Chip type fuse

Abstract

A chip-type fuse is provided. A fusible body (26) in a plate shape has internal electrodes (28, 30) toward the inside of the center side of a straight line from both ends of the straight line, and a fusible portion (32) integrally formed with the internal electrodes (28, 30) between the internal electrodes (28, 30). The fusible body (26) is housed in a housing (2), and protruding portions (38, 40) protrude from portions of the internal electrodes (28, 30) located at both ends of the straight line. The protruding portions (38, 40) are covered with plating layers (50, 52).

Description

Technical Field

[0001] This invention relates to chip-type fuses, and particularly to the construction of electrodes. Background Technology

[0002] WO1993 / 17442 discloses an example of a chip-type fuse. This chip-type fuse has a substrate consisting of a glass plate with a rectangular parallelepiped shape. A metal thin-film fuse element is formed on the upper surface of the substrate. The fuse element has rectangular electrodes at both ends of the upper surface of the substrate, and a connection narrower than the electrodes is formed between these electrodes. The fuse element is covered by a silicon dioxide inert layer. A rectangular glass film is bonded to the silicon dioxide active layer by an epoxy layer. The electrodes are exposed at both ends of the substrate and the glass film. A plating layer of nickel, chromium, etc., covers both end faces of the substrate and the film, the end of the lower surface of the end face of the substrate, and the end of the upper surface of the film, which is adjacent to the end face of the film. A solder film covers the plating layer. The plating layer electrically connects the solder film and the fuse element. Summary of the Invention

[0003] In the aforementioned chip-type fuse, the electrode integrated with the assembly is exposed on the end face of the assembly and only contacts the plating layer formed on the end face, thus failing to achieve sufficient electrical connection between the plating layer and the electrode.

[0004] The object of the present invention is to obtain sufficient electrical connection between the electrodes located inside the chip fuse and the plating layer formed on the fuse.

[0005] One aspect of the present invention provides a chip fuse having a plate-shaped fusible body. Internal electrodes are disposed at both ends of a straight line within the fusible body. The shape of the internal electrodes can be arbitrary. A fusible portion is formed between these internal electrodes. The fusible portion is integrally formed with the internal electrodes and is thinner than the internal electrodes. The fusible portion can be, for example, a single shape such as a straight line or a curve. The fusible body is housed within a housing. The housing can be of any shape as long as it can accommodate the fusible body. Furthermore, when the chip fuse is to be a surface-mount chip fuse, the housing preferably has at least one flat side. The portions of the internal electrodes located at both ends of the straight line are exposed from the housing. A conductive layer is formed to cover these portions (hereinafter referred to as exposed portions). The conductive layer can be formed either by plating the exposed portions or by applying a conductive coating to the exposed portions. The conductive layer can also extend to other surfaces in the housing beyond the exposed portions. A protrusion projecting outward from the exposed portion is integrally formed on the exposed portion. The protrusion is covered by the conductive layer.

[0006] In this type of chip fuse, within the plate-shaped fusible element, a protrusion extends from an internal electrode integrally formed with the fusible element, and this protrusion is covered by a conductive layer. Therefore, the internal electrode and the conductive layer are fully electrically connected. If the internal electrode and fusible element are formed using a coating technique, it is difficult to form a protrusion extending from the internal electrode.

[0007] In this configuration, the housing may have a recess having concave surfaces that intersect the straight line at both ends. In this case, the conductive layer is formed on the concave surface, and the protrusion protrudes from the concave surface into the recess.

[0008] With this configuration, the protrusion does not protrude from the recess, so the protrusion will not become an obstacle when soldering the chip-type fuse to the printed circuit board.

[0009] Furthermore, the internal electrode can have a recessed surface, at least a portion of which is located within the recess, within the housing. In this case, the protrusion exists between the recessed surface and the concave surface.

[0010] With this configuration, when the fusible element forms a recessed surface, it is also possible to form a portion that becomes a protrusion when the fusible element is disposed within the housing. Therefore, the manufacture of this chip-type fuse becomes easier.

[0011] Furthermore, the protrusions can be made to protrude into the recess from the entire area of ​​the recessed surface when viewed from above. This configuration increases the area of ​​the protrusions, making the electrical connection between the conductive layer and the internal electrodes more reliable.

[0012] In the chip fuse described above, the housing can have at least one plane. In this case, the conductive layer extends onto the plane. With this configuration, the chip fuse becomes a chip fuse suitable for surface mounting.

[0013] In the chip-type fuse described above, the housing may have first and second planes of the same shape, arranged parallel to each other and spaced apart. In this case, the housing has a peripheral surface surrounding the edges of the first and second planes. Furthermore, the protrusion protrudes from the peripheral surface. The housing may, for example, have a cuboid shape, a disc shape, an elliptical shape, or a bowl shape.

[0014] Furthermore, the housing can have a concave surface near both ends of the straight line, which partially connects to the straight line and intersects the first and second planes. In this case, within the housing, the protrusions project from the entire edge of the concave surface when viewed from above, and the plating layer is formed over the entire surface area of ​​the concave surface.

[0015] With this configuration, when the chip-type fuse is used for surface mounting, the electrical connection between the conductive layer and the internal electrodes can be achieved very well. Attached Figure Description

[0016] Figure 1 This is a front longitudinal sectional view of the chip-type fuse according to the first embodiment of the present invention.

[0017] Figure 2 yes Figure 1 A top view of a chip-type fuse.

[0018] Figure 3 yes Figure 1 The left side view of a chip-type fuse.

[0019] Figure 4 yes Figure 1 A top view of the lower housing component of a chip-type fuse.

[0020] Figure 5 yes Figure 1 A top view of the fusible element of a chip-type fuse.

[0021] Figure 6 yes Figure 1 A cross-sectional top view of a chip-type fuse.

[0022] Figure 7 yes Figure 1 A top view of a semi-finished chip-type fuse.

[0023] Figure 8 This is a front longitudinal sectional view of the chip-type fuse according to the second embodiment of the present invention.

[0024] Figure 9 yes Figure 8 A top view of a chip-type fuse.

[0025] Figure 10 yes Figure 8 A cross-sectional top view of a chip-type fuse.

[0026] Figure 11a This is a variation of the fusible element used in the chip-type fuse of the first embodiment.

[0027] Figure 11b This is another variation of the fusible element used in the chip-type fuse of the first embodiment. Detailed Implementation

[0028] The chip-type fuse of the first embodiment of the present invention is as follows: Figures 1 to 3As shown, the device has a housing 2. For example, the housing 2 is formed into a generally rectangular shape made of glass epoxy. The housing 2 has a first surface, such as an upper surface 4, and a second surface, such as a lower surface 6. The upper surface 4 and the lower surface 6 are formed into the same shape, such as a rectangle, and are arranged parallel to each other in an overlapping manner. Between the upper surface 4 and the lower surface 6, a peripheral surface is formed that surrounds the edges of the first and second surfaces. The peripheral surface is formed, for example, by side surfaces 8 and 10 and end surfaces 12 and 14. They are all rectangular. Concave surfaces 16 and 18 are formed on the end surfaces 12 and 14 near the center along the direction of the side surfaces 8 and 10, respectively. The concave surfaces 16 and 18 are formed toward the inside of the housing 2. Specifically, with respect to the concave surfaces 16 and 18, a portion of the center and the vicinity of the end surfaces 12 and 14 is removed, for example, formed into an arc shape, specifically a semi-circle. By forming concave surfaces 16 and 18 respectively, recesses 19 and 21, which are semi-cylindrical spaces, are formed on end faces 12 and 14 respectively. Recess 19 opens in the direction of the upper surface 4, the lower surface 6, and the end face 12, while recess 21 opens in the direction of the upper surface 4, the lower surface 6, and the end face 14. The shell 2 is as follows... Figure 1 As shown, along the central direction of the upper surface 4 and the lower surface 6, the structure is divided into an upper shell component 20 and a lower shell component 22, both of the same shape. A cavity 24 is formed in the center of the interior of the shell 2. The cavity 24 is as follows... Figure 4 The planar shape shown is an elongated hole.

[0029] like Figure 1 As shown, a fusible material 26 is disposed at the mating surface of the upper housing component 20 and the lower housing component 22. The fusible material 26 is as follows... Figure 5 The diagram shows internal electrodes 28 and 30 and a fusible portion 32. Within the fusible body 26, as... Figure 6 As shown, internal electrodes 28 and 30 extend from both ends of a straight line toward the central side of the housing 2. This straight line, for example, has a length equal to the distance between end faces 12 and 14 at their center. Internal electrodes 28 and 30 are formed in a generally rectangular shape with a maximum width equal to the distance between the sides 8 and 10 of the housing 2. A fusible portion 32 lies on the straight line between the inner edges of the internal electrodes 28 and 30 on the central side of the housing 2. The fusible portion 32 is formed as a straight line narrower than the internal electrodes 28 and 30. This fusible portion 32 is located within the cavity 24. The fusible body 26 is a thin metal sheet, such as a copper plate, formed by stamping or etching a thin metal sheet, such as a copper plate. In the fusible body 26, the fusible portion 32 is integrally formed with the internal electrodes 28 and 30.

[0030] like Figure 5As shown, recessed surfaces 34 and 36 are formed on the outer edges of the internal electrodes 28 and 30. These recessed surfaces 34 and 36 are formed, for example, in an arc shape, specifically a semi-circular shape, and are recessed towards the central side of the fusible portion 32. Figure 6 As shown, a fusible element 26 is arranged on the lower housing component 22 such that the end faces 12 and 14 align with the outer edges of the internal electrodes 28 and 30. In this arrangement, the centers of the recessed surfaces 34 and 36 lie on the aforementioned straight line. The recessed surfaces 16 and 18 and 34 and 36 are concentrically arranged. The radii of the recessed surfaces 34 and 36 are formed to be smaller than the radii of the recessed surfaces 16 and 18. As a result, the recessed surfaces 34 and 36 protrude further outward than the recessed surfaces 16 and 18. The portion from the recessed surfaces 34 and 36 to the recessed surfaces 16 and 18 is referred to as the protrusions 38 and 40. These protrusions 38 and 40 are as follows: Figure 5 As shown in the top view from the recessed surfaces 34 and 36, the entire area protrudes horizontally into the recesses 19 and 21. If the protrusions 38 and 40 were not present, portions of the internal electrodes 28 and 30 located on the recessed surfaces 16 and 18 would be exposed in the recesses 19 and 21.

[0031] In this chip-type fuse, initially, a lower housing component 22, an upper housing component 22, and a fusible element 26 are prepared. For example... Figure 6 As shown, a fusible element 26 is disposed on the lower housing component 22. The lower housing component is as follows... Figure 7 The upper housing component 20 is shown. The upper housing component 20 and the lower housing component 22 are bonded together.

[0032] like Figure 1 As shown, conductive layers, such as external electrodes 42 and 44, are formed at one end of the upper surface 4 and lower surface 6 of the housing 2. These external electrodes 42 and 44 extend from the end face 12 of the housing 2 beyond the concave surface 16, and have holes at positions corresponding to the concave surface 16, with widths corresponding to the lengths of the side surfaces 8 to 10 of the housing 2. Similarly, conductive layers, such as external electrodes 46 and 48, are also formed at the other end of the upper surface 4 and lower surface 6 of the housing 2. These external electrodes 42, 44, 46, and 48 are, for example, made of copper film.

[0033] A conductive layer, such as plating layer 50, is formed over the entire concave surface 16 such that the protrusion 38 is entirely contained within the plating layer 50. A plating layer 52 is formed over the entire concave surface 18, also internally containing the protrusion 40. These plating layers 50 and 52 extend to the upper surface 4 and lower surface 6 of the housing 2. Plating layer 50 also covers the entire areas of external electrodes 42 and 44, and plating layer 52 covers the entire areas of external electrodes 46 and 48. Figures 1 to 3In order to simplify the accompanying drawings, plating layers 50 and 52 are represented as one layer, but in reality they are composed of multiple plating layers such as non-electrolytic copper plating layer, electrolytic copper plating layer, electrolytic nickel plating layer, and electrolytic tin plating layer.

[0034] In this chip-type fuse, protrusions 38 and 40 protrude from the internal electrodes 28 and 30 beyond the concave surfaces 16 and 18 into the concave surfaces 19 and 21, respectively. The entire area of ​​protrusions 38 and 40 is covered by plating layers 50 and 52, respectively. Therefore, the contact area between protrusion 38 and plating layer 50 is large, resulting in good electrical connection between them. Similarly, the contact area between protrusion 40 and plating layer 52 is large, also resulting in good electrical connection between them. Specifically, in this embodiment, protrusions 38 and 40 protrude from the entire area of ​​concave surfaces 16 and 18, thus their areas are large, and the contact areas between protrusions 38 and plating layer 50 and between protrusions 40 and plating layer 52 are further increased. As a result, protrusion 38 can reliably and well connect with plating layer 50, and protrusion 40 can reliably and well connect with plating layer 52. Furthermore, protrusions 38 and 40 are located within recesses 19 and 21 and do not protrude outward from recesses 19 and 21. Therefore, protrusions 38 and 40 will not obstruct the soldering of the chip-type fuse to the printed circuit board.

[0035] Figures 8 to 10 A chip-type fuse according to a second embodiment is shown. In this embodiment, the recesses 19 and 21 present in the chip-type fuse of the first embodiment, and the portions surrounding them, are removed from the housing 2a. As a result, the length of the housing 2a is shortened corresponding to the amount removed. Along with this removal, the internal electrodes 28a and 30a are also shortened so that their outer edges are... Figure 10 The internal electrodes 28a and 30a are formed in a manner consistent with the end faces 12a and 14a of the housing 2a and are short. The protrusions 38a and 40a protrude horizontally and further outward from the entire area of ​​the outer edges of the internal electrodes 12a and 14a. If the protrusions 38a and 40a were not present, the internal electrodes 28a and 30a would be exposed at the end faces 12a and 14a. These protrusions 38a and 40a are entirely covered by plating layers 50a and 52a. Other structures are the same as those of the chip-type fuse of the first embodiment, so the same reference numerals are used for equivalent parts, and their descriptions are omitted. In the chip-type fuse of this embodiment, a good electrical connection between the protrusions 38a and 40a and the plating layers 50a and 52a can also be obtained.

[0036] The chip fuses described in the two embodiments above can be modified in various ways. For example, in the chip fuse of the first embodiment, the length of the fusible portion 32 can be varied according to the desired fusing characteristics in the chip fuse. For example, as Figure 11aAs shown, a fusible portion 32a shorter than the fusible portion 32 can be used, or a curved fusible portion can be used instead of a straight fusible portion 32 as in the first embodiment. Furthermore, a characteristic adjustment portion can be provided midway through the fusible portion 32. In the chip-type fuse of the second embodiment, the fusible portion 32 can also be deformed in the same way.

[0037] In the chip-type fuses of the two embodiments described above, arc-suppressing materials can be added to the fusible portions 32 and 32a respectively, or arc-suppressing materials can be placed in the cavity 24 in a manner that surrounds the fusible portions 32 and 32a.

[0038] Additionally, spaces can be formed on the sides 8 and 10 of the housing 2, such as... Figure 11b As shown, the widths of the internal electrodes 28b and 30b are thinner than those of the internal electrodes 28 and 30 in the first embodiment, and reinforcing patterns 62 and 64, independent of the internal electrodes 28b and 30b, are provided in these spaces. Although reinforcing patterns 62 and 64 are provided, the strength of the housing 2 is improved. Regarding the reinforcing patterns 62 and 64, they can be formed simultaneously from the aforementioned metal when the fusible body 26 is formed by stamping or etching the metal. The reinforcing patterns can also be provided in the chip-type fuse of the second embodiment in the same way.

[0039] In the chip-type fuses of the two embodiments described above, plating layers 50, 52, 50a, and 52a are used as conductive layers, but conductive coating layers can also be used instead of plating layers 50, 52, 50a, and 52a. In particular, in the first embodiment, conductive coating layers can be provided in the recesses 19 and 21 in such a way that they completely cover the recesses 19 and 21.

[0040] In the chip-type fuses of the two embodiments described above, the housings 2 and 2a are rectangular, but other shapes, such as circular plates, elliptical plates, and bowls, can also be used.

[0041] In the chip-type fuses of the two embodiments described above, external electrodes 42 and 46 are provided on the upper surfaces of the housings 2 and 2a, and external electrodes 44 and 48 are provided on the lower surfaces. However, it is also possible to provide only the external electrodes 44 and 48 on the lower surfaces. In this case, the plating layer 50 can be formed to cover the protrusion 38 and the external electrode 44, and the plating layer 52 can be formed to cover the protrusion 40 and the external electrode 48. Similarly, the plating layer 50a can be formed to cover the protrusion 38a and the external electrode 44, and the plating layer 52a can be formed to cover the protrusion 40a and the external electrode 48.

[0042] In the chip-type fuse of the first embodiment, the concave surfaces 16 and 18 and the recessed surfaces 34 and 36 are made into a semi-circular shape, but are not limited to this shape. For example, they can also be U-shaped, channel-shaped or V-shaped.

[0043] In the chip-type fuse of the first embodiment, protrusions 38 and 40 protrude from the entire area of ​​concave surfaces 16 and 18, respectively, but protrusions 38 and 40 can also protrude from only a portion of concave surfaces 16 and 18. Similarly, in the second embodiment, protrusions 38a and 40a also protrude from the entire area of ​​the outer edge of the internal electrodes 28a and 30a, respectively, but protrusions can also be made from only a portion of them. In the chip-type fuses of the above two embodiments, protrusions 38, 40, 38a, and 40a protrude horizontally as a whole, but for example, the front ends of protrusions 38, 40, 38a, and 40a can also be bent toward the upper surface 4 or lower surface 6 of housings 2 and 2a. Even in this case, plating layers 50, 50a, 52, and 52a are provided in a manner that also covers the bent portion.

Claims

1. A chip-type fuse, comprising: A plate-shaped fusible body has internal electrodes respectively disposed at both ends of a straight line, and has a fusible portion formed integrally with the internal electrodes between these internal electrodes and being thinner than the internal electrodes; A housing that internally accommodates the fusible body, with portions of the internal electrodes exposed at both ends of the straight line; and A conductive layer is formed on the exposed portions of the internal electrodes in a manner that covers these exposed portions. A protrusion extending outward from the exposed portion is integrally formed with the exposed portion, and the protrusion is covered by the conductive layer. The housing has a recess, which has concave surfaces at both ends of the straight line that are connected to the straight line. The conductive layer is formed on the concave surface, and the protrusion protrudes from the concave surface into the recess. The internal electrode has at least a portion of a recessed surface located within the recess, and the protrusion is located between the recessed surface and the concave surface.

2. The chip-type fuse according to claim 1, wherein, The protrusion extends from the entire area of ​​the concave surface into the concave portion.

3. The chip-type fuse according to claim 1, wherein, At least one side of the housing is formed as a plane, and the conductive layer extends onto the plane.

4. A chip-type fuse, comprising: A plate-shaped fusible body has internal electrodes respectively disposed at both ends of a straight line, and has a fusible portion formed integrally with the internal electrodes between these internal electrodes and being thinner than the internal electrodes; A housing that internally accommodates the fusible body, with portions of the internal electrodes exposed at both ends of the straight line; and A conductive layer is formed on the exposed portions of the internal electrodes in a manner that covers these exposed portions. A protrusion extending outward from the exposed portion is integrally formed with the exposed portion, and the protrusion is covered by the conductive layer. The housing has a first plane and a second plane of the same shape, which are spaced apart and arranged parallel to each other, and a peripheral surface surrounding the edges of the first plane and the second plane, the protrusion protruding from the peripheral surface. The housing has concave surfaces at both ends of the straight line that are connected to the straight line and intersect the first plane and the second plane, the protrusions protruding from the entire area of ​​the concave surface, and the conductive layer is formed on the entire area of ​​the concave surface.

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