Evaluation Engineering - 19

Figure 4:
Several DUTs
connected to
the X-axis of a
crosspoint matrix.

Figure 5: DUT
connections via
three different
cable types.
(Courtesy of
Virginia Panel Corp.)

Board test with multi-up fixtures
With the IoT and the trend to increasingly
miniaturize electronic devices, PCBs are
also decreasing in size. Now it is often
not practical to individually manufacture-much less test-a 1-in.-square
PCB. Hence, such PCBs are assembled in
a panel, also called an array. These PCBs
are usually tested as a group as well. Once
testing is complete, the panel is broken up
and the good PCBs are sent on to the next
stage of the system assembly. Failed PCBs
are either scrapped or sent to rework.
In this case, a large matrix is ideal to
share resources between each DUT. In
Figure 4, you see several DUTs connected
to the X-axis of a crosspoint matrix. A
number of instruments are also connected to the X-axis. The colored lines show
a number of simultaneous instrument
connections. The number of connections
is limited by the number of Y-axis lines
available. Once measurements are made,
the matrix can reroute the instruments to
other DUTs and repeat the measurement
made earlier.

Board test with multiple
test programs
If you are in a repair-depot environment, or a company that has a highmix, low-volume manufacturing strategy, chances are your test system needs
to be very versatile to address multiple
DUT types on the same system. For
functional test, chances are that many

of your DUTs use the same connector
types. However, the signal requirement
on any given connector pin can be different depending on the function of a particular DUT.

(See Figure 5. Note the three different
cable connectors for DUT connections.)
This type of situation is where a
crosspoint matrix can make your test
system much more f lexible as it can
connect every test resource to any
DUT test point, rerouting resources
programmatically.

Bob Stasonis is a technical
product specialist at Pickering
Interfaces. He has contributed to and written numerous papers and articles on
the subject of electronic test. Over the last
40 years, Bob has held technical, sales, and
marketing positions with Teradyne, GenRad,
and Schlumberger. Bob is the president of the
PXI Systems Alliance as well as a past board
member of the LXI Consortium and past VP
of marketing for the American Society of Test
Engineers. bob.stasonis@pickeringtest.com

Conclusion

FOR FURTHER READING

There are many test strategies that depend on the type of test to be performed,
volume and mix of DUTs, and your budget. Clearly, no one test system can do it
all, at least not economically. But if you
have testing needs similar to what has
been described here, a crosspoint matrix may be an important part of your
test plans.

"Iddq testing," Wikipedia.
Rubin, Dave, "Short Pulse Testing Mandatory for
Semiconductor Reliability," Keithley Applications
Note, 2006.
"Pickering Interfaces LXI High-density Matrix
Modules Selected for Opens and Shorts Testing
of Semiconductor Packages," Pickering Interfaces
Knowledge Base.
SwitchMate, 2nd edition, Pickering Interfaces,
2019.

FEBRUARY 2020 EVALUATIONENGINEERING.COM

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Evaluation Engineering

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