Abstract:
A method for plating strips including providing a strip of material, providing a masking belt including patterned windows, providing a tank with a plating solution, generating a continuous movement in the cell of an assembly of the strip and masking belt, whereby the structure of the masking belt masks portions of the strip in the tank.

Description:
FIELD OF THE INVENTION 
       [0001]    The instant invention relates to plating methods and apparatus for the plating of strips. For instance, the plating method and apparatus is applicable to the manufacture of electrical terminals and electrical connectors, and strips obtained by these methods. 
       BACKGROUND OF THE INVENTION 
       [0002]    In this document the invention is described in relation to the manufacturing of electrical terminals for connectors used in automotive or telecommunication applications, but as it will be understood from the following the invention can be used for plating any kind of strip of material and in particular flexible metal strips. 
         [0003]    In the application chosen for illustrating the invention strips to be plated are connector terminal strips. One may use rigid structures such as so-called “lead frames” or “carriers” for supporting these electrical terminals. A lead frame or carrier enables to hold together the terminals during their manufacturing process, which makes a continuous manufacturing process possible on an industrial scale. At a final stage of the manufacture process of the connector, the terminals are separated away from the frame or carrier, which is scraped. 
         [0004]    One of the steps of the manufacture of electrical terminals is the plating of a metallic conductor such as, for example gold, on their surface. The strip of lead frames or carriers is continuously moved in an electroplating cell between two independent belt portions, which are used to carry the lead frames or carriers. There is a need to make this process more efficient. 
         [0005]    In the following, for the sake of simplification, the word “carrier” is used for designating either a lead- frame or any other kind of carrier. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention relates to a method for the manufacture of plated strips. 
         [0007]    This method comprises the provision of a strip, for instance a metallic strip. This strip comprises a top band, a bottom band, a structure joining together the top and bottom bands, and leads disposed between the top band and the bottom band. For instance, these leads are designed to form electrical terminals for electrical connectors. 
         [0008]    A masking belt is provided. The belt comprises a top band, a bottom band, and a structure joining together the top and bottom bands. 
         [0009]    A tank is provided. For instance this tank is a metallisation cell with a chamber receiving a solution of an electrical conductor, and an electrode. 
         [0010]    A continuous movement of an assembly of the strip and the masking belt is generated in the cell. The masking belt masks at least partially the strip in the cell. 
         [0011]    The electrical conductor is electroplated on the metallic strip in the solution by applying an electrical field between the strip and the electrode during the continuous movement. The electroplating occurs only on the uncovered or unmasked portions of the strip. 
         [0012]    With these features, no electrical conductor is applied on the masked portion of the strip. Since this portion may be scraped and/or not used, waste of plating material (gold for instance) is avoided and the efficiency of the process is consequently improved. 
         [0013]    In some embodiments, one might also use one or more of the features as defined in the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Other characteristics and advantages of the invention will appear from the following description of three of its embodiments, provided as non-limitative examples, and of the accompanying drawings. 
           [0015]    On the drawings: 
           [0016]      FIG. 1  is a partial planar view of a metallic strip, 
           [0017]      FIG. 2  is a schematic partial perspective view of an apparatus according to a first embodiment, 
           [0018]      FIGS. 3   a  and  3   b  are opposite exploded perspective views of a strip and belt assembly for the apparatus of  FIG. 2 , 
           [0019]      FIG. 4  is a view corresponding to  FIG. 3   b , and not exploded, and 
           [0020]      FIGS. 5 and 6  are views corresponding to  FIG. 4  for a second and respectively third embodiments. On the different figures, the same reference signs designate like or similar elements. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  schematically shows a pattern of an electrically conductive strip  1 . The strip  1  is formed as a repetition of a plurality of such patterns arranged the one after the others along the longitudinal direction X. The strip  1  may comprise hundreds of such patterns. The strip  1  is made from electrically conducting material, such as for example, a thin foil of copper which has been formed, for example stamped, as the shown shape. The strip is provided sufficiently thin and resilient to be flexible with respect to the X axis, so as to be provided as a reel of material. The strip  1  comprises a carrier band  2  which carries electrical leads  3 . The carrier band  2  may define a plurality of windows  4 , each window enclosing a set of leads  3  which will form electrical terminals of a same electrical connector. The carrier band  2  comprises a top band  5  and a parallel bottom band  6  which extend along the direction X. The top and bottom bands  5 ,  6  are linked together by a structure  7 , which ensures the mechanical stability of the carrier band  2 . For example, the structure  7  comprises a plurality of parallel pillars  8  extending along the transverse direction Y between the top  5  and bottom bands  6 . In this particular example, a window  4  is defined between two subsequent pillars  8 , and between the top and bottom bands  5 ,  6 . The leads  3  are made integral with the carrier band  2  using a linking bar  9  which is a bar integral with the structure  7 , as well as integral with any of the leads  3 . 
         [0022]    In the present example, the leads  3  extend sensibly straight along the direction Y. However, other geometries are possible. Each lead  3  extends between a first end  3   a  and a second end  3   b,  which are provided on opposite sides with respect to the bar  9 . The first  3   a  and second  3   b  ends are form tips which are more or less sharp depending on the application. All leads need not to have the same geometry. Some of the leads are longer than the others. 
         [0023]    The carrier band  2  comprises a plurality of driving features  10 . Such features  10  are for example holes  11  provided in the top and bottom bands  5  and  6  in equidistant fashion along the direction X, so as to cooperate with a driving device, not shown, such as motor-driven toothed wheels having teeth designed to engage the holes  11 . 
         [0024]    Referring to  FIG. 2 , an apparatus  12  is described. The apparatus  12  comprises at least one electroplating cell or tank  13  as well as a feeding reel  14  and an uptake reel  15 . The feeding reel  14  feeds the strip  1  to the electroplating cell  13 . The strip is shown plain so as to simplify the drawing, but is has windows as shown on  FIG. 1 . In the electroplating cell  13 , an electrically conductive material, in particular metal, is electroplated on the strip  1 . The apparatus  12  may comprise one or more such cells  13  provided the one after the others, so as to apply a plurality of identical or different treatments to the strip  1 . The strip  1  is then wound again on the uptake reel  15 . 
         [0025]    The cell  13  encloses a solution bath  16  which is a liquid in which a metal to be deposited on a strip  1  is diluted. The cell  13  further comprises an electrode  17  to which an electrical potential can be applied by a generator. The strip  1  is held at another potential so that the potential difference between the electrode  17  and the strip  1  causes metal of the bath  16  to plate the strip  1 . 
         [0026]    In the cell  13 , the strip  1  is assembled with a masking belt  18 , which masks portions of the strip  1  on which electroplating is not desired. A driving device  19 , such as a roller, is rotated and used to drive the belt  18  in the cell  13 . 
         [0027]    In the cell  13 , the strip  1  and the belt  18  are pressed against each other so that only the unmasked parts of the strip are plated with the diluted metal. In the shown embodiment, the strip  1  is held between two belt portions  20  and  21 . The belt portion  20  is a continuous belt in direct contact with the driving device  19  and also with one or more additional rollers  22 . 
         [0028]    Two rollers  23   a  and  23   b  apply the strip  1  directly against the belt portion  20  within the cell  13 . These rollers may be provided outside the cell  3  and/or used to apply an electrical potential to the strip. They engage the holes  11  to drive the strip  1 . 
         [0029]    The second belt portion  21  is applied directly on the strip  1  using rollers  24   a  and  24   b.  The second belt portion  21  may also be provided continuous (endless) using other rollers (not shown). 
         [0030]      FIGS. 3   a  and  3   b  schematically show the way the strip  1  is held between the two belt portions  20  and  21  in the bath.  FIGS. 3   a  and  3   b  are schematically shown with the straight strip  1  and the belt portions  20  and  21 , but in fact they are wrapped around the driving device  19  as shown on  FIG. 2 . 
         [0031]    The belt portion  20  has a face  26  which faces the strip  1  and an opposite face  27  which is driven by the driving device  19 . For example, the face  27  has corrugations  28  which cooperate with complementary features of the driving device  19  so as to precisely drive the belt portion  20 . 
         [0032]    The belt  18  has a top band  29  which faces the top band  5  of the strip  1 . The belt  18  also has a bottom band  30  which faces the bottom band  6  of the strip  1 . 
         [0033]    Furthermore, the belt  18  is provided with periodic structures  31 , the geometry of which mimics the geometry of the structures  7  of the strip  1 . In the present example, where the strip  1  has pillars  8 , the belt  18  is also provided with pillars. 
         [0034]    In the present case, windows  32  are provided in the belt  18 , which correspond to the windows  4  of the strip  1 . A recess or groove  33  is provided on the inner face of one or more of the belt portions  20 ,  21 , it is sufficiently large and deep for receiving the strip  1 . 
         [0035]    The belt portions  20  and  21  are also provided with inter-digital features, in order to precisely define their relative positions, in particular with respect to the longitudinal direction X. Indeed, any slippage or differential movement of the belts along the direction X, and any offset between the structures of the belt and the strip ought to be avoided. For example, the belt portion  20  is provided with fingers  34  which cooperate with complementary holes or recesses  35  of the belt portion  21  so as to precisely define the position of the two belt portions relative to one another. 
         [0036]    The belt  18  is provided in a material which is sufficiently strong to withstand the driving by the driving device  19 , which can carry the strip without any slippage, and which can also seal efficiently the part of the structures which should not be electroplated, in particular in a bath which is agitated in particular by the movement of the moving parts. For example, the belt portions are made from a reinforced aramide overcoated with a silicone coating adapted to provide the sealing ability. 
         [0037]      FIG. 4  shows the strip  1  and belt  18  assembly, the strip  1  being masked by the belt  18 . In this way, metal is electroplated only on the terminal leads and the bar  9 . For example, nickel is electroplated in this embodiment. In a second embodiment, as shown on  FIG. 5 , which can be alternative to the embodiment of  FIG. 4 , or after it, in another cell, the belt  18  is provided with a different geometry, so that only part of the leads  3  is submitted to electroplating. In particular, in this embodiment, only the bottom part of the pins, below the bar  9 , is submitted to electroplating, for example of tin. 
         [0038]    In yet another embodiment, as shown on  FIG. 6 , which may be alternative or following the embodiments of  FIG. 4  or  5 , only the top part of the leads are electroplated, for example by gold, by masking the bottom part of the leads  3  with the masking belt  18 . 
         [0039]    The manufactured leads can then be processed for the manufacture of electrical connectors, for example by overmolding the leads in plastic and separating away the metallic frame.