Abstract:
A method of producing layered metal components is described which obviates the need for layering the terminals twice. The method includes the steps of providing a strip of base material, layering the base material with layering material, and cutting individual pieces from the strip such that the layering material is wiped across the surface of the base material which would otherwise be exposed by the separation.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the manufacture of layered metal components and particularly to electrical terminals having solder cladding. 
     Description of the Prior Art 
     Electrical terminals must be connected to certain articles of manufacture to allow for the flow of electricity from one medium to a different medium. This is particularly true in instances where the conductive elements are embedded in a non-conductive material, such as glass or dielectric substrate. In, for instance, automotive glass panels having electrical wiring embedded therein for the purpose of defogging the window, electrical terminals must be attached to the glass panels to provide a point of connection for electrical current input and output. 
     Currently, such terminals are manufactured beginning with the step of obtaining a ribbon of copper, then cleaning, tin-plating, and reeling the ribbon. The ribbon is de-reeled, clad with a solder material on one side, and re-reeled. The ribbon of solder-clad copper is fed into a progressive stamping die that blanks out the flat terminal, then forms the terminal into its final shape. The terminals are connected to a carrier strip which is used to transfer the terminals along the multiple stations of the progressive stamping dye. The progressive stamping die cuts the individual terminal off of the carrier strip at its last station. The individual terminals are optionally cleaned and reclad with tin-plating or solder to cover the exposed copper where it was cut from the carrier strip. 
     The prior art method of forming electrical terminals has the disadvantage of producing a terminal with exposed copper. Such a terminal is subject to deterioration by oxidation. Alternatively, the terminals must be individually reclad to seal the copper. The task of cladding individual terminals adds expense to the process. 
     SUMMARY OF THE INVENTION 
     A method of producing layered metal components such as clad electrical terminals is described which obviates the need for cladding the terminals twice. The method of this invention includes the steps of providing a strip of base material, depositing a layer of material on the base material, such as cladding material, and cutting individual pieces from the strip in such a manner that the cladding material is wiped across the surface of the base material which would otherwise be exposed by the separation. The method optimally incorporates the use of a comparatively brittle base material, such as copper. The method also optimally includes the use of a soft layering material such as solder, or other lead-tin alloys. Finally, the method works best when a stepped punch is used to cut the individual terminals. The stepped punch includes a fine edge which trims the soft layering material, and a wider edge which both severs the base material and wipes the soft layering material over the newly exposed base material. A stepped die may be used rather than or in addition to a stepped punch. 
     It is therefore a principal object of the invention to provide a method of producing metal components which method includes the step of layering integrated components with layering material only once, but which produces individual components that are entirely covered with layering material. 
     It is another object of this invention to provide a method of forming electrical terminals which allows for the layering of integrated terminals, but which does not require re-layering of separated terminals. 
     Yet another object of this invention is to provide a method of producing layered metal components which are durable and inexpensive of manufacture. 
    
    
     These and other objects will be apparent to those skilled in the art. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of an assembly employing the method of this invention; 
     FIG. 2 is an isometric view of integrated electrical terminals and a separated electrical terminal 
     FIG. 3A is a cross-section of a metal component prior to being severed by the method of this invention; 
     FIG. 3B is a cross section of a metal component being separated from intregated components by the method of this invention; and 
     FIG. 4 is an isometric drawing of the punch and mating die. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The numeral  10  refers to a punch which is used in this novel method. The punch  10  includes a cutting end  12  and a support end  14 . The cutting end  12  is adapted to fit in the aperture  16  of a mating die  18 . The support end  14  is connected to a press  20  which moves the punch  10  into and out of the mating die  18 . 
     The punch  10  and mating die  18  are adapted to sever integrated metal components  22 . Although the integrated metal components  22  may comprise coins, jewelry, or other metal parts, for the purposes of this disclosure, the method of this invention will be described as a method of forming individual electrical terminals  24 . Similarly, the punch  10  and mating die  18  shown herein produce a straight cut, but can be configured to produce any desired shape. In the exemplary method that is shown, the individual electrical terminals  24  are initially processed as integrated electrical terminals  26 . The integrated electrical terminals  26  are formed to include a series of individual electrical terminals  24 , each joined to an adjacent terminal by a terminal carrier portion  28 . 
     The integrated electrical terminals  26  are formed of a base material  30 , commonly copper. The base material  30  is then layered with layering material  32 , such as tin, a tin-lead alloy, or a lead-tin alloy, such as solder. It is also acceptable to layer the base material  30  with tin or a tin-lead alloy, and subsequently apply solder to one side of the electrical terminals. This allows the individual electrical terminals  24  to be pre-soldered for ease of connection, but provides an individual electrical terminal  24  that has a more durable tin or tin-lead alloy plating. The step of layering the layering material  32  on the base material  30  may be completed by any conventional method, such as, but not limited to, electroplating, laminating, spray plating, or cladding. For the application of soldering material to the integrated electrical terminals  26 , cladding is the preferred method of layering. 
     The punch  10  and mating die  18  are employed to remove the terminal carrier portion  28  from the integrated electrical terminals  26  to provide individual electrical terminals  24 . The prior art methods of punching out individual electrical terminals in this manner would result in an exposed portion of the base material  30  where the terminal carrier portion  28  would have been removed. The present method prevents this exposure of the base material  30  by wiping the layering material  32  over the base material  30  in the process of severing the individual electrical terminals  24 . This step is achieved by manipulation of die clearance. 
     Die clearance is the ratio of the space between a punch and its mating die, also known as clearance, to the thickness of the material being punched. The die clearance determines the manner in which the material being punched is cut. A punch employing small die clearance values will tend to shear or trim the material. A punch employing larger die clearance values will tend to stretch or tear the material. 
     The method of this invention employs the method of using a punch  10  that has varying die clearance. Upon initial contact with the integrated electrical terminals  26 , the punch  10  should contact the layering material  32  with a punch having a large die clearance. Such a punch has the effect of stretching the layering material  32  downwardly with the cutting end  12  of the punch  10 . The punch  10  should then have a smaller die clearance to trim the base material  30  and wipe the stretched layering material  32  over the exposed base material  30 . 
     One manner by which this method may be employed is by using a punch  10  with a cutting edge  12  that is stepped. As seen in FIGS. 3A and 3B, the cutting end  12  has a leading section  34 . The leading section  34  has a width (w) and a height (h). The cutting end  12  also has a trailing section  36 . The trailing section  36  has a width (w+2×). As the cutting end  12  contacts the integrated electrical terminals  26 , the leading section  34 , having a larger die clearance, stretches the layering material  32 . As the punch  10  continues toward the mating die  18 , the trailing section  36  both trims the base material  30  and wipes the layering material  32  over the newly exposed base section  30 . The punch  10  continues into the mating die  18  to remove the terminal carrier portion  28  from the integrated electrical terminal  26  to produce an individual electrical terminal  24  that has no exposed base material  30 . The die clearance may also be manipulated as described above by providing a stepped die (not shown). The stepped die would have a wider apeture and a stepped, slightly smaller apeture below the upper surface of the die. The die clearance is initially large and, as the material is pushed into the die, becomes small, resulting in a punched piece that is entirely covered with layering material  32 . 
     Thus it can be seen that the present invention achieves at least all of the stated objects of the invention.