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Commercial Laboratory Equipment
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instrument or in a software program. These methods make a great deal of
sense when the volume of the product is low, since accomplishing BIT
requires some software (SW) or firmware (FW) development and attention
to circuit board layout. The layout requires test pads and the addition of
components to the design to increase the test coverage.
There are several methods and types of ICT. The most common are
boundary scan, flying probe, and full fixture, bed-of-nails ICT. Flying probe
testers pin down on component leads, PC board traces, and test pads
provided on the circuit board. This is the least expensive form of ICT in
terms of fixture cost. Flying probe testing is much slower than a bed-of-nails
test method and is usually used during prototype builds and for very-lowvolume products. Boundary scan testing is used most effectively for digital
designs. The components have to be selected for the capability to support
boundary scan during design. A test connector or test pads on the circuit
board provide test access. The test process can be run from a computer
through a vendor’s boundary scan module or accessed from the flying
probe and bed-of-nails testers. ICT will usually require a ‘‘bed-of-nails’’ type
fixture that may cost from US$20K to $30K. This fixture will need to be
modified with each board modification, and it may need to be replaced if
the board layout changes too much. For the high-mix, low-volume market,
a major concern for Keithley is the initial investment cost. If you assume a
US$50 savings per unit, as an example, it requires 600 units to break even;
for products that might ship only a 100 per year, it does not make sense to
incorporate ICT. BIT may be a better choice. As a result, Keithley carefully
examines when to use BIT and when to use ICT; other factors, such as
quality, help determine the decision for Keithley.
6.9.10
Maintenance and Repair
Keithley has centers around the world for repairing and maintaining their
products. These centers are particularly important for feeding back information to Keithley’s engineers on newly introduced products. Other, moreestablished products can have regional dependencies that determine how
they are repaired and maintained. In some cases, calibration and repair are
contracted to third-party firms. For large customers with their own facilities,
Keithley provides the documentation and training so that the customer can
do the work themselves.
6.10
Tests
Keithley Instruments has a full range of development tests—informal,
formal, and laboratory. The more informal or lab bench tests include prototypes and breadboards, such as the two-sided PCBs milled out in short
order to try out ideas. The formal tests include both inspection and
peer review, promoted from within by the engineers. They also include