How was the Molecular vapor deposition (MVD) technology for protecting electronic circuit boards developed?

Nexus has been examining Molecular Vapor Deposition (MVD), a new novel coating technique that may be able to offer superior protection to electronic circuit boards compared to the standard coating technologies like conformal coatings and Parylene.

The MVD process is a hybrid ALD (Atomic Layer Deposition) / CVD (Chemical Vapor Deposition) technique that uses multiple layers of ultra-thin coatings with differing properties to build a completely protective coating.

The results are proving to be highly effective and could change the industry in time.


But where did the MVD technology come from originally?

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The Molecular Vapor Deposition (MVD®) process was found in 2003 by the SPTS MVD group located in San Jose, California.

SPTS provided nano-film technology processing, equipment and coating services, supplying to multiple markets including:

  • MEMS (Microelectromechanical systems)
  • Semiconductors
  • Industrial Inkjet Heads
  • Display Technology
  • Advanced Packaging
  • Data Storage Industry
  • Biomedical
  • Genome Sequencing
  • µfluidics

How is the MVD coating process used in the different industries?

The MVD process provides low temperature vapor deposition of coatings with many different properties in many sectors.

Consider the examples of MVD coating use below:

Surface Energy Control

  • Anti-stiction
  • Hydrophobic
  • Hydrophilic
  • Oleophobic
  • Oleophilic
  • Lubrication
  • Bio-functional layer

Device Protection / Package Sealing

  • Moisture barrier
  • Corrosion barrier
  • Chemical barrier
  • Gas/Oxygen barrier

Optical Films

  • Anti-reflection coatings

 Dielectric Films

  • Electrical insulation
  • Conformal films on high A/R

Adhesion

  • Adhesion promotion
  • Improved thermal stability
  • Improved mechanical durability

The MVD process offers great flexibility of processing thin films and it has now been considered for electronics protection.


Need to find out more?

Click Molecular Vapor Deposition (MVD) for protecting electronics 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 sectors are polyurethane conformal coatings used to protect electronic circuit boards?

 

NEXUS1Polyurethane conformal coatings are used in nearly all sectors where electronic circuit boards are used including:

  1. Aerospace
  2. Defence
  3. Marine
  4. Transport
  5. Automotive
  6. Control drives
  7. Industrial electronics
  8. LEDs
  9. Telecommunications
  10. Mobile technology
  11. White goods

In fact there are few sectors they are not used.


Why use a polyurethane conformal coating in electronics protection?

Conformal coatings made from polyurethane resin are part of the organic family of coating materials that also includes the acrylic and epoxy materials.

All organic conformal coating materials provide good humidity & moisture protection.

What differentiates the polyurethane coating from the other coatings like the acrylic resins is that the urethanes also offer high chemical resistance.

This makes them excellent conformal coatings where chemical attack is a potential hazard for the electronic circuit.


Need to find out more?

Click polyurethane conformal coatings as part of the organic coatings 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.

The ABCs of Parylene coating for electronic circuit boards

NEXUSParylene is a conformal coating that can be applied to electronic circuit board assemblies that is deposited as a gas in a vacuum chamber.

It is a completely different process to the normal liquid conformal coatings that are applied by alternative methods such as dip, brush and spray.

This difference means Parylene offer advantages and disadvantages in comparison.

For Parylene coating and electronics here are six key areas to consider.

These are:

Click on each link to find out more Parylene, the process and its properties.


Need to find out more?

Click Parylene conformal coating for electronics 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.

Do you need UL qualification for your conformal coating?

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What is UL and how does it relate to conformal coating?

UL stands for Underwriter Laboratories. They are a global safety certification body for consumer electronics.

When a conformal coating states that it has a UL qualification, it means that the material has been independently tested by UL in one of their laboratories and passed a particular standard.

UL carry out the testing. It is independent. There is no self-certification available.

UL qualified conformal coatings are used in all areas of electronics protection including aerospace, industrial controls, automotive and telecommunication sectors.


What UL standard tests are used with conformal coating?

For conformal coating materials there are two standard tests typically used.

These are UL94 and UL 746E.

UL 94 Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing.

UL 94 is a plastic material flammability standard. It classifies plastics according to how they burn in various orientations and thicknesses.

UL 94 measures a conformal coating material’s ability to extinguish or to spread the flame once a test specimen has been ignited.

This ability is ranked as a classification as below.

Classifications

For conformal coatings the coupons are normally tested Horizontally (HB).

Tests are normally conducted on coupons of the minimum approved thickness with different types of laminate.

The conformal coating thickness range also is normally specified.

  • V-2 burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.
  • V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
  • V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

Most conformal coatings aim to achieve V-0 status.

UL 746E Standard Polymeric Materials: Industrial Laminates, Filament Wound Tubing, Vulcanized Fiber and Materials Used in Printed-Wiring Boards

The UL 746 test measures the resistance of the conformal coating to electrical ignition sources.

The conformal coating material’s resistance to ignition and surface tracking characteristics is described in UL 746E.


Need to find out more?

Click UL standards and conformal coating for further information on whether you need UL qualified conformal coatings 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 the different techniques for cleaning a circuit board before conformal coating application?

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Cleaning circuit boards before conformal coating is a huge topic by itself. This is because cleaning circuit boards can be challenging.

However, successful cleaning of electronic circuits can be achieved by a variety of techniques.

The main methods of cleaning can include:
• Aqueous wash
• Semi-aqueous wash
• Solvent & chemical wash
• Plasma cleaning

The key to success in cleaning circuit boards is similar to the success made with conformal coating. You need to match the cleaning process, the cleaning materials and the circuit board together.

If you do this then this will give you the best results for cleaning the circuit board assembly.


Why clean circuit boards 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.


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.

The residues can come from:
• 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.


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.

How do I selective apply my conformal coating without using masking?

Selective spraying of conformal coating using an automated robot system is one of the widest used application methods in high volume processing.

The principle is that the conformal coating is applied selectively by a small spray gun to the circuit board to the areas requiring coating only.

The selective process deliberately does not apply the conformal coating to areas that normally require masking such as connectors and other components.

This selective application of the conformal coating to the circuit board can avoid using a time consuming masking process and costs can normally be reduced.


What equipment do you need for selective spraying?

A specialist robotic system designed for application of conformal coatings is normally required for selective coating.

The robotic system will be fitted with various conformal coating spray valves that apply the different types of conformal coating material to the circuit board using different spray patterns.

The level of movement of the robot can vary with systems having three, four, five and even six axes of movement for the spray valves.

Want to find out more about application of conformal coatings to circuit boards by selective robots?

Click to find out more about questions such as:

  1. What equipment do you need for selective spraying?
  2. What specialist valves are required for applying different types of conformal coating?
  3. Which conformal coatings can be used in selective spraying?
  4. Is selective spraying of conformal coating a complex process?
  5. How cost effective is selective spraying of conformal coating as a process?
  6. What variables control the quality of the conformal coating finish in selective spraying?
  7. What are five advantages of the selective spray conformal coating process?
  8. What are five disadvantages of the selective spray conformal coating process?

Need to find out more?

Go directly to our conformal coating selective spray application section 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.

Images 1 and 2 courtesy of PVA (Precision Valve Automation).

How do I spray coat my printed circuit board with conformal coating?

Nexus 1Batch spraying of conformal coating on printed circuit board assemblies (PCBA) is one of the most widely used techniques in low and medium volume production processing.

Typically, using either a compressed air spray gun or an aerosol, the conformal coating is sprayed across the whole of the circuit board to provide the protection it requires.

The batch spray process can produce a high quality conformal coating finish that gives the best protection due to good tip edge coverage of components.

However, it is not a selective process and all parts are coated on the circuit board.

Therefore, masking may be required to protect components that must not be conformal coated.


What is a typical spray process for application of the conformal coating to the circuit board?

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Batch spraying using an aerosol or hand spray gun is normally a simple process.

A typical method of application for spraying is as follows:

  1. Dilute the conformal coating with thinners according to the manufacturers recommended instructions (typically the viscosity is close to 24cps and almost like water).
  2. Mix the blend thoroughly but without creating bubbles (if bubbles occur wait for them to dissipate) and apply a test pattern to ensure the material from the spray gun is flowing properly.
  3. If “spider webs” occur (similar to candy floss in the air) then dilute further with more thinning solvents.
  4. Position the circuit board horizontally
in front of the spray gun operator.
  5. Hold the spray gun at a 45° angle and at the recommended distance (typically 20 to 25 cm from the circuit board).
  6. Spray a thin and uniform coat onto the circuit board with an even motion using “spray and release” strokes in a raster pattern. Do not over apply too much liquid.
  7. Turn the circuit board 90°and repeat until the board has completed one complete 360° rotation.
  8. If a second coat is required, wait 2-3 minutes (may be longer with certain solvent types so check manufacturers recommended instructions) and repeat steps 5-7.

Once complete follow the cure instructions for the coating on the circuit board.


Need to find out more?

Go directly to our conformal coating batch spraying section 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.