A surface mount fuse

Abstract

The present invention provides a surface mounted fuse, comprising an insulating shell provided with an end electrode, a fuse body arranged inside the insulating shell, and a side electrode for electrically connecting the end electrode to the fuse body, wherein the connection positions of the side electrode and the second side walls on both sides are respectively a first connection point and a second connection point, a cross section through the middle of the surface mounted fuse is a reference plane, the position at which the side electrode is farthest from the reference plane is a distal end of the side electrode, and the distance between the distal end of the side electrode and the reference plane is respectively greater than the distance between the first connection point and the reference plane and the distance between the second connection point and the reference plane; the side electrode portion located between the first connection point and the distal end of the side electrode and the side electrode portion located between the second connection point and the distal end of the side electrode will generate an inward pulling force on the side electrode, thereby at least partially offsetting the thrust on the side electrode when the insulating shell is thermally expanded, so that the side electrode is not easily peeled off from the insulating shell when the insulating shell is cold-shrunk.

Description

Technical Field

[0001] The invention relates to the field of electrical protection elements, and in particular provides a surface mounted fuse with a novel side electrode. Background Art

[0002] In the prior art, a fuse such as that disclosed in CN107610988A is Figure 1 As shown, it includes an insulating shell 1, an end electrode 2, and a side electrode 3 connecting two end electrodes and a fuse, and the two ends of the side electrode 3 are respectively connected to the end electrode 2. In this design, since the expansion coefficients of the insulating shell 1 and the side electrode 3 made of metal plating are different, the expansion coefficient of the insulating shell 1 is usually several times or even more than ten times that of the metal. When the customer uses a surface mount fuse, it needs to be soldered to the PCB board through high-temperature soldering technology such as wave soldering or reflow soldering. In addition, if the product is subjected to alternating high and low temperature conditions after assembly by the customer (such as multiple assembly of various parts during SMT, rework or operation under harsh conditions), since the side electrode is only connected to the two end electrodes in the length direction, and no additional connection force is provided on the two sides in the longer width direction, the thermal expansion and contraction at this time will easily cause the side electrode to peel off from the insulating shell, resulting in the electrical connection between the fuse and the side electrode being disconnected, causing a safety hazard.

[0003] CN201721665677.2 discloses a fuse having two end caps, which cover the five sides of the insulating shell, realize the firm fixation of the metal coating as the side terminal electrode, ensure the stable electrical connection between the melt and the terminal electrode, and enhance the working stability of the fuse. However, this kind of setting structure and production process are complicated and the cost is high. Summary of the invention

[0004] The object of the present invention is to provide at least a new type of surface mount fuse.

[0005] In order to achieve the above object, the present invention provides a surface mount fuse, comprising:

[0006] An insulating shell, wherein both ends of the bottom wall of the insulating shell and both ends of the top wall of the insulating shell are respectively provided with terminal electrodes, and the insulating shell further comprises two first side walls respectively located at both ends in the length direction and two second side walls respectively located at both ends in the width direction;

[0007] A fuse body, the fuse body being arranged inside the insulating housing;

[0008] Side electrodes, two of the side electrodes are respectively arranged on the two first side walls, and the side electrodes on each side are respectively electrically connected to the fuse body at a corresponding position and the end electrodes located on the bottom wall of the insulating housing and the top wall of the insulating housing;

[0009] The connection positions between the side electrode and the second side walls on both sides are respectively a first connection point and a second connection point, a cross-section through the middle of the surface mount fuse is a reference plane, the part of the side electrode farthest from the reference plane is a distal end of the side electrode, the distance between the distal end of the side electrode and the reference plane is greater than the distance between the first connection point and the reference plane, and the distance between the distal end of the side electrode and the reference plane is greater than the distance between the second connection point and the reference plane.

[0010] The insulating shell is a hexahedron, including a top wall and a bottom wall located at the top and bottom, respectively, two first side walls located at the front and the back, respectively, and second side walls located at the left and the right, respectively, wherein the top wall, the bottom wall, and the second side wall are all planes, the two second side walls are parallel to each other, and the top wall and the bottom wall are parallel to each other, which is convenient for processing. The reference plane is a reference plane that is perpendicular to the plane where the top wall, the bottom wall, and the second side wall are located. The reference plane passes through the middle of the length direction of the surface mount fuse, which is convenient for explaining the setting characteristics of the side electrode.

[0011] The distance between the distal end of the side electrode and the reference plane is greater than the distance between the first connection and the second connection and the reference plane, which will make the plane parallel to the reference plane passing through the first connection and the plane parallel to the reference plane passing through the distal end of the side electrode parallel to each other, and the plane parallel to the reference plane passing through the second connection and the plane parallel to the reference plane passing through the distal end of the side electrode parallel to each other. When the insulating shell expands due to heat, it will push the side electrode outward. At this time, the side electrode portion located between the first connection and the distal end of the side electrode and the side electrode portion located between the second connection and the distal end of the side electrode will generate an inward pulling force on the side electrode, thereby at least partially offsetting the thrust of the insulating shell on the side electrode, so that the side electrode is not easily peeled off from the insulating shell when the insulating shell shrinks, ensuring a stable electrical connection between the melt and the end electrode, and enhancing the working stability of the fuse. Preferably, the first connection and the second connection are respectively a straight line perpendicular to the top wall, which can form a complete connection with the side electrode.

[0012] In some embodiments, the distal end of the side electrode is located in a plane parallel to the reference plane, and the first connection point is connected to the distal end of the side electrode through a first arc surface.

[0013] In some embodiments, the second connection point is connected to the distal end of the side electrode via a second arc surface.

[0014] In some embodiments, the first arc surface and / or the second arc surface is / are circular arc surfaces.

[0015] In some embodiments, the first curved surface and / or the second curved surface is / are an inwardly concave curved surface.

[0016] In some embodiments, the first arc surface and / or the second arc surface is an inwardly concave arc surface, and the curvature of the arc surface is π / 2, which is convenient for large-scale production.

[0017] In some embodiments, the distal end of the side electrode includes two distal end surfaces located in the same plane, and the two distal end surfaces are connected by a middle concave surface.

[0018] In some embodiments, both ends of the middle concave surface in the length direction are respectively connected to the end electrodes at corresponding positions.

[0019] In some embodiments, the side electrode is a convex arc surface that protrudes in a direction away from the reference surface.

[0020] In some embodiments, the convex arc surface is a circular arc.

[0021] The beneficial effects of the present invention are as follows: the surface mounted fuse of the present invention.

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the three-dimensional structure of a surface mount fuse in the prior art;

[0024] Figure 2 It is a perspective schematic diagram of the three-dimensional structure of the surface mount fuse of the first embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of the three-dimensional structure of the surface mount fuse of the first embodiment of the present invention;

[0026] Figure 4 It is a partial cross-sectional schematic diagram of the surface mount fuse of the first embodiment of the present invention;

[0027] Figure 5 It is a partial view of a surface mount fuse in the prior art after multiple reflow soldering;

[0028] Figure 6 It is a local X-Ray image of a surface mount fuse in the prior art after multiple reflow soldering;

[0029] Figure 7 It is a partial view of the surface mount fuse of the first embodiment of the present invention after multiple reflow soldering;

[0030] Figure 8 This is a partial X-Ray image of the surface mount fuse of Example 1 of the present invention after multiple reflow soldering;

[0031] Fig. 9It is a schematic diagram of the three-dimensional structure of the surface mount fuse of the second embodiment of the present invention;

[0032] Fig.10 It is a perspective schematic diagram of the three-dimensional structure of the surface mount fuse of the second embodiment of the present invention;

[0033] Fig.11 It is a perspective diagram of the three-dimensional structure of the surface mount fuse of the third embodiment of the present invention.

[0034] Among them, 1-insulating shell; 11-top wall; 12-second side wall; 2-end electrode; 3-side electrode; 31-distal end surface; 4-arc surface; 41-first connection point; 5-middle concave surface; F1-thrust force; F2-pull force. DETAILED DESCRIPTION

[0035] The present invention can be further understood by the specific examples of the present invention given below, but they are not intended to limit the present invention.

[0036] Embodiment 1

[0037] like Figure 2-4 As shown, this embodiment provides a surface mount fuse, including an insulating shell 1, an end electrode 2, a side electrode 3 and a fuse body (not shown in the figure) arranged inside the insulating shell 1, and a plurality of end electrodes 2 are respectively arranged at both ends of the bottom wall of the insulating shell 1 and at both ends of the top wall 11 of the insulating shell 1. The insulating shell 1 also includes two first side walls (not shown in the figure, covered by the side electrodes 3) respectively located at both ends in the length direction and two second side walls 12 respectively located at both ends in the width direction. In this embodiment, the two first side walls are respectively located in two planes parallel to each other, the two second side walls 12 are respectively located in two planes parallel to each other, and the top wall 11 and the bottom wall are respectively located in two planes parallel to each other.

[0038] The two side electrodes 3 are respectively arranged on the two first side walls, for example, by directly coating the metal on the first side walls by spraying, electroplating, etc. The upper and lower ends of the side electrode 3 on each side are respectively electrically connected to the terminal electrode 2 located on the bottom wall of the insulating housing 1 and the top wall 11 of the insulating housing 1, and at the same time, the two ends of the fuse body are respectively electrically connected to the side electrodes 3 on both sides, so as to realize the electrical connection between the fuse body and the terminal electrode 2.

[0039] In this embodiment, Figure 2As shown, the connection positions of the side electrode 3 and the second side walls 12 on both sides are respectively the first connection 41 and the second connection (not shown in the figure). In this embodiment, the first connection 41 and the second connection are respectively a straight line perpendicular to the top wall, and the upper ends and lower sections of the first connection 41 and the second connection are respectively electrically connected to the terminal electrodes at the corresponding positions on the top wall and the bottom wall. The cross section through the middle of the surface mount fuse is the reference plane, which is a reference plane that is perpendicular to the plane where the top wall 11, the bottom wall and the second side wall 12 are located. The reference plane passes through the middle of the length direction of the surface mount fuse, which is convenient for explaining the setting characteristics of the side electrode 3.

[0040] The part of the side electrode that is farthest from the reference surface is the distal end of the side electrode. In this embodiment, the distal end of the side electrode is a complete plane, which is parallel to the plane where the first side wall is located and the reference surface. The first connection 41 is connected to the distal end of the side electrode through the first arc surface 4, and the second connection is connected to the distal end of the side electrode through the second arc surface. In this embodiment, the upper and lower ends of the first arc surface and the second arc surface are respectively connected to the end electrodes on the bottom wall and the top wall at the corresponding positions, so that a continuous and uninterrupted metal layer is formed from the first connection 41 → the first arc surface 4 → the distal end of the side electrode → the second arc surface → the second connection, and the upper and lower parts of the metal layer are respectively connected to the end electrodes at the corresponding positions. At this time, the distance between the distal end of the side electrode and the reference surface is greater than the distance between the first connection 41 and the reference surface, and the distance between the distal end of the side electrode and the reference surface is greater than the distance between the second connection and the reference surface.

[0041] The first arc surface 41 and the second arc surface can be irregular arc surfaces or circular arc surfaces. In this embodiment, the first arc surface 41 and the second arc surface are both inwardly concave circular arc surfaces, and the curvature of the circular arc surface is π / 2. In large-scale array production, circular holes are cut at corresponding positions, and corresponding circular arc surfaces can be cut for four final products at the same time, thereby improving the efficiency of large-scale production.

[0042] In this embodiment, Figure 4As shown, the first connection 41 and the second connection are symmetrically arranged, so that the first connection 41 and the second connection are located in the same plane parallel to the reference plane. At this time, the distance between the distal end of the side electrode and the reference plane is greater than the distance between the first connection 41 and the second connection and the reference plane. When the surface mount fuse undergoes reflow soldering, the insulating shell 1 expands due to heat, which will generate an outward thrust in the direction shown by F1 on the side electrode 3. At this time, the side electrode portion (i.e., the first arc surface 4) located between the first connection 41 and the distal end of the side electrode and the side electrode portion (i.e., the second arc surface 4) located between the second connection and the distal end of the side electrode will generate an oblique pulling force as shown by F2 on the side electrode, which will inevitably generate an inward pulling force component, thereby at least partially offsetting the thrust F1 of the insulating shell on the side electrode, so that the side electrode 3 is not easily peeled off from the insulating shell 1 when the insulating shell 1 shrinks, ensuring a stable electrical connection between the melt and the end electrode 2, and enhancing the working stability of the fuse. Figure 5-6 The figure shows that the end portion of the surface mount fuse in the prior art has obvious cracks after thermal expansion and contraction. Figure 7-8 The broken end portion of the surface mount fuse of this embodiment is shown, and no cracks appear after thermal expansion and contraction.

[0043] In order to further verify the stability of this product, the end electrode 2 of the surface mount fuse in the prior art and the end electrode 2 of the fuse in this embodiment are removed respectively, and then the lead is welded to the side electrode 3, and the lead is connected to the tensile machine to pull the lead until the side electrode 3 is pulled away from the insulating shell 1. The experimental results are shown in the following table. The experimental results show that the traditional surface mount fuse requires a tensile force of about 3N to break, while the surface mount fuse in this embodiment requires a tensile force of about 8N, indicating that the connection strength between the side electrode 3 and the insulating shell 1 is significantly improved.

[0044]

[0045] Embodiment 2

[0046] like Figure 9-10 As shown, this embodiment provides another arrangement of the side electrode 3. The difference from the first embodiment is that the distal end of the side electrode includes two distal end surfaces 31 located in the same plane, the two distal end surfaces 31 are connected by an intermediate concave surface 5, and the two ends of the intermediate concave surface 5 in the length direction are respectively connected to the end electrodes 2 at corresponding positions.

[0047] Embodiment 3

[0048] like Fig.11 As shown, this embodiment provides another arrangement of the side electrode 3. The difference from the first embodiment is that the side electrode 3 is a convex arc surface protruding in a direction away from the reference surface, and the arc surface is a circular arc, which is convenient for processing.

[0049] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A surface mount fuse, comprising: An insulating shell, wherein both ends of the bottom wall of the insulating shell and both ends of the top wall of the insulating shell are respectively provided with terminal electrodes, and the insulating shell further comprises two first side walls respectively located at both ends in the length direction and two second side walls respectively located at both ends in the width direction; A fuse body, the fuse body being arranged inside the insulating housing; Side electrodes, two of the side electrodes are respectively arranged on the two first side walls, and the side electrodes on each side are respectively electrically connected to the fuse body at a corresponding position and the terminal electrodes located on the bottom wall of the insulating housing and the top wall of the insulating housing; The connection positions of the side electrode and the second side walls on both sides are respectively a first connection point and a second connection point, a cross section through the middle of the surface mount fuse is a reference plane, and the position at which the side electrode is farthest from the reference plane is a side electrode distal end, characterized in that the distance between the side electrode distal end and the reference plane is greater than the distance between the first connection point and the reference plane, and the distance between the side electrode distal end and the reference plane is greater than the distance between the second connection point and the reference plane; The first connection point is connected to the distal end of the side electrode via a first arc surface; the second connection point is connected to the distal end of the side electrode via a second arc surface; the first arc surface and / or the second arc surface are inwardly concave arc surfaces.

2. The surface mount fuse according to claim 1, characterized in that: The distal end of the side electrode is located in a plane parallel to the reference plane, and the upper and lower ends of the first arc surface and the second arc surface are respectively connected to the end electrodes on the bottom wall and the top wall at corresponding positions.

3. The surface mount fuse according to claim 2, characterized in that: The first arc surface and / or the second arc surface is / are circular arc surfaces.

4. The surface mount fuse according to claim 3, characterized in that: The first arc surface and / or the second arc surface is an inwardly concave arc surface, and the arc angle of the arc surface is π / 2.

5. The surface mount fuse according to claim 2, characterized in that: The distal end of the side electrode includes two distal end surfaces located in the same plane, and the two distal end surfaces are connected by a middle concave surface.

6. The surface mount fuse according to claim 5, characterized in that: Both ends of the middle concave surface in the length direction are respectively connected to the end electrodes at corresponding positions.

7. The surface mount fuse according to claim 1, characterized in that: The side electrode is a convex arc surface that protrudes in a direction away from the reference surface.

8. The surface mount fuse according to claim 7, characterized in that: The convex arc surface is a circular arc.

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