Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1999-07-13
2001-11-13
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
Reexamination Certificate
active
06316954
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention involves devices for testing electronic components such as computer chips (sometimes referred to as integrated circuits) and/or other electrical and electronic devices, and, more particularly, to test interfaces which connect to a tester a circuit board upon which an electronic device is mounted.
DESCRIPTION OF THE PRIOR ART
Interfaces are used in electrically testing an electronic component such as a computer chip (the “device under test” or DUT). The DUT is typically mounted on a round circuit board (“DUT board”) which is clamped or otherwise held to the interface. The DUT board is then brought into contact with spring loaded contact pins (an example of which is referred to as “pogo pins”) which are electrically connected to a tester. The pogo pins contact conductive pads on the circuit board. These pads are connected to terminals on the DUT.
Typically the DUT board is mounted on guide pins on the interface. The DUT board is then locked down using a large wrench such as a spanner wrench, or a vacuum system which is typically used to pull the DUT board toward the pogo pins within the interface, and to hold the DUT boards against the pogo pins during testing. After testing the vacuum is released, and a spanner wrench or other large mechanical wrench is used to release the DUT board.
There are several problems inherent in the typical interfaces described above. It is awkward and time-consuming to use a spanner wrench or other mechanical wrench when inserting and removing the DUT board. Typical systems also tend to be heavy, weighing more than one person is able comfortably to carry around.
Further, the pogo pins are small and can be easily damaged. Pogo pins may be damaged when the DUT board is inserted into the interface, for example, by unintended contact with the DUT board or with tools used to install the DUT board. Damage to the pogo pins may also occur when the DUT board is brought into contact with them. Differential friction on the guide pins where the DUT board slides may cause the DUT board to “walk” (move first along one pin, and then along another) as it is moved by the vacuum system. This “walking,” if it occurs when the DUT board is in contact with the pogo pins, has a tendency to damage the tips of the pogo pins.
Typical systems also have the shortcoming of pogo pins being difficult and time consuming to replace.
The vacuum systems typically used to hold the DUT board against the Pogo pins introduce the further problem of vibrations or fluctuations being transmitted or propagated to the interface from the vacuum pump.
Another problem with typical interfaces with vacuum systems is that they are limited as to the number of pogo pins they can utilize. Each pogo pin is spring loaded, and therefore the combined spring force of all of the pogo pins opposes any effort to bring the DUT board in contact with the pogo pins. The limited pressure available to a vacuum system therefore limits the number of pogo pins that can be used in such a system. This limitation increases in importance as increasing numbers of pogo pins are desired for testing more complicated electronic devices.
Another desirable feature for a test interface is that it propagates signals quickly from the DUT board to the tester. As microprocessors continue to increase in processing speed, it is increasingly desirable to increase the speed of signals to the tester, in order to better test such faster-running chips.
From the foregoing it will be seen that it would be desirable to improve the characteristics of test interfaces in several aspects.
SUMMARY OF THE INVENTION
A test interface is used to connect an electronic device under test (“DUT”), such as a computer chip, to a tester. The interface utilizes a combination of spring forces and air pressure forces to extend and retract pogo pins. The pogo pins when extended contact conductive pads which are electrically connected to the DUT, for example via a DUT board. Springs are biased to extend the pins to contact the pads, and air pressure is used to retract the pins. Thus no air pressure is required to maintain the pins in contact with the pads. When retracted, the pogo pins are shielded from damage by a shield, such as a board with holes in it for the pogo pins to pass through.
According to one aspect of the invention, a test interface has pins that are protected from damage during loading and unloading of DUT boards by a shield between the pins and where the DUT board is loaded and unloaded.
According to another aspect of the invention, a test interface has retractable pins, the pins being maintained in contact with a DUT or a DUT board by a mechanical force.
According to yet another aspect of the invention, a test interface has retractable pins which are biased by a spring force to an extended position.
According to another aspect of the invention, a test interface has pogo pins which are housed in carriers, the carriers being easily removable from the interface and the pogo pins being easily removable from the carriers.
According to still another aspect of the invention, a test interface has pogo pins which are terminated to wire conductors of coaxial cable, and fabricated with an insert molded structure to form a channel or sub-assembly. These sub-assemblies are grouped and retained in carriers, so that they can be removed and replaced easily. In addition to the replaceability of sub-assemblies, individual pogo pin contacts can be replaced.
According to a further aspect of the invention, a test interface includes pogo pin ends partially embedded in plastic bodies, the plastic bodies being made of a plastic with a low dielectric constant, such as a Teflon-doped plastic, which in conjunction with the geometry of the pogo pins and their sockets, will control impedance while increasing the speed of the signal while it propagates through the pogo pins.
According to a still further aspect of the invention, a test interface has a cover which is secured to the rest of the interface by securing pins on the interface which fit into slots on the cover. According to a particular embodiment the slots are T-shaped, with differently-sized segments of the “T” for securing DUT boards having different thicknesses.
According to another aspect of the invention, a test interface has parts made out of aluminum, thus saving weight in comparison to steel test interfaces.
According to yet another aspect of the invention, a method of testing an electronic device includes the steps of retracting pogo pins which are part of a test interface, mechanically coupling the device to the interface, and extending the pins to electrically connect the pogo pins and the device.
According to a further aspect of the invention, a method of testing an electronic device includes the steps of mechanically coupling the device to a test interface, electrically connecting the device and the interface by extending pogo pins which are part of the interface, and using a mechanical force to maintain the connection between the device and the pogo pins.
According to a still further aspect of the invention, a method of testing an electronic device includes the steps of shielding pogo pins by retracting them into openings in a shield, mechanically coupling the device to a test interface, and electrically connecting the device and the interface by extending the pogo pins.
According to another aspect of the invention, a test interface includes a cable with a construction which optimizes high speed performance including impedance control, low loss and low propagation delay.
According to yet another aspect of the invention, a test interface includes pogo pin bodies each having two or more pogo pins partially embedded therein, the bodies fitting into carriers such that the pogo pins are arranged in an opposite signal-ground pattern.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in deta
Roath Alan L.
Tengler John
Venaleck John T.
Kerveros J
Metjahic Safet
Ohio Associated Enterprises, Inc.
Renner , Otto, Boisselle & Sklar, LLP
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