Parylene Coating Process

Parylene Processing

Parylene films are created via a Chemical Vapor Deposition (CVD) process.

As part of this process there normally are four stages. These are:

  • Stage 1: Vapourisation

  • Stage 2: Pyrolysis

  • Stage 3: Coating Deposition

  • Stage 4: Cold Trap

Stage 1: Parylene Vapourisation

  • Dimer is placed in the glass tube at the opposite end from the deposition chamber in an aluminum foil cup called a “boat”.
  • The volume of dimer placed in the boat will determine the final coating thickness deposited on the product.
  • The boat is inserted into the vaporizer stage of the Parylene system and the process started.
  • The vaporizer radiant heater heat the dimer to between 100-180ºC.
  • The dimer changes from a solid to a vapor
  • The molecules move down the tube by virtue of the reduced pressure at the opposite end.

Stage 2: Parylene Pyrolysis

  • At this time the vapor is pulled under vacuum into the pyrolizer furnace zone.
  • The pyrolysis zone is typically at temperatures of 650-700°C.
  • This high temperature cleaves the dimer by sublimation into monomers.
  • The monomer is now ready for transfer to the coating deposition chamber.

Stage 3: Parylene Coating Deposition

  • The monomer molecular gas continues to be drawn by vacuum one molecule at a time into the coating chamber.
  • The monomers are collectively re-aligned and reform into polymer chains on all surfaces within the chamber.
  • The monomer deposits on the desired substrate at ambient temperatures in the coating chamber.
  • The coating forms slowly and uniformly over surfaces with both sharp edges and deep crevices with no pinholes.

Stage 4: Cold Trap

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

 

Key Elements of the Process

There are many key points to the process.

They include:

  • Dimer vaporized at ~180°C
  • Pyrolized to Monomer at ~700°C
  • Polymerization occurs on product surface at room temperature
  • Deposition process – occurs only at vapor level, no liquid phase throughout
  • Low vacuum pressure (30-50 mtorr)
  • Process in non-toxic from start to finish
  • No volatile effluents (VOC’s)
  • Minimal impurities (99% pure)
  • Controlled process – beginning to end.
  • Polymerization process is slow, can take 4 hours, or 20+ hours.
  • Deposition at the molecular level…one at a time, on all surfaces (even chamber walls)
  • No initiators or curing required
  • Controlled film thickness (nanometers, microns or mils)
  • Completely 3-dimensional process
  •  Thin film…no weight added to target substrate

The Total Parylene Process

The actual Parylene coating process involves a complex sequence of stages.

They include: 

  • Inspection
  • Cleaning
  • Drying
  • Masking (as required)
  • Surface Preparation or Promotion
  • Coating Application Process
  • De-masking (as required)
  • Final Inspection

Understanding that this is a complete process and good process development is critical is the key to a great solution. Thin film Partners can take the pain away from this process development. 

 

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Talk to us about your Parylene coating requirements now.

We have the knowledge, tools, experience and the complete solutions whatever you need. We are here to help. 

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