Surface-mounted tubular fuse structure and preparation method thereof

Abstract

The invention discloses a surface-mounted tubular fuse structure and a preparation method thereof, and belongs to the technical field of overcurrent protection electronic components. The fuse structure comprises an insulating tube, a fuse body, an arc extinguishing body, an inner copper cap, an outer copper cap and a sealing colloid. The fuse body is arranged in the insulating tube body, the arc extinguishing body is filled in the insulating tube body and wraps the fuse body, the inner copper cap and the outer copper cap form a combined electrode cap, the sealing colloid is filled between the end part of the insulating tube body and a circular inner cap of the combined electrode cap, and the circular inner copper cap and the end part of the insulating tube body realize preliminary airtight packaging through welding or interference fit. And the sealing colloid is combined for secondary reinforced sealing, and the square outer copper cap provides a flat surface-mounted welding surface. The preparation method comprises the process steps of inner copper cap pressing, threading and spot welding, arc extinguishing material potting, outer copper cap assembling, sealant potting and the like. The problems that a traditional tubular fuse is large in installation space, has reliability hidden danger and is limited in high breaking capacity are solved. The fuse is widely applied to the technical field of tubular fuses.

Description

Technical Field

[0001] This invention belongs to the field of overcurrent protection electronic components technology, and more specifically to the field of fuse technology. In particular, it relates to a surface-mount tubular fuse structure and its preparation method. Background Technology

[0002] A fuse is a component connected in series in an electronic circuit to provide overcurrent protection. When the circuit current exceeds a specified value and persists for a certain period of time, the fuse element itself generates heat that exceeds the heat dissipated, causing the fuse element to reach its melting point and thus melt, achieving the purpose of overcurrent protection.

[0003] Tubular fuses are widely used for overcurrent protection in various electronic and electrical equipment due to their high breaking capacity and stable performance. Traditional tubular fuse encapsulation forms are mainly divided into end cap type, lead wire type, and bolt mounting type.

[0004] End-cap type fuses have cylindrical metal caps at both ends of the ceramic tube, which need to be inserted into a dedicated fuse holder during use. Although this structure provides good contact, the fuse holder itself occupies a significant amount of vertical and horizontal space on the PCB board (the fuse holder space needs to be reserved in other structural components inside the chassis or on the chassis panel before the fuse is installed), which cannot meet the development needs of miniaturization and high-density integration in modern electronic products.

[0005] Lead-wire fuses, on the other hand, have metal wires leading out from both end caps. Installation requires drilling holes in the PCB board, bending the leads, threading them through the holes, and then cutting and soldering them. This installation method is cumbersome, inefficient, and the leads are at risk of breakage due to repeated bending or vibration, affecting product reliability. Furthermore, the leads themselves and the required mounting holes occupy valuable board space.

[0006] Bolted fuses have bolt holes on their end caps, requiring additional nuts to secure them to the PCB board or fuse holder. This mounting method not only requires extra fasteners, increasing material costs and assembly steps, but the nuts, bolts, and the required installation space are also very large, severely contradicting the trend of miniaturization and lightweighting of electronic devices. A common problem with all these traditional types is their large footprint during installation.

[0007] In existing technologies, there are several solutions dedicated to miniaturizing and surface-mounting fuses. For example, Chinese utility model patent CN216818260U proposes a "miniature fuse with an integral end cap," where the end cap is an integrally formed L-shaped structure riveted to a ceramic shell with an interference fit, aiming to save space and avoid welding that would increase contact resistance. Chinese utility model patent CN203192732U relates to a "surface-mount tubular fuse," which improves withstand voltage and breaking capacity by combining perforated metal sheets at both ends of the tubular shell with end electrodes.

[0008] Therefore, existing tubular fuses have certain shortcomings in terms of space occupation and ease of installation, while existing surface-mount fuse solutions have certain shortcomings in terms of high breaking capacity. There is an urgent need for a new surface-mount structure that can inherit the advantages of high rated breaking capacity of traditional tubular fuses, while achieving small size (solving the problem of the space occupied by the installation structure of existing traditional tubular fuses, resulting in low space utilization) and high reliability.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] The technical problem to be solved by this invention is to address the issues of large installation space, potential reliability risks, and limited high breaking capacity of traditional tubular fuses.

[0011] The inventive concept of this invention is to transform the existing product mounting structure into a surface-mount structure. A compact, easy-to-install, and highly reliable surface-mount miniature tubular fuse is designed. Space is saved through SMT (Surface Mount Technology) installation, and the application of multiple fuse wires in parallel, arc-extinguishing material filling, and end-sealing adhesive comprehensively improves the product's electrical performance, breaking capacity, environmental sealing, and mechanical reliability.

[0012] Therefore, the present invention provides a surface-mount tubular fuse structure, such as... Figure 1 As shown. Includes: 1. Insulating tube; 2. Fusible element; 3. Arc extinguishing element; 4. Inner copper cap; 5. Outer copper cap; 6. Sealing colloid.

[0013] The fusible element is a fuse wire housed within an insulating tube, and can be a single fuse wire or multiple fuse wires connected in parallel. The use of multiple fuse wires in parallel design effectively distributes the current, achieving a higher rated current value within the same total volume, or precisely controls the fusing characteristics through a combination of different fuse wire materials.

[0014] The arc-extinguishing body is an arc-extinguishing material filler that fills the insulating tube and covers the fuse wire, used for rapid arc extinguishing and improving breaking capacity.

[0015] The sealing colloid is a sealing filler that fills the space between the end of the insulating tube and the inner circular cap of the composite electrode cap. It is used to enhance the sealing effect of the end encapsulation, effectively prevent the intrusion of external moisture and corrosive gases, and improve the long-term reliability of the product.

[0016] The inner and outer copper caps form a composite electrode cap: consisting of a circular inner cap and a square outer cap. The circular inner cap is initially hermetically sealed to the end of the insulating tube through welding or interference fit, and then further reinforced with a sealing compound. The square outer cap provides a flat surface for surface mounting.

[0017] (1) Pressing the inner copper caps: Press the two brass circular inner caps into the insulating tube from both ends with an interference fit to form the main frame.

[0018] (2) Wire threading and spot welding: The fusible wire designed according to the requirements of the fusion characteristics is threaded through the inner cavity of the insulating tube, and the two ends of the fusible wire are welded to the outer end faces of the two circular inner caps respectively using a precision spot welding machine to form an electrical connection.

[0019] (3) Filling arc extinguishing material: Using special filling equipment, the arc extinguishing material is tightly and evenly filled into the insulating tube under vibration environment until the entire inside of the insulating tube is filled.

[0020] (4) Assembly of outer copper cap: The square outer copper cap is assembled with the round inner copper cap by interference fit to form a complete composite electrode cap.

[0021] (5) Potting sealant: Finally, using precision dispensing equipment, the sealant is potted in a ring along the joint between the end of the insulating tube and the circular inner copper cap. After curing, the sealant forms an elastic sealing layer.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: Flexible and adjustable electrical performance: The product adopts a single or multiple fuse design, which enables it to flexibly adapt to different rated voltage, rated current and fusing characteristics requirements, thus expanding its application range.

[0023] Ultimate environmental sealing: Based on traditional welding / sintering sealing, a secondary sealant with high-temperature resistant sealing colloid is added, forming a double sealing barrier, which greatly improves the product's moisture resistance and corrosion resistance, and extends its service life.

[0024] High electrical and mechanical performance: Arc-extinguishing material ensures high breaking capacity; multiple fuses and internal filling structure enhance vibration and shock resistance; sealing colloid further enhances the mechanical strength of the end structure.

[0025] This invention can be widely applied in the field of tubular fuse technology. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the fuse chip structure of the present invention.

[0027] Figure 2 This is a schematic diagram showing the appearance of the sample S2 product prepared according to the present invention.

[0028] In the diagram: 1 is the insulating tube, 2 is the molten metal, 3 is the arc extinguishing body, 4 is the inner copper cap, 5 is the outer copper cap, and 6 is the sealing colloid. Detailed Implementation

[0029] like Figure 1-2 As shown, the specific implementation method of the surface-mount tubular fuse structure and its manufacturing method is as follows: The insulating tube is a ceramic tube.

[0030] The fuse is made of pure silver, pure copper, silver-plated copper, or other alloy materials.

[0031] The arc-extinguishing material is an inorganic mixed arc-extinguishing material mainly composed of 30μm-300μm quartz sand, or an arc-extinguishing material mainly composed of 30μm-300μm quartz sand mixed with inorganic and organic binders.

[0032] The sealant is a high-temperature resistant (≥200℃), acid and alkali resistant, and highly insulating colloid.

[0033] The copper cap inside is made of brass, with a 2μm-50μm nickel plating.

[0034] The outer copper cap is made of brass or copper, and is plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer.

[0035] Example 1: Fabrication of a 500V / 30A All-Solid-State Surface-Modified Tubular Fuse (1) Pressing the inner copper caps: Press the two brass circular inner caps with the ceramic tube from both ends with an interference fit to form the main frame.

[0036] (2) Wire threading and spot welding: The sheet-shaped pure silver fusion wire designed according to the fusing characteristics is threaded through the inner cavity of the ceramic tube, and the two ends of the fusion wire are welded to the outer end faces of the two circular inner caps respectively using a precision spot welding machine to form an electrical connection.

[0037] (3) Filling arc extinguishing material: Using a special filling equipment, under vibration environment, inorganic arc extinguishing material mainly composed of 30μm-300μm quartz sand or arc extinguishing material mainly composed of 30μm-300μm quartz sand mixed with inorganic and organic binders is tightly and evenly filled into the ceramic tube until the inside of the ceramic tube is completely filled.

[0038] (4) Assembly of outer copper cap: The square outer cap of brass plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer is assembled with the round inner cap by interference fit to form a complete composite electrode cap.

[0039] (5) Potting sealant: Using precision dispensing equipment, the electronic sealant is potted in a ring along the joint between the end of the ceramic tube and the round inner cap. After curing, the sealant forms an elastic sealing layer.

[0040] The fusing times of the 500V / 30A surface-mount tubular fuse (referred to as sample S1) prepared according to the above method at 300% and 1000% rated current are shown in Table 1 below.

[0041] Table 1. Blowout time of sample S1 (30A) at 300% and 1000% rated current.

[0042] Example 2: Fabrication of a 1500V / 50A All-Solid-State Surface-Modified Tubular Fuse (1) Pressing the inner copper caps: Press the two brass circular inner caps with the ceramic tube from both ends with an interference fit to form the main frame.

[0043] (2) Wire threading and spot welding: The sheet-shaped pure silver fusion wire designed according to the fusing characteristics is threaded through the inner cavity of the ceramic tube, and the two ends of the fusion wire are welded to the outer end faces of the two circular inner caps respectively using a precision spot welding machine to form an electrical connection.

[0044] (3) Assembly of one end of the outer copper cap: Assemble the brass square outer cap plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer onto the inner copper cap at one end.

[0045] (4) Filling arc extinguishing material: First, fill most of the 30μm-300μm quartz sand, then inject a certain amount of water glass solution to mix with the remaining quartz sand and penetrate into all the pores. Water glass acts as a binder and arc inhibitor.

[0046] (5) Curing: After the arc-quenching material is filled, the product is transferred to a vacuum curing oven using a special fixture for curing, so that the water glass and quartz sand form a dense and compact solid structure.

[0047] (6) Assembly of the outer copper cap at both ends: Assemble the square brass cap with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer onto the inner copper cap at the other end.

[0048] (7) Potting sealant: Using precision dispensing equipment, electronic sealant is potted in a ring along the joint between the end of the ceramic tube and the round inner cap. After curing, the sealant forms an elastic sealing layer, forming the final structure of the product.

[0049] The fusing times of the 1500V / 50A surface-mount tubular fuse (referred to as sample S2) prepared according to the above are shown in Table 2 below at 400% and 1000% of the rated current.

[0050] Table 2. Blow-off time of sample S2 (50A) at 1000% rated current.

[0051] Finally, it should be noted that the above embodiments are merely examples for clear illustration. This invention includes, but is not limited to, the above embodiments, and it is neither necessary nor possible to exhaustively describe all possible implementations. Those skilled in the art can make other variations or modifications based on the above description. All implementation schemes that meet the requirements of this invention are within the protection scope of this invention.

Claims

1. A surface-mount tubular fuse structure, characterized in that, include: Insulating tube, molten metal, arc extinguisher, inner copper cap, outer copper cap, sealing colloid; The melt is a fuse wire, which is disposed inside an insulating tube and can be a single fuse wire or multiple fuse wires connected in parallel; The arc-extinguishing body is an arc-extinguishing material filler, which is filled into an insulating tube and covered with a fuse. The sealing colloid is a sealing filler that fills the space between the end of the insulating tube and the circular inner cap of the composite electrode cap. The inner copper cap and the outer copper cap form a composite electrode cap: the inner copper cap is round and the outer copper cap is square. The round inner cap and the end of the insulating tube are initially hermetically sealed by welding or interference fit, and then reinforced with a sealing colloid for secondary sealing. The square outer copper cap provides a flat surface for surface bonding.

2. The surface-mount tubular fuse structure as described in claim 1, characterized in that: The insulating tube is a ceramic tube.

3. The surface-mount tubular fuse structure as described in claim 1, characterized in that: The fuse is made of pure silver, pure copper, silver-plated copper, or other alloy materials.

4. The surface-mount tubular fuse structure as described in claim 1, characterized in that: The arc-extinguishing material is an inorganic mixed arc-extinguishing material mainly composed of 30μm-300μm quartz sand, or an arc-extinguishing material mainly composed of 30μm-300μm quartz sand mixed with inorganic and organic binders.

5. The surface-mount tubular fuse structure as described in claim 1, characterized in that: The sealant is a high-temperature resistant (≥200℃), acid and alkali resistant, and highly insulating colloid.

6. The surface-mount tubular fuse structure as described in claim 1, characterized in that: The copper cap inside is made of brass, with a 2μm-50μm nickel plating.

7. The surface-mount tubular fuse structure as described in claim 1, characterized in that: The outer copper cap is made of brass or copper, and is plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer.

8. The method for fabricating a surface-mounted tubular fuse structure as described in claim 1, characterized in that, The preparation method is as follows: (1) Inner copper cap pressing: The two brass circular inner caps are pressed into the insulating tube from both ends by interference fit to form the main body frame; (2) Wire threading and spot welding: The fusible wire designed according to the fusing characteristics is threaded through the inner cavity of the insulating tube, and the two ends of the fusible wire are welded to the outer end faces of the two circular inner caps respectively using a precision spot welding machine to form an electrical connection; (3) Filling arc-extinguishing material: Using special filling equipment, the arc-extinguishing material is tightly and evenly filled into the insulating tube under vibration environment until the inside of the insulating tube is completely filled; (4) Assembly of outer copper cap: The square outer copper cap is assembled with the round inner copper cap by interference fit to form a complete composite electrode cap; (5) Potting sealant: Using precision dispensing equipment, the sealant is potted in a ring along the joint between the end of the insulating tube and the circular inner copper cap. After curing, the sealant forms an elastic sealing layer.

9. The method for preparing a surface-mounted tubular fuse structure as described in claim 8, characterized in that: The fabrication method for a 500V / 30A all-solid-state surface-mount tubular fuse is as follows: (1) Pressing the inner copper caps: Press the two brass circular inner caps into the ceramic tube from both ends with an interference fit to form the main frame; (2) Wire threading and spot welding: The sheet-shaped pure silver fusion wire designed according to the fusing characteristics is threaded through the inner cavity of the ceramic tube, and the two ends of the fusion wire are welded to the outer end faces of the two circular inner caps respectively using a precision spot welding machine to form an electrical connection; (3) Filling arc extinguishing material: Using a special filling equipment, under vibration environment, inorganic arc extinguishing material mainly composed of 30μm-300μm quartz sand or arc extinguishing material mainly composed of 30μm-300μm quartz sand mixed with inorganic and organic binders is tightly and evenly filled into the ceramic tube until the inside of the ceramic tube is completely filled. (4) Assembly of outer copper cap: The brass square outer cap plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer is assembled with the round inner cap by interference fit to form a complete composite electrode cap; (5) Potting sealant: Using precision dispensing equipment, the electronic sealant is potted in a ring along the joint between the end of the ceramic tube and the round inner cap. After curing, the sealant forms an elastic sealing layer.

10. The method for preparing a surface-mounted tubular fuse structure as described in claim 8, characterized in that: The fabrication method for a 1500V / 50A all-solid-state surface-mount tubular fuse is as follows: (1) Pressing the inner copper caps: Press the two brass circular inner caps into the ceramic tube from both ends with an interference fit to form the main frame; (2) Wire threading and spot welding: The sheet-shaped pure silver fusion wire designed according to the fusing characteristics is threaded through the inner cavity of the ceramic tube, and the two ends of the fusion wire are welded to the outer end faces of the two circular inner caps respectively using a precision spot welding machine to form an electrical connection; (3) Assembly of one end of the outer copper cap: Assemble the brass square outer cap plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer onto the inner copper cap at one end; (4) Filling arc-extinguishing material: First, fill most of the 30μm-300μm quartz sand, then inject a certain amount of water glass solution to mix it with the remaining quartz sand and penetrate into all the pores. Water glass is used as a binder and arc inhibitor. (5) Curing: After the arc-quenching material is filled, the product is transferred to a vacuum curing oven using a special fixture for curing, so that the water glass and quartz sand form a dense and compact solid structure. (6) Assembly of the outer copper cap at both ends: Assemble the square brass cap plated with a 2μm-50μm nickel layer and a 3μm-50μm tin layer or tin-lead layer onto the inner copper cap at the other end; (7) Potting sealant: Using precision dispensing equipment, electronic sealant is potted in a ring along the joint between the end of the ceramic tube and the round inner cap. After curing, the sealant forms an elastic sealing layer, forming the final structure of the product.

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