HK1170081A - Low current fuse - Google Patents

Description

Low current fuse

Technical Field

The present subject matter relates generally to electrical fuses, and more particularly to Land Grid Array (LGA) and Surface Mount (SMD) micro-current fuses using thin film technology. The present technology also relates to methods of manufacturing these fuses.

Background

Surface mounting has become the preferred technique for circuit board assembly. Thus, virtually all types of electrical components for surface mount (i.e., leadless) embodiments or applications have been or are being redesigned. Surface Mount Devices (SMDs) quickly incorporate all types of electrical circuits creating a corresponding need for SMD fuses.

Fuses play an important role on many circuit boards. Damage to the entire system, which might otherwise be caused by failure of individual, localized components, can be prevented by fusing the circuits, selected sub-circuits, and/or even certain individual components.

Many different performance characteristics of electronic components may be addressed to facilitate desired operation. An example of the prior art is U.S. patent 7,570,148 issued to Parker et al, which discloses certain fuse aspects proposed. The Parker et al patent is directed to a low resistance fuse that includes a fuse element layer and first and second intermediate insulating layers extending on opposite sides of and bonded to the fuse element layer. The fuse element layer is formed on the first intermediate insulating layer, and the second insulating layer is laminated on the fuse element layer. Another example is disclosed in U.S. Pat. No.5,296,833 (issued to Breen et al). The Breen et al patent is directed to a surface mount fuse device that includes an alumina-glass-fuse-glass-alumina laminate structure.

Additional references disclosing exemplary processes in the design of fuses include two U.S. patent nos. 5,228,188 and 5,166,656 issued to Badihi et al. These references to Badihi et al generally relate to surface mount fuses and methods of making the same.

The disclosures of all of these prior U.S. patent documents are incorporated by reference herein in their entirety. It should be noted that none of the documents in the prior art publications address the need to provide surface mountable fuses for millicurrent levels of about 50 milliamps. Some preferred embodiments suggest that packages of less than 80mil by 50mil (about 2mm by 1.5mm) are required, sometimes as small as 40mil by 20mil (about 1mm by 0.5 mm).

Disclosure of Invention

The present subject matter recognizes and addresses various design aspects as previously discussed, in addition to certain aspects related to fuses and related electronic technology. Accordingly, it is a primary object of the disclosed technology, in its broadest sense, to provide an improved fuse device. More specifically, the present disclosure describes a weak current fuse device that may be configured in either a Land Grid Array (LGA) configuration or a Surface Mount (SMD) configuration.

The present subject matter also relates generally to multilayer fuse devices and, more particularly, to a multilayer fuse device including a substrate having an elongated fuse element and a pair of integral contact pads formed at and coupled to opposite longitudinal ends of the fuse element, the fuse element being formed on one surface of the substrate. In some embodiments, a pair of passivation layers covering the fuse and the contact pads and a pair of windows may be provided, the windows opening through both passivation layers on both contact pads to accommodate the conductive electrode material plated through the passivation layers. The plated material may extend over the upper surface of the passivation layer and be coated with a solderable conductive material.

Particularly low current surface mount fuses with ratings of 0.025 to 0.125 amps are needed.

Note that: the rating of the fuse is the current that is intended to be used. Typically, fuses are designed to blow at a current of about 250% of the rated current.

A first aspect of the invention is to provide a surface mountable fuse rated to blow if exposed to a maximum current in the range of about 0.06 to 0.5 amps.

Such surface mount fuses may be obtained using a suitable metal film.

Typically, surface mountable fuses include nickel or copper tracks (tracks) 3 to 20 microns wide and 0.2 to 2 microns thick.

Typically, the surface-mountable fuse further comprises a dielectric substrate comprising a ceramic, a glass or a glass-ceramic.

Most preferably, the dielectric substrate comprises glass.

Typically, the surface mount fuses include nickel traces, which also include a thin layer of tantalum under the fuse metal to promote adhesion between the substrate and the metal.

Typically, the thin layer of tantalum is several hundred angstroms thick.

Typically, the surface-mountable fuse further comprises a passivation layer protecting the fuse metal.

In one embodiment, the passivation layer comprises silicon oxynitride.

Optionally, a tantalum layer is disposed over the fuse metal and under the passivation layer to promote adhesion of the passivation layer to the fuse metal.

Optionally, the passivation layer is 1 to 6 microns thick.

Typically, the surface-mountable fuse further comprises a polyimide encapsulation layer.

Typically, surface-mountable fuses are configured for use in Land Grid Array (LGA) or Surface Mount (SMD) applications.

Most typically, the surface mountable fuse also includes a terminal.

In one embodiment, the terminal includes a contact pad accessible through a window in the passivation layer.

Typically, the surface-mountable fuse further comprises an encapsulation layer of polyimide material having a window, which usually corresponds to a window formed in the passivation layer.

Additionally, the surface mountable fuse may include a protective coating of benzocyclobutene (BCB) or epoxy.

Optionally, the surface mountable fuse further comprises a copper (Cu) electrode plated through a window on the contact pad such that the electrode extends over the passivation layer.

Typically, the exposed portions of the Cu electrodes are terminated by nickel and tin (Ni/Sn) layers.

Alternatively, the exposed portion of the Cu electrode may be terminated using a Ball Grid Array (BGA) process.

In one exemplary embodiment, the subject matter of the present disclosure relates to a fuse comprising a substrate having respective upper, bottom, side and end surfaces; an elongated fuse element formed on the upper surface of this substrate; a pair of contact pads integrally formed at opposite ends of the fuse element; at least one passivation layer covering the fuse element and at least a portion of the contact pads; first and second conductive electrodes respectively coupled to an upper surface of each of the pair of contact pads; and at least one conductive termination layer for each of said electrodes.

In some embodiments, the first and second conductive electrodes may be bonded at one end thereof to one of each pair of such connection pads. Further, each of the first and second conductive electrodes may have a second end extending through at least one passivation layer. Additionally, at least one conductive termination layer may include a coating of the second end of each of the first and second conductive electrodes.

In other current alternatives, such first and second conductive electrodes along one edge thereof may extend to respective edge portions of the substrate. Further, the at least one conductive termination layer may include respective end terminations that are electrically coupled with each of the first and second conductive electrodes, respectively. Additionally, first and second conductive electrodes may be coupled to one of each pair of contact pads along one side thereof. Additionally, first and second conductive electrodes may be coupled to one of each pair of contact pads along one side thereof. In other alternatives, the at least one conductive termination layer may include respective end terminations electrically coupled with each of the first and second conductive electrodes, respectively. In some alternatives, such a termination layer may cover a portion of the side of the substrate adjacent each end.

In other variations of the present disclosure, exemplary embodiments of such fuses may include at least one pair of passivation layers covering the fuse element and the contact pads. Further, the termination layer may cover at least a portion of the upper surface of the passivation layer and may cover all end surfaces and a portion of the bottom surface of the substrate adjacent to each end, whereby the termination layer enables surface mounting of such fuses. In addition, the terminal layer may cover a portion of the side of the substrate adjacent to each end.

In still other variations of the present disclosure, the fuse may further include a window formed on each contact pad through the pair of passivation layers; wherein the first and second conductive electrodes may extend on an upper surface of the passivation layer on the contact pad; the termination layer may cover at least a portion of the conductive electrode extending on the upper surface of the passivation layer and cover at least a portion of the bottom surface of the substrate, whereby the termination layer enables surface mounting of the fuse. Also, in some cases, such a termination layer may cover a portion of the side of the substrate adjacent each end.

In other variations, the fuse may further include a glass layer overlying the passivation layer; wherein the first and second electrodes may extend in a direction of the end of the substrate and be exposed at the end of the substrate; the termination layer may cover at least a portion of an upper surface of the glass layer and may cover end and bottom surfaces of the substrate adjacent each end. In certain variations, the passivation layer may include a polyimide material. In addition, the passivation layer may include SiNO, Al₂O₃、SiO₂、Si₃N₄One or more of polyimide, benzocyclobutene, and glass.

In some other variations of the present disclosure, the fuse may further include a window formed on each contact pad through the at least one passivation layer; wherein the first and second conductive electrodes may extend on an upper surface of the at least one passivation layer on the contact pad; the termination layer may cover at least a portion of the conductive electrode extending on an upper surface of the at least one passivation layer, whereby the termination layer enables land grid array mounting of the fuse.

In some other current alternatives, the fuse element and the contact pad may be formed as an integral multilayer of adhesive and conductive material. Also, the first and second conductive electrodes may be bonded at one end thereof to the nickel layer of one of each pair of contact pads. Further, the fuse element and the contact pad may be formed as an integral layer of at least one of copper, nickel, cobalt, and iron or an alloy thereof. Additionally, in some alternatives, the first and second conductive electrodes may include a conductive metal. Further, the first and second conductive electrodes may include copper electrodes. In other configurations, the substrate may comprise one of a glass, a glass-ceramic, a ceramic, silicon, and a polymer material. Further, the conductive termination layer may include a termination metal. Also, the terminal metal may include nickel and tin layers.

Additional objects and advantages of the present subject matter are set forth in, or will be apparent to, those of ordinary skill in the art from the detailed description of the application. Moreover, it will be further appreciated by those of ordinary skill in the art that variations and modifications to the specifically illustrated, referred and discussed features and steps hereof may be practiced in various embodiments and uses of the subject matter without departing from the spirit and scope of the subject matter. Such variations may include, but are not limited to, substitution of equivalent means, features, materials, or steps for those illustrated and discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like.

Moreover, it is to be understood that different embodiments, as well as different presently preferred embodiments, of the disclosed technology may include various combinations or configurations of presently disclosed features or elements, or their equivalents (including combinations of features or configurations thereof not expressly shown in the figures or stated in the detailed description).

Those skilled in the art will appreciate the features and aspects of the disclosed subject matter more fully upon consideration of the remainder of the specification.

Drawings

The subject matter of the present disclosure, in its entirety and implementations thereof, including what is best mode known to those of ordinary skill in the art, is described in detail below with reference to the accompanying drawings. In the drawings:

FIG. 1 is a partial cut-away view of an exemplary first embodiment of a low current fuse in accordance with the present technique;

FIG. 2 is an assembled perspective view of the exemplary fuse embodiment shown in FIG. 1;

FIG. 3 is an exploded view of the exemplary fuse embodiment shown in FIG. 1;

FIG. 4A is a partial cross-sectional view of an exemplary second embodiment of a low current fuse in accordance with the present technique, the fuse configured for surface mount use;

FIG. 4B shows an enlarged portion of the contact pad area of the embodiment shown in FIG. 4A;

FIG. 5 is an assembled perspective view of the exemplary fuse embodiment shown in FIG. 4A;

FIG. 6 is a partial cross-sectional view of an exemplary third embodiment of a low current fuse in accordance with the present technique, the fuse configured for surface mount use;

FIG. 7 is an assembled perspective view of the exemplary fuse embodiment shown in FIG. 6, illustrating an alternative termination;

fig. 8 is an assembled perspective view of the exemplary fuse embodiment shown in fig. 6.

Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features, steps, or other elements of the present technology.

Detailed Description

As mentioned in the summary, some aspects of the present subject matter relate to improved low current fuse devices.

Referring now to the drawings, FIG. 1 is a cut-away view of an exemplary first embodiment of a low current fuse, indicated generally at 100, in accordance with the present technique. The low current fuse 100 is built on multiple layers starting from a glass-ceramic layer corresponding to the substrate 102. Glass substrates are preferred, but any ceramic such as alumina or other ceramics, silicon (Si), polymer substrates with suitable thermal properties (with or without a suitable passivation layer), or glass-ceramic materials may be used.

The fuse element 104 is fabricated by sputtering or other physical vapor deposition technique onto the substrate 102 and then patterning the fuse metal layer, with an adhesive layer 105 and integral contact pads 106 (only one visible in fig. 1) formed at each end of the fuse element. Various metals, including copper, having high conductivity and ductility may be used as the fuse. Nickel (Ni) has been found to be a good candidate, especially for very weak current fuses, but it should be noted that nickel exhibits a sharp increase in resistance with temperature. Without wishing to be bound by any particular theory, it is believed that this arises from ferromagnetic properties. Other magnetic materials, such as cobalt and some nickel and cobalt based alloys, are expected to have advantages. Thus, in alternative embodiments, other magnetic metals (Ni, Co, Fe, or alloys thereof) may be used.

These metals exhibit low joule heating and high electrical resistance to electron transport as well as other diffusion and thermally active degradation processes. Nickel and cobalt also have high ductility and corrosion resistance in air, water and chlorides, which provides reliable operation even in humid, moderately corrosive environments.

It should be reminded, however, that other metals, e.g. with suitable resistance/melting points, may also be used.

For example, the thickness of the fuse element 102 may vary from 0.2-2 microns. Such a thickness can be deposited relatively easily to an acceptable tolerance. Adhesion layers above and/or below the fuse material may also be used, including but not limited to Ta, Cr, TaN, TiW, Ti, TiN. A thin adhesion layer of tantalum (Ta) may preferably be used to promote adhesion to the substrate.

The thickness of such an adhesive layer 103 may be, for example, from 100-And (4) changing. It should also be understood by those skilled in the art that while the fuse element 104 is shown as a straight element, other configurations are possible, such as additional lengths are needed or desired. In some cases, curved or sinusoidal elements may be provided.

A silicon oxynitride (SiNO) passivation layer 108 having a window over the contact pad 106 may be disposed over the element 104 and the contact pad 106. In one exemplary configuration, the passivation layer 108 may be about 1-6 microns thick with windows provided by photolithographic application of the passivation layer 108 or by etching over an overlying layer of passivation material. In an alternative embodiment, the passivation layer 108 may be formed of any inorganic passivation material, including but not limited to Al₂O₃、SiO₂And Si₃N₄。

To help the passivation layer adhere to the fuse metal, a thin layer of material may be added, which may typically be tantalum, but optionally may be Ta, Cr, TaN, TiW, Ti, TiN. The adhesion layer may be selected appropriately according to the fuse metal, passivation layer and deposition process, and is not intended to be limited by a specific process, and may be designed to overcome such phenomena as lattice mismatch and residual stress.

A second passivation layer or protective sealing layer 110 may be applied over the passivation layer 108. To speed up deposition, the second passivation layer 110 may be, for example, a polymer of about 5-25 microns, such as a polyimide material, for example, and may also be formed with windows that generally correspond to the extent of the windows formed in the passivation layer 108. In some additional optional embodiments, the second passivation layer 110 may also be provided with a protective coating of benzocyclobutene (BCB), epoxy, or other protective coating.

Electrode 112 is then plated through the window on contact pad 106 such that electrode 112 extends through passivation layer 110. For example, where the fuse metal is copper, the fuse metal may even be other materials such as nickel, and for ease of fabrication, the electrode 112 is typically copper (Cu).

The exposed portion of the Cu electrode 112 is then terminated, typically by being coated with a nickel and tin (Ni/Sn) layer 114. Other metals may be used, particularly metals that may be suitable for more specific termination requirements. In alternative configurations, a micro Ball Grid Array (BGA) process or a copper-free solder ball bump process (studbumping technologies) may be used.

Referring to fig. 2, an assembled perspective view of an exemplary fuse 200 constructed in accordance with the present technology is shown. As can be seen in fig. 2, the fuse 200 includes a substrate 202, passivation layers 208 and 210, and a Ni/Sn cladding layer 214 exposed over copper electrodes (not shown).

Reference is made to fig. 3, which is an exploded view of an exemplary fuse 300 corresponding to the exemplary embodiment shown in fig. 1 and 2. In the exploded view, the fuse 300 reveals a substrate 302 and more clearly shows a pair of contact pads 306, 306' coupled to a fuse element 304, the pads being positioned at each opposing longitudinal end. In addition, openings 318, 318 'and 320, 320' in passivation layers 308 and 310, respectively, are more fully shown. It should be understood that the openings 318 and 320 are substantially coextensive in area and are uniformly aligned over the contact pads 306. Openings 318 ' and 320 ' (at opposite ends of passivation layers 308, 310) are similarly disposed in relation to contact pad 306 '.

Reference is now made to fig. 4A, which is a cut-away view of a second exemplary embodiment of a low current fuse, generally designated 400, in accordance with the present technique. The low current fuse 400 is built on multiple layers, starting with a glass, ceramic or glass-ceramic substrate layer 402, in substantially the same manner as previously described in connection with fig. 1.

A fuse element 404 having integral contact pads 406 at each end is formed by sputtering onto a substrate 402 and then patterning a fuse metal track such as a copper or nickel layer and is provided with a tantalum (Ta) adhesion layer underneath or on top of it. It should be understood by those skilled in the art that adhesive layers (not labeled in this example, but may be combined with layers such as those represented by layers 103 and 105 in fig. 1 and 3) may also be implemented for each of the presently disclosed subject matter in combination with the current fig. 4A embodiment. As more clearly shown by the enlarged contact pad area shown in FIG. 4B, in one exemplary configuration, the first Ta layer 416, followed by the Ni layer 426, and the second Ta layer 436 may be bonded together to form a thickness of about 0.1 to about 10 μ to be sputtered onto the glass substrate 402. As with the fuse 102 of fig. 1, in some alternative embodiments, a magnetic metal such as Ni, Co, Fe, or other alloys, or other metals such as copper with suitable resistance/melting points, may be used. Also similar to fig. 1, other adhesive layers above and/or below the fuse material may be used.

According to a second embodiment, a Surface Mount Device (SMD) may be provided by modifying the electrode structure illustrated above in connection with fig. 1-3. According to a second embodiment, an electrode material 446 may be disposed on and in contact with the fuse metal (typically nickel or copper) layer 426, the electrode material being positioned to substantially cover the Ni layer 406 and extend to the edge portion 450 of the substrate 402. In an exemplary configuration, electrode material 446 may be copper (Cu) and may be electroplated on Ni layer 416. Other methods of providing Cu layer 446 may also be employed, as is known to those skilled in the art. It should also be understood that the electrodes may be made of conductive materials other than copper. In addition, it should be noted that these additional electrode materials are not necessary because the material forming the pad region and the fuse is itself conductive.

After the electrode material 446 is provided, a first passivation layer 408 of silicon oxynitride (SiNO) may be provided, followed by application of a second passivation layer or protective encapsulation layer 410 onto the passivation layer 408. Finally a glass cover 412 or alternatively other insulating material may be applied. In this embodiment, no window is required (as shown in relation to the first embodiment), although windows may be formed to accommodate electrodes, as will be described later in relation to the embodiment shown in figure 6. The end terminations 442, 444 may then be applied using processes known to those skilled in the art to allow surface mounting of the completed device.

Referring to fig. 5, an assembled perspective view of an exemplary fuse 400 constructed in accordance with the present technology is shown. As can be seen in fig. 5, the fuse 400 includes a substrate 402, passivation layers 408 and 410, and a glass cover 412. The end terminations 442, 444 are applied at the respective ends 452, 454 of the device 400, and at the overlying portions of both the upper surface 454 and the bottom surface 458 shown in fig. 5. End termination material may optionally be applied to the side surfaces as shown in fig. 8. The end terminations 442, 444 may correspond to Cu terminations and may include a coating (not separately shown) of a material such as Ni/Sn or other solder material combination to facilitate securing the completed device to a circuit board, for example using known soldering or other securing techniques.

Reference is now made to fig. 6, which is a cut-away view of a third exemplary embodiment of a low current fuse, indicated generally at 600, in accordance with the present technique. The low current fuse 600 is built on multiple layers in substantially the same manner as previously shown with respect to fig. 1 and 3, starting with a dielectric layer such as glass, ceramic or glass-ceramic corresponding to the substrate 602.

According to a third embodiment of the present subject matter, a Surface Mount Device (SMD) is provided by modifying the electrode structure previously illustrated in connection with fig. 4-5. According to a third embodiment, electrode material 646 may be disposed over and in contact with metal layer 606 and positioned to cover a portion of metal layer 606. As shown in cut-away portion 646', the electrode material 646 extends upwardly through the windows in the passivation layers 608, 610 so as to extend at least to the surface of the upper passivation layer 610. The end terminals 644, 644 may then be applied using techniques well known to those skilled in the art to allow surface mounting of the completed device, as previously described with respect to fig. 4A and 5.

In the embodiment shown in fig. 6 and 8, the terminal materials 644, 842, 644, 844, 852 may extend not only along the end, upper and lower surfaces of the completed device, but also along the sides, as shown in 862, 864 in fig. 8.

Referring to fig. 7, there is an assembled perspective view of an exemplary fuse 700 constructed in accordance with the present technology having alternate terminations where termination materials 744, 752, 744 are confined to the end, top and bottom surfaces of the completed device.

The theory and resulting equations for calculating the appropriate dimensions (thickness, length and width of the metal strip used as a fuse) are well understood.

Examples of the invention

Referring to fig. 1, some preferred embodiments below are directed to providing a low current fuse 100 rated to blow if exposed to a current exceeding a maximum current between 0.1 and 0.5 amps.

The required dimensions can be accurately reproduced and the fuse needs to have a high electromigration resistance. Such a precise low current fuse can be obtained by depositing a fuse element 104, which fuse element 104 comprises a 3 to 20 μm (micrometer) wide nickel or copper track, has a predetermined thickness in the range of 0.2 to 2 micrometers, and preferably has an integral pad 106.

A thin layer 103 of tantalum is preferably deposited first to obtain good adhesion and to prevent interaction between the substrate 102 and the nickel fuse element 104.

Glass is selected as the substrate 102. It should be noted that various glasses, ceramics or glass-ceramics may be used.

The thin layer 103 of tantalum, which is typically several hundred angstroms thick, may be deposited by Physical Vapor Deposition (PVD).

It has been found that such a breakable fuse is suitable for encapsulation with polyimide.

A protective layer of silicon oxynitride may be first deposited by chemical vapor deposition on the nickel fuse element 104 for passivation, and then a second layer 110 of polyimide may be applied to the passivation layer 108.

A second layer of tantalum is preferably deposited over the fuse metal and under the passivation layer to obtain good adhesion of the passivation layer and to prevent interaction between the fuse element 104 and the passivation layer.

Once packaged, the overall size of these devices can be less than 2mm by 3mm and can be as small as 1mm by 0.5mm, enabling their surface mounting in small devices.

While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be apparent that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present invention has been disclosed by way of example rather than limitation, and it will be apparent to those skilled in the art that the disclosed subject matter does not preclude inclusion of such modifications, variations and/or additions to the present subject matter.

Claims with priority

This application claims priority to U.S. provisional patent application entitled "weak current fuse," filed on 14/10/2010, assigned as USSN 61/393,149, for the purpose of incorporation by reference.

Claims (24)

1. A surface mountable fuse rated from 0.025 to 0.125 amps.

2. The surface mountable fuse of claim 1, designed to blow if exposed to a maximum current in the range of about 0.06 to 0.5 amps.

3. The surface-mountable fuse of claim 1, comprising a fuse element comprised of nickel or copper tracks ranging from 3 to 20 μm wide and from 0.2 to 2 μm thick.

4. The surface-mountable fuse of claim 3, further comprising a dielectric substrate supporting the fuse element, the dielectric substrate comprising a material selected from the group of ceramic, glass, and glass-ceramic.

5. The surface-mountable fuse of claim 3, wherein the dielectric substrate comprises glass.

6. The surface mountable fuse of claim 3, further comprising a thin layer of tantalum below the fuse metal.

7. The surface mountable fuse of claim 5, wherein the thin layer of tantalum is a few hundred angstroms thick.

8. The surface mountable fuse of claim 3, further comprising a passivation layer protecting the nickel or copper.

9. The surface mountable fuse of claim 8, wherein the passivation layer comprises silicon oxynitride.

10. The surface mountable fuse of claim 9, wherein the passivation layer is 1 to 6 microns thick.

11. The surface mountable fuse of claim 9, wherein an adhesion layer is deposited between the fuse metal and the passivation layer.

12. The surface mountable fuse of claim 9, wherein the adhesion layer comprises tantalum.

13. The surface mountable fuse of claim 9, further comprising a polyimide encapsulation layer.

14. The surface mountable fuse of claim 1, configured for a Land Grid Array (LGA) or Surface Mount (SMD) application.

15. The surface mountable fuse of claim 3, further comprising a termination.

16. The surface mountable fuse of claim 15, wherein the terminations comprise contact pads at each end of the fuse element and accessible through windows in the passivation layer.

17. The surface mountable fuse as recited in claim 16, further comprising an encapsulation layer of polyimide material having an additional window substantially corresponding to the window formed in the passivation layer.

18. The surface mountable fuse of claim 16, further comprising a benzocyclobutene (BCB) or epoxy protective coating.

19. The surface mountable fuse of claim 16, further comprising a copper (Cu) electrode formed by electroplating through a window on the contact pad such that the electrode extends over the passivation layer.

20. The surface-mountable fuse of claim 16, wherein the exposed portion of the Cu electrode is terminated with a nickel and tin (Ni/Sn) layer.

21. The surface mountable fuse of claim 16, wherein the exposed portion of the Cu electrode is terminated using a micro Ball Grid Array (BGA) process.

22. The surface mountable fuse of claim 16 fabricated as a component having overall dimensions no greater than 3mm x 2 mm.

23. The surface mountable fuse of claim 16 fabricated as a component having overall dimensions no greater than 1mm x 0.5 mm.

24. A fuse, comprising:

a substrate having respective upper, bottom, side and end surfaces;

an elongated fuse element formed on the upper surface of the substrate;

a pair of contact pads integrally formed at opposite ends of the fuse element;

at least one passivation layer covering the fuse element and at least a portion of the contact pads;

first and second conductive electrodes respectively coupled to an upper surface of each of the pair of contact pads; and

at least one conductive termination layer for each of said electrodes.