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- QA Technology's standard test
probes are lubricated to increase their
life. The lubricant drastically reduces
the normal wear from the sliding metal-to-metal
contact within the probe.
Sixteen pieces of QA Technology
part number 100-PRP2544H (standard,
lubricated probes) and sixteen identical
probes without lubrication were run
side-by-side on the contact test system
for 250,000 cycles. Resistance measurements
were made each 2,000 cycles, and stroke
measurements each 5,000 cycles.
There are significant performance differences between lubricated and unlubricated probes:
Unlubricated probes had electrical resistance
greater than 50 milliohms (considered
a failure) as early as 8,000 cycles.
Three probes out of sixteen had failed
sby 30,000 cycles.
The lubricated probes were tested
to 250,000 cycles with no measurements
greater than 24 milliohms. The test
was stopped at this point due to the
condition of the unlubricated probes.
Lubricated probes are routinely tested
to one million cycles with electrical
resistance below 50 milliohms.
Wear of the unlubricated probes generated
a considerable amount of filings.
The black wear particles were not
only evident on the plunger shanks,
but also formed piles around the socket
bases. This wear not only results
in electrical failure, but the particles
also cause stick down failures. By
the end of the test, six out of the
sixteen unlubricated probes (38%)
exhibited stroke failures, the earliest
at 40,000 cycles.
There is a significant increase in
the amount of force required to compress
an unlubricated probe. This observation
is based on the relative condition
of the contact platen after the test.
The contacts made by lubricated probes
were almost unnoticeable, but the
platen had obvious indents and damage
from the crown points of the unlubricated
probes. This is probably not an issue
on solder pads for single board tests,
but may damage gold or otherwise delicate
contact surfaces. More important,
the increased force may cause fixture
actuation problems
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