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.
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.
Many wet chemistry cleaning processes can be eliminated. Methods using cleaning chemistries, water processing and drying energy become unnecessary.
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.
The plasma cleaning process is a simple, safe and environmentally friendly technology.
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.
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
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.
Of course the reasons for the use of conformal coating are for safety critical reliability improvement and not just inconvenience to the user if the electronics fail.
This makes transport one of the largest sectors for conformal coating use in the world.
Conformal coatings are being used as protection in ever increasing electronic applications across a wide range of market sectors.
In the past, conformal coating was only applied to military and safety critical products like medical devices as the cost and the process of doing this was high.
However, the emphasis on reliability has changed.
In recent years, the development in materials and new processes, linked with the customer requirement of a reliable electronic product that isn’t safety critical, has meant consumer electronics products must now be protected as well.
With the new technologies like wearable electronics becoming more popular then this trend will only increase and protecting the electronics with a coating of some description will become even more commonplace.
Traditional markets like aerospace, automotive and military sectors still use conformal coatings. However, the growth in use across many other sectors is significant due to customers requiring reliable products for consumer electronics
So what sectors are using conformal coatings and other thin film technologies?
Due to the fact that conformal coatings provide several key benefits including moisture and insulation properties, chemical resistance and particulate protection, this means they can be used anywhere there is a need for a higher reliability than that which is achieved without the coating.
It is possible to identify both traditional and emerging sectors where conformal coatings are being applied.
These include sectors such as:
Aerospace
Defence
Automotive
Telecommunications
Wearable technologies
Consumer electronics
Tablets and computers
Industrial Engineering
Transport
White Goods
Geothermal
LEDs
Solar Panels
Marine and Coastal Environment
Space
Medical
Each market sector has a distinct set of requirements in terms of standards, operating environments as well as other factors that impact on the requirements.
The challenge is for the engineer to define the requirements and the suppliers to provide the protection at a commercially effective price.
To find out more click conformal coating basics to discover why conformal coatings are used and what they actually do to protect the circuit boards and products.
Dr Lee Hitchens is the Author of the Nexus eBook and a main contributor to Nexus.
I am regularly asked how I would go about choosing a conformal coating?
I normally respond to the person involved by asking an awful lot of questions and they wonder what they got themselves in to!
Why do I have to ask a lot of questions?
The questions are there because choosing a conformal coating process is a complicated process usually balancing a lot of important trade-offs and compromises.
When I consider the question I actually see three major parts of the complete process.
These parts are:
The conformal coating material
The application method
The circuit board design
When you consider these three points you have to balance them to create the best compromise process solution that suits your requirements.
It is tempting to consider one of these parts in isolation.
However, this could be a mistake.
After all, the wrong choice can be devastating to the conformal coating production process as a whole and even worse, the reliability of your product.
I feel that to identify the best conformal coating material and application process there are several key factors that you need to consider that, if you are lucky, will add up to at least one sensible process choice.
Factors to be considered include:
Temperature operating range
International, customer or National Standards
Environmental considerations of the circuit board
Requirement to rework the conformal coating
Conformal coating material type
Application process considerations
Curing the conformal coating
National, State, Regional Legislation and Insurance
