Patent Publication Number: US-2006000642-A1

Title: Interposer with compliant pins

Description:
This application claims priority to Provisional Patent Application No. 60/584,895 filed Jul. 1, 2004 which is herein incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION  
      The present invention is related to printed circuit board (PCB) type connectors. More particularly, the present invention is directed to an interposer including a plurality of compliant pins that is suitable for use as a connector or carrier. The present invention also includes a method for making the interposer.  
     BACKGROUND  
      Electronic components such as resistors, transistors, diodes, inductors, capacitors, packaged integrated circuits, and unpackaged dies must interface with other electronic components in an endless variety of systems. It would be desirable to provide a device which allows for electronic components to connect in a mechanically convenient manner, yet provides a high level of electrical performance and scalability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING(S)  
       FIG. 1  is a cross-sectional elevation view of an interposer according to a preferred embodiment of the invention.  
       FIG. 1   a  is a cross-sectional elevation view showing an installation detail of the interposer in the form of a carrier including an electronic component according to a preferred embodiment of the invention.  
       FIG. 2  is a perspective view of a sheet of conductive and resilient material for forming at least one, and more preferably an array of compliant pins according to a preferred embodiment of the invention.  
       FIG. 3  is a perspective view of a portion of the conductive and resilient material sheet representative of each of the areas depicted in dashed line in  FIG. 2 .  
       FIG. 4  is a perspective view of the sheet portion of  FIG. 3  which has been deep drawn to form a body.  
       FIG. 5  is a perspective view of the body with an end of the body being removed.  
       FIG. 6  is a perspective view, partially in cross-section, of the completed compliant pin.  
       FIG. 7  is a perspective view of the completed compliant pin.  
       FIG. 8  is a perspective view of an alternative embodiment of the compliant pin having additional side wall slits.  
       FIG. 9  is a flowchart depicting a process for creating a compliant pin package according to a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
      The present invention will be described with reference to the drawing figures wherein like numerals represent like elements throughout. The terms “down”, “up”, “bottom”, “side” or “top” as used hereinafter are used only for convenience to differentiate certain aspects of the preferred embodiments in the orientation shown in the figures. It should be understood that these terms are not meant to limit the functional aspects of the elements to which the terms apply.  
      Referring to  FIGS. 1 and 9 , the present invention provides an interposer  1  and a method for making the interposer  1 . The interposer  1  includes a printed circuit board (PCB)  6  and a plurality of compliant pins  8  adhered thereto. The PCB  6  includes vias  4  which provide a path between the compliant pins  8  and a top surface of the PCB  6 .  
      The compliant pins  8  are preferably fabricated from a single sheet of conductive and resilient material such as copper (Cu) or beryllium copper (BeCu). Alternatively, brass, phosphorous bronze or other suitable alloys may also be used. Referring to  FIG. 2 , a sheet  10  of conductive and resilient material is shown. Although the sheet  10  is shown as being configured in a generally square shape having a certain thickness, those of skill in the art should realize that this is for convenience of explanation and the shape and/or thickness of the sheet  10  will vary depending upon the particular application and the desired physical characteristics of the compliant pin. Such physical characteristics, for example, may include the impedance of the compliant pin, the desired normal force to be applied by the compliant pin and the working range of the compliant pin. The length and width of the compliant pin, as well as the distance between adjacent ones of the pins (i.e. the pitch) are also factors used in the selection of material composition and thickness.  
      Referring to  FIG. 3 , a partial view of the sheet  10 , representative of each of circular areas depicted in dashed line in  FIG. 2 , is shown. This portion of the sheet  10  corresponds to the areas in which each of the compliant pins  8  is formed.  
      The sheet  10  is drawn to form one or more cavities using a deep drawing process as shown in  FIG. 4 . Deep drawing is a well known process to those of skill in the metallurgical arts and, therefore, a detailed description of the process will not be set forth in detail hereinafter. Generally, however, deep drawing selectively stretches a sheet of material to form a desired three-dimensional shape. The cylindrical shape as shown in  FIG. 4  and the subsequent Figures is for example only and the shape may be any shape desired for the particular application. For example, the body  14  may be substantially rectilinear in shape, or may be drawn much deeper or much more shallow than shown.  
      The body  14  generally comprises one or more side walls  16  and a bottom  18 . The body  14  shown in the figures is substantially cylindrical and slightly tapered toward the bottom to allow easier insertion, and comprises a single continuous wall  16 . However, the body  14  could also be a cubic or other three-dimensional shape, so that there may be a plurality of side walls  16 . Likewise, although a bottom  18  is shown, a deep drawing process may be used such that there is no bottom  18  to the body  14 .  
      If the body  14  includes a bottom  18 , the bottom  18  may optionally be removed as shown in  FIG. 5 . This step is preferably used when it is desired to have a compliant pin with an extended operating range. As such, removing the bottom  18  from the body  14  would have certain operational advantages, although this step is optional and is not required for the compliant pin  8  to operate properly.  
      Referring to  FIGS. 6 and 7 , at least one slit is made in the wall  16  to form an opening  22 . Although preferably at least one opening  22  is formed in the wall  16 , any suitable number of openings can be formed, depending on the required insertion force and normal spring force desired. Referring to  FIG. 9 , for example, an additional opening  23  is added to provide added compliancy in the pin  8 . Alternatively, the pins  8  may be provided without openings.  
      Referring again to  FIG. 1 , the completed sheet  10  with compliant pins  8  is attached to the PCB  6  to form the interposer  1 , preferably using a suitable bonding adhesive such as polyimide, epoxy, silver-filled glass adhesive or other adhesives including pressure sensitive and heat cured adhesives. Depending on the particular application, one or more of the compliant pins  8  are then singulated, preferably using known etching techniques. Alternatively, mechanical or electrical techniques of singulating the compliant pins  8  may be used. Further, it is preferable to plate over the completed interposer  1  to establish electrical continuity between the pins  8  and the vias  4 .  
      Referring to  FIG. 1   a , the interposer  1  may include an electronic component  50  connected to the PCB  6 . In one preferred embodiment, the interposer  1  forms a carrier and the electronic component  50  is a die  30 , enclosed by packaging material  38 , attached to the PCB  6 , preferably through use of a polyimide, epoxy or silver-filled glass adhesive  48 . Bonding wires  32  are attached to bond pads  36  on the die  30 . The bonding wires  32  extend from the bond pads  36  and attach to lead fingers or pads  34  on the PCB  6  which are connected to the vias  4 . Alternatively, the die  30  may be electrically connected to the vias  4  by other known methods. Preferably, the die  30  and bonding wires  32  are covered by the packaging material  38  (represented by the phantom lines) which may include a plastic molding compound. Optionally, a die overcoat may be provided on the surface of the die  30  to reduce induced stresses in the die.  
      Alternatively, the electronic component  50  (represented by the phantom lines) may represent a resistor(s), transistor(s), diode(s), inductor(s), capacitor(s), and/or pre-packaged integrated circuit(s). Further, the electronic component  50  may include other connecting apparatus to allow other devices to connect with the interposer/carrier  1  though the electronic component  50 .  
      The interposer/carrier  1  may be selectively connected to a second printed circuit board (second PCB)  40 . Preferably, the compliant pins  8  are connectable with the plated through holes  42  of the second PCB  40 . The compliant pins  8  provide a spring force radially outwardly against the perimeter of the holes  42  to removably retain the pins  8  in the holes. The removable connection may be made permanent through use of adhesive bonding or other known bonding methods. If openings  22 ,  23  are not provided in the pins  8 , it is preferable the interposer be assembled using solder to attach the pins to the holes  42 . In such an instance, the sheet  10  is preferably Copper (Cu) or a suitable Copper Alloy.  
      The interposer  1  may be connected with cables or other electronic devices. Further, the interposer  1  is a scalable device, and the compliant pins  8  and the PCB  6  may be enlarged or reduced in size to accommodate a variety of electronic devices of different sizes and applications.  
      Referring to  FIG. 9 , a method  200  for making a connector is shown. The method includes deep drawing a conductive material sheet to form a plurality of bodies (step  202 ), removing the closed ends of the bodies (step  204 ), and forming an opening in at least a portion of a side wall of each of the bodies to create compliant pins (step  206 ). The conductive material sheet is attached to a first surface of a PCB which includes vias (step  208 ). Preferably, the compliant pins are singulated (step  210 ). Optionally, some of the compliant pins may remain connected with other ones of the compliant pins as required by the particular application. An electronic component, such as the electronic component  50  of  FIG. 1   a , is connected to a second surface of the PCB and connected to the compliant pins using the vias (step  212 ).  
      One or more of the above-described steps may be omitted and/or performed in a different order. Further, while the preferred method is disclosed, the above-described embodiments of the interposer  1  and the components included therein are not limited by the preferred method. Any suitable method may be employed to construct the disclosed devices.  
      Although the present invention has been described in detail, it is to be understood that the invention is not limited thereto, and that various changes can be made therein without departing from the spirit and scope of the invention, which is defined by the attached claims.