Parylene AF-4 is the only parylene type that displays a consistent degree of UV-resistance, one wherein performance is maintained relatively long-term. Like the other parylene types, AF-4 also forms an effective, structurally continuous protective film as thin as several hundred angstroms, due to uniqueness of the chemical vapor deposition (CVD) process used to coat substrate surfaces.

Also called aliphatic fluorinate, AF-4 replaces the alpha hydrogen atom of the N dimer with fluorine, and totals 4 atoms. This compositional variation allows AF-4 to generate the lowest parylene coefficient of friction and dielectric constant throughout UV-exposure, and the highest penetrating ability. AF-4 is also useful in high temperature, short-term applications up to 450°C.

Basic information

Chemical Properties

Features

Characteristics of Parylen AF4 coating:

Specialties:

? Unmatched UV stability
? Excellent thermal stability at high service temperature (350)
? Unmatched oxidation stability
? Completely conformal coating
? Superior crevice penetration, pin hole free
? Anti-saline damage
? Anti-stick ion

Barrier properties:

? Chemical insolubility and solvent resistant
? Low water absorption
? Hydrophobic properties
? Low gas permeability , no out-gassing

Physical & mechanical properties:

? Transparent
? Light-weight and ultra-thin
? Low CTE
? Low coefficient of friction
? Good dry lubricity
? Abrasion resistance
? Stabilization of components and structures
? Particulate immobilization

Electrical properties:

? Electrical insulation
? High dielectric strength
? High volume resistivity ,ohm-cm
? Low dissipation factor
? Low dielectric constant
? Mitigation of tin whisker growth

Biocompatibility and bio-stability

? USP class VI
? Microorganism resistance

Application

Parylen AF4 is extremely useful in high temperature applications and those in which long-term UV stability is required.

? Aerospace
? Military
? Electronic
? Medical
? Industrial
? Semiconductor (3D IC TSV electrical insulation , AMOLED De-bonding layer , Barrier layer )
? Bio-MEMS electrode protection film
? EWD (Electro Wetting Device) Liquid lens

Parylene AF4 Polymer is superior to most liquid-based coatings like acrylic or silicone. The parylene is an excellent coating for protecting aerospace PCBs and many other electronic components and assemblies. The encapsulation conforms amazingly on all kinds of device surfaces, including edged services, complex creviced services, flat or round surfaces. Another plus point of the polymer is that the coating does not increase the weight of the coated device in anyways.