Five important facts about acrylic conformal coatings

conformal coated PCBs Collage 640x480_Nexus

The  majority of conformal coatings used in the world are organic coatings.

The acrylic conformal coatings are part of that group.

Here are five reasons to use acrylic conformal coatings:

  1. Acrylic conformal coatings have excellent humidity resistance. This is the number one use for using an acrylic conformal coating.
  2. Solvent based acrylic conformal coatings are one of the easiest materials to apply to printed circuit boards. They are easily applied using every method including spraying, dipping and brushing.
  3. Acrylic solvent-based coatings dry quicker than nearly all other types of coatings. They dry within minutes. This is because the acrylic resin does not polymerise (does not cure) and actually just dries out as the solvent evaporates away. They are also very easy to dry artificially using heat and can reach optimum properties very quickly.
  4. Acrylic coatings are very easy to repair and rework since they have very little chemical resistance. They are easily chemically removed and stripping a complete board is relatively straightforward.
  5. Finally, acrylic coatings have excellent pot life compared to many other types.

Need to find out more?

Click for further information on organic and acrylic conformal coatings 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.

 

Advertisements

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.

 

Five key facts about plasma cleaning for conformal coating processing

  1. Plasma cleaning can clean surfaces of the circuit board 100% to improve adhesion and surface energy of the product. Generally, conformal coatings must exhibit good adhesion in order to be effective.
  2. There is no single theory that describes the property of adhesion for coatings. There are several basic mechanisms for coatings that are known to define good adhesion. They are adsorption, chemical bonding, and mechanical interlocking:
  • Adsorption is where the molecules in the conformal coating wet or flow freely over the substrate and make intimate contact with the substrate. This forms interfacial (electrostatic) bonds with van-der-Waal forces.
  • Chemical bonds are formed at the interface between the conformal coating and the substrate.
  • The conformal coating film penetrates the roughness on the substrate surface. This results in mechanical interlocking once the coating dries.

All three of mechanisms do not have to occur to form good adhesion. Depending on the specific conformal coating system, substrate, and application method, different mechanisms could work. However, good wetting or adsorption is normally required.

  1. Many wet chemistry cleaning processes can be eliminated. Methods using cleaning chemistries, water processing and drying energy become unnecessary.
  2. The significant improvement in adhesion enables the use of alternative conformal coatings and other chemical vapour deposition coatings (CVD) that may have difficulty adhering to circuit boards without the treatment.
  3. The plasma cleaning process is a simple, safe and environmentally friendly technology.

Plasmatreatment of circuits collage

Plasma cleaning can clean surfaces of the circuit board 100% to improve adhesion and surface energy of the product. Generally, conformal coatings must exhibit good adhesion in order to be effective.

 


Need to find out more?

For further information on plasma cleaning for conformal coating processing 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 application methods are available for applying conformal coating?

 

Conformal coatings can be applied to printed circuit boards (PCBs) in the production process environment in many different ways.

Listed below are the common methods of applying conformal coating materials:

Click on each to review each conformal coating application technique in our free ebook online.

Nexus
Conformal coatings can be applied to printed circuit boards (PCBs) in the production process environment in many different ways including spraying selectively, batch spraying and dipping.

The holistic approach to conformal coating application methods 

It is possible to split the different application methods and their suitability in many different ways including:

  • Compatibility with the conformal coating material
  • Design of the circuit board
  • Suitability to low, medium and high volume
  • Manual versus automatic process
  • Type of method of application
  • Level of control required

Each of the various coating methods has different advantages and disadvantages.

This relates to the holistic approach to conformal coating processing. It states that you should consider the conformal coating material itself, the application process and the circuit board together and not as three separate entities.

However, when considering the application methods it is possible to make some assumptions that help in selection.


Need to find out more?

For further information on conformal coating application methods 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.

 

Why use conformal coatings to protect a printed circuit board?

 

There are a lot of different reasons for using a conformal coating material or Parylene to protect a printed circuit board (PCB).

These reasons can include:

  • Barrier protection
  • High insulation protection
  • High moisture and humidity protection
  • Chemical and temperature resistance
  • Ruggedising
  • Improve dielectric properties
nexus1.jpg
There are a lot of different reasons for using a conformal coating material to protect a circuit board including barrier protection, increased insulation resistance, chemical protection and increased dielectric properties

Barrier protection

A conformal coating can create a barrier against attack during the lifetime of the circuit board.

The coating material can prevent various types of particulate contamination reaching the surface of the circuit board, which can lead to problems such as corrosion.


High insulation protection

Conformal coatings can provide a high degree of insulation protection for the circuit board during its lifetime when applied as a protective lacquer.

The circuit board normally starts with a high level of insulation when it is first manufacture as it is normally clean.

However, with time in the field and its natural environment the circuit can degrade in different ways.

The conformal coating can slow this degradation down.


High moisture and humidity protection

Printed circuit boards can be vulnerable to moisture and humidity whilst in the field during its lifetime.

Most conformal coatings are highly resistant to moisture and humidity and this can lead to a reduction in leakage currents, cross talk, electrochemical migration, dendrite growth and arcing across the circuit board.


Chemical and temperature resistance

Some conformal coatings can be highly resistant to many types of solvents, chemical attack and be heat resistant.

Normally, a circuit board exposed to chemically aggressive environment would be attacked but the conformal coating can slow down the effects or even prevent them.


Ruggedising

Conformal coating can prevent damage from rough handling, installation and reduction of mechanical and thermal stress.


Improved dielectric properties

Just as the conformal coating can protect the circuit from moisture it can also help to increase the dielectric strength on the circuit board between components and lead interconnects.

This enables the design of the PCB to be more compact and small.


Need to find out more?

For further information on using conformal coatings 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)?

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.

 

What sectors are fluoropolymer coatings used? 

I am regularly asked where fluoropolymer coatings are used? After all they are a relatively new coating type in the world of conformal coatings and printed circuit boards.

Well to be honest, fluorinated coatings are used in almost all industrial sectors.

They include:

  • Aviation
  • Aerospace
  • Defense
  • Automotive
  • Industrial
  • Oil & Gas
  • Electronics
  • Medical/Pharmaceutical
  • Optics
  • Telecommunications
  • White goods / Commercial

This list is limited and there are a lot more areas that they are used.

In terms of products that are actually coated right now in fluoropolymer coating materials there are many.

They include:

  • Circuit boards
  • Mobile phones
  • Tablets
  • Automotive parts (gears, rotors, pistons)
  • Commercial bake-ware
  • Glassware, labware
  • Machine parts/components
  • Printing equipment
  • Sintered metal parts
  • Catheters, guidewires
  • Fasteners
  • Screen (metal/synthetic)
  • Filter media (cloth, synthetic)
  • O-rings, gaskets, seals
  • Silicone rubber
  • Solenoid, springs, coils

What is really interesting is that these coatings are really advancing in technology and changing all the time. Companies are tailoring the coating technology to the problem.

They are a wonderful material waiting for a project or problem to solve.

They are also being used in new and different ways.

For example, we are now experimenting with depositing the fluorinated films by plasma coating. This actually makes the bonding stronger and improves the overall performance without significant cost.

Fluoropolymer nano coating repels water 600

Fluoropolymer coatings are also being used in new and different ways. They are being depositing by plasma coating. This actually makes the bonding stronger and improves the overall performance without significant cost.


Need to find out more?

For further information on fluoropolymer coating 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.