Abstract:
A zero insertion force (ZIF) socket for electrically connecting an electronic package and a mother board, comprises an insulative cover, a driving device, an insulative base defining a number of engaging slots therein and at least two types of engaging terminals received in the corresponding engaging slots. The engaging terminals or rows of the engaging slots are each offset relative to each other. Thus, electrical contacts are established between the engaging terminals and conductive terminals of the electronic package at different times thereby effectively lowering the operating resistance of the ZIF socket.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electrical socket for electrically connecting a electronic package and a mother board, and particularly to a zero insertion force (ZIF) electrical socket which can lower the operating resistance of the ZIF socket. 
     A conventional socket of the prior arts for electrically engaging with a electronic package having a large number of terminals should be equipped with auxiliary features for facilitating the mating process. For example, a cam lever can be introduced for simplifying opening and closing operations. In addition, engaging terminals of the ZIF socket can be configured to reduce a normal contact force between the engaging terminals of the ZIF socket and conductive contacts of a mating electronic package. However, large operating resistance is still not properly addressed by sockets of the prior art. Large contact normal peak force between engaging terminals of the electronic package and conductive terminals of a mating socket must be overcome at the onset of operation. Furthermore, unstable or inaccurate contact may result between terminals of an electronic package and a socket during assembly. 
     BRIEF SUMMARY OF THE INVENTION 
     A main object of the present invention is to provide a socket exhibiting the advantages of a low peak operating resistance and a reliable electrical connecting performance thereby ensuring mating quality. 
     In accordance with one aspect of the present invention, adjacent groups of engaging terminals received in corresponding engaging slots of a socket are arranged to be offset relative to each other. Thus, the engaging terminals of the socket contact with corresponding conductive terminals of a mating electronic package at different times thereby lowering operating resistance of the socket for moving from an inoperative position to an operative position by activating a lever from a vertical position to a horizontal position during assembly. 
     In accordance with another aspect of the present invention, rows of engaging slots receiving the corresponding engaging terminals of the socket are arranged to be offset relative to each other for electrically engaging the conductive terminals of the electronic package at different times. 
     Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is an exploded view of a socket of the present invention and an electronic package having conductive terminals arranged in arrays; 
     FIG. 2 is a partial perspective view of the socket of the present invention and engaging terminals thereof; 
     FIG. 3 is a partial cross sectional view of the socket of the present invention showing the assembly of a mating terminal with the electronic package and a mother board; 
     FIG. 4A is a cross sectional view of a first embodiment of the present invention showing three engaging terminals before engagement with the corresponding conductive terminals of the electronic package; 
     FIG. 4B is similar to FIG. 4A showing the engaging terminals engaged with the corresponding conductive terminals of the electronic package; 
     FIG. 5A is a cross sectional view of a second embodiment of the present invention showing three engaging terminals before engagement with the corresponding conductive terminals of the electronic package; 
     FIG. 5B is similar to FIG. 5A showing the engaging terminals engaged with the corresponding conductive terminals of the electronic package; 
     FIG. 6A is a cross sectional view of a third embodiment of the present invention showing three engaging terminals before engagement with the corresponding conductive terminals of the electronic package; 
     FIG. 6B is similar to FIG. 6A showing the engaging terminals engaged with the corresponding conductive terminals of the electronic package; and 
     FIG. 7 is an exploded view of the present invention and an electronic package having alternately arranged rows of conductive terminals. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, an electronic package  10  is provided with rows of conductive terminals  12 . An electrical socket  20  forms a plurality of terminal receiving passageways  24  in an insulative cover  22  thereof and a plurality of engaging slots  32  in an insulative base  30  thereof. The conductive terminals  12  are insertable through the terminal receiving passageways  24  of the cover  22  into the engaging slots  32  of the insulative base  30  and each engaging slot  32  is relevant to a corresponding terminal receiving passageway  24  inserted through by the same conductive terminal  12 . First engaging terminals  34  and second engaging terminals  341  are received in the engaging slots  32 . An L-shaped lever  26  is pivotally attached between the cover  22  and the base  30  thereby driving the cover  22  relatively sliding along a top mating surface of the base  30 , thus enabling the conductive terminals  12  of the package  10  moving in the engaging slots  32  of the socket  20 . 
     Further referring to FIG. 3, each engaging slot  32  of the base  30  has a wide opening  321  communicating with a narrow opening  322 . Each engaging terminal of the first engaging terminals  34  and the second engaging terminals  341  comprises a contact section  36  for contacting the corresponding conductive terminal  12  of the electronic package  10 , a supporting section  38  extending from the contact section  36 , a securing section  40  for interferentially fitting in the corresponding engaging slot  32  and a mating lead  42  extending from the securing section  40 , through an aperture  33  and beyond a bottom surface of the base  30  to be received in a corresponding mating slot  46  of a mother board  44 . The difference between the first engaging terminals  34  and the second engaging terminals  341  lies in the structure of the securing sections  40 ,  340 . Two limbs  48  of the securing section  40  of the first engaging terminal  34  are the same length, while two limbs  348  of the securing section  340  of the second engaging terminal  341  are different lengths. However, the total length of each securing section  40 ,  340  is the same for each engaging terminal  34 ,  341 . 
     The conductive terminals  12  of the electronic package  10  extend through the terminal receiving passageways  24  of the cover  22  into the engaging slots  32  of the base  30  thereby electrically contacting with the engaging terminals  34 ,  341 . Since the mating leads  42  of the engaging terminals  34 ,  341  are electrically connected with the mother board  44 , the terminals  12  are also electrically connected therewith. 
     A detailed description of the three embodiments of the present invention is given below. Three engaging terminals  34 ,  341  received in the corresponding engaging slots  32  are used to describe the mating process with the conductive terminals  12 . 
     Referring to FIGS. 4A and 4B, in the first embodiment, the engaging terminals  34 ,  341  are alternately disposed in the same row of the engaging slots  32 . When the conductive terminals  12  of the electronic package  10  are in inoperative positions, that is, being received in the wide openings  321  of the corresponding engaging slots  32  of the base  30 , electrical contact is not yet established with the engaging terminals  34 ,  341 . Please refer to FIG. 4A, particularly, the contact sections  36  of the first and the second engaging terminals  34 ,  341  respectively have a first contact point A 1  and a first contact point B 1  that contact foremost corresponding conductive terminals  12  of the electrical package  10 . In the inoperative positions, the first points A 1 , B 1  of the contact sections of the first engaging terminals  34  are offset respectively a first distance f 1  and a second distance f 2  from the same row of conductive terminals  12  of the electrical package  10  in a first sliding direction (shown by large arrows in FIGS. 4A,  5 A &amp;  6 A) defined by relative movement between the base  30  and the cover  22 . The second distance J 2  is greater than the first distance f 1 . It is well know in the ZIF Socket field that each conductive terminal  12  of the electrical package  10  is relevant to the engaging slot  24  of the cover  22  in which the conductive terminal  12  is received. Thus, the first and the second engaging terminals  34 ,  341  are disposed in the engaging slots  24  in such a manner that the first contact points A 1 , B 1  of the contact sections of the first and the second engaging terminals  34 ,  341  are respectively offset the distances f 1 , f 2  relative to center lines of the engaging slots  24  relevant to the engaging slots  32  in which the first and the second engaging terminals  34 ,  341  are received. Similar features are shown in FIGS. 5A &amp; 6A and symbols f 3 ˜f 6  are used to facilitate understanding of such features. When the lever  26  is activated from a vertical position to a horizontal position to drive the cover  22  sliding along a top surface of the base  30  in the first sliding direction, the conductive terminals  12  are displaced from the wide openings  321  of the engaging slots  32  to the narrow openings  322  of the engaging slots  32  thereby contacting the corresponding contact sections  36  of one of the engaging terminals  34 ,  341 . The supporting sections  38  of the engaging terminals  34  are thus deformed toward a wall of the corresponding mating slots  32 . The conductive terminals  12  firmly abut against a middle or end portion of the contact sections  36  thereby being distanced from the wide opening  321  of the mating slots  32 , that is to say, the socket  20  is in an operative position. Therefore, electrical contacts between the conductive terminals  12  of the electronic package  10  and the engaging terminals  34 ,  341  occurs at different times by alternately arranging the first engaging terminals  34  to be offset relative to the second engaging terminals  341  in the corresponding engaging slots  32  along the first sliding direction. Thus, the operating resistance of the socket  20  is effectively dispersed by creating intervals of contact during the mating process. 
     As best seen in FIGS. 4A &amp; 4B, the conductive terminals  12  of the electronic package  10  are disposed in rows and the conductive terminals in a same row are not offset relative to each other in the first sliding direction (shown by large arrow). The rows of engaging slots  32  are arranged in the first sliding direction and each row extends in a second direction being generally perpendicular to said first sliding direction. The engaging slots in a same row are not offset relative to each other in said first sliding direction. The first engaging terminals  34  and the second engaging terminals  341  are alternately disposed in the rows of engaging slots  32  in said second direction. The contact sections  36  of the first and second engaging terminals  34 ,  341  in a same row of engaging slots are offset from each other in said first sliding direction. 
     As shown in FIGS. 5A and 5B, adjacent rows of the engaging slots  32  are offset relative to each other along a first sliding direction as indicated by a large arrow. In this embodiment, the structures of the engaging terminals  34 ,  341  are identical, unlike in the first embodiment. When the conductive terminals  12  of the electronic package  10  are received in the wide openings  321  of the corresponding engaging slots  32  of the base  30 , electrical contact is not yet established with the engaging terminals  34 ,  341 . When the lever  26  is activated from a vertical position to a horizontal position to drive the cover  22  sliding along a top surface of the base  30  in the first sliding direction, the conductive terminals  12  are displaced from the wide openings  321  of the engaging slots  32  to the narrow openings  322  of the engaging slots  32 , thereby contacting the corresponding contact sections  36  of the engaging terminals  34 ,  341 . The supporting sections  38  of the engaging terminals  34 ,  341  are thus deformed toward a wall of the corresponding mating slot  32 . The conductive terminals  12  firmly abut against a middle or end portion of the contact sections  36  thereby being distanced from the wide opening  321  of the mating slots  32 . Therefore, electrical contacts between the conductive terminals  12  and the engaging terminals  34 ,  341  occurs at different times by alternately arranging adjacent rows of engaging slots  32  to be offset relative to each other along the first sliding direction of the relative sliding movement of the insulative cover  22  along the insulative base  30 . 
     Referring to FIGS. 6A and 6B, in the third embodiment, the first engaging terminals  34  are offset relative to the second engaging terminals  341  as described in the first embodiment and adjacent rows of engaging slots  32  are offset relative to each other, both along a first sliding direction as indicated by a large arrow. As described in the second embodiment. In this embodiment, the mating process is similar to the mating process of the other two embodiments, hereon do not repeat it again. 
     In addition, the engaging terminals can consist of more than two different types. The position of each type of engaging terminal can be offset relative to the position of a different adjacent type of engaging terminal thereby providing sequential electrical contact between the conductive terminals  12  of the electronic package  10  and the engaging terminals of the same type thereby effectively dispersing the peak operative resistance of the socket  20 . 
     Furthermore, if conductive terminals  52  of an electronic package  50  are aligned, as shown in FIG. 7, then the same measures described in the disclosed embodiments can be used to create intervals during the assembly process of a socket  60  and the electronic package  50  thereby dispersing and reducing the operating resistance of the socket  60 . 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.