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Microelectromechanical Systems and Microstructures in Aerospace 349

(excluding government laboratories such as Sandia National Laboratory) have been
developed to produce MEMS solely for commercial and terrestrial applications.
This chapter will emphasize the noncommercial high volume environment and
assumes that production runs will be an iterative process using prototypes and
small wafer runs. Therefore, the focus will be on custom and prototype activity.

16.1.2 TAILORING OF TEST PLANS
As a small volume, custom-type activity, test plans are expected to modify or supple-
ment standard test plans. These tailoring activities should have the following attri-
butes:

. It should be a standard methodology — not necessarily a standard test.
. It should be concurrent with other engineering activities — not a final pass or
fail gate.
. It should be easily applicable to a given design — rather than being a standard
test.
. It should be easily portable across processes — not requiring reinitialization
of all steps taken to date.
. It should be quick and inexpensive — not requiring months of the design
process and tens of thousands of dollars.
. It should be based on understanding of reliability — not the lack of it.
. It should be based on all data sources — not just a single qualification
test.

An example of reliability testing that uses the above principles is product
testing at Analog Devices, Inc. A series of mechanical tests confirm resistance to
mechanical shock, stiction, and other MEMS-specific failure modes. These
3
reliability tests can be applied at the technology, component, or system level, but
all fundamentally depend on the interactions of MEMS parts at their most
basic level. The test conditions used in these reliability tests use MIL-STD-883
(‘‘Test Methods for Microcircuits’’) as the base. MIL-STD-883 is a widely used and
accepted document for prescribing test methodology. These MIL-STD-883 tests
include:

. High-temperature operating life (HTOL at condition C)
. Temperature cycle (condition C)
. Thermal shock (condition C)
. High temperature storage (condition C)
. Mechanical stress sequence (group D, subgroup 4).

In addition, analog devices developed stress tests called ‘‘random drop’’ and
‘‘mechanical drop.’’ Random drop is the random-orientation batch drop of pack-
aged devices from a height of 1.2 m onto a marble surface. The drop is repeated
about 10 times, and a basic functionality check is done between each drop. In the
mechanical drop test, devices are dropped one by one from a height of 0.3 m onto a
marble surface, first in the X-axis, then the Y-axis, and finally the Z-axis. An
electrical screen is performed, and the same procedure repeated from a height of

© 2006 by Taylor & Francis Group, LLC