Frequently Asked Questions (FAQ)

Is parylene a hydrophobic coating?

Yes, parylene coating has hydrophobic properties repelling water and moisture.

Are parylene coatings cryogenic resistant?

Yes, this ultra-thin coating is cryogenic resistant to -200°C.

Is parylene biocompatible?

Yes, parylene N and parylene C met the requirements of USP Plastic Class VI. Testing completed by Advanced Coating.

Does parylene bond to all surfaces on the PCB?

Yes, the parylene (CVD) process will deposit the conformal coating on all surfaces of the PCB.

Does your parylene C meet Mil-I-46058C/IPC-CC-830-C?

Yes, parylene C meets the requirements of Mil-I-46058C/IPC-CC-830-C. Testing completed by Advanced Coating.

What are the advantages/disadvantages of parylene?

Advantages of Parylene:

Disadvantages of Parylene:

UNIFORMITY - Complete, uniform coverage on all surfaces.
ULTRA-THIN - Ultra-thin coating between 0.25 to 0.75 microns.
CONSISTENT THICKNESS - Consistency of coating thickness across the entire board.
EXCELLENT PROTECTION - Complete protection from moisture, fumes, gases, salt water, corrosion, fungus, and other environmental conditions.
CLEAR APPEARANCE - Parylene C and N are clear in appearance and ideal for optical applications.
NO CAPILLARY FLOW - No capillary flow under components on the circuit board.
LIGHTWEIGHT - On 1” x 1” x 0.00125 mils FR4 board with no components, parylene added 0.040 grams.
NO STRESS ON COMPONENTS - Deposition is completed at room temperature preventing stress on PCB components.

LONG PROCESS TIME - Limited throughput due to batch process cycle time.
ADHESION - Adhesion promoter required to achieve parylene bond to the PCB.
COST - Higher process and material costs than other conformal coatings.
DIFFICULT TO REWORK - Very challenging to rework localized and complete PCB.
PREP TIME - Labor intensive cleaning and masking process.
FAILURES - Failures can occur from parylene lifting at the de-masking site, cracking, no transparency, or voids anywhere on the coating.
NOBLE METALS - Poor adhesion to noble metals – gold, silver, and stainless steel.

What are the phases of the parylene process?

1 – Sublimination - The dimer granular is vaporized into a gas.

2 - Pyrolysis - The dimer gas is heated to a high temperature to produce a monomer gas that splits the dimer molecules.

3 - Deposition - The monomer gas is transferred to the coating vessel to deposit onto the PCB as an ultra-thin coating at room temperature.

4 - Chiller & Vacuum - The chiller captures the excess parylene at the end of the cycle. The vacuum pulls all the air and gasses from the chamber, facilitating the parylene deposition.

Does parylene conformal coating add weight to my PCB?

Parylene is an ultra-thin conformal coating that adds minimal weight to the PCB. The weight of the parylene layer over a 1” x 1” x .00125 mils on an FR4 board with no components is. 040 grams.

Does parylene coating evenly coat complex and intricate surfaces on my PCB?

Yes, parylene is a uniform coating over complex and intricate surfaces, controlled during the deposition phase.

What is the thickness of your parylene coating?

The parylene coating thickness can range from .1 to 50 microns (.001 – 2 mils). Typically, most customers require mil-spec standard thicknesses, which are repeatable and achievable batch after batch with our equipment.

How is the thickness of the parylene coating controlled?

The thickness of the parylene coating is impacted by the dimer mass, deposition rate, temperature, and other factors, such as the topography of the PCB.

What masking techniques will be used?

The complexity of the PCB topography determines masking techniques. Masking options are liquid maskants such as UV-curable maskants, latex maskant, polyester or Kapton tape, caps, and boots (standardized or 3D printed).

Why is an adhesion promoter used before the parylene coating deposition process?

Pre-treatment with silane stimulates parylene adhesion to promote a molecular bond from the substrate to the applied parylene coating.

Is a cleaning process necessary before the parylene process?

Yes, all PCBs are cleaned before applying the adhesion promoter and the parylene process to ensure the adhesion of the parylene coating.