U.S. patent application number 12/628741 was filed with the patent office on 2010-08-05 for high-speed capacitor leakage measurement systems and methods.
This patent application is currently assigned to Rudolph Technologies, Inc.. Invention is credited to Charles Corulli, Gregory Olmstead, Donald B. Snow.
Application Number | 20100194406 12/628741 |
Document ID | / |
Family ID | 38328075 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100194406 |
Kind Code |
A1 |
Corulli; Charles ; et
al. |
August 5, 2010 |
HIGH-SPEED CAPACITOR LEAKAGE MEASUREMENT SYSTEMS AND METHODS
Abstract
Systems and methods according to aspects of the present
invention are described. The systems and methods enable charging,
soaking, and measuring of capacitors to be conducted quickly.
Charging and soaking typically occurs in parallel and certain
embodiments facilitate the measuring of capacitor leakage by
sequentially disconnecting each capacitor and measuring the time
for voltage on the capacitor to reach a predetermined threshold.
Further, all capacitors can be disconnected from a charging source
simultaneously and voltages can be measured for each capacitor
simultaneously. Monitoring can be periodic in nature. Substantial
time savings in the calculation device of leakage values and
parameters can be attained.
Inventors: |
Corulli; Charles; (Issaquah,
WA) ; Olmstead; Gregory; (Sammamish, WA) ;
Snow; Donald B.; (Mercer Island, WA) |
Correspondence
Address: |
Dicke, Billig & Czaja, PLLC;ATTN: Christopher McLaughlin
Fifth Street Towers, Suite 2250, 100 South Fifth Street
Minneapolis
MN
55402
US
|
Assignee: |
Rudolph Technologies, Inc.
Flanders
NJ
|
Family ID: |
38328075 |
Appl. No.: |
12/628741 |
Filed: |
December 1, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11668457 |
Jan 29, 2007 |
7663382 |
|
|
12628741 |
|
|
|
|
60762967 |
Jan 27, 2006 |
|
|
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Current U.S.
Class: |
324/659 |
Current CPC
Class: |
G01R 31/64 20200101;
G11C 29/50 20130101; G01R 31/27 20130101; G11C 29/50016 20130101;
G11C 2029/5002 20130101 |
Class at
Publication: |
324/659 |
International
Class: |
G01R 27/26 20060101
G01R027/26 |
Claims
1. A method for measuring capacitor leakage comprising: accessing a
list of plurality of capacitors; providing a charging current to
the plurality of capacitors, wherein the current charges and soaks
the plurality of capacitors; selecting first and second capacitors
from the plurality of capacitors; disconnecting the charging
current from the first and second selected capacitors; connecting
the first and second selected capacitors to a voltage sensor;
measuring first and second voltages of the first and second
selected capacitors; comparing first and second measured voltages
of the first and second selected capacitors to a predetermined
threshold voltage; determining whether first and second measured
voltages of the first and second selected capacitors have crossed
the predetermined threshold voltage; and adjusting the list of the
plurality of capacitors as a function of determining whether first
and second measured voltages of the first and second capacitors
have crossed the predetermined threshold voltage.
2. A method according to claim 1, wherein the step of disconnecting
is performed simultaneously for all of the plurality of
capacitors.
3. A method according to claim 1, wherein the step of disconnecting
is performed simultaneously for the first selected capacitor and
the second selected capacitor.
4. A method according to claim 3, wherein the step of determining
is performed simultaneously for the first selected capacitor and
the second selected capacitor.
5. (canceled)
6. A method according to claim 5, wherein the first and second
selected capacitors are disconnected from the voltage sensor after
voltage of the first and second selected capacitors are
measured.
7. A method according to claim 6, wherein voltages on each of the
first and second selected capacitors are measured periodically
until a corresponding time required to discharge the first and
second selected capacitors has been determined.
8. A method according to claim 1, wherein the step of adjusting
comprises removing at least one of the first capacitor and the
second capacitor from the list.
9. A method according to claim 1, wherein the steps of
disconnecting and determining are repeated for the second selected
capacitor after the time to discharge the first selected capacitor
is determined.
10. A method according to claim 1, and further comprising
calculating leakage values for the first and second capacitors as a
function of time.
11. A system for measuring capacitor leakage comprising: a
plurality of charging switches, each charging switch controlling
connection of one of a plurality of capacitors to a charging
source; a plurality of sensing switches, each sensing switch
controlling connection of one of the plurality of capacitors to a
voltage sensing device; a controller operative to control the
plurality of charging switches and the plurality of sensing
switches wherein the controller is configured to cause all of the
plurality of capacitors to be charged and soaked simultaneously,
connect selected ones of the plurality of capacitors to the voltage
sensing device according to a programmed sequence based on a list
of the plurality of capacitors, and for each step in the programmed
sequence, provide a measurement of voltage on a capacitor currently
connected to the sensing device and determine whether a capacitor
should remain on the list based on the measurement; and a computing
device programmed to determine leakage values for each of the
plurality of capacitors based on a measurement of time after each
capacitor is disconnected from the charging source.
12. The system of claim 11, wherein the plurality of charging
switches is provided by a switch matrix.
13. The system of claim 11, wherein the plurality of sensing
switches is provided by a switch matrix.
14. The system of claim 11, wherein the plurality of charging
switches and the plurality of sensing switches are provided by a
switch matrix.
15. The system of claim 11, wherein all capacitors of the plurality
of capacitors are simultaneously disconnected from the charging
source.
16. The system of claim 15, wherein the controller is further
configured to connect each of the plurality of capacitors to the
sensing device periodically.
17. The system of claim 11, wherein the controller is further
configured to disconnect each of the plurality of capacitors from
the sensing device sequentially.
18-20. (canceled)
21. A method for measuring capacitor leakage comprising: applying a
current to a plurality of capacitors simultaneously, the current
being applied for sufficient time to charge and soak each of the
plurality of capacitors; recording for each of the plurality of
capacitors a first voltage obtained as a result of charging and
soaking each of the plurality of capacitors; discharging separately
and simultaneously the plurality of capacitors; after a
predetermined period, measuring successively a second voltage for
each of the plurality of capacitors as the plurality of capacitors
discharges; recording the second voltage and time duration, as
measured from the start of the separate and simultaneous discharge
of the plurality of capacitors; and determining from the first and
second voltages whether the capacitor leakage of a particular
capacitor of the plurality of capacitors has reached a
predetermined threshold value.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 11/668,457, titled "High-Speed Capacitor
Leakage Measurement Systems and Methods" and filed Jan. 29, 2007,
which claims benefit of priority from U.S. Provisional Patent
Application Ser. No. 60/762,967, titled "System and Method for
High-Speed Capacitor Leakage Measurements" and filed Jan. 27, 2006,
the contents of which are incorporated herein by reference and for
all purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to the field of
electrical test methods and equipment and more particularly to
high-speed electrical testing of capacitors
[0004] 2. Description of Related Art
[0005] Rapid testing of capacitor leakage is important in the
semiconductor industry. In the semiconductor industry, many
replicate components, or die, are created on a single semiconductor
wafer. Each of the individual die are electrically tested, commonly
with a method called "probing." During the probing process, a grid
array of fine tungsten wires is touched down on the metallized
bonding pads of each die. The tungsten wires are in turn connected
to test equipment that is used to evaluate the electrical quality
of each die. More specifically, the fine tungsten wires, or other
contact media, known in the art as "probe card pins" or "probe
pins," are arranged on conventional printed circuit boards or test
cards known in the art as "probe cards" or "probe array cards."
Probe cards are in turn connected to electrical test equipment
known in the art as "probers" or "prober machines."
[0006] Precision is important when testing electrical components
but obtaining test results in a timely fashion is often equally
important. This is especially true when many components are to be
tested. An ideal capacitor that is charged to a steady state
condition and disconnected from other components would hold its
charge forever. However, certain intrinsic properties of real
capacitors cause discharge over time. As depicted in FIG. 1, after
a capacitor 10 is charged to voltage V.sub.C 16, extrinsic
components 12 such as inadvertent connections or solder flux can
cause or increase a leakage current 14 that results in discharge of
capacitor 10. By measuring the leakage properties of capacitor 10,
it is possible to determine if capacitor 10 meets its
specifications, is installed properly, and whether connected or
surrounding circuits are behaving as expected.
[0007] Referring now to FIG. 2, conventional methods of leakage
testing test one capacitor 10 at a time. A voltage source initially
provides voltage V.sub.C 16 to charge and soak capacitor 10. Once
capacitor 10 is fully charged and soaked, a voltage source 20
provides a current to sense resistor 24 and the resultant voltage
drop across sense resistor 24 is recorded as a measurement 220
(provided by voltage detector 22) of the amount of current required
to counteract leakage current 14 such that capacitor 10 holds its
charge. Various problems arising from this method to leakage
measurement make the method unattractive for measuring complex
systems that may contain hundreds or even thousands of large
capacitors. One problem lies with the sense resistor 24. To achieve
adequate resolution for very small currents, the conventional
approach requires utilizing a large sense resistor 24. For example,
a capacitor leakage current 14 of 5 nA would cause only a 500 .mu.V
across a 100 K.OMEGA. sense resistor 14 and, in the example, a test
capacitor 10 having a capacitance of 100 .mu.F would have a 10
second time constant. Such a circuit time constant would require
approximately 150 seconds to charge, soak, and settle a capacitor
10.
[0008] Another problem with the method of testing is the limitation
that only one capacitor can be tested at a time. For a circuit
containing over 100 capacitors, it may take over four hours to
obtain accurate leakage currents for the entire circuit. A
conventional probe card may contain hundreds of capacitors that
require repeated testing throughout the probe card's development
and useful life. A manufacturer loses revenue for every minute that
the probing process is inoperable, due to a probe card malfunction
for example. What is needed in the art is a high speed method for
accurately testing a multitude of capacitors.
SUMMARY OF THE INVENTION
[0009] Certain embodiments of the present invention resolve issues
and difficulties associated with the measurement of capacitor
leakage current. Certain embodiments provide systems and methods
that enable charging, soaking, and measuring of capacitors to be
conducted quickly and in parallel.
[0010] Certain embodiments of the invention provide systems and
methods for measuring capacitor leakage comprising the steps of
providing a charging current to a plurality of capacitors, wherein
the current charges and soaks the plurality of capacitors.
Capacitors can be disconnected from the charging current and their
voltage monitored according to a programmed sequence. Monitoring
can be periodic in nature. Typically, large numbers of capacitors
can be charged and soaked in parallel. The time required for
discharge of the capacitors can be monitored sequentially and in
parallel, thereby generating substantial time savings in the
calculation device of leakage values and parameters.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic representation of leakage in a
capacitor.
[0012] FIG. 2 is a schematic representation of a simplified example
of a measurement system according to certain aspects of the
invention.
[0013] FIG. 3 is a schematic representation of a simplified example
of a measurement system capable of parallel sensing according to
certain aspects of the invention.
[0014] FIG. 4 is a schematic representation of an example of a
measurement system according to certain aspects of the
invention.
[0015] FIG. 5 is a schematic representation of an example of a
measurement system according to certain aspects of the
invention.
[0016] FIG. 6 is a flowchart of a process for measuring leakage
according to certain aspects of the invention.
[0017] FIG. 7 is a block schematic showing components of a leakage
measurement system according to certain aspects of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Embodiments of the present invention will now be described
in detail with reference to the drawings, which are provided as
illustrative examples so as to enable those skilled in the art to
practice the invention. Notably, the figures and examples below are
not meant to limit the scope of the present invention to a single
embodiment, but other embodiments are possible by way of
interchange of some or all of the described or illustrated
elements. Wherever convenient, the same reference numbers will be
used throughout the drawings to refer to same or like parts. Where
certain elements of these embodiments can be partially or fully
implemented using known components, only those portions of such
known components that are necessary for an understanding of the
present invention will be described, and detailed descriptions of
other portions of such known components will be omitted so as not
to obscure the invention. In the present specification, an
embodiment showing a singular component should not be considered
limiting; rather, the invention is intended to encompass other
embodiments including a plurality of the same component, and
vice-versa, unless explicitly stated otherwise herein. Moreover,
applicants do not intend for any term in the specification or
claims to be ascribed an uncommon or special meaning unless
explicitly set forth as such. Further, the present invention
encompasses present and future known equivalents to the components
referred to herein by way of illustration.
[0019] Certain embodiments of the present invention provide systems
and methods for measuring capacitor leakage that can be
incorporated in metrology and other systems. Before measuring
leakage in a capacitor, the capacitor may first be charged and
soaked. A capacitor is typically charged to obtain a desired steady
state voltage across the capacitor and at measurement nodes or
points. Soaking can be defined as the time required to minimize
dielectric absorption contribution in the capacitor. The dielectric
absorption contribution is proportional to the capacitance value.
For example, a 0.1 .mu.F capacitor must soak for approximately 0.5
seconds while a 1000 .mu.F capacitor must soak for approximately
300 seconds.
[0020] Referring to FIG. 3, in certain embodiments of the
invention, a capacitor 10 can be fully charged and soaked using a
charging source 30 such as a voltage source, a current source, or
other charging system. In certain embodiments, a series resistor 32
can be used that has a smaller value than required in conventional
measurement systems and methods. Series resistor 32 is typically
provided to limit current provided to the capacitor. Because of the
reduced resistance value of series resistor 32, the time constant
of the circuit can be relatively small, even for large capacitor
values.
[0021] After charging and soaking, the charging source 30 may be
disconnected from capacitor 10 using a first switch 34 which may be
regarded as a charging circuit control switch. A second switch 36
can then connect the charged capacitor to a voltage sense circuit
38 to provide a measurement 380 of capacitor voltage 340. In
certain embodiments, capacitor voltage 340 may be monitored over a
period of time. In certain embodiments, monitoring capacitor
voltage 340 can include periodically measuring capacitor voltage
340.
[0022] In certain embodiments, monitoring can be performed by a
computer system configured to control measurement of voltages,
record data, and calculate capacitor parameters including leakage
current. In performing measurements and associated calculations,
measurements of capacitor voltage 340 may be recorded before and/or
after the voltage source 30 is disconnected from capacitor 10.
Capacitor voltage 340 may then be monitored until it has dropped by
a predetermined value or crossed a predetermined threshold. In one
example, a discharge time and change in voltage can be monitored
and recorded and, based on these measured values, leakage current
may be calculated as follows:
I = C v t . Equation 1 ##EQU00001##
[0023] The period of time over which measurements are taken can
vary depending upon test circumstances, capacitor characteristics,
measurement system accuracy and so on. In certain embodiments, the
time required for voltage to drop sufficiently may be measurable in
tens of seconds.
[0024] In certain embodiments, nominal characteristics of capacitor
10 may be determined using any suitable means having sufficient
accuracy. Characteristics can include capacitance which can be
analytically determined for each component prior to measuring
leakage. Characteristics of a device can be maintained in storage
for use in subsequent tests. It will be appreciated that more than
one method can be employed or combined to determine component
characteristics. Methods are typically selected based on parameters
and configuration requirements including the characteristics of
individual devices, characteristics of groups of devices and
circuit configuration and characteristics.
[0025] Referring to FIG. 4, certain embodiments provide systems and
methods for charging and soaking multiple capacitors
simultaneously. In the example shown in FIG. 4, a charging source
42 can provide a current to more than one capacitor
(C.sub.1-C.sub.n) 400.sub.1-400.sub.n in order to charge and soak
each capacitor 400.sub.1-400.sub.n simultaneously. Typically, one
or more switches 402.sub.1-402.sub.n electrically connect charging
source 42 through optionally provided series resistor 46. After
being charged and soaked, a first capacitor 400.sub.1 may be
removed from the charging source 42 by opening a corresponding
switch 400.sub.1. First capacitor 400.sub.1 may then be connected
to a measurement device 44 by closing switch 404.sub.1. Typically,
other switches 404.sub.2-404.sub.n are opened to isolate first
capacitor 400.sub.1 from the other capacitors 400.sub.2-400.sub.n
during voltage measurement.
[0026] In certain embodiments, electrical connection between
charging source 42 and each of the other capacitors
400.sub.2-400.sub.n is maintained until the leakage of first
capacitor 400.sub.1 can be measured and recorded. A second
capacitor 400.sub.2 may then be measured in similar fashion. Each
of capacitors 400.sub.1-400.sub.n can be tested sequentially until
all of the capacitors 400.sub.1-400.sub.n have been tested. It will
be appreciated that significant time savings accrue from the
simultaneous charging and soaking of two or more capacitors under
test.
[0027] In certain embodiments additional time savings can be
obtained by measuring capacitor leakage of more than one capacitor
at the same time. For example, capacitors 400.sub.1-400.sub.n may
be connected to charging source 42 by closing each of charging
switches 402.sub.1-402.sub.n to permit capacitors to be charged and
soaked simultaneously and in parallel. Next, each of capacitors
400.sub.1-400.sub.n may be disconnected from the charging source
and from one another by opening charging switches
402.sub.1-402.sub.n. Sensing switches 404.sub.1-404.sub.n are
typically maintained opened before charging source 42 is
disconnected from capacitors 400.sub.1-400.sub.n. Capacitors
400.sub.1-400.sub.n may then be allowed to discharge separately but
simultaneously.
[0028] Next, the voltage on each of capacitors 400.sub.1-400.sub.n
can be measured individually by sequentially closing and then
reopening each of switches 404.sub.1-404.sub.n, or selected ones of
the switches, typically in a periodic fashion. Thus, at each step
in a repeating sequence, the voltage across one of capacitors
400.sub.1-400.sub.n can be measured in isolation from the voltage
on the other capacitors. The time at which voltage across each
capacitor 400.sub.1-400.sub.n is detected to have dropped below a
predetermined threshold value can then be recorded; e.g. a
predetermined threshold value may be set at 10 mV and the time
measured represents the elapsed time for a voltage to reach the 10
mV or for the absolute value of the voltage to decrease by 10 mV.
In certain embodiments, measurements of elapsed time may be
expressed in terms of the periodicity of the sequence.
[0029] Leakage calculations can be performed using the measured
elapsed times and results stored and processed further as desired.
In certain embodiments, measurement of voltage across a capacitor
can cease when the voltage crosses the predetermined threshold.
However, it may be advantageous to continue measurement of all
voltages to obtain a more complete characteristic of each
capacitor. Bypass switch may be used to discharge all capacitors
400.sub.1-400.sub.n and to calibrate voltage sensing device 44 and
for other purposes.
[0030] Referring now to FIG. 5, in certain embodiments, multiple
sensing devices 54 and 55 can be used to measure capacitor leakage
in large numbers of capacitors 500.sub.1-500.sub.n. Capacitors
500.sub.1-500.sub.n may be initially electrically connected to
charging source 52 through charging circuit switches
502.sub.1-502.sub.n such that each of capacitors
500.sub.1-500.sub.n are charged and soaked in parallel. Two or more
of capacitors 500.sub.1-500.sub.n may then be disconnected from the
charging source and from one another by opening selected ones of
switches 502.sub.1-502.sub.n. In certain embodiments, all
capacitors 500.sub.1-500.sub.n are monitored simultaneously and
thus all capacitors are disconnected from the charging source 52
and from each other by opening switches 500.sub.1-500.sub.n.
Thereafter, each of sensing devices 54 and 55 can be connected to
one of capacitors 500.sub.1-500.sub.n for measuring current
voltage. As described above, sequential measurement of voltage on
individual ones of capacitors 500.sub.1-500.sub.n can be performed
by one of voltage sensors 54 and 55 by sequencing closure of
switches 504.sub.1-504.sub.n. It will be appreciated that the
quantity of voltage sensors to be used may be determined by factors
including the number of items to be tested, sample times associated
with voltage sensors 54 and 55 and processing capabilities of
computers and controllers used in the system. Additionally, the
sequencing of switches 504.sub.1-504.sub.n can be configured to
initially prioritize measurements based on capacitor size, circuit
configuration and other parameters. This prioritization can allow
frequent sampling of voltages for rapidly discharging capacitors
and discontinuation of sampling of these rapidly discharging
capacitors when they cross predetermined threshold voltage levels.
Thus, sampling rates for more slowly discharging capacitors can be
increased over time.
[0031] In certain embodiments the time elapsed during leakage
measurement of large numbers of capacitors can be little or no more
than the time required to measure leakage in the capacitor having
the longest discharge time. Thus, time savings can be accrued by
replacing an essentially serial measurement process with highly
parallel processes and methods. These methods may be able to
accommodate large numbers of different capacitor values that can be
measured in thousands.
[0032] FIG. 6 is a simplified flow diagram further illustrating
certain aspects of the invention. At step 600, a list of capacitors
to be tested can be generated. The list may identify all capacitors
on a device or in a circuit together with corresponding operational
characteristics. The list may be obtained electronically from
previously entered information, from CAD CAM systems and by manual
entry. Next, capacitance of each item may be individually measured
at step 602 until capacitance for all items in the list is obtained
(step 604). The list can include a combination of previously known
capacitance values and newly measured capacitances. At step 606,
the capacitors are charged and soaked. Charge and soak time can be
calculated from the information provided that identifies the
capacitance of the items to be tested. This information may include
other data affecting charge and soak time. Typically, a timeout
controls charge and soak time at step 608, although other methods
of determining charge and soak periods may be implemented. At step
610, charging sources have been removed from one or more capacitors
and discharge is in progress. Discharge is monitored, typically
using voltage sensing. If the voltage on the capacitor has passed a
threshold value at step 612, the elapsed time can be recorded for
the capacitor and the capacitor may optionally be removed from the
list of items to be monitored at step 613. At step 614, the list is
checked to determine if any items are still to be monitored or
measured. If items remain on the list, then monitoring continues.
If items are being monitored individually, then a next device to be
measured is disconnected from the charging source. Monitoring
continues.
[0033] Table 1 provides an example potential improvement in
capacitor leakage test time of the present invention over that of
the conventional method in an example where leakage in one hundred
100 .mu.F capacitors is measured.
TABLE-US-00001 TABLE 1 Charge Soak Measure Time Time Capacitor Time
Total Test (sec) (sec) Time (sec) (sec) Time (min) Conventional 63
15000 2.5 2000 284.4 Method Parallel charge/ 63 150 2.5 2000 36.9
soak Parallel 63 150 2.5 20 3.9 charge/soak/ measure
[0034] FIG. 7 is a simplified block diagram of an embodiment
illustrating certain aspects of the present invention. A computing
device 70 may be provided to initiate measurements, to receive
measured data and to calculate desired results. The computing
device 70 can be any suitable device including a personal computer,
an embedded processing system calculator or microcontroller. In
certain embodiments, computing device 70 communicates with a
control processor 72 configured to respond to commands from the
computing device 70 and to generate control signals, manage or
provide charging sources 74 and to manage or provide voltage
sensing 75 of output voltages from devices under test 78.
Controller 72 may also manage or provide analog-to-digital and
digital-to-analog converters used in controlling the test process
and measuring leakage. Controller 72 may also facilitate
communications between processor 70 and test equipment and devices
under test 78. The computing device 70 can be used to sequence the
measurement of voltages on the devices under test 78. Sequencing
can be accomplished by providing timing and order information
indicating at which times the different switches should be opened
or closed. This information may be provided to the controller 72 as
address and time interval information, etc. Sequence information
may also be directly provided as control signals to a switch matrix
76.
[0035] In certain embodiments, current and voltage source
electronics 74 may be provided to generate analog currents and
voltages responsive to signals received from the control processor
72. A switch matrix 76 is typically configured to receive analog
voltages and currents from current and voltage source electronics
74 and to transmit these voltages and currents to devices under
test 78. Sensing electronics 75 may receive signals obtained from
the devices under test 78 and transmitted by switch matrix 76.
Sensing electronics 75 can provide analog or digital signals
representative of measurements of voltage and current values sensed
by sensing electronics 75.
[0036] In certain embodiments, a single switching matrix 76 can
provide switched pathways between charging sources 74 and devices
under test 78 and from devices under test 78 to sensing electronics
75. Switch matrix 76 may provide and receive other signals to and
from the control processor 72. In certain embodiments, separate
switching matrices 76 provide pathways to and pathways from devices
under test 78. In certain embodiments, switch matrix 76 can
comprise more than one matrix, and can be stacked or arranged in
hierarchical fashion as necessary to support the number items
included in devices under test 78. In certain embodiments, switch
matrix 76 may be configured to provide multiple channels, each
channel associated with one or more circuits under test; channels
may or may not contain capacitors. In certain embodiments, switch
matrix 76 may be directly controlled by the computing device
70.
Additional Descriptions of Certain Aspects of the Invention
[0037] Certain embodiments of the invention provide methods for
measuring capacitor leakage comprising the steps of providing a
charging current to a plurality of capacitors, wherein the current
charges and soaks the plurality of capacitors, selecting a first
capacitor from the plurality of capacitors, disconnecting the
charging current from the selected capacitor, determining a time
required to discharge the selected capacitor by a predetermined
amount, and selecting a second capacitor from the plurality of
capacitors and repeating the steps of disconnecting and determining
for the second selected capacitor. In certain embodiments, the step
of disconnecting is performed simultaneously for all of the
plurality of capacitors. In certain embodiments, the step of
disconnecting is performed simultaneously for the first selected
capacitor and the second selected capacitor. In certain
embodiments, the step of determining is performed simultaneously
for the first selected capacitor and the second selected capacitor.
In certain embodiments, the step of determining includes comparing
a measured voltage of the selected capacitor to a predetermined
threshold voltage, wherein voltage of the selected capacitor is
measured by connecting the selected capacitor to a voltage sensor.
In certain embodiments, the selected capacitor is disconnected from
the voltage sensor after voltage of the selected capacitor is
measured. In certain embodiments, voltages on each of the first and
second selected capacitors are measured periodically until a
corresponding time required to discharge the first and second
selected capacitors has been determined. In certain embodiments,
the step of determining is performed simultaneously for each of the
plurality of capacitors, wherein voltage on each capacitor in the
plurality of capacitors is sequentially and periodically measured
and compared to a predetermined threshold voltage. In certain
embodiments, the steps of disconnecting and determining are
repeated for the second selected capacitor after the time to
discharge the first selected capacitor is determined. Certain
embodiments also comprise the step of calculating leakage values
for the first and second capacitors based on the respective times
required to discharge the first and second selected capacitors by
the predetermined amount.
[0038] Certain embodiments of the invention provide systems for
measuring capacitor leakage comprising a plurality of charging
switches, each charging switch controlling connection of one of a
plurality of capacitors to a charging source, a plurality of
sensing switches, each sensing switch controlling connection of one
of the plurality of capacitors to a voltage sensing device, a
controller operative to control the plurality of charging switches
and the plurality of sensing switches wherein the controller is
configured to cause all of the plurality of capacitors to be
charged and soaked simultaneously, connect selected ones of the
plurality of capacitors to the voltage sensing device according to
a programmed sequence, and for each step in the programmed
sequence, provide a measurement of voltage on a capacitor currently
connected to the sensing device, and a computing device programmed
to determine leakage values for each of the plurality of capacitors
based on a measurement of time required for the voltage on the each
capacitor to reach a threshold value after the each capacitor is
disconnected from the charging source. In certain embodiments, the
plurality of charging switches is provided by a switch matrix. In
certain embodiments, the plurality of sensing switches is provided
by a switch matrix. In certain embodiments, the plurality of
charging switches and the plurality of sensing switches are
provided by a switch matrix. In certain embodiments, all capacitors
of the plurality of capacitors are simultaneously disconnected from
the charging source. In certain embodiments, the controller is
further configured to connect each of the plurality of capacitors
to the sensing device periodically. In certain embodiments, the
controller is further configured to disconnect each of the
plurality of capacitors from the sensing device sequentially.
[0039] Certain embodiments of the invention provide methods for
measuring capacitor leakage comprising providing a charging current
to a plurality of capacitors, wherein the charging current charges
and soaks the plurality of capacitors, sequentially connecting each
of the plurality of capacitors to a voltage sensing device,
monitoring voltage of the each capacitor to determine time elapsed
until the monitored voltage reaches a predetermined threshold
value, calculating leakage values for the plurality of capacitors
based on the time elapsed for each capacitor, wherein monitoring of
each capacitor commences after the each capacitor is disconnected
from the charging current. In certain embodiments, all of the
plurality of capacitors are disconnected from the charging current
simultaneously and wherein each capacitor is periodically monitored
in isolation from the other capacitors. Certain embodiments also
comprise at least one other voltage sensing device, wherein the
voltage of two or more capacitors are measured simultaneously.
[0040] Certain embodiments of the invention provide a method for
measuring capacitor leakage comprising charging one or more
capacitors with a charging source, removing the charging source
from the one or more capacitors, monitoring the voltage of the one
or more capacitors, and calculating capacitor leakage.
[0041] Certain embodiments of the invention provide a computer
readable medium encoded with data and instructions for calculating
capacitor leakage, the data and instructions causing an apparatus
executing the instructions to utilize a charging source to charge
one or more capacitors, remove the charging source from the one or
more capacitors, monitor voltage of the one of more capacitors, and
calculate capacitor leakage. Some of the embodiments further
comprise soaking the capacitors. Certain of the embodiments further
comprise charging one or more capacitors with a voltage source and
removing the voltage source from the one or more capacitors.
Certain of the embodiments further comprise charging one or more
capacitors with a current source and removing the voltage source
from the one or more capacitors. Certain of the embodiments further
comprise monitoring the voltage of the one or more capacitors after
removing the charging source. Certain of the embodiments further
comprise monitoring the voltage of the one or more capacitors
before and after removing the charging source. Certain of the
embodiments further comprise charging one or more capacitors
through a small valued series resistor. Certain of the embodiments
further comprise removal of the charging source using a switch.
Certain of the embodiments further comprise removal of the charging
source from a plurality of capacitors using a plurality of
switches. Certain of the embodiments further comprise calculating
capacitor leakage by monitoring the capacitor's discharge time,
monitoring the capacitor's change in voltage, and calculating the
capacitor's leakage using the equation I=Cdv/dt.
[0042] Certain of the embodiments further comprise receiving a
capacitor list. Certain of the embodiments further comprise
inputting the capacitance of one or more capacitors. Certain of the
embodiments further comprise analytically determining the
capacitance of one or more capacitors. Certain of the embodiments
further comprise measuring leakage of one of a plurality of
capacitors while holding the other capacitors at the charging
voltage. Certain of the embodiments further comprise sequentially
measuring leakage of individual capacitors within a plurality of
capacitors. Certain of the embodiments further comprise
simultaneously disconnecting a plurality of capacitors from a
charging source, and measuring the voltage of each capacitor until
it reaches a predetermined threshold level.
[0043] Certain embodiments of the invention provide a system for
measuring capacitor leakage comprising a communications/control
processor, a charging source, a sensing electronic component, a
capacitor or plurality of capacitors from which capacitor leakage
measurements are desired, and a switch matrix operable to
substantially simultaneously connect to a plurality of capacitors.
Certain of the embodiments further comprise a personal computer
operatively connected to the communications/control processor.
[0044] Although the present invention has been described with
reference to specific exemplary embodiments, it will be evident to
one of ordinary skill in the art that various modifications and
changes may be made to these embodiments without departing from the
broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative
rather than a restrictive sense.
[0045] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes can be made in form and detail without
departing from the spirit and scope of the present invention.
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