Factors to consider when setting up a conformal coating production line for printed circuit boards

The conformal coating production line, whether it is an operator manually brush coating printed circuit boards (PCBs) or an inline robotic spray coating process is typically made up of several stages.

However, not all the stages are mandatory or may be required. These stages are shown below:

 

Chart

Consider each stage below.


Boards In / Boards Out

This is very straightforward. The PCBs are delivered to the conformal coating area ready for processing.


Inspection

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Inspecting the circuit boards before starting the conformal coating application process starts helps avoid stopping the line if there is a problem.

The initial inspection process can also identify which PCBs are to be coated, the material to be used and how they are to be coated.

This can be done automatically as part of the production process or completed by the operator.


Cleaning

Cleaning the circuit boards before application of conformal coating may or may not be required.

This is a decision that should be made earlier on in the design stage before production actually starts.

However, if you do decide to clean then consider these guidelines:

  • Ensure that the cleaning process does not add more contaminants to the PCB than it started with due to entrapment of cleaning fluids.
  • Make sure the PCBs are dry enough for the conformal coating process and the cleaning process not leave water entrapped under components that could impede the application.
  • Ensure the cleaning process actually removes residues that may cause defects like de-wetting to minimise finishing at the end of the process.

Again, cleaning is for the engineers to decide.  The option of whether you need to clean your circuit boards for conformal coating is a whole topic on its own.


Masking

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Masking may not be required on the circuit board.  However, generally there are very few circuit board assemblies that can be completely coated and have no areas that must not be conformal coated.

Some components on PCBs generally need to avoid having conformal coating applied to them.

This leaves three options:

  1. You can avoid coating the component or area using a selective application process.
  2. You can apply some form of masking that the conformal coating can be applied to and remove the masking materials after application.
  3. You can apply a conformal coating that does not need masking against.

Again, engineers need to consider their options on whether to use conformal coating masking as soon as possible.


Pre-Coating Inspection

Generally, it is more efficient to double check the masking process is correct before conformal coating application rather than repair the PCB after the process goes wrong because the masking process was incorrect.

This check can be manual or automated but it is highly valuable.


Coating Application

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The one stage that cannot be avoided is the conformal coating applied to the PCB.

There are many different methods for applying conformal coatings and probably the most important factor in all of them is training. The operator needs to understand the process to be able to work correctly.


Drying and Curing

A conformal coating is a wet process (unless you use Parylene) and therefore the coating has to dry.

The difference between drying and curing in conformal coating is very different. However the process required depends on the conformal coating itself.

Care needs to be taken in deciding how to achieve the right result.


De-masking

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Like masking, there is skill in removing the masking materials from the circuit board and not damaging the coating.

This is also where touch up (finishing) is carried out to ensure the final finished PCB is fit to pass the inspection criteria.

Work instructions are needed along with training on the specific methods of finishing to ensure this can be achieved.

Again, the work environment can be critical to achieve the right results.


Inspection

When the PCB is conformal coated and finished, you need to know if the product meets the inspection criteria.

The conformal coating inspection process can be done manually or automatically. This can depend on the volume of PCBs and the level of sophistication required.

Again, it is down to operator training and using the right equipment to ensure that this is possible.

Also, at this stage it is possible to measure process factors like coating conformal thickness to check that the criteria are met.


Other factors to consider

The set up of a conformal coating production line regardless of the application method has many similar characteristics.

General requirements

Any coating facility will need the basic requirements put in place that would be standard for any piece of electronic manufacturing process. These include ESD systems, facilities for the machines, the environmental requirements and the normal Health & Safety (HSE) considerations.

Health & Safety (HSE)

HSE tends to be more important for conformal coatings since in general the coatings themselves are hazardous, or the way they are applied makes them potentially harmful to operators

Environment

Conformal coatings are sensitive to the environment that they are processed. Cleanliness could be critical, as can temperature and humidity.


Summary

Setting up a conformal coating production facility can be a straightforward process as long as all factors are considered.

Get this right and many of the problems that could occur during production will be avoided.


Need to find out more?

Click conformal coating production processes for 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.r

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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
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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 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.

Nexus Series of Webinars: Conformal Coating Rework, Repair and In Process Application

Nexus are to hold a series of webinars on conformal coating topics in the Autumn of 2012.The series of four online conformal coating webinars will cover the following topics and each last 90 min. The last of the online training webinars will be:

Rework, Repair & In Process Application
Monday 4th February Rework of coating boards is a skilled job to obtain the optimum product reliability. Different materials or thicker coating may require different techniques to maintain the same reliability provided by the original coating system. It’s not always possible to use the same coating system in a rework situation so what are the alternatives?

Topics will include:

Material identification
Conformal Coating removal techniques
Cleaning & preparation
What coatings are compatible?
Re-coating assemblies after rework
Inspection of coatings after rework

Please click online conformal coating webinars for further information.

Nexus Conformal Coating Video Library: An operator carrying out a Conformal Coating Adhesion Test on a conformal coating on a printed circuit board (PCB)

Nexus, the Conformal Coating Resource, have a section which has videos showing processes for conformal coating and also company video’s of which Nexus feels offer technical information to users of conformal coating.

This video shows an operator carrying out a Conformal Coating Adhesion Test on a conformal coating on a printed circuit board (PCB)

Click through to see the full range of Conformal Coating Videos at the Nexus Website.

Nexus Series of Webinars: Conformal Coating Inspection and Quality of Coated Board Assemblies

Nexus are to hold a series of webinars on conformal coating topics in the Autumn of 2012.The series of four online conformal coating webinars will cover the following topics and each last 90 min. The third of the online training webinars will be:
Inspection & Quality of Coated Board Assemblies
Monday 7th January

Conformal Coating Inspection standards exist from a variety of sources and are based mostly on practical experience. There are many cosmetic defects that are reworked in industry which are unlikely to actually impact on product quality. The majority of coated products are inspected manually but with the growing use of coating application in high volume, automatic optical inspection is gaining in popularity.

Topics will include:

Inspection standards and what is important
Understanding some of the coating terminology
Manual & automated inspection
Common process defects & why they occur
Recording & charting defects in a process
Cosmetic process indicators

Please click online conformal coating webinars for further information.

Nexus Conformal Coating Video Library: Operator masking a DIN connector with masking tape ready for the Conformal Coating application process

Nexus, the Conformal Coating Resource, have a section which has videos showing processes for conformal coating and also company video’s of which Nexus feels offer technical information to users of conformal coating.

This video shows An operator masking a DIN connector with masking tape ready for the Conformal Coating application process

Click through to see the full range of Conformal Coating Videos at the Nexus Website.