Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Device held in place by clamping
Reexamination Certificate
2000-05-02
2001-11-06
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Device held in place by clamping
C257S780000
Reexamination Certificate
active
06313530
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to making connections between integrated circuit array packages (IC) and circuit boards.
Ball grid array (BGA) and land grid array (LGA) packages are becoming increasingly popular because of their low profiles and high densities. With a BGA package, for example, the rounded solder balls of the BGA are generally soldered directly to corresponding surface mount pads of a printed circuit board rather than to plated thru-holes which receive pins from, for example, a pin grid array IC package.
Sockets are used to allow particular IC packages to be interchanged without permanent connection to a circuit board. More recently, sockets for use with BGA and LGA packages have been developed to allow these packages to be non-permanently connected (e.g., for testing) to a circuit board. However, problems can exist in attaching a BGA package to conventional sockets. This is because a BGA package presents a non-traditional mating condition. The rounded solder balls of the BGA are themselves relatively poor points of contact for socketing, suited only for their intended purpose of being reflowed. Further, the co-planarity between the individual points of contact for each rounded solder ball may be lacking due to ball irregularities and warping of the BGA package.
SUMMARY OF THE INVENTION
This invention features a socket terminal assembly which provides a reliable, non-permanent and low-loss electrical interconnection between electrical contacting areas of an array package and connection regions of a substrate (e.g., printed circuit board) while duplicating the mating condition normally present between the electrical contacting areas and connection regions. The term “integrated circuit array package” is intended to mean those packages, including PGA (pin grid array), BGA and LGA packages. The term “substrate” is intended to mean any base member having electrical contact areas including printed circuit boards, IC chip substrates or the packages supporting such chip substrates.
In one aspect of the invention, the socket terminal assembly includes a contact spring, disposed within an opening of a socket body, to receive and apply a frictional force sufficient to retain a pin within the opening of the socket body; and a resilient member, disposed within the opening, to apply, in response to a downward force applied to the pin, an upward force to the pin sufficient to overcome the frictional force of the contact spring. The pin is adapted to contact the electrical contacting area of the integrated circuit array package. The socket body has an end configured to contact the corresponding connection region of the substrate and an opposite end having the opening for receiving the lower end of the pin.
Preferred embodiments of this aspect of the invention may include one or more of the following features. The contact spring is configured to provide a “wiping”, reliable electrical contact in which the frictional force sufficient to retain the pin within the socket body is in a direction substantially transverse to the upward force applied by the resilient member. For example, the contact spring includes resilient spring fingers which frictionally engage the lower end of the pin. The resilient member for applying the upward force, on the other hand, is in the form of a coiled conductive spring, or alternatively, in the form of an elastomeric material (e.g., rubber).
The lower end of the socket body is ball-shaped or may include a solder ball attached thereto. The upper end of the pin includes a ball-contacting surface which is concave to receive a ball-shaped contact of a ball grid array package. A sharp protuberance extending from the ball-contacting surface may be provided to pierce the surface of the ball-shaped contact. The sharp protuberance is conically-shaped and disposed along the longitudinal axis of the pin. In other embodiments, the sharp protuberance may be ring-shaped and disposed concentric with the longitudinal axis. Alternatively, the upper end of the pin includes particle interconnections.
In another aspect of the invention, an intercoupling component (e.g., a socket assembly) includes a number of socket terminal assemblies, of the type described above, all of which are positioned within an array of holes or apertures in an insulative support member and configured to electrically connect the electrical contacting areas of the integrated circuit array package with the array of connection regions of the substrate. The array of holes in the support member are located in a pattern corresponding to the array of electrical connection regions of the substrate.
An intercoupling component having this arrangement eliminates the need for soldering the package directly to a circuit board (e.g., motherboard) and allows removing the integrated circuit array package in situations where the package needs to be repaired or replaced.
Preferred embodiments of this aspect of the invention may include one or more of the following features. The intercoupling component further includes an electrically insulative sheet coupled to the pins and having holes arranged in a pattern of the connection contacts. The sheet is formed, for example, of a polyimide film and adapted to retain the pins in a ganged arrangement. The intercoupling component further includes a member which applies a downward force on the contact area of the integrated circuit package and to each pin to cause the resilient member to compress. The member is a heat sink threadingly received within a cover positioned over the integrated circuit package. The terminal support member includes alignment elements to align the contacting area of the integrated circuit package to corresponding ones of the connection regions.
In another aspect of the invention, an intercoupling component includes a retaining member coupled to a plurality of pins received within a corresponding plurality of sockets which, in turn, are received within a socket support member having a detent. The returning member is configured to cooperate with the detent so that each of the pins are maintained with the sockets.
Preferred embodiments of this aspect of the invention may include one or more of the following features. The retaining member includes a relatively thin, electrically insulative, flexible sheet member (e.g., formed of polyimide) having holes extending therethrough and arranged in a planar configuration about the sheet to correspond with the predetermined positioning of the pins in the sockets. Each of the pins includes a head at the upper end of the pin, the head having an inwardly extending groove along its periphery. Each hole of the flexible sheet has a peripheral edge extending into a corresponding groove of the head of the pin. The detent is an opening formed in a sidewall which extends vertically from the upper surface of the socket support member and receives an edge of the flexible sheet. A detent may be formed in each of a pair of opposing sidewalls of the socket support member.
In another aspect of the invention, a terminal for electrically connect a solder ball contact area of a ball grid array package to a corresponding connection region of a substrate includes a head having a ball-contacting surface with a sharp protuberance extending vertically from a lowest point of the ball-contacting surface and below a highest point of the ball-contacting surface. The ball-contacting surface is concave and conically-shaped to receive the solder ball contact area. The sharp protuberance is configured to pierce the surface of the solder ball.
In embodiments of this aspect of the invention, the sharp protuberance is conically-shaped and lies along the longitudinal axis of the terminal. Alternatively, the sharp protuberance may be ring-shaped and disposed concentric with the longitudinal axis.
Other features of the invention will be apparent from the following description of the preferred embodiments and from the claims.
REFERENCES:
patent: 4616895 (1986-10-01), Yoshizaki et al.
patent: 4750890 (1988-06-01), Dube et al.
p
Advanced Interconnections Corporation
Clark Sheila V.
Fish & Richardson P.C.
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