Co-authors and contributors

  • Dr Lee Hitchens, Nexus
  • Jason Delaney, Curtiss-Wright
  • Craig Barter, Paratronix

The Parylene Process: Video courtesy of Curtiss-Wright

The four stages of the Parylene process

The Parylene process can comprise of four Stages.

  • Stage 1: Vapourisation
  • Stage 2: Pyrolysis
  • Stage 3: Coating Deposition
  • Stage 4: Cold Trap

The process is shown visually below:Paratronix Parylene Process

Schematic of the Parylene Process: Image courtesy of Paratronix

Stage 1: Parylene Vapourisation

  1. Dimer is placed in the glass tube at the opposite end from the deposition chamber in an aluminum foil cup called a “boat”.
  2. The volume of dimer placed in the boat will determine the final coating thickness deposited on the product.
  3. The boat is inserted into the vaporizer stage of the Parylene System.
  4. An end cap is then placed over the glass tube and the process started.
  5. The vaporizer radiant heater cycles on and off with a pressure safety interlock to ensure safe operating limits.
  6. The raw dimer is heated between 100-150ºC.
  7. The dimer changes from a solid to a vapor and the molecules move down the tube by virtue of the reduced pressure at the opposite end.

Stage 2: Parylene Pyrolysis

  1. At this time the vapor is pulled under vacuum into the pyrolizer furnace zone.
  2. The pyrolysis zone is typically at temperatures of 650-680°C.
  3. This high temperature cleaves the dimer by sublimation into two divalent radical monomers.
  4. Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.
  5. The monomer is now ready for transfer to the Coating Deposition Chamber.

Stage 3: Parylene Coating Deposition

  1. The monomer molecular gas continues to be drawn by vacuum one molecule at a time into the Coating Deposition Chamber.
  2. The monomers re-form as a long chain polymer on all surfaces within the chamber.
  3. The monomer deposits on the desired substrate at ambient temperatures in the coating chamber.
  4. The coating forms slowly and uniformly over surfaces with both sharp edges and deep crevices with no pinholes.

Stage 4: Cold Trap

  1. The final stage of the parylene deposition process is the cold trap.
  2. This is between the Coating Chamber and the pump.
  3. The cold trap is cooled to between -90ºC and -120ºC.
  4. It is responsible for removing all residual parylene materials pulled through the coating chamber.