SMD (Surface Mount Device) fuse and fuse element thereof

Abstract

The invention discloses a patch type fuse and a fuse element thereof. The fuse element comprises a lead-free fuse, a fluxing agent layer and a porous metal layer, wherein the porous metal layer is fixed on one surface of the lead-free fuse wire through the fluxing agent layer; at the moment, part of the fluxing agent layer permeates into pores of the porous metal layer under the capillary action; therefore, the fluxing agent can fill the pores of the first porous metal layer and is uniformly distributed on the surface of the lead-free fuse wire, thereby effectively helping the porous metal layer and the lead-free fuse wire to be broken at over-current high temperature, and enabling a current loop to be interrupted by the fuse wire part in time.

Description

Technical Field

[0001] The invention relates to a fuse, in particular to a chip-type fuse and a fuse element thereof. Background Art

[0002] The chip fuse is used to be welded on a circuit board. When an abnormal condition such as overcurrent occurs in the current loop of the circuit board, the chip fuse can interrupt the current loop of the circuit board to protect the circuit board.

[0003] Traditional chip fuses use a piece of tin-lead alloy fuse, which has a melting point of about 290°C. However, in order to comply with the RoHS (Restriction of Hazardous Substance) regulations on the use of lead (Pb), it is necessary to use a piece of lead-free alloy fuse. For example, tin-bismuth alloy has a melting point of 245°C to 250°C. However, the melting point of tin-bismuth alloy is lower than that of tin-lead alloy, and is even lower than the temperature of the reflow process (for example, 260°C). As a result, the tin-bismuth alloy lead-free fuse will be blown after the reflow process and lose its fuse function. Therefore, please refer to Figure 7 In the conventional SMD fuse, a fuse element has two first metal layers 52a and a second metal layer 52b, each having a melting point higher than the reflow temperature, stacked on the upper and lower sides of a lead-free fuse 51. In addition, the conventional SMD fuse can further coat a flux 53 on the surface of the first metal layer 52a to effectively prevent the first metal layer 52a from being oxidized and to accelerate the fusing efficiency.

[0004] However, during the coating process of the above-mentioned conventional SMD fuse, if the coating amount is not properly controlled, the flux is easy to overflow to other places, and it is difficult to coat the flux evenly on the surface of the first metal layer in sufficient amount. Under overcurrent and high temperature, it cannot help the lead-free fuse and the first metal layer to effectively break and interrupt the current circuit in time. Summary of the invention

[0005] In view of the problem that a sufficient amount of flux cannot be uniformly coated on the chip fuse using the lead-free fuse, the main purpose of the present invention is to provide an improved chip fuse and a fuse element thereof to solve the above-mentioned problem.

[0006] To achieve the above purpose, the main technical means used by the present invention are to make the above-mentioned chip fuse include:

[0007] A base comprises a first surface, two electrodes and a heater; wherein the two electrodes and the heater are formed on the first surface, and the heater is located between the two electrodes;

[0008] A fuse element electrically connects the two electrodes of the base and the heater, and comprises:

[0009] A lead-free fuse, comprising two opposite second surfaces and a third surface; wherein the second surface spans across the two electrodes of the base and covers the heater;

[0010] a first flux layer formed on the third surface of the lead-free fuse;

[0011] a first porous metal layer, stacked on the first flux layer, and its periphery does not exceed the periphery of the lead-free fuse; wherein a portion of the first flux layer penetrates into the pores of the first porous metal layer and is bonded to the third surface of the lead-free fuse through the first flux layer; and

[0012] A hollow cover is disposed on the first surface of the base to cover the fuse element therein.

[0013] From the above description, it can be known that the chip fuse of the present invention mainly forms the first flux layer on the lead-free fuse of the fuse element, and then stacks the first porous metal layer on the first flux layer, so that part of the first flux layer penetrates into the first porous metal layer through capillary action, so that the flux fills the pores of the first porous metal layer and is evenly distributed on the lead-free fuse; in this way, the fuse element of the chip fuse of the present invention has evenly distributed and sufficient flux, and when an overcurrent occurs in the current circuit and high temperature is generated, the first flux layer can help the first porous metal layer and the lead-free fuse to be effectively blown, so as to interrupt the current circuit in time.

[0014] To achieve the above object, the main technical means used by the present invention are to make the fuse element of the above-mentioned chip fuse include:

[0015] A lead-free fuse comprising two opposite first and second surfaces;

[0016] a first flux layer formed on the first surface of the lead-free fuse;

[0017] A first porous metal layer is stacked on the first flux layer and its periphery does not exceed the periphery of the lead-free fuse; wherein the first flux layer penetrates into the pores of the first porous metal layer and is bonded to the first surface of the lead-free fuse through the first flux layer.

[0018] From the above description, it can be known that the fuse element of the chip fuse of the present invention mainly forms the first flux layer on the first surface of the lead-free fuse, and then stacks the first porous metal layer on the first flux layer, so that part of the first flux layer penetrates into the first porous metal layer through capillary action, so that the flux fills the pores of the first porous metal layer and is evenly distributed on the first surface of the lead-free fuse; in this way, the fuse element of the present invention has evenly distributed and sufficient flux, so that the first flux layer can help the first porous metal layer and the lead-free fuse to effectively blow under overcurrent and high temperature, so as to interrupt the current loop in time.

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but is not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A : A cross-sectional view of a first embodiment of a chip fuse of the present invention.

[0021] Figure 1B : Figure 1A A partial enlarged view of .

[0022] Figure 1C : A cross-sectional view of a second embodiment of the chip fuse of the present invention.

[0023] Figure 2A : A three-dimensional exploded view of a first embodiment of a fuse element of a chip fuse of the present invention.

[0024] Figure 2B : A three-dimensional exploded view of a second embodiment of the fuse element of the chip fuse of the present invention.

[0025] Figure 3 : A top plan view of a third embodiment of the fuse element of the chip fuse of the present invention disposed on a base.

[0026] Figure 4 : A top plan view of a fourth embodiment of the fuse element of the chip fuse of the present invention disposed on a base.

[0027] Figure 5 : A cross-sectional view of a fifth embodiment of the chip fuse of the present invention.

[0028] Figure 6 : A three-dimensional exploded view of the fifth embodiment of the fuse element of the chip fuse of the present invention.

[0029] Figure 7 : A cross-sectional view of a fuse element of an existing chip fuse.

[0030] Among them, the reference numerals

[0031] 10: Base

[0032] 12: First surface

[0033] 14: Electrode

[0034] 15: Heater

[0035] 16: Lead-out electrode

[0036] 17: The first good conductor layer

[0037] 18: Heating layer

[0038] 19: Second good conductor layer

[0039] 20, 20a, 20': Fuse

[0040] 21: Lead-free fuse

[0041] 22: Second Surface

[0042] 23: The third surface

[0043] 230: Accommodation space

[0044] 231: Around

[0045] 24: First flux layer

[0046] 24': Second flux layer

[0047] 25, 25a: first porous metal layer

[0048] 251: Porosity

[0049] 25': Second porous metal layer

[0050] 26: Third flux layer

[0051] 27: First frame edge

[0052] 27': Third Box

[0053] 28, 28a, 28b: Second frame edge

[0054] 28': Fourth box edge

[0055] 29: Gap

[0056] 30: Hollow cover

[0057] 51: Lead-free fuse

[0058] 52a: First metal layer

[0059] 52b: Second metal layer

[0060] 53: Flux DETAILED DESCRIPTION

[0061] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments to further understand the purpose, solution and effect of the present invention, but it is not intended to limit the scope of protection of the claims attached to the present invention.

[0062] The present invention relates to an improved chip fuse and a fuse element thereof. The technical contents of the present invention are described in detail below with reference to a plurality of embodiments and drawings.

[0063] See also Figure 1A , which is the first embodiment of the chip fuse of the present invention. The chip fuse comprises a base 10 , a fuse element 20 a and a hollow cover 30 .

[0064] The base 10 is made of an electrically insulating material and includes a first surface 12, two electrodes 14, and a heater 15; the two electrodes 14 are formed on the first surface 12; the heater 15 is formed on the first surface 12 and is located between the two electrodes 14, and a distance D is maintained between the heater 15 and each of the electrodes 14. Figure 3 As shown, the heater 15 may include an extraction electrode 16, a first good conductor layer 17, a heating layer 18 and a second good conductor layer 19. The extraction electrode 16 is located between the two electrodes 14; the first good conductor layer 17 covers the extraction electrode 16; the heating layer 18 covers the first good conductor layer 17; and the second good conductor layer 19 is formed on the heating layer 18. The first and second good conductor layers 17 and 19 are good conductors of electricity and heat, respectively.

[0065] The fuse element 20 a is electrically connected to the two electrodes 14 of the base 10 and the heater 15 , and includes a lead-free fuse 21 , a first flux layer 24 and a first porous metal layer 25 a .

[0066] The lead-free fuse 21 of the fuse element 20a includes a second surface 22 and a third surface 23. The second surface 22 faces the first surface 12 of the base 10 and spans the two electrodes 14 of the base 10; Figure 3As shown, the second surface 22 is attached to the heater 15; specifically, the second surface 22 of the lead-free fuse 21 is attached to the two electrodes 14 and the second good conductor layer 19 of the heater 15, so the lead-free fuse 21 is electrically connected to the two electrodes 14 and the heater 15. The third surface 23 of the lead-free fuse 21 is opposite to the second surface 22 and away from the first surface 12 of the base 10. In order to comply with the regulations on the restriction of lead (Pb) in RoHS, in this embodiment, the material of the lead-free fuse 21 is lead-free materials such as tin (Sn) or bismuth (Bi) or tin-bismuth alloy, but is not limited thereto. When a large current passes through the lead-free fuse 21 due to overcurrent, the large current will simultaneously pass through the second good conductor layer 19, the heating layer 18, the first good conductor layer 17 and the lead-out electrode 16 of the heater 15, thereby causing the heating layer 18 of the heater 15 to heat up. At this time, the second good conductor layer 19 can heat the lead-free fuse 21 evenly, and cause the lead-free fuse 21 to quickly heat up to its melting point, thereby melting.

[0067] Please cooperate Figure 2A As shown, the first flux layer 24 is formed on the third surface 23 of the lead-free fuse 21; in one embodiment, the material of the first flux layer 24 can be rosin, but it is not limited thereto. The periphery of the first porous metal layer 25a does not exceed the periphery of the lead-free fuse 21, and the first porous metal layer 25a is stacked on the first flux layer 24 and adhered to the third surface 23 of the lead-free fuse 21 through the first flux layer 24. At this time, due to the capillary action, part of the first flux layer 24 penetrates into the first porous metal layer 25a, that is, Figure 1B As shown, the flux of the first flux layer 24 will fill the pores 251 of the first porous metal layer 25a, so that the first flux layer 24 can be evenly distributed on the third surface 23 of the lead-free fuse 21. Preferably, the melting point of the first porous metal layer 25a is higher than the melting point of the lead-free fuse 21. In addition, in order to increase the flux amount, a third flux layer 26 can be further formed on the first porous metal layer 25. In one embodiment, the material of the first porous metal layer 25a can be gold (Au), silver (Ag), copper (Cu), zinc (Zn) or a porous alloy formed by at least two of gold, silver, copper and zinc, but is not limited thereto.

[0068] Please see again Figure 1C and Figure 2BIn the second embodiment shown, a first porous metal layer 25 of another fuse element 20 is in a frame shape, so in this embodiment, a first flux layer 24 of the fuse element 20 can be formed only on the periphery 231 of the third surface 23 of the lead-free fuse 21, and the first porous metal layer 25 is also bonded to the periphery 231 of the third surface 23 of the lead-free fuse 21 through the first flux layer 24; thus, the third surface 23 of the lead-free fuse 21 and the first flux layer 24 and the first porous metal layer 25 form a receiving space 230, so that the third flux layer 26 can be filled in the receiving space 230 to fix the position of the third flux layer 26; in one embodiment, the third flux layer 26 can also further cover the upper surface of the first porous metal layer 25. In this embodiment, the frame-shaped first porous metal layer 25 can include two opposite first frame edges 27 and two opposite second frame edges 28. like Figure 1C As shown, the two first frame edges 27 correspond to the two electrodes 14 of the base 10, and the two second frame edges 28 are respectively connected to the two first frame edges 27. In this embodiment, the widths of the first frame edges 27 and the second frame edges 28 can be the same, or can be as follows: Figure 3 In the third embodiment shown, the widths of the two relative first frame edges 27 and the two relative second frame edges 28a of the other frame-shaped first porous metal layer 25 can be different, that is, each of the first frame edges 27 has a first width W1, and each of the second frame edges 28a has a second width W2, and the second width W2 is smaller than the first width W1, so as to accelerate the breaking speed when overcurrent occurs. In this embodiment, the easy-to-break part of each of the second frame edges 28 is usually between the heater 15 and each of the electrodes 14, that is, Figure 1C The two spacings D are within the range shown; therefore, Figure 4 In the fourth embodiment shown, each second frame side 28b of another frame-shaped first porous metal layer 25 forms at least one notch 29 at a breakable location, making the width of the location narrower and accelerating the break speed when an overcurrent occurs; preferably, two notches 29 can be formed at the breakable location of each second frame side 28b.

[0069] like Figure 1A and Figure 1C As shown, the hollow cover 30 is disposed on the first surface 12 of the base 10 to cover the fuse elements 20a, 20 therein, and the hollow cover 30 is made of an electrically insulating material. Specifically, the hollow cover 30 is disposed on the first surface 12 of the base 10 and is located at the periphery of the two electrodes 14.

[0070] Please see again Figure 5 and Figure 6 , is the fifth embodiment of the chip fuse of the present invention, which is Figure 1CThe structure of the second embodiment of the present invention is substantially the same as that of the first embodiment of the present invention, except that: a fuse element 20' further includes a second flux layer 24' and a second porous metal layer 25', wherein the second flux layer 24' is formed around the second surface 22 of the lead-free fuse 21, and the second porous metal layer 25'

[0071] The second porous metal layer 25' is stacked on the second flux layer 24', and a portion of the second flux layer 24' penetrates into the second porous metal layer 25'. The second porous metal layer 25' is bonded to the periphery of the second surface 22 of the lead-free fuse 21 through the second flux layer 24'. Figure 5 As shown, the second porous metal layer 25 '

[0072] The second porous metal layer 25' spans across the two electrodes 14 of the base 10 and adheres to the second good conductor layer 19 of the heater 15, so that the second porous metal layer 25' forms an electrical connection with the two electrodes 14 and the heater 15. In one embodiment, the structure of the second porous metal layer 25' can be Figure 1C The first porous metal layer 25 shown in FIG. 1 is the same as that shown in FIG. 1 , namely, it includes two opposite third frame edges 27' and two opposite fourth frame edges 28'. Each of the fourth frame edges 28' may also be Figure 3 and Figure 4 The second frame edges 28a and 28b are the same. Figure 2A The second surface of the lead-free fuse 21 of the fuse element 20a may also be further bonded with a second porous metal layer (not shown) matching the first porous metal layer through a second flux layer (not shown).

[0073] As can be seen from the above description, the chip fuse and its fuse element of the present invention mainly form the first flux layer on the third surface of the lead-free fuse of the fuse element, and then stack the first porous metal layer on the first flux layer, so that part of the first flux layer penetrates into the first porous metal layer through capillary action, so that the flux fills the pores of the first porous metal layer and is evenly distributed on the third surface of the lead-free fuse, which can also increase the flux content and enhance the bonding strength between the two. In this way, the fuse element of the chip fuse of the present invention has evenly distributed and sufficient flux, and when an overcurrent occurs in the current circuit and high temperature is generated, the first flux layer can help the first porous metal layer and the lead-free fuse to be effectively blown, so as to interrupt the current circuit in time.

[0074] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A fuse element of a chip fuse, characterized in that: Include: A lead-free fuse comprising two opposite first and second surfaces; a first flux layer formed on the first surface of the lead-free fuse; A first porous metal layer is stacked on the first flux layer and its periphery does not exceed the periphery of the lead-free fuse; wherein the first flux layer penetrates into the pores of the first porous metal layer and is bonded to the first surface of the lead-free fuse through the first flux layer.

2. The fuse element of the chip fuse according to claim 1, characterized in that: The melting point of the first porous metal layer is higher than the melting point of the lead-free fuse.

3. The fuse element of the chip fuse according to claim 2, characterized in that: The first flux layer is formed around the first surface of the lead-free fuse; and The first porous metal layer is in a frame shape and comprises: Two opposite first frame edges each having a first width; and Two opposite second frame edges are respectively connected to the two first frame edges; wherein each of the second frame edges has a second width, and the second width is the same as or smaller than the first width.

4. The fuse element of the chip fuse according to claim 2, characterized in that: The first flux layer is formed around the first surface of the lead-free fuse; and The first porous metal layer is in a frame shape and comprises: two opposite first frame edges; and Two opposite second frame edges are respectively connected to the two first frame edges; wherein the portion of each second frame edge adjacent to the two first frame edges respectively forms at least one notch.

5. The fuse element of the chip fuse according to claim 2, characterized in that: A third flux layer is further formed on the upper surface of the first porous metal layer.

6. The fuse element of the chip fuse according to claim 3 or 4, characterized in that: The invention further comprises a third flux layer, wherein the third flux layer is filled in a containing space formed by the first surface of the lead-free fuse, the first flux layer and the first porous metal layer.

7. The fuse element of the chip fuse according to any one of claims 2 to 5, characterized in that: Further including: a second flux layer formed on the second surface of the lead-free fuse; and A second porous metal layer is stacked on the second flux layer; wherein a portion of the second flux layer penetrates into the pores of the second porous metal layer and is bonded to the second surface of the lead-free fuse through the second flux layer; wherein the melting point of the second porous metal layer is higher than the melting point of the lead-free fuse.

8. The fuse element of the chip fuse according to claim 7, characterized in that: The second flux layer is formed around the second surface of the lead-free fuse; and The second porous metal layer is in a frame shape and comprises: Two opposite third frame edges each having a first width; and Two opposite fourth frame edges are respectively connected to the two third frame edges; wherein each of the fourth frame edges has a second width, and the second width is the same as or smaller than the first width.

9. The fuse element of the chip fuse according to claim 7, characterized in that: The second flux layer is formed around the second surface of the lead-free fuse; and The second porous metal layer is in a frame shape and comprises: Two opposite third frame edges; and Two opposite fourth frame edges are respectively connected to the two third frame edges; wherein the portion of each fourth frame edge adjacent to the two third frame edges respectively forms at least one notch.

10. The fuse element of the chip fuse according to claim 5, characterized in that: The lead-free fuse is made of tin or bismuth or tin-bismuth alloy; The material of the first and third flux layers is rosin; The material of the first porous metal layer is gold, silver, copper, zinc or a porous alloy formed by at least two of gold, silver, copper and zinc.

11. A chip fuse, characterized in that: Include: A base comprises a first surface, two electrodes and a heater; wherein the two electrodes and the heater are formed on the first surface, and the heater is located between the two electrodes; A fuse element as claimed in any one of claims 1 to 10, wherein the second surface of the lead-free fuse crosses the two electrodes of the base and covers the heater; and A hollow cover is disposed on the first surface of the base to cover the fuse element therein.

12. The chip fuse according to claim 11, characterized in that: The heater contains: An extraction electrode is formed on the first surface of the base and is located between the two electrodes; A first good conductor layer is formed on the first surface of the base and covers the lead-out electrode; A heating layer is formed on the first surface of the base and covers the first good conductor layer; as well as A second good conductor layer is formed on the heating layer and adheres to the second surface of the lead-free fuse of the fuse element.

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