What type of problems can you have with conformal coating?

Normally, when I am working with customers I see two types of problems.

Those are problems relating to the conformal coating process and those relating to the actual product reliability.

They are two very different issues to deal with.

Conformal coating reliability problems

Ultimately, there are many factors that can affect the short, medium and long-term reliability of a circuit board.

It is not just the conformal coating that can influence this.

However, if the conformal coating material is not correctly specified at the reliability design stage then this could be the major issue and the reason for failure.

Once the product reliability requirements have been defined as part of the conformal coating design procedure then the resulting information needs to be combined with the data from the conformal coating holistic approach.

This will ensure that the risks of a failure due to the conformal coating are minimised.

if the conformal coating material is not correctly specified at the reliability design stage then this could be the major issue and the reason for failure.
If the conformal coating material is not correctly specified at the reliability design stage then this could be the major issue and the reason for failure.

Conformal coating process problems

Typical failure mechanisms in conformal coating processing normally come from the conformal coating masking process or the application process.

Conformal coating masking failures

Failures in the masking process are generally a known quantity and easy to understand.

Adopting best practice methods for conformal coating masking can help to minimise these problems.

Masking with tape and latex 1 600
Using best masking techniques can minimise some problems found in conformal coating processing

Conformal coating application failures

Failures in the conformal coating application process are very well understood.

Typical failure mechanisms include:

  • Bubbles
  • Blushing
  • Contamination
  • Capillary Flow
  • Orange Peel
  • Shadowing
  • Cracking
  • Delamination
  • De-wetting
  • Fish Eyes

Understanding and troubleshooting why these conformal coating failures occur can quickly lead to a solution to the failure in the conformal coating process.


Need help with your conformal coating process?

Contact Nexus now and let us show you how we can help you.


Dr Lee Hitchens, Author of Nexus website and ebook

Dr Lee Hitchens is the Author of the Nexus eBook and a main contributor to Nexus.

 

Advertisements

Read Part 3 of our Series, “Key fundamental challenges in conformal coating production”, and understand how Staff affect conformal coating production

Selective Coating HR CROP 3How do staff interaction with the production process and affect the results?

When considering staff we are talking about everyone involved in the process. That is operators, technicians, supervisors and process engineers. For staff then there are three key areas. These can be considered as training, operation and troubleshooting.

Nexus takes a look at each of the areas individually.

click Staff and their affect on Conformal Coating Production  to find out more

Nexus Newsletter Feature So you are considering outsourcing your conformal coating to a subcontract coating house.

Subcontracting out your conformal coating process to a third party can be a great solution or a complete disaster. Nexus have written a detailed article on all the points that should be considered before you take that step and outsource your conformal coating process.  Check out the feature and ensure you don’t make a critical error.

Ask The Expert: Dr Lee Hitchens, Nexus on Key Conformal Coating Material Challenges

“Out of all the Key Material Challenges I see on a regular basis, one of the most prolific is difficulties in adhesion to solder resist or to no clean residues and contaminants.“
 “It can be as basic as the coating just will not stick to the PCB or it runs away from areas on the PCB. At other times, it’s interpreting just how well the coating is stuck and determining if it’s good enough for the customer? Normally, this cannot be answered instantly and leads to some serious thinking!”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating material challenges.

Ask The Expert: Karl Hardcastle, SCH Services Ltd, Subcontract Conformal Coating Service on Key Conformal Coating Material Challenges

“One of the biggest issues we face is availability of the materials. As a subcontract coating house we generally have to use the coating selected by the customer. This can have dramatic issues occasionally when lead times on products can stretch into weeks or months and the customer wants the product now!”
“Conformal coating is one of the last processes on the PCB. Coating houses are normally making up the time lost in other areas. If you can plan the production to coincide with the material supply chain it’s a great help!”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating material challenges.

Ask The Expert: Gordon Watson, SMS Automation, Conformal Coating Equipment on Key Conformal Coating Material Challenges

“Our greatest Challenge is establishing good communication at an early stage with the key decision makers to determine the critical factors such as material specification, performance and requirements. Customers should also think of future needs when discussing conformal coating application systems rather than limit their choices to what is available on a standard machine.”

“Our skill is in combining machine building and automation skills with knowledge of the process of conformal coating and so it is important that we obtain a thorough understanding of our customers’ requirements and quickly formalise them into a  plan as quickly as possible.”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating material challenges.

Ask The Expert: Frank Hart, Sales and Marketing Director, PVA Conformal Coating Robotic Systems on Key Conformal Coating Material Challenges

“There has been much segmentation in the coating industry and this has driven chemical companies to the most prominent current trend in the marketplace, customization.  No longer is one coating chemistry versatile enough for the changing demands of the consumer.  It is no longer unusual to take a long standing coating material and have 8-10 versions of the formulation on the market.  Viscosity modifications, sometimes from 20 cps all the way to a non-slumping gel version, tend to be the most popular.  If you are looking to modify the flow characteristics, limit wicking into keep out areas, produce a dam, or control the solvent to resin ratio, there is typically a product tailored to your requirements.”

“Maybe the appearance of the coating is of greater importance to the end user.  This can be as radical as the physical color of the coating itself or maybe just the level of fluorescence under black light.  Some end users do specify the coating needs to be visible to the operator from a predetermined distance from the application, or perhaps they are using an automated AOI system.  Maybe your technology is proprietary to the point that an opaque coating protects your design in lieu of clear transparent materials.  Such requirements may drive an end user to request a custom formulation with these properties.”

“No matter what the request may be, from appearance to viscosity, to the cure mechanism or even changing the solvent carrier to a VOC friendly alternative, customizing formulations has become the norm more than the exception and chemical manufacturers are marketing these products as standard solutions.  End users should always work with formulators to assure that any modification to the original chemistry does not affect performance properties such as adhesion, protection, or curing. From an application standpoint, having your chemistry slightly altered may affect a variety of process parameters so always consult your material manufacturer and equipment manufacturer’s applications experts prior to making any formulation change.  In an automated process the changes may be as simple as modifying the robot speed or adjusting the path spacing to compensate for the new flow characteristics, or it may require a complete redesign of the fluid system and spray/dispensing valves….  But these factors can always be pre-qualified in a test laboratory.”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating material challenges.