How does Parylene material differ from liquid conformal coatings and where can you buy it?

nexus1

Parylene is very different to typical liquid conformal coatings like acrylic, epoxy, silicone and polyurethane resin based materials.

When you buy Parylene it is a white powdered dimer.

This powder cannot be applied to circuit boards in its current state. The dimer requires specialist Parylene equipment that uses a Chemical Vapour Deposition (CVD) process. That is the dimer is placed inside the machine, a vacuum created and the dimer is then transformed to a gas vapour by being heated up.

This vapour created during the pyrolysis process can then be deposited on the printed circuit board as the Parylene coating.

This is very different to liquid conformal coatings. They start off as a “varnish” in a can or container and are applied to circuit boards by brushing, dipping or spraying. They then dry either naturally or artificially in some manner and the circuit board is now protected.


Where to buy Parylene

When purchasing Parylene it is important to find a source that provides a quality product. The purity of the coating is one of the key points in creating a successful Parylene process. Neglecting this fact can cause endless problems.

Remember that buying Parylene cheaply is easy. Buying cheap Parylene that is pure enough to protect the circuit board is another issue.

Thin film Partners can inform you of the right vendors who supply high-quality material and the pricing for each type. Then you can compare which vendor you would like to buy from.

This is a cost effective method to ensure you get the right Parylene coating at the right price.


Want to find out more about Parylene?

Contact us to discuss your needs and let us explain how we can help you.

Contact us now.

Advertisements

Why is it harder to mask and de-mask Parylene on a circuit board assembly compared to traditional liquid conformal coatings?

There are four key reasons why Parylene masking and de-masking is more difficult compared to liquid conformal coatings.

These are:

  1. Parylene is a vapour. When you are masking against a gas rather than a liquid then there is more of a challenge. So you need to provide a much better barrier with the masking process compared to the liquid coatings.
  2. Parylene is immersion. Most liquid conformal coatings are sprayed and so the capillary is less compared to immersion in a limitless supply of material.
  3. Stripping Parylene is hard. It is much harder to remove unwanted Parylene material on components that should not have been coated. Parylene is chemically inert (therefore harder to strip off or remove) and more difficult to see (no UV trace in most Parylene coatings). Mistakes can be more costly.
  4. The Parylene can bond more to the masking materials. When the Parylene is deposited on the masking materials and circuit board it can bind the two together and it can take significant effort and care to remove the masking materials without damaging the board or the Parylene coating integrity.

Need to find out more?

Click Parylene coating to protect electronic circuit boards to find out further information or contact us directly and we can help you.

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.

Why use Parylene to protect printed circuit boards?

Parylene2

Parylene is a conformal coating film that is applied using a specialised vapour deposition application process.

This means it is very different to all of the other liquid conformal coatings available on the market.


Three reasons why Parylene is better than traditional liquid conformal coatings

The fact that the Parylene film is deposited onto circuit boards in a vacuum leads to many unique advantages.

Here are three key reasons to use Parylene:

  1. The Parylene coating is completely conformal to the surface of the Printed Circuit Board (PCB) or product. The coating has a uniform thickness and is pinhole free. Therefore, components with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids.
  2. Parylene coating provides an excellent barrier that exhibits a very low permeability to moisture and gases compared to traditional liquid conformal coatings. This means that circuit boards coated in Parylene generally are more “waterproof” than the same circuits coated in a liquid conformal coating.
  3. Parylene has excellent electrical properties compared to normal conformal coatings. These include low dielectric constant and loss with good high-frequency properties, good dielectric strength, and high bulk and surface resistance.

Need to find out more?

Go directly to our Parylene section in Nexus  or contact us directly and we can help you.

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 Parylene?

Parylene is the trade name for a variety of chemical vapor deposited poly (p-xylylene) polymers used as moisture and dielectric barriers.

Although Parylene is a conformal coating it is different compared to the standard “wet” liquid conformal coatings in that it is deposited as a gas in a vacuum chamber and it is a dry process.

nexusphoto1Although Parylene is a conformal coating it is different compared to the standard “wet” liquid conformal coatings in that it is deposited as a gas in a vacuum chamber and it is a dry process. Image courtesy of Plasma Rugged Solutions

This method of chemical vapour deposition (CVD) and the Parylene dimer material itself give Parylene unique properties compared to other traditional conformal coatings.

For Parylene there are five key areas that Nexus can help with.

These are:


Need to find out more?

For further information on Parylene then contact us directly or go to our Parylene section in Nexus. See how we can help you.

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.

Description of Hybrid ALD_CVD Technology

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.


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.

 

How do you remove Parylene completely from a printed circuit board?  

Parylene is the trade name for a variety of chemical vapor deposited poly (p-xylylene) polymers used as moisture and dielectric barriers.

Although Parylene is a conformal coating it is different compared to the standard “wet” liquid conformal coatings in that it is deposited as a gas in a vacuum chamber and it is a dry process.

This method and the material itself give Parylene unique material properties that give it a lot of advantages compared to other traditional conformal coatings.

However, these unique properties also make it an extremely difficult material to remove.

Why is Parylene difficult to remove?

Compared to typical liquid conformal coatings like acrylics and polyurethanes that more easily dissolve in mildly aggressive solvents then Parylene is much tougher to remove.

The reasons are many why but a key point is that the Parylene coating itself is chemically inert. It has a high chemical resistance so the solvents don’t work well.

This means any chemical attack tried with solvents or other liquid chemicals on the Parylene is as much likely to damage the circuit board than remove the actual coating.

So, chemical removal is almost impossible.

This leaves another well know method for Parylene removal that is mechanical abrasion.

Mechanical abrasion of a coating can be done crudely by scraping off the Parylene with a knife or tool. Or, removal can be done with a media blast system that gradually erodes the Parylene coating away.

However, mechanical abrasion is a time consuming process and is highly skilled. Any wrong action could result in irreparable damage.

Further, mechanical abrasion tends to be a localised repair and removal technique. The concept of completely removing all of the Parylene of a circuit by mechanical abrasion is considered almost impossible unless a ridiculous amount of time and effort is injected into the process.

Therefore, a specialist method is required to remove Parylene completely from a whole circuit board.

A new method for completely stripping Parylene from a PCBA

Due to new research two processes have been developed for completely removing Parylene coating from the surface of a circuit.

They are:

  • A method for <15um thickness of Parylene coating on the board
  • A method for >15um thickness of Parylene coating on the board

Removal with <15um thickness of Parylene coating on the circuit

When the Parylene coating is under 15um then the removal from the whole circuit is a relatively simple process.

To successfully remove the Parylene a technique has been developed involving plasma etching.

The plasma-etch process uses a proprietary blend of gasses, and a custom system to mechanically etch off the Parylene. This specially designed alchemy of gasses specifically attacks Parylene rather than the solder mask.

The technique successfully removes the Parylene from all over the board.

Also, the etching process is quick relative to the other mechanical methods. Typically, the circuit can be completely etched of Parylene in under an hour.

Further, the process is safe. It does almost no harm to the circuit and is one of the safest methods for complete removal of Parylene.

Removal with >15um thickness of Parylene coating on the circuit

When the Parylene coating is greater than 15um then the removal from the whole circuit is a little more complex. In fact, it becomes a two-stage process.

First, you can use the plasma etch treatment to loosen the Parylene from the surface of the circuit. Normally the Parylene is bonded well to the surface and this loosening allows for a second stage process.

In the second stage a media blaster like the SWARM system can be used to remove the coating. Since the coating has been loosened it does tend to come off much easier and quicker.

That said it is still a little slow and costs are higher. But, it still can be removed more easily.


Need to find out more?

For further information on Parylene removal then contact us directly and we can help you.

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 different coating finishes of MVD.png
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 technology coating.png
MVD is used in many different modern day electronics

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, Author of Nexus website and ebook
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?