What is Parylene?
Deposition Process
Parylene Benefits
Parylene Properties
Design Guidelines
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Parylene Recommendations

Working with parylene

Parylene requires specific knowledge that tends to differ from previous coatings you may have used. Below you will find the best practices for working with parylene.

Design
Guidelines

Parylene is a robust material with a unique vapor deposition process among conformal coatings. As a result, parylene requires specific knowledge that tends to significantly differ from previous coatings you may have used. Below you will find design best practices for working with parylene to extract maximum benefits.

Masking Considerations

Parylene film is produced via deposits of individual monomer molecules onto surfaces as a gas. As a result, parylene is highly intrusive and will penetrate the smallest of openings to coat everything in its path. The masking process is therefore critical to the success of coated parts. Parylene repair and removal is often a difficult and costly process to implement. Below are design factors that directly impact the masking process.

Board Simplicity

Design the board to make it efficient to mask and de-mask the areas to be free of Parylene. For example, flat solder pads are easier to mask when associated components are not yet attached creating complex 3D topographies.

Masking Tolerance

Ensure there is space between components to allow masking materials to be applied efficiently and ensure secure coverage. For example, placing small resistors adjacent to a connector that will require masking may result in the resistor not being parylene coated thoroughly.

Masking Selection

Parylene offers a truly conformal coating without bridging, peeling or pooling. As a result, choose to mask only when absolutely needed. For example, un-plated holes and other low points will not pool. Heat sinks, dependent on coat thickness, may not meaningfully impact heat dissipation as there is no bridging between individual fins.

Component Considerations

When selecting components for your board, emphasis should be placed on “gas-friendly” connectors. Doing so can drastically reduce the amount of masking required. Choose sealed connectors, switches and relays that have a closed back or bottom without vent holes or alignment pinholes.

Pre-Sealing Connectors

Sealing connectors prior to arriving at the masking stage will reduce overall process cost. Choose silicone or epoxy material to seal connector bases and openings.

Male Connectors

Where applicable, choose male pin type connectors for your board design. Male connectors simplify the masking process by mating with a simple boot to seal. Female sockets require careful and time consuming masking.

Cables and wires

Parylene is deposited inside a vacuum chamber of fixed size. To make efficient use of chamber’s space constraints avoid cables and wires that protrude from your board. Selecting shorter cable and wires will increase density per batch reducing cost.

Determining Your Coating Requirements

Top 10 considerations when comparing conformal coatings

Biocompatibility:

Does the coating exhibit long-term compatibility with body fluids and tissues? When applied onto the substrate, are there any toxic chemical interactions and/or byproducts that could be harmful to a patient or to the function of the device?

Parylene is 100% biocompatible.

Hydrophobic & Hydrophilic Characteristics

Does the coating aim for lubricity when dry or wet? (I.e. a cardiovascular catheter that is hydrophilic (slippery when wet) vs. a hydrophobic guidewire that is easy for a cardiologist to grip.)

Parylene is hydrophobic.

Coating Inertness

Does the coating contaminate the substrate with outgassing from process catalysts, cure agents, solvents or plasticizers?

Parylene is 100% chemically inert

Cure Temperature

Does the cure temperature of the coating exceed the performance range of the substrate?

Parylene does not require curing of any kind.

Cure Forces

Does the curing process degrade or distort the underlying substrate?

Parylene does not require curing of any kind.

Conformability

Does the coating offer conformability to highly variable surface geometries?
Does the coating maintain conformability at all magnitudes and surface feature sizes, from macro to micro?

Parylene is 100% conformal.

Finished Thickness

Does the finished coating meet tight dimensional tolerances while maintaining desired physical, chemical, or electrical protection that is free of voids and pinholes?

Parylene coating range is measured in microns and is free of voids and pinholes.

Mechanical Loading

Does the coating perform its function without significantly altering the physical or mechanical properties of the substrate?

Parylene’s micron-thin film does not add meaningful mechanical load.

Resistance to Flaking

Does the coating sufficiently adhere to the substrate to avoid flaking?

Parylene has excellent adhesion to most substrates.

Sterilizability

Does the coating withstand the effects of sterilization processes?

Parylene withstands most sterilization processes.

Find the service that’s right for you.

VSi’s Total Solution is a comprehensive, step-by-step suite of services designed to integrate parylene coating seamlessly into your production activities.

Find the service that’s right for you.

VSi’s Total Solution is a comprehensive step-by-step suite of services designed to seamlessly integrate parylene coating into your production activities.’