WO2016145642A1

WO2016145642A1 - High interrupting current subminiature fuse and method of manufacture

Info

Publication number: WO2016145642A1
Application number: PCT/CN2015/074552
Authority: WO
Inventors: Sidharta Wiryana; Duren HUANG; Dacheng FENG
Original assignee: Cooper Technologies Company
Priority date: 2015-03-19
Filing date: 2015-03-19
Publication date: 2016-09-22

Abstract

A subminiature fuse includes a cap filled with a fluid arc extinguishing composition paste that, when assembled with a base and fuse element, coats the fuse element and provides a protective, arc extinguishing coating that improves reliability and increases a current interrupting capability of the fuse.

Description

HIGH INTERRUPTING CURRENT SUBMINIATURE FUSE AND METHOD OF MANUFACTURE

BACKGROUND OF THE INVENTION

The field of the invention relates generally to electrical circuit protection fuses and methods of manufacture, and more specifically to subminiature fuses for mounting to a circuit board of an electronic device and methods of manufacture that facilitate higher current interruption capability.

Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. Fuse terminals typically form an electrical connection between an electrical power source or power supply and an electrical component or a combination of components arranged in an electrical circuit. One or more fusible links or elements, or a fuse element assembly, is connected between the fuse terminals, so that when electrical current flow through the fuse exceeds a predetermined limit, the fusible elements melt and open one or more circuits established through the fuse to prevent electrical component damage.

In view of constantly expanding variations of electrical power systems, known electrical fuses are disadvantaged in some aspects. In particular, industry tends to provide higher performing fuses without changing the physical package size of the fuse relative to conventional fuses, or alternatively to provide higher performing fuses in a smaller physical package size than conventional fuses, presents practical challenges to electrical fuse manufacturers. High power, high current applications are becoming more prevalent in electrical power systems and are imposing increased demands on fuse manufacturers to provide fuses capable of performing in such applications within desired package size constraints.

In particular, increasingly powerful electronic devices are now highly desired in ever smaller package sizes. To facilitate a reduction in the size of more powerful electronic devices, the circuit boards and related components in the electronic devices must handle higher operating power in the same or reduced physical amount to space. This presents particular challenges to the manufacture of sub-miniature fuses that are mounted to circuit boards. Improvements are desired to meet the needs of the marketplace.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments are described with reference to the following Figures, wherein like reference numerals refer to like parts throughout the various drawings unless otherwise specified.

Figure 1 is a side elevational view of an exemplary embodiment of a subminiature fuse formed in accordance with an exemplary embodiment of the present invention.

Figure 2 is a cross sectional view of the subminiature fuse shown in Figure 1.

Figure 3 is a perspective view of a base for the subminiature fuse shown in Figure 1

Figure 4 is a first assembly view of the fuse shown in Figures 1 and 2 at a first stage of manufacture.

Figure 5 is a second assembly view of the fuse shown in Figures 1 and 2 at a second stage of manufacture.

Figure 6 is a third assembly view of the fuse shown in Figures 1 and 2 at a third stage of manufacture.

Figure 7 is a flowchart of a method of manufacturing a fuse as shown in Figures 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of subminiature fuses are described hereinbelow that advantageously overcome certain problems in the art. Specifically, exemplary embodiments of subminiature fuses and manufacturing methodology therefor is described herein that advantageously facilitate improved arc extinguishing capacity and, in turn, higher current breaking capacity in a compact package size. A sturdier subminiature fuse construction is also facilitated relative to known subminiature fuse constructions that improves reliability of the subminiature fuse in operation. Method aspects will be in part apparent and in part explicitly discussed in the description below.

Figure 1 illustrates an exemplary embodiment of a subminiature fuse 100 having a so-called radial fuse configuration that may be mounted to a circuit board 200 (shown in phantom in Figure 1) while occupying a small amount of space. The radial fuse configuration is one exemplary type of subminiature fuse that may benefit from the concepts described further below. Other types of subminiature fuse configurations are possible in other embodiments as described below.

In the radial fuse configuration shown, the fuse 100 includes a nonconductive base 102, a nonconductive protective cap 104, and conductive terminals in the form or a pair of

axial leads

106, 108 extending through and from a common side of the base 102 and cap 104 in the same direction for connection to the circuit board 200. The

leads

106, 108 are seen to extend from the base 102 in a spaced apart relation to one another and may be electrically connected to the circuit board 200 via well-known through-hole mounting and soldering techniques, for example. Such radial fuse configurations are used, for example, in combination with the circuit board 200 to protect power supplies, power adapters, and battery chargers for a variety of electronic devices that are becoming increasingly miniaturized yet more powerful devices. A fusible element 110 (Figure 2) extends across the base 102 and is connected to respective ends of the

axial leads

106, 108 via soldering techniques.

Unlike conventional subminiature fuses that have an interrupting current capacity less than about 100A, the subminiature fuse 100 can be provided with a substantially greater interrupting current capacity that is difficult, if not impossible, to achieve in conventionally fabricated subminiature fuses. Indeed, the construction of the subminiature fuse 100 described below renders it possible to interrupt currents as high as 300A in contemplated embodiments of the invention. This is due at least in part to improved arc extinguishing material and improved construction of the base 102 and protective cap 104 described below.

Certain types of conventional subminiature fuses utilize sand for arc quenching to improve breaking capacity relative to subminiature fuses that do not include such arc quenching material. In some cases, a mixture of sand and water glass is utilized for arc quenching purposes in subminiature fuses. Regardless, such conventional arc extinguishing material works well in lower current ranges, but for ratings of 100A and above that are now desired in the subminiature fuse 100, such conventional arc extinguishing material is insufficient to quench arc energy as the fuse element 110 opens. As the operating current increases, so does the intensity of electrical arcing and energy as it occurs, and if electrical arcing is not safely quenched by the arc extinguishing material the base 102 and cap 104 assembly can undesirably rupture and release arc energy to the ambient environment. Conventional arc quenching materials are inadequate in this regard.

As best shown in Figure 2, cap 104 defines an inner receptacle 112 that receives the fuse element 110 and the base 102. In combination, the base 102 and the protective cap 104 provide a sealed enclosure for the fuse element 110. As further explained below, the base 102, the fuse element 110 and

axial leads

106, 108 define a first subassembly of the subminiature fuse 100. The subminiature fuse 100 includes an arc extinguishing composition 114 injected in the receptacle 112 of the cap 104. The cap 114 and the arc extinguishing composition 114 define a second subassembly from a manufacturing perspective, and when the first and second subassemblies are combined, the arc extinguishing composition 114 surrounds the fuse element 110 inside the cap 104. The arc extinguishing composition 114 described below provides an increased interrupting current capacity of the subminiature fuse that is dramatically higher than conventional radial fuses, as well as other benefits described below.

In contemplated embodiments, the arc extinguishing composition 114 may include Bisphenol A (sometimes referred to as “BPA” ) as an arc quenching agent. In one contemplated example, the arc extinguishing composition 114 may include an arc quenching agent such as liquid epoxy BPA resin commercially available from, for example, the Epoxy Resin Division of Baling Petrochemical Co. Ltd. (www. epoxyresin. com. cn) . Such an arc quenching agent may be mixed with a binder to provide the arc extinguishing composition 114. The binder may be, for example, an inorganic binder such as sand and/or water glass and may be mixed with the BPA resin to form a paste that partially fills the cap receptacle 110. When the base 102 and fuse element 110 subassembly are installed to the cap 104 the fuse element 110 is therefore embedded in the paste.

In other contemplated embodiments, the arc extinguishing composition 114 may include alternative arc-quenching agents and/or alternative binder materials to those discussed above. Alternative quenching agents may include, for example only, melamine, guanidine, guanidine carbonate, guanine, and urea. The binder may be an inorganic binder such as sand or water glass or other known heat resistant material familiar to those in the art. The arc quenching composition 114 may likewise be formulated as a paste using such alternative quenching agents and binder materials, which advantageously facilitates dipping of the fuse element 110 into arc extinguishing composition 114 as the subminiature fuse 100 is assembled. The fuse element 110 after it has been soldered onto

leads

106, 108 is therefore coated with the arc extinguishing composition 114 in the form of paste as the fuse element 110 is immersed in the paste during assembly of the fuse 100.

To further enhance the interrupting current capability of the subminiature fuse 100, the base 102 and the cap 104 in contemplated embodiments may each be fabricated from, for example, a glass reinforced nylon resin material. In one contemplated example, the cap 104 and base 102 may each be fabricated from 30％glass reinforced nylon resin such as DuPont^TM

nylon resin and even more specifically from DuPont^TM

73GOL NC010 glass fiber reinforced polyamide 66 resin for injection molding. By virtue of such a reinforced base 102 and cap 104, in combination with the arc extinguishing composition 114 described above, the current breaking capacity improves significantly relative to conventional subminiature fuses.

In the exemplary embodiment shown, the cap 104 has a generally rectangular, box-like outer shape and profile defined by orthogonally arranged generally planar side walls. In other embodiments, however, other geometric shapes are possible. For example, the cap 104 may include a rounded side wall imparting a cylindrical profile to the fuse 100 rather than a rectangular one. Regardless of its geometric shape, the cap 104 defines a protective enclosure that receives the base 102 and the fuse element 110 that extends across the base 102 inside the receptacle 112 defined by the cap 104.

As seen in Figures 1 and 2, the axial leads 106, 108 extend axially from the base 102 in a generally parallel but spaced-apart relation to one another. Additionally, the

leads

106, 108 are positioned approximately equidistantly from an axial centerline 116 (Figure 2) of the cap 104, which coincides with an axial centerline of the base 102, both of which are generally indicated with centerline 116. Such orientation of the

leads

106, 108 is typical of a radial fuse configuration. Radial fuses are sometimes preferred for circuit board applications because of their smaller size or footprint when installed to a circuit board, although other configurations are likewise possible in other embodiments.

For example, in another embodiment of the subminiature fuse 100 the

leads

106, 108 may extend axially from opposing sides of the base 102 and/or the cap 104 with the leads extending in opposite directions to one another (e.g., to the left and to the right in the plane of Figure 1 instead of both leads 106, 108 extending downwardly as shown in Figure 1) . Such an alternative terminal lead configuration would require additional space on the circuit board than the radial fuse configuration illustrated, but may still nonetheless achieve at least some of the benefits of the present invention as described herein.

As another example, in an alternative embodiment of the subminiature fuse 100, surface mount terminals may be provided in lieu of the axial leads 106, 108. In such a surface mount embodiment of the fuse 100, for example, surface mount terminals may be provided in the form of end caps or ferrules, which would also increase the size of the subminiature fuse 100 relative to the radial fuse configuration illustrated. Such surface mount terminals would also increase the complexity and cost of the fuse for manufacture, but would nonetheless achieve at least some of the benefits of the present invention as described herein.

Figure 3 shows an exemplary base 102 for the subminiature fuse 100. The base 102 may be fabricated from an injection molded, nonconductive and reinforced material such as those described above into the generally shape illustrated or another shapes as desired. The base 102 may formed with opposing ends or

sides

120 and 122 interconnected by orthogonally arranged

side walls

126, 128, 130 and 132. In the embodiment illustrated the base 102 and the

sidewalls

126, 128, 130 and 132 define a generally elongated rectangular profile in the base 102, while in other embodiments the profile may be more or less elongated, or further may even be square or rounded in profile, including but not limited to a circular disk-shape. As such, while a specific configuration of the base 102 is shown, other configurations of the base may alternatively be utilized as desired.

The end 120 of the base 102 includes spaced apart and sloped cradle members 134 each defining a saddle area or receiving area for the ends of the

leads

106, 108 and the fuse element 110. The cradle members 134 are arranged in pairs on opposing lateral ends of the base 102 and form valley shaped saddle areas or receiving areas for the fuse element 110 and the ends of the

leads

106, 108 as described further below. When the base 102 including the fuse element 110 and the

leads

106, 108 is assembled with the cap 104, the end 120 of the base 102 is received within the hollow cap 104 such that the receiving area and the fuse element 110 are fully protected and enclosed by the cap 104, with the end wall of the cap 104 overlying the fuse element 110.

The end 122 of the base faces the circuit board 200 when the fuse 100 is installed thereto and is shown to include a projecting or protruding surface 136 on the end 122. The projecting surface 136 extends between openings or bores 138 formed through the base 102 between the opposing ends 120, 122 and also between each opposing pair of cradle members 134. As such, when the leads 106, 108 are extended through the bores 128, the projecting surface 236 extends in between the

leads

106, 108.

A protruding peripheral rib or flange 140 can also be seen in Figure 3 that is integrally formed with circumscribe the perimeter of the base 102 in the orthogonally arranged 126, 128, 130 and 132. The rib or flange 140 may provide an interlocking feature with the cap 104 when the subminiature fuse 100 is assembled. In some embodiments, however, the peripheral rib 140 may be considered optional and need not be provided.

Figure 4 and 5 illustrate assembly of the axial leads 106, 108 and attached fuse element 110 with the base 102. The axial leads 106, 108 in an exemplary embodiment may be conductive wire elements, stamped and formed metal elements, or combinations of both. Each of the

leads

106, 108 extends for a predetermined length between a proximal end 152 connecting to the fuse element 110 and an opposing distal end 154. The distal ends 154 may be inserted thought the through-holes 138 in the base 102 such that each lead 106, 108 is located proximate the cradle members 134 and extend completely though the base 102 between the end 120 and the end 122. The proximal end 152 of each lead 106, 108 may be shaped to facilitate connection to the fuse element 110 such as with a rounded eyelet shape imparting a hook-like appearance to the proximal ends 152 as shown in Figure 4. The distal ends 152 of each lead 106, 108 may be shaped before or after their assembly with the base 102 as shown in Figure 4. While exemplary leads 106, 108 are shown and described, other configurations of leads are possible and may be utilized.

As shown in Figure 5, the fuse element 110 may include an elongated fuse wire 160 that is spirally wound on an insulative former 162. The fuse wire 160 is connected to the proximal ends 152 of the axial leads 106, 108 via known soldering techniques. Optionally, once the fuse element 110 is inserted into the shaped ends 152, the ends 152 may be shaped or bent further around the ends of the fuse link 110 such that the fuse element 110 is positively captured or secured to the ends 152 of the

leads

106, 108. The ends of the fuse wire 160 defining the fusible element 110 and the

leads

106, 108 are soldered together to complete a mechanical and electrical connection between the fuse element wire 160 and the

leads

106, 108. As such, a current path is created through the subminiature fuse 100 wherein current may flow from line side circuitry 202 (shown in phantom in Figure 1) through the circuit board 200 and the fuse element 110 to load side circuitry 204 (shown in phantom in Figure 1) when the axial leads 106, 108 are terminated to the circuit board and the circuit is energized.

Once the fuse element 110 is mechanically and electrically connected to the

leads

106, 108 as described, the

leads

106, 108 are pulled through the base 102 in the direction of arrow A in Figure 5 until the ends of the

leads

106, 108 where attached to the fuse element 110 are received in the respective cradle members 134 of the base 102. The elements shown in Figure 5 thus define a first subassembly 170 in the construction of the subminiature fuse 100. The first subassembly 170 is then provided as shown in Figure 6 to complete the subminiature fuse construction as described below.

When the first subassembly 170 is completed, the fuse element 110 is mechanically and electrically connected to the proximal ends 152 of the

leads

106, 108 and extends across the end 120 of the base 102, spanning a distance between the cradle members 134 that provide a guide surface to receive the fuse element 110. The fuse element 110 extends generally transverse to the axial leads 106, 108. Alternatively stated, the fuse element 110 interconnects the axial leads 106, 108 in a substantially U-shaped arrangement, and when the fuse element 110 is seated in the cradle members 134, the fuse element 110 extends across the length of the end 120 of the base 102. The elongated base and the spiral wound fuse wire 160 facilitate increased current ratings of the subminiature fuse 100, although other base and fuse element configurations are possible while still achieving some of the advantages of the present invention.

In accordance with known electrical fuses, the fuse element wire 160 in the fuse element 110 is constructed to melt, vaporize, disintegrate or otherwise structurally fail when a predetermined magnitude of electrical current flows through the fuse for a duration of time, sometimes referred to as an overcurrent condition, that may damage sensitive electronic components in the load side circuitry 204 (Figure 1) . That is, the current path through the fuse element 110 is designed to fail and open the current path through the fuse element when subject to predetermined current conditions. By implication, when the fuse element 110 opens, an open circuit through the fuse 100 results and the line circuitry 202 is electrically isolated from the load circuitry 204 to prevent damage to sensitive circuit components in the load circuitry 204 that may otherwise occur from overcurrent conditions.

The amount of current that the fuse element 110 may sustain before opening the current path may vary depending on its particular material properties and dimensional aspects. Various fuses link or fuse element constructions are known for such a purpose and may be utilized as desired. That is, while an exemplary fuse element 110 has been described in relation to the illustrated examples in the Figures, it should be understood that a variety of different fuse elements are known that alternatively may be utilized to achieve particular opening characteristics of the subminiature fuse 100. Accordingly, the fuse element 110 need not include a fuse wire 160 in all embodiments. Further, when a fuse wire is included, it need not be spirally wound in all embodiments.

Figure 6 is a partial assembly view of the subminiature fuse 100 showing the first subassembly 170 before insertion into a second subassembly 180 including the cap 104 and arc extinguishing composition 114 described above. The receptacle 112 (Figure 2) of the cap 104 is filled with a predetermined amount of the arc extinguishing composition 114 described above that is preferably formed as a paste.

The cap 104 includes an open end 182 and a recessed opening 184 accessible from the open end 182. The open end 184 is sized and dimensioned to receive the base 102 of the first subassembly 170. The base 102 is shaped in a generally complementary manner in its outer profile to the open end 182 of the cap 104, and the base 102 and cap 104 may be dimensioned to provide a slight interference fit when the cap 104 and base 102 are assembled. In some embodiments, the cap 104 and base 102 may include interlocking, snap-fit attachment features such as the flange 140 (Figure 3) formed with the base 102 and a complementary slot 186 (Figure 2) formed into the open end 182 of the cap 104. In still further embodiments, other types of snap-fit features, latching features or other attachment features and techniques, including but not limited to adhesives and other elements known in the art may be utilized to provide secure attachment between the cap 104 and base 102 once assembled.

The recessed opening 184 in the open end 182 of the cap 104 provides access to the cap receptacle 112 both for inserting the arc extinguishing composition 114 discussed above and for inserting the lead end of the first subassembly 170 into the cap. When the cap receptacle 112 is pre-filled with the arc extinguishing composition 114 in a desired amount and in the form of paste as discussed above, the fuse element 110 is dipped into the arc extinguishing composition paste when the base 102 is inserted into the cap 102 via the recessed opening 184 in the direction of arrow B in Figure 6. The base 102 is inserted into the open end 182 and the fuse element 110 is inserted through the opening 184 and into the cap receptacle 112 until the end 122 of the base 102 is substantially flush with and closes the open end 182 as shown in Figures 1 and 2. The projecting or protruding surface 136 on the end 122 of the base 102 in between the

leads

106, 108 projects from the lower end of the cap 104 as also shown in Figure 1 and 2 and provides a stand-off surface when mounting the subminiature fuse 100 to the circuit board 200.

Preferably, the cap receptacle 112 is pre-filled with enough of the arc extinguishing composition 114 such that substantially the entire fuse element 110 is embedded in the paste as the subminiature fuse 100 is assembled. Ideally, enough of the arc extinguishing composition 114 is provided in the cap 104 to provide the second subassembly 180 such that the first subassembly 170 can be assembled without spillage of the arc extinguishing composition 114 as the first subassembly is inserted, while still completely covering the outer surfaces of the fuse element 110 with the arc extinguishing composition 114. The fluid arc extinguishing composition 114 is displaced when the fuse element 110 and the base 102 are dipped into it as the assembly is completed, so some empty space (i.e., space unfilled with the arc extinguishing composition paste) should be left to allow room for the paste to move around the fuse element 110 without being ejected from the assembly.

Once the subminiature fuse 100 is assembled, it may be cured in an air oven at, for example, 150℃ for 30 minutes. The arc extinguishing composition paste is dried and forms the protective coating over the fuse element 110 that facilitates vastly higher current interruption capability in use as well as improved reliability. The dried arc extinguishing composition 114 advantageously protects and secures the internal electrical connections of the fuse element 110 inside the cap 104 and prevents relative movement of the fuse element interface with the

leads

106, 108. In conventional subminiature fuses, vibration as the fuse is transported, vibration of the fuse in use, and/or vibration during handling of the fuse and manufacturing operations can sometimes compromise the internal electrical connections and present reliability issues for the fuse in operation. An epoxy arc quenching medium such as that described above provides significant assurance of the integrity of the electrical connection even when subject to rough handling and vibration in use and is more reliable than known subminiature fuse constructions in this aspect.

Also, during soldering of the

leads

106, 108 to a printed circuit board, transmitted heat has been sometimes known to cause re-melting of the soldered connection or seam between the fuse element 110 and the

leads

106, 108 in conventional subminiature fuses, which in turn may compromise the electrical connection and cause reliability issues. The arc extinguishing composition 114, especially those including epoxy arc quenching agents such as BPA, is heat resistant and mechanically stable, however, to reliably avoid these issues.

The subminiature fuses 100 including the arc extinguishing composition 114 are further manufacturable at relatively low cost while offering current interruption ratings of up to 300A, about three times the current interrupting capability of conventional subminiature fuses.

Figure 7 illustrates a method 300 of manufacturing the subminiature fuse 100 as shown and described.

The method 300 includes as shown the preparatory step of providing a base at step 302. The base provided may be the base 102 as shown and described above. The base provided may be injection molded from a material such as that described above. The step 302 of providing the base may include forming the base. Alternatively, the step 302 of providing the base may including acquiring the base or otherwise making it available for assembly of the fuse 100.

The method 300 further includes as shown the preparatory step of providing a cap at step 304. The cap provided may be the cap 104 as shown and described above. The cap provided may be injection molded from a material such as that described above. The step 304 of providing the cap may include forming the cap. Alternatively, the step 304 of providing the cap may include acquiring the cap or otherwise making it available for assembly of the fuse 100.

The method 300 further includes as shown the preparatory step of providing terminals at step 306. The terminals provided may be the terminal leads 106, 108 as shown and described above. The terminals provided may be fabricated from any of the materials or techniques described above. The step 306 of providing the terminals may include forming the terminals. Alternatively, the step 306 of providing the terminals may include acquiring the terminals or otherwise making them available for assembly of the fuse 100.

The method 300 further includes as shown the preparatory step of providing a fuse element at step 308. The fuse element provided may be the fuse element 100 as shown and described above. The step 308 of providing the fuse element may include forming the fuse element. Alternatively, the step 308 of providing the fuse element may include acquiring the fuse element or otherwise making it available for assembly of the fuse 100.

The method 300 further includes as shown the preparatory step of providing an arc extinguishing composition at step 310. The arc extinguishing composition provided may be the arc extinguishing composition 114 as shown and described above. The step 310 of providing the fuse element may include forming the arc extinguishing composition including selecting and mixing of the arc quenching and binder ingredients in the amounts or proportions desired to form an arc extinguishing composition paste that is fluid or flowable to facilitate the assembly described. In some embodiments that paste may be a semi-solid, fluid material depending on the particular ingredients and proportions selected. Alternatively, the step 310 of providing the arc extinguishing composition may include acquiring the arc extinguishing composition or otherwise making it available for assembly of the fuse 100.

At step 312, the terminals provided at step 306 are assembled to the base provided at step 302 as shown and described in relation to Figure 4. The proximal ends 152 of the terminal leads 106, 108 may be shaped in advance per step 306 or may be shaped as part of the assembly step 312.

At step 314, the fuse element provided at step 308 is connected to the terminals assembled at step 312 via soldering techniques. The step 308 may include drawing the terminals through the base after the fuse element is connected in the direction of arrow A shown in Figure 5. Upon completion of

steps

312 and 314, the first subassembly 170 as shown in Figures 5 and 6 is completed.

At step 316, the cap is filled with a desired amount of the arc extinguishing composition provided at step 310. The flowbable fluid material may be injected or otherwise introduced into the receptacle of cap through the opening on the open end of the cap as described above in any manner desired for purposes of the step 316. Once step 316 is completed, the second subassembly 180 as described in relation to Figure 6 is completed.

At step 318 the base assembly from step 314 is inserted into the cap from step 316. As this is done, the fuse element is immersed in the arc extinguishing composition paste as described above. The fuse element is dipped into the fluid arc extinguishing composition and is coated by the arc extinguishing composition paste as the assembly is made.

At step 320, the assembly of step 318 is cured. The subminiature fuse 100 is now complete and optionally may be tested prior to its installation to the circuit board 200.

The method 300 as shown and described is exemplary only. The steps as shown may be performed in a different order. Certain steps may be consolidated or omitted, while still other steps may be added. Nonetheless, the method 300 as shown and described illustrates one way to manufacture the subminiature as shown and described using a relatively small number of steps and a straightforward manufacturing process that facilitates production of a high performance subminiature fuse 100 having the benefits described at relatively low cost.

The benefits and advantages of the invention are now believed to have been amply illustrated in relation to the exemplary embodiments disclosed.

An embodiment of a subminiature fuse has been disclosed including a first subassembly and a second subassembly. The a first subassembly comprises a nonconductive base defining an external receiving surface, a fuse element assembled to the external receiving surface, the fuse element including a first end and a second end, and first and second terminals soldered to the respective first and second ends of the fuse element. The second subassembly comprises: a cap defining a receptacle, and an arc extinguishing composition in the receptacle. When the second subassembly is assembled to the first subassembly, the fuse element and the first and second ends are extended into the arc extinguishing composition. The receptacle encloses the fuse element and the receiving surface.

Optionally, the arc extinguishing composition may include an epoxy. The epoxy may include Bisphenol A.

The arc extinguishing composition may also optionally include an arc extinguishing agent selected from the group of an epoxy, melamine, guanidine, guanidine carbonate, guanine, and urea. The arc extinguishing composition may further include a binder. The binder may comprise an inorganic binder. The inorganic binder may comprise water glass.

As further options, the first and second terminals may include terminal leads extending through the nonconductive base and projecting from the nonconductive base opposite the receiving surface for through-hole mounting to a circuit board. The fuse element may be wound on an insulative former. The first and second terminals may extend perpendicularly to a longitudinal axis of the former.

The fuse may element extend spirally between the first and second ends. The first and second terminals may each include respective cradles to receive the fuse element. The base may include a plurality of cradles receiving the fuse element. The conductive base and the cap may each fabricated from a glass reinforced nylon resin.

A method of fabricating a subminiature fuse has also been disclosed, including: assembling a fuse element to an external receiving surface of a nonconductive base； filling at least a portion of a receptacle defined in a cap with a fluid arc extinguishing composition； and assembling the cap to the nonconductive base, whereby the fuse element is dipped into and coated by the fluid arc extinguishing composition.

Optionally, filling the receptacle of the cap with a fluid arc extinguishing composition may comprise filling at least a portion of the receptacle of the cap with an arc extinguishing composition paste including epoxy. The epoxy may include Bisphenol A. Filling at least a portion of the receptacle of the cap with a fluid arc extinguishing composition may include filling at least a portion of the receptacle of the cap with an arc extinguishing composition paste including an arc extinguishing agent selected from the group of an epoxy, melamine, guanidine, guanidine carbonate, guanine, and urea. The arc extinguishing composition may further include a binder. The binder may include an inorganic binder. The inorganic binder may include water glass.

Assembling the fuse element to the external surface of a nonconductive base may comprise: respectively soldering a first end and a second end of the fuse element to first and second terminals. The method may also include extending the first and second terminals through the nonconductive base.

The fuse element may be wound on an insulative former, and the fuse element may extend spirally between the first and second ends. The method may further include receiving the fuse element in respective cradles of first and second terminals. The method may also include receiving the fuse element with a plurality of cradles projecting from the nonconductive base and defining the receiving surface. The nonconductive base may be fabricated from a glass reinforced nylon resin material. The cap may be fabricated from a glass reinforced nylon resin material. The method may also include curing the assembly.

An embodiment of a subminiature fuse may be manufactured according to the method above.

An embodiment of a subminiature fuse has also been disclosed including: a nonconductive base fabricated from a reinforced resin material； a former element； a fuse element spirally wound on the former element, the fuse element and former element assembled to and exposed upon a surface of the nonconductive base, the fuse element including a first end and a second end； first and second terminals soldered to the respective first and second ends of the fuse element； and a cap fabricated from a reinforced resin material and defining a receptacle filled with an arc extinguishing composition comprising Bisphenol A； wherein when the cap is assembled to the nonconductive base the receptacle encloses the fuse element and the external surface and the arc extinguishing composition coats the fuse element and the first and second ends.

Optionally, the reinforced resin material comprises a glass reinforced nylon resin material. The fuse may have an interrupting rating greater than 100A. The fuse may be configured as a radial fuse.

An embodiment of an electrical fuse has also been disclosed including: a nonconductive housing defining a receptacle； a fuse element received in the receptacle； and an arc extinguishing composition filling the receptacle around the fuse element； wherein the arc extinguishing composition comprises Bisphenol A.

Optionally, the nonconductive housing comprises a base and a cap assembled to the base, each of the cap and base fabricated from a glass reinforced nylon resin material. The fuse may have an interrupting rating greater than 100A. The fuse may be configured as a radial fuse.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

A method of fabricating a subminiature fuse, comprising

assembling a fuse element to an external receiving surface of a nonconductive base；

filling at least a portion of a receptacle defined in a cap with a fluid arc extinguishing composition； and

assembling the cap to the nonconductive base, whereby the fuse element is dipped into and coated by the fluid arc extinguishing composition.
The method of claim 1, wherein filling the receptacle of the cap with a fluid arc extinguishing composition comprises filling at least a portion of the receptacle of the cap with an arc extinguishing composition paste including epoxy.
The method of claim 2, wherein the epoxy includes Bisphenol A.
The method of claim 1, wherein filling at least a portion of the receptacle of the cap with a fluid arc extinguishing composition comprises filling at least a portion of the receptacle of the cap with an arc extinguishing composition paste including an arc extinguishing agent selected from the group of an epoxy, melamine, guanidine, guanidine carbonate, guanine, and urea.
The method of claim 4, wherein the arc extinguishing composition further includes a binder.
The method of claim 5, wherein the binder comprises an inorganic binder.
The method of claim 6, wherein the inorganic binder comprises water glass.
The method of claim 1, wherein assembling the fuse element to the external surface of a nonconductive base comprises:

respectively soldering a first end and a second end of the fuse element to first and second terminals.
The method of claim 8, further comprising extending the first and second terminals through the nonconductive base.
The method of claim 1, wherein the fuse element is wound on an insulative former, and wherein the fuse element extends spirally between the first and second ends.
The method of claim 1 further comprising receiving the fuse element in respective cradles of first and second terminals.
The method of claim 1, further comprising receiving the fuse element with a plurality of cradles projecting from the nonconductive base and defining the receiving surface.
The method of claim 1, wherein the nonconductive base is fabricated from a glass reinforced nylon resin material.
The method of claim 1, wherein the cap is fabricated from a glass reinforced nylon resin material.
The method of claim 1, further comprising curing the assembly.
A subminiature fuse comprising:

a nonconductive base fabricated from a reinforced resin material；

a former element；

a fuse element spirally wound on the former element, the fuse element and former element assembled to and exposed upon a surface of the nonconductive base, the fuse element including a first end and a second end；

first and second terminals soldered to the respective first and second ends of the fuse element； and

a cap fabricated from a reinforced resin material and defining a receptacle filled with an arc extinguishing composition comprising Bisphenol A；

wherein when the cap is assembled to the nonconductive base the receptacle encloses the fuse element and the external surface and the arc extinguishing composition coats the fuse element and the first and second ends.
The fuse of claim 16, wherein the reinforced resin material comprises a glass reinforced nylon resin material.
The fuse of claim 17, wherein the fuse has an interrupting rating greater than 100A.
The fuse of claim 18, wherein the fuse is configured as a radial fuse.
An electrical fuse comprising:

a nonconductive housing defining a receptacle；

a fuse element received in the receptacle； and

an arc extinguishing composition filling the receptacle around the fuse element；

wherein the arc extinguishing composition comprises Bisphenol A.