EP0113733A1 - Zif test socket for pin grid array packages - Google Patents

Abstract

Base (74) having a base member (10) in which contact elements (12) are mounted and from which first and second normally closed arms (78, 80) extend upwardly from each element ( 12), as well as a cover (14) positioned in a sliding manner on the base member (10) and having inside a member (66) so that when the cover (14) slides, the arms (78) , 80) are separated so that pins (24) on a pin gate array package (22) can be freely inserted therein. The arms (78, 80) close automatically upon releasing the cover (14).

Description

ZIF TEST SOCKET FOR PIN GRID ARRAY PACKAGES There is described in U.S. Patent 3,763,459 a zero or low insertion force socket with which integrated circuits and electronic components in devices such as dual-in-line packages (DIPs) can be easily inserted, tested and evaluated, and thereafter easily withdrawn. This type of device is. known as a high cycle or test socket as opposed to a connector, mounted on a circuit board in, for example, a computer, and into which a DIP has. been inserted to remain there for an extended length of time.

The socket disclosed in the aforementioned patent is comprised of. a housing of three stacked members. The middle member moves back and forth between the upper and lower members that are fastened together. U-shaped contact elements are positioned in the socket with the two "arms" extending up through aligned openings in the middle and upper members. The contact arms are in the open position; i.e., spaced apart, in the relaxed position. The openings through which the contact arms extend have concave surfaces so. that upon moving the middle member axially, the contact arms are brought into engagement with DIP leads positioned thereinbetween and are wrapped around them partially by the concave surfaces to effect a good electrical contact.

A second embodiment is a socket adapted to engage pins or leads depending from a multi-pin type package. The socket is formed from three members stacked one on top of the other. The underside of the top member has a slot in which two sliding cam plates are positioned. Openings in the top member and plates are in aligned relationship. A cam rotatably positioned in the socket slides the cam plates in opposite directions simultaneously. Contact elements are positioned in the socket with L-shaped upper ends extending up through the openings in the sliding plates. Each aligned openings receives two separate contacts. Upon inserting the pins into the openings and between the two L-shaped upper ends of the contact elements/ the rotation of the cam causes the opening walls to pivot the contact ends about the pins and into a pressure relation therewith for effective electrical termination.

The present invention is intended to provide a socket of the above kind which is substantially simplified in that the housing is formed from two members and the contact elements, having two vertical arms, are normally closed. Further, the socket is designed to receive grid array packages, or GAP for short.

A socket as defined above is, according to the present invention, characterized in having a two piece housing, one being a lower or base member, and the other being the upper member or cover. Contact elements, having first and second upwardly extending arms, are positioned in vertical cavities in the base member with the second arm extending above the top surface thereof and into a slot in the overlying cover adjacent pin-receiving openings therein. The arms are normally closed; i.e., biased against one another. By pulling the cover across the top surface of the base member, the second arm is pulled away from the first arm so that a grid array pin may be freely inserted therein between. Upon releasing the cover, the second arm moves back towards the first arm and thereby places the intervening pin in a compressive grip to establish electrical contact therewith. A cam or lever, housed in cooperating structures on the base member and cover, facilitates the operation described above so that GAPs and the like may be tested quickly and reliably. For a better understanding of the invention, reference will now be made by way of example to the accompanying drawings, in which:

Figure 1 is an isometric drawing illustrating in exploded fashion the socket constructed in accordance with the present invention: a GAP is also shown along with a printed circuit board;

Figure 2 is an isometric drawing illustrating the socket of Figure 1 as assembled, mounted on the circuit board and with the GAP inserted therein;

Figure 3 is an isometric view of the contact element constructed in accordance with the present invention;

Figure 4 is a view taken along line 4-4 in Figure 3 looking down into the contact element;

Figure 5 is a vievr of the contact element of Figure 3 after being blanked or stamped out but prior to being formed; Figure 6 is an isometric drawing of a cavity cut down the middle and spread open to show clearly the interior structure;

Figure 7 is a top plan view looking down into the cavity of Figure 6; Figures 8A and 8B, the latter being taken along line

8B-8B in the former, are views showing a contact element in the housing and in its normally closed position; and

Figures 9A and 9B, the latter being taken along lines

9B-9B in the former, are views showing a contact element in the housing and in the open position with a grid array pin inserted between the open arms.

Figure 1 shows the components of the socket of the present invention in exploded fashion. These components are base member 10, contact elements 12, cover 14 and lever 16. Roll pins 18 are utilized to attach cover 14 to the base member. A printed circuit board 20 on which base member 10 is mounted, is shown below. GAP 22 is shown above with pins 24.depending therefrom.

Base member 10, preferrably molded from a plastic sold by ICI, Americas, Inc. under the trademark VICTREX.

A plurality of cavities 26 extend vertically through the base member, opening out onto top surface 28 and under surface 30. End 32 of member 10 is recessed to provide shelf 34 and further is notched as indicated by reference numeral 36. Apertures 38 are provided in. the face of the notch.

Vertical holes 40 may be provided on the shelf so that base member 10 can be bolted to board 20.

Opposite end 42 of member 10 is notched as indicated by reference numeral 44. Apertures 38 are also provided in this notch.

Contact elements 12 are described in detail below. Generally speaking, each element has a pair of upwardly extending arms biased together and a lead or pin depending from one arm. The elements are positioned substantially in base member 10 with the leads or pins depending therefrom for insertion into board 20. One arm extends above top surface 28 and into an opening in the cover so that upon moving the cover across the top surface of member 10, that arm is pulled away from the other and a pin from a GAP can be freely inserted therein between.

Cover 14 is attached to base member 10 so that it can be moved across upper surface 28. Depending rails 46 on ends 48 and 50 of the cover are received in notches 36 and 44 on base member 10. Roll pins 18 are located in holes 52 in. the rails and apertures 38 in the base member to hold the cover thereon. The cover can move back and forth between ends 32 and 42 on the base member.

Vertical slot 54 is located in the cover at end 48 between rail 46 and one side. The cut-out between the rail and slot provides access to a bolt holding base member 10 to the board. A plurality of vertical openings 56 extend through cover 14 on the same spacing as cavities 26 in base member 10. The entrances to the openings on top surface 58 of the cover may be beveled as shown, Further, each entrance is discrete; i.e., separated from its neighbor on all sides. The openings and the opening outlets 60 on underside 62 of the cover are separated on the sides by vertical walls 64. Each opening is defined by an increase in the dimension between walls which provides forwardly facing vertical shoulders 66 and rearwardly facing vertical shoulders 68, both seen more clearly in Figures 8B and 9B. There are no separating walls between openings longitudinal Cover 14 is preferably molded from the same material as base member 10.

Lever 16 is an L-shaped device consisting of a loop handle 70 and arm 72. It must be made from a rigid material such as steel. Figure 2 is a view showing an assembled pin grid array test socket 74 mounted on circuit board 20 and into which GAP 22 has been inserted. In the assembled socket, arm 72 of lever 16 lies on shelf 34 of base member 10 and extends through a downwardly open groove (not shown) in the cover behind the facing surface of end 48 with the lever in the position shown in solid lines; i.e., pivoted down, the socket or more specifically, the contact elements are closed. This is the condition shown in Figures 8A and 8B. Upon pivoting lever 16 downwardly to the position shown by dashed lines, cover 14 moves forward as indicated by the dashed-line arrow 76. The arms of the contact elements are drawn apart and pins 24 on GAP 22 may be freely inserted or withdrawn. This is the Figures 9A and 9B condition. Moving the lever back up allows the cover to move back to its normally closed position under the force of the contact elements arms returning to their normally closed position.

A contact element 12 is shown isometrically in Figure 3. The upper section of the element consists of upwardly extending first and second arms 78 and 80 respectively and connecting strap 82. An upper ear 84 projects out from one side of the first arm adjacent the arm's upper or free end 86. A beveled lead-in surface 88 may be provided on the free end of the first arm 78 as shown. Connecting strap 82 extends between and spaces the two arms apart at their lower ends as well as joining them together. The second arm 80 attachment to strap 82 is also a hinge line and is indicated by reference numeral 90. From hinge line 90 upwardly, the second arm converges towards first arm 78. A concavo-convex contact pad 92 defines the upper or free end of the second arm, and in the normal non-stressed position, the convex surface 94 of the pad bears against or is immediately adjacent the free end 86 of the first arm.

The lower section of a contact element 12, being a continuation of first arm 78, includes a retaining portion 96 and lead 98 of substantially reduced width. A laterally extending lower ear 100 is located on portion 96. The lead is adapted for insertion into a plated through hole in board 20. Figure 4 is a top plan view of element 12.

Figure 5 is a view showing a stamped or blanked-out cdhtact element 12 prior to being formed up into the Figure 3 configuration. The structural features of Figure 3 are indicated by the same reference numerals. Additionally, the drawing shows carrier strip 102 indicating that the preferred method of making the elements is by stamping and forming them on a continuous strip. The preferred material is beryllium copper.

Figure 6 is an isometric drawing of a cavity 26 which has been split apart and swung open so to speak, to reveal the interior structure clearly.

Back wall 104 includes support 106 which extends above top surface 28 of base member 10. The support does not extend across the full width of the cavity, stopping short on the left-hand side.

Vertical rails 108 and 110, located on right side wall 112 and left side wall 114 respectively, define, in cooperation with back wall 104, vertical grooves 116-R and 116-L. Both grooves terminate at upwardly facing shoulders 118-R and 118-L, located near the bottom of the cavity. The cavity continues down and out through the base member as a narrow slot 120 located between the two shoulders, 118-R and 118-L. A beveled surface 122 and upwardly facing surface 124 are in front of the slot.

Reference numeral 126 indicates the primary floor of the cavity.

A beveled surface 128 is provided on 108 and 110 leading into grooves 116. An intermediate step 130, facing upwardly, is located on rail 108 adjacent right side wall 112. Front wall 132 extends down to floor 126.

Figure 7 is a view looking down into a cavity 26 showing the several upwardly facing surfaces in greatly expanded scale.

With reference to the drawings in Figures 3, 6, 7 and 8, the positioning of a contact element 12 in a cavity 26 will now be described. The element is loaded into the cavity from above with the lower section (retaining section 96, lead 98) and first arm 78 bearing against back wall 104. Lead 98 passes through slot 120 and out from under side 30 of base member 10. The lower edge of lower ear

100 rests on upwardly facing shoulder 118-L to vertically position the element in the cavity. The lateral edges of that ear and of upper ear 84 are in groove 116-L while the right sides of first arm 78 and retaining section 96 are in groove 116-R. Accordingly, first arm 78 (and the lower section) are held firmly against back wall 104 and support 106 and cannot move away therefrom in a horizontal direction

Strap 82 is suspended in the cavity space as is second arm 80. However, there is an abutting relation between the strap and rail 108.

Beveled surfaces 122 and 128 facilitate the entry of the elements into the cavities. The space above surface 124 provides room for the slot 120 core pin and is not a critical area with regard to the contact elements. The spaces above floor 126 and step 130 provide room for second arm 80 as it is pulled away from first arm 78. With the contact elements 12 loaded in cavities 26 as described above, lever 16 is positioned and cover 14 placed on top surface 28 of base member 10. The sides of pads 92 on second arms 80 engage forwardly facing, vertical shoulders 66 in cover openings 56. This is shown in Figures 8-A and 8-B and is the normally closed condition; i.e., second arm 80 is in a non-stressed state and is adjacent or may even be touching first arm 78 at their upper free ends. Upon pivoting lever 16, cover 14 is moved forwardly, as indicated by arrow 76 in Figure 2 and arrows 134 in

Figures 9-A and 9-B. As the cover moves forward, second arms 80, caught by shoulders 66, are pulled away from first arms 78. This open position is shown in Figures 9-A and 9-B. Pins 24 on GAP 22 may be inserted in between the two arms through openings 56 without engaging either arm; i.e., zero insertion force. Thereafter, lever 16 is returned to its original position and the cover, under the influence of the energy stored in the resiliently deformed second arms 80, is moved back. Pins 24 are firmly gripped between the two arms 78 and 80 and an electrical contact there between established. The GAP may be removed without exerting any force by rotating lever 16 to move the cover forward to draw the two arms apart.

Claims

CLAIMS :

1. A zero insertion force test socket comprising a base member having a plurality of cavities extending vertically therethrough, a cover slidably positioned on top of the base member and having a plurality of vertical openings extending vertically therethrough, means to slide the cover, characterised by the cover having vertically extending shoulder means adjacent each opening and accessible from the underside, and further a plurality of contact elements having hingedly connected, upwardly extending, relatively short first and relatively long second arms in normally abutting position and a depending lead adapted for insertion into a printed circuit board, said elements positioned in the cavities with the leads extending downwardly from the base member, the first arms secured against horizontal movement and the second arms extending upwardly into the cover adjacent the vertically extending shoulder means.

2. A test socket according to claim 1 characterised by the lead on the contact elements being attached to and extending down from the first arm.

3. The test socket according to claim 2 characterised by the first and second arms being connected by a strap attached to a side of each arm.

4. The test socket according to claim 3 characterised by the free end of the second arm being a concavo-convex shape with the convex surface facing the first arm.

5. The test socket according to claim 4 characterised by the first arm including a laterally extending ear and the cavity including a groove for receiving the ear so that the first arm is restrained from horizontal movement.