Abstract:
A convenient, cost-effective method for manufacturing low-current fuse elements. The method may include the steps of stamping a substrate out of a sheet of material and stamping at least one hole in the substrate. The method may further include the steps of bonding a layer of fuse material to a surface of the substrate with a portion of the fuse material covering the hole, stamping a fuse element out of the portion of fuse material covering the hole, and separating an individual fuse from the fuse material and the substrate. A low-current fuse can thereby be obtained using an easily performed stamping process.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 14/381,701 filed Aug. 28, 2014, which claims priority to U.S. Provisional Patent Application No. 61/647,855, filed May 16, 2012, both of which are herein incorporated by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The disclosure relates generally to the field of circuit protection devices and more particularly to a method for manufacturing low-current fuses. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    Automotive fuses are typically produced using conventional stamping processes wherein a fuse is punched out of a sheet of metal by an appropriately-shaped dye. Stamping is generally preferred to other fuse manufacturing methods because it is a relatively low cost process that produces a high-quality product. However, it is extremely difficult to produce low-current fuse elements using stamping processes because such elements must generally be very narrow and very thin. Stamping such thin materials often results in damage to portions of the material that must remain intact. Thus, in order to achieve the requisite dimensions for low-current fuse elements, skiving or coining methods are commonly employed. While these methods are capable of producing fuse elements that are thin and narrow, they are extremely difficult to employ and are themselves prone to material tear-through. It would therefore be advantageous to provide a method for manufacturing low-current fuse elements that offers the ease and low cost of stamping processes. 
       SUMMARY 
       [0004]    In accordance with the present disclosure, a convenient, cost-effective method for manufacturing high-quality, low-current fuse elements is provided. The method may include the steps of stamping a base metal blank out of a sheet of material and stamping at least one hole in the base metal blank. The method may further include the steps of bonding a layer of fuse material to a surface of the base metal blank with a portion of the fuse material covering the hole, stamping a fuse element out of the portion of fuse material covering the hole, and separating an individual fuse from the fuse material and the base metal blank. A low-current fuse can thereby be obtained using an easily performed, low-cost stamping process. 
         [0005]    Additional methods may include stamping a base blank out of a nonconductive material and stamping at least one hole in the base blank. The method may further include the steps of bonding a layer of fuse material to a surface of the base blank with a portion of the fuse material covering the hole, stamping a fuse element out of the portion of fuse material covering the hole, and separating an individual fuse from the fuse material and the base blank. A low-current fuse can thereby be obtained using an easily performed, low-cost stamping process. 
         [0006]    A low-current fuse comprising a first fuse terminal formed from a first terminal layer bonded about a first lateral edge of a substrate, a second fuse terminal formed from a second terminal layer bonded about a second lateral edge of a substrate, and a fuse element formed from a conductive foil bonded to a surface of the substrate, the fuse element electrically connecting the first and second fuse terminals, the fuse element formed from stamping the conductive foil after the conductive foil has been bonded to the substrate are also disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    By way of example, specific embodiments of the disclosed device will now be described, with reference to the accompanying drawings, in which: 
           [0008]      FIGS. 1A-1D  are block diagrams of a fuse stamped from a bonded conductive foil and base metal blank; 
           [0009]      FIGS. 2A-2D  are block diagrams of a fuse stamped from a bonded conductive foil and base blank; 
           [0010]      FIG. 3  is a flow chart illustrating a method of forming a fuse, all arranged in accordance with at least some embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. 
         [0012]      FIG. 1A  illustrates a block diagram of a base metal blank  100 . The base metal blank  100  may be stamped out of a larger sheet of material (not shown), such as a sheet of aluminum or other metal, using a conventional stamping process that will be familiar to those of ordinary skill in the art. The sheet of material may have a thickness that facilitates conventional stamping of the material. In some examples, the base metal blank  100  may have a thickness of about 0.75 mm. The base metal blank  100  may have a width that is substantially equal to the width of a desired fuse and a length that is at least as long as the length of a desired fuse. In some examples, the length of the base metal blank  100  may be at least as long as the length of several desired fuses. 
         [0013]    As depicted, the base metal blank  100  has holes  110  therein. The holes  110  may be stamped in the base metal blank  100  using a conventional stamping process that will be familiar to those of ordinary skill in the art. The position of the holes  110  relative to the lateral edges of the base metal blank  100  may correspond to the position of a fuse element of a desired fuse relative to the lateral edges of the desired fuse. The holes  110  are longitudinally spaced apart from one another a distance that is at least as great as the length of a desired fuse. The holes  110  may have an area at least as large as the area of a fuse element of a desired fuse. In some examples, the width of the holes  110  may be about 3 mm and the length of the holes  110  may be about 4 mm. As depicted, the shape of the holes  110  is square. It is to be appreciated, that the shape of the holes  200  may be changed to suite various geometries and areas of the fuse element of a desired fuse without departing from the scope of the present disclosure. 
         [0014]      FIG. 1B  illustrates a block diagram of the base metal blank  100  having a conductive foil  120  bonded thereto. As depicted, the conductive foil  120  is bonded to the top surface of the base metal blank  100 . In some examples, the conductive foil  120  may be a thin strip of copper. As depicted, the conductive foil  120  covers the holes  110  in the base metal blank  100 . The conductive foil  120  may have a thickness that is substantially equal to a thickness of a desired low-current fuse element, such as, for example, 0.05 mm. In some example, the low-current fuse may be configured to have a maximum current capacity of less than 2 Amps. Other material having suitable conductive and fuse properties may be substituted for the conductive foil  120  without departing from the scope of the present disclosure. 
         [0015]      FIG. 1C  illustrates the base metal blank  100  and the conductive foil  120  having fuse elements  130  stamped out of the conductive foil  120 . In general, the fuse elements  130  may be stamped using an appropriate shaped dye. As depicted, the fuse elements  130  are stamped out of the conductive foil  120  over the holes  110 . During such stamping, the base metal blank  100  provides the conductive foil  120  with a rigid backing and effectively thickens the portions of the conductive foil  120  that surround the fuse element  130  being stamped, thereby facilitating the application of a conventional stamping process that would be difficult of impossible to perform on the conductive foil  120  alone. More specifically, the thickness of the conductive foil  120  is such that traditional stamping processes may tear the fuse element. The base metal blank  100 , however, provides a rigid backing that enables the fuse elements  130  to be stamped out of the conductive foil  120  using conventional stamping processes. 
         [0016]    As depicted, the fuse elements  130  are “Z” shaped. However, other fuse element geometries may be stamped out of the conductive foil  120  without departing from the scope of the present disclosure. 
         [0017]      FIG. 1D  illustrates an individual fuse  140  separated from corresponding portion  102  shown in  FIG. 1C . In some examples, the individual fuse  140 , including the corresponding portion of the base metal blank  100  and conductive foil  120  may be separated by cutting or clipping the base metal blank  100  and the conductive foil  120 . As such, the individual fuse  140  having a low-current fuse element  130   a  and, optionally, associated fuse terminals  150 , may be obtained. The base metal blank  100  material on the underside of the fuse  140  provides the fuse  140  with an additional amount of strength and support. 
         [0018]      FIG. 2A  illustrates a block diagram of a substrate  200 . The substrate  200  may be stamped out of a larger sheet of nonconductive material (not shown), such as a sheet of FR4or other suitable substrate material, using a conventional stamping process that will be familiar to those of ordinary skill in the art. The sheet of material may have a thickness that facilitates conventional stamping of the material. In some examples, the substrate  200  may have a thickness of about 0.75 mm. The substrate  200  may have a width that is substantially equal to the width of a desired fuse and a length that is at least as long as the length of a desired fuse. In some examples, the length of the substrate  200  may be at least as long as the length of several desired fuses. As will be described more fully herein, the substrate  200  may be used a frame for a thin conductive material, which by itself may not have enough mechanical strength to facilitate stamping or otherwise manufacturing a fuse element from. 
         [0019]    As depicted, the substrate  200  has holes  210  therein. The holes  210  may be stamped in the base blank  200  using a conventional stamping process that will be familiar to those of ordinary skill in the art. The position of the holes  210  relative to the lateral edges of the substrate  200  may correspond to the position of a fuse element of a desired fuse relative to the lateral edges of the desired fuse. The holes  210  are longitudinally spaced apart from one another a distance that is at least as great as the length of a desired fuse. The holes  210  may have an area at least as large as the area of a fuse element of a desired fuse. In some examples, the width of the holes  210  may be about 3 mm and the length of the holes  210  may be about 4 mm. As depicted, the holes  200  are square in shape. It is to be appreciated, that the shape of the holes  200  may be changed to suite various geometries and areas of the fuse element of a desired fuse without departing from the scope of the present disclosure. 
         [0020]    The substrate  200  additionally has a first terminal layer  212   a  bonded around one edge of the substrate  200 . As depicted, the first terminal layer  212   a  is bonded on the upper surface of the substrate  200 , over a lateral edge of the substrate  200  and on the lower surface of the substrate  200 . Furthermore, the first terminal layer  212   a  is depicted as starting at one lateral edge of the holes  210  on the upper surface of the substrate  200  and ending at the same lateral edge of the holes  210  on the lower surface. A second terminal layer  212   b  is also bonded around the other edge of the substrate  200 . As depicted, the second terminal layer  212   b  is bonded on the upper surface of the substrate  200 , over the other lateral edge of the substrate  200  and on the lower surface of the substrate  200 . Furthermore, the second terminal layer  212   b  is depicted as starting at the other lateral edge of the holes  210  on the upper surface of the substrate  200  and ending at the same lateral edge of the holes  210  on the lower surface. In some examples, the terminal layers  212   a ,  212   b  may be a thin strip of copper, zinc, or other suitable conductive material. 
         [0021]      FIG. 2B  illustrates a block diagram of the substrate  200  having a conductive foil  220  bonded thereto. As depicted, the conductive foil  220  is bonded to the top surface of the substrate  200 , over the first and second terminal layers  212   a ,  212   b . In some examples, the conductive foil  220  may be a thin strip of copper, zinc, or other conductive material having fuse element properties. As depicted, the conductive foil  220  covers the holes  210  in the substrate  200 . The conductive foil  220  may have a thickness that is substantially equal to a thickness of a desired low-current fuse element, such as, for example, between 0.4 mm and 0.05 mm. In some example, the low-current fuse may be configured to have a maximum current capacity of less than 2 Amps. Other material having suitable conductive and fuse properties may be substituted for the conductive foil  220  without departing from the scope of the present disclosure. 
         [0022]      FIG. 2C  illustrates the substrate  200  and the conductive foil  220  having fuse elements  230  stamped out of the conductive foil  220 . In general, the fuse elements  230  may be stamped using an appropriate shaped dye. As depicted, the fuse elements  230  are stamped out of the conductive foil  220  over the holes  210 . During such stamping, the substrate  200  provides the conductive foil  220  with a rigid backing and effectively thickens the portions of the conductive foil  220  that surround the fuse element  230  being stamped, thereby facilitating the application of a conventional stamping process that would be difficult of impossible to perform on the conductive foil  220  alone. More specifically, the thickness of the conductive foil  220  is such that traditional stamping processes may tear the fuse element. The substrate  200 , however, provides a rigid backing that enables the fuse elements  230  to be stamped out of the conductive foil  220  using conventional stamping processes. 
         [0023]    As depicted, the fuse elements  230  are “S” shaped. However, other fuse element geometries may be stamped out of the conductive foil  220  without departing from the scope of the present disclosure. 
         [0024]      FIG. 2D  illustrates an individual fuse  240  separated from a corresponding portion  202  shown in  FIG. 2C . In some examples, the individual fuse  240 , including the corresponding portion of the substrate  200 , first and second terminal layers  212   a ,  212   b , and conductive foil  220  may be separated by cutting or clipping fuse  240  from the corresponding portion  202 . As such, the individual fuse  240  having a low-current fuse element  230   a  may be obtained. The substrate  200  material on the underside of the fuse  240  provides the fuse  240  with an additional amount of strength and support. 
         [0025]    As depicted, the fuse element  230   a , formed from the portion of the conductive foil  220 , is disposed over the hole  210   a . The substrate  200  material on the underside of the conductive foil  220  provides the fuse  240 , and particularly, the fuse element  230   a , with an additional amount of strength and support. Additionally, first and second terminal layers  212   a ,  212   b  provide first and second terminals  250   a ,  250   b , respectively, for the fuse  240 . In some examples, the fuse  240  may be a surface mount fuse. As such, the portions of the first and second terminal layers  212   a ,  212   b  bonded on the lower surface of the substrate  200 , which form first and second terminals  250   a ,  250   b , may provide electrical connection with a circuit to be protected in a surface mount application. 
         [0026]      FIG. 3  is a flow chart illustrating a method  300  for forming a fuse, arranged in accordance with at least some embodiments of the present disclosure. In general, the method  300  is described with reference to  FIGS. 2A-2D . It is to be appreciated, however, that the method  300  may also be used to manufacture the fuse  140  described with respect to  FIGS. 1A-1D , or other fuses consistent with the present disclosure. 
         [0027]    The method  300  may begin at block  310 . At block  310 , a substrate is stamped out of a larger sheet of material. For example,  FIG. 2A  shows the substrate  200 , which may be stamped out of a larger sheet of material, such as, for example, aluminum, FR4, or other material, using a conventional stamping process that will be familiar to those of ordinary skill in the art. 
         [0028]    Continuing from block  310  to block  320 , a series of holes are stamped in the substrate. For example,  FIG. 2A  shows holes  210  stamped in the substrate  200 . In some examples, blocks  310  and  320  may be performed simultaneously (e.g., using a single stamping operation, or the like). Continuing from block  320  to block  330 , terminal layers may be bonded to the substrate  200 . For example,  FIG. 2A  shows first terminal layer  212   a  may be bonded about a first lateral edge of the substrate  200  and on upper and lower surfaces of the substrate  200  adjacent to the first lateral edge. Similarly, second terminal layer  212   b  may be bonded about a second lateral edge of the substrate  200  and on upper and lower surfaces of the substrate  200  adjacent to the second lateral edge. In some examples, the terminal layers  212   a ,  212   b  may be a thin strip of copper. The terminal layers  212   a ,  212   b  may be bonded to the substrate  200  using an adhesive, such as, for example, “prepreg” or other appropriate bonding agent. In some examples, the terminal layers  212   a ,  212   b  may be bonded, laminated, or otherwise affixed to the surface of the substrate  200  using any suitable process or technique. 
         [0029]    Continuing from block  320  to block  330 , a conductive foil may be bonded to the substrate. For example,  FIG. 2B  shows conductive foil  220  bonded to the substrate  200 . In some examples, the conductive foil  220  may be a thin strip of copper. The conductive foil  220  may be bonded to the substrate  200  using an adhesive, such as, for example, “prepreg” or other appropriate bonding agent. In some examples, the conductive foil  220  may be bonded, laminated, or otherwise affixed to the surface of the substrate  200  using any suitable process or technique. Furthermore, in embodiments where terminal layers  212   a ,  212   b  are bonded to the substrate  200 , the conductive foil  220  may be bonded over the portions of the terminal layers  212   a ,  212   b  disposed on the same surface of the substrate to which the conductive foil  220  is bonded. 
         [0030]    Continuing from block  330  to block  340 , a fuse element may be stamped in the conductive foil. For example,  FIG. 2C  shows fuse elements  230  stamped out of the conductive foil  220 . Continuing from block  340  to block  350 , an individual fuse may be separated from a corresponding portion of the substrate. For example,  FIG. 2D  shows an individual fuse  240  separated from the corresponding portion  202  shown in  FIG. 2C . In some examples, the individual fuse  240 , including the corresponding portion of the substrate  200  and conductive foil  220  may be separated by cutting or clipping the substrate  200  and the conductive foil  220 . As such, the individual fuse  240  having a low-current fuse element  230   a  and, optionally, associated fuse terminal  250 , may be obtained. 
         [0031]    Continuing from block  350  to block  360 , a determination of whether more fuses need to be removed from the substrate  200  and the conductive foil  220  may be made. Based on the determination, the process may return to block  350 , where another individual fuse may be separated from a corresponding portion of the substrate and conductive foil, or the process may end. In some examples, individual fuses (e.g., the fuse  240 , or the like) may be separated iteratively as block  350  is repeatedly performed. With other examples, multiple individual fuses may be separated at once, such as, by stamping them out, or the like.