What are the alternative materials to the traditional liquid conformal coatings?

The traditional liquid conformal coatings offer great protection for the majority of circuit boards requiring protection. Between the standard coatings like the acrylic, urethane and silicone materials most problems can be prevented.

However, there are times when they just can’t do the job.

There can be various reasons that these conformal coatings can’t be used.

For example, they may not protect the electronics effectively enough due to an extreme environmental exposure. A good example is where the circuit boards are required to be waterproofed or immersed in water. In this case, the liquid coatings may be inadequate.

Another reason may be cost. The value of the circuit board may be too low versus the cost of the coating production and material. Therefore, an alternative material and process may be required that is lower in price.

water repelled from a connector due to FC coating square crop
The alternative conformal coatings like the fluoropolymers can offer different effects such as creating a hydrophobic, water repellent surface.

So what alternative coatings are there to the liquid conformal coatings?

There are many alternative coatings available to the traditional conformal coating materials that can provide extremely high protection to circuit boards.

These alternative coatings include:

  • Parylene coatings
  • Fluoropolymer coatings
  • Molecular Vapour Deposition (MVD) coatings
  • Atomic Layer Deposition (ALD) coatings

Some of these coatings offer a higher level of protection or create alternative surfaces. Others are lower in cost in production.

Nexus examines them in detail.


Need to find out more?

If further information on these topics and the key question you can go to our free eBook by clicking alternative conformal coatings 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?

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Why choosing a compatible conformal coating and equipment for your circuit board is important

I was recently at a customers facility examining their production process.They had issues with conformal coating de-wetting on their board.

The defect was occurring just after the spray application of the coating. The system being used was a selective robot applying an acrylic solvent based conformal coating.

So far so good. Nothing complex in the process. But, the de-wetting was occurring all over the circuit.

I asked if the problem had always been there?

The answer was no, it had just started to occur in the last 2-3 weeks. Hence, my being there.

So, we dug a little deeper into the process. Without going into all the details it turns out that they had changed the solder resist and this was the root cause of the problem.

The original solder resist was fine.  The conformal coating wet the surface perfectly.

However, the new solder resist had a lower surface energy and now the conformal coating was de-wetting all over the surface.

Dewetting 5 400.jpeg
The conformal coating was applied to the circuit board but would not adhere to the solder resist.

Well, the company had originally matched the material and process to the circuit board. They were compatible. They had applied a holistic approach to the process.

But, someone decided to change a material part of the circuit board. The failure came in not applying the holistic approach to check for compatibility of the three parts, the material, process and board.

This resulted in lots of scrap circuits, a defective conformal coating process and a company discussing whether to scrap a lot of bare laminates or whether they could salvage them.

How to avoid conformal coating problems?

If you are going to use a conformal coating check that all the parts are compatible. That is the material, process and board.

If you are going to change a part of the process, repeat the tests. Don’t assume the process is instantly drop in regardless of what you are told.


Need further help?

If further information on these topics and the key question you can go to our free eBook by clicking the conformal coating holistic approach 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?

 

How do you define a conformal coating failure?

When I consider circuit board failures in the field, and they are due to the conformal coating, then I immediately think of two reasons for it occurring.

The first reason is that the wrong conformal coating material was selected.That is during the material specification the wrong material was chosen and it cannot protect the circuit regardless of how it is applied.

To address this issue then the design team should consider both the holistic approach to conformal coating and the design rules for conformal coating to ensure that the right material is selected.

The second reason is that the conformal coating was applied incorrectly. That is the right material is being used but the application process is failing.

This problem in the production line leads to conformal coating failures of the confomal coating that need to examined.

Both issues lead to the circuit failing but they are very different.


If further information on these topics and the key question you can go to our free eBook by clicking conformal coating process problems 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?

 

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?

Which conformal coating standards do you need in the production process?

For conformal coating processing and inspection there are many different types of standards.

They include international, national, national trade bodies and internal company standards.

The purpose of standards is to give guidance for users on the quality of the conformal coating process.

For conformal coating standards there are two areas that they address.

These are:

  • Conformal coating manufacture
  • Conformal coating production process

These two areas are distinctly different.

Standards for conformal coating manufacture

These standards are used for the manufacture of the conformal coating.

They include:

  • MIL-I-46058C
  • Underwriters Laboratories (UL)
  • IPC-CC-830B
  • IEC 61086-1 ed2.0

These standards are used to test the quality of the conformal coating before use.

The standards can also be split in two other ways.

  • Self-Certification: Those that the manufacturer follows and completes the testing themselves on their own conformal coatings.
  • Independent: Those standards that are completed by independent laboratories on the customer coatings.

For further information click conformal coating standards now.

Standards for the conformal coating process

The standards for processing conformal coatings are used by the end user of the coating in the production environment.

They include:

  • IPC A 610 Acceptability of Electronic Assemblies
  • IPC-HDBK-830 Guidelines for Design, Selection and Application of Conformal Coatings

Both standards are self-certifying and help the production team control their conformal coating processes.


If further information on these topics and the key question you can go to our free eBook by clicking conformal coating standards 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?

 

Find out more about companies providing conformal coating equipment, materials and services with Nexus

Suppliers Section

Nexus provide a Suppliers Section for users of the site.

These are companies who provide materials, equipment or services for the thin film technologies markets.

We provide details on their products and services as well as their contact information in an easily searchable section of our website.

These sections include:

  • Supplier Directories
  • Supplier Profiles
  • Spotlight Services

Click to find out more about our Suppliers Section of our website or read about the sections below.


Supplier Directories

The directories section of Nexus that provides supplier lists by country and product.

They include directories for:

  • Independent coating services
  • Coating materials
  • Masking materials
  • Coating equipment
  • Cleaning materials
  • Cleaning equipment
  • Training and consultancy

Click to find out more.


Supplier Profile

An individual page on a coating company providing some details on what services and products they provide.

Click to find out more.

Spotlight Services

The service highlights new products coming to market that relate to thin film technologies.

Click to find out more.

Click to find out more about our Suppliers Section of our website.


 

What are the key questions to ask when cleaning for conformal coating?

Of all the questions I am asked related to cleaning the most frequent is

“Do I need to clean my circuit board before conformal coating?”.

If only it was simple to answer!

Generally, cleaning of a circuit board before conformal coating application is desirable. For Parylene this requirement may be even more important due to the bonding issues of the material.

However, it may not be essential.

Ultimately, the cleanliness of the circuit can be crucial for both the short-term production process and the long-term reliability of the circuit.

But, its difficult to know for sure if you need to clean until you complete some trials.

For the process it is difficult to know until you attempt to apply the conformal coating in production.

Then you will know immediately if you need cleaning since if you have problems you will see conformal coating defects like de-wetting, de-lamination and poor adhesion.

For the long-term reliability unless you want to wait until your product fails then some sort of reliability testing should be tried.

After all the purpose of the application of the conformal coating is to improve reliability.

It has less value unless the board is clean enough in the first place.


Other key questions in cleaning

There are many questions relating to conformal coating and cleanliness that are regularly asked.

These include:

  • What is being cleaned when circuit boards are washed?
  • How should I clean my electronic circuit board?
  • How do I validate my cleaning process?

If further information on these topics and the key question you can go to our free eBook by clicking Nexus conformal coating and cleaning.

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?