Surface-mounted thick film fuse and preparation method thereof

Abstract

The invention discloses a surface-mounted thick film fuse and a preparation method thereof, the surface-mounted thick film fuse sequentially comprises a ceramic substrate, a multi-layer composite layer, an arc extinguishing layer and a metal electrode, the multi-layer composite layer is formed by sequentially and alternately laminating x fuse link layers and x-1 insulating layers, x is an integer greater than 1, and x is an integer greater than 1. And the insulating layer is an aluminum nitride film which is formed on the surface of the fuse link layer by adopting a physical vapor deposition or chemical vapor deposition method and has the thickness of 100nm-5mu m. According to the invention, the AlN films with micron-scale and nano-scale thicknesses are used for cutting the fuse link layer with a certain film thickness into a plurality of fuse link layers, and the thickness of a single fuse link layer is relatively thin, so that the electric arc can be effectively inhibited; meanwhile, the high-thermal-conductivity AlN thin film can improve the temperature consistency of the fuse link layers, so that the breaking time of the fuse can be effectively shortened. Therefore, the surface-mounted thick film fuse is small in size, high in overall reliability, high in breaking capacity and suitable for large-current and large-voltage working conditions.

Description

Technical Field

[0001] The present invention belongs to the field of circuit protection, specifically relates to the field of fuses, and particularly relates to a surface-mounted thick film fuse and a preparation method thereof. Background Art

[0002] As a kind of circuit protection component, a fuse is usually connected in series in the protected circuit. When a short circuit occurs in the circuit or the current exceeds the specified value and lasts for a period of time, the fuse will cut off the circuit by its own safe fusing, thereby avoiding damage to the circuit and equipment, and preventing dangerous accidents such as fires. As a kind of reliable electronic component, fuses are widely used in electronic products and electrical equipment in civil, aerospace, military and other fields.

[0003] As an important type of fuse, the surface-mounted thick film fuse has the advantages of high reliability, stable electrical performance, small volume and light weight, and is widely used in various fields. However, in the working scenarios of high voltage and large current, the existing surface-mounted thick film fuses face some technical problems: to meet the working requirements of high voltage and large current, the fuse body layer of the fuse must have a certain thickness, and a larger film thickness is likely to generate a larger arc during the fusing process. The existence of this larger arc will not only affect the normal fusing action of the fuse, but in more serious cases, it may even cause the dangerous situation of the fuse exploding, which directly limits the improvement of the rated voltage and rated current of the surface-mounted thick film fuse, making its current rated voltage and rated current usually at a relatively low level and difficult to meet the scenarios with the demand for high voltage and large current circuit protection.

[0004] Therefore, there is an urgent need for a surface-mounted thick film fuse and a preparation method thereof to solve the deficiencies of the existing technology. Summary of the Invention

[0005] To solve the contradiction between increasing the rated voltage and reducing the arc, the inventors of the present application designed multiple relatively thin fuse body layers in the surface-mounted thick film fuse. These fuse body layers are spaced apart by a glass insulating layer and are connected to the electrodes in parallel. The main advantage of this design is that the current entering the fuse is divided into smaller branches and flows through different fuse body layers respectively. Since the thickness of a single fuse body layer is relatively thin and the current passing through it is relatively small, the arc generated during fusing can be suppressed to a certain extent. However, the surface-mounted thick film fuse with this structure also faces some challenges. First, when the fuse with this structure is powered on, the temperature consistency of different fuse body layers is relatively poor. This is because: First, in the actual preparation of the fuse, it is very difficult for the existing process to make the thicknesses of all fuse body layers exactly the same, and there are more or less certain differences in the thicknesses of each layer, resulting in deviations in the resistance values of each layer and inconsistent heat generation when powered on; Second, different fuse body layers are located in different spatial positions and are adjacent to different components. For example, the fuse body layer at the bottom is usually in contact with the ceramic substrate, while the fuse body layer at the top is usually in contact with the arc extinguishing layer, and the thermal conductivities of different components are also different. This difference leads to different heat exchanges between each fuse body layer and the surrounding environment, resulting in temperature differences between each layer; Third, the fuse body layers are spaced apart by an insulating layer, which is usually made of glass paste by printing and then high-temperature sintering. However, the thermal conductivity of the obtained glass insulating layer is relatively low (about ~1 W / mK), and the films obtained by the existing printing technology are relatively thick, which is not conducive to the heat conduction between the fuse body layers, thus exacerbating the temperature difference between each layer. Since the fusing of the fuse is achieved by the melting and breaking of the fuse body layer inside it when the temperature rises to the set value, for a fuse containing multiple fuse body layers, the temperature difference between each layer will inevitably prolong the breaking time, thus affecting the breaking ability of the device. In addition, the glass softening temperature usually starts to soften at 500-600 °C. Therefore, the obtained glass insulating layer is easily affected by the subsequent sintering process and will undergo processes such as softening, melting, and solidification again due to the subsequent sintering process, easily damaging the adjacent fuse body layers, thereby damaging the device structure. At the same time, it also makes it difficult to increase the number of fuse body layers, thus affecting the preparation of high-performance devices. In addition, it is also relatively difficult to obtain a glass insulating layer with a thickness of less than 10 μm in the prior art. When multiple insulating layers need to be provided inside the fuse, it will result in a relatively thick device thickness, making it difficult for the device size to meet the development trend and requirements of the miniaturization and micro-miniaturization of electronic devices.

[0006] In view of the above problems, the object of the present invention is to provide a surface-mounted thick film fuse and its preparation method. The surface-mounted thick film fuse has a small size, high overall reliability, strong breaking ability, and is suitable for working conditions of large current and large voltage.

[0007] To achieve the above object, a first aspect of the present invention provides a surface-mounted thick film fuse, which sequentially includes a ceramic substrate, a multi-layer composite layer, an arc extinguishing layer, and metal electrodes. The multi-layer composite layer is formed by sequentially laminating x fuse body layers and x - 1 insulating layers alternately, where x is an integer greater than 1. The insulating layer is an aluminum nitride film with a thickness of 100 nm to 5 μm formed on the surface of the fuse body layer by physical vapor deposition or chemical vapor deposition.

[0008] The surface-mounted thick film fuse provided by the present invention has the following beneficial effects:

[0009] 1. The surface-mounted thick film fuse of the present invention has multiple fuse body layers, and the fuse body layers are separated by an aluminum nitride (AlN) film. The thermal conductivity of AlN is usually between 100 and 320 W / mK, which is much higher than that of glass (about 1 W / mK). Therefore, sandwiching the aluminum nitride (AlN) film between the fuse body layers helps to achieve efficient heat conduction between the fuse body layers, thereby improving the temperature consistency of each fuse body layer. At the same time, the insulating layer of the present invention is prepared by physical vapor deposition or chemical vapor deposition method, so the thickness of the insulating layer can be easily controlled and an AlN film with a micron-level or nano-level thickness can be obtained. Therefore, the film thickness of the insulating layer is much lower than that of the glass layer prepared by the printing method, thus further optimizing the heat conduction path and further reducing the temperature difference between each fuse body layer. Therefore, the temperature of each fuse body layer in the surface-mounted thick film fuse provided by the present invention tends to be consistent, thus effectively shortening the breaking time of the fuse and improving the breaking capacity, and is suitable for working conditions of large current and large voltage.

[0010] 2. The AlN film of the present invention has extremely high thermal stability, can maintain its structural and chemical stability in an environment up to 2200 °C, has strong thermal shock resistance, can withstand repeated sintering and remain stable, and does not cause damage to adjacent fuse body layers, which is more conducive to the preparation of fuses with multiple fuse body layers, and also improves the overall reliability of the surface-mounted thick film fuse.

[0011] 3. The thickness of the AlN film of the present invention is only 100 nm to 5 μm, which saves more space and can effectively reduce the device size. Therefore, the surface-mounted thick film fuse of the present invention has a small size, meeting the development trend and requirements of miniaturization and microminiaturization of electronic devices.

[0012] Further, the thickness of the fuse body layer of the present invention is 1 to 50 μm.

[0013] Further, the ceramic substrate of the present invention has a flat cuboid structure.

[0014] Further, the ceramic substrate of the present invention is an Al2O3 ceramic substrate.

[0015] Further, the thickness of the insulating layer of the present invention is 200 nm to 2 μm.

[0016] Accordingly, a second aspect of the present invention provides a method for manufacturing a surface-mounted thick film fuse, the steps including:

[0017] (1) Preparing a multi-layer composite layer

[0018] A multi-layer composite layer is formed by alternately laminating a fuse body layer and an insulating layer on the surface of a ceramic substrate in sequence; both the side of the multi-layer composite layer away from the ceramic substrate and the side close to the ceramic substrate are fuse body layers;

[0019] The preparation of the fuse body layer includes: printing a resistance paste on the ceramic substrate or the formed insulating layer and then sintering;

[0020] The preparation of the insulating layer includes: forming an aluminum nitride film on the surface of the formed fuse body layer by using a magnetron sputtering method;

[0021] (2) Preparing an arc extinguishing layer

[0022] An arc extinguishing layer is obtained by printing a glass paste on the surface of the multi-layer composite layer away from the ceramic substrate and then sintering;

[0023] (3) Preparing metal electrodes

[0024] The ceramic substrate obtained after step (2) is subjected to end face metallization treatment to form metal electrodes.

[0025] Further, the preparation of the fuse body layer of the present invention includes: printing a resistance paste on the ceramic substrate or the formed fuse body layer by using a screen printing method, and the resistance paste is at least one of a gold paste and a silver paste.

[0026] Further, the sintering temperature in step (1) of the present invention is 600 - 900 °C.

[0027] Further, the sintering temperature in step (2) of the present invention is 500 - 800 °C. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the surface-mounted thick film fuse of Example 1.

[0029] Figure 2 It is a schematic structural diagram of the surface-mounted thick film fuse in Example 1 after removing the arc extinguishing layer and the metal electrodes.

[0030] Figure 3 It is a process flow chart of the manufacturing method of the surface-mounted thick film fuse in Example 1. Detailed Embodiments

[0031] When the existing thick film fuse reaches the melting temperature, the internal fuse layer is relatively thick, which easily leads to poor disconnection. In addition, the current flowing through is large, so the arcing phenomenon is serious. Based on this, the present invention provides a surface-mount thick film fuse, which includes a ceramic substrate, a multi-layer composite layer, an arc extinguishing layer, and a metal electrode in sequence. The multi-layer composite layer is formed by alternating x fuse layers and x-1 insulating layers in sequence, where x is an integer greater than 1, and the insulating layer is an aluminum nitride film with a thickness of 100nm to 5μm formed on the surface of the fuse layer by physical vapor deposition or chemical vapor deposition. The present invention uses an AlN film with a micron-level or nanometer-level thickness to "cut" a fuse layer with a certain film thickness into multiple thinner fuse layers. When the device is working, the current flowing through each fuse layer is small, and the thickness of a single fuse layer is thin, so the arc energy can be effectively suppressed. At the same time, the highly thermally conductive AlN insulating layer can achieve efficient heat conduction between the fuse layers and improve the consistency of the temperature of each layer, thereby effectively shortening the breaking time of the fuse and improving the breaking capacity of the device. In addition, the thickness of the AlN film provided by the present invention can be easily controlled, and it is easy to obtain an extremely thin insulating layer, which is not only conducive to further optimizing the heat conduction path and improving the heat conduction efficiency, but also conducive to reducing the thickness of the device, and is more suitable for the preparation of miniaturized and micro-miniaturized fuses. In addition, unlike the glass insulating layer, which is easy to melt and deform at a lower temperature, the AlN insulating layer provided by the present invention has strong resistance to thermal shock, is less affected by the subsequent sintering process, can withstand repeated sintering while maintaining stable morphology and composition, and does not damage the adjacent fuse layer, so it is more conducive to the preparation of a surface-mounted thick film fuse with multiple fuse layers. Therefore, when the surface-mounted thick film fuse provided by the present invention is applied to high current and high voltage working conditions, it has good breaking capacity, high overall reliability, and small device size, which meets the current development trend and requirements of miniaturized and micro-miniaturized electronic devices.

[0032] Specifically, the thickness of the fuse layer of the present invention is 1-50 μm. More specifically, the thickness of the fuse layer may be, but is not limited to, 1 μm, 8 μm, 20 μm, 30 μm, 40 μm, or 50 μm.

[0033] Specifically, the ceramic substrate of the present invention is a flat rectangular parallelepiped structure. More specifically, the ceramic substrate of the present invention is an Al2O3 ceramic substrate; preferably, the ceramic substrate is 96% Al2O3 ceramic, with a thermal conductivity of 25 W / mK and a thermal expansion coefficient of 7.1×10 -6 / K, dielectric strength greater than 15kV / mm, surface roughness of 0.20~0.75μm.

[0034] Specifically, the thickness of the insulating layer of the present invention is 200 nm to 2 μm. More specifically, the thickness of the insulating layer can be, but is not limited to, 200 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, 2000 nm. Preferably, the thickness of the insulating layer is 200 nm to 1 μm.

[0035] Specifically, x can be 2, 3, 4, 5, 6, 7, 8, etc. It should be noted that the value of x can be specifically selected according to actual needs, that is, the present invention can prepare fuses with different numbers of fuse body layers and insulating layers according to actual needs. For example, the number of fuse body layers and insulating layers can be increased or decreased according to device size, rated voltage, rated current, etc.

[0036] Correspondingly, the second aspect of the present invention provides a method for manufacturing a surface-mounted thick film fuse, and the steps include:

[0037] (1) Prepare a multi-layer composite layer

[0038] A multi-layer composite layer is formed by alternately laminating a fuse body layer and an insulating layer on the surface of a ceramic substrate in sequence; both the side of the multi-layer composite layer away from the ceramic substrate and the side close to the ceramic substrate are fuse body layers;

[0039] The preparation of the fuse body layer includes: printing a resistance paste on the ceramic substrate or the formed insulating layer and then sintering;

[0040] The preparation of the insulating layer includes: forming an aluminum nitride film on the surface of the formed fuse body layer by means of magnetron sputtering;

[0041] (2) Prepare an arc extinguishing layer

[0042] An arc extinguishing layer is obtained by printing a glass paste on the surface of the multi-layer composite layer away from the ceramic substrate and then sintering;

[0043] (3) Prepare metal electrodes

[0044] The ceramic substrate obtained after step (2) is subjected to end face metallization treatment to form metal electrodes.

[0045] Furthermore, the preparation of the fuse body layer of the present invention includes: printing a resistance paste on the ceramic substrate or the formed fuse body layer by means of screen printing, and the resistance paste is at least one of a gold paste and a silver paste. Specifically, the main components of the silver paste include silver powder, binder, solvent, dispersant, leveling agent, antioxidant, stabilizer, etc., and it can be purchased through commercial channels; of course, the gold paste can also be purchased through commercial channels.

[0046] Furthermore, the main components of the glass paste of the present invention are glass powder, resin, organic solvent, etc., and it can be purchased through commercial channels.

[0047] Further, in step (1) of the present invention, the sintering temperature is 600 to 900 °C. Specifically, the sintering temperature can be, but is not limited to, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C.

[0048] Further, in step (2) of the present invention, the sintering temperature is 500 to 800 °C. Specifically, the sintering temperature can be, but is not limited to, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C.

[0049] Further, in step (3) of the present invention, the metal electrode is obtained by a conventional end face metallization treatment technology. Specifically, the material of the metal electrode is a silver layer plated with nickel on the surface.

[0050] To better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings.

[0051] The resist paste in Examples 1 to 4 is silver paste, which is purchased from Suzhou Xinwei High-Tech Materials Co., Ltd.; the glass paste in Examples 1 to 4 is purchased from Shenzhen Saiya Electronic Paste Co., Ltd.

[0052] The ceramic substrates in Examples 1 to 4 are in the shape of a flat cuboid structure. The ceramic substrate is 96% Al2O3 ceramic, with a thermal conductivity of 25 W / mK, a thermal expansion coefficient of 7.1×10 -6 / K, a dielectric strength greater than 15 kV / mm, and a surface roughness of 0.20 to 0.75 μm.

[0053] Example 1

[0054] Please refer to Figures 1 to 2 , this embodiment provides a surface-mounted thick film fuse 100, which sequentially includes a ceramic substrate 1, a multi-layer composite layer, an arc extinguishing layer 7, and a metal electrode 8. The multi-layer composite layer is formed by sequentially and alternately laminating three fuse layers (the first fuse layer 2, the second fuse layer 4, and the third fuse layer 6) and two insulating layers (the first insulating layer 3 and the second insulating layer 5). The insulating layer is a 300-nm-thick aluminum nitride film formed on the surface of the fuse layer by magnetron sputtering.

[0055] Please refer to Figure 3 , this embodiment provides the preparation method of the above-mentioned surface-mounted thick film fuse, and the steps include:

[0056] (1) Prepare the multi-layer composite layer

[0057] Screen-print the resist paste on the surface of the ceramic substrate 1 and then sinter at 880 °C to form the first fuse layer 2 with a thickness of 15 μm;

[0058] The first insulating layer 3 is formed by preparing an AlN film with a thickness of 300 nm on the first fuse layer 2 by means of magnetron sputtering;

[0059] The resist paste is screen-printed on the first insulating layer 3 and then sintered at 880 °C to form the second fuse layer 4 with a thickness of 15 μm;

[0060] The second insulating layer 5 is formed by preparing an AlN film with a thickness of 300 nm on the second fuse layer 4 by means of magnetron sputtering;

[0061] The resist paste is screen-printed on the second insulating layer 5 and then sintered at 880 °C to form the third fuse layer 6 with a thickness of 15 μm;

[0062] The conditions of the above magnetron sputtering method are as follows: the substrate temperature is room temperature; the base vacuum degree is 1×10 -4 Pa; the sputtering gas and the reaction gas are argon and nitrogen respectively, and the purities are both 99.99%; the target is an Al target with a purity of 99.999%; the distance from the target to the substrate is 12 cm; the total pressure of the working gas is 1 Pa; the flow ratio of argon to nitrogen is 2:1; the sputtering power is 200 - 300 W;

[0063] (2) Preparation of the arc extinguishing layer

[0064] The glass paste is screen-printed on the surface of the multi-layer composite layer far from the ceramic substrate by means of screen printing, and then sintered at 700 °C to obtain the arc extinguishing layer 7;

[0065] (3) Preparation of the metal electrode

[0066] The ceramic substrate obtained after step (2) is subjected to end face metallization treatment to form the metal electrode 8, wherein the material of the metal electrode 8 is a silver layer plated with nickel on the surface.

[0067] Example 2

[0068] This example provides a surface-mounted thick film fuse, which sequentially includes a ceramic substrate, a multi-layer composite layer, an arc extinguishing layer, and a metal electrode. The multi-layer composite layer is formed by sequentially and alternately laminating three fuse layers (the first fuse layer, the second fuse layer, and the third fuse layer) and two insulating layers (the first insulating layer and the second insulating layer). The insulating layer is a aluminum nitride film with a thickness of 500 nm formed on the surface of the fuse layer by means of magnetron sputtering.

[0069] This example provides the preparation method of the above surface-mounted thick film fuse, and the steps include:

[0070] (1) Preparation of the multi-layer composite layer

[0071] Screen-print the resist paste on the surface of the ceramic substrate and then sinter it at 850 °C to form a first fuse layer with a thickness of 12 μm;

[0072] Use the magnetron sputtering method to deposit an AlN film with a thickness of 500 nm on the first fuse layer to form a first insulating layer;

[0073] Screen-print the resist paste on the first insulating layer and then sinter it at 850 °C to form a second fuse layer with a thickness of 12 μm;

[0074] Use the magnetron sputtering method to deposit an AlN film with a thickness of 500 nm on the second fuse layer to form a second insulating layer;

[0075] Screen-print the resist paste on the second insulating layer and then sinter it at 850 °C to form a third fuse layer with a thickness of 12 μm;

[0076] The conditions of the above magnetron sputtering method are as follows: the substrate temperature is room temperature; the base vacuum is 1×10 -4 Pa; the sputtering gas and the reaction gas are argon and nitrogen respectively, and the purity of both is 99.99%; the target is an Al target with a purity of 99.999%; the distance from the target to the substrate is 12 cm; the total pressure of the working gas is 1 Pa; the flow ratio of argon to nitrogen is 2:1; the sputtering power is 200 - 300 W;

[0077] (2) Prepare the arc extinguishing layer

[0078] Use the screen-printing method to print the glass paste on the surface of the multi-layer composite layer away from the ceramic substrate, and then sinter it at 800 °C to obtain the arc extinguishing layer;

[0079] (3) Prepare the metal electrodes

[0080] Perform end face metallization on the ceramic substrate obtained in step (2) to form metal electrodes, where the material of the metal electrodes is a silver layer plated with nickel on the surface.

[0081] Example 3

[0082] This example provides a surface-mounted thick film fuse, which sequentially includes a ceramic substrate, a multi-layer composite layer, an arc extinguishing layer, and metal electrodes. The multi-layer composite layer is sequentially and alternately stacked by three fuse layers (the first fuse layer, the second fuse layer, and the third fuse layer) and two insulating layers (the first insulating layer and the second insulating layer). The insulating layer is an aluminum nitride film with a thickness of 800 nm formed on the surface of the fuse layer by the magnetron sputtering method.

[0083] This example provides a preparation method for the above surface-mounted thick film fuse, and the steps include:

[0084] (1) Prepare the multi-layer composite layer

[0085] Screen-print the resist paste on the surface of the ceramic substrate and then sinter it at 800 °C to form a first fuse layer with a thickness of 20 μm;

[0086] Use the magnetron sputtering method to prepare an AlN film with a thickness of 800 nm on the first fuse layer to form a first insulating layer;

[0087] Screen-print the resist paste on the first insulating layer and then sinter it at 800 °C to form a second fuse layer with a thickness of 20 μm;

[0088] Use the magnetron sputtering method to prepare an AlN film with a thickness of 800 nm on the second fuse layer to form a second insulating layer;

[0089] Screen-print the resist paste on the second insulating layer and then sinter it at 800 °C to form a third fuse layer with a thickness of 20 μm;

[0090] The conditions of the above magnetron sputtering method are: the substrate temperature is room temperature; the base vacuum is 1×10 -4 Pa; the sputtering gas and the reaction gas are argon and nitrogen respectively, and the purity of both is 99.99%; the target is an Al target with a purity of 99.999%; the distance from the target to the substrate is 12 cm; the total pressure of the working gas is 1 Pa; the flow ratio of argon to nitrogen is 2:1; the sputtering power is 200 - 300 W;

[0091] (2) Prepare the arc extinguishing layer

[0092] Use the screen-printing method to print the glass paste on the surface of the multi-layer composite layer away from the ceramic substrate, and then sinter it at 600 °C to obtain the arc extinguishing layer;

[0093] (3) Prepare the metal electrode

[0094] Perform end-face metallization on the ceramic substrate obtained after step (2) to form a metal electrode, where the material of the metal electrode is a silver layer plated with nickel on the surface.

[0095] Example 4

[0096] Example 4 is basically the same as Example 1, and the only difference between the two is that the multi-layer composite layer is formed by sequentially and alternately laminating four fuse layers (the first fuse layer, the second fuse layer, the third fuse layer, and the fourth fuse layer) and three insulating layers (the first insulating layer, the second insulating layer, and the third insulating layer);

[0097] Accordingly, the preparation method of the surface-mounted thick film fuse of Example 4 is basically the same as that of Example 1, and the difference between the two is only that: in step (1) of Example 4, an AlN film with a thickness of 300 nm is prepared on the third fuse layer by magnetron sputtering to form a third insulating layer; a resist paste is screen-printed on the third insulating layer and then sintered at 880 °C to form a fourth fuse layer with a thickness of 8 μm.

[0098] The arc suppression performance of the surface-mounted thick film fuses of Examples 1 to 4 was tested. The test instruments were a short-circuit test platform (DL10KV-100), a megohmmeter (AR3127), a DC programmable power supply (IT6932A), and a 6 1 / 2-digit multimeter (34401A); the test environment temperature was 20.7 °C and the humidity was 46% RH. The arc suppression performance test results of the surface-mounted thick film fuses of Examples 1 to 4 at 3.5 times the rated current are shown in Table 1.

[0099] Table 1 Arc suppression performance test results of the fuses

[0100] Group Arc ignition time (ms) Example 1 153 Example 2 251 Example 3 246 Example 4 334

[0101] As can be seen from Table 1, the surface-mounted thick film fuses of Examples 1 to 4 have good arc extinguishing effects. This shows that the present invention uses AlN thin films with micron-level and nano-level thicknesses to "cut" a fuse layer with a certain film thickness into multiple thinner fuse layers. When the device is working, the current flowing through each fuse layer is small, and the thickness of a single fuse layer is thin, so the arc can be effectively suppressed. At the same time, the highly thermally conductive AlN insulating layer can achieve efficient heat conduction between the fuse layers, improve the temperature consistency of each layer, and thus can effectively shorten the breaking time of the fuse and improve the breaking capacity of the device.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to only those listed in the embodiments. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A surface mount thick film fuse, characterized in that: The invention comprises a ceramic substrate, a multi-layer composite layer, an arc extinguishing layer and a metal electrode in sequence. The multi-layer composite layer is formed by alternating x fuse layers and x-1 insulating layers in sequence, wherein x is an integer greater than 1, and the insulating layer is an aluminum nitride film with a thickness of 100nm to 5μm formed on the surface of the fuse layer by physical vapor deposition or chemical vapor deposition.

2. The surface mount thick film fuse according to claim 1, characterized in that: The thickness of the fuse layer is 1-50 μm.

3. The surface mount thick film fuse according to claim 1, characterized in that: The ceramic substrate is in a flat rectangular parallelepiped structure.

4. The surface mount thick film fuse according to claim 1, characterized in that: The ceramic substrate is an Al2O3 ceramic substrate.

5. The surface mount thick film fuse according to claim 1, characterized in that: The thickness of the insulating layer is 200 nm to 2 μm.

6. A method for preparing a surface mount thick film fuse according to any one of claims 1 to 5, characterized in that the steps include: (1) Preparation of multi-layer composite layers On the surface of the ceramic substrate, fuse layers and insulating layers are alternately stacked in sequence to form a multi-layer composite layer; The side of the multi-layer composite layer away from the ceramic substrate and the side close to the ceramic substrate are both the fuse layer; The preparation of the fuse layer includes: printing a resist slurry on the ceramic substrate or the formed insulating layer and then sintering; The preparation of the insulating layer comprises: forming an aluminum nitride film on the surface of the formed fuse layer by a magnetron sputtering method; (2) Preparation of arc extinguishing layer Printing glass paste on the surface of the multi-layer composite layer away from the ceramic substrate and then sintering to obtain an arc-extinguishing layer; (3) Preparation of metal electrodes The ceramic substrate obtained after step (2) is subjected to end surface metallization treatment to form metal electrodes.

7. The method for preparing a surface mount thick film fuse according to claim 6, characterized in that: The preparation of the fuse layer includes: printing a resist slurry on the ceramic substrate or the formed fuse layer by a screen printing method, wherein the resist slurry is at least one of a gold paste and a silver paste.

8. The method for preparing a surface mount thick film fuse according to claim 6, characterized in that: The sintering temperature in step (1) is 600-900°C.

9. The method for preparing a surface mount thick film fuse according to claim 6, characterized in that: The sintering temperature in step (2) is 500-800°C.

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