Evaluation of adhesion promoters for Parylene C on gold metallization

Abstract

Delamination of thin film polymeric coatings from metallization layers is a common cause of failure in biomedical implants. To address the problem, different adhesion promotion techniques can be applied which include surface pre-treatment with oxygen and argon plasma and the use of different adhesion promoters. In this paper the applicability of titanium (Ti), silicon oxide (SiOx), diamond-like carbon (DLC), tetramethylsilane (TMS) and aluminium oxide (AlOx) as adhesion promoters is evaluated. A cross cut, peel and scratch test are used to qualify and quantify the adhesion before and after storage in phosphate buffered saline (PBS) for 48 hours at a temperature of 37 °C. Promising results could be achieved by a combination of Ti and DLC as well as by AlOx.

The Effect of Reactive Sputtering on the Microstructure of Parylene-C

“…Since the SEM results showed a diminishing delamination result of the parylene-C/AlN bilayers with respect to sputtering time, a scratch-resistant test measurement was conducted on the bilayers on a glass substrate to ascertain the adhesion properties of the films. The scratch test is one of the acceptable methods for measuring the adhesion properties of different coatings [ 7 , 26 ]. During its operation, a scratch is drawn across the surface of the film with a simultaneously constant or progressively applied load.…”

“…Parylene films generally have poor adhesion to cold surfaces due to the lack of bonding between the surface and parylene film, a problem that is detrimental to surfaces coated with parylene for protection, biocompatibility, enhancing light extraction, etc. Over the years, this problem has been solved through either the application of adhesion promoters onto the substrate’s surface before parylene deposition and/or post-thermal treatment of parylene using plasma or annealing processes, to ensure strong adhesion [ 7 , 8 , 9 ]. The use of the plasma post-treatment technique on parylene has become more popular due to its ability to remove contaminating substances and tailor the wettability and adhesion properties of the surface [ 2 , 9 ].…”

Achieving long-term stability of thin-film electrodes for neurostimulation

“…Delamination is reported as one of the most frequent failure mechanisms of thin-film electrodes, whereby two layers (insulation-metallisation or metallisation-electrode coating) separate from one another [49,135,147]. Delamination can occur because of water intrusion at the interface, which leads to a change in adhesion due to the weakening of polar attractions and/or mechanical interlocking.…”

“…With the development of novel biomaterials and coatings, tests are needed to evaluate their longterm adhesion stability. This is partially addressed by methods such as the crosscut test and peel test, which can be performed in vitro pre-implantation [135,147,183,184]. The former involves artificially cutting the electrodes and applying an adhesion force to evaluate the extent of delamination.…”

Techniques and Considerations in the Microfabrication of Parylene C Microelectromechanical Systems

“…Reports suggest that annealing increases the entanglement of the polymer chains while reducing stress by recrystallization of Parylene-Parylene interfaces [ 57 , 75 ]. Interposer layers have also been investigated to either modify the surface energy of a coated material, thereby improving chemical adhesion, or to create a barrier against water vapor, minimizing water intrusion and subsequent failure [ 76 , 77 , 78 ]. Plasma-enhanced Parylene is a method to improve adhesion of Parylene to other surfaces by cleaning and modifying the film within the process chamber [ 79 ].…”