Abstract:
Apparatus including a body as an intermediary between a device and a printed circuit board, the body including a contact area defined by a plurality of openings each to accommodate a contact therethrough and an alignment feature adjacent the contact area and protruding from a plane defined by the contact area, wherein a surface of the alignment feature includes a friction-reducing material. A method including contacting an alignment feature of a socket with a friction-reducing material. Apparatus and system including a body as an intermediary between a device and a printed circuit board; a plurality of contacts each disposed through a contact area of the body and oriented to deflect a device in a first direction; and a load plate coupled to the body and configured to apply an actuation force on a device in a different second direction. A method including inserting a device into a socket.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    Semiconductor packaging. 
         [0003]    2. Description 
         [0004]    Land Grid Array (LGA) packaging technology offers many advantages in terms of device manufacturing, high I/O density, low inductance, ease of upgrade, and cost. 
         [0005]    An LGA socket is typically used to attach a LGA device such as a packaged chip to a printed circuit board (PCB). The typical loading required for LGA contact deflection generates lateral device (e.g., package) displacement driven by contact-to-device frictional forces. Package lateral displacement may continue until the device (e.g., package) comes in contact with the socket sidewall. Subsequently, frictional forces are generated between the device and the socket sidewall that can result in electrical opens or package damage through, for example, deformation to the device sidewalls or even breaking them. 
         [0006]    Existing techniques to reduce the resultant friction force and moment during socket actuation have a number of drawbacks. Most LGA sockets or connectors have the LGA contacts wiping in one direction. While this configuration may be acceptable when the number of contacts is a few hundred, the resultant friction force and moment become significant when the number of contacts exceeds 1,000. Another technique lays out the LGA contacts into two diagonal triangular areas on a square socket with a square central cavity. However, when the socket or the central cavity is not square, some amount of moment results in reaction forces on the socket sidewall. In addition, the number of contacts in each row may be different in one area, causing complexities in manufacturing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Embodiments may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments. In the drawings: 
           [0008]      FIG. 1  is an exploded top view of an embodiment of an assembly including socket and a device (e.g., package and chip) to be positioned within the socket. 
           [0009]      FIG. 2  shows a schematic side view of an assembly including a device positioned over a contact area of the socket prior to electrical connection between the device and the socket. 
           [0010]      FIG. 3  shows the assembly of  FIG. 2  following the electrical connection of the device and the socket. 
           [0011]      FIG. 4  shows a magnified view of a portion of the socket of  FIG. 1  and shows a friction-reducing material on the package-locating sidewall feature. 
           [0012]      FIG. 5  shows the magnified view of a portion of the socket of  FIG. 1  and shows a device (e.g., package and chip) positioned in the socket. 
           [0013]      FIG. 6  shows a schematic top side view of an assembly including a hinged socket with a hinged door in a partially opened position and a device (e.g., package and chip) positioned above a contact area of the socket. 
           [0014]      FIG. 7  shows the assembly of  FIG. 6  with the device loaded into the socket and the hinged door closed. 
           [0015]      FIG. 8  shows a computer system including a socket mounted on a printed circuit board. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  illustrates a top partially exploded view of a representation of an integrated circuit system that might be used, for example, in a computing device, wireless communication device, computer-related peripheral, or entertainment device. In this embodiment, system  100  includes printed circuit board (PCB)  110 , device  120 , and socket  130 . 
         [0017]    PCB  110  is any PCB that may contain circuits and devices used in a processing system. PCB  110  may be a multi-layer board made of materials such as epoxy and FR4. It may include copper clad, microwave, and rigid and/or flexible laminates, etc. It typically meets a broad range of thermal and electrical requirements of various systems. It may be a motherboard or a main board in a computer system, an expansion board that plugs into an expansion slot, a daughter card that is attached directly to another board, or an adapter that contains special devices or processors such as video, graphics, network, etc. PCB  110  is typically populated with many devices having various packaging type such as surface mount, ball grid array (BGA), microBGA, pin grid array (PGA), Land Grid Array (LGA), small outline integrated circuit (SOIC), quad flat pack (QFP), Thin Small Outline Package (TSOP), Chip Carrier (CC), Chip Scale Package (CSP), etc. PCB  110  had traces, pads, vias and other elements to provide electrical connections that connect devices or components together. 
         [0018]    Device  120  is any device that is encapsulated with a proper package compatible with socket  130 . In particular, device  120  is packaged with a LGA package. Typically device  120  has a very high pin count, ranging from several hundred pins to over a thousand pins.  FIG. 1  shows device  120  as a LGA package including chip  125 . Chip  125  may be, for example, a microprocessor, a digital signal processor, a network processor, a graphics co-processor, a floating-point co-processor, a micro-controller, an integrated controller hub, or any complex device. 
         [0019]    Socket  130  is used to hold device  120  firmly and provide electrical contacts between device  120  and PCB  110  (e.g., an intermediary between the device (e.g., package and chip) and the PCB). It is mounted on PCB  110  (and provides electrical contact with PCB  110 ) through a re-flow soldering process or any other mounting techniques. Socket  130  provides mechanical, thermal, and electrical support to allow device  120  to be attached to PCB  1   10 . It may include housing  140  and contact area  150 . Housing  140  is a frame to provide mechanical encapsulation for the device. Contact area  150  contains contacts to provide electrical connections between PCB  110  and the pads on device  120  when device  120  is inserted into socket  130 . When fully inserted, device  120  typically occupies substantially all of the inner surface of socket  130  within housing  140 . Socket  130  is designed to be compatible with an LGA device. However, an embodiment may be used for other types of sockets as long as there are a number of contacts that provide electrical connection between a PCB and a device when the device is inserted into the socket. 
         [0020]      FIG. 2  and  FIG. 3  schematically illustrate the locating and placement of device  120  into socket  130  such as an LGA socket.  FIG. 2  shows device  120  positioned within socket  130  (i.e., within housing  140 ) and occupying an area substantially equivalent to contact area  150 . Electrical connection between device  120  and socket  130  at this point has not been made.  FIG. 2  shows device  120  including a number of contacts  160  extending from a surface opposite the surface including chip  125 . Contacts  160  extend from the surface of socket  130  (an upper surface as viewed) at an angle, α, that is less than 90 degrees. In this way, when a force is applied normal or perpendicular to a surface of device  120  (the upper surface as viewed), device  120  actuates laterally as shown by actuation force  165  as the contacts are placed in socket  130 . 
         [0021]      FIG. 3  shows contacts  160  electrically connected to socket  130 .  FIG. 3  also shows the contacting of device  120  with a sidewall of socket  130  (at contact point  170 ). The contact of device  120  with a sidewall of socket  130  causes a friction force between device  120  (the package of device  120 ) and socket  130 . When friction force  170  is higher than an insertion force, device  120  cannot be placed into socket  130 . If the friction force is higher than the yield strength of device  120 , however, then device  120  will yield causing package damage and possibly electrical signal loss between chip  125  and socket  130 . 
         [0022]    In one embodiment, friction force  170  is reduced by incorporating or applying a friction-reducing material into/onto socket  130  (e.g., on one or more of the sidewalls of socket  130  that define contact area  150 ).  FIG. 4  shows a magnified view of one corner of socket  130  and illustrates package-locating sidewall feature or datum  180 A and package-locating sidewall feature or datum  180 B that are used as alignment features to position device  120  within socket  130  and that define contact area  150 . In one embodiment, socket  130  includes datum  180 A and datum  180 B that are made of a low-friction material surface or coated with a friction-reducing material/lubricant. In one embodiment, a material for datum  180 A and datum  180 B or a material layer on datum  180 A and datum  180 B (e.g., material layer  185 ) is selected such that it can withstand a solder melt temperature (SMT) that would be used to bond socket  130  to a PCB. One suitable material is a polytetrafluoroethylene, such as TEFLON®. A metallic material would also be suitable. In the embodiment shown in  FIG. 4 , an inset shows material layer  185  of a friction-reducing material/lubricant a polytetrafluoroethylene, such as TEFLON® coated on a sidewall of datum features  180  where a device may be actuated against the sidewall. A friction-reducing material may be used to fabricate socket  130  such as by molding socket  130  of a friction-reducing material. Alternatively, socket  130  may be made of a material (e.g., plastic material) that may not have friction-reducing material properties and the data of the socket may be coated, such as by spraying or dipping with a friction-reducing material. 
         [0023]    Friction may be described as the coefficient of friction (COF) time a force (i.e., resultant normal force perpendicular to the friction surface). A typical COF between a device (e.g., a chip package) and a socket housing a 0.3 to 0.4. The typical COF between a device and TEFLON coated polymer is 0.04 to 0.1. Thus, by using a friction-reducing material such as TEFLON, the friction force can be reduced by 70 percent to 80 percent thus easing insertion of a device into a socket and significantly reducing the chance to damage the device (i.e., the package). 
         [0024]      FIG. 5  shows device  120  positioned within socket  130  and adjacent (contacting) sidewall surfaces of datum  180 A and datum  180 B. The low friction force material of datum  180 A and datum  180 B will inhibit the ability of device  120  from binding against the socket sidewall during package installation and subsequent loading. By inhibiting the aforementioned binding, electrical opens and package damage failure mechanism are minimized. 
         [0025]    The above embodiment has been described with respect to a LGA socket. It is appreciated that the embodiment may have application for alternate designs. It may be, for example, have applications in PGA-style socket where frictional forces need to be overcome to actuate the socket/package interconnect. 
         [0026]    As noted above, the typical loading for LGA contact deflections generate lateral device (e.g., package) displacement driven by contact-to-device frictional forces. Device lateral displacement occurs until the device substrate (e.g., package) comes in contact with a socket sidewall. Subsequently, frictional forces are generated between the substrate and the socket sidewall that can result in electrical opens or device damage (e.g., package damage). Utilizing friction-reducing material on one or more of the package datum may minimize the frictional force. Alternatively, or additionally, the package may be configured so that an opposing force vector may be applied during device loading that reduces a friction force associated with device loading. 
         [0027]      FIG. 6  shows an embodiment of a hinged-device-socket-loading mechanism in an unloaded state with device  220  position to be loaded into socket. Representatively, socket  230  is a direct load socket such as an LGA775 SKT DSL or an independent loading mechanism such as SKT B ILM. Socket  230  includes, in this embodiment, contact area  260  including contacts  255  to provide electrical connection between a PCB (not shown) and pad on device  220  when device  220  is inserted into socket  230 . Socket  230  also includes hinged door  235  and locking arm  236 . When device  220  is positioned within socket  230  (within contact area  250 ), hinged door  235  is rotated downward (clockwise as shown toward a contact area) and is used to apply an actuation force (illustrated by arrow  270 ) to device  220  and to secure the device in the socket. Locking arm  236  is then rotated downward (counterclockwise as shown) to secure hinged door  235  in place on device  220 . 
         [0028]    In one embodiment, contacts  255  of socket  230  are configured such that where device  220  (e.g., of a chip in package) is placed into contact area  250  and a force applied to electrically connect contact pads on device  220  with contacts  255 , the contact force will be in a direction (illustrated by arrow  280 ) opposite actuation force  270  of hinged door  235 . In this manner, device  220  will be actuated toward the hinge of hinged door  235 . The force vectors represented by arrow  270  and arrow  280  will offset one another thereby minimizing contact frictional forces. It is appreciated that contacts  255  are typically placed in socket  230  once the socket is formed. Thus, at such point, the orientation of contacts may be selected. 
         [0029]      FIG. 7  shows device  220  positioned in contact area  250  with contacts  255  (not shown) providing an electrical connection between contact pads on device  220  and a PCB to which socket  230  may be attached.  FIG. 7  shows hinged door  235  in ghost lines. 
         [0030]    In the above embodiments described with reference to  FIGS. 6 and 7 , opposing force orientations are utilized between a hinged socket loading mechanism and a contact deflection direction. This may be achieved with a direct socket load socket by designing a socket and loading mechanism to support offsetting force vectors. Sockets may be formed by molding the housing, inserting contacts, applying solder balls, and attaching a pick and place cap. The loading mechanism may then be fabricated and attached to the socket adhering to an opposing force configurations described above. The socket may then be soldered to a printed circuit board and a device, such as a package containing a chip inserted into a contact area of the socket and the socket loading mechanism actuated. For an independent loading mechanism, the socket and loading mechanism may be designed to support offsetting vectors, with the socket fabricated and soldered to the PCB. The loading mechanism may then be attached on a device such as a package and the package inserted into a contact area of the socket and the socket loading mechanism actuated. 
         [0031]      FIG. 8  shows a cross-sectional side view of a socket including an integrated circuit package that is physically and electrically connected to a printed wiring board or printed circuit board (PCB) to form an electronic assembly. The electronic assembly can be part of an electronic system such as a computer (e.g., desktop, laptop, handheld, server, etc.), wireless communication device (e.g., cellular phone, cordless phone, pager, etc.), computer-related peripheral (e.g., printer, scanner, monitor, etc.), entertainment device (e.g., television, radio, stereo, tape and compact disc player, video cassette recorder, MP3 (motion picture experts group, audio layer  3  player, etc.), and the like.  FIG. 8  illustrates the electronic assembly is part of a desktop computer.  FIG. 8  shows electronic assembly  300  including socket  310 , configured as described in one or more embodiment described with reference to  FIGS. 1-7  and the accompanying text, physically and electrically connected to printed circuit board  820  such as a motherboard or other circuit board. Socket  810  includes a packaged chip. Electrical contact points, e.g., contact pads on a surface of the chip are connected to the package through, for example, a conductive bump layer. Electrical contact points of socket  310  may be similarly soldered to printed circuit board  320 . The package is electrically connected to socket  310  through contacts as described above. 
         [0032]    In the preceding detailed description, reference is made to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.