Data processing: measuring – calibrating – or testing – Testing system – Of circuit
Reexamination Certificate
2001-03-30
2004-12-07
Shah, Kamini (Department: 2863)
Data processing: measuring, calibrating, or testing
Testing system
Of circuit
C714S733000, C714S724000, C324S763010, C324S537000
Reexamination Certificate
active
06829553
ABSTRACT:
FIELD
The present invention pertains to automatic test arrangements for automatic testing of devices. More particularly, the present invention pertains to a method of and an apparatus for determining the correctness of the calibration of an automatic test arrangement and a method of and apparatus for correcting the fundamental calibration errors inherent in automatic test equipment, arrangements, and/or environments.
BACKGROUND
Newly manufactured products are generally tested prior to being delivered to customers in order to assure that the products perform as desired. In high volume manufacturing of products, such as electronic components, such acceptance testing is often performed by automatic test equipment. The test results, however, are only as good as the calibration of the automatic test equipment. This is a problem in general in acceptance testing, and it is a particular and fundamental problem in the acceptance testing of electronic components since the available operating speeds of such components are increasing, and the component operating speed is often faster than the operating speed of the automatic test equipment. Methods of calibration presently used, known, and/or available are limited in accuracy and have associated inherent errors. Consequently, in order to accurately evaluate and correct the results of testing by automatic test equipment, it is necessary to determine the correctness of the calibration of the automatic test equipment and to make and/or embed any modification and/or corrections to the base tester calibration and/or the test results that are necessary to obtain meaningful results.
The present invention is applicable to automatic test equipment, automatic test arrangements, and automatic test environments. In the following, these will all be referred to as automatic test arrangements, but it is to be understood that equipment, arrangements, and environments are included, as well as other appropriate meanings.
FIG. 1
is a block diagram commonly considered to depict an automatic test arrangement testing a device. Tester driver
10
applies a test signal to pin electronics card
12
, the output of which is connected to the input of tester interface unit
16
. The output of tester interface unit
16
is connected to the device under test
20
. Tester driver
10
, and pin electronics card
12
, might be a piece of general purpose automatic test equipment, while tester interface unit
16
is specifically adapted for testing of the particular device under test
20
on such a general purpose automatic test equipment.
The automatic test arrangement of
FIG. 1
can test device under test
20
by determining the electrical length of the signal path from tester driver
10
to device under test
20
, using time domain reflectometry. A signal is applied from tester driver
10
, through pin electronics card
12
and tester interface unit
16
to device under test
20
, and a resulting reflected signal is returned to tester driver
10
. The time between initiation of the signal by tester driver
10
and receipt of the reflected signal at tester driver
10
is used to determine whether device under test
20
is acceptable, as is well known in the art. That time is referred to as the electrical length of the signal path.
In practice the automatic test arrangement is calibrated with no device connected to the output of tester interface unit
16
. This calibration electrical length is:
EL=PEC+TIU
where EL is electrical length, PEC is the electrical length of pin electronics card
12
, and TIU is the electrical length of tester interface unit
16
. This electrical length might be determined under various conditions. One condition is with no ground connections. A second is with the output of tester interface unit
16
connected to ground by a grounding block. A third condition is with the output of pin electronics card
12
connected to ground by a first grounding block and the output of tester interface unit
16
connected to ground by a second grounding block. While each of these methods produces a calibration value for the automatic test arrangement, the calibration values differ, and, in fact, none of them is wholly accurate because none of them considers all of the electrical lengths involved in the test arrangement. Nevertheless, these three conditions are frequently used variously to calibrate automatic test equipment.
The electrical length of the automatic test equipment made up of tester driver
10
and pin electronics card
12
is generally tested to obtain a first calibration value which might be stored in a memory device of the pin electronics card. Because not all electrical lengths are considered, the measured value is the actual electrical length of the pin electronics card plus a calibration adjustment. One such value might be obtained and stored with the output of the pin electronics card open and another value obtained and stored with that output shorted to ground.
A second set of calibrations is generally performed to determine the electrical length of the pin electronics card and the tester interface unit, both with the tester interface unit output open, and with that output shorted to ground, and the resulting values might be stored in a memory device of the tester interface unit. Again, however, the measured values are the electrical length of the pin electronics card and the tester interface unit plus a calibration adjustment. Even so, these stored values do not properly reflect the calibration of the automatic test arrangement because they do not take into consideration all the electrical lengths involved. Consequently, it is difficult to correctly calibrate an automatic test arrangement.
SUMMARY
The present invention pertains to automatic test arrangements for automatic testing of devices. More particularly, the present invention pertains to a method of and an apparatus for determining the correctness of the calibration of an automatic test arrangement and a method of and an apparatus for correcting fundamental calibration errors inherent in an automatic test arrangement. Such an automatic test arrangement generally includes a tester driver, a pin electronics card having an input connected to the tester driver and an output connected to an output pin such as pogo pin, and a tester interface unit having an input connected to the pin electronics card output pin and an output connected to an output pin such as a socket pin. In accordance with the present invention, the electrical length from the tester driver to the socket pin is determined taking into consideration the pin electronics card output pin and the tester interface unit output pin. The actual electrical length from the tester driver, through the pin electronics card, the pin electronics card output pin, the tester interface unit, and the tester interface unit output pin to a grounding point of the device under test is determined. In a first embodiment of the invention, a second electrical length is determined from the tester driver, through the pin electronics card and the pin electronics card output pin to the tester interface unit, with neither the pin electronics card output pin nor the tester interface unit output pin grounded. With the tester interface unit output pin connected to ground by a shorting block, a third electrical length is determined from the tester driver, through the pin electronics card, the pin electronics card output pin, the tester interface unit, the tester interface unit output pin, and the shorting block to ground. A first difference value is determined as the difference between the first electrical length and the second electrical length. A second difference value is determined as the difference between the first electrical length and the third electrical length. A third difference value is determined as the difference between the first difference value and the second difference value, and the third difference value is evaluated to determine the correctness of the calibration of the automatic test arrangement.
In another embodiment of
Chema Greg P.
Jain Sunil K.
Intel Corporation
Shah Kamini
LandOfFree
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