Screen display for automated verification and repair station

Details Screen display for automated verification and repair station Screen display for automated verification and repair station

1999-04-27

2001-12-11

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C348S126000

Reexamination Certificate

active

06329830

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to screen displays for the automatic testing of bare printed circuit boards, and more particularly, to a screen display for a fault verification and repair station.
BACKGROUND OF THE INVENTION
Traditional manual bare circuit board fault verification has been a tedious process. Most of the associated equipment merely provided a visual aid in the fault verification process. Typically a flying prober would be utilized for this purpose which traditionally was used to test prototype circuit boards providing the benefit that a test fixture did not have to be devised for the prototype circuit board. Using a flying prober provided the benefit of making it easier to test fine pitch test sites on the circuit boards. A problem with flying probers is that they are slow in testing the circuit board due to the requirement for manually contacting each required test site on the circuit board, which in contrast to a fixture which can test all the test sites on the circuit board simultaneously.
Traditional repair stations have also been used for fault verification for bare circuit boards. Traditional repair stations are graphics based having software which illustrates the circuitry to indicate where the possible failure could be. The repair station utilizes the failure data from the tester and verifies the failure data by hand placement of probes. Software used in connection with traditional repair stations provides risk areas for areas such as shorts or opens based upon the physical layout of the circuitry and the likelihood of conductors in close proximity to each other. Plasma displays including a glass hood where the circuit is projected and the error is highlighted also have been used in repair stations. This method is unacceptable due to the ever shrinking size of today's circuit boards and the associated closeness of test locations. Conventional repair stations simply helped an operator locate a failed net end point designated by the tester, but stopped short of helping verify the fault and tracking down the location of the actual defect.
Flying probers have also been used in the repair process to verify error data from a tester. Typically there are two kinds of flying probers, namely, vertical probers and horizontal probers. In a vertical flying prober, the circuit board to be tested stands vertically upright and a probe contacts the board from either side depending upon the test site locations. The board is manually loaded and held in an upright position by hand manipulated clamps which are moved to the appropriate position and tightened to secure the circuit board. A disadvantage with vertical flying probers is that it is time consuming to manually move each clamp into position and manually manipulate the clamp to secure the circuit board. In the horizontal flying prober, the circuit boards are manually loaded into a drawer which is pulled out from the frame structure of the prober. Clamps hold the board to secure the circuit boards in a horizontal position. Again, the disadvantage in a horizontal flying prober is the time consuming and labor intensive procedure of manually loading boards in the drawer for testing.
Previous repair stations could not provide the user the ability to simultaneously view the board being tested in full along with particular potential failure areas highlighted against a standard to easily and quickly locate, identify and verify the error data. Consequently, a need exists for a flying prober verification and repair station with a screen display with an improved ability to track down the location of an actual defect and verify the fault.
SUMMARY OF THE INVENTION
The present invention is a novel screen display for an automated bare board fault verification and repair station having a locating and loading mechanism which atomically secures the circuit board to be tested or unit under test (UUT) in position. The fault verification and repair station of the present invention will also be referred to as a flying prober. The flying prober of the present invention includes, preferably, two pairs of X-Y-Z prober heads positioned one pair on each side of the unit under test which move independently across the surface of the circuit board to contact the desired test locations on the circuit board. Although two prober heads are preferred, more or less can be used, and on one or both sides of the UUT. The flying prober further includes electronic hardware and software for measuring isolations and continuities of the test sites electrically connected to the prober heads. The prober further includes a loading and locating mechanism for automatically securing the unit under test on the prober relative to the prober heads.
The loading and locating mechanism includes an upper housing and a lower housing one each positionable at opposite ends of the circuit boards. The housings include a lower lip for resting the edges of the circuit board on the housing. The lower housing is fixed on the frame of the flying prober and the upper housing is adjustable by screw clamps to accommodate different sized circuit boards. Positioned inside each of the upper housing and the lower housing is a movable clamping block having a plurality of finger springs rotatable by a dowel rod to lift and lower the springs above the upper surface of the circuit board. An air cylinder on either end of the clamping blocks moves the clamping block forward and backward. Similarly, an air cylinder, or other suitable actuator rotates the dowel rod to raise and lower the finger springs.
A camera is located on the prober head to view both the test probe in the prober head and the test site to verify the test probe is making contact with the test site. The camera image is generated on a computer screen for viewing by the operator of the verification and repair station.
In operation, the upper housing is manually set to the desired positioned according to the specific size of the circuit board to be tested by securing the screw clamps to the frame. The circuit board to be tested is then positioned on the housing such that the edges of the circuit board rest on the lip of the upper and lower housing. Because the frame is angled, gravity allows the circuit board to be located on the clamping mechanism. With the finger springs in a raised position, the clamping blocks are actuated forward towards the circuit board to position the ends of the finger springs over the edge of the circuit board. The dowel rod is then actuated to lower the finger springs into contact with the upper surface of the circuit board along the edge to securely clamp the circuit board in the flying prober. The prober heads are then actuated across the surface of the circuit board to conduct the fault verification process. The dowel rod, clamping block and prober heads are automatically operated and controlled by the software programed within the flying prober. The test probe contacts the test sites and the camera projects the image to verify contact between the test probe and the test sites.
The verification and repair station initially reads a data file corresponding to the circuit board to be tested. The station then reads in the error file from a grid tester or prober which prints a bar card report. Next, the verification process generates files that include all of the defect locations, identifications and video images. When the optional bar code is scanned at the repair station, the repair operator is led defect by defect through the unit under test. The CAD data is cross-referenced with the failure data location. Software includes the ability to evaluate which risk area has a higher probability of having the error location by strategically choosing test locations to measure resistance levels between the locations and choose risk areas based upon lowest resistance measurement between those test locations. This is accomplished by starting with the risk area with the closest test site locations and choosing test site locations closest to the risk area by measuring the resistance between those t

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