The science behind Molecular vapour deposition (MVD) in protecting circuit boards

Nexus has been examining a new, novel technique that may be able to superior protection for electronic circuit boards compared to the standard coating methods like conformal coatings and Parylene but also actually be cost-effective.

This process is a hybrid ALD (Atomic Layer Deposition)/CVD (Chemical Vapor Deposition) technique called Molecular Vapor Deposition (MVD).

This method uses multiple layers of ultra-thin coatings with differing properties to build a completely protective coating.

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So, why is this new coating so good compared to Parylene and other conformal coatings?

The final MVD coating built up is much thinner than the other traditional coatings including Parylene. However, its protective performance has been found to be superior to them all in most categories of testing so far.

Key performance indicators like Water Vapor Transmission Rate (WVTR), optical clarity, temperature resistance and hydrophobicity have been found to be much better than the other coatings.

Further, the really exciting part about this technology is the cost of processing that is extremely low.

Since the coating is extremely thin then it has been found that no masking is required. This is because when components like connectors are joined together then the ultrathin coating does not prevent electrical connection.

This means that the cost of process is purely the cost of application of the material and nothing else.

Since the process is relatively low cost then this does offer a very interesting alternative to the traditional coating materials.

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So what does the science of Molecular Vapor Deposition coating (MVD) look like?

The actual film is built up of alternating layers of ALD and CVD thin coating layers.

The ALD is a ceramic-based material providing the insulating properties. The CVD film provides the barrier protection.

First, an ALD layer is applied to the substrate. Then a CVD layer is applied. Then a further ALD layer is applied and so on.

This continues until the correct number of layers is built that has the right protection.

Finally, once the required film thickness is achieved with the alternating layers, then a final hydrophobic thin film layer is applied, that combines with the ALD and CVD layers to provide a highly effective barrier.

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So, just how good is the hybrid coating as a protective material for electronic circuit boards?

Generally, with protective coatings for electronics then Parylene is considered the gold standard in most cases.

So, Nexus compared Parylene with the MVD material.

Property	Parylene	MVD Coating
Hardness	Soft	Hard
Wear resistance/Handling Ease	Poor	Excellent
Water Vapor Transmission Rate	Good	Excellent
Temperature Resistance (extended time)	100°C	350°C
Color	Gray/white	Clear
Adhesion to various materials	Poor	Excellent
Scalable to large production	Poor	Excellent
Process Time	8 – 12 hrs	8 – 12 hrs
Hydrophobicity	Good	Good – Excellent
Cost	High	Low – Med

What Nexus also identified for the material were some key properties.

• The Water Vapor Transmission Rate (WVTR) is superior to Parylene so the coating is far more waterproof.
• Coating adhesion is superior as it covalently bonds to the substrate. So, the lifetime of the material will be better on the circuit.
• The temperature range of the material can be up to 350C without any degradation.
• The hybrid coating is UV stable whereas Parylene in general is not. This is an important criteria for coatings exposed to UV light.
• The coating stayed 100% transparent during testing (no loss of lux).
• The coating thickness of the hybrid material is x10 LESS than the Parylene. This aids light transmission and electric connectivity

So, in reality the MVD material could just be what industries like the automotive and LED sectors are looking for in protecting their circuits where cost and protection abilities are critical.

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Need to find out more?

Contact us directly and we can help you with this new material.

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page or our free conformal coating eBook.

What is Molecular Vapour Deposition (MVD)?

Nexus has been examining a novel coating technique that may be able to meet all of the environmental demands for circuit board protection and actually be cost-effective.

This process is Molecular Vapour Deposition (MVD) and is brand new to the electronics coating market.

MVD is a hybrid coating technique using ALD (Atomic Layer Deposition) and CVD (Chemical Vapor Deposition) coating processes in combination.

This method uses multiple layers of ultra-thin coatings with differing properties to build a completely protective coating.

The final coating built up is much thinner than the other traditional coatings including Parylene. However, its protective performance has been found to be superior to them all in most categories of testing so far.

Further, the really exciting part about this technology is the cost of processing.

Since the coating is extremely thin then it has been found that no masking is required.

This is because when components like connectors are joined together then the ultrathin coating does not prevent electrical connection. Even better, the physical protection is not compromised.

This means that the cost of process is purely the cost of application of the material and nothing else.

Since the process is relatively low cost then this does offer a very interesting alternative to the traditional coating materials.

Does MVD sound complex?

Actually, although the technology and chemistry can be a little complex the process itself is fairly simple.

Once the process is set up in the machine the operator just loads, switches the machine on and unloads on completion.

This is a far cry from the sophisticated processes of robotic selective coating or the challenges of Parylene. Further, the process is actually very stable and in reality is tried and test in other industries.

So what does a MVD film look like?

The film is built up of alternating layers of ALD and CVD thin coating layers. The ALD is a ceramic-based material providing the insulating properties and the CVD film provides the barrier protection.

Once the required film thickness is achieved then a final hydrophobic layer is applied that combines with the ALD and CVD layers to provide a highly effective barrier.

Label: The film is built up of alternating layers of ALD and CVD thin coating layers. The ALD is a ceramic-based material and the CVD film is an organic layer.

So how well did the MVD coating perform when protecting circuit boards?

Data was recently presented at Apex in Sand Diego looking at live LED circuits from a customer.

The customer LED product was for outdoor application. For testing, the customer used in-house test methods to prove the technology.

The LED circuit was exposed to customer tests for resistance against salt, moisture and temperature.

The test methods included:

• Initial test submerged in DI water dip for 12 hours
• Second test submerged in 25% concentration saltwater dip for 17 hours
• Third test 2 x 6 hour cycles in water ramped from room temperature to 70°C

After each test the boards were tested for failure or problems.

The LED circuit passed on all tests. All results achieved were completed with no masking of components and zero light loss in LED opacity.

The electrical connections were found to be excellent and the coating did not affect the integrity of the connectors.

So what about the cost of process for MVD?

Since the process is masking and de-masking free then the cost per unit is incredibly low. The performance is also superior to nearly all the traditional methods of coating protection.

Further, the protective properties of the MVD coating in nearly all cases is superior to the conventional methods.

So, you get a lower cost coating with a higher technical performance.

So, just how good is the MVD coating as a protective material for electronics?

Generally, with protective coatings for electronics then Parylene is considered the gold standard in most cases.

So, we compared Parylene with the MVD coating material.

Property	Parylene	MVD
Hardness	Soft	Hard
Wear resistance/Handling Ease	Poor	Excellent
Water Vapor Transmission Rate	Good	Excellent
Temperature Resistance (extended time)	100°C	350°C
Color	Gray/white	Clear
Adhesion to various materials	Poor	Excellent
Scalable to large production	Poor	Excellent
Process Time	8 – 12 hrs	8 – 12 hrs
Hydrophobicity	Good	Good – Excellent
Cost	High	Low – Med

What we also identified for the material were some key properties for LEDs.

• The Water Vapor Transmission Rate (WVTR) is superior to Parylene so the coating is far more waterproof for the LEDs
• Coating adhesion is superior as it covalently bonds to the substrate. So, the lifetime of the material will be better on the circuit.
• The hybrid coating is UV stable whereas Parylene in general is not. This is an important criteria for coatings exposed outside on LEDs
• The coating stayed 100% transparent during testing (no loss of lux). That again is important for LEDs.
• The coating thickness of the hybrid material is x10 LESS than the Parylene. This aids light transmission and electric connectivity

So, in reality the MVD material could just be what the high volume electronics industry is looking for in protecting their circuits.

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Need to find out more?

For further information on Molecular Vapour Deposition (MVD) then contact us directly.

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page or our free conformal coating ebook.

 

What is molecular vapour deposition (MVD) and what are its advantages against Parylene?

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

The molecular vapour deposition (MVD) process can produce both hydrophobic and hydrophilic 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

MVD is used in many different modern day electronics

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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.

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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.

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Dr Lee Hitchens, Author of Nexus

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?