(Georgia Institute of Technology, 1999-07)
Wong, C. P.; Wu, Jiali; Pike, Randy T.
A flexible, smooth, and low profile conformal coating
was developed to accomplish the encapsulation of a microelectromechanical
system (MEMS) device that will be applied to
sense the static pressure on aircraft during real flight testing.
The encapsulant should be able to protect the MEMS device
and the multichip module (MCM) from adverse environmental
conditions, i.e., mechanical shock, temperature fluctuation, engine
fuel and oil contamination, and moisture/mobile ion permeation.
Presently, conventional packaging schemes for electronics cannot
satisfy this specific outdoor application, and a new encapsulation
combination has been designed in accord with the requirement
of reliability without hermeticity (RWOH). A bi-layer structure
was selected because of property limitations of a single material.
Pliable elastomeric silicones, are typically flexible, water repellant,
and abrasion resistant. The silicone encapsulant will be first
applied to planarize the MEMS surface and function as durable
dielectric insulation, stress-relief, and shock/vibration absorbers
over a wide humidity/temperature range. To compensate for the
deficiency of silicone on engine fuel/oil contamination, Parylene
C is to be deposited afterward. This bi-layer coating can achieve
excellent bulk properties, such as moisture and mobile ion barrier
resistance, chemical compatibility, and electrical insulation characteristics.
However, the poor adhesion of Parylene C to silicone
greatly restricts its application. To address this problem, silane
coupling agents were used as an adhesion promoter. Significant
adhesion im provement was achieved by placing an interlayer
silane coupling agent to provide interfacial bonding to the silicone
elastomeric surface and the Parylene C film. Furthermore, a possible
mechanism of adhesion enhancement will also be presented
in this study.
Index Terms— Bi-layer conformal coating, micro-electromechanical
system (MEMS), multichip module, Parylene C,
reliability without hermeticity (RWOH), silane coupling agent,
silicone elastomer.
(Georgia Institute of Technology, 1998-10)
Wong, C. P.; Wu, Jiali; Pike, Randy T.
Large area substrate processing is a key solution
for improving the productivity of multichip module deposition
(MCM-D) technology. This project is focused on high temperature
polymeric adhesives for attachment of silicon tiles to suitable
pallets to facilitate large area film processing of MCM structures.
Current polymeric high temperature adhesives are predominately
polyimide-based that are not reworkable, which places an obstacle
to remove the coated substrates and to reuse the high
cost pallets. However, an approach will be presented in this
paper to address this demand by introducing thermally cleavable
links in the thermoset polyimide-amide resin. A series of novel
reworkable high temperature (in excess of 350–400 ℃) adhesives
have been developed, that can meet the requirements of adhesion,
viscosity, thermal stability, and reworkability of the MCM-D
production. Furthermore, scanning electron microscopy (SEM)
microstructure images are presented for intuitive reworkability
analysis.