Five important facts about polyurethane (UR) conformal coatings

conformal coated PCBs Collage 640x480_NEXUS

  1. Polyurethane (UR) conformal coatings generally provide good humidity & moisture protection although not always as good as the acrylics. However, it normally is enough to protect the circuit board.
  2. Normally, urethanes are selected for their excellent chemical resistance. This is because the coatings cure rather than dry. That is they cross-link by one of many different methods including heat, UV, moisture and catalysed cure.
  3. Typically they have higher dielectric properties compared to the acrylic conformal coatings.
  4. Their chemical resistance, however, can be a limitation since rework and repair generally is more difficult than the acrylic coatings.
  5. UR coatings are normally available as either single or two-component formulations. Pot life is dependent on the cure mechanism but can be more limited than the acrylic coatings.

Need to find out more?

Click organic conformal coatings to find out about polyurethanes 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.

Why I have to clean my circuit board before conformal coating?

 

The cleaning of a printed circuit board (PCB) before conformal coating application is normally done for two key reasons:

These are:

  • Contamination removal
  • Process improvement

They have different effects on the lifetime of the circuit board but can be equally important.


Contamination removal

OLYMPUS DIGITAL CAMERA

The removal of contaminants from the surface of a printed circuit board before coating application could be important.

The contamination may be harmful and affect the long-term reliability of the circuit. Defects like corrosion can be devastating to a circuit performance in the field.

Also, applying the coating over the contamination will not necessarily improve the reliability.

Therefore, cleaning the PCB before coating could be advantageous.


Process improvement

OLYMPUS DIGITAL CAMERACleaning can aid the conformal coating application process.

It could avoid conformal coating defects like de-wetting and delamination. It can also help promote adhesion of the coating to the PCB.

The surface preparation can be extremely important, especially where some conformal coatings may have compatibility issues with the circuit board.

Therefore, cleaning a PCB before conformal coating may improve the coating quality and minimise defects.


What types of contamination may be present on a circuit board?

Cleaning is used to remove many different types of contaminants from the manufacturing and assembly processes.

They can affect the long-term reliability of the circuit after conformal coating.

The residues can come from many areas including:

  • Board laminate manufacture
  • Component manufacture
  • Soldering assembly processes (fluxes)
  • Glue and ruggedizing processes
  • Operator handling (finger prints, hair)
  • Machine contamination (oils and greases)
  • Environmental contamination (dust)

Removing the contamination may be a priority depending on their harmfulness.

How should I clean the printed circuit board?


Cleaning circuit boards before coating is a huge topic by itself.

Cleaning of a circuit before conformal coating at SCH 640_NexusSuccessful cleaning of circuits can be achieved by a variety of techniques.

These cleaning techniques include:

  • Aqueous
  • Semi-aqueous
  • Solvent & chemical
  • Plasma

The key to success in cleaning is similar to the success made with coating.

You need to match the cleaning process, materials and the circuit board together.

This will give the best results for application of the conformal coating.


How do I validate my cleaning process?

There are many techniques that can be used to measure cleanliness. They include many IPC test methods.

The techniques available include:

  • Ionic Contamination Testing (ROSE)
  • Ion Chromatography (IC) or High Performance Ion Chromatography (HPLC)
  • Surface Insulation Resistance (SIR) testing

Further information can be found in the IPC HDBK 001 on different cleanliness assessment methods or talk to us.


Need to find out more?

Click conformal coating cleaning 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.

What are conformal coating masking boots?

Nexus Image 1Masking boots are formed shapes used to cover components before conformal coating.

They are made to replace tape and dots in the conformal coating masking process for both Parylene and liquid conformal coating processes.

Using masking boots in protecting printed circuit boards (PCBs) from conformal coating application errors can be a lower cost, more reliable solution to using tapes.

The use of masking tapes, dots and liquid latex can be an effective process in protecting components from ingress of conformal coating.

However, the masking can be labour intensive, difficult and time consuming.

Masking boots can offer a labour saving alternative in both the masking and de-masking stages of the coating process. This saves time and money.

Further if the boots are recyclable then the savings can be even higher.

Three reasons to use masking boots

  1. Masking time is normally reduced. Masking boots can be 4-5 times quicker than masking tape.
  2. De-masking time is reduced. Again it is normally much quicker to remove masking boots.
  3. Masking boots are much less likely to leak. So there is potentially less damage and rework of the circuit.

This means you could save a lot of money very quickly when switching to masking boots.

Nexus Image 2
Masking boots can offer a labour saving alternative in both the masking and de-masking stages of the coating process. This saves time and money.

 Need to find out more?

Click conformal coating masking 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.

Why use plasma cleaning for cleaning circuit boards?

NEXUS 1Normally, conformal coatings must exhibit good adhesion to the PCB in order to be effective in the long term in protecting the circuit.

Therefore, the surface properties of the circuit board can be critical to the success of the coating adhesion.

Cleaning of circuit boards before conformal coating has taken place for many years.

The reasons for doing this have always remained the same:

  • Improve the surface cleanliness of the circuit to protect against corrosion and the effects of contamination on the surface from the process.
  • Improve the surface energy of the surface to improve the adhesion of conformal coating.

Traditionally, cleaning and adhesion promotion has been achieved by either using a wet chemistry treatment like washing or applying extra undercoats (priming).

Now, there are new methods and techniques appearing on the market for improving cleaning, adhesion and actually coating circuit boards differently to the traditional methods.

One of these techniques is plasma treatment.


Why use Plasma to clean circuit boards?

Here are a few key reasons to use plasma cleaning and surface treatment of printed circuit boards:

  • Plasma cleaning can clean surfaces of a product 100% to improve adhesion and surface energy of the product.
  • Many wet chemistry cleaning processes can be eliminated. Methods using cleaning chemistries, water processing and drying energy are unnecessary.
  • Activate the surface of the circuit by changing the surface energy. This allows easier bonding and better adhesion to the surface. The significant improvement in adhesion enables the use of alternative coatings that may have difficulty adhering to surfaces without the treatment.
  • The plasma process is a simple, safe and environmentally friendly technology.
  • The plasma process has both batch (offline) and inline capability.

This means the plasma process can be highly effective on printed circuit boards.


Need to find out more?

Contact us directly and we can help you with your plasma treatment requirements.

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.

The science behind Molecular vapour deposition (MVD) in protecting circuit boards

Nexus has been examining a new, novel technique that may be able to superior protection for electronic circuit boards compared to the standard coating methods like conformal coatings and Parylene but also actually be cost-effective.

This process is a hybrid ALD (Atomic Layer Deposition)/CVD (Chemical Vapor Deposition) technique called Molecular Vapor Deposition (MVD).

This method uses multiple layers of ultra-thin coatings with differing properties to build a completely protective coating.


So, why is this new coating so good compared to Parylene and other conformal coatings?

The final MVD 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.

Key performance indicators like Water Vapor Transmission Rate (WVTR), optical clarity, temperature resistance and hydrophobicity have been found to be much better than the other coatings.

Further, the really exciting part about this technology is the cost of processing that is extremely low.

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.

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.


So what does the science of Molecular Vapor Deposition coating (MVD) look like?

The actual 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. The CVD film provides the barrier protection.

First, an ALD layer is applied to the substrate. Then a CVD layer is applied. Then a further ALD layer is applied and so on.

This continues until the correct number of layers is built that has the right protection.

Description of Hybrid ALD_CVD Technology

Finally, once the required film thickness is achieved with the alternating layers, then a final hydrophobic thin film layer is applied, that combines with the ALD and CVD layers to provide a highly effective barrier.


So, just how good is the hybrid coating as a protective material for electronic circuit boards?

Generally, with protective coatings for electronics then Parylene is considered the gold standard in most cases.

So, Nexus compared Parylene with the MVD material.

Property Parylene MVD Coating
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 Nexus also identified for the material were some key properties.

  • The Water Vapor Transmission Rate (WVTR) is superior to Parylene so the coating is far more waterproof.
  • Coating adhesion is superior as it covalently bonds to the substrate. So, the lifetime of the material will be better on the circuit.
  • The temperature range of the material can be up to 350C without any degradation.
  • The hybrid coating is UV stable whereas Parylene in general is not. This is an important criteria for coatings exposed to UV light.
  • The coating stayed 100% transparent during testing (no loss of lux).
  • 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 industries like the automotive and LED sectors are looking for in protecting their circuits where cost and protection abilities are critical.


Need to find out more?

Contact us directly and we can help you with this new material.

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 you should know about Atomic Layer Deposition (ALD)

LED2

  1. ALD belongs to the family of chemical vapor deposition methods (CVD). It was initially developed for manufacturing nano-laminate insulators and zinc sulfide phosphor films for thin film electroluminescent displays. The unique properties of the coatings, together with the high repeatability, were the main factors leading to successful industrial production.
  2. The ALD deposition technique is based upon the sequential use of a gas phase chemical process. Gases are used to grow the films onto the substrate within a vacuum chamber. Through the repeated exposure to alternating gases there is a buildup of a thin film through deposition.
  3. ALD has several advantages in its use. For example, the process is self-Limiting, the films are perfectly conformal, they are pinhole free and the process allows layers or laminates.
  4. Along with advantages are a few key considerations. They include the substrate has to be of a high purity, the price of the systems are not low, the process tends to be very slow and the masking process for ALD has to be perfect.
  5. The ultra-thin films can be grown onto virtually any substrate. They have been demonstrated on highly patterned wafers, polymer films, and fine powders of most compositions. ALD is used in many different areas including microelectronics, semiconductors, photovoltaics, biotechnology, biomedical, LEDs, optics and fuel cell system technologies.

 


Need to find out more?

For further information on ALD and its performance then contact us directly or check out our section on Atomic Layer Deposition (ALD).

If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page.

 

Things you should know about Parylene

What is Parylene?

Parylene is a conformal coating that is deposited as a gas in a vacuum chamber.

It is a completely different process to the liquid conformal coatings and its properties offer advantages and disadvantages in comparison.

Parylene is a dry process compared to the standard “wet” liquid conformal coatings.

Since Parylene is deposited as a gas its thickness is almost uniform across the whole circuit board.

 

The ABCs of Parylene

Parylene is an organic polymer conformal coating that is deposited as a gas in a vacuum chamber.

Therefore, the Parylene application process is a completely different process to the liquid conformal coatings.

This gives Parylene unique properties that are not possible with the typical liquid conformal coatings normally used in electronics protection.

 

Five key facts about Parylene

  1. Parylene is the trade name for a variety of poly(p-xylylene) polymers
  2. It is a conformal coating that is deposited as a gas in a vacuum chamber. This is different to liquid conformal coatings.
  3. The Parylene film is created via a controlled Chemical Vapor Deposition (CVD) process.
  4. It is a dry process compared to the standard “wet” liquid conformal coatings.
  5. This process makes Parylene a highly effective moisture and dielectric barrier that outperforms most liquid conformal coatings.

 

Three important points you should know about Parylene

  1. Parylene has unique properties that are not possible with the liquid conformal coatings.
  2. Parylene is a conformal coating that is deposited as a gas in a vacuum chamber.
  3. This is different to liquid conformal coatings that can be brushed, dipped or sprayed.

Nexus Conformal Coating Research Program

Nexus, an independent conformal coating resource company, have launched an Independent Conformal Coating Research Project starting in September 2012. Why should your company take part?
Nexus is conducting a world-first, independent analysis of the most popular commercially available conformal coating materials and combining the data with the various application methods used to apply them, to provide you an unparalleled level of knowledge and insight.
The Research Program will be structured over two years and broken into 3 phases. The Research Program will look at all areas of conformal coating, cleaning and related reliability.
 

Phase 1: Conformal Coating Materials and Equipment Benchmarking

In an effort to answer these questions and many more Nexus will begin Phase 1 of a full ongoing Research Program in August. This Research will identify the best conformal coating materials, conformal coating application processes and ultimately value for money for customers in the world of electronics printed circuit board protection.

  • Upon completion of the research you will know:
  • Whether your Conformal Coating Material is the best available for your application including well known acrylic, urethane, silicone liquid conformal coatings and parylene coatings.
  • Whether your application process is giving you the best results from your material
  • Whether there is a significant difference in protection provided by the various conformal coating equipment and application methods
  • Just how good the new environmentally friendly conformal coatings are
  • Optimise your commercial costs through using the right conformal coating materials and equipment
  • Which materials and processes you should be considering for your new projects

To find out more click Two Year Conformal Coating Research Program

Click here to find out Why you should take part in the Conformal coating Research Program.

Why Should Nexus Carry Out Conformal Coating Research Now?

 The interest in, awareness of and need for conformal coating has never been greater.  With the continued drive towards miniaturisation, increased performance expectations among users and the ever more diverse and unexpected operating environments encountered, increasing the reliability of electronic assemblies becomes increasingly more of a challenge.
Conformal coatings have long been used in military and aerospace environments, and more recently have become more prevalent in automotive electronics as an additional level of protection to prevent corrosion and other failures due to humidity and condensation.  Increasingly, however, industrial control electronics and even consumer devices require coating to survive their warranty period, and provide a consumer acceptable lifetime.
Increasingly, western designed electronics are being manufactured and sold in developing economies, and encountering operating environments for which they were not designed, with high levels of humidity and pollution, resulting in some fairly corrosive operating environments.  Many OEM’s have encountered these kinds of issues, and often, the addition of a protective layer of conformal coating has been a more cost-effective solution than redesigning the device, electronics and or enclosures.
A Tale of Two Countries
One OEM of which we are aware had a monthly warranty claim in India alone of $600,000, for a mature, uncoated product design that had warranty claims in the region of $10,000 per year in North America.  The company’s brand image was suffering and senior management was ‘deeply concerned with finding a solution’.
One year after instigating a conformal coating process, this OEM now has warranty claims of under $10,000 in India.  The OEM achieved an ROI of greater than 60%, with a less than two month payback.  The Senior Leadership team is delighted, the operations manager responsible for the implementation was promoted to a global corporate role and they are looking to implement coating on all new designs and adopting a ‘design for coating’ mantra, based on their experiences over the last year.  All in all, a total success story?
Well not quite.  It took them three months to identify and prove the root cause failure mechanism was corrosion due to the cocktail of sulfides and nitroxides, present in significant quantities in the polluted indian cities, mixing with humidity and condensing as acidic solutions on the electronics, in a similar fashion to the ‘acid rain’ phenomenon so familiar in the west.
After they had diagnosed the failure mechanism, it took them two more months to decide on conformal coating, rather than changing the housing, gasketing the housing or potting as solutions.  Then they decided to adopt the conformal coating used by their parent company on the basis ‘if it was  tested and found good enough for them, it would be good enough for us’.
They then coated assemblies for test, by hand using an aerosol spray can, and ran them through a 3 month much shortened verification campaign, at the end of which all the units bar one had failed dismally.  2 weeks later they had a failure report which attributed most of the failures to either ‘the conformal coating material was not able to protect the circuit from the test environment’ or that ‘poor coverage and bad application technique were responsible for the failures’.
The engineering team gets smart
Thankfully, the failure analysis brought the operations team into the equation, since if the application method was important, then that should be considered as part of the solution.  The operations team got the selective coating equipment suppliers involved, and a partnership with the conformal coating material supplier was formed.
The manufacturers of the materials and equipment provided some actionable input, and a new set of assemblies was coated with a robot and a different (much more expensive) material and  subjected to the test regime.
Three months later all of the test units had survived the accelerated test, the material was fast-tracked through the corporate qualification program (another two months) since it was unknown and untested by them, and the implementation program began with another two month lead time on production equipment.
The real cost of implementation
The OEM had still been stuck with the warranty claims throughout the process development of nearly one year (approx $7,200,000)
Laboratory testing at an outsourced laboratory for the 6 months of actual validation, the expedited failure analysis report and the cost of corporate qualification cost the program close to $500,000
The overhead cost of the project team with an equivalent ten full-time members ran to nearly $1,000,000
The opportunity cost was unmeasured, but the same team were required to solve a soldering defect which was deferred.
The damage to the brand reputation of the additional year’s field failures and warranty returns.
The capital equipment for five production lines ran to $600,000
The material expenditure ran at $300,000 per annum
Total Investment = $9,300,000
Payback = 31 Months
3 Yr Return = 1%
5 Yr Return = 4%
Of course, the big number here is the length of time during which they continued to field warranty claims (and pay the project team, and an extra set of lab tests and more delay due to the false start with the original material and application method).  The selection of which was based on a bad assumption, and could very well be made again.  Was it the material or was it the application method that caused the failures in the first round of testing?  Is there a way to separate the two?  Does this dilemma sound familiar?
Is there a better way?
Conformal Coating is a process, not a material.  Not all materials and processes are created equally.  When it comes to increasing the reliability of your printed circuit assemblies in harsh operating conditions, you need to know which conformal coating materials and application processes provide the best levels of protection for your assembly.
Nexus, THE conformal coating consulting company, is conducting a world-first, independent research analysis of the most popular commercially available conformal coating materials and the various application methods used to apply them, to provide you an unparalleled level of knowledge and insight.  Upon completion of the research you will know:
• Whether your material is the best available or most suitable for your application
• Whether your conformal coating application process is giving you the best results from your material
• Whether there is a significant difference in protection provided by the various application methods.
• Which materials and processes you should be considering for your new (or legacy) projects.
Had the OEM team been armed with this report, they would have known that the initial conformal coating material selection and application method was or was not suitable and could have saved half of the time (and  $4,500,000) they spent on this project, reducing the payback by seven months to 24 months, improving returns to a more respectable 5% and 9%, reducing the damage to their brand reputation and moved onto solving the solder defect quicker, thus compounding their savings.

Just how good are the new environmentally friendly conformal coatings? Nexus Can answer this….

In an effort to answer this question and many more Nexus will begin Phase 1 of a full ongoing Conformal Coating Research Program in August.

This Research will identify the best conformal coating materials, conformal coating application processes and ultimately value for money for customers in the world of electronics printed circuit board protection.

The First Phase of the Research will:

  • Compare and rank the protective capability of a number new and well established conformal coatings including both liquid and parylene based materials, against single aggressive environments as well as the sequential load to provide a reliability enhancement index.
  • Compare and rank the performance capability of the commercial application methods including selective spraying, batch spraying, dipping and brushing.
  • Provide a cost comparison of coated assemblies and determine cost-benefit comparisons between coating materials and application processes combinations.

This research will be open to join by users and suppliers alike who wish to access the full unabridged data.

For further information on how to join the Program visit Nexus