Parylene coatings

PARYLENE COATINGS - GALWAY DIVISION

Parylene coating has a long and successful history in the automotive, aerospace, electronic and medical industries, solving many design challenges. This ultra thin film coating provides a consistent pin-hole free barrier that is truly conformal, coating all shapes, edges, crevices and recesses to the same thickness without suffering any of the edge effects of conventional coatings.

 

Benefits of Parylene coatings

  • Ultra thin film – coating thickness of less than 1 µm can be applied providing sufficient lubricity and barrier protection for most silicone and rubber materials penetrating openings and features as small as 0.01mm
  • Uniform coating – thickness tolerances are typically held to ±20% from nominal and tolerances as tight as ±5% are possible even for the most intricate and complex shapes
  • Stability – Parylene is inert and insoluble in most solvent systems within its temperature range. It is thermally stable between -200°C and 140°C
  • Pin-hole free barrier coating – with no additives offering resistance to chemical attack from organic solvents, inorganic reagents, acids, oxygen and moisture
  • Lubricant – Parylene acts as a dry film lubricant, eliminating the need for liquid release agents
  • Low stress process – applied at room temperature. Any object which can be exposed to medium vacuum can be coated with Parylene
  • Elasticity – elongation and adhesion of the Parylene film with elasticity above 2x (100%)
  • Cost effective – utilises batch processing
  • Hydrophobic – overcomes internal and external fluid build-up in silicone tubes and other components
  • Optical clarity – Parylene C is optically clear
  • Sterilisation – coated devices may be sterilised with steam, ETO (Ethylene Oxide Sterilisation) or radiation
  • Dielectric strength – extremely high dielectric strength of 5 kV/mil
  • FDA – Parylene is FDA approved

 

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Parylene Coatings on medical equipment

 

Parylene coating on a stent

The process of Parylene coatings

Parylene is applied by vapour deposition under a vacuum in a coating chamber at room temperature. The coating process exposes objects to a gas-phase monomer at low pressure. Through vacuum deposition, Parylene condenses and polymerizes on the object’s surface in a polycrystalline formation. The Parylene coating grows at a rate 0.2 µm - 0.3 µm per minute depending on type N or C respectively.

 

Parylene coatings process

 

Parylene coating is normally applied using a batch process where parts are put into a chamber, either horizontal (tumbler) or vertical. The batch process offers a cost effective solution for many applications.


Parylene C is most widely used as it has good electrical and physical properties.


Parylene N is selected for its high dielectric strength and where greater coating penetration is needed.

 

QUALITY CONTROL

Stringent checks are applied throughout the process, including:

  • chemical analysis of the dimer
  • temperature and pressure monitoring of the deposition cycle
  • careful visual inspection of the coated substrates
  • witness strips to confirm thickness
  • adhesion testing of the coated samples

 

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Parylene C

 

Parylene N

 

Parylene coatings on equipment

Applications of Parylene coatings

MEDICAL DEVICES

Parylene is ideal for medical applications requiring a protective conformal coating, biomedical compatibility and deposition to a thickness that is both critical and consistent.


Parylene provides a pin-hole free protective barrier against biofluids, moisture and chemicals.

 

Parylene also acts as a dry film lubricant with a coefficient of friction measurement that approaches that of TEFLON®. Parylene type N is typically used in applications requiring this type of releasability or dry film lubricant.

 

Typical medical applications include:

  • STENTS – uniquely suited to coat the intricate structures of stents, without webbing or pooling. Parylene is nonthrombogenic and can facilitate the adhesion of drug-polymer combinations when applied directly onto Parylene coated stents.
  • CATHETERS – improved lubricity, reducing the chatter of insertion or removal and barrier protection against biofluids.
  • MANDRELS – to increase the releasability of the newly formed catheter from the forming mandrel.
  • CARDIAC ASSISTED IMPLANTABLE DEVICES – protection for pacemakers and implantable defibrillators against the corrosive effects of biofluids including the electrical isolation of metal cases.

 

OTHER APPLICATIONS

Other applications include pressure sensors, medical instrumentation, ultrasound transducers, guide wires, needles, epidural probes and elastomer products (silicone, latex gasket and seals), wherever lubricity and barrier protection is required.

 

CIRCUIT BOARDS

Parylene films ranging from 6 µm – 40 µm in thickness provide a barrier which is equivalent or superior to 50 µm – 150 µm of other conventional coatings. Parylene does not pull away from edges or exhibit meniscus forces as do conventional liquid coatings applied by spraying, dipping or brushing. Board components are evenly and consistently coated with an ultra thin layer of Parylene. The dielectric constant and dissipation factor are practically insensitive to changes in frequency.


Given its resistance to humidity, its barrier, physical and thermal properties and its unique molecular structure, Parylene is practically insoluble in all known organic and inorganic solvents including strong acids and alkali. Parylene has proven to be an effective barrier against corrosive agents and does not out-gas. Parylene is an excellent choice when it comes to conformally coating printed circuit boards for military and aerospace applications.


When looking at the total cost of protecting electronic components in a hazardous or contaminated environment, Parylene provides an extremely cost effective option.

 

WIRE WOUND DEVICES

  • magnets
  • wire wound ferrite cores
  • powdered ferrite cores

Parylene eliminates abrasion damage to the wire in the winding process along with uniform coating thickness. Unlike the variance of thickness (bridging, shrinking, thin out and pin-holes) with conventional liquid, spray or brushed on coatings, Parylene gives a maximum winding window.


Parylene does not impart magnetostrictive or permeability problems that may be encountered with conventional varnish impregnation.


With Parylene’s low water vapour transmission properties it provides excellent corrosion protection.

 

RUBBER

Parylene yields a truly conformally coated part with a consistent thickness on the flat surface area and around the internal dimensions of holes. Irrespective of the size or shape of the elastomer application, Parylene film conforms to the surface features.


With Parylene film’s surface adhesion and elasticity, the coating can handle substantial elongation of the elastomer part with minimal fracturing or breaking of the surface adhesion of the film from the substrate bond.


Rubber keyboard applications using the Parylene coating process will remove the elastomer tack but will also protect the keyboard against dirt, oils, petrochemicals and solvents whilst also protecting printed legends from wear.

 

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Medical Applications
  • Pacemakers
  • Defibrillators
  • Stents
  • Silicone catheters
  • Guide wires
  • Mandrels
  • Elastomers
  • Pressure sensors
  • Medical instrumentation
  • Ultrasound transducers
  • Needles
  • Epidural probes

 

Other applications
  • Rings and seals
  • Rubber keyboards
  • Circuit boards
  • Gaskets
  • Valves
  • Wire wound devices

 

Coated circuit board

 

Parylene caotings applications