Title:
Evaluation and Characterization of Reliable Non-Hermetic Conformal Coatings for Microelectromechanical System (MEMS) Device Encapsulation
Evaluation and Characterization of Reliable Non-Hermetic Conformal Coatings for Microelectromechanical System (MEMS) Device Encapsulation
Author(s)
Wong, C. P.
Wu, Jiali
Pike, Randy T.
Kim, Namsoo P.
Tanielian, Minas H.
Wu, Jiali
Pike, Randy T.
Kim, Namsoo P.
Tanielian, Minas H.
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Abstract
The thrust of this project was to evaluate commercial
conformal encapsulation candidates for low cost aerospace applications.
The candidate conformal coatings evaluated in this study
included silicone elastomers, epoxies, and Parylenes with bi-layer
or tri-layer designs. Properties characterized in this study included
mobile ion permeation and moisture ingress resistance, interfacial
adhesion variation through thermal shock cycling and 85 C/85%
RH aging. Surface Insulation Resistance (SIR), Triple Track Resistance
(TTR) and die shear strength were used for the corresponding
electrical and physical property characterizations. Parylene
F displayed excellent properties for environmental protection.
Silicone elastomers displayed less resistance to the harsh environment
as compared to the Parylene family (N, C, D types), but it
could provide advantages for low residual stress applications. The
change in adhesion strength between Parylene C and silicone elastomers
after exposure to thermal shock cycling or 85 C/85%RH
aging for different time periods were conducted from die shear test
in terms of the interfacial failure. SIR values of all the candidate
materials after 1000 h exposure to 85 C/85%RH, with 100V dc for
resistance measurement, range from 1 108–1 109. Leakage
current values after 1000 h exposure to 85 C/85%RH, 175 V bias,
are in the range of 10 9 to 10 11 Amp. The bi- or tri-layer conformal
coating combination investigated in this study showed significant
promise for encapsulation of the microelectromechanical
system (MEMS) devices.
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Date Issued
2000-11
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