# Patent

## Title
Adjustable test socket

## Abstract

An adjustable test socket for aligning an electronic device with spring probes in a test fixture is provided having two adjustable walls or four adjustable walls.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of co-pending provisional application Ser. No. 60/780,448, filed Mar. 8, 2006, entitled ADJUSTABLE TEST SOCKET.


FIELD OF THE INVENTION
The present invention relates to test socket assemblies and, more particularly, to test socket assemblies for temporarily connecting the conductive pads of an electronic device to an electronic test fixture during a test and evaluation procedure.
BACKGROUND OF THE INVENTION
Test sockets for the semi-conductor industry revolve around being able to guarantee contact between the spring probes in the test socket and the device pad/ball. It has become increasingly difficult to guarantee contact because of the variance in the package size of a chip and the variance of the pitch between the pads on the chip, along with the increased density of pads. A variety of errors may be reported for a tested device due to one or more probes contacting the wrong pad(s), contacting the edge of a pad resulting in poor contact between a test probe and pad, or a test probe simply missing the target pad all together. As a result, perfectly good devices may be rejected as defective driving up the cost of manufacturing or the end product.
SUMMARY OF THE INVENTION
A two- and four-wall adjustable test socket compensates for device tolerances to increase the ability to guarantee contact between the spring probes of the test fixture and the device pads. The two-wall adjustable test socket effectively cuts the outside device tolerance in half by presenting a device pocket which has a fixed corner dimensional to a particular device's nominal size, and two adjustable side walls to control the X dimension and Y dimension of the pocket.
The four-wall adjustable test socket presents a device which has four adjustable device pocket walls. The walls move in and out together to center the device within the device pocket and thereby compensate for device variances.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a two-wall adjustable test socket.
FIG. 2 is an enlarged partial sectional view of an adjustable wall member of FIG. 1 along line 2-2.
FIG. 3 is an enlarged perspective view of an adjustable wall member of FIG. 1.
FIG. 4 is an enlarged sectional view of a test fixture with the two-wall adjustable test socket of FIG. 2.
FIG. 5 is another embodiment of the two-wall adjustable test socket.
FIG. 6 is an enlarged partial sectional view of an adjustable wall member of FIG. 5 along line 6-6.
FIG. 7 is an enlarged perspective view of an adjustable wall member of FIG. 5.
FIG. 8 is an enlarged sectional view of a test texture with the two-wall adjustable test socket of FIG. 6.
FIG. 9 is a top plan view of a four-wall adjustable test socket.
FIG. 10 is a bottom plan view of the four-wall adjustable test socket of FIG. 7.
FIG. 11 is an enlarged perspective view of the wall members and adjusting cam.



DETAILED DESCRIPTION
Referring initially to FIGS. 1-4 a two-wall adjustable test socket of the present invention is generally indicated by reference numeral 20. The two-wall adjustable test socket 20 includes a mounting plate 22 which is secured to a test fixture plate 24 by fasteners 26 in each corner of the mounting plate 22. The mounting plate 22 includes a device pocket 28 formed by two fixed sides 30 and 32 each having a beveled surface 31 and 33, respectively, to present a fixed corner 34, and two adjustable wall members 36 and 38 which present device pocket walls 40 and 42, respectively. Extending through the bottom of the test fixture plate 24 aligned with the device pocket 28 are arrays of spring probes 44 which are positioned to be aligned with the device pads (not shown).
The adjustable wall members 36 and 38 are identical and will be described in detail referring to adjustable wall member 36. Adjustable wall member 36 includes a base 46 which has an aperture 48 for a fastener 50 for securing the adjustable wall member 36 to the mounting plate 22, a pair of compliant members 52 and 54 extending from base 46, and a nose 56 which includes a beveled surface 58 and the device pocket wall 40. The nose 56 is separated from the base 46 by a gap 57 which allows the adjustable wall member 36 to automatically adjust for varying device sizes. The adjustable wall member 36 also includes a rail or guide ridge 60 and 62 on the lower surface of the base 46 and nose 56, respectively, which fits into an alignment groove 62 in mounting plate 22.
The adjustable wall members 36 and 38 are adjusted to the optimal location according to the dimensions of a particular device under test and then secured in place by tightening the fasteners 50. In operation, the text fixture 70 presses an electronic device (not shown) into the device pocket 28 of the adjustable test socket 20. The beveled surfaces 31, 33 and 58 of the pocket sides 30, 32, 40 and 42 guide the electronic device into the device pocket 28 and into alignment with the spring probes 44. The compliant members 52 and 54 ensure that the electronic device is urged into the fixed corner 34 of the mounting plate 22. By forcing the device into the fixed corner 34, the variances in the device package and the location of the device pads can be accurately managed to improve the likelihood of contact between the device and the spring probes 44 of the test fixture 70.
Referring to FIGS. 5-8, another embodiment of a two-wall adjustable test socket is generally indicated by reference numeral 20. The two-wall adjustable test socket 20 includes basically the same components as set forth above for the first embodiment except for the adjustable wall members 80 and 82, which are discussed below in detail.
The adjustable wall members 80 and 82 are identical and will be described in detail referring to adjustable wall member 80. Adjustable wall member 80 includes a base 84 which has an aperture 86 for a fastener 50 for securing the adjustable wall member 80 to the mounting plate 22, a pair of compliant members 88 and 90, and a nose 92 which includes a beveled surface 94 and a device pocket wall 96. Along the lower surface, a rail 98 extends from the base 84 to the nose 92 and fits into the alignment groove 62 in mounting plate 22. The aperture 86 is countersunk and includes a lateral split or channel 100. When a fastener 50 is inserted into the aperture 86 and tightened, the head of the fastener 50 forces the nose 92 away from the base 84. The adjustable wall member 80 is aligned in the groove 62 and is adjusted inwardly or outwardly as necessary. In this manner, the wall members 80 and 82 are adjusted to properly size the device pocket 28 for a particular electronic device. When the fastener 50 is loosened, the compliant members 88 and 90 pull the nose 92 back towards the base 84.
Referring to FIGS. 9-11, a four-wall adjustable test socket assembly is generally indicated by reference numeral 120. Four-wall adjustable test socket assembly 120 includes a base plate 122 which is secured to the test fixture plate 24 by fasteners 124 in each corner of the base plate 122. A cam ring plate 126 is adjustably secured to the base plate 122. A cam ring plate 126 is adjustably secured to the base plate 122 by a fastener 128 which extends through an arcuate slot 130 in base plate 122 to an aperture 132 in cam ring plate 126. Cam ring plate 126 includes four cam profile arcuate slots 134 which are evenly spaced around the cam ring plate 126 and curve inwardly toward the inner edge 136 of the cam ring plate 126 so that a first end 138 of the cam profile arcuate slot 134 is radially spaced farther from the inner edge 136 than a second end 140 of the cam profile arcuate slot 134. In other words, each cam profile arcuate slot 134 follows an inward spiral toward the center of the cam ring plate 126.
The cam ring plate 126 includes four adjustable wall members 142. Each adjustable wall member 1452 includes a base 144 with a raised alignment stud 146, and a nose 148 with a beveled surface 150 extending to a pocket wall 152.
A dowel pin 154 extends through the raised alignment stud 146 of each adjustable wall member 142 through the base 144. The dowel pin 154 extends beyond the lower surface of the base 144 so that it can be inserted into the cam profile arcuate slot 134. The diameter of the dowel pin is approximately equal to the width of the cam profile arcuate slot 134.
When the four-wall adjustable test socket 120 is assembled, the four adjustable wall members 142 are captured between the cam ring 126 and the base plate 122. The raised alignment studs 146 extend through rectangular slots 156 in the base plate 122. The rectangular slots 156 are spaced 90 degrees apart and extend radially outwardly from a device pocket opening 158 in the base plate 122. The device pocket opening 158 is generally square and is centered in the base plate 122. It should be understood that the device pocket opening may be any shape as necessary to accommodate the periphery of an electronic device to be tested (not shown). An adjustment handle 160 attached to the outer periphery of the cam ring plate 126 extends beyond the periphery of the base plate 122.
When fastener 128 is loose, the adjustment handle may be moved between a first position in which the adjustable wall members 142 are fully retracted, and a second position in which the adjustable wall members 142 are fully extended. In the retracted position, the device pocket 162 is the maximum size. In the extended position, the device pocket 162 is the minimum size.
As the adjustment handle 160 is moved, the dowel pins 154 follow cam profile arcuate slots 134 and the raised alignment studs 146 slide within the rectangular slots 156. The rectangular slots 156 guide the adjustable wall members 142 radially inwardly and outwardly. The adjustable wall members 142 move in unison to keep the electronic device aligned and centered within the device pocket 162. When the adjustment handle 160 is rotated to the desired position, the fastener 128 is tightened to prevent the cam plate 126 from rotating and thereby locking the position of the adjustable wall members 142.

## Claims

1. A two-wall adjustable test socket for aligning an electronic device with an array of spring probes mounted in a test fixture plate, said two-wall adjustable test socket comprising:
a mounting plate having a device pocket and two fixed walls forming a corner, said mounting plate secured to said test fixture plate,
a pair of adjustable wall members slidably mounted to said mounting plate forming an adjustable corner opposite said fixed corner, each of said pair of adjustable wall members having a base,
a pair of compliant members extending from opposite sides of said base, and a nose secured to said pair of compliant members opposite said base, said nose forming a wall of said adjustable corner.
whereas the electronic device is secured to the test fixture and pressed into said device pocket to make contact with the array of spring probes, and whereas said nose of said adjustable wall members urge the electronic device into said fixed corner and into alignment with the spring probes,
wherein said mounting plate comprises a pair of alignment grooves, one each of said pair of alignment grooves extending outwardly from said device pocket and perpendicularly to said fixed walls,
wherein each of said pair of adjustable wall members comprises a rail extending from a lower surface of said base for engagement with one of said pair of alignment grooves in said mounting plate.

2. The two-wall adjustable test socket as set forth in claim 1 wherein each nose of said pair of adjustable wall members includes a beveled surface to guide the electronic device into said device pocket.

3. The two-wall adjustable test socket as set forth in claim 1 wherein each of said fixed walls of said mounting plate includes a beveled surface to guide the electronic device into said device pocket.

4. The two-wall adjustable test socket as set forth in claim 1 further comprising a pair of fasteners to secure each of said pair of adjustable wall members to said mounting plate in a fixed relationship to said two fixed walls.