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Impact of Space Environmental Factors on Microtechnologies 75

situation. Due to long lead times, devices spend a minimum of 10% of the prelaunch
time span in the manufacture and test cycle; therefore, concerns about both handling
and storage are of particular interest to space programs (based on the experiences in
microelectronics). Board assembly and qualification take more than 20% of the
prelaunch period. Integration and test at the board level takes approximately 6 to 18
months. This includes mechanical assembly, functional testing, and environmental
exposure. Much time is spent in queuing for a mission. Factors such as budget
negotiation and availability of the launch facilities and vehicle also contribute to the
long time between program initiation and launch. It is not unusual for these time
frames between initial plan and design to launch to stretch from 7 to 12 years as
noted in Table 4.1. Proper handling control of MEMS devices during the prelaunch
period is essential to avoid the introduction of latent defects that may manifest
themselves in a postlaunch environment. Proper handling and storage require
precaution to preclude damage from electrostatic discharge (ESD) and contamin-
ation. Temperature through test and storage should be maintained at 25 + 58C and
humidity should be held at 50 + 10% RH. However, this requirement for ESD for
the electronics runs counter to handling and storage precautions for MEMS devices.
A chapter of this book is dedicated to handling and contamination control, and
special storage requirements, which may well be required for MEMS devices in
nonhermetic packaging.
Parts may degrade during the time between the manufacturing stage and the
launch of the vehicle. This degradation generally proceeds at a much slower rate for
nonoperating parts than for operating parts due to the lower stresses involved.
Special precautions must be taken regarding humidity. Parts stored in a humid
environment may degrade faster than operating parts that are kept dry by self-
heating during operation. Keeping the parts in a temperature controlled, inert
atmosphere can reduce the degradation that occurs during storage. Controls to
prevent contamination are integral to good handling and storage procedures.
Most civilian contractors, and military space centers handle all EEE parts as if
they were sensitive to ESD and have precautionary programs in place. These same
precautions must be extended to MEMS devices once the devices have been
singulated and released. NASA requirements for ESD control may be found in

TABLE 4.1
Time Span from Design Phase to Launch

Project Initial Plan and Design Launch Duration (years)
TRMM 1985 1997 12
GRO or EGRET 1980 1991 11
COBE 1978 1989 11
ISTP 1985 1992–1993 8
TDRSS 1976 1983 7

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