Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-02-22
2001-01-16
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C024S296000, C257S727000, C439S487000
Reexamination Certificate
active
06175499
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a resilient clip holding a heat sink in place against an electronic package within a socket, while simultaneously holding a movable portion of the socket in a locked position, with engagement forces retained between contacts within the socket and pins descending from the electronic package.
2. Background Information
Developments in integrated circuits have resulted in greater circuit density and complexity, increasing the number of pins necessary to connect power and signal lines between an electronic package and the circuit board to which it is attached, and increasing the heat generated by operation of an integrated circuit within the electronic package. These changes in integrated circuits have in turn resulted in increased needs for LIF (Low Insertion Force) and ZIF (Zero Insertion Force) sockets into which electronic packages are inserted, and in increased needs for heat sinks clamped to outer surfaces of electronic packages. The insertion force is the force required to plug the electronic package into a socket, typically arising from the deflection and friction forces acting between the individual pins descending from the electronic package and individual contact springs within the socket. Seating a high pin-count electronic package in a socket without the LIF or ZIF feature can require a force of over 250 pounds.
A ZIF feature is conventionally achieved, within a socket having an array of holes into which the pins descending from an electronic package are inserted, through the use of a sliding locking member operating on the module pins or contact springs within the socket, so that, when the sliding member is in an unlocked position, the pins can be inserted through these holes without contact with the contact springs, or with minimal contact with these springs. As the sliding member is subsequently moved into its locked position, the contact springs exert high contact forces on the pins from the electronic package. These contact forces are used both to provide for the passage of electrical signals between the individual pins and contact springs and to hold the electronic package in place on the socket.
A heat sink is conventionally clamped atop a high-density electronic package by means of a clamping spring extending upward from the socket into which the electronic package is plugged. A thermally conductive grease aids in the transfer of heat from the electronic package to the heat sink. Heat is dissipated from the heat sink into the surrounding air by means of a number of pins or fins extending outward as a part of the heat sink. A suitable force between the electronic package and the heat sink is maintained by the clamping spring. Many of the high-density pluggable electronic modules requiring a ZIF socket, due to a high pin count, also require this kind of a heat sink for proper operation.
Computing devices are being increasingly used in environments, such as manufacturing environments, including relatively high levels of mechanical shock and vibration. It has been determined that, during operation in such an environment, the detent mechanism used to hold the sliding member within the ZIF socket in its closed position is sometimes inadequate, allowing the sliding member to be moved by shock and vibration from its locked position toward its unlocked position. This movement causes the failure of signal transmission as the forces are reduced between individual spring contacts within the socket and individual pins from the electronic module, and conceivably loosens the electronic module from the socket.
Thus, what is needed is a positive method for positively holding the sliding member in its closed position. Preferably, such a method can accomplish this objective without increasing part count or assembly complexity by performing this latching function as a heat sink is clamped in place atop the electronic module.
DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 5,448,449 appears to show, without describing, a method for preventing movement of the sliding member within a ZIF socket. The ZIF socket apparently includes a sliding member operated by pivoting a lever through a 90-degree angle. The heat sink, which is substantially larger in area than the electronic module, is mounted to overextend the lever. Thus the lever must be rotated downward, apparently closing or locking the ZIF connector, before the heat sink is placed on the electronic package. With the heat sink clamped in place on the electronic module, the lever cannot be rotated upward to open or unlock the ZIF connector.
This patent describes a heat sink retainer including a clip having a pair of spaced-apart beams extending within the grooves between fins of the heat sink. The beams are resiliently deflected in respective planes extending parallel to the fins. One end of the clip is engaged beneath a first ledge on one side of the socket, while the opposite end of the clip is pivotally coupled to a latch. The latch is engaged beneath a second ledge on an opposite side of the socket, upon deflection of the beams in their respective planes. The clip assembly biases the heat sink toward the socket when the one end of the clip and the latch are engaged beneath the first and second ledges. A toggle coupled between the clip and the latch is movable between open and closed positions to engage and disengage the latch with the second ledge. The toggle has an overcenter position corresponding to the closed position such that a force must be applied to the toggle to move the toggle from the closed to the open position.
However, this method for holding the ZIF connector closed lacks general applicability. This method requires the presence of a pivoting lever extending upward from the ZIF connector when the connector is open. Many ZIF connectors do not have this feature. Furthermore, this method uses additional space, which is often not available on a circuit board to which a high-density electronic package is attached. The extra space is required on a first side of the socket for the lever itself and for the overextending portion of the heat sink, on a second side extending from the first side for the lever pivot and for a cam mechanism converting the pivoting motion of the lever to lever to operation of the ZIF mechanism, and on a side opposite the second side for the latch and toggle mechanism of the clip assembly.
Thus, what is needed is a mechanism for holding a ZIF connector closed without relying on the presence of an upward-pivoting lever and without requiring substantial space around the electronic module.
A number of U.S. patents describe spring clips for holding heat sinks in place atop circuit modules without addressing the problem of holding a ZIF connector closed. For example, U.S. Pat. No. 5,486,981 describes a spring clip for holding a heat sink in place, with one end of the spring clip being formed into the shape of lever or rocket arm so that heat sink can be attached or removed without the use of tools. U.S. Pat. No. 5,594,624 describes a strap spring mounting a heat sink to an electronic device by snapping holes in a leg over ears of a catch on the socket. Two perpendicularly extending spring have an opening between them so that the spring fit between the fins of a heat sink and are latched in ratchet indentations. U.S. Pat. No. 5,579,205 describes the attachment of a heat sink to an electronic package which is soldered in place on a circuit card, using a frame having legs with lower lips extending between the electronic package and the circuit card.
U.S. Pat. No. 5,602,719 describes a socket having an upper frame which is pivotally connected along an edge to the base of the socket. The electronic module moves with the upper frame, with its pins being moved into and out of contact with contact springs within the base. A heat sink is fastened to the electronic package by means of a spring clip, with one end of the spring clip being clipped onto the base of the socket near the pivotal connection to the upper frame, and with the oth
Adams Stuart Thomas
Cranston, III William Vincent
Hamel Will Eugene
Koenig Jochem K.
McCloskey John E.
Davidge Ronald V.
International Business Machines - Corporation
Tolin Gerald
Tomlin Richard A.
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