 . By increasing the coverage area of the end electrode 8, it is convenient to climb tin and solder.

In order to improve production efficiency, the floating fuse type surface mount fuse is prepared in batches. The preparation method includes the following steps: (1) preparing two substrates 11 and fuses 12 that will form the first cover 2 and the second cover 3 , The side electrode pattern is formed on the side of at least one substrate 11. In FIG. 4, the up-and-down direction of the observer is defined as the longitudinal direction, and the left-right direction is defined as the transverse direction. The longitudinal direction here corresponds to a single fuse that is subsequently processed. The width direction of the device, the transverse direction corresponds to the length direction of a single fuse, and the electrode pattern of the side end adopts a plurality of parallel electrode strips 14 extending in the longitudinal direction, and the electrode strips 14 are arranged. Adhere electrode materials such as copper foil, or remove part of the electrode materials by etching the circuit board with electrode materials, to form electrode strips 14 . Groove arrays are formed on the sides of the two substrates 11, and through-hole arrays are formed on the sides of the two substrates 11. As shown in FIG. 4, the order of processing the groove arrays and the through-hole arrays is not sequential. It is feasible to form the side terminal electrode pattern on only one substrate or on two substrates at the same time. Corresponding to the subsequent processing of a single fuse, it can only be placed and welded in one direction, or it can be welded upside down, same as above. As mentioned above, on the substrate 11 having the side terminal electrode pattern and the groove array at the same time, the side terminal electrode pattern and the groove array are arranged on opposite sides, and the perforation 13 passes through the side terminal electrode pattern, that is, through the electrode strip 14; (2) The two substrates 11 are stacked and bonded, and the fuse 12 is clamped in the groove 4 between the two substrates 11 by bonding. When the substrates 11 are stacked, the corresponding The grooves 4 are closed together to form a cavity array, and the corresponding perforations 13 on the two substrates 11 are in communication with each other. Part of the fuse 12 is suspended in the cavity, and some parts are exposed in the perforations 13, as shown in FIG. 5 As shown, the fuse 12 exposed in the perforation 13 forms the exposed end of a single fuse that is subsequently processed. In order to ensure that the perforations 13 of the two substrates 11 are aligned without deviation, in the perforation array processing, the two The substrates are stacked and formed by stamping, drilling and other mechanical processing methods; (3) cutting the two stacked and bonded substrates 11 along the middle part of each perforation, that is, along the longitudinal direction in Figure 4, and cutting out the first The end faces of the first cover plate 2 and the second cover plate 3, and cut off the fuse 12, the electrode strip 14 has also been cut accordingly, as shown in Figure 6, the end faces of the first cover plate 2 and the second cover plate 3 There is a central concave surface formed by a perforation 13, and two side surfaces connected to the central concave surface. The two ends of the cut-off fuse 10 are exposed outside the corresponding central concave surfaces of the first cover plate 2 and the second cover plate 3. The above-mentioned Cutting is carried out inside the two substrates 11 that are stacked and bonded, without cutting to the edge of at least one end of the substrates, as shown in Figure 4, which ensures that the subsequent processing technology can be performed on the entire substrate, that is, batch processing, Cutting can be formed by mechanical cutting, laser cutting and other methods; (4) bend the exposed ends of the fuse 10, close to the corresponding middle concave surface of the first cover 2 or the second cover 3, and bend the ends of the fuse 10 It can be formed by mechanical stamping or high-pressure air blowing; (5) electroplating on the entire end faces of the first cover plate 2 and the second cover plate 3 and the curved end of the fuse 10 to form the end face electrode 6 to ensure that the end face electrode 6 is covered Hold the middle concave surface of the first cover plate 2 and the second cover plate 3, the side surfaces on both sides and the curved end of the fuse, and the end electrode 6 is electrically connected with the side end electrode 5. Figure 6 shows that during electroplating, the cut The electrode strip 14 is also electroplated with a coating. In the actual production process, the side electrode 5 will be formed only when multilayer electroplating is carried out on the electrode strip 14. Similarly, the multilayer coating will form the end electrode 6 (in each accompanying drawing). does not explicitly draw multiple layers of plating). Due to the cutting and the end of the fuse 10 being bent close to the middle concave surface before the electroplating, the end electrode 6 formed after the activation electroplating covers the end surfaces of the entire first cover plate 2 and the second cover plate 3, covering the fuse. The curved end of the wire 10 realizes the stable connection between the end electrode 6 and the end of the fuse 10, and maximizes the coverage area of the end electrode 6 to improve the weldability of the fuse; (6) according to the air The array of cavities, that is, the transverse direction shown in FIG. 4 is correspondingly cut, that is, a single fuse is formed.

To sum up, in the floating fuse type surface mount fuse of the present invention, when the end of the fuse is bent close to the end face of the insulator, the end electrode covering the end face of the insulator also covers the curved end of the fuse, increasing the distance between the end electrode and the end face of the insulator. The contact area at the end of the fuse ensures the reliability of the electrical connection, and the end face electrode is set to cover the entire end face of the insulator, thereby improving the weldability of the fuse. Through the corresponding preparation method, the surface mount fuse can be quickly and easily Mass production, high production efficiency.

Claims (10)

1. A floating fuse type surface mount fuse, comprising An insulator with an inner cavity, the insulator has a first cover plate and a second cover plate stacked on top of each other, grooves are opened on the opposite inner sides of the first cover plate and the second cover plate, and the first cover plate and the second cover plate are provided with grooves. The grooves of the cover plate and the second cover plate are closed to form the inner cavity; Side terminal electrodes, the two ends of the outer surface of at least one of the first cover plate and the second cover plate are provided with the side terminal electrodes; a fuse, the fuse is sandwiched between the first cover plate and the second cover plate, and the middle part of the fuse is suspended in the inner cavity, and both ends of the fuse are protruding beyond the end faces of said insulator; End face electrodes, the end face electrodes are provided on both ends of the insulator, and the corresponding end face electrodes are electrically connected to the side end electrodes; It is characterized in that: both ends of the fuse exposed outside the insulator are bent, and the bent ends of the fuse are arranged close to the corresponding end faces of the insulator, and the electrodes on the end cover the fuse The curved ends of the wire. 2 . The floating fuse type surface mount fuse according to claim 1 , wherein the end face electrode covers the entire end face of the insulator. 3 . 3. The floating fuse type surface mount fuse according to claim 2, characterized in that: both ends of the insulator have a central concave surface, and two side surfaces connected to the central concave surface, the central concave surface Extending from the outer surface of the first cover plate opposite to the inner surface to the outer surface of the second cover plate opposite to the inner surface, the bent ends of the fuses are located in the corresponding middle In the concave surface and arranged close to the concave surface, the end electrode covers the middle concave surface, the two side surfaces and the curved end of the fuse. 4. The floating fuse type surface mount fuse according to claim 1, characterized in that: on the first cover plate and the second cover plate respectively, the two ends of the outer surface opposite to the inner surface The side end electrodes are provided, and the side end electrodes on corresponding ends of the first cover plate and the second cover plate are electrically connected to the end face electrodes. 5. The floating fuse type surface mount fuse according to claim 1, characterized in that: the inner surfaces of the first cover plate and the second cover plate are bonded and fixed, and the fuse is fixed by bonding Between the opposite inner surfaces of the first cover plate and the second cover plate. 6. The method for preparing the floating fuse type surface mount fuse as claimed in claim 3, comprises the following steps: (1) Prepare two substrates and fuses that will form the first cover and the second cover, process and form side electrode patterns on the side of at least one of the substrates, and process on the sides of the two substrates respectively A groove array is formed, and a perforation array is formed on the side surfaces of the two substrates respectively. On the substrate having both the side electrode pattern and the groove array, the side electrode pattern and the groove arrays are disposed on opposite sides, and the through holes pass through the side terminal electrode patterns; (2) The two substrates are stacked and bonded, the fuse is sandwiched between the two substrates, and bonded on the opposite sides of the two substrates to ensure that the two substrates correspond to each other. The grooves of the two substrates are closed together to form a cavity array, and the corresponding through holes on the two substrates are directly connected to each other, and part of the fuse is suspended in the cavity, and part of the fuse is exposed in the through hole; It is characterized by: (3) Cutting the two superimposed and bonded substrates along the middle part of each perforation, cutting out the end faces of the first cover plate and the second cover plate, and cutting off the fuse, the first cover plate and the end faces of the second cover plate have the central concave surface formed by the perforation, and the two side surfaces connected to the central concave surface, and the two ends of the cut fuse are exposed on the first cover plate and the second cover plate. the outside of the corresponding central concave surface of the cover plate; (4) Bend the exposed ends of the fuse so as to be close to the corresponding middle concave surface of the first cover or the second cover; (5) Electroplating on the entire end faces of the first cover plate and the second cover plate and the curved end of the fuse to form end face electrodes, ensuring that the end face electrodes cover the first cover plate and the second cover plate The central concave surface of the cover plate, the side surfaces on both sides and the curved end of the fuse, and the end electrode is electrically connected to the side electrode; (6) Carry out corresponding cutting according to the cavity array, that is, form a single fuse. 7. The method according to claim 6, characterized in that: the bending at both ends of the fuse is formed by mechanical stamping or high-pressure air blowing. 8. The method according to claim 6, characterized in that the cutting in the above step (3) is carried out inside the two overlapping and bonded substrates, without cutting to the edge of at least one end of the substrates . 9 . The method according to claim 6 , wherein, in the perforation array processing in the above step (1), two substrates are stacked to punch or drill holes. 10 . 10. The method according to claim 6, characterized in that: the side surfaces of the two substrates are processed to form the side electrode patterns, and the circuit board with the electrode material on the surface is removed by etching part of the electrode material to form A substrate provided with the side terminal electrode pattern.

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