Molecular Vapour Deposition (MVD) is a vacuum deposition process that provides excellent barrier properties and surface energy control.
The MVD process produces a highly conformal thin film coating, typically less than 100nm.
Where is MVD used?
MVD technology is used to produce coatings such as:
- Electrical insulation films
- Liquid and vapor moisture barriers
- Corrosion and oxidation barriers
- Lubrication and anti-stiction films
- Hydrophobic or hydrophilic surfaces
- Biocompatible surfaces
- Reactive coatings
How does the MVD process actually work?
The process works by allowing small amounts of gas-phase chemicals introduced into the process chamber and reacted at the surface to form thin films.
Unlike traditional CVD and ALD flow processes, the MVD reaction takes place in a chamber under static pressure resulting in extremely low chemical use.
Samples are typically maintained at temperatures ranging from 30°C to 80°C during deposition.
Where is MVD used in technology applications?
Typical applications include:
- Non-stick coatings for sophisticated microelectronics and parts found in smartphones, computers, displays, automobile sensors, and hard disks
- Non-wetting coatings used on inkjet nozzles
- Surface functionalization for biological assays
- Anti-fouling and lubrication coatings for parts implanted in the human eye
- Dielectric films used in virtual reality displays
- Release layers for nano-imprint lithography
What are the advantages of MVD
Complete coverage
The MVD process is designed to produce 100% coverage of all exposed surfaces on complex parts.
Conformal coating thickness control
The MVD process manages film thickness and thickness uniformity by dosing exact amounts of precursors and controlling reaction times.
Many other processes like Parylene are dependent upon amount of dimer and will continue to deposit successive polymer layers until it is completely used up causing thickness variation across the chamber.
Cost of process
MVD does appear to be a much faster process compared to Parylene to create like for like protection.
Also, it does not require silane pre-treatment and it only requires small amounts of chemicals. As a result, PCB processing cost could be very low compared to Parylene.
Multiple laminate layers are possible
MVD allows single component layers for basic barrier protection or customized laminate layering for complex requirements.
Most other films including Parylene are single component layers.
Water vapor transmission rate (WVTR) is lower than Parylene
The WVTR < 0.1 g/m2-day for a fast deposition time and < 0.00001 g/m2-day for a longer deposition time.
Parylene WVTR is typically 0.5 g/m2-day
Light transmission
MVD films are optically transparent and do not affect light transmission or reflection due to the relatively low coating thickness.
Electrical insulation
A component in the MVD coating is a flexible ceramic layer that acts to help preserve electrical isolation over time.
This can give a highly insulating coating finish.
Pinhole-free
MVD films are pinhole-free at a nanometer level thickness.
Parylene and some other materials are only pinhole-free at micron levels.
Coating stability
Coatings stable up to 450°C environment.
Ease-of-Use
The MVD system is fully automated and requires only a push of a button to run a process recipe.
If further information on these topics and the key question you can go to our free eBook by clicking molecular vapour deposition (MVD) now.
If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page.
Dr Lee Hitchens is the author of the Nexus conformal coating website and eBook.
Send me an email at lhitchens@nexus3c.com and let me know what you think?
