Abstract:
A method and device for depositing a solder mass within a plated opening that is formed in a side edge of an electronic device includes the steps of carrying the solder mass in a carrier device and orienting the carrier device with respect to the side edge such that the solder mass is aligned with the plated opening. The method further includes reflowing the solder mass to cause the solder mass to be deposited and securely held within the plated opening and then removing the carrier device leaving the solder mass behind within the plated opening and along the side edge of the electronic device.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a U.S. National Phase application under 35. U.S.C. §371 of International Application No. PCT/US2007/070048, filed on May 31, 2007, and claims the benefit of U.S. patent application No. 60/810,032, filed May 31, 2006, both of which are hereby incorporated by reference in their entirety. The International Application was published in English on Dec. 6, 2007 as WO 2007/140448 A2 under PCT Article 21(2). 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to solder-bearing articles, such as devices used for joining electronic components to one another, electrical leads, terminals, electromagnetic shields, and furthermore, to a method for retaining a solder mass along a side edge of the solder-bearing article. 
       BACKGROUND 
       [0003]    It is often necessary and desirable to electrically connect one component to another component. For example, a multi-terminal component, such as a connector, is often electrically connected to a substrate, such as a printed circuit board, so that the contacts or terminals of the component are securely attached to contact pads formed on the substrate to provide an electrical connection therebetween. One preferred technique for securely attaching the component terminals to the contact pads is to use a solder material. 
         [0004]    In the electronic equipment industry, an important necessity is the rapid and accurate assembly of leads, terminals and contacts with contact pads of printed circuit boards (PCB) and other substrates. For convenience of connecting such elements, it has previously been disclosed to facilitate the soldering of their connection by securing a solder slug or mass to one of the elements so that, when positioned in engagement with the other element and heated, the molten solder will cover the adjacent surfaces of both elements to form when cooled a solder joint providing both a mechanical coupling and an electrical connection between the elements. 
         [0005]    One disadvantage of using solder masses is that the solder masses first have to be formed to have the proper dimensions and then the solder masses have to be coupled to solder-holding elements (e.g., solder clips) before the solder reflow operation is performed. This can be a very time consuming and difficult task depending upon the construction of the element that receives the solder, such as a PCB. 
         [0006]    In addition, the construction of some PCBs makes it difficult to electrically connect one planar contact of one PCB to another planar contact of another PCB as is the case when the contacts overlie one another at least partially. 
       SUMMARY 
       [0007]    One embodiment of the invention is directed to a method of depositing a solder mass within a plated opening that is formed in a side edge of an electronic device includes the steps of holding the solder mass in a carrier device and orienting the carrier device with respect to the side edge such that the solder mass is aligned with the plated opening. The method may also include reflowing the solder mass to cause the solder mass to be deposited and securely held within the plated opening and then removing the carrier device leaving the solder mass behind within the plated opening along the side edge of the electronic device. 
         [0008]    The electronic device includes a conductive area, such as a solder pad, that is formed on one face or surface thereof that intersects the side edge at a right angle. The plated opening in the side edge of the electronic device intersects the conductive area and thus provides a means for electrically conducting the conductive area to another conductive area, such as another solder pad, associated with another electronic device. 
         [0009]    Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing and other features of the present invention will be more readily apparent from the following detailed description and drawings of illustrative embodiments of the invention in which: 
           [0011]      FIG. 1  is a perspective view of a printed circuit board (PCB) that has a bisected plated opening formed on an edge of the PCB with a solder pad being connected thereto; 
           [0012]      FIG. 2  is a perspective view of a carrier that is constructed to hold and align a solder mass for placement in the bisected plated opening of the PCB of  FIG. 1 ; 
           [0013]      FIG. 3  is a top plan view of the carrier of  FIG. 2  aligned with the PCB so that the solder mass aligns with the bisected plated opening; 
           [0014]      FIG. 4  is an end elevation view of the carrier of  FIG. 2  aligned with the PCB so that the solder mass aligns with the bisected plated opening; 
           [0015]      FIG. 5  is a perspective of the PCB of  FIG. 1  after the solder mass is deposited into the bisected plated opening and the carrier is removed; and 
           [0016]      FIG. 6  is a top perspective view of the PCB of  FIG. 1  electrically connected to another electronic device by means of reflowing the solder mass. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    As described and illustrated herein, one exemplary solder-bearing article according to the present invention is in the form of a solder-bearing component for use in electrical applications. 
         [0018]      FIG. 1  illustrates a solder bearing article  100  in the form of a printed circuit board (PCB) that has a top surface  102  and an opposite bottom surface  104 , as well as a peripheral edge (side edge)  110  that extends between the top and bottom surfaces  102 ,  104  and defines a thickness of the PCB  100 . Typically, the PCB  100  has a generally square or rectangular shape; however, other shapes are equally possible. The illustrated PCB  100  is a plated, solderable structure in that the PCB  100  includes at least one and preferably a plurality of plated openings  120 . In contrast to common PCB design, the plated openings  120  according to the present embodiment are formed along one or more edges  110  of the PCB  100 . For purpose of illustration only, the illustrated embodiment shows the plated openings  120  formed in one side edge  110  of the PCB  100 ; however, it will be understood that the plated openings  120  can be formed in more than one of the edges  110 . 
         [0019]    In the illustrated embodiment, the plated openings  120  are perpendicular bisected plated opening  120  in that the PCB  100  includes solder pads  130  that are connected to the perpendicularly bisected plated openings  120 . The solder pads  130  can be conventional solder pads; however, the solder pads  130  are arranged on the top surface  102  such that they are orientated perpendicular to the plated openings  120  and such that they intersect the plated openings  120  at a right angle. Each plated opening  120  defines a channel that extends from the bottom surface  104  to the top surface  102  and in the illustrated embodiment, the plated opening  120  has an arcuate surface, such as a semi-circular shaped channel in that it is not a completely closed hole formed through the substrate. The opening  120  is thus an elongated channel formed along the side edge  110 . 
         [0020]    The solder pads  130  can have any number of different shapes so long as they are electrically connected to the plated openings  120 . In other words, the solder pads  130  intersect the plated openings  120 . Since the plated opening  120  has an arcuate shape, the solder pad  130  has an arcuate shaped edge  121  where it intersects the plated opening  120 . The remaining, surrounding shape of the solder pad  130  can be a regular shape, such as a square or rectangle. In the illustrated embodiment, the solder pad  130  has a square shape except for the arcuate shaped edge  121  at the edge  110 . 
         [0021]    Typically, one solder pad  130  is electrically connected to one plated opening  120 . 
         [0022]    Now referring to  FIG. 2  in which a carrier  200  for holding a solder mass  300  is provided; the carrier  200  has a body  210  that includes an elongated strip  220  and a solder-holding conformation  230  that is connected to the elongated strip  220  by means of a neck  240 . The body  210 , or at least a portion thereof, can be formed by any number of conventional techniques, including forming the body  210  by stamping from a material strip. In accordance with an embodiment of the present invention, the carrier  200  is formed of a non-wettable material, relative to solder, with exemplary non-wettable materials including but not limited to aluminum, a plastic, etc. 
         [0023]    The elongated strip  220  includes a plurality of slots or openings  222  that are formed in the strip  220  along a length thereof. In the exemplary embodiment, the openings  222  are formed in the strip  220  at a location where the neck  240  intersects the strip  220 . The neck  240  extends from the upper edge  221  of the strip  220  and is integrally connected to the solder-holding conformation  230 . The solder-holding conformation  230  has a U-shaped body  232  that is defined by a pair of side walls  234  that are spaced apart from one another so as to define a space  235  therebetween. The neck  240  is connected to a base portion  236  of the body  232 , with the side walls  234  extending outwardly therefrom. 
         [0024]    The side walls  234  include a feature that permits the solder mass  300  to be held and carried by the solder-holding conformation  230 . More specifically, each side wall  234  includes an open notch  237  that is formed along an inner edge  239  of the side wall  234 . The notch  237  can have any number of different shapes so long as it can receive and hold an end of solder mass segment  300 . For example, the notch  237  can have an arcuate shape, a square shape, a triangular shape, a rectangular shape, etc., with the illustrated notch  237  having a U-shape. The notches  237  are axially aligned to permit the solder mass  300  to be received within the notches  237  and extend across the space  235 . 
         [0025]    The solder-holding conformation  230  includes a structure, generally indicated at  250 , for “Z” axis alignment to the PCB  100  when the carrier  200  is orientated relative to side edge  110  of the PCB  100  for deposing the solder mass  300  into the plated opening  120 . The structure  250  is in the form of a pair of tabs or protrusions that acts as an alignment and stop mechanism. More specifically and as illustrated, a lower edge  238  of each side wall  234  includes an elongated protrusion  250  that extends outwardly from the inner edge  239  of the side wall  234 . The protrusion (stop)  250  is preferably formed at a right angle to the inner edge  239  such that the protrusion  250  and inner edge  239  form a right angled shoulder. As described below, the spaced protrusions  250  are received along the bottom surface  104  of the PCB  100  and since the edge  110  and the bottom surface  104  are formed at a right angle, they are therefore complementary to the right angle formed between the protrusions  250  and inner edge  239 . 
         [0026]    The solder-holding conformation  230  also includes a structure  260  for shielding the solder pad  130  from wicking of the solder mass  300  during reflow thereof. The structure  260  is in the form of an integral shield/elongated protrusion that extends outwardly from the upper edge  241  of the side wall  234 . The shield  260  thus occupies a significant amount of the area of the space  235  between the side walls  234  at the upper edge  241  thereof. In the illustrated embodiment, the length of the shield  260  is greater than a length of both the protrusions  250  and the side walls  234  and therefore, the shield  260  extends beyond both of these structures. The shield  260  is formed above the notches  237  and therefore, the shield  260  is disposed over the solder mass  300 . 
         [0027]    The use of the carrier  200  for depositing the solder mass  300  into the plated opening  120  of the PCB  100  is described with reference to  FIGS. 1-6 . The solder mass  300  is held by the solder conformation  230  by placing ends of a solder mass segment  300  within the notches  237  such that the solder mass  300  extends across the space  235 . As best shown in  FIG. 3 , the solder mass  300  can be pre-shaped before insertion or depositing the solder mass  300  into the plated opening  120 . For example, the solder mass  300  can be bent in a middle region  302  thereof between the ends of the solder mass  300  so as to form a convex shape that is complementary to the arcuate (e.g., semi-circular) shaped so as to permit the bent portion  302  of the solder mass  300  to be received within the plated opening  120 . By forming a bent portion  302 , the placement/deposition of the solder mass  300  in the plated opening  120  is made easier. 
         [0028]    The carrier  200  is positioned relative to the PCB  100  by aligning the side walls  234  on each side of the plated opening  120  such that the space  235  is aligned with and faces the plated opening  120 . In this orientation, the protrusions (stops)  250  are positioned along the bottom surface  104  of the PCB  100  with the edge  110  in contact with or being placed proximate to the inner edge  239  of the side walls  234 . The protrusions  250 , as well as the inner edge  239 , thus serve as locating features that position and orientate the carrier  200  relative to the PCB  100  as shown in  FIGS. 3-4 . 
         [0029]    As shown in  FIGS. 3-4 , the shield  260  extends above the solder mass  300  and extends at least partially across the solder pad  130  so as to cover an area of the solder pad  130 . In  FIG. 3 , one of the shields  260  is partially broken away to illustrate the underlying solder mass  300  and the plated opening  120 . Once again, when the inner edge  239  seats against the edge  110  of the PCB  100 , the solder mass  300 , and in particular the bent portion  302 , is aligned and deposited into the plated opening  120 . The shield  260  is constructed to prevent molten solder (formed by a reflow operation) from wicking onto the planar solder pad  130  that is disposed on the top surface  102  of the PCB  100 . 
         [0030]      FIGS. 3-4  show the solder mass  300  prior to reflowing the solder mass  300  to cause it to flow into and bond with the plated opening  120  resulting in the addition of solder to plated, solderable structures on the edge  110  of the PCB  100 . The solder mass  300  is then reflowed using conventional techniques, such as applying heat to the solder mass  300 . The heat can be delivered in any number of forms, including hot air that is directed onto the solder mass  300  or the entire assembly can be subjected to an elevated temperature, causing the solder reflow, so long as the printed circuit board (PCB)  100  is not damaged. 
         [0031]      FIG. 5  shows the solder mass  300  deposited in the plated opening  120  after the carrier  200  ( FIG. 2 ) has been removed and at the end of the reflow operation. It will be appreciated that during reflow, the solder mass  300  flows into the arcuate (semi-circular) shaped plated opening  120  and thus, the formed solder deposit has at least a semi-circular shape and more typically, the formed solder deposit has a generally cylindrical shape as shown in  FIG. 5 . The bonding between the deposited solder mass  300  and the plated opening  120  results in the solder mass  300  being securely held within the plated opening  120  and is ready for later use when it is desired to electrically connect the solder pad  130  with another electronic component via the bisected plated opening  120  located at the edge  110 . 
         [0032]    For example,  FIG. 6  shows one exemplary application for the PCB  100  with one or more solder masses  300  deposited along edge  110  within the bisected plated opening  120 . In particular, the PCB  100 , and in particular, the solder pad  130  thereof, is electrically connected to a second electronic component  400 . In the illustrated embodiment, the second electronic component  400  is in the form of a substrate, such as another PCB assembly, that includes a top surface  402 , a bottom surface  404  and a peripheral side wall  406  that extends between the top surface  404  and the bottom surface  404 . The construction of the PCB  400  can be similar or identical to the construction of the PCB  100  and in any event, the PCB  400  includes a number of electronic components  410  formed thereon. For example, the top surface  402  of the PCB  400  can have one or more conductive pads (solder pads)  410  formed thereon that are designed to be electrically connected to electronic components associated with the other electronic device. More specifically, the solder pad  130  of the PCB  100  is to be electrically connected to the solder pad  410  of the PCB  400 . 
         [0033]    The PCB  100  and the secondary PCB  400  represent planar substrates that have complementary planar surfaces to permit one substrate to seat against the other substrate. For example, the PCB  100  as shown in  FIG. 5  can be inverted and the top surface  102  of the PCB  100  can seat against the top surface  402  of the secondary PCB  400  such that at least a portion of the solder pad  130  is in contact with least a portion of the solder pad  410  of the PCB  400  to establish an electrical connection therebetween. In this orientation, the solder mass  300  likewise lies above and in contact with the solder pad  410 . To electrically connect the two electronic components (conductive pads  130 ,  410 ), the solder mass  300  is reflowed to provide and form a robust, filleted solder joint between the two PCBs  100 ,  400  which was otherwise not possible with a one-dimensional planar PCB solder pad (e.g., solder pad  130 ) using conventional soldering techniques. 
         [0034]    Thus, one embodiment of the present invention provides a mechanism for SMT (surface mount technology) attachment of one PCB  100  to another PCB  400  by using conventional PCB solder pads  130 ,  410  that are connected to a perpendicular bisected plated opening and conventional SMT component attachment methods. The use of a perpendicular bisected plated opening (BPO)-PCB solder joint according to the present invention permits a solder joint and an electrical connection between two electronic components (solder pads) that were otherwise not possible. 
         [0035]    More specifically and according to the present invention, the formation of this type of BPO-PCB solder joint is possible due to the addition of solder only on the edge of the PCB and on the inside of the bisected plated opening (through hole). The present method thus provides a device and means for effectively depositing solder only on the inside of the bisected plated opening on the edge of the PCB which has a common solderable surface with the solder pad. 
         [0036]    While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.