U.S. patent application number 12/606788 was filed with the patent office on 2010-02-18 for voltage fault detection and protection.
This patent application is currently assigned to FORMFACTOR, INC.. Invention is credited to Bruce J. Barbara, Charles A. Miller.
Application Number | 20100039739 12/606788 |
Document ID | / |
Family ID | 37024398 |
Filed Date | 2010-02-18 |
United States Patent
Application |
20100039739 |
Kind Code |
A1 |
Barbara; Bruce J. ; et
al. |
February 18, 2010 |
VOLTAGE FAULT DETECTION AND PROTECTION
Abstract
A fault detection and protection circuit can include a comparing
circuit (e.g., a comparator or a detector) that can be connected to
a power line supplying power to an electronic device being tested.
The comparing circuit can be configured to detect a fault in which
the power line is shorted to ground. For example, the electronic
device being tested may have a fault in which its power terminals
are shorted to ground. Upon detection of such a fault, the
comparing circuit activates one or more switches that shunt
capacitors or other energy storage devices on the power line to
ground. The comparing circuit may alternatively or in addition
activate one or more switches that disconnect the power supply
supplying power to the electronic device under test from probes
contacting the electronic device.
Inventors: |
Barbara; Bruce J.;
(Discovery Bay, CA) ; Miller; Charles A.;
(Fremont, CA) |
Correspondence
Address: |
N. KENNETH BURRASTON;KIRTON & MCCONKIE
P.O. BOX 45120
SALT LAKE CITY
UT
84145-0120
US
|
Assignee: |
FORMFACTOR, INC.
|
Family ID: |
37024398 |
Appl. No.: |
12/606788 |
Filed: |
October 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11306186 |
Dec 19, 2005 |
7609080 |
|
|
12606788 |
|
|
|
|
60594248 |
Mar 22, 2005 |
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Current U.S.
Class: |
361/54 |
Current CPC
Class: |
G01R 1/36 20130101; G01R
31/2889 20130101 |
Class at
Publication: |
361/54 |
International
Class: |
H02H 9/00 20060101
H02H009/00 |
Claims
1. A method of detecting and responding to a fault in a
semiconductor device under test, the method comprising: monitoring
at least one electrical characteristic of a power line electrically
connected to the semiconductor device under test for indications of
the fault; determining from the at least one electrical
characteristic whether a fault condition exists; and in response to
determining the fault condition exists, diverting power from a
probe in electrical connection with a terminal of the semiconductor
device under test affected by the fault, wherein the diverting
occurs in close proximity to the probe in relation to a power
supply supplying power to the power line.
2. The method of claim 1 further comprising providing a capacitor
electrically connected to the power line.
3. The method of claim 2, wherein the diverting comprises at least
one of disconnecting the probe from the capacitor, disconnecting
the probe from the power supply, or connecting the probe to
ground.
4. The method of claim 3, wherein the diverting comprises
disconnecting the probe from the capacitor.
5. The method of claim 3, wherein the diverting comprises
disconnecting the probe from the power supply.
6. The method of claim 3, wherein the diverting comprises
disconnecting the probe from the capacitor and disconnecting the
probe from the power supply.
7. The method of claim 3, wherein the diverting comprises
connecting the probe to ground.
8. The method of claim 3, wherein: the probe is one of a plurality
of probes of a probe card assembly configured to contact a
plurality of terminals of the semiconductor device, and the
monitoring comprises monitoring a portion of the power line
disposed on the probe card assembly.
9. The method of claim 8, wherein the determining comprises
comparing a voltage on the power line to a reference voltage.
10. The method of claim 9, wherein the fault is a short to
ground.
11. The method of claim 1 further comprising testing the electronic
device.
12. The method of claim 1, wherein the monitoring comprising
monitoring a voltage on the power line.
13. The method of claim 1, wherein the power supply is connected to
a first end of the power line and the probe is connected to a
second end of the power line, and the monitoring comprises
monitoring a voltage on the power line at a location on the power
line that is in close proximity to the probe relative to the power
supply.
14. The method of claim 1, wherein the monitoring comprises
monitoring the at least one electrical characteristic at a
plurality of locations on a power plane, wherein the power plane is
electrically connected through the power line to a power supply,
and a plurality of probes are electrically connected to the power
plane and disposed to contact a plurality of terminals of a
plurality of electronic devices.
15. The method of claim 14, wherein the monitoring further
comprises determining whether a difference in voltages between at
least one pair of locations on the power plane exceeds a
predetermined threshold.
16-44. (canceled)
Description
BACKGROUND
[0001] FIG. 1A illustrates a simplified diagram of an exemplary
test system 100 for testing an electronic device 110. Tester 102
generates test data, which is written through communications link
106 to interface apparatus 108, which provides connections (not
shown) to probes 112 that, as shown in FIG. 1A, contact terminals
114 of the electronic device 110 under test. Response data
generated by the electronic device 110 returns to the tester 102
through probes 112, interface apparatus 108, and communication link
106. The communications link 106, interface apparatus 108, and
probes 112 thus provide a plurality of communications channels
between the tester 102 and the electronic device 110 under test. Of
course, other devices may be included in the system 100. For
example, devices for processing and/or routing test data and
response data may be placed between the communications link 106 and
the interface apparatus 108.
[0002] The interface apparatus 108 can be a probe card apparatus,
for contacting an electronic device 110 under test. Typically,
power must be supplied to the electronic device 110. As shown in
FIG. 1A, the power supply 104 is part of the tester 102, and power
from the power supply 104 is supplied through one of the
communications channels formed by the communications link 106,
interface apparatus 108, and power probe 116 to the power terminal
118 of the electronic device 110.
[0003] FIG. 1B illustrates a schematic diagram of a single power
line 120 from the power supply 104 to the power terminal 118 of the
electronic device 110 being tested. Power line 120 represents one
communications channel from the tester 102 to the electronic device
being tested 110 and thus comprises a portion of the communications
link 106, the interface apparatus 108, and the power probe 116. As
shown in FIG. 1B, a by-pass capacitor 122 is often connected
between the power line 120 and ground 124 to filter noise on the
power line 120.
[0004] At times, the electronic device 110 being tested has a fault
in which power is shorted to ground in the electronic device 110.
Such a condition typically causes a large current surge from the
power supply 104. Even if power supply 104 can include over-current
protection that automatically shuts power supply 104 off upon
detection of such a fault, the over-current protection circuitry
(not shown) in the power supply 104 may be unable to turn the power
supply 104 off due to both the delay and inductance of the power
line 120 before a current surge travels down power line 120. If
sufficiently large, such a current surge can damage the interface
apparatus 108 or a power probe 116. In fact, probe 116 may be
particularly susceptible to such damage. Moreover, even if the
over-current protection circuitry (not shown) in power supply 104
is able to shut the power supply 104 off in time to prevent a
current surge, by-pass capacitor 122 is likely to discharge
rapidly, and the resulting current through power probe 116 may
damage the probe 116.
SUMMARY
[0005] In exemplary embodiments, a comparing circuit (e.g., a
comparator or a detector) can be connected to the power line
supplying power to an electronic device being tested. The comparing
circuit can be configured to detect a fault in which the power line
can be shorted to ground. For example, the electronic device being
tested may have a fault in which its power terminals are shorted to
ground. Upon detection of such a fault, the comparing circuit can
activate one or more switches that shunt to ground or disconnect
capacitors or other energy storage devices from probes contacting
the electronic device being tested. The comparing circuit may
alternatively or in addition activate one or more switches that
disconnect the power supply supplying power to the electronic
device from probes contacting the electronic device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A illustrates a simplified diagram of an exemplary
prior art test system.
[0007] FIG. 1B is a schematic diagram of a power line and by-pass
capacitor in the system of FIG. 1A.
[0008] FIG. 2 illustrates a schematic diagram of a power line and
by-pass capacitor that can include an exemplary fault detection and
protection circuit according to some embodiments of the
invention.
[0009] FIG. 3 shows a schematic diagram of the power line and
by-pass capacitor of FIG. 2 that can include another exemplary
fault detection and protection circuit according to some
embodiments of the invention.
[0010] FIG. 4 illustrates a schematic diagram of the power line and
by-pass capacitor of FIG. 2 with yet another exemplary fault
detection and protection circuit according to some embodiments of
the invention.
[0011] FIG. 5 illustrates a schematic diagram of the power line and
by-pass capacitor of FIG. 2 with still another exemplary fault
detection and protection circuit according to some embodiments of
the invention.
[0012] FIG. 6 illustrates an exemplary semiconductor wafer probing
system according to some embodiments of the invention.
[0013] FIG. 7 illustrates an exemplary probe card assembly
according to some embodiments of the invention.
[0014] FIG. 8 illustrates yet another exemplary fault detection and
protection circuit according to some embodiments of the
invention.
[0015] FIG. 9 illustrates an exemplary configuration of the
detector of FIG. 8 according to some embodiments of the
invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0016] This specification describes exemplary embodiments and
applications of the invention. The invention, however, is not
limited to these exemplary embodiments and applications or to the
manner in which the exemplary embodiments and applications operate
or are described herein.
[0017] FIG. 2 illustrates a schematic diagram of a power line 120
and by-pass capacitor 122 that can include an exemplary fault
detection and protection circuit according to some embodiments of
the invention. As described above, power line 120 can be a power
line from the power supply 104 of a tester 102 to a power terminal
118 of an electronic device 110 (shown in partial view only) being
tested. As also described above, by-pass capacitor 122 can be
connected between power line 120 and ground 124 and may function as
a noise filter for power line 120.
[0018] The exemplary fault detection and isolation circuit shown in
FIG. 2 can include a comparator 210 and three switches 252, 254,
256. To test electronic device 110, switch 252 can be closed, and
power line 120 consequently can be connected and provide power to
from power supply 104 to power terminal 118 of the electronic
device 110 being tested. Switch 256 can be closed, connecting
by-pass capacitor 122 to power line 120. Switch 254 can be left
open.
[0019] Comparator 210 can include two inputs 206, 208. One input
206 can be connected to the power line 120, preferably close to the
probe 116 (which can be at the end of the power line 120) as shown
in FIG. 2. The other input 208 can be connected to a reference
voltage (not shown). If a fault on the electronic device 110 shorts
power terminal 118 to ground, the voltage on the power line 120
will drop towards ground because of the fault. The reference
voltage applied to input 208 can be set to correspond to a low
voltage that represents such a fault in which power terminal 118 is
shorted to ground. The reference voltage applied to input 208 can
be selected in a variety of ways. For example, electronic device
110 may be designed to operate with a supplied power that is within
a specified voltage range. The reference voltage applied to input
208 can be selected to be below the minimum specified operating
voltage (i.e., the lower end of the specified power supply voltage)
of electronic device 110. For example, an electronic device 110 may
be designed to operate with a supplied power in the range of
approximately 3.5-5.0 volts. Assuming that such an electronic
device is supplied with a ground of zero volts, reference voltage
applied to input 208 can be selected to be below 3.5 volts, for
example, 3.0 volts. Higher or lower voltages can alternatively be
selected as the reference voltage applied to input 208 of
comparator 210.
[0020] The foregoing numerical examples are not limiting, and the
reference voltage applied to input 208 can depend on the particular
operating parameters of electronic device 110. The reference
voltage applied to input 208 can thus be selected to be any voltage
that, given the particular operating parameters of electronic
device 110, indicates a fault at a power terminal of electronic
device 110. Generally speaking, the closer the reference voltage is
to the operating range of the electronic device 110, the faster
comparator 210 can detect a fault.
[0021] If the voltage from power line 120 at input 206 of the
comparator 210 drops to the reference voltage applied to input 208,
the comparator 210 indicates such and the output 212 of comparator
210 can be used to open switches 252, 256 and closes switch 254.
Opening switch 252 disconnects probe 116 from power supply 104,
protecting probe 116 from a power surge from power supply 104 down
power line 120 caused by the fault at power terminal 118. Opening
switch 256 disconnects probe 116 from by-pass capacitor 122,
protecting probe 116 from a sudden discharge from by-pass capacitor
122 caused by the fault. Closing switch 254 creates a path to
ground 124. Thus, should a power surge from power supply 104
propagate past switch 252 before switch 252 can be opened, the
closing of switch 254 provides a path to ground 124 for the power
surge. The power surge can thus flow through switch 254 to ground
124, protecting probe 116. A power surge from power supply 104 can
propagate past switch 252 if, for example, the sum of the
propagation delay along power line 120 from probe 116 to power
supply 104 plus the propagation delay from power supply 104 to
switch 252 is less than the sum of the following delays: any
propagation delay along input 206 between power line 120 and
comparator 210, the processing delay of comparator 210, any
propagation delay along output 212 between comparator 210 and
switch 252, and the switching delay of switch 252.
[0022] The closing of switch 254 similarly creates a path to ground
124 for a discharge from by-pass capacitor 122 that propagates past
switch 256 before switch 256 is opened. The discharge will thus
flow through switch 254 to ground rather than through probe
116.
[0023] The comparator 210 and switches 252, 254, 256 can thus form
and function as a fault detection and protection circuit that
protects probe 116 from a power surge from power supply 104 and/or
a current discharge from by-pass capacitor 122 such as may occur
due to a fault in which power terminal 118 is shorted to ground.
According to other embodiments, the fault detection and protection
circuit shown in FIG. 2 need not include each of switches 252, 254,
256. Rather, the fault detection and protection circuit shown in
FIG. 2 can include only one of switches 252, 254, 256 or any
combination of two of those switches. FIG. 3 shows one non-limiting
example in which the fault detection and protection circuit can
include switch 254 but not switches 252, 256.
[0024] In FIG. 3, the fault detection and protection circuit can
include comparator 210 and switch 254. As discussed above, while
testing the electronic device 110, switch 254 can be open (i.e., in
position 316). As also discussed above, if the comparator 210
detects a voltage on power line 120 indicating a fault in which
power terminal 118 is shorted to ground as compared to a chosen
voltage reference applied to input 208, comparator 210 can activate
switch 254, causing switch 254 to move to closed position 319,
which creates a path through switch 254 to ground 124. This creates
a path to ground between power supply 104 and probe 116 and between
by-pass capacitor 122 and probe 116. A power surge from power
supply 104 and a discharge from by-pass capacitor 122 can thus flow
through switch 254 to ground 124, protecting probe 116.
[0025] As shown in FIGS. 2 and 3, connection 230 may be provided
between the tester 102 and the comparator 210. Such connection 230
may allow the tester to set and reset the comparator 210. Various
data (e.g., status data and/or handshaking data) may also be
exchanged between the comparator 210 and the tester 102 over
connection 230. For example, the comparator 210 may send
information regarding a detected fault to tester 102 through
connection 230. Such information provided from comparator 210
through connection 230 to tester 102 can include a signal or
signals that cause tester 102 to turn power supply 104 off. For
example, upon detecting a fault, comparator 210 can (in addition to
generating output signal 212 that opens switches 256, opens switch
252, and/or closes switch 254) generate a control signal or signals
that are sent to tester 102 via connection 230 indicating detection
of the fault and causing tester 102 to turn power supply 104
off.
[0026] FIG. 4 illustrates yet another configuration of a fault
detection and protection circuit according to some embodiments of
the invention. FIG. 4 includes a schematic diagram of power line
120 with a fault detection and protection circuit that can include
comparator 210, which can be connected to switch 214. In position
216, which can be the normal operating position of switch 214
during testing of the electronic device 110, power from power
supply 104 can be connected to the power probe 116. In position
219, which can be the position of switch 214 upon detection of a
fault, the probe 116 can be connected to ground 124 and
disconnected from the by-pass capacitor 122. Accordingly, the
charge from by-pass capacitor is generally prevented from
discharging into probe 116. The probe 116 can be also disconnected
from the power supply 104. The comparator 210 and switch 214 can
thus form a fault detection and protection circuit that protects
probe 116 from a current discharge from by-pass capacitor 122 such
as may occur due to a fault in which power terminal 118 is shorted
to ground. The probe 116 can be also disconnected (and thus
protected) from the power supply 104.
[0027] FIG. 5 illustrates still another configuration of a fault
detection and protection circuit according to some embodiments of
the invention. FIG. 5 includes a schematic diagram of power line
120 with a fault detection and protection circuit that can include
comparator 210, which can be connected to switch 414. While testing
the electronic device 110, switch 414 can be in position 416 and
forms part of power line 120. When activated by output 212 of
comparator 210 (as described above), switch 414 moves to position
419, which interrupts power line 120 and disconnects probe 116 from
the power supply 104. As can be seen in FIG. 5, while in position
419, switch 414 also disconnects by-pass capacitor 122 from probe
116, preventing by-pass capacitor 122 from discharging through
probe 116.
[0028] In any of the foregoing embodiments, the comparator 210 can
be a high speed voltage comparator (e.g., generating an output
within about 100 to 1000 picoseconds or even less than 100
picoseconds of a change at its inputs), such as are known in the
art. The comparator 210 may alternatively be a programmed
microcontroller or other logic hardware and/or software (including
without limitation firmware or microcode). Various types of
monitoring and reporting may thus be programmed into comparator
210. The switches 214, 252, 254, 256, 314, 414 may be implemented
using transistors (e.g., bi-polar transistors or field effect
transistors), silicon controlled rectifiers, or any other structure
suitable for opening and/or closing an electrically conductive
line. For example, many transistors configured in parallel may form
a switch 214, 252, 254, 256, 314, 414. Switches 214, 252, 254, 256,
314, 414 may alternatively be relays or any other suitable
electronic switching device. Comparator 210 and/or switches 214,
252, 254, 256, 314, 414 may be implemented on an integrated
circuit.
[0029] FIG. 6 illustrates an exemplary probing system 600 for
testing one or more electronic devices 610, which may be, for
example, one or more dies of a semiconductor wafer, one or more
singulated semiconductor dies of an array of dies, or any other
electronic device or devices. As will be seen, the exemplary fault
detection and protection circuits of FIGS. 2-5 may be implemented
on the probe card assembly 608 of the probing system 600.
[0030] As shown, the probing system 600 can include a tester 602,
which may be generally similar to tester 102 of FIG. 1A, and a
prober 609 with a moveable stage 626 for supporting electronic
device or devices 610 under test and for moving the electronic
device or devices 610 into contact with probes 612 of the probe
card assembly 608. A communications link 606, test head 650,
connectors 652, and probe card assembly 608 (which can include
probes 612) can provide a plurality of communications channels (not
shown) between the tester 602 and the semiconductor electronic
device or devices 610 under test. One or more of those
communications channels (not shown) may provide power from power
supply 604 to the dies (not shown) of the electronic device or
devices 610 under test.
[0031] The communications link 606 can provide a plurality of
separate communications connections (not shown) between the tester
602 and the test head 650. Communications link 606 may be any means
for communicating data and/power. (In some embodiments, power may
be supplied through electrical connections other than
communications link 606.) Non-limiting examples include a cable,
optical data links, wireless data links, etc. The test head 650 can
route the communications connections of link 606 to the connectors
652, which in turn can provide electrically conductive paths
between the test head 650 and the probe card assembly 608.
Connectors 652 may be any means for providing electrically
conductive paths between the test head 650 and the probe card
assembly 608. Non-limiting examples include pogo pins, cables or
wires with zero-insertion-force connectors, etc. The probe card
assembly 608 provides electrical paths (not shown in FIG. 6)
between the connectors 652 and the probes 612.
[0032] Probe card assembly 608 can be any type of apparatus having
probes for contacting dies (not shown) of a semiconductor
electronic device or devices 610. FIG. 7 shows a simplified block
and schematic diagram of one exemplary probe card assembly 608.
[0033] The probe card assembly 608 of FIG. 7 can include three
substrates: a printed circuit board 502, an interposer 504, and a
probe head 506. Terminals 508 electrically connect to connectors
652 of FIG. 6. Terminals 508 may be pads for receiving pogo pins
(if connectors 652 are pogo pins), zero-insertion-force connectors,
or any other connection device suitable for receiving connectors
652 of FIG. 6.
[0034] Electrical connections 510 (e.g., conductive vias and/or
traces) through the printed circuit board 502, spring contacts 512
electrically connecting printed circuit board 502 and interposer
504, electrical connections 514 (e.g., conductive vias and/or
traces) through interposer 504, spring contacts 516 electrically
connecting interposer 504 and probe head 506, and electrical
connections 518 (e.g., conductive vias and/or traces) through probe
head 506 can electrically connect connectors 508 to probes 612.
Probes 612 can be configured to contact terminals on the
semiconductor dies (not shown) of electronic device or devices 610.
Connectors 508, connections 510, spring contacts 512, connections
514, spring contacts 516, connections 518, and probes 612 can thus
form the electrical paths between connectors 652 of FIG. 6 and the
probes 612 of the probe card assembly 608 that contact the
electronic device or devices 610 under test.
[0035] The probe head 506 and interposer 504 may be secured to the
printed circuit board 502 using any suitable means (not shown),
including without limitation bolts, screws, clamps, brackets,
spring devices, etc. U.S. Pat. No. 5,974,622, U.S. Pat. No.
6,509,751, and U.S. patent application serial no. 11/165,833 (filed
Jun. 24, 2005) describe exemplary probe card apparatuses, and
various features of the probe card apparatuses described in those
patents may be implemented in probe card assembly 608.
[0036] The communications link 606, test head 650, connectors 652,
electrical paths (e.g., 510, 512, 514, 516, 518) through the probe
card assembly 608, and probes 612 can form the plurality of
communications channels mentioned above between the tester 602 and
the dies (not shown) of the electronic device or devices 610. As
also mentioned above, one or more of these communications channels
may be used to supply power from the power supply 604 to the dies
(not shown) of the electronic device or devices 610 during testing
of the dies. The power line 120 in FIGS. 2-5 may represent one such
communications channel used to supply power. (Power supply 104 in
FIGS. 2-5 would thus represent power supply 604 in FIG. 6, and
terminal 118 in FIGS. 2-5 would represent a power input terminal to
one of the dies (not shown) of the electronic device or devices 610
in FIG. 6.) The by-pass capacitor 122 of FIGS. 2-5 may be placed on
any or all of the substrates 502, 504, and/or 506 of the probe card
assembly 608 of FIG. 7. The comparator 210 and switches 214, 252,
254, 256, 314, 414 of FIGS. 2-5 may likewise be placed on any or
all of the substrates 502, 504, and/or 506. In some embodiments,
by-pass capacitors (like 122) can be advantageously placed as close
as possible or practical to probes 612 and therefore may be placed
on probe head 506. As is known, in some cases, the closer a by-pass
capacitor (e.g., like by-pass capacitor 122) is to a power input
(e.g., power terminal 118) of an electronic device (e.g.,
electronic device 110), the more effective the capacitor can be in
filtering noise on the power line out of the power signal provided
to the power input. By-pass capacitors (like 122) may be placed on
either side of the probe head 506, including the side 524 to which
the probes 612 are attached. The comparator 210 and switches 214,
252, 254, 256, 314, 414 of FIGS. 2-5 may likewise by placed on the
probe head 506 (on either side, including side 524). Input 206 of
the comparator 210 may be connected to connections 518 embedded
within 526 the probe head 506. The comparator 210 and switches 214,
252, 254, 256, 314, 414 may also be placed on one or more of the
printed circuit board 502 and/or interposer 504.
[0037] FIG. 8 illustrates yet another configuration of a fault
detection and protection circuit according to some embodiments of
the invention. As shown, like the configuration of FIG. 2, the
fault detection and protection circuit of FIG. 8 can include a
power line 120 for supplying power from a power supply 104. A
by-pass capacitor 122 can be connected to ground 124. The fault
detection and protection circuit of FIG. 8 can also include
switches 252, 254, and 256, which may be the same as and function
as like numbered switches in FIG. 2. Unlike the fault detection and
protection circuit of FIG. 2, however, the fault detection and
protection circuit of FIG. 8 includes a power plane 1204 that
distributes power from power line 120 through a plurality of probes
116 to a plurality of power terminals 118 of a plurality of
electronic devices 110 being tested. The configuration of FIG. 8
can also include detector 1206.
[0038] As shown in FIG. 8, the inputs 1208 of detector 1206 can be
electrically connected to different points on the power plane 1204.
(Although five inputs 1208 can be shown in FIG. 8, more or fewer
may be used.) Detector 1206 can be configured to activate output
1202 if a sufficiently large voltage difference is detected between
two or more of the inputs 1208, which can be an indication that one
or more of probes 116 is shorted to ground due to a short-to-ground
fault at one or more of power terminals 118. As discussed above,
electronic devices 110 are typically designed to operate with a
supply of power within a specified voltage range. A fault in which
a power terminal 118 is shorted to ground can short the probe 116
contacting the power plane 1204 to ground, which can cause a drop
in the voltage on the power plane 1204 in the general vicinity
where the shorted probe 116 is connected to the power plane 1204.
The amount of the voltage drop can depend on the operating
parameters of the electronic device 110 and the test system used to
test the electronic device 110. Thus, the voltage difference
detector 1206 is configured to detect can depend on the operating
parameters of the electronic device 110 and test system.
[0039] Upon detecting such a difference (i.e., representing a fault
at one of the power terminals 118), detector 1206 can activate
output 1202, which closes switch 254 and opens switches 252 and 256
as discussed above with respect to FIG. 2. (Also as discussed above
with respect to FIG. 2, the normal operating positions of switches
252, 254, 256 during testing of electronic devices 110 can be as
follows: switch 252 can be closed, switch 254 can be open, and
switch 256 can be closed.) As discussed above with respect to FIG.
2, closing switch 254 can provide a path to ground 124 for a
current surge from power supply 104 and/or for a discharge from
by-pass capacitor 122, diverting such a current surge from power
supply 104 and a discharge from by-pass capacitor 122 away from
probes 116. Opening switch 252 disconnects probes 116 from power
supply 104, and opening switch 256 disconnects probes 116 from
by-pass capacitor 122. As also discussed above with respect to FIG.
2, various configurations of the fault detection and protection
circuit of FIG. 8 may be implemented with only one of or only two
of switches 252, 254, 256.
[0040] FIG. 9, which shows a top view of power plane 1204,
illustrates an exemplary configuration of a detector, such as
detector 1206, according to some embodiments of the invention. As
shown, detector 1206 can comprise four differential amplifiers
1312, 1314, 1316, 1318 and a functional OR circuit 1328 configured
to detect a positive or negative output on one or more of
differential amplifier outputs 1320, 1322, 1324, 1326 active its
output 1202 in response thereto. As also shown, detector 1206 can
include five inputs, each tapped from five locations 1302, 1304,
1306, 1308, 1310, such as power plane 1204. One of the taps 1302,
1304, 1306, 1308, 1310 (in this example tap 1306) can be input to
each of differential amplifiers 1312, 1314, 1316, 1318. Each of the
other taps 1302, 1304, 1308, 1310 can become the other input to
differential amplifiers 1312, 1314, 1316, 1318. Each differential
amplifier 1312, 1314, 1316, 1318 can thus compare the voltage (or
current) at tap 1306 to the voltage (or current) at another of taps
1302, 1304, 1308, 1310. As shown in FIG. 9, a tap (e.g., tap 1306)
that is generally centrally located with respect to others of the
taps (e.g., 1302, 1304, 1308, 1310) may be selected as providing a
voltage to which voltages from the other taps can be compared.
Alternatively, any of taps 1302, 1304, 1306, 1308, 1310 may be
selected as providing a voltage to which voltages from the other
taps can be compared.
[0041] The voltage (or drawn current) should be generally the same
across plane 1204 unless, for example, there is a fault at one of
power terminals 118 (see FIG. 8) as discussed above. Each
differential amplifier 1312, 1314, 1316, 1318 can activate its
output 1320, 1322, 1324, 1326 if the voltage (or drawn current)
difference at its inputs exceeds a predetermined threshold, which
as discussed above, indicates a fault at one or more of terminals
118. As generally discussed above, the threshold can depend on the
operating parameters of electronic device 110 and the test system
used to test electronic device 110. The outputs 1320, 1322, 1324,
1326 of differential amplifiers 1312, 1314, 1316, 1318 can be
logically ORed together by circuit 1328 so that output 1202 of
detector 1206 is activated if any of the outputs 1320, 1322, 1324,
1326 of differential amplifiers 1312, 1314, 1316, 1318 is
activated.
[0042] For example, if a probe 116 connected to power plane 1204 in
the vicinity of one or more of taps 1302, 1304, 1308, 1310 contacts
a terminal 118 of an electronic device 110 with a short-to-ground
fault, the voltage on power plane 1204 at the one or more of taps
1302, 1304, 1308, 1310 can fall below the voltage at tap 1306, and
one or more of differential amplifiers 1312, 1314, 1316, 1318 can
generate a positive pulse on its or their outputs 1320, 1322, 1324,
1326. If a probe 116 connected to power plane 1204 in the vicinity
of tap 1306 contacts a terminal 118 of an electronic device 110
with a short-to-ground fault, the voltage on power plane 1204 at
tap 1306 can fall below the voltage on power plane 1204 at taps
1302, 1304, 1308, 1310, and each of differential amplifiers 1312,
1314, 1316, 1318 can generate a negative pulse on outputs 1320,
1322, 1324, 1326. Although five taps 1302, 1304, 1306, 1308, 1310,
four differential amplifiers 1312, 1314, 1316, 1318, and one OR
gate 1328 are shown in FIG. 9, more or fewer taps, differential
amplifiers, and/or OR gates may be used. Moreover, multiple
detectors 1206 configured as shown in FIG. 9 can be connected to
power plane 1204.
[0043] The exemplary fault detection and protection circuit shown
in FIGS. 8 and 9 may be implemented on a probe card assembly like
probe card assembly 608 of FIG. 7. For example, power plane 1204
may be embedded in probe substrate 506, and probes 116 may be
implemented like probes 612 of FIG. 7. Any one or more of switches
252, 254, 256, detector 1206 (including one or more of differential
amplifiers 1312, 1314, 1316, 1318 and/or OR gate 1328) may be
disposed on or embedded in any of printed circuit board 502,
interposer 504, and/or probe substrate 506.
[0044] In any of the foregoing embodiments, the comparator 210 and
differential amplifiers 1312, 1314, 1316, 1318 can be high speed
voltage comparators or differential amplifiers (e.g., generating an
output within about 100 to 1000 picoseconds or even less than 100
picoseconds of a change at its inputs), such as are known in the
art. Comparator 210 or differential amplifiers 1312, 1314, 1316,
1318 may alternatively be a programmed microcontroller or other
logic hardware and/or software (including without limitation
firmware or microcode). Various monitoring and reporting may thus
be programmed into comparator 210 and/or any of differential
amplifiers 1312, 1314, 1316, 138. The switches 214, 252, 254, 256,
314, 414 can be implemented using transistors (e.g., bi-polar
transistors or field effect transistors), silicon controlled
rectifiers, or any other structure suitable for opening and/or
closing an electrically conductive line. For example, many
transistors configured in parallel may form a switch 214, 252, 254,
256, 314, 414. Switches 214, 252, 254, 256, 314, 414 may
alternatively be relays or any other suitable electronic switching
device. Comparator 210, differential amplifiers 1312, 1314, 1316,
138 and/or switches 214, 252, 254, 256, 314, 414 may be implemented
on one or more integrated circuits.
[0045] As generally discussed above with respect to FIG. 2, in any
of the embodiments described herein, tester 102 can provide control
signals through connection 230 to comparator 210 or detector 1206
(e.g., setting parameters of comparator 210 or detector 1206,
resetting comparator 210 or detector 1206, etc.) and can receive
status and/or other signals from comparator 210 or detector 1206.
Moreover, comparator 210 or detector 1206 can provide information
to tester 102 regarding a detected fault, and such information can
include a signal or signals that cause tester 102 to turn power
supply 104 off. For example, upon detecting a fault, comparator 210
or detector 1206 can (in addition to generating output signal 212
or 1202 that opens or closes one or more of switches 252, 254, 256,
414) generate a control signal or signals that are sent to tester
102 via connection 230 indicating detection of the fault and
causing tester 102 to turn power supply 104 off.
[0046] Various exemplary embodiments and applications of the
invention have been presented and described. Many variations and
modifications and alternative embodiments and applications are
possible. For example, the comparator 210 and switches 214, 252,
254, 256, 314, 414 may be configured to shunt to ground or to
disconnect from power line 120 energy storage devices other than
capacitors 122. As another example, the fault detection and
protection circuit (comprising the comparator 210 and switches 214,
252, 254, 256, 314, 414) may be implemented in a system other than
the semiconductor probing system 600 shown in FIG. 6. For example,
the fault detection and protection circuit of FIG. 2-5 may be
implemented in another type or configuration of a probing system,
or the fault detection and protection circuit may be implemented in
another type of testing system, such as the more generalized test
system shown in FIG. 1A. As yet another example, the power supply
104 of FIG. 1A or 604 of FIG. 6 need not be located in the tester
102, 602 but may be placed in any location.
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