Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
2000-01-07
2002-10-08
Nguyen, Vinh P. (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
Reexamination Certificate
active
06462532
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to automatic test equipments, and more particularly to the structural design of remote test heads.
BACKGROUND OF THE INVENTION
To provide quality assurance, semiconductor device makers systematically perform tests on their products to ensure that they meet or exceed all of their design parameters. Some of the types of tests routinely performed include device parametric testing (a.k.a. DC testing), device logic function testing, and device timing testing (a.k.a. AC testing). The semiconductor device being tested is commonly known as the Device Under Test (DUT) and the test system used in conducting the above tests on the DUT is commonly known as Automatic Test Equipment (ATE). In carrying out the aforementioned tests on very sensitive DUTs, the ATE is necessarily very precise. In general, the ATE hardware is controlled by a computer which executes a test program to present the correct voltages, currents, timings, and functional states to the DUT and monitor the response from the device for each test. The result of each test is then compared to pre-defined limits and a pass/fail decision is made. As such, the ATE hardware normally includes a collection of power-supplies, meters, signal generators, pattern generators, etc. The Pin Electronics (PE) circuitry provides the interface between the ATE and the DUT.
U.S. Pat. No. 4,517,512 to Petrich et al. (hereinafter the '512 patent) shows an example of a prior art rack-and-stack ATE. As shown in FIG. 1 of the '512 patent, a control computer including display, power supplies, I/O peripherals (e.g., data storage drives, printers) are stacked on top of each other in a rack console which may be 19 inches wide. The ATE has a remote test head module which carries the instrument cards designed to provide voltages, currents, timings, and functional states to the DUT and to monitor the responses. A cable links the remote test head module to the equipments in the rack console to supply power from the rack console to the remote test head module as well as to allow the transfer of data and control/command signals between the rack console and the remote test head module. During testing, the remote test head module is attached to a test fixture underneath a prober/handler also attached to the test fixture. The prober/handler is used to hold the DUT and to position the DUT relative to the remote test head module. As computers and testers move into the gigahertz range, corresponding wavelengths are a few millimeters. At such wavelengths, almost any wire is an antenna causing signal radiation. Also, ATEs are now working with lower power levels, with currents in the microampere range. This increases the effects of electrical noise. Where higher powers are used to offset noise, transmission line losses occur thereby reducing efficiency. An advantage of this invention is that the distance from the instrument cards in the test head module to the DUT is kept reasonably short to reduce signal radiation, to improve the signal-to-noise ratio, and to reduce transmission line losses.
The instrument cards in the remote test head module are electrically and mechanically connected to each other in a stack-like fashion wherein a male connector on an instrument card is connected to a corresponding female connector on an immediately adjacent instrument card and so on. The connection established by connectors allow the instrument cards to communicate to each other. The instrument cards are connected to the rack console by the cable. The instrument card on top of the stack (a.k.a. the master instrument card) is connected to as many as 64 PE cards. To accommodate 64 PE cards, connectors are arranged in a circle on top of the master instrument card. A disadvantage in connecting instrument cards in a stack is that it does not allow for replacing an instrument card in the stack without disassembling and reconfiguring the instrument card stack. Such disassembly and reconfiguration are likely to result in down time for the ATE which may be undesirable. Another disadvantage in relying on connectors to mechanically connect instrument cards in a stack is that it limits the number of instrument cards that can be stacked and therefore the number of tests that can be carried out by the ATE. While additional mechanical fasteners may be used to secure the instrument cards together thereby allowing more cards to be stacked on top of each other, such fasteners increase costs as well as making it more difficult and time consuming to replace an instrument card.
To accommodate the increase number of tests performed by an ATE (e.g., in linear and mixed signals testing) as well as to improve the ability to replace instrument cards and/or reconfigure the test module rapidly, an approach has been developed wherein instrument cards with connectors are connected to corresponding connectors on a backplane such that the instrument cards are parallel to each other. In so doing, any instrument card can be removed and replaced quickly and easily. A prior art ATE
100
that employs this backplane approach is the ASL1000 that is manufactured by TMT Inc. of Sunnyvale, Calif. which is illustrated in FIG.
1
.
As shown in
FIG. 1
, remote test head module
101
is controlled by central processing unit (CPU)
111
with display monitor
112
and keyboard
113
. Power supply
114
supplies the required power to remote test head module
101
which interfaces with DUT
106
. Remote test head module
101
includes back plane
102
having up to twenty-one (21) parallel connectors on one side into which twenty-one instrument cards
103
are plugged. To converge the signals from twenty-one proprietary instrument cards
103
into a small test area that interfaces with DUT
106
, the opposite side of backplane
102
is connected to system interconnect board
104
. On the opposite side of backplane
102
, there are six (6) 96-pin connectors
107
to which six corresponding 96-pins connectors
108
of system interconnect board
104
are plugged. System interconnect board
104
is in turn connected to DUT board
105
. Accordingly, on the opposite side of system interconnect board
104
there are a plurality of connectors
109
to which corresponding connectors
110
of DUT board
105
are connected.
In this prior art ATE system, any individual instrument card
103
can be easily and rapid replaced. However, when replacement of a large number of instrument cards is involved, it may be necessary to remove interconnect board
104
from backplane
102
(e.g., for reconfiguration). This is quite challenging given the force required to simultaneously disengage/engage all five-hundred-seventy-six (6×96) pins of six connectors that connect backplane
102
to system interconnect board
104
. Accordingly, mechanical assistance may be required. Even with such a mechanical tool, it is still difficult to remove and replace interconnect board
104
rapidly.
Moreover, a test head module that is designed to seat multiple instrument cards like test head module
101
can be rather large in terms of size and weight (as much as 200 lbs) which makes it very difficult to move it close to a DUT let alone maneuvering, even with mechanical aids (e.g., manipulator, wheels, etc.), the test head module in a precise manner to properly connect the test head module with the DUT. As such, it may be necessary to connect PE circuitry to the test head module by a cable to get close to the DUT. This almost always degrades the signals.
Thus, a need exists for an ATE test head module that houses a large number of instrument cards, that allows for rapid reconfiguration of a backplane and replacement of instrument cards, as well as can be placed in close proximity with a DUT without requiring a mechanical manipulator and without requiring strenuous forces in reconfiguring the test head module.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides an Automated Test Equipment (ATE) test head module that houses a large number of instrument cards, that allows for rapid reco
Nguyen Vinh P.
Nguyen & Associates
Third Millennium Test Solutions
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