Abstract:
A jig securing alignment and positional accuracy in all directions (x, y, z) for an electrical component to be soldered to a PCB is provided. The jig positions the IC in the x and y directions, and keeps the IC from rotating. The jig also holds the IC down during the soldering process to make sure that the IC remains parallel to the PCB before, during and after soldering. The jig attaches to mounting holes on the PCB and its placement can be automated or performed manually.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the earlier filing date of U.S. Provisional Application No. 60/970,123, filed Sep. 5, 2007, entitled “Alignment Jig for Electronic Component,” the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to the assembly of printed circuit boards, and, more particularly, a device and methodology for positioning and retaining an electronic component on a printed circuit board during assembly. 
     Printed circuit boards (PCB) are known in the art for positioning and connecting electronic components, such as integrated circuits (IC), thereon. Typically, the placement and soldering of the ICs onto the PCB is an automated process in which armatures select components from a storage location and place the selected component in a pre-programmed position on the PCB. Printed circuit boards for surface mounted components have flat, usually tin, silver or gold plated copper pads without holes. In such configurations, components are attached to the printed circuit boards by soldering them onto these pads. 
     Prior to soldering, solder paste, a sticky mixture of flux and tiny solder particles, is applied to all the solder pads. After initial placement of all of the components, the PCB moves through a soldering area where the components are soldered to the PCB. In the soldering area the temperature is high enough to melt the solder particles in the solder paste, bonding the component pins to the pads on the circuit board. The surface tension of the molten solder helps keep the components in place, and if the solder pad geometries are correctly designed, surface tension automatically aligns the components on their pads. 
     Some components (an optical sensors, for example) require precise positioning with respect to the PCB or to another object (optical lens, for example). For example, an image sensor and an associated optical lens are to be mounted directly onto a PCB. The PCB has mounting holes for the optical lens. If the sensor is not aligned correctly with the mounting holes in the PCB (and hence the optical lens) the picture quality from the sensor will be less than optimal, and time-consuming adjustments might be necessary. Due to the very small sizes and pin spacing of surface mounted devices (SMD) manual handling and component-level repair is extremely difficult, and often uneconomical. 
     During placement of IC components on the printed circuit board and subsequent soldering process, an IC component may migrate from an initial placement position. Even if the IC is glued to the PCB when initially placed, misalignment in several directions may occur. As illustrated in  FIGS. 1A and 1B , an IC may be misaligned in both x and y directions, and may also be misaligned in rotation (the dotted line  34  in  FIGS. 1A and 1B  illustrates the perfect position for the component pins). Additionally, solder may form under the pins or soldering points of the IC causing a lifting in the z direction (upward from the PCB), as illustrated in  FIG. 1C , and tilting the sensor with respect to the PCB. 
     For most IC&#39;s, for example microprocessors and memory chips, such misalignment does not degrade the performance of the IC as long as the component pins have sufficient contact with the correct solder pads. However, such misalignment may result in severe problems in optical sensor systems. For example, in systems where an optical sensor and its optical lens are connected to the same PCB, the slightest misalignment of the image sensor may cause severe image deterioration. This occurs because once the optical sensor is tilted with respect to the PCB, at least part of the optical sensor may fall outside a focus plane of the lens. 
     One method of accounting for such deficiencies is to align or attach the optics directly to the sensor instead of the PCB, however, this is both expensive and complicated. Furthermore, there are several examples of soldering jigs for connectors, switches and other electric devices, but few of these jigs are intended for electronic components mounted on a PCB. 
     One device intended for preventing components having pins that go through the PCB from lifting during the soldering process, is described in Japanese patent application JP2002261433. This device does not guide or adjust the position of the component and is used for components with pins that go through the PCB. 
     Japanese publication, JP3038089, describes a jig in the form of a frame that is placed around an IC. This solution is intended for surface mounted components and holds the IC in place in the horizontal plane while soldering. However, this soldering jig does not secure the IC in the vertical direction, and is not constructed to guide the IC to a correct position. On the contrary, the cavity of the jig is larger than the IC, requiring manual mounting of the jig on the PCB. 
     The soldering jig of Japanese publication JP10084183 is also placed over a surface mounted IC. This jig, however, is intended to prevent solder bridges by masking the space between each of the pines of an IC during the soldering process. Japanese publication JP6334325 describes a guide pin on the IC and a corresponding tapered part on the PCB to position the IC on the printed circuit board. 
     SUMMARY 
     The present disclosure provides a jig and associated methodology for manufacturing an electronic device that solves the aforementioned deficiencies in the art. 
     An exemplary jig for aligning and supporting an electronic component on a printed circuit board (PCB) includes a frame defining an opening of a size and shape corresponding to at least one part of the electronic component. The jig also includes a plurality of guide members extending from the frame to guide the electronic component into the opening, and mounting pins to engage the printed circuit board, interlocking the jig to the printed circuit board. At least one holding member for supporting a top surface of the electronic component is also included in the jig. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. However, the accompanying drawings and their exemplary depictions do not in any way limit the scope of the disclosure embraced by this specification. The scope of the disclosure embraced by the specification and drawings is defined by the words of the accompanying claims. 
         FIG. 1A  is a first schematic of an electronic component misaligned respective to an optimal position, 
         FIG. 1B  is a second schematic of an electronic component misaligned respective to an optimal position; 
         FIG. 1C  is a third schematic of an electronic component misaligned respective to an optimal position; 
         FIG. 2  is a schematic of a jig according to an exemplary embodiment of the present disclosure and parts of a printed circuit board; 
         FIG. 3A  is a top view schematic of a jig according to an exemplary embodiment of the present disclosure; 
         FIG. 3B  is a bottom view schematic of a jig according to an exemplary embodiment of the present disclosure; 
         FIG. 4  is a schematic of an alternate embodiment of a jig according to the present disclosure; 
         FIG. 5  is a schematic of an alternate embodiment of a jig according to the present disclosure; and 
         FIG. 6  is a schematic of an alternate embodiment of a jig according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes a preferred embodiment by referring to the accompanying drawings. However, people skilled in the art will realize other applications and modifications within the scope of the disclosure. 
     As used herein, the term “component pin” refers to the metallic conductor of an electrical or electronic component that is joined to the printed circuit pattern, for example, the component leads, pins, terminals, lugs, etc. The term “pad” as used herein refers to the metallic pattern on the printed circuit to which the pin is joined. 
     A method and a device (a soldering jig) for correctly positioning, and retaining, during soldering, an IC or similar electronic components on a printed circuit board (PCB) is described herein. 
     As mentioned above, when electrical components are soldered to a PCB, components may be misaligned with respect to an optimal placement position. The misalignment may not be problematic for the electrical connectivity between component pins and soldering pads, but for certain components (such as image sensors) the misalignment may cause serious problems. 
     Referring now to  FIG. 2 , in order to secure good alignment and positional accuracy in all directions (x, y, z) for an electrical component  30  to be soldered to a PCB  31 , a jig  10  according to an exemplary embodiment is utilized. The exemplary jig  10  positions the IC  30  in the x and y directions (sideways, back and forth), in rotation t, and to press the IC  30  against the PCB  31  during the soldering process, ensuring that the IC  30  remains parallel to the PCB  31  before, during and after soldering. 
       FIGS. 3A and 3B  show a top view and bottom view, respectively, of an alignment jig according to one exemplary embodiment of the present disclosure. The jig  10  comprises a frame  13 , a central body  11 , a set of mounting pins  14  and one or a set of supporting structures  12  connecting the central body  11  to the frame  13 . 
     The frame  13  has an opening, confined by the vertical inner surfaces  19  of the frame  13 , having a size and shape corresponding to at least a part of the electronic component  30  to be joined to the PCB  31 . In other words, the inner dimension of the frame  13  is substantially complementary to the outer dimensions of at least parts of the electronic component  30  to be aligned by the jig  10 , and has a substantially complementary shape. Substantially here is a relative term, the scope of which will be known to one of skill in the art as corresponding to deviations in size and shape encountered in mass-produced components to be mounted that are nominally identical. However, the opening in the frame  13  (or the inner dimension of the frame) preferably provides a snug fit around the electronic component  13  (or parts thereof). 
     A set of guiding members are associated with the frame  13  to guide an electronic component  30 , or at least a part of the electronic component  30 , into the opening of frame  13 . According to one exemplary embodiment of the present disclosure, a set of guiding tongues  18  protrude from the bottom of the frame  13 . The guiding tongues  18  are tapered, creating a slope from the vertical inner surface  19 . This embodiment prevents protruding parts of the electronic component  30  (e.g. the component pins) from obstructing or interfering with the frame  13  during alignment. In alternate embodiments the guiding tongues  18  may be anchored to other locations of the frame  13 , central body  11 , or supporting structures  12 . 
     In another exemplary embodiment of the disclosure, the frame  13  itself is chamfered, creating a tapered lower portion  22  (referred to as guiding member) of the frame  13  for guiding the electronic component  30 , or parts of the electronic component  30 , into the opening  19  of the frame  13 , as shown in  FIG. 6 . 
     Also shown in  FIG. 6 , the jig  10  comprises a set of mounting pins  14  extending from of the frame  13 . The mounting pins  14  are designed to engage with a corresponding set of holes  32  in the PCB  31 , and interlock to the PCB  31 . 
     According to the exemplary embodiment of the present disclosure shown in  FIGS. 3A and 3B , the mounting pins  14  comprise a flexible arm  16  with barbs  15 . In this arrangement, the mounting pins  14  are urged through the corresponding set of holes  32  and the barbs  15  engage with the PCB  31  locking the jig  10  to the PCB  31 . Removal of the jig  10  requires the application of pressure to the mounting pins  14 , manually or with the aid of tools, to prevent the barbs  15  from engaging with the PCB  31 . Any type of semi-permanent or quick-release type of locking pin may be used with devices and methodologies described herein. Further, the mounting pins  14  or the holes  32  may be slightly tapered to ease the entry (or guide) of the mounting pins  14  into the holes  32 . 
     Further, the jig  10  comprises one or more holding members for gently pressing the electronic component  30  against the PCB  31 , thereby holding the electronic component  30  parallel to the PCB  31 , and preventing the electronic component  30 , or parts of the electronic component  31 , from lifting during soldering. To ensure a correct fastening of the jig  10  to the PCB  31  and simultaneously provide a firm pressure on the electronic component  30 , the holding members are at least partly elastically pliable under the return force from the electronic component  30 . The holding members would typically interact with the top surface of the component, or parts of the top surface. Exemplary holding members are a set of flexible holding arms  20  extending substantially horizontally from the lowest part of the central member  11 , as shown in  FIG. 3B . The holding arms  20  comprise contact members  21  protruding downward from the distal end of the holding arms  20 . The central member  11  and its holding arms  20  are designed such that the holding arms  20  and/or the contact member  21  are at least partly elastically pliable under the return force of engagement with an electronic component  31 . In other words, when the jig  10  is pressed against an electronic component  30 , the flexible holding arms  20  and/or contact members  21  create a spring-like effect on the electronic component  30 , pressing the electronic component  30  against the PCB  31 . 
     In an alternate embodiment, the holding members are a set of flexible holding arms  20 , extending substantially horizontally from the frame  13 , as shown in  FIG. 4 . The holding arms  20  comprise contact members  21  protruding downward from the distal end of the holding arms  20 . The holding arms  20  and contact members  21  have the characteristics described above regarding flexibility. 
     According to another exemplary embodiment of the present disclosure, the holding member is a spring  23 , or a spring-like object, associated with the central member  11 , as shown in  FIG. 5 . Alternatively, the central body  11  may be formed of an elastomeric material formed to abut an electronic component  30  and compress in the manner of the spring  23 . For example, the central body  11  may be formed of a compressible foam or rubber material having a shape memory for returning to a shape after compression. 
     The exemplary central body  11  is stiffly anchored to the frame  13  by one or a set of supporting members  12 . Further, the central body  11  has a substantially flat top surface. Most pick-and-place machines for electronic components have placement heads comprising a nozzle for holding a component in place by suction. The substantially flat top surface of central member  11  provides compatibility with these traditional pick-an-place machines. 
     In yet another alternative embodiment of the present disclosure, the central member  11  acts as holding member  20  and a set of contact members  21  protrude downwards from the bottom of the central member  11 , as shown in  FIG. 6 . According to this embodiment, supporting members  12  are flexible to provide the elastic pliability to the holding member. Since the central member  11  is not stiffly anchored to the frame  13 , this embodiment may require manual installation or a dedicated pick-and-place machine. 
     Referring back to  FIG. 2 , during the assembly of a PCB  31 , a robot or mechanical armature (pick-and-place machine) picks an IC  30  or other electrical component  30  (e.g. an optical sensor) from a feeder and places it onto the PCB  31 . The robot is programmed to place the electronic component  30  in a correct position such that the component pins  33  align with the soldering pads (not shown) on the PCB  31 . Typically these soldering pads are covered with a solder paste prior to the placement of the electronic component  30 . When the PCB  31  is heated the solder particles in the paste melt and bond the component pins  33  to the pads on the PCB  31 . 
     In  FIG. 2 , the PCB  31  may have guiding/mounting holes  32  in close proximity to the electrical component  30  (in other words, in close proximity to the soldering pads for the electrical component  31 ), which will later be used to mount an object (not shown) in a position relative to the IC  30 , for example an optic lens. Since these holes  32  determine the final position of the object to be mounted, and since the relative position between the electrical component  30  and the object may be crucial, the same mounting holes  32  are used as guiding/mounting holes for the jig  10 . According to another embodiment of the present invention, the PCB may have dedicated guiding/mounting holes for the jig  10 . 
     In operation, as previously noted, when an IC  30  is placed on the PCB  31  there may be misalignment with respect to the mounting holes  32 . For example, the IC  30  may be misplaced slightly sideways (x-direction) or slightly back or forth (y-direction). It may also be slightly rotated, or placed at a wrong angle in the horizontal plane. 
     Therefore, after the IC  30  is placed on the PCB  31 , the robot or armature selects the jig  10  from a feeder and places the jig  10  over the IC  30 . When the robot presses the jig towards the PCB  31 , the mounting pins  14  (or parts of the mounting pins  14 , such as the flexible arms  16 ) on the jig  10  enter the mounting holes  32  in the PCB  31 . The holes  32  act as guiding holes for the jig  10 . The tips of the mounting pins  14  may have a conical shape to easily being able to enter the holes  32  even if the accuracy of the robot is inexact. After the tip of the mounding pins  14  enter the mounting holes  32 , the jig  10  is further pressed towards the PCB  31 . If the IC  30  is not correctly positioned on the PCB  31 , the edges of at least parts of the IC  30  will come in contact with the component guiding members  18  of the frame  13 . When the jig  10  is pressed further towards the PCB  31  the guiding members  18  move the IC  30  into the correct position. Just before the jig is in place, the edges of at least parts of the IC pass the guiding members  18  and enter the part of the frame  13  having substantially vertical edges  19  (also referred to as the opening in the frame  13 ). The tips of the corner pins  14  have small barbs  15  (or hooks) on a side, and parts of the corner pins  14  may be removed to make the pins more flexible, making room for the barbs  15  to pass down through the holes  32 . When the jig  10  is in a final position, completely against the PCB  31 , the barbs  15  exit the holes  32  on the other side of the PCB  31  and lock the jig  10  to the PCB  31 . 
     As the jig  10  approaches the final position, the elastically pliable holding member, and contact members  21 , engage the top surface of the IC  30  and flex, creating a constant hold-down force on the IC  30 . The barbs  15  on one side of the PCB  31  and the holding member on the other side of the PCB  31 , lock the jig  10  and the IC  30  to the PCB  31 . The jig  10 , firmly held on the PCB  31  and secured by the barbs  15  (or hooks), positions the IC  30  correctly in the x, y and rotational directions. Further, the jig  10  prevents the IC  30  from tilting relative to the PCB  31 . 
     With the Jig  10  and the IC  30  firmly attached, the PCB  31  can move through the soldering zone where the solder particles in the solder paste are heated to their melting point. The pins  33  of the IC  30  are bonded to the PCB&#39;s solder pads as the PCB  31  cools. During the soldering process the IC  30  is held in position by the jig  10  and pressed against the solder pads of the PCB  31 , preventing lifting and/or tilting. 
     During testing and further handling of the PCB  31  the jig  10  protects the IC  30 . To mount an object (e.g. optic lens) relative to the IC  30 , the jig  10  may easily be removed by compressing the barbs  15  (or at least parts of the pins) at the underside of the PCB  31  until the barbs  15  release from the PCB  31 . The object (e.g. optical lens) may use the same mounting holes  32  as the jig  10 ; hence the object (e.g. optical lens) is automatically aligned with respect to the IC  30 . 
     According to one exemplary embodiment of the invention, the jig  10  is permanently attached to the PCB  31 . An object may then be mounted on the jig  10  instead of the PCB  31 . The jig  10  also has other features that ensure a safe function. For example, the central body  11  of the jig  10  has a substantially flat and smooth top surface, enabling a robot or armature (or pick-and-place machine) to use a vacuum pickup device to hold the jig  10  during assembly. The robot or armature may also use the central body  11  to press the jig  10  onto the PCB  31 . Further, to press the mounting pins  14  firmly and evenly, the central body  11  is connected to the frame  13  of the jig  10  by rigid arms  12  extending from the center body  11  outward to the frame  13 . 
     To be able to withstand high soldering temperatures jig  10  should be made of a heat resistant material, such as a heat resistant plastic, for example polyamides. The jig  10  may be injection molded in a suitable high temperature polymer material, reaction injection molded, or created by any suitable production technique. The jig  10  may be made of metal. However, the shape of the jig  10  should not significantly change during high temperature soldering, and the support members  12  pressing the IC  30  against the PCB  31  should not lose stiffness. The jig  10  may have any number of mounting pins  14 . 
     The jig  10  according to the present disclosure correctly positions an IC  30  relative to soldering pads on a PCB  31 , and presses the IC  30  against the PCB  31  during soldering procedures, thereby preventing the IC  30  from moving both in the horizontal and vertical plane. Further, the jig  10  positions an IC  30  with respect to a set of mounting holes  32 , used, for example, to mount optics or other objects that are to be mounted to the PCB  31  at a later stage of assembly, and that need to be precisely positioned relative to the IC  30 . 
     The jig may easily be handled (picked and placed) by a robot or armature (pick-and-place machine), and may easily be removed (snapped off) automatically or manually. As can be appreciated, the jig  10  protects the IC  30  during testing and further handling of the PCB  31 . 
     Further, the jig  10  prevents expensive, time consuming manual correction of faulty soldered IC&#39;s, reducing production cost and increasing product quality. 
     The foregoing discussion discloses merely exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present advancement is intended to be illustrative, but not limiting of the scope of the advancement, as well as other claims. The disclosure, including any readily discernible variants of the teachings herein, define, in part, the scope of the foregoing terminology.