Socket for positioning and installing an integrated circuit chip on a flexible connector sheet

A socket for positioning and installing an integrated circuit chip having terminals on one side thereof on a conductive elastomer includes a base which positions the chip over the elastomer. A camming member is moveable relative to the base between an open position disengaged from the chip and allowing the chip to be installed in the socket to a closed position in which the actuating member engages a side of the chip and exerts a force on the chip to embed the terminals in the elastomer to thereby provide an electrical connection between the terminals and the elastomer.

This invention relates to a socket for positioning and installing an 
integrated circuit chip on a test board having a flexible connector sheet 
making electrical contact between the terminals on the integrated circuit 
chip and the test board. 
Integrated circuit chips have become increasingly small in recent years, 
and may be small as 50 mm.sup.2 or less and require terminals for 
effecting electrical connections with the chip that are extremely thin. 
One way of providing terminals at the required density is the so called 
ball grid array, or "BGA" terminals in which semi-spherical projections of 
alloy are provided in an array on one side of the integrated circuit chip. 
After manufacture, these chips must be tested to assure that they are not 
defective. This is accomplished by temporarily connecting the terminals of 
the chip to a test circuit board to permit testing to take place. The 
extremely dense terminal arrays necessary on state of the art integrated 
circuits make it difficult to effect connection of the terminal with the 
circuit test board in a way in which the same test board may be used 
repeatedly to test multiple chips. However, a flexible connector sheet, 
such as that shown in U.S. Pat. No. 5,500,280 (Yamazaki et al.) has 
recently become available. The flexible connector sheet comprises a sheet 
of a flexible elastomer in which multiple wire segments are embedded. 
Accordingly, a segment of the flexible elastomer connection sheet is 
mounted on a printed circuit board and the appropriate wire segments are 
connected to the conductors in the circuit board. The elastomer is 
reasonably flexible so that when a chip having a terminal array is pressed 
upon the connector sheet, the sheet deflects to enable the terminal balls 
of the array to make proper electrical contact with the wire segments. 
When a chip has been tested and removed from the connector sheet, the 
resiliency of the elastomer returns the connector sheet to its original 
state. The chip must installed in the proper position, and a reasonable 
force must be applied to the chip to push the terminals of the terminal 
array into the elastomer. 
The present invention provides a test socket for positioning and installing 
an integrated circuit chip over a flexible connector sheet, and then 
installing the circuit on the connector sheet in the correct position, 
while assuring that the correct amount of force is exerted on the chip to 
properly embed the terminals in the elastomer, so that the terminals make 
proper electric contact with the appropriate wire segments. The socket 
includes a pair of levers with attached pressure pads that translate and 
rotate from an open position to a closed position in which the pressure 
pads, that are carried by the levers, engage the surface of the chip 
opposite the side bearing the terminal array.

Referring now to the drawings, a socket generally indicated by the numeral 
10 is used to embed the terminals 14 of a ball grid terminal array (BGA) 
which is provided on one side 16 of the integrated circuit chip generally 
indicated by the numeral 18, into a connector sheet generally indicated by 
the numeral 20. The connector sheet 20 consists of a relatively soft 
elastomer in which parallel wire segments 22 are embedded at discrete 
intervals. The wire segments 22 extend between the top and bottom surfaces 
of the connecting sheet 20 at an angle as more fully described in the 
aforementioned U.S. Pat. No. 5,500,280. The connecting sheet 20 is mounted 
on a convention printed circuit (PC) board 24 and some or all of the wire 
segments 22 make contact with corresponding conductors of the PC board 24. 
Accordingly, an electrical connection between the integrated circuit chip 
18 and the appropriate test equipment (not shown)is provided. The 
integrated circuit chip 18 has a surface 26 opposite the surface 16. The 
surface 26 is engaged, as will be hereinafter be described, by components 
of the socket 10 to install the integrated circuit chip 18 on the 
connector sheet 20 with the terminals 14 embedded in the sheet 20 in 
electrical contact at the appropriate wires 22. 
The socket 10 includes a lower base plate generally indicated by the 
numeral 30 and an upper base plate generally indicated by the numeral 32. 
Lower base plate 30 defines a recess 34 which receives the connecting 
sheet 20, and also defines cavity 36 immediately above recess 34 which 
receives the integrated circuit chip 18. Projecting members 38, 39 project 
inwardly from the sides of the cavity 36 to engage the edges the chip 18 
to precisely position the chip 18 with respect to the connecting sheet 20 
when the latter is received in the recess 34. Lower base plate 30 further 
includes columns 40 at each corner thereof which define bores 42 
therewithin. Each of the bores 42 receive a coiled spring 44. Opposite 
sides of the lower base plate 30 define raised columns 45 from which 
locating projections 46 extends. Columns 45 define half moons 48 and 
shoulders 50 at the lower edge of the columns 45. Columns 45 are connected 
to their adjacent columns 40 by walls defining outer sliding surfaces 52 
and upper surfaces 54. The upper surfaces 54 are stepped down from the top 
of columns 45. 
The lower base plate 30 and upper base plate 32 slidably support a camming 
member generally indicated by the numeral 56. Camming member 56 includes 
opposite walls 58 both of which include recessed portions 60 into which 
the columns 45 project. Shoulder 61 projects into the recesses 60 adjacent 
the lower end thereof. Walls 58 further include inner sliding surfaces 66 
which slide against corresponding sliding surfaces 52. Angled camming 
slots 68 are provided in each of the surfaces 66. The walls 58 are 
interconnected by side walls 70. A recess 72 is defined in each of the 
side walls 70 and a control surface 74 defines the lower edge of each of 
the recesses 72. The control surface 74 will be described in detail 
hereinafter. The juncture of the corners between the walls 58 and 70 are 
provided with bores 76 which receive the ends of the springs 44 opposite 
the end received in the bores 42. The ends of the bores 76 define stop 
surfaces 77 (FIGS. 1 and 4) which engage corresponding stop surfaces 79 on 
columns 40 to stop downward movement of the camming member 58 when the 
camming member 58 is moved into the fully lowered position. Accordingly, 
the springs 44 yieldably urge the camming member 56 away from the lower 
base plate 30. The upper base plate 32 include opposite walls 78 from 
which apertured tabs 80 project. Apertured tabs 80 define apertures 82, 
which receive fasteners 84. The fasteners 84 are used to secure the socket 
10 to the PC board 24. A shoulder 81 (FIGS. 2 and 7) is defined on the 
lower ends of the tabs 80 and are engaged by shoulders 61 on camming 
member 58 to act as a stop for camming member 58 when springs 44 urge the 
camming member 58 to the uppermost position. 
Legs 86 extends downwardly from the tabs 80 and terminate in barbs 88 which 
are adapted to engage shoulders 50 when the socket is assembled. The walls 
78 include undercuts 90 on the lower edges thereof which cooperates with 
the surfaces 54 to define slots 92 when the upper base plate 32 is 
assembled onto the lower base plate 30. The upper base plate 32 further 
includes end walls 94 from which solid tabs 96 extend. 
Tabs 80 are received within recess portion 60 on the camming member 56 and 
the legs 86 extends through the bottom of the recessed portion 60 
substantially parallel to the columns 45 and the barbs 88 are engaged with 
the shoulders 50. Accordingly, the solid tabs 96 are received within the 
recesses 72 of the camming member 56. Accordingly, the upper base plate 32 
and lower base plate 30 cooperate to guide the camming member 56 as it 
moves toward and away from the lower base plate 30. The camming member 56 
is illustrated in FIG. 1 in its uppermost position, and is urged thereto 
by the action of the springs 44. 
A pair of levers 98 define opposite ends 100, 102. The ends 102 of each 
lever 98 define a surface 103 (FIGS. 8 and 9) which guide the chip 18 as 
it passes through the socket. A recess 104 is formed in the end 100 of 
each of the levers 98. One end of a coil spring 106 is received in the 
recess 104 of each lever 98, and the other end of the spring 106 slidably 
engages lower surface 108 of wall 94 of upper base plate 32. Ends 100 
further include a curved surface 110 that slidably and pivotally engages 
the control surface 74 of camming member 56 as the latter moves from an 
intermediate position into its uppermost position illustrated in FIG. 1. 
Pins 112 extends from opposite edges of each of the levers 98 intermediate 
the ends 100, 102 thereof. Each of the pins 112 extends through a 
corresponding slot 92 and into a corresponding one of the camming slots 68 
in the camming member 56. A detent 114 on each lever 98 acts as a stop 
wherein the springs 106 urge the detent 114 against surfaces 54 as the 
control surface 74 is moved away from the curved surface 110 on levers 98 
as the camming member 56 is moved to the lowered position. 
A pressure pad generally indicated by the numeral 116 is mounted on the 
ends 102 of the levers 98. Pressure pad 116 is adapted to engage the chip 
18 as described hereinabove. Pressure pads 116 define a crown 117 (FIGS. 
10-14) on one surface thereof and a flat surface 119 on the opposite 
surface. Pressure pads 116 further include hangers 118 that are pivotally 
received within recesses 120 to permit limited pivoting movement of the 
pad 116 with respect to the levers 98. Hangers 118 also permit movement of 
the levers 98 relative to pads 116 before pressure is applied through the 
pads 116 on the chip 18. Pads 116 further include a portion 122 that is 
designed to accommodate the projection 39 as the pressure pads are moved 
by the levers into engagement with the integrated circuit chip 18. The 
levers 98 include a recessed portion 125 to accommodate the portion 122. 
In operation, the chip 18 is installed in the socket 10 by passing the chip 
through the opening 124 in upper base plate 32. The chip then passes 
between the ends 103 (FIG. 8) of the levers 98 and into the cavity 36. 
Accordingly, as the chip 18 passes through the socket and into the cavity 
36, it passes through three different levels of alignment. The first level 
of alignment is provided by the opening 124; the second level of alignment 
is provided by the end surfaces 103 on the levers 98; and the final 
alignment is provided by the projections 38, 39. The springs 44 yieldably 
urge camming member 56 to its uppermost position illustrated in FIGS. 1-6. 
In this position, and referring to FIG. 4, the pins 112 are disposed in 
the lowermost portion of the camming slots 68. Springs 44, acting through 
camming member 56, pins 112, levers 98, slotsand 92, and pressure pads 116 
provide the necessary inserting force such that the terminals 14 are 
embedded sufficiently in the elastomeric connection sheet 20 to assure 
that the terminals 14 make proper electric contact with the wire segments 
22. The wire segments 22 are connected to an appropriate conductor (not 
shown) in the PC board 24. Accordingly, the appropriate test equipment 
(not shown) can be used to effect testing of the chip. 
After testing has been completed, the chip 26 is released by forcing the 
camming member 56 downwardly toward lower base plate 30. As the camming 
member 56 is lowered, springs 106 pivot the levers 98 about the pins 112 
and about surfaces 110. Accordingly, the camming slots 68 force the pins 
112 to move along the surfaces 54 toward the corresponding edges of the 
socket, thereby spreading the levers 98 away from each other. As the 
camming member 56 is moved downwardly, springs 106 maintain the surfaces 
110 in sliding and pivoting engagement with the surfaces 74 until the 
camming member 56 is moved downwardly to an intermediate position between 
the fully raised position illustrated in FIG. 6 and the fully lowered 
position illustrated in FIG. 9. When this occurs, the detent or stop 114 
on the levers 98 adjacent the pins 112 are urged into engagement with the 
sliding surface 54 by the springs 106, thereby preventing further 
downwardly pivoting movement of the levers 98 as the camming member 56 is 
lowered between the intermediate position and the fully lowered position 
illustrated in FIG. 9. As can be seen in FIG. 9, as the camming member 56 
moves between the intermediate and the fully lowered position, the camming 
slots 68 continue to slide the levers 98 and their pins 112 along and 
relative to the sliding surface 54. As this occurs, the springs 106 also 
slide along the surfaces 108 until they attain the position illustrated in 
FIG. 9. When the camming member 56 is in its fully lowered position 
against the bias of springs 44 and the levers have been spread apart, the 
chip 16 can be extracted through the opening 124 in the upper base plate 
member 32, by any appropriate means, such as by vacuum extraction. 
Referring now to FIGS. 10-14, which are schematic illustrations of the 
manner in which the levers 98 move the pressure pads 116 between the fully 
open position illustrated in FIGS. 9 and 10 and the fully closed position 
illustrated in FIGS. 6 and 14, FIG. 10 illustrates the various components 
of the socket 10 in a position in which they are disposed in when the 
camming member 56 is fully pressed against the force of the springs 44, 
and the levers are in the FIG. 9 position. The chip 18 has been inserted 
over the connecting sheet 20 by inserting the chip 18 through the opening 
124 in upper base plate 32. 
FIG. 11 illustrates the various components in the position which they 
assume when the camming member 56 is moved to the intermediate position, 
in which the control surface 74 engages the surface 110. In this position, 
the camming member 56 has been raised to a position in which the pins 112 
have moved down the tapering portion of the camming slot 68, such that the 
pressure pads 116 are disposed over the chip 18. The pressure pads 116 are 
adapted to engage the projections 38 on the edge of the cavity 36. The 
projection 38 cooperates with a projection 126 adjacent thereto to guide 
the pad 116 in its proper orientation so that it properly engages the chip 
18. As discussed above, the limited pivoting motion between the pad 116 
and the lever 98 allows the pad 116 freedom to be guided by the projection 
38 and 126. The projections 38 and 126 guide the pressure pad 116 to 
assure that the flat surface 119 will engage the chip 18 over the entire 
surface 119. The chip 18 is fragile, and point or line stresses on the 
chip 18 must be avoided. Because a clearance exists between the crown 117 
and the lever 98, pivotal motion of the pad 116 is accommodated so that it 
may be guided by the projections 38 and 126. In FIG. 12, pressure pad 116 
has just engaged the upper surface 26 of the chip 18 as the pivot pins 112 
have just entered the vertical portion of the 128 of the slot 68. In FIGS. 
13 and 14, the pressure pads 116 install the chip on the connector sheet 
such that the terminals are embedded in the connector sheet to their 
proper depth. Accordingly, surface 119 of pressure pad 116 has engaged the 
chip 18 and the clearance between the crown 117 and the lever 98 has been 
taken up, so that pressure may be applied to the chip 18 by the lever 98 
through the pressure pad 116. In FIG. 14, the fully engaged position, the 
pressure is being fully applied to the chip 18 through the pressure pad 
116. Accordingly, the terminals will be embedded in the connecting sheets 
20 to the proper depth to assure good electrical contact with the wire 
segments.