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294 MEMS and Microstructures in Aerospace Applications

inert gas, dry air, or dry nitrogen. The temperature range should be 18 to 248C
with a relative humidity (RH) range well below 30% and an air cleanliness of Class
1000 per FED-STD-209. All materials shall be electrostatic discharge control
(ESD) protective and specifically chosen to preclude ESD damage to the devices.
In addition any special instructions should be included but not limited to:

. Die attaches, material, and properties
. Bond wire size and down bonds (pad number and electrical potential)
. Bonding method (e.g., thermo compression, thermo sonic, ultrasonic,
etc.)
. Descriptions of any other unique materials or exposed surfaces that may
require special protection during assembly
. Suggested limitations on handling methods, or die-attach pressures
. Suggested wire bonding sequence, quantity of bond wires on power and
ground pins, and stitch bond (connection) requirements between ground pins
. Suggested lid sealing material and sealing procedure
. Packaged component ESD sensitivity
. Environmental conditions necessary to ensure long-term die reliability (e.g.,
special sealing)
. Maximum recommended allowable peak die assembly process temperatures
or times
. Dimensional data (for features of top metal and mask layers) in a backside
surface roughness finish type, etc.
. Environmental conditions and storage duration prior to shipment
. Unusual die material properties (e.g., SiC backside coatings)
. Moisture resistance data (for nonhermetic applications) based upon acceler-
ated stress studies (e.g., 85% RH — 858C, highly accelerated stress testing,
autoclave, etc.) of existing nonhermetic packaged product
. Recommended die coat material, thickness, and application process as
required.

13.5 ELECTROSTATIC DISCHARGE CONTROL
If not handled properly, several elements used in MEMS can be damaged by ESD.
Therefore, every process and design should be characterized to determine ESD
sensitivity. Regardless of these results, all MEMS devices should be treated as
sensitive to ESD damage. An ESD handling and training program is essential to
maintain a low level of ESD-attributed failures.
Inspection, test, and packaging of MEMS should be carried out in a static-free
environment to assure that delivered products are free of damage. Devices should be
packaged in conductive carriers and delivered in static-free bags. All handling and
inspection should be performed in areas meeting ‘‘Class 1’’ handling requirements.
Both the manufacturer and the user share the responsibility of assuring that an
adequate procedure is in place for protection against ESD.

© 2006 by Taylor & Francis Group, LLC