Surface Mount Thin Film Fuses with Compliant Terminals

Abstract

A surface mountable thin film fuse assembly is disclosed, which may include a substrate having a top surface, a first end, and a second end spaced apart from the first end in a longitudinal direction. The thin film assembly may include a fuse layer formed on the top surface of the substrate. The fuse layer may include a thin film fuse track. An external terminal may be disposed along the first end of the substrate and electrically connected to the thin film fuse track. The external terminal may include a compliant layer including a conductive polymeric composition.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 62 / 841,917, filed May 2, 2019, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present subject matter relates generally to surface mountable thin film assemblies, and in particular to surface mountable thin film fuses having compliant terminals. Background Art

[0004] Surface mounting has become the preferred technology for circuit board assembly. As a result, virtually all types of electronic components have been or are being redesigned for surface mount (i.e., leadless) implementations or applications. The rapid incorporation of surface mount devices (SMDs) into all types of electronic circuits has created a corresponding demand for SMD fuses.

[0005] Fuses play an important role on many circuit boards. By fusing circuits, selected subcircuits, and / or even certain individual components, damage to the entire system can be prevented that might otherwise result from the failure of a single local component.

[0006] Surface mount fuses are often subject to intermittent current surges, which generate significant heat. As a result, the fuses are subject to thermal cycling and thermal stress. Thermal stress may undesirably cause the rigid terminals to detach from the surface to which the surface mount fuse is mounted. Summary of the invention

[0007] According to one embodiment of the present disclosure, a surface mountable thin film fuse assembly may include a substrate having a top surface, a first end, and a second end spaced apart from the first end in a longitudinal direction. The thin film fuse assembly may include a fuse layer formed on the top surface of the substrate. The fuse layer may include a thin film fuse track. An external terminal may be disposed along the first end of the substrate and electrically connected to the thin film fuse track. The external terminal may include a compliant layer including a conductive polymeric composition.

[0008] According to one embodiment of the present disclosure, a method for forming a surface mountable thin film fuse assembly is disclosed. The method may include providing a substrate having a first end and a second end spaced apart from the first end in a longitudinal direction. The method may include depositing a fuse layer formed on a top surface of the substrate. The fuse layer may include a thin film fuse track. The method may include forming an external terminal along the first end of the substrate, the external terminal being connected to the fuse layer. The external terminal may include a compliant layer, the compliant layer including a conductive polymeric composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A full and enabling description of the presently disclosed subject matter, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0010] Figure 1 shows a cutaway perspective view of an embodiment of a surface mountable thin film fuse assembly according to aspects of the present disclosure;

[0011] Figure 2 According to aspects of the present disclosure Figure 1 A side view of an embodiment of a surface mountable fuse assembly;

[0012] Figure 3A shows a perspective view of another embodiment of a surface mountable thin film fuse assembly according to aspects of the present disclosure;

[0013] Figure 3B Shows Figure 3A A perspective view of a portion of an embodiment of a surface mountable thin film fuse assembly;

[0014] Figure 4 A flow chart of a method for forming a surface mountable thin film fuse assembly according to aspects of the present disclosure is shown.

[0015] Repeated use of reference characters throughout the present specification and drawings is intended to represent the same or analogous features, steps, or other elements of the technology. DETAILED DESCRIPTION

[0016] Those skilled in the art will appreciate that the present disclosure is merely a description of exemplary embodiments and is not intended to be limiting of the broader aspects of the subject matter, which are embodied in the exemplary configurations.

[0017] Generally, the present disclosure relates to a surface-mountable (SMD) fuse that includes at least one external terminal that includes a compliant layer. Thin-film fuses often experience thermal cycles caused by current surges. During such thermal cycles, the compliant layer can prevent the terminal from breaking or detaching from the mounting surface to which the external terminal is attached.

[0018] The thin film fuse assembly may include a substrate having a first end and a second end spaced apart from the first end in a longitudinal direction. A fuse layer including a thin film fuse track may be formed over a top surface of the substrate. A first external terminal may be disposed along the first end of the substrate and connected to the thin film fuse track. A second external terminal may be disposed along the second end of the substrate and connected to the thin film fuse track.

[0019] As used herein, "formed on" may refer to a layer that is in direct contact with another layer. However, an intermediate layer may also be formed between them. In addition, when used with reference to a bottom surface, "formed on" may be used relative to an outer surface of a component. Thus, a layer "formed on the bottom surface" may be closer to the exterior of the component than a layer formed thereon.

[0020] One or more of the external terminals may include a compliant layer comprising a conductive polymeric composition. The conductive polymeric composition may include one or more suitable polymeric materials. As an example, the compliant layer may include an epoxy resin, a polyimide, an amidoamine, a phenolic resin, and / or a silicone epoxy resin. The polymer may include a thermosetting or thermoplastic resin.

[0021] The conductive polymer composition may include conductive particles that may be dispersed within the polymer (e.g., as a polymer matrix) and may improve the conductivity of the compliant layer. The conductive particles may be or include a metal, such as silver, gold, copper, etc. For example, the conductive particles may be or include silver, copper, gold, nickel, tin, titanium, or other conductive metals. Thus, in some embodiments, the compliant layer may include a silver-filled polymer, a nickel-filled polymer, a copper-filled polymer, etc.

[0022] In some embodiments, one or more of the conductive particles may include a layer of conductive material formed on a base material. For example, one or more of the conductive particles may have a layer of precious metal (e.g., silver, gold, etc.) on a base metal (e.g., copper).

[0023] The compliant layer may have a Young's modulus of less than about 20 GPa, in some embodiments less than about 10 GPa, in some embodiments less than about 5 GPa, and in some embodiments less than about 3 GPa, as tested according to ASTM D638-14 at about 23°C and 20% relative humidity.

[0024] The compliant layer may exhibit low electrical resistance. For example, the compliant layer may exhibit a volume resistivity of less than about 0.01 ohm-cm, in some embodiments less than about 0.001 ohm-cm, and in some embodiments about 0.0001 ohm-cm or less as tested according to ASTM B193-16.

[0025] The compliant layer of the external terminal may be formed by dipping the monolithic body into a solution of the conductive polymeric composition to form a thick film layer of the conductive polymeric composition.

[0026] A fuse layer that may include thin film elements may be formed using a variety of suitable techniques. Examples of techniques that may be employed include chemical deposition (e.g., chemical vapor deposition), physical deposition (e.g., sputtering), or any other suitable deposition technique for forming thin film elements. Additional embodiments include any suitable patterning technique (e.g., photolithography), etching, and any other suitable subtractive technique for forming thin film elements.

[0027] The fuse layer, which may include a thin film element, may be or include a variety of suitable materials. For example, a variety of metals may be used, including copper having high conductivity and ductility. In some embodiments, the thin film element may be or include nickel (Ni).

[0028] The thickness of the fuse layer can vary. For example, in some embodiments, the thickness of the fuse layer can range from about 0.05 microns to about 40 microns, in some embodiments from about 0.1 microns to about 30 microns, and in some embodiments from about 0.5 microns to about 10 microns.

[0029] In some embodiments, the fuse track may be generally straight. It will also be appreciated that other configurations are possible, for example where additional length is needed or desired. As an example, in some embodiments, the fuse track may be curved, may be serrated, or may have a sinusoidal shape.

[0030] The fuse track can be configured to "fail" or "blow" (e.g., stop electrically connecting the terminals together) when the current flowing through the fuse track exceeds a maximum current within a specified time. The maximum current may be related to the rated current of the fuse assembly. For example, the threshold current may be 250% of the rated current at which the fuse blows in 5 seconds.

[0031] In other embodiments, the maximum current that the fuse has can range from about 0.1 ampere to about 4 amperes or greater and in some embodiments from about 0.25 ampere to about 2 amperes. However, in other embodiments, the fuse can be configured as an ultra-low current fuse. In such embodiments, the maximum current of the fuse can be in the range of about 5 milliamperes (mA) to about 100mA, in some embodiments in the range of about 10mA to about 75mA, and in some embodiments in the range of about 20mA to about 50mA.

[0032] The film fuse assembly may include at least one terminal. In some embodiments, the assembly may include a pair of terminals. However, in other embodiments, the assembly may include more than two terminals. For example, in some embodiments, the number of terminals may be in the range of 2 to 12 or more, in the range of 2 to 10 in some embodiments, and in the range of 2 to 8 in some embodiments. The terminals may be arranged symmetrically about the longitudinal center line, the transverse center line or the two. For example, the assembly may include 2 terminals per side, 3 terminals per side, 4 terminals per side or more.

[0033] The terminal may include multiple layers. These layers may be formed using a variety of techniques, such as dipping, screen printing, electroplating, chemical deposition (eg, chemical vapor deposition), physical deposition (eg, sputtering), or any other suitable technique.

[0034] In some embodiments, the terminal may include a first layer formed over the first end of the substrate and in electrical contact with the thin film fuse track. The first layer of conductive material may be or include copper (e.g., formed by dipping or printing using a conductive adhesive). In other embodiments, the first layer of conductive material may be or include a variety of other suitable materials, such as gold, silver, platinum, nickel, copper, steel, or a combination thereof. A compliant layer may be formed over the first layer. However, it should be understood that multiple layers may be formed between the compliant layer and the substrate.

[0035] In some embodiments, the terminal may include one or more additional conductive layers formed on the compliant layer, which may be formed above the first layer. For example, a second layer may be formed on the compliant layer. Thus, the compliant layer may be formed between the first layer and the second layer. In some embodiments, a third layer may be formed on the second layer. The second layer and / or the third layer may include a solderable conductive material. For example, the second layer may be or include nickel. The third layer may be or include tin. It should be understood that the second layer and / or the third layer may alternatively be or include tin, nickel, lead, or a mixture thereof.

[0036] The thickness of the first layer of the terminal can range from about 10 microns to about 200 microns, in some embodiments, from about 15 microns to about 100 microns, in some embodiments, from about 15 microns to about 80 microns, and in some embodiments, from about 20 microns to 60 microns.

[0037] The maximum thickness of the compliant layer of the terminal can be in the range of about 10 microns to about 200 microns, in some embodiments in the range of about 15 microns to about 100 microns, in some embodiments in the range of about 15 microns to about 80 microns, and in some embodiments in the range of about 20 microns to 60 microns.

[0038] The ratio of the maximum thickness of the compliant layer to the thickness of the fuse layer can be in the range of about 0.25 to about 100, in some embodiments in the range of about 0.3 to about 50, in some embodiments in the range of about 0.5 to about 30, in some embodiments in the range of about 1 to about 20, in some embodiments in the range of about 2 to about 10, and in some embodiments in the range of about 3 to about 8. For example, a fuse with a relatively small contact area (corresponding to a thin fuse layer) can benefit from a relatively thick compliant layer to relieve thermal stress at the contact area between the fuse layer and the external terminal. Therefore, the above ratio can provide a more stable and reliable connection between the fuse layer and the external terminal, thereby making the fuse more stable and reliable.

[0039] The thickness of the second layer of the terminal can be in the range of about 1 micron to about 30 microns, in some embodiments in the range of about 2 microns to about 20 microns, in some embodiments in the range of about 3 microns to about 15 microns, and in some embodiments in the range of about 4 microns to 10 microns, for example, about 7 microns.

[0040] The total thickness of the terminal (eg, including the first layer and any subsequent layers, if present) may preferably be in the range of about 15 microns to about 60 microns, and in some embodiments, in the range of about 20 microns to about 40 microns.

[0041] The fuse layer may include one or more contact pads connected to the thin film fuse track. A first contact pad may be electrically connected to the thin film element, the contact pad extending to one of the first end or the second end of the substrate and electrically connected to one of the external terminals at the first end.

[0042] In some embodiments, the assembly may include at least one adhesion layer formed on and / or below the fuse layer. The adhesion layer may be or include a variety of materials suitable for improving adhesion between the fuse layer and adjacent layers. For example, the adhesion layer may include at least one of Ta, Cr, TaN, TiW, Ti, or TiN. For example, in some embodiments, the adhesion layer may be or include tantalum (Ta) (e.g., tantalum or its oxide or nitride) and may be formed between the fuse layer and the substrate to improve adhesion. As another example, in some embodiments, the adhesion layer may be formed above the fuse layer and below the passivation layer, which will be described in more detail below. Without being bound by theory, the material of the adhesion layer may be selected to overcome phenomena such as lattice mismatch and residual stress.

[0043] The adhesion layer can have a variety of suitable thicknesses. For example, in some embodiments, the thickness of the adhesion layer can be in the range of about 100 angstroms to about 2000 angstroms, in some embodiments in the range of about 200 angstroms to about 800 angstroms, and in some embodiments in the range of about 400 angstroms to about 600 angstroms.

[0044] In alternative embodiments, the thin film fuse assembly may include one or more passivation layers formed on at least a portion of the fuse layer. The passivation layer may be applied on the fuse layer. The passivation layer may cover and protect the thin film fuse from the influence of a deposition process (e.g., electroplating) for forming a terminal. The passivation layer may be formed by a variety of suitable materials (including polymeric materials). For example, in some embodiments, the passivation layer may be or include polyimide. In some embodiments, the passivation layer may include at least one of silicon oxynitride, Al2O3, SiO2, Si3N4, benzocyclobutene, or glass.

[0045] In some embodiments, the protective layer can be applied on the passivation layer (if present) or directly on the fuse layer. The protective layer can have a thickness in the range of about 3 microns to about 25 microns, in some embodiments in the range of about 5 microns to about 20 microns, and in some embodiments in the range of about 7 microns to about 15 microns. In some embodiments, multiple protective layers can be used.

[0046] The substrate, passivation layer and / or protective layer may be formed of a variety of inorganic materials such as glass, ceramic or glass-ceramic mixtures. The substrate may generally have a low thermal conductivity, such as less than about 10 W / (m·K), less than about 5 W / (m·K) in some embodiments, less than about 3 W / (m·K) in some embodiments, less than about 2 W / (m·K) in some embodiments, and less than about 1 W / (m·K) in some embodiments, and greater than about 0.1 W / (m·K) in some embodiments. In another embodiment, however, the substrate may have a thermal conductivity greater than 10 W / (m·K) and / or For example, the substrate may include silicon oxynitride, silicon oxide, silicon, aluminum oxide, sapphire and / or other suitable materials.

[0047] In some embodiments, the passivation layer and / or the protective layer may be formed by depositing a paste (eg, a glass paste, a glass-ceramic paste, etc.) followed by a firing step. However, any suitable process may be used to form the passivation layer and / or the protective layer.

[0048] Figure 1 is a perspective view of one embodiment of a surface mountable thin film fuse assembly 100 according to aspects of the present disclosure. Figure 2 is a diagram showing an external terminal including a compliant layer Figure 1 A side view of a surface mountable thin film fuse assembly 100 is shown. Figure 1 and Figure 2 , the surface mountable thin film fuse assembly 100 may include a substrate 102. The substrate 102 may have a top surface 104, a first end 106, and a second end 108 ( Figure 1 ), the second end being spaced apart from the first end 106 in the longitudinal direction 110.

[0049] A fuse layer 112 may be formed over the top surface 104 of the substrate 102. The fuse layer 112 may include a thin film fuse track 114. The fuse layer 112 may have a thickness 113 of less than about 40 microns in the Z direction 115. The fuse track 114 may be generally straight, such as Figure 1 It should also be understood that other configurations are possible, for example, where additional length is needed or desired. As an example, in some embodiments, the fuse track 114 may be curved, may be serrated, or may have a sinusoidal shape.

[0050] The fuse track 114 can be configured to "fail" or "blow" (e.g., stop electrically connecting the terminals together) when the current flowing through the fuse track exceeds a maximum current within a specified time (e.g., 5 seconds). The maximum current may be related to the rated current of the fuse assembly. For example, the threshold current may be 250% of the rated current at which the fuse blows within 5 seconds.

[0051] The fuse layer 112 may include a first contact pad 116 extending to the first end 106 of the substrate 102 and a second contact pad 118 extending to the second end 108 of the substrate 102 ( Figure 2 ). The contact pads 116, 118 may be integrally formed with the fuse track 114 during formation of the fuse layer 112. The second contact pad 118 may be generally similar to the first contact pad 116. For example, the contact pads 116, 118 may be spaced apart relative to the lateral centerline 120 ( Figure 2 However, it should be understood that the contact pads 116, 118 may have any suitable shape, including rectangular, triangular, circular, etc.

[0052] The surface mountable thin film fuse assembly 100 can include one or more passivation layers formed on the thin film fuse layer 112. For example, a first passivation layer 122 can be formed on the thin film fuse layer 112. A second passivation layer 124 can be formed on the first passivation layer 122.

[0053] The surface mountable thin film fuse assembly 100 may include a first external terminal 140 disposed along the first end 106 of the substrate 102 and connected to the first contact pad 116 of the fuse layer 112. The surface mountable thin film fuse assembly 100 may include a second external terminal 142 disposed along the second end 108 of the substrate 102 and connected to the second contact pad 116.

[0054] For example, the first external terminal 140 may include a first base layer 146 formed over the first end 106 of the substrate 102 and electrically connected to the first contact pad 116. The second external terminal 142 may include a second base layer 148 formed over the second end 108 of the substrate 102 and electrically connected to the second contact pad 118. The base layers 146, 148 may be formed by dipping the ends 106, 108 of the substrate 102 to form a thick film layer of a conductive material such as copper, silver, gold, etc. However, in other embodiments, the base layers 146, 148 may be formed using other suitable techniques such as plating (e.g., electroplating or chemical plating or a combination thereof).

[0055] The first external terminal 140 may include a first compliant layer 150 formed on the first base layer 146. The second external terminal 142 may include a second compliant layer 152 formed on the second base layer 148. The compliant layers 150, 152 may include a conductive polymeric composition. For example, the conductive polymeric composition may include a polymeric material (e.g., epoxy resin) and conductive particles, such as described above.

[0056] The compliant layers 150, 152 may have respective maximum thicknesses 153, 155 in the longitudinal direction 110. A ratio of the maximum thicknesses 153, 155 of the compliant layers 150, 152 to the thickness 113 of the fuse layer 112 may be in the range of about 0.25 to about 4.

[0057] The external terminals 140, 142 may include one or more plating layers formed on the compliant layers 150, 152. For example, the first external terminal 140 may include a first plating layer 154 formed on the first compliant layer 150. The second external terminal 142 may include a first plating layer 156 formed on the second compliant layer 152. In some embodiments, respective second plating layers 158, 160 may optionally be formed on the first plating layers 154, 156.

[0058] The plating layers 154, 156, 158, 160 can be formed of a variety of suitable metals. In one embodiment, the first plating layers 154, 156 can include nickel. The second plating layers 158, 160 can include tin. However, any suitable conductive material combination can be used for the first plating layers 154, 156 and / or the second plating layers 158, 160. However, in other embodiments, the terminals 140, 142 can have different plating configurations (e.g., without one or more of the first plating layers 154, 156 and / or the second plating layers 158, 160).

[0059] In some embodiments, the protective layer can be exposed along the exterior of the surface mountable thin film fuse assembly 100 (e.g., applied over the passivation layers 122, 124 and / or the bottom surface 157 of the substrate 102). The protective layer can have a thickness in the range of about 5 microns to about 25 microns. For example, the protective layer can include glass, ceramic, or a glass-ceramic mixture.

[0060] As an embodiment, the passivation layers 122, 124 may be or include glass or a glass-ceramic mixture.A protective layer may be formed over the second passivation layer 124 and may be or include glass or a glass-ceramic mixture.

[0061] Figure 3A A perspective view of another embodiment of a surface mountable thin film fuse assembly 200 according to aspects of the present disclosure is shown. Figure 3B Shows Figure 3A A perspective view of a portion of a surface mountable thin film fuse assembly 200 is shown. The surface mountable thin film fuse assembly 200 may be similar to the previously described thin film fuse assembly. Figure 1 The device is constructed in substantially the same manner as described to include multiple layers, starting with a glass, ceramic or glass-ceramic substrate layer 202. The fuse layer 204 may include a fuse track having an integrated contact pad 206 at each end thereof, such as described above with reference to Figure 1As described. The fuse layer 204 may be formed by sputtering a conductive material onto the substrate 202 and then by patterning the fuse tracks and contact pads 206. The fuse layer 204 may include copper or nickel. One or more adhesion layers may be formed below the fuse layer 204 and / or above the fuse layer 204 to improve adhesion between the fuse layer and adjacent layers (e.g., the substrate 202 and / or the first passivation layer 208).

[0062] The surface mountable thin film fuse assembly 200 may include a first external terminal 242 disposed along a first end 250 of the substrate 202 and connected to a first contact pad 206 of the fuse layer 204. The surface mountable thin film fuse assembly 200 may include a second external terminal 244 disposed along a second end 252 of the substrate 202 and connected to the second contact pad 116.

[0063] More specifically, refer to Figure 3B , the surface mountable thin film fuse assembly 200 may include a first adhesion layer 216 covering a conductive layer 226 (e.g., nickel) of the contact pad 206. The surface mountable thin film fuse assembly 200 may include a second adhesion layer 236 formed on the conductive layer 226 of the contact pad 206. In this embodiment, the conductive layer 226 and the adhesion layers 216, 236 (if present) may have a total thickness in the range of about 0.1 microns to about 10 microns thick. The adhesion layers 216, 236 and the conductive layer 226 may be sputtered ( Figure 3A ). In alternative embodiments, magnetic metals (such as Ni, Co, Fe, or alloys thereof) or other metals (such as copper with appropriate resistance / melting point) may be employed. As described above, other materials and configurations may also be employed.

[0064] In some embodiments, electrode material 246 can be disposed on and in contact with conductive layer 226 (eg, comprising nickel or copper). Electrode material 246 can extend to substrate 202 ( Figure 3A ) so that the electrode material 246 contacts the first external terminal 242 ( Figure 3A ). Therefore, the electrode material 246 can increase the contact area between the fuse layer 206 and the first external terminal 242 to form a more stable connection between the fuse layer and the first external terminal. Therefore, the fuse can be more resistant to thermal cycles and thermal stress.

[0065] In an exemplary configuration, the electrode material 446 can be copper (Cu) and can be electroplated on the first passivation layer 216. As will be appreciated by one of ordinary skill in the art, other methods for depositing the electrode material 246 can also be employed. It should also be understood that the electrode material 246 can be made of a conductive material other than copper. In addition, it should be understood that in some embodiments, the surface mountable thin film fuse assembly 200 can lack such additional electrode material 246.

[0066] Reference again Figure 3A After placing the electrode material 246, a first passivation layer 208 of silicon oxynitride (SiNO) may be formed over the fuse layer 204. A second passivation layer 210 may be formed over the first passivation layer 208. Finally, a glass cover 212 may be applied, or alternatively other insulating materials. The end terminals 242, 244 may include a compliant layer and may be substantially as described above with reference to Figure 2 Configure as described.

[0067] Figure 4 FIG. 4 is a flow chart of a method 400 for forming a surface mountable thin film fuse assembly according to aspects of the present disclosure. Figures 1 to 3B The method 400 is described with reference to the surface mountable thin film fuse assembly 100, 200. However, it should be understood that the disclosed method 400 can be implemented with any suitable thin film fuse. Figure 4 , for the purpose of illustration and discussion, the steps performed in a particular order are depicted, but the methods discussed herein are not limited to any particular order or arrangement. Those skilled in the art will understand, using the disclosure provided herein, that the various steps of the methods disclosed herein may be omitted, rearranged, combined, and / or modified in various ways without departing from the scope of the present disclosure.

[0068] The method 400 may include providing, at (402), a substrate having a first end and a second end spaced apart from the first end in a longitudinal direction, such as described above with reference to Figures 1 to 3B As described.

[0069] Method 400 may include, at (404), depositing a fuse layer formed over a top surface of the substrate. The fuse layer may include a thin film fuse track, such as described above with reference to Figures 1 to 3B As described.

[0070] The method 400 may include: forming an external terminal along the first end of the substrate at (406), the external terminal being connected to the fuse layer, such as the one described above with reference to Figures 1 to 3B The external terminal may include a compliant layer, which may include a conductive polymeric composition.

[0071] Although the subject matter of the present invention has been described in detail with reference to specific embodiments of the subject matter of the present invention, it should be understood that those skilled in the art can easily make changes, variations and equivalent substitutions to these embodiments after understanding the foregoing. Therefore, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not exclude such modifications, variations and / or additions to the subject matter that will be readily apparent to those of ordinary skill in the art.

Claims

1. A surface mountable thin film fuse assembly comprising: a substrate having a top surface, a first end, and a second end spaced apart from the first end in a longitudinal direction; a fuse layer formed over the top surface of the substrate, the fuse layer comprising a thin film fuse track; as well as an external terminal disposed along the first end of the substrate and connected to the fuse layer, the external terminal comprising a compliant layer, the compliant layer comprising a conductive polymeric composition, wherein: The fuse layer has a fuse layer thickness in a Z direction perpendicular to the top surface of the substrate; The compliant layer has a maximum compliant layer thickness in a longitudinal direction, the maximum compliant layer thickness being in a range of 10 micrometers to 200 micrometers; and A ratio of the maximum compliant layer thickness to the fuse layer thickness is in the range of 0.25 to 100.

2. The surface mountable thin film fuse assembly of claim 1, wherein: The conductive polymeric composition includes an epoxy resin.

3. The surface mountable thin film fuse assembly of claim 1, wherein: The conductive polymeric composition includes conductive particles.

4. The surface mountable thin film fuse assembly of claim 3, wherein: The conductive particles include silver.

5. The surface mountable thin film fuse assembly of claim 1, wherein: The thin film fuse track has a thickness in a Z direction that is less than 40 microns, the Z direction being perpendicular to the top surface of the substrate.

6. The surface mountable thin film fuse assembly of claim 1, wherein: The fuse layer also includes a contact pad electrically connected to the thin film fuse track, the contact pad extending to one of the first end or the second end of the substrate and electrically connected to one of the external terminals at the first end.

7. The surface mountable thin film fuse assembly of claim 6, wherein: The external terminal includes a first layer formed over the first end of the substrate and in electrical contact with the contact pad, and wherein the compliant layer is formed over the first layer.

8. The surface mountable thin film fuse assembly of claim 7, wherein: The first layer includes copper.

9. The surface mountable thin film fuse assembly of claim 1, wherein: The external terminal includes a plated layer on the compliant layer.

10. The surface mountable thin film fuse assembly of claim 9, wherein: The plating layer includes at least one of tin or nickel.

11. The surface mountable thin film fuse assembly of claim 1, wherein: The surface mountable thin film fuse assembly includes a protective layer formed over the fuse layer.

12. The surface mountable thin film fuse assembly of claim 11, wherein: The protective layer includes glass.

13. The surface mountable thin film fuse assembly of claim 1, wherein: The substrate includes glass.

14. The surface mountable thin film fuse assembly of claim 1, wherein: The surface mountable thin film fuse assembly is designed to blow if exposed to a maximum current in the range of 0.1A to 4A.

15. A method for forming a surface mountable thin film fuse assembly, the method comprising: providing a substrate having a first end and a second end spaced apart from the first end in a longitudinal direction; depositing a fuse layer formed over a top surface of the substrate, the fuse layer comprising a thin film fuse track; as well as An external terminal is formed along the first end of the substrate, the external terminal is connected to the fuse layer, the external terminal includes a compliant layer, the compliant layer includes a conductive polymeric composition, wherein: The fuse layer has a fuse layer thickness in a Z direction perpendicular to the top surface of the substrate; The compliant layer has a maximum compliant layer thickness in a longitudinal direction, the maximum compliant layer thickness being in a range of 10 micrometers to 200 micrometers; and A ratio of the maximum compliant layer thickness to the fuse layer thickness is in the range of 0.25 to 100.

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