Abstract:
A method of securing articles to each other and an alignment and holding apparatus comprising a platform having an alignment member for positioning and holding a first article, such as a substrate, in a first position and a further alignment member for aligning extensions of a second article, such as a lead frame, in an assembleable position with respect to the first article while a spacer maintains the extensions in proper lateral position and a clamp that secures the extensions proximate the first article while an electrical connection is formed between the first article and the extensions of the second article.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    None  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    None  
         REFERENCE TO A MICROFICHE APPENDIX  
         [0003]    None  
         FIELD OF THE INVENTION  
         [0004]    This invention relates generally to an apparatus and a method of precision alignment mounting and holding articles during a securement process and, more specifically, to apparatus and method for mounting and holding a lead frame as the electrical leads are secured to a substrate.  
         BACKGROUND OF THE INVENTION  
         [0005]    The surface mounting of lead frames to a substrate is known in the art. U.S. Pat. No. 6,307,755 shows and describes a number of methods for mounting a lead frame to a substrate. In contrast, the present invention provides a method and apparatus for first positioning two or more articles with respect to each other and then securing the articles to each other and, more specifically, it enables small delicate elements, such as the elongated electrical leads of a lead frame, to be quickly and properly positioned with respect to a substrate. Once positioned the electrical leads are then temporarily held in a securement position by a pressure clamp followed by the in situ securement of the leads of the lead frame to the substrate.  
         SUMMARY OF THE INVENTION  
         [0006]    Briefly, the present invention comprises a method of securing articles to each other and an alignment and holding apparatus comprising a platform having an alignment member for positioning and holding a first article, such as a substrate, in a first position and a further alignment member for aligning extensions of a second article, such as a lead frame, in an assembleable position with respect to the first article while a spacer maintains the extensions in proper lateral position. A clamp secures the extensions proximate the first article while an electrical connection is formed between the first article and the extensions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a top view of a plurality of substrates mounted in a side-by-side condition on a support sheet;  
         [0008]    [0008]FIG. 2 is a top view of a lead frame having a plurality of electrically conducting leads that are held in a spaced condition by a non-conducting material;  
         [0009]    [0009]FIG. 3 is a side view of the apparatus for holding a substrate and the leads of a lead frame in an assembleable condition;  
         [0010]    [0010]FIG. 4 is a front view of the apparatus of FIG. 4 showing a plurality of lead frame clamping members arranged in a side-by-side condition;  
         [0011]    [0011]FIG. 5 shows a separator member having a plurality of elongated tines or fingers for holding the leads of a lead frame in a spaced condition during the assembly process;  
         [0012]    [0012]FIG. 6 is a partial perspective view showing a substrate and a lead frame positioned proximate each other with the elongated separator elements holding the electrically conducting leads on the lead frame in a spaced condition;  
         [0013]    [0013]FIG. 7 is a partial side view showing a substrate and lead frame held in a clamped condition by a lead frame clamp; and  
         [0014]    [0014]FIG. 8 is a partial top view showing the substrate and lead frame of FIG. 7 held in a clamped condition by the lead frame clamp. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    [0015]FIG. 1 is a top view of a plurality of articles such as substrates  12 ,  13 ,  14  and  15  which are mounted in a side-by-side condition on a support sheet  11 . In the embodiment shown support sheet  11  comprises four distinct separable regions  11   a,    11   b,    11   c  and  11   d.  Regions  11   a  and  11   b  are separated by a break line comprising a partially severed region  22  to enable the separation of support sheet  11   a  from support sheet  11   b  by bending adjacent sections. Similarly, regions  11   b  and  11   c  are separated by a break line comprising a partially severed region  16  to enable the separation of support sheet  11   b  from support sheet  11   c  and regions  11   c  and  11   d  are separated by a break line comprising a partially severed region  17  to enable the separation of support sheet  11   d  from support sheet  11   c.  By mounting multiple substrates on a support sheet one can simultaneously align all the substrates on the support sheet and simultaneously secure the substrates to another article. Once secured the individual substrates can be separated. Thus, one of the purposes of mounting multiple substrates on a single support sheet is to permit assembly and attachment of multiple lead frames to corresponding substrates. While four substrates are shown more or less substrates could be assembled using the present apparatus and method.  
         [0016]    Although a support sheet  11  is shown as separable to permit multiple attachments, if desired, each of the substrates can be integral to a support sheet which is non-separable.  
         [0017]    Mounted on support sheet  11  are substrates  12 ,  13 ,  14  and  15 . In the embodiment shown each of the substrates are identical and only one will be described herein. Substrate  12  includes electrically conducting leads  12   a,    12   b,    12   c  and  12   d  extending outwardly from substrate  12  with each of the leads in a laterally spaced condition from each other. The leads are to be connected to the electrically conducting leads of another article such as a lead frame.  
         [0018]    In the embodiment shown the support sheet  11  includes a set of locators or alignment holes  18 ,  19 ,  20  and  21  which comprises circular holes that have been etched in support sheet  11 . By etching the alignment holes in support sheet  11  one can obtain precise location of the alignment holes in the support sheet  11  which allows one to precisely position the support sheet on a substrate platform and consequently precisely position the leads on support sheet  11  in a condition for securement to the leads of a lead frame. Thus, by positioning the alignment holes on alignment members such as guide pins on a substrate platform one can quickly orientate the leads of the substrate to a known position. Similarly, by using the same substrate platform having a further alignment member for the lead frame one can quickly position the leads of the substrate with respect to the leads on the lead frame. In order to appreciate the alignment and securement process reference should be made to FIGS.  2 - 8 .  
         [0019]    [0019]FIG. 2 is a top view of a lead frame  25  having a plurality of electrically conducting leads  27 ,  28 ,  29  and  30  that are held in a spaced condition by a traversely extending non-conducting member  31 . Typically, lead frame  25  can be etched from a sheet of electrical conducting material such as metal or the like. During the manufacturing process, one can leave a separable cross piece  26  having holes  37  and  38  with electrical conducting leads  27 ,  28   29  and  30  extending from the separable and disposable cross piece  26 . Each of the leads  27 ,  28   29  and  30  are held in a spaced condition by non-conducting member  31  which can be secured thereto by an adhesive or the like. The purpose of member  31  is two fold, first as each of the electrical conducting leads are small and can easily be bent the member  31  functions to hold the leads in a rigid arrangement. Second, since the member  31  is secured to the leads, it can be used as a locating guide to position the ends of the electrical leads on a substrate platform. In the embodiment shown lead  27  has a coating of solder and flux  33 . Similarly, lead  28  has a coating of solder and flux  34 , lead  29  has a coating of solder and flux  35  and lead  23  has a coating of solder and flux  36 .  
         [0020]    [0020]FIG. 3 is a side view of the apparatus  40  for holding a substrate and a lead frame in an assembleable condition. Apparatus  40  includes a substrate platform  41  having a first set of alignment members  42  comprises cylindrical guide pins (see FIG. 4) that extend perpendicularly outward from platform  41  for aligning and holding support sheet  11  so that the alignment holes  18 ,  19 ,  20  and  21  engage the alignment members  43  thereby precisely locating the substrates thereon. Referring to FIG. 3, located laterally of alignment member  42  is a lead separation member  43  which is held in position in a slot in platform  41 . Lead separation member  43  is refereed to as a comb since it contains a set of parallel extending teeth.  
         [0021]    [0021]FIG. 5 shows a front view of comb  43  illustrating the fingers  43   a,    43   b,    43   c,    43   d  and  43   e  that extend outward from each other in a parallel relationship. Each of the fingers or teeth are sufficiently rigid so as to maintain the spacing therebetween. In the embodiment shown the comb  43  is positioned so as to engage and maintain the separation of the leads on the lead frame during the assembly process and to ensure the leads are located properly with respect to the substrate platform. In order to facilitate insertion of the leads therearound the ends of the fingers are provided with a tapered end surface.  
         [0022]    Located on platform  41  is a pressure clamp  50  having a movable jaw  51  that can be extended to apply normal pressure to hold a lead frame in a fixed position on the platform  41 . Lead frame clamp  50  includes a handle  52  to allow one to apply or remove clamping pressure to a lead frame positioned on the platform  41 .  
         [0023]    [0023]FIG. 4 shows a front view of the apparatus  40  showing that four clamps  50 ,  55 ,  56  and  58  are mounted in a side-by-side condition for securing a plurality of lead frames to a substrate. The purpose of using multiple clamps is that individual lead frames do not have to be ganged together as they can be individually positioned and aligned with respect to a substrate on the support sheet.  
         [0024]    [0024]FIG. 6 shows an isolated perspective view illustrating how the substrate  12 , comb  43  and lead frame  25  are positioned during the assembly process. In the embodiment shown the lead frame ends are to be soldered or electrically connected unto leads extending from substrate  12 .  
         [0025]    [0025]FIG. 7 shows a partial enlarged side view of the substrate platform  41  and support sheet  11  with support sheet  11  carrying an electrical lead  12   a  from substrate  12 . Electrical lead  12   a  is in an aligned condition with lead  27  on lead frame  25 . In the view showing in FIG. 7 the finger  43   a  is positioned on one side lead  27  and the end of lead  27  is positioned over lead  12   a  with the solder and pastes  33  on lead  27  in engagement with solder and paste  12   ae  on lead  12 . The lead  27  is further held in position by dielectric alignment member  31  which is located in alignment recess  41   a  in platform  41 . The movable jaw  51  is shown clamping lead  27  in position. Located on top of the end of lead  27  is a pressure heating element  70  for heating the end of lead  27  to cause the solder to flow and solder the end of lead  12   a  and end of lead  27  to each other.  
         [0026]    A reference to FIG. 8 shows a partial top view of the substrate platform  41  shown in FIG. 7. In the embodiment shown each of electrical leads  27  and  28  are spaced from each other by a finger separation member  43 , that is a first finger  43   a  is on one side of lead  27  and a second finger  43   b  is on the opposite side of separating member  27 . A third separating finger  43   c  is locate on the opposite side of lead  28 . While only two leads are shown in FIG. 8, it is to be understood that multiple leads can be positioned in the side-by-side and aligned condition shown in FIG. 8.  
         [0027]    In the embodiment shown the lead  27  and lead  12   a  are in alignment with each other as are leads  12   b  and leads  28 . Thus it will be seen that the positioning of the support member  11  through alignment member  42  and the corresponding positioning of leads  27  and  28  by the recess  41   a  in member  41  produces the aligned overlapping condition as shown in FIG. 8. To hold the leads  27  and  28  in place during the securement process the movable jaw  51  clamps on the top of lead  27  and  28  to hold the leads and the transverse member  31  in the alignment recess  41   a  in the substrate platform  41 . As a result the ends of leads  27  and  28  form top alignment with leads  12   b  and  12   a.  The platen  70  for conduction heating the leads  27  and  28  is shown in dotted lines to indicate the positioning for heating to cause the ends of leads  12   b,  and  12   a  to be respectively secured to lead  28   a  and  27  through the melting and subsequent solidification of the solder on the leads.