Page 178 - Handbook of Adhesion Promoters

8.26 Poly(p-xylylene) 171

8.26 POLY(P-XYLYLENE)

Parylene C adhesion for microelectromechanical systems (silicon, silicon nitride, and sili-
1
con dioxide substrates) was improved by potassium hydroxide wet etching. A liquid
phase silanization on both sides of the wafer resulted in an improvement of the adhesion
1
of the Parylene layer.
A silane-based adhesion promoter (3-trimethoxysilylpropyl) suitable for a multi-
dielectric-layer coating on a digital microfluidic chip improved in chip lifetime by more
than 100 times via transforming the bonding of the dielectric layers (Ta O and Parylene
5
2
2
C) from nonspecific to chemical (see Figure 2.25).
Organic coatings are used in the aerospace industry as corrosion protective coatings
3
or primers in improving the adhesive bond in structural adhesive joints. The high strength
of the adhesive bond can be related to the formation of covalent bonds between the amino
groups of poly(o-amino-p-xylylene-co-p-xylylene) and the epoxy groups of the adhesive
3
during curing. The side-groups of substituted poly(p-xylylene) (such as amino, chlorine,
etc.) may offer direct attachment points for other coatings. 3
Parylene-C (poly-chloro-p-xylylene) is used in an implantable, microfabricated
4
devices because it has a low dielectric constant and superb biocompatibility. In many bio-
4
electrical applications, its poor wet adhesion is a serious shortcoming. An adhesion pro-
moter 3-trimethoxysilylpropylsilane was vaporized onto the wafer surface then Parylene-
4
C was polymerized by chemical vapor polymerization.
REFERENCES
1 Charmet, J; Bitterli, J; Sereda, O; Liley, M; Renaud, P; Keppner, H, J. Microelectromech. Systems,
22, 4, 855-64, 2013.
2 Gao, J; Chen, T; Dong, C; Jia, Y; Mak, P-I; Vai, M-I; Martins, RP, RCS Adv., 5, 48626-30, 2015.
3 Fundeanu, I; Klee, Kwakernaak, A; Poulis, JA, Int. J. Adh. Adh., 30, 2, 111-6, 2010.
4 Seymour, JP; Elkasabi, YM; Chen, H-Y; Lahann, J; Kipke, DR, Biomaterials, 30, 31, 6158-67, 2009.