MXPA97009973A - Method and apparatus for a mountable device on a surface for protection against electrostatic damage to components electroni - Google Patents

Abstract

A surface-mount, thin-film fusible switch that has two material subassemblies. The first sub-assembly includes a fuse link, its support substrate and terminal contacts. The second sub-assembly includes a protective layer that covers the fusible link to provide shock and oxidation protection. The protective layer is preferably made of a polymeric material. The most preferred polymeric material is a polyurethane gel or paste. In addition, the most preferred support substrate is an epoxy FR-4 or a polyimi

Description

METHOD AND APPARATUS IMPROVED FOR ON DEVICE FUSE MOUNTED ON A SURFACE r-s-n-pr. Technician The invention is generally related to a fusible switch mountable on a surface for placement in and for protection of the electrical circuit of a printed circuit board. Related Application The present application is a continuation in part of the Serial US Application No. 08 / 247,584, filed May 27, 1994. Background of the Invention The printed circuit boards (CI) have found increasingly application in electrical equipment and electronic of all types. The electrical circuits formed of these Cl slats, as conventional large-scale integration electric circuits, need protection against electrical overloads. This protection is typically provided by subminiature fuse switches that are physically secured to the Cl-board. An example of such miniature fuse switch for surface mounting is disclosed in the U.S. patent No. 5,166,656 ('656 patent). The fusible link of this surface-mounted fuse switch is disclosed to be covered with a 3-layer composite which includes a passivation layer, an insulating cover, and an epoxy layer to join the passivation layer with the insulating layer. See the '656 patent, column 6, lines 4-7. Typically, the passivation layer is either a chemically deposited silica layer or printed glass. See the '656 patent, column 3, lines 39-41. The insulating cover can be a glass cover. See the '656 patent, column 4, lines 43-46. The fuse switch of the patent. '656, has 3 layers that protect its fusible link. In addition, the fuse switch of the '656 patent has a relatively thick glass cover. There are other diverse characteristics in the fuse switch of the '656 patent which are unnecessary in the present invention. In this way, the present invention is designed to solve these and other problems. The invention is a fuse switch mounted on a thin film surface, which comprises two sub-assemblies of material. The first subassembly comprises a fusible link, its support substrate and terminal contacts. The second subassembly comprises a protective layer that is superimposed on the fusible link to provide shock and oxidation protection. The protective layer is preferably made of a polymeric material. The most preferred polymeric material is a polyurethane gel or paste when the printing step on stencil or stencil is used to apply the covering coating. However, polycarbonates will also work well when the injection molding step is used to apply the cover layer. In addition, the most preferred support substrate is an epoxy FR-4 or a polyimide. A second aspect of the invention is a thin film surface mounted fusible switch. This fuse switch comprises a fusible link made of a conductive metal. The first conductive metal is preferably but not exclusively selected from the group including copper, silver, nickel, titanium, aluminum or alloys of these conductive metals. A second, conductive metal different from the first conductive metal is deposited on the surface of this fusible link. A preferred metal for the surface mounted fusible switch of this invention is copper. A second preferred conductive metal is e, tin, lead. Another preferred second conducting metal is tin. The second conductor metal can be deposited in the fusible link in the form of a rectangle, circle or in the form of any other configuration, depending on the configuration of the fusible link. The second conductive metal is preferably deposited along the central portion of the fusible link. Photolithographic processing techniques can be used, mechanics and lasers to create very small, intricate and complex fusible link geometries. This ability, when combined with extremely thin film coatings applied through electrochemical deposit and physical vapor (PVD) techniques, allows these subminiature fuse switches to control the fuse area of the element and protect the circuits from the passage of currents in The range of microamps and amps that passes This is unique, in that the previous fuse switches provide protection to these high currents were made with filament wires. The manufacture of such fuse switches with filament wires created certain difficulties in handling. The location of the fusible link on the top of the substrate of the present fusible switch allows anyone to use laser processing methods as a secondary high-precision operation, thereby trimming the final resistance value of the fusible element. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of an epoxy sheet FR-4 plated with copper, used to make a surface mounted subminiature fuse switch. Figure 2 is a view of a portion of the figure 1, taken along lines 2-2 of Figure 1. Figure 3 is a perspective view of epoxy FR-4 of Figure 1, but devoid of its copper plating, and with a plurality of holes. { shown coaxially), each has a separate procedure for a length L a width W and oriented in separate quadrants of that sheet. Figure 4 is an enlarged perspective view of a sectional portion of the perforated sheet of Figure 3, but with a layer of copper sheet that has been reapplied. In Figure 5 is a perspective view of a cut away from the flat surfaces, the upward facing surfaces of the re-plated copper sheet, after the sheet was masked with a multi-square panel of an opaque substance to the light ultraviolet (UV '.. Figure 6 is a perspective view of the reverse side of Figure 5, rotated about one of the rows of fusible switch 27, but after removal of a strip-like portion of the copper bath from the sheet Figure 5 is a perspective view of the upper part of Figure 6, rotated around one of the rows of fusible switch 27, and showing linear regions 40 defined by dotted lines. 8 is a perspective view of a single fuse switch row .27 of the sheet, in the offset cut of the other rows, and in cut off offset on the edge of the fuse switches, after immersing the sheet in a water bath. copper plating and then in a liquid plating bath, with the result that the copper and nickel layers were deposited on it; copper base layer of terminal contacts; including contact slots. Fig. 9 is a perspective view of the strip of Fig. 8, but before curing with light V, and showing a portion of fused fusible switches 50 in the center of the fusible link 42 which is masked with a substance opaque to the light V. Figure 10 shows the strip of figure 9, but after immersion in a tin-lead plating bath to create another layer on the copper and nickel layers, and after depositing a tin alloy- lead in the central portion of the fusible link. Figure 11 shows the strip of Figure 10, but with a layer of polymeric gel or paste on top of the row of fusible switches 27. Figure 12 shows that the individual fuse switch is finally manufactured, and after a This operation is called a square cut in which a diamond saw is used to cut the strips in parallel and perpendicular planes to form these individual fuse switches that can be mounted on surfaces. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS While this invention is capable of materializing in many different ways, it is shown in the drawings and a preferred embodiment of the invention will be described in detail here. It is understood that the present disclosure should be considered as an exemplification of the invention. This disclosure is not intended to limit the broad aspect of the invention to the embodiment or embodiments illustrated. A preferred embodiment of the present invention is shown in Figure 12. The thin film fuse switch mounted on the surface is a subminiature fuse used in a surface mount configuration on a Cl board or a thin film hybrid circuit. One of these fuse switches is commonly known in the art as an "A" case fuse. The case fuse switch "A" is also designated as a fuse switch 1206. In addition, the present invention includes even smaller fuse switches which are compatible with standard size surface mount devices. In particular the present invention can be used, within all standard sizes of such sizes of surface mounted device, such as 120109, 0805, 0803 and 0402 fuse switches, as well as non-standard sizes. The invention generally comprises two sub-assemblies of material. As may be noted the first subassembly includes the fusible element or fusible link 42, its support substrate or core 13 and terminal contacts 34 and 36 for connecting the fuse switch 58 to the Cl-board. The second sub-assembly is a protective layer 56, which covers the fusible link 42 and a substantial portion of the upper portion of the fuse, to at least provide protection from impacts which may occur during automated assembly and protection against oxidation during use . The first subassembly contains and supports two metal electrodes or contacts 34, 36 and the fusible link 42, which are attached to the substrate as a single continuous film as shown in Figure 5. The contacts 34, 36 are located in the upper part, the lower part and the sides of the substrate or core 13, while the fusible link 42 is located in the upper part of the substrate 13. More specifically, the contacts 34, 36 extend into the grooves 16 (each groove 16). is one half of each hole 14) in each fuse switch created by the holes 14 and the dicing operation during the manufacturing process, as will be described further below. As will be seen, in the preferred embodiment, the contacts are made of several layers, including a copper base layer, a complementary copper layer, a nickel layer and a tin-lead layer. The base copper layer of the contacts and the thin film fusible link are deposited simultaneously by (1) electrochemical processes, such as the veneer described in the preferred embodiment below; or (2) by PVD. Such a simultaneous deposit ensures a good conductive path between the fusible link 42 and the terminal contacts 34, 36. This type of deposits also facilitates manufacturing and allows very precise control of the. thickness of the fusible link 42. After placement of the fusible link 42 and the base copper in the substrate 13, additional layers of a conductive material are placed in the terminal contacts 34, 36. - These additional layers could be defined and placed on these contacts through photolithography and deposit techniques, respectively. This fuse switch can also be made by the following procedures. Shown in Figures 1 and 2, a solid sheet 10 of an epoxy FR-4 with copper plating 12. The copper plating 12 and the epoxy core 13 FR-4 of this solid sheet 10 can be seen better in the figure 2. This epoxy sheet FR-4 coated with copper 10 is for sale from Allier Signal Laminate Systems, Hoosick Falls, New York, as part No 0200BEDI30C1 / C1GFN0200C1 / C1A2C. Although epoxy FR-4 is a preferred material, other suitable materials include any material that is compatible with it, for example of a physical and structurally similar chemical nature, to the materials from which the Cl tablets are made. In this manner, another suitable material for this solid sheet 10 is polyimide. FR-4 epoxy and polyimide are among the class of materials that have physical properties that are closely identical with the standard substrate materials used in the Cl-tablet industry. As a result, the fuse switch of the invention and the Cl plate to which the fuse switch is secured, have extremely well-compatible technical and mechanical properties. The substrate of the fuse of the present invention also provides desired characteristics of arc formation, and simultaneously exhibits sufficient mechanical flexibility / to remain intact when exposed to rapid release, de-energies associated with arc formation. In the next step of the manufacturing process of the fuse switches of the present invention, the copper bath plating 12 is. etching of the solid sheet 10 by a conventional etching process. In these conventional etching processes, copper is etched from copper by a ferric chloride solution. Although it is understood that after the completion of this step, all the copper layers 12 of Figure 2 are etched from the epoxy core 13 ER-4 of this solid sheet 10, the remaining epoxy core 13 of this sheet 10 of epoxy FR -4 is different from a "clean" sheet of epoxy FR-4 that has not been initially treated with a copper layer. In particular, a chemically etched surface treatment remains on the surface of the epoxy core 13 after the copper layer 12 has been removed by etching. The treated surface of the epoxy core 13 is more responsive to subsequent operations that are necessary in the manufacture of the present surface mounted miniature fuse switch. The FR-4 epoxy sheet 10 having this treated surface free of copper, and untreated, is then perforated to create holes or holes 14 along 4 quadrants 10a, 10b, 10c, 10d of the sheet 10, as see Figure 3. The dotted lines separate these four quadrants 10a, 10b, 10c, 10d in Figure 3. It should be noted further that in Figure 3, the holes 14 are aligned in rows 27 and columns 29. Although only 4 rows 27 of the holes 14 are shown in figure 3 in a quadrant 10a for convenience, the rows 27 of the holes 14 are actually arranged over almost the entire sheet 10 in the four quadrants 10a, 10b, 10c, 10d, as designated for the three dotted lines ll. For the standard size "603" of the surface mounted devices mentioned above, the length L between the center of the cores of the holes 14 is approximately 1778 micras (70 mils) and the width W between the center of the holes 14 is approximately 127 microns (50 mils), and the width W between the center of holes 14 is approximately 762 microns (30 mils). Again, the standard size may and the non-standard sizing are possible for the present invention. The diameter of Figure 4 for each hole 14 for size "603" is approximately 457 microns (18 mils). When the perforation of the barriers 14 has been completed, the engraved and perforated sheet 10 shown in Figure 3 is again plated with copper. This copper re-application occurs through immersion of the engraved and perforated sheet of Figure 3 in a copper plating bath. This method of copper plating is well known in the art. This copper-plating step results in the placement of a copper layer 'having a uniform thickness through each of the exposed surfaces of the sheet 10. For example, as can be seen in Figure 4, the copper plating 18 resulting from this step covers both (1) the flat upper surfaces 22 of the sheet 10; and (2) the vertical regions of the grooves 16 and / or the vertical regions of the holes 14. This vertical portion of the grooves 16 and / or holes 14 must be plated with copper until they finally form a portion of the contacts 34. , 36 of the final fuse switch as will be described below. The uniform thickness of the veneer will depend on the user's ultimate needs. Particularly, as can be seen in Figure 4, for a fuse switch designed to be opened in 1/16 amp, the copper plated 18 has a thickness of 2500 Angstroms. For a fuse switch intended to open at 5 amps, the copper plate 18 has a thickness of approximately 75,000 Angstroms for a particular width of the fusible link. After the veneering has been completed, to access the copper-plated structure of Figure 4, the fully exposed surface of this structure is covered with a so-called photosynthetic polymer. A clear mask is placed in another case on the copper-plated sheet 20 of FIG. 4 after it has been covered with the photoresistor. Square panels are part of and are evenly separated through this transparent mask according to the size of the fuse switch that is being manufactured. These square panels are made of an opaque substance a. UV light, and is generally shown as the rectangle 30 shown in Figure 5. Essentially, by placing this mask having these panels on the sheet 20 re-plated with copper, with several portions of the flat surfaces facing upwards 22 of the re-plated copper sheet 20 of Figure 4 are effectively shielded from the UV light examples. It is understood that the following discussion of these square panels will essentially define the shapes and sizes of the so-called fuse links 42 and the upper terminal areas 60 of the terminal contacts 34, 36 in the upper portion of the fusible switch. The fusible link 42 is in electrical communication with the upper terminal areas 60. It will be appreciated that the width, length and shape of both the fusible link 42, and these terminal areas 60, may be altered to resize and. form of these panels opaque to UV light. Additionally, the back side of the sheet is covered with a photo-resistant material and in another case a transparent mask is placed over the copper-plated sheet 20 after it has been covered with the photoresistor. A rectangular panel is part of this transparent mask. The rectangular panels are made of a substance opaque to UV light and are of a size corresponding to the size of the panel 18 shown in Figure 6. Essentially, by placing this mask having these panels on the re-plated copper sheet. , several strips of the upwardly facing flat surfaces 28 of the re-plated copper sheet 20 are effectively shielded from the effects of UV light. The rectangular panel will essentially define the shapes and sizes of the lower end areas 62 of the terminal contacts 34, 36 and the lower middle portions 28 of the sheet 20, as shown in Figure 6. The copper plating of a portion of the side inner of sheet 20 is defined by a photo-resistant mask. Particularly, the copper plating of the middle, lower portions 28 of the inner side of the sheet 20 is removed. The lower middle portions 28 of the inner side of the sheet 20 are that part of the strip along a line immediately below the transparent epoxy areas 30 and fusible links 42. A perspective view of this sheet re- plated 20 is shown in Figure 6. The entire re-veneered sheet covered with photoresistor 20, ie the top, bottom and sides of that sheet, is then subjected to UV light. The re-veneered sheet 20 is subjected to UV light for a sufficient time to ensure curing of the entire photoresistor that is not covered by the square panels and rectangular shots of the masks. After that, the masks containing these square panels and rectangular strips are removed from the re-veneered sheet 20. The photoresistor that was previously under these square panels remains uncured. This uncured photoresistor can be washed from the re-veneered sheet 20 using a solvent. The photoresistor cured on the rest of the re-veneered sheet 20 provides protection against the next stage in the process. In particular, the cured photo-resistor prevents the removal of copper under those areas of cured photo-resistor. The regions initially below the square panels do not have cured photo-resistor or such protection. Thus, the copper of these regions can be removed by engraving. This engraving is done with a ferric chloride solution through well-known engraving concepts. After the copper has been removed, as can be seen in Figures 5 and 6, the regions originally below the square panels and the rectangular strips of the mask are not completely covered. Instead, these regions now comprise transparent epoxy areas 28 and 30. The re-veneered sheet 20 is then placed in a chemical bath to remove all of the remaining cured resistor from the previously cured areas of that sheet 20. After the completion of several operations described in that specification, this sheet 20 will be cut off by last in a plurality of pieces and each of these pieces will become a switch, fuse according to the invention, as will be described further below.

However, for the sake of brevity only a portion of cut off of the entire sheet including three rows and four columns 29 are shown in Figures 5 to 7.

Also seen from Figures 5 to 7, the holes 14 and the slots of the sheet 20 still include copper plating.

These holes 14 and grooves 16 form part of the contacts 34-36. Those contacts 34-36 will ultimately serve as the means to secure the entire fuse, terminated for the Cl tablet. Figure 7 is a perspective view of the opposite side of the sheet 20 of Figure 6. Directly opposite and coinciding with the lower middle portions 28 of the sheet 20, are the linear regions 40 on the upper side 38 of the sheet 20. These linear regions 40 are defined by the dotted lines of Figure 7. Figure 7 is to be referred to in connection with the next step in the manufacture of the invention. In this next step a photoresist polymer is placed along each of the linear regions 40 between the upper side of the sheet 20. By covering these linear regions 40, a photoresisting polymer is also placed. length of the relatively thin portions which comprise the fusible links 42. These fuse links 42 are made of a conductive material, here, copper. The photoresist polymer was treated with UV light, resulting in curing of the polymer in the linear region 40 and its fusible links. As a result of the curing of this photoresistor in the linear region 40 and its fuse links 42, the metal will not adhere to this linear region 40 when the sheet 20 is immersed within the electrolytic bath, which contains a metal for the purpose of plating. In addition, as explained above, the middle portion 28 of the underlying side of the sheet 20 will also not be subjected to plating when the sheet 20 is subjected to the electrostatic bath. The copper metal that previously covered this metal portion had been removed, revealing the epoxy bar that forms the base of the sheet 20. The metal does not adhere to, or plate in, this bar epoxide using an electrolytic plating process. The whole sheet 20 is immersed in a silver plating bath to a copper electrolytic plating bath and then to a nickel electrolytic bath. As a result, as can be seen in Figure 8, a copper layer and a layer of nickel were deposited on the copper layer of the base 44. After deposition of these copper and nickel 48 layers, the photoresist polymer cured on the linear region 40, including the photoresist polymer on the fusible link, is removed from this region. Photoresistor polymer is then applied through the entire region 40. As can be seen in Figure 9, however, a portion 50 in the center of the fusible link 42 was masked with an opaque substance in UV light. The linear input region 40 is then subjected to UV light, with the result that the cure of the photoresist polymer occurs throughout that region, except in the masked central portion 50 of the fusible link 42. The mask is removed from the portion 50 of the fusible link, and sheet 20 is rinsed. As a result of this rinsing, the photoresistor above the central portion 50 of the fusible link 42 is removed from the fusible link 42. The photoresistor cured together with the remainder of the linear region 40 nevertheless remains.

Metal plating will not occur on the portion of the sheet 20 covered by the cured photoresistor. Due to the absence of photoresistor of the central portion 50 of the fusible link 42, however, this central portion 50 can be metal plated. When the strip shown in Figure 9 is immersed in a tin-lead electrolytic plating bath , a tin-lead layer is superimposed on the lead layer 46 (FIG. 10) and the nickel layers 48. A tin-lead drop 54 is also deposited on the surface of the fusible link 42, that is to say placed essentially by an electrolytic plating process in the central portion 50 of the fusible link 42. This electrolytic plating process is essentially a thin film deposition process. It is understood, however, that this tin-lead can also be added to the surface of the fusible link 42 by a lithography process or by means of a fixed vapor deposition process, such as sizzle or evaporation in a high vacuum reservoir chamber. . This droplet 54 is comprised of a second conductive metal, for example tin-lead or tin, which is not similar to the copper metal of the fusible link 42. This second conductive metal in the form of a tin-lead drop 54 is deposited on the fusible link 42 in the form of a rectangle. The tin-lead drop 54 on the fusible link 42 provides this with certain advantages. First, the tin-lead drop 54 melts under conditions of current overload, creating a fusible link 42 that becomes a tin-lead-copper alloy. This tin-lead-copper alloy results in a fusible link that has a lower melting temperature than copper alone. The lower melting temperature reduces the operating temperature of the fuse switch device of the invention, and this results in improved device performance. Although a tin-lead alloy is deposited on the copper fusible link 42 in this example, it will be interpreted by those skilled in the art that other conductive metals can be placed on the fusible link 42 to lower its melting temperature, and that the fusible link 42 itself can be made of conductive metals other than copper. In addition, the tin-lead alloy or other metal deposited on the deposit link 42 need not be rectangular in shape, but may be of any number of additional configurations. The second conducting metal can be placed in a sample section of the link or in the holes or gaps of the link. Fusible parallel links are also possible. As a result of this flexibility, specific electrical characteristics can be engineered within the fuse switch to meet various needs of the end user.

As indicated above, one of the possible fusible link configurations is a serpentine configuration. By using a coil configuration the length of the fusible link can be increased, although the distance between the terminals on opposite sides of that link remains the same. In this way, a serpentine configuration provides a larger fusible link without increasing the dimensions of the fusible switch itself.

* The next stage in the manufacture of the device of the invention is the placement through a significant portion of the upper portion of the sheet 20 between the terminal contacts 34, 36 of the protective layer 56 (FIG. eleven) . This protective layer 56 is the second sub-assembly of the present fusible switch and forms a relatively hermetic seal on the portion of the upper part of the sheet where the fusible link 42 exists. In this way, the protective layer 56 inhibits the corrosion of the fusible link 42 during its lifetime of use. The protective layer 56 also provides protection against oxidation and shock during fastening to the Cl-board. This protective layer also serves as a means to provide a surface for lifting and laying operations in which they use a vacuum lifting tool. This protective layer 56 helps to control melting, and ionization and electric arc from occurring in the fusible link 42 during overload conditions. The protective layer 56 or cover coating material provides desired arc extinguishing characteristics, especially important under the interruption of the fusible link 42. The protective layer 56 may also be comprised of a polymer, preferably a gel or polyurethane paste when use a template or cliché printing operation to apply the cover coating. A preferred polyurethane is made by Dymax Corporation. Other gels, pastes or similar adhesives are suitable for the invention. In addition to the polymers, the protective layer 56 may also be comprised of conformational and epoxy coatings. This protective layer 56 is applied to the strip 26 using a template or cliché printing process, which includes the use of a common template or cliché printing machine. In the past, an injection of the material into a die mold was performed while the sheet 20 was held between the two dies. However, template or cliché printing is a much faster process. Specifically, it has been found that the use of a template or cliché printing process while using a template or cliché printing machine, at least, double output outputs of the number of fusible switches from a previous punching operation. The template or cliché printing machine is manufactured by Affiliated Manufacturers, Inc. of Northbranch, New Jersey, Model No. PC-885. In the template or cliché printing process, material is applied to the sheet 20 in strips simultaneously, instead of two strips at a time in the die / injection molding process. As will be explained later, the material cures much faster than the injection-filling process because in the template or cliché printing process, the cover coating material is completely exposed to the UV radiation of the lamps in opposition to the injection filling process where there is a filter to which the energy of the lamp must be transmitted to the coating itself since the mold acted as a filter itself. In addition, the template or cliché printing process produces a more uniform cover coating than the injection-fill process, in terms of the height, the width of the cover coating. Due to this uniformity, fuse switches can be tested and packaged automatically. With the injection filling process it is sometimes more difficult to accurately align the fusible switches in the test and packaging equipment due to some non-uniform heights and widths of the cover liner.

The template or cliché printing machine comprises a slide plate:, 70, a base 72, a roller arm 74, a rubber roller 76, and a cover 78, the cover 78 is mounted on the base 72 and the roller rubber 76 is movably mounted on the roller arm 74 above the base 72 and the cover 78. The plate 70 is slidable below the base 72 and the cover 78. The cover 78 has parallel openings 80 which correspond to the cover coating width 56. The template or stencil printing process begins by attaching an adhesive tape under the fusible sheet 20. The fuse sheet 20 is placed on the plate 70 with the adhesive tape 70 and the fuse sheet 20. The cover coating material is then applied with an end syringe to the cover 78. The plate 70 then slides under the cover 78 and loads the sheet 20 below it in correct alignment with the parallel openings 80. rubber rollers 76 b then adjust to contact the cover 78 beyond the material on top of the cover 78. Where the openings 80 exist, thereby forcing the cover coating material through the openings 80 and onto the sheet. In this way, the cover coating now covers the area. of fusible link 40 (figures 8 and 9). The rubber roller 76 is then raised, the sheet 20 is discharged from the cover 78, and is moved in a UV light chamber in such a way that the material can solidify and form the protective layer 56 (figures 11 and 12). The openings 80 in the cover 78 are large enough so that the protective layer partially covers the contacts 34, 36 as shown in Figures 11 and 12. In addition, the material used for the cover coating must have a viscosity in the Gel or paste range so that after the material diffuses on the sheet 20, it will flow in a manner that creates a generally flat top surface 49, but will not flow into the holes 14 or grooves 16. Although a transparent cover coating without color it is aesthetically pleasing, alternate types of coverings can be used, for example, transparent materials with color can be used. Those colored materials can be manufactured simply by adding a dye to a clear polyurethane gel or paste. The color coding can be achieved through these gels or pastes with color. In other words, different colors of gels can correspond to different amperages, providing the user with a means of reading to determine the amperage of a given fuse switch. The transparency of both coatings allows the user to visually inspect the fusible link 42 prior to installation and during use, on the electronic device in which the fusible switch is used.

The use of this protective layer 56 has significant advantages over the prior art, including the so-called "plugging" method of the prior art. Due to the placement of the protective layer 56 over the entire upper part of a fuse body, the location of the protective layer with respect to the location of the fusible link 42 is not critical. The sheet 20 is then ready for a dicing operation, which separates the rows and columns 27, 29 from each other, and in individual fuse switches, in this dicing operation, a diamond saw is used to cut the blade 20 along parallel planes 57 (FIG 11), and once again perpendicular to planes 57, through the center of holes 14, in individual fuse switches 58 of surface mount thin film (FIGURE 12). One of the cutting directions bisects the terminal areas through the center of the holes 14, exposing and creating the slots 16 of the. terminal contacts 34, 36.

These slots 16 appear on each side of the fusible link 42. This coring operation completes the fabrication of the surface mount thin film fuse switch (FIG 12) of the present invention. Fusible switches according to this invention are cut at voltages and amperages greater than the rates of prior art devices. Tests have indicated that fuse switches that fall within the dimensioning standard. "603" has a melting voltage estimate of 32 volts AC, and a melting amperage that fluctuates between 1/16 amp and 2 amp. Although the fuse switches according to the present invention can protect circuits over a wide range of amperage estimates, the physical size of. These fuse switches remain constant. In summary, the use of the present invention exhibits improved control of fusion characteristics by regulating voltage drops through the fusible link 42. Consistent erase times are ensured by (1) the ability to control through the processes of deposit and photolithography, the dimensions and shapes of the fusible link 42 and the terminal contacts 34, 36; and (2) the proper selection of the fusible link materials 42. Restrictive tendencies are minimized by the cross-section of an optimized material for the substrate 13 and the protective layer 56. While specific embodiments have been illustrated and described, numerous modifications are made. They can come to mind without departing significantly from the spirit of the invention and the scope of protection limited only by the scope of the accompanying claims.

Claims (30)

1. CLAIMS 1. A surface-mount fuse switch, said fuse switch comprises two subassemblies of material: a) a first subassembly comprising a fusible link, a support substrate and terminal contacts that include a plurality of conductive layers of terminal contacts, Support substrate has an upper surface, a lower surface and opposite side surfaces, a first of the plurality of conductive layers of terminal contacts and the fusible link formed as a single continuous layer and extending through the upper surface of the substrate of support, the first of the terminal contact conductive layers further extends over at least a portion of the opposite side surfaces and terminates at the bottom surface of the substrate; and b) the secondary sub-assembly comprises a protective layer which covers the fusible link to provide protection against impacts and oxidation.
2. 2. The surface mount fuse switch according to claim 1, wherein the protective layer is made of a polymeric material.
3. 3. The surface mount fuse switch according to claim 1, wherein the protective layer is made of a polyurethane material.
4. 4. The surface mount fuse switch according to claim 1, wherein the support substrate is made of an epoxy FR-4 or a polyimide.
5. 5. The surface mount fuse switch according to claim 1, wherein the polymeric material is transparent and colorless.
6. 6. The surface mount fuse switch according to claim 2, wherein the polymeric material is transparent and colorless.
7. 7. A method for manufacturing a fusible switch, comprising simultaneously depositing, on the upper part of the substrate, a fusible link and a terminal contact at the opposite ends of said fusible link.
8. 8. The method as claimed in clause 7, comprising depositing, on a portion of the sides and on the upper part of the substrate, electrically communicating terminal contacts with the fusible link, said contacts are for connecting the surface mount fuse switch with a printed circuit board.
9. 9. The method as claimed in clause 7, wherein the fusible link and the wide terminals are deposited by vapor deposition.
10. 10. The method as claimed in clause 7, wherein the fusible link and the wide terminals are deposited electrochemically.
11. 11. A method for protecting a thin film fusible switch having a fusible link and terminal contacts, the terminal contacts have a plurality of r conductive layers of terminal contacts and the substrate has an upper surface, a lower surface and opposite side surfaces, wherein a first of the plurality of terminal contact conductive layers and the fusible link form a continuous thin film extending across the upper surface of the substrate, the first of the terminal contact conductive layers further extends over at least a portion of the opposite lateral surfaces and ends on the lower surface of the substrate, said method comprises placing a single protective layer on the entire surface of the substrate.
12. 12. A thin film fuse switch for surface mounting, comprising: a) a substrate; b) a fusible link and a first terminal contact layer formed as a single continuous layer disposed on the substrate, wherein the fusible link and the first terminal contact layer are made of a metal selected from the group consisting of copper, silver, nickel, titanium, aluminum and their alloys; c) a second terminal contact layer disposed on the first terminal contact layer, wherein the second terminal contact layer is made of the same material as the first layer; d) a third terminal contact layer disposed on the second terminal contact layer, wherein the third terminal contact layer is made of nickel; and e) a fourth terminal layer disposed on the third terminal layer, wherein the fourth terminal layer is made of tin-lead or tin.
13. The surface mount fuse switch according to claim 12, wherein the fusible link has a central portion with a drop of tin-lead that is disposed in the central portion.
14. The surface mount fuse switch according to claim 12, wherein a protective coating layer is applied over the fusible link.
15. 15. The surface mount fuse switch according to claim 14, wherein the protective layer is also applied to a portion of the fourth terminal contact layer.
16. 16. A thin film fuse switch for surface mounting, said fuse comprises: a) a substrate; b) a fusible link made of a first conductive metal deposited on the substrate; c) a second conductive metal, different from the first conducting metal, deposited on the surface of the fusible link; d) terminal contacts electrically connected to the fusible link, the terminal contacts have a plurality of conductive layers, wherein the first of the plurality of conductive layers and the fusible link are simultaneously deposited to form a single one. elícula continues.
17. 17. The device according to the claim 16, wherein wherein the second of the plurality of conductive layers is deposited on the first of the plurality of conductive layers and consists of the same metal as the conductive metal of the first conductive layer.
18. 18. The device according to the claim 17, wherein the third of the plurality of conductive layers is deposited on the second of the plurality of conductive layers and consists of nickel.
19. The device according to claim 17, wherein the fourth of the plurality of conductive layers is deposited on the third of the plurality of conductive layers and consists of tin-lead.
20. The surface mount fuse switch according to claim 16, wherein the first conductive metal is selected from the group including copper, silver, nickel, titanium, aluminum, or its alloys.
21. 21. The surface mount fuse switch according to claim 16, wherein the second conductive metal is a tin-lead alloy.
22. 22. The surface mount fuse switch according to claim 21, wherein the second conductive metal is a tin-lead alloy.
23. 23. The surface mount fuse switch according to claim 22, wherein the second conductive metal is deposited on the fusible link in the shape of a rectangle.
24. 24. The surface mount fuse switch according to claim 23, wherein the fusible link has a central portion and the rectangle is deposited through the central portion of the fusible link.
25. 25. A method for; fabricating a thin film switch for surface mounting, the steps comprising: a) providing a substrate having a top surface, a bottom surface and a stop of holes; b) depositing a first conductive layer on the upper surface of the substrate; and c) a protective layer; wherein the method is characterized in that the deposits of the first conductive layer simultaneously form a fusible link and terminal contacts on the upper surfaces * of the substrate, the fusible link is deposited between the pair of holes and is electrically connected to the terminal contacts, wherein the protective layer includes a single layer of polymeric material having an upper surface which is applied as a gel and is softened through the upper surface of the support substrate and wherein the polymeric material hardens with a substantially flat surface of the material polymeric
26. 26. The method according to claim 25, wherein the first conductive layer extends from the upper surface of the substrate into the holes so that the terminal contacts extend from the upper surface into the holes.
27. 27. The method according to claim 26, wherein the first conductive layer extends from the holes and terminates at the bottom surface of the substrate so that the terminal contacts extend from the holes and terminate at the bottom surface of the substrate.
28. 28. The method according to claim 27, further comprising the step of depositing one or more additional conductive layers on the. top of the terminal contacts.
29. 29. The method according to claim 26, further comprising the step of depositing a metal drop in the fusible link.
30. 30. The method according to claim 25, wherein the protective layer is applied to the fusible link using a template or cliché printing machine. second conductive metal, different from the first conductive metal, deposited on the surface of the fusible link, - d) terminal contacts electrically connected to the fusible link, the terminal contacts have a plurality of conductive layers, wherein the first of the plurality of conductive layers and The fusible link are deposited simultaneously to form a single continuous film. second conductor metal is deposited on the fusible link in the shape of a rectangle.