GB2342510A

GB2342510A - Zif socket for an electronic package

Info

Publication number: GB2342510A
Application number: GB9821775A
Authority: GB
Inventors: James P Scholz
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1997-10-10
Filing date: 1998-10-06
Publication date: 2000-04-12
Anticipated expiration: 2018-10-06
Also published as: JPH11195470A; GB2342510B; GB9821775D0; TW383961U

Abstract

A socket for an electronic package of the type having a plurality of depending leads includes a base 10 and a cover 20. The base holds a plurality of contacts 40 in respective cavities 15. Each of the contacts has a resilient contact arm 45. The cover is transversely movable over the base between open and closed positions and has a plurality of projections 27 which are engageable with the contact arms. When the cover is in the open position, the contact arms are deflected by the projections so that the leads can be freely installed in the cavities along vertical insertion paths. The cover is movable to the closed position without transverse movement of the leads. When the cover is moved to the closed position, the contact arms resile into engagement with the leads without transverse movement of the leads.

Description

ZIF SOCKET FOR AN ELECTRONIC PACKAGE The invention relates to a zero insertion force socket for an electronic package having a plurality of depending leads.

Electrical sockets are known for removably mounting integrated circuit (IC) packages on a circuit board.

Such sockets have a plurality of contacts which are engageable with leads of the IC package. The contacts typically exert resilient forces on the leads to provide reliable electrical connections with the leads and to secure the package to the socket. These resilient forces must be overcome when installing the package on the socket or removing the package from the socket. For an IC package, such as, a pin grid array (PGA) package which has a multitude of leads in the form of depending pins, resilient forces during installation and withdrawal can be excessively high. In order to overcome this problem and to accommodate IC packages with greater numbers of leads, zero insertion force (ZIF) sockets have been developed. The prior art ZIF sockets have a mechanism which permits the package to be installed on the socket in a first position without resistance prior to electrical mating. The package is then moved on the socket to a second position wherein the leads of the package electrically engage the contacts in the socket.

U. S. Patent No. 5,649,836 discloses a ZIF socket including a base which holds a plurality of contacts in respective cavities, and a cover which is transversely movable over the base. The cover has a top surface which supports an IC package, and a lower surface with a plurality of protruding preload projections which correspond to the plurality of contacts in the base.

Each of the contacts has a pair of opposed resilient contact arms. The preload projections are arranged to enter between and expand the contact arms when the cover is moved in one direction so that the leads of the PC package can be freely inserted into the cavities.

Movement of the cover in a reverse direction withdraws the preload projections from between the arms while simultaneously moving the leads of the IC package so that the leads become engaged between the arms. As a result, the 1C package moves transversely back and forth over the socket during insertion and withdrawal of the package into and from the socket.

A new 7C packaging scheme currently in development does not allow for transverse movement of the IC package on the socket. There is a need for a socket that exhibits low insertion and withdrawal forces on an IC package and which does not recuire transverse movement of the IC package.

The invention is a socket for an electronic package having a plurality of depending leads, the socket comprising : a base having a top surface and a plurality of cavities that are open through the top surface, each of the cavities including a reception zone for receiving a respective said lead along a vertical insertion path, the base holding a plurality of contacts each having a resilient contact arm that in a free state extends into a respective said reception zone, the socket including a cover which is mounted for transverse movement over the top surface between open and closed positions, the cover having a plurality of projections which extend into the cavities and which are arranged to resiliently deflect the contact arms when the cover is in the open position, the cover having a plurality of apertures wherein the leads of the electronic package can be inserted through the apertures and into the reception zones when the cover is in the open position, the apertures extending g transversely in the cover wherein the cover is movable to the closed position without transverse movement of the leads, and wherein moving the cover to the closed position moves the projections and permits the contact arms to resile into engagement with the leads, thereby electrically connecting the contacts and the leads without transverse movement of the leads.

The invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is an isometric view of an electrical socket according to the invention; Fig. 2 is a top plan view of the socket ; Fig. 3 is a cross-sectional view taken along a portion of line 3-3 of Fig. 2 showing contacts disposed in cavities and a cover in a closed position; Fig. 4 is an enlarged top view of one of the cavities with the cover in the closed position ; Fig. 5 is a cross-sectional view similar to Fig. 3 with the cover in an open position; Fig. 6 is an enlarged top view of one of the cavities with the cover in the closed position; and Fig. 7 is an isometric view of a contact which is used in the socket.

With reference to Figs. 1-3, a socket according to the invention comprises a base 10, a cover 20, and an actuator 30. The socket is adapted to receive an electronic package (not shown) of the type which'has an array of leads depending from a bottom surface thereof, such as pins of a pin grid array (PGA) package. The socket permits the electronic package to be electrically connected to and removably mounted on a circuit board (not shown).

The base 10 comprises a dielectric housing 12 having a top surface 13 and a bottom surface 14. The base 10 holds a plurality of contacts 40 in respective cavities 15 which are open through the top surface 13.

The cover 20 is slidably mounted on the base 10 for transverse movement in a horizontal plane in forward and reverse directions X. The cover 20 is guided for transverse movement by depending sides 22 which straddle the base. The cover has a plurality of apertures 24 which extend through the cover between top and bottom surfaces 25,26. The plurality of apertures 24 correspond to and are in registration with the plurality of cavities 15 in the base.

The actuator 30 is pivotally coupled to the base 10 on a pivot pin 32 having a vertical axis A. The actuator has a handle end 34 which can be moved in an arc B, and a camming end 35 which is disposed between the base and the cover. The camming end has a sloz 36 with walls which are configured as cam surfaces to operate on a cam follower 23 that is held by the cover 2C. The cover is movable transversely in the X direction by pivoting the actuator through the arc B.

The cover is movable between a closed position shown in Fig. 3 and an open position shown in Fig. 5. The actuator has projections 37 which cooperate with latch tips 18 on the base 10 to hold the actuator in positions corresponding to the closed and open positions of the cover. Further details of an actuator which can be used with the present invention are disclosed in U. S. patent application serial number 08/854,310 filed May 12, 1997, which application is assigne to the The Whitaker Corporation and is incorporated by reference as if set forth fully herein.

Or. of the contacts 40 is shown in deta l in Fig.

7. The contact 40 is an electrically conductive body having a base portion 42 that is fixed in the housing 12 by an interterence fit within in a pocket in the bottom su-face 14 of the housing. mhe cortact 40 has an upstanding main beam 43 which transitions through a bend 44 to a downwardly sloping resilient contact arm 45 that has a contact nose 46 and a free end 47. An extension 48 of the base portion has an undersurface 49 to which a solder ball 5C is attached, as shown in Fig. 3. The solder ball 50 extends below the bottom surface 14 to serve as a lead for connection with a circuit trace on a circuit board (not shown).

Reference will now be made to Figs. 3 and 4 wherein the cover is shown in a closed position, and to Figs. 5 and 6 wherein the cover is shown in an open position.

Each of the cavities 15 includes a reception zone 16 and a channel 17. The reception zone 16 is configured for receiving a lead of the electronic package. In the present example, the reception zone 16 is cylindrical for receiving a pin of a pin grid array package. The reception zone 16 and the channel 17 are open to each other. The contact arm 45 of a respective contact is disposed in the channel 17 and, in a free state (closed position of the cover), the contact arm 45 extends into the reception zone 16 so that the contact nose 46 will engage a lead that is inserted in the reception zone.

Each of the contact arms 45 slopes downwardly at an oblique angle and the contact noses 46 are disposed in the reception zones 16. The cover 20 has a plurality of projections 27 which extend below the bottom surface 26 and into the cavities 15. The projections 27 are configured to engage and deflect the contact arms 45 into their respective channels 17 when the cover is moved to the open position, as shown in Figs. 5 and 6.

The contact arms are deflected in respective vertical planes that are perpendicular to the transverse movement of the cover. Deflection of the contact arms 45 withdraws the contact noses 46 from the reception zones 16, thereby clearing the reception zones of obstruction.

When the cover is in the open position, the leads of an electronic package can be installed into the reception zones along vertical insertion paths without resistance.

The apertures 24 in the cover are transversely elongated so that the cover can be moved to the closed position with transverse movement of the leads. When the cover is returned to the closed position as shown in Figs. 3 and 4, the projections 27 are disengaged from the contact arms 45 and the arms are allowed to resile into biasing engagement with the leads in the reception zones. In the closed position, the contact arms 45 exert normal forces on the leads through the contact noses 46.

Thus, a substantial withdrawal force must be exerted on the package in order to withdraw the package from the socket when the cover is in the closed position.

The invention provides a zero insertion force socket having a cover which is slidable on a base between open and closed positions. The socket has the advantage that no transverse movement of the electronic package on the socket is required. In the event that installation of the package is attempted with the cover in the closed position, the socket will act as a low insertion force socket which accents the package without damage to the package leads.

Claims

CLAIMS 1. A socket for an electronic package having a plurality of depending leads, comprising a base having a plurality of cavities which are open through a surface thereof, each of the cavities including a reception zone for receiving a respective lead, a plurality of contacts in the base each of which has a resilient contact arm that in a free state extends into a respective reception zone, and a cover which is mounted for transverse movement over said surface between open and closed positions, the cover having a plurality of projections, which extend into the cavities and are arranged resiliently to deflect the contact arms when the cover is in the open position, and a plurality of apertures through which the leads of the electronic package are insertable into the reception zones when the cover is in the open position, and the cover being movable to the closed position without transverse movement of the leads, such movement of the cover moving the projections and permitting the contact arms to resile into engagement with the leads, thereby electrically connecting the contacts and the leads without transverse movement of the leads.
2. A socket for an electronic package having a plurality of depending leads, comprising a base having a plurality of contacts in respective cavities, each of the cavities including a reception zone for receiving a respective lead, and each of the contacts having a resilient contact arm that in a free state extends into a respective reception zone, and a cover which is transversely movable over the base between open and closed positions, the cover having a plurality of projections which are engageable with the contact arms and are arranged resiliently to deflect the contact arms out of the reception zones when the cover is in the open position, the contact arms being permitted to resile into the reception zones when the cover is in the closed position, and the cover having a plurality of apertures which are in registration with the cavities, such that the leads are insertable through the apertures and into the reception zones without resistance from the contact arms, when the cover is in the open position, and are insertable into the reception zones against resistance from the contact arms when the cover is in the closed position.
3. The socket according to claim 1 or 2, wherein the contact arms are deflectable in the direction of movement of the cover.
4. The socket according to claim 1,2 or 3, including an actuator which is operable to move the cover between the open and closed positions.
5. The socket according to claim 3, wherein the actuator is pivotally mounted.
6. A socket constructed and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.