Page 203 - Handbook of Adhesion Promoters

196 Selection of Adhesion Promoters for Different

9.15 ELECTRONICS

Electronics is one of the main applications of adhesive promoters. The following commer-
cial products are proposed for these applications: Bomar BR-970BT & BR-742S,
Chartwell B-515.1, B-515.1/2H, B-517.4, & C-515.72.HR, Dow Corning Z-6128, Dyna-
sylan 1189, Eastman CP, Silquest A-1871, and Sipomer PAM 100. Their main active com-
ponents are based on aliphatic & polyester urethane acrylates, chlorinated polyolefins,
phosphate esters of polyethylene glycol monomethacrylate, and amino-, carboxy-, epoxy-,
and vinyl-silanes.
Liquid crystal polymers and silicone adhesives are widely used in electronics manu-
1
facturing. Their adhesion is critical to the reliability of electronic products. The adhesion
1
is based on hydrogen bonds. The humidity significantly weakens the adhesion strength
1
because it interferes with hydrogen bonding. The weakened adhesion strength can be
1
recovered by removing the moisture from the interface.
In the resist lithography, polyallylamine was used as an effective adhesion promoter
2
between wafer and epoxy resin.
Polydopamine-functionalized graphene was used as a conductive adhesion promoter
3
and a protective layer for silver nanowire transparent electrodes with good results. Long-
3
term stability of optoelectronic devices was improved.
A silane-based adhesion promoter was found suitable for a multi-dielectric-layer
4
coating on a digital microfluidic chip. It improved a chip lifetime by more than 100 times
via transforming the bonding of the dielectric layers (Ta O and Parylene C) from nonspe-
2
5
4
4
cific to chemical. Figure 2.25 shows the mechanism of adhesion promotion.
The combination of an adhesion promoter (3-methacryloxypropyltrimethoxysilane)
and a thermal treatment improves the adhesion of Parylene to silicon substrates in produc-
5
tion microelectromechanical systems.
A poor adhesion of poly(3,4-ethylenedioxythiophene) to metallic substrates was
6
improved by the use of iridium oxide. Figure 8.6 shows the mechanism of adhesion
6
improvement.
Adhesion between copper and epoxy resin in a printed circuit board was improved
by deposition of an epoxy resin on copper modified by amine alkylthiol and dithiol mono-
7
layers. The chemical linkage between the amine self-assembled monolayer and the epoxy
function has been obtained by the deposition on a short epoxy fragment, the 2-(4-fluoro-
7
phenoxy-methyl)oxirane. The formation of chemical bonds such as Cu–S and N-epoxy
was essential for increasing the adhesion strength between copper and the polymer (mech-
7
anism explained in Figure 9.3).

Fig. 9.3. Scheme of the deposition of epoxy resin on copper modified by amine terminated thiol and dithiol self-
assembled monolayer. [Adapted, by permission, from Denayer, J; Delhalle, J; Mekhalif, Z, Appl. Surf. Sci., 257,
24, 10686-91, 2011.]