Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2000-06-22
2001-10-02
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C439S264000
Reexamination Certificate
active
06297654
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the testing of integrated circuit (IC) devices, and has particular application to the testing of optical IC devices where the IC must be illuminated by a light source to produce a detectable electrical response for test.
The testing of IC devices is typically accomplished using IC test sockets which hold a device under test (“DUT”) to a test board (often referred to as a “DUT board”) with the electrical contacts of the IC facing the DUT board. This orientation of the DUT is known as a “live bug” orientation referring to its resemblance to a live bug with its feet on the ground. While conventional IC socket designs are well adapted to the testing in a live bug orientation, a need exists for an IC socket which can accomplish a test of an IC in a “dead bug” orientation where the IC leads are reversed in the test cavity, that is, where the IC is on its back with its contacts facing up away from the DUT board . One class of IC devices that are best suited for testing in a dead bug orientation are optical IC devices having photoactive circuitry that must be illuminated to produce an electrical signal capable of being processed. Such optical ICs are used in a variety of applications ranging from optical sensors to digital cameras. When testing such ICs (“optical DUTs”) the photoactive circuitry of the optical DUT must be illuminated to produce a test result. Where automated pick and place machinery is used to load the test socket, an optical DUT cannot be easily illuminated since the photoactive circuitry is on the side of the DUT which is picked up by the pick and place arm of the automated handling equipment. Illumination from the side of the DUT would require a costly mechanism for doing so built into the automated handler.
The present invention provides a test socket and mechanism for efficiently testing a DUT in a dead bug orientation, and particularly for testing the optical DUT in a manner that facilitates illumination of the photoactive circuitry of the optical DUT during test. In accordance with the invention, the optical DUT can be illuminated from the light source below the DUT board, thereby allowing illumination of the DUT from below the DUT board without costly design modifications to the automated handler machinery.
SUMMARY OF THE INVENTION
In accordance with the invention, a test socket is provided for testing any IC device in a dead bug orientation and particularly an optical IC device having a photoactive side and a plurality of electrical contacts on an opposite facing contact side of the device. The test socket has a socket body having a top, a bottom for mounting to a test board, and a DUT cavity extending downwardly from the top of the socket body for receiving an optical DUT in a contact-up orientation. In the socket for an optical DUT, the bottom wall of the DUT cavity has at least one aperture through which the photoactive side of an optical DUT in a contact-up orientation can be illuminated. The test socket is further comprised of a plunger assembly which includes a top end, a plunger end insertable into the DUT cavity of the socket body, and an inner array of axial contact elements which extend through the plunger assembly. The inner array of axial contact elements are configured to make contact with the electrical contacts on the upper contact side of the optical DUT when the optical DUT, in its dead bug orientation, is contacted by the assembly's plunger end. In addition to the inner array of contact elements in the plunger assembly, an outer array of axially oriented contact elements is arranged about the DUT cavity for providing an electrical path through the socket body. A transverse conductor bridge at the top of the plunger assembly provides a transverse electrical path that spans the inner and outer contact elements of the plunger assembly and socket body elements. This conductor bridge electrically connects the inner and outer contact elements when the plunger assembly is fully inserted into the DUT cavity.
In accordance with the preferred embodiments of the invention, the inner and outer array of axial contact elements are provided in the form of low-profile, double-ended spring contact pins, sometimes referred to as “pogo pins,” while the transverse conductor bridge is provided in the form of a printed circuit board having conductor traces that extend from an inner end contacted by the inner array of axial contact elements of the plunger assembly to an outer end contacted by the array of axial contact elements of the socket body. Such a configuration provides a low-profile arrangement of conductors resulting in a low-profile test socket.
The invention also provides for a method of testing an optical IC device comprised of providing a test socket which includes a socket body having a DUT cavity and an aperture in the bottom wall of the DUT cavity. In accordance with the method, the optical DUT is placed in a contact-up orientation in the DUT cavity so that the photoactive side of the optical DUT is exposed through the DUT cavity aperture. The optical DUT is held in the DUT cavity by a plunger assembly having an array of contact elements configured to provide contact with the electrical contacts on the face-up contact side of the optical DUT. The contact elements of the plunger assembly are electrically interconnected by a conductor bridge to outer contact elements in the socket body of the test socket for providing an electrical path to the test board to which the test socket is mounted. The method can also be applied to test IC devices in a dead bug orientation other than optical DUTs.
Therefore, it can be seen that it is a primary object of the invention to provide a test socket and method for testing IC device in a dead bug orientation. It is another object of the invention to provide a test socket and method for efficiently testing an optical DUT. It is still a further object of the invention to reduce the cost of automated testing of optical DUTs. Still further objects of the invention will be apparent from the following specification and claims.
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Beeson Donald L.
Cerprobe Corporation
Kerveros James
Metjahic Safet
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