Parylene combines mechanical characteristics that award it uniqueness as a uniform coating layer. Most types of parylene have a low Young’s Modulus and a high fracture elongation, mainly in type C parylene. A low Young’s Modulus is a desirable characteristic for coatings, since for low values of Young’s Modulus no stresses are applied to the coated circuit, and combined with fracture elongation of up to 200% for parylene C, the result is a homogeneous and flexible layer capable of accepting significant distortions liable to result from functioning of the circuit.
This characteristic has two significant advantages:
The first advantage is for invasive devices or all devices that change their volume in the application (such as an inflatable invasive balloon, etc.) and whose polymeric coating quality must also be preserved during elongation.
The second advantage is in various electronic devices in which there is a fear of the development of tin whiskers. The capability of elongation of the parylene and it flexibility permit it to elongate up to a specific length in the region of the lead-free tin and not necessarily to be damaged immediately like other coatings.
|Properties||Test Method||Parylene C||Epoxies||Silicone||Urethanes [ur]|
|Elongation to break, %||ASTM D882-56T @ 10% strain/min||200%||3-6%||100%||100-1,000%|