Patent Application
20060110953
Not Applicable
Not Applicable
Not Applicable
1. Background—Field of Invention
This invention relates to making interconnections between electronic components, especially microelectronic components and, more particularly, to providing techniques for making temporary connections for semiconductor packages to circuit boards.
2. Background—Description of Prior Art
When a semiconductor manufacturer develops a new electronic device, it is subjected to a series of tests prior to production release. A common way to accelerate these qualification tests is to operate the device in a high temperature chamber. This testing at high temperatures is known as burn-in. During some qualification testing, certain electronic devices exhibit a high rate of infant mortality. Infant mortality refers to the early-life failures often observed in the “bath tub” shape statistical distribution of failures versus time. Devices of this type can usually be expected to function for years if they survive the initial hours of operation. When necessary, production lots can be screened for early failures by subjecting the devices to burn-in.
It is possible to solder the devices directly to a PCB and remove the devices after the burn-in but this is time-consuming, costly and potentially damaging to the device. A burn-in socket forms a temporary mechanical “nest” to hold the device and provide electrical contact during burn-in without damaging it.
There are many standard semiconductor package styles, each with a unique socket type and interconnection mechanism. Each package has dimensions that can vary from one manufacturer to another, and within each run of devices there may be piece to piece variation within Joint Electronic Device Engineering Council (JEDEC) specifications. As more and more contacts may be added and devices become more complex, precise positioning is more important, especially for test and burn-in. In that case, one would need to be able to accommodate more variation than, for example, in a manufacturing line where quite a number of pieces from the same supplier would be installed during a particular shift.
Various burn-in board sockets have been designed to accept the IC devices. However, as the distance between contacts, the pitch, tightens it becomes the same magnitude as the tolerance of fixed size nests so some form of compliance for dimensional variation may be necessary.
Objects and Advantages
It is an object of the present invention to provide a means of assuring that the device will be centered in the test and burn-in socket in the two dimensions of the plane of the contacts regardless of size variation, within certain limits.
It is a further object of the present invention to provide a means of assuring that the device will be centered in the test and burn-in socket regardless of any skewing that occurs during insertion.
It is another object of the present invention to maintain the position of the device throughout the test and burn-in period.
The present invention is envisioned as falling into one of four different embodiments, all of which achieve the same result by somewhat different means. In each case the device is placed in approximate position either manually or by a robot. Following its placement, a clamping device applies a downward pressure as lateral positioning devices move the device in two dimensions to its final centered test position, determined by the lateral positioning devices.
One embodiment has centering blocks that are pivoted so they move in a vertical plane, although the movement to center the DUT is so slight that their movement is essentially in a horizontal plane. The centering blocks are spring loaded and are held back away from the DUT for its insertion and removal.
Another embodiment is a rack and pinion arrangement where four mutually perpendicular racks are moved simultaneously by a single pinion. Four positioning blocks are attached to each of their respective racks and move in and out at equal rates until contact is made with all four sides of the device under test (DUT). At this point the DUT is centered and further downward pressure may be applied to ensure electrical contact with the test leads.
In another embodiment, instead of a rack and pinion arrangement, the centering blocks are pivoted so they swing in a horizontal plane and are spring loaded against the DUT. Insertion of the DUT is enabled by a mechanism that retracts the centering blocks against the spring tension to allow insertion. A further mechanism is included to apply a downward pressure to enable electrical contact.
Finally, the fourth embodiment comprises a moveable frame that can be pressed down to open the centering blocks and released to provide the centering force. This movement is achieved by means of four rack and pinion sets, a “multi-rack”, wherein the pinions are attached to the centering blocks and the racks are attached to the frame mentioned previously and move vertically.
More details of the four embodiments will be apparent from the figures and the detailed description.
A second embodiment of a method for centering the device for testing using a multiple rack and single pinion assemblage, is shown in
The rack and pinion assemblage of
Still another mechanism for achieving accurate centering of the DUT is shown in
The mechanism of
In
As in the previous embodiments of the centering mechanism, this one can be incorporated in a clamshell base 90 or open top test socket base 92 as shown in
Four different centering techniques have been shown incorporated in two different types of test socket bodies. Other methods and variations of the methods presented here may become apparent to one skilled in the art. One such variation is the replacement of the compression springs with torsion or cantilever beam springs in all embodiments. Another possible variation is the mechanism to hold back the centering pads, not shown in these figures, may be a screw, an inclined plane, a cam, or by some other method in all embodiments. Yet another possible variation is that the automatic positioner mechanism may be activated by the lid of the clamshell or pusher in the open top or it may be separately activated through a lever arm, knob, or other means. This disclosure is not intended to be limiting and exclusive, but should include all the obvious variations.
