Z I F SOCKET FOR CH I P CARRIERS This invention relates, generally , to chip carrier sockets and , more particularly , to a chip carrier socket housing which facilitates zero insertion force for a chip carrier. With the increased usage of chip carriers and chip carrier sockets , there has been an increasing demand to use tin-plated contacts or other suitable metals rather than traditional gold plating , thereby lowering the overall cost. Coupled with the usage of tin or non-gold platings is the requirement for increased contact forces. When a chip carrier socket has a large number of contacts _t with each contact using tin, significant chip carrier insertion forces must be utilized . Also, problematic is the need for the chip carrier to be inserted in a uniform manner so as to prevent it from being cocked in an inserted position . Accordingly-, it is desirable to have a chip carrier housing which allows for zero insertion force for chip carriers. Further, it would be advantageous tσ have a device which allows for easy removal of a chip carrier from a chip carrier socket while still providing a low profil and not occupying significantly larger board space. Accordingly , the present invention teaches and as an object of the present invention a ZI F socket for chip carriers , comprising a chip carrier having conductive pads or areas, thereon , chip carrier contacts for providing electrical communication from the conductive pads or areas through the contacts , and a chip carrier socket housing having the chip carrier contacts disposed therein and being profiled to receive the chip carrier therein , characterized in that the walls of the housing are inwardly compressible towards the chip carrier so as to urge the chip carrier contacts into engagement with the conductive pads or areas contained on the chip carrier.

Reference is now made to the description of the preferred embodiment illustrated in the accompanying drawings in which:

FIGURE 1 is an exploded isometric view of the apparatus of the present invention;

FICU RE 2 is a cross-sectional view prior to chip carrier insertion;

FIGU RE 3 is a cross-sectional view showing the assembled invention; and FIGURE 4 is a crσss-sectroπai view taken through a portion of Figure 1 .

Referring now to the drawings and in particular to Figure 1 , there is shown an exploded isometric view of the present invention. Shown is a plastic retainer or lid 10 which cooperates with a chip carrier socket housing shown generally at 12 to retain the chip carrier 1 . in the cfiip carrier socket housing 12. Contacts shown generally at 16 reside in the housing and make electrical contact with conductive strips 34* which are contained on the printed circuit board 18. The contacts 16 in the preferred embodiment of the present invention are those described in U . S . Patent Application given Serial No . 584 ,274 entitled " Contact for Chip Carriers and Method of Inserting Same into a Housing" , filed February 27, 1984, and which is incorporated by reference herein . The retainer or lid 10 has a retainer latch mechanism 20 disposed on the outside and which is shown more clearly in Figures 2 and 1. The chip carrier 14 has conductive pads or areas at 22 disposed thereon which engage portions of the contacts 16 (shown more clearly in Figures 2 and 3 ) . The chip carrier socket housing 1 2 is preferably made from plastic and is comprised of movable socket walls 24 which are separated by slits 30 which are disposed adjacent each of the housing corners or corner portions 28. The movable socket walls 24 have contact spacing barriers 32 disposed on the inside thereof for separating , aligning and retaining each of the contacts 16. Disposed on the floor of the chip carrier socket housing 12 is an X-shaped standoff which provides some rigidity to the entire housing structure 12 as well as vertically spacing the chip carrier 14 in the housing 1 2. Tabs 26 are disposed along the exterior portions of the movable socket walls 24 and resiliently engage the retainer latches 20 (shown more clearly in

Figures 2 and 3) . Channels 51 are disposed alongside each of the movable walls 24 and extend through the bottom or base 13 of the socket housing 1 2. This thereby allows the movable walls 24 to pivot about the movable wall pivot portions 52 disposed adjacent each of the slits 30 and at each end of the movable socket walls 24- since the movable wall pivot portions 52 are the only means of interconnecting the housing corners 28 with the movable socket walls 24.

Referring now to Figure 2 , there is shown a cross-sectional view taken through a portion of the present invention prior to full assembly of the entire device. Here it can be seen how the printed circuit board 18 having conductive strips 34 thereon electrically interconnects with the contact shown generally at 16. Also visible is the channel 51 which allows the movable socket walls 24- to pivot inward. The movable socket wall 24 has a contact retaining member 44 disposed therein which aids in resiliently holding the contact 16. The contact 16 has a knee portion 46 which engages the upper portion of the chip carrier conductive pads 22 as well as a contact pivot arm 48 and a front beam pivot elbow 50. The tabs 26 perform a cam-like function (as shown- ore clearly in Figure 3) and have- a- housing. -latching* or engaging portion 42 which cooperates with the retainer latching or engaging portion 40 contained on the retainer inclined plane portion 38. The retainer or lid 10 is comprised of a retainer top portion 35 , a retainer sidewall 36 , and the retainer inclined plane portion and retainer latching or engaging portion 38 , 40 respectively , as previously mentioned .

Referring now to Figure 3 , there is shown a view similar to that of Figure 2 with the device of the present invention completely assembled . During this assembly process , the chip carrier 14 is placed into the chip carrier socket housing 12 between the contacts 16. Thereafter , the retainer or lid 10 is placed over the chip carrier socket housing 12 and the chip carrier 14 and is urged downwards such that the retainer latching or engaging portion 40 begins to slide along the inclined

surface of the tab 26. Thereafter , in a cam-like motion , the movable socket walls 24 are urged inwards toward the chip carrier 14 with the movable socket walls 24 pivoting about the movable wall pivot portions 52. As the knee portion 46 of the 5 contact 16 engages the conductive pads 22 ₁ the. contact pivot arm 48 and the front beam pivot elbow 50 of the contact 16 begin to flex while the rear beam portion 49 of the contact 16 also flexes as can be readily seen by comparing the movement of the rear beam portion 48 between Figures 2 and 3. Upon full seating of

10 the retainer or lid 10 , the housing latching or engaging portion 42 fully engages the retainer latching or engaging portion 40 which thereby resiliently holds the lid 10 onto the housing 12. This , therefore, causes the chip carrier 14 to be fully seated and rigidly held in the chip carrier socket housing 12 while

15 providing proper flexure of the contacts 16 such that a contact mating force is accomplished between the conductive pads 22 of the chip carrier 14 and the knee portion 46 of the contact 16. Therefore the contact mating force is not vertically downward as is normally utilized by standard chip carrier sockets and covers

20 or lids , but is almost horizontal and normal to the contact mating area. The removal of the chip carrier 14 from the housing 12 is relatively simple and only requires removal of the retainer or lid 10. This is preferably performed through the use of a screwdriver or other similar article being placed in between the

25 outer portion of the movable socket walls 24 and the retainer incl ined plane portion 38 , with the screwdriver being rotated slightly so as to disengage the retainer latching or engaging portion 40 from the housing latching or engaging portion 42. An alternate means of retainer or lid 10 removal may be accomplished

30 a number of ways which are readily obvious to one skilled in the art such as through the use of a lid removal handle 54 which would be disposed on each side of lid 10. Thereafter , urging of the handles 54 towards each other has a tendency to urge, in a pivoting motion , the retainer sidewall 36 outward thereby

35 releasing the lid 10 from the housing 12.

Referring now to Figure 4 , there is shown a cross-sectional view taken through a portion of Figure 1 showing the housing 1 2 prior to placement of the retainer or lid 10 as well as after placement of the retainer or lid 10 (shown in phantom) . Here it can be readily seen how the movable wall pivot portion 52 allows the movable socket wall 24 to be pivoted inward .

It is to be remembered that many variations of the present invention may be practiced without departing from the spirit and scope of the present invention . These variations may include use of circuit boards other than printed circuit boards while plated-through holes exclusive of conductive strips may also be utilized . Further , other types of contacts may be used while different types of conductive pads on the chip carrier, such as leads , may be utilized. Further , the standoffs utilized may be eliminated or the configuration may ^* be changed while the number of tabs may be varied or utilize a different type of configuration with corresponding modifications to the retainer or lid. Additionally , the slits in the movable socket walls or the channels in the bottom of the housing may be eliminated with the use of weakened portions being used which would facilitate the pivoting motion of the movable socket walls . Additionally ,, materials other than plastic may be utilized for the socket housing or the lid .

Accordingly , the present invention teaches a device which is very inexpensive to manufacture, easy to utilize , accomplishes easy replacement as well as facilitating automatic insertion methods . Additionally , tight space requirements and high contact mating forces are also practiced .