What is a hydrophobic acrylic conformal coating?

alternative, Blog, conformal coating

Nano-coating fluoropolymers Collage 640_SCH UK

There are several reasons for using a conformal coating or Parylene to protect a printed circuit board (PCB).

They include:

  • High insulation protection
  • High moisture and humidity protection
  • Chemical and temperature resistance
  • Ruggedisation
  • Improve dielectric properties
  • Barrier protection against particulates

However, one property that most liquid conformal coatings do not possess that is extremely useful to have is being water repellent or hydrophobic.

A coating that is hydrophobic repels water from the surface by changing the surface energy of the coating.

This makes it energetically unfavourable for the water to wet the surface. Hence, the water “balls up” and rolls off the surface.

This occurs in the fluorinated nano-coatings that are hydrophobic and is an extremely useful property when protecting a circuit board where water may be present.

However, typical conformal coatings are not hydrophobic.

Materials like acrylics and polyurethane coatings are excellent against moisture but not so good as water repellent materials. They do not have a low surface energy.

Conformal coatings like acrylics and urethanes do not have water repellent properties (left). A hydrophobic conformal coating repels the water and does not allow it to wet the surface (right).
Conformal coatings like acrylics and urethanes do not have water repellent properties (left). A hydrophobic conformal coating repels the water and does not allow it to wet the surface (right).

A hydrophobic acrylic conformal coating – the best of both coatings

Now, there exists a hybrid acrylic coating that has both the properties of an acrylic conformal coating at the same thickness plus the benefits of a hydrophobic nano-coating.

These benefits include:

  • Hydrophobic (water repellent) surface
  • High Insulation protection
  • High moisture and humidity protection
  • Ruggedisation
  • Improved dielectric properties
  • Barrier protection against particulates

This new range of conformal coatings can now offer the best properties of both without any cost penalty.

The water wets the surface (left) on a normal acrylic conformal coating. A hydrophobic acrylic conformal coating, with a low surface energy, makes water de-wet from the surface (right) and still has all the benefits of the acrylic conformal coating.
The water wets the surface (left) on a normal acrylic conformal coating. A hydrophobic acrylic conformal coating, with a low surface energy, makes water de-wet from the surface (right) and still has all the benefits of the acrylic conformal coating.

Find out how we can help you with your acrylic hydrophobic coatings now.

Contact us to discuss your needs and let us explain how our hydrophobic coatings could work for you.

Contact us now.

How do I spray coat my conformal coating?

Blog, conformal coating

 

SCH UK Image 3conformal coating batch spraying Collage 640x480

Batch spraying is one of the widest used techniques used in low and medium volume conformal coating processing.

Whether you are using a compressed air spray gun or an aerosol can, the conformal coating is sprayed across the whole of the circuit board.

It can produce a high quality coating finish that gives the best protection due to good edge coverage.

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

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

What equipment do you need for batch conformal coating spraying?

SCHUK Image 2

If you are not using aerosols then for conformal coating spraying a typical set up is:

  • Spray gun
  • Air Compressor for the Air Supply
  • Spray booth

This is a low cost set up that can handle a fairly high volume of product.

However, the quality of the finish is dependent on the quality of the spray equipment itself and the operator.

How do you apply the conformal coating by spraying?

Although the process can be material specific there are a few general guidelines for applying conformal coating by spraying.

These include:

  • Only apply thin, consistent coats. It may be necessary to apply more than one coat.
  • Apply the coating in a narrow raster pattern across the circuit.
  • Rotate the board 90 degrees and repeat. Continue until the whole board is coated to avoid 3D effects.
  • Allow the coating to dry enough to avoid problems like bubbles before applying a second coat.

Following a few simple guidelines can save a lot of problems.

What variables control the quality of the conformal coating in batch spraying?

SCHUK Image 1

Variables that influence the quality of the coating process in spraying are:

  • The operator skill
  • Quality of the spray equipment
  • Viscosity of the conformal coating
  • Blending the conformal coating to the right viscosity is critical.
  • The level of masking required

Find out how we can help you with your conformal coatings now.

Contact us to discuss your needs and let us explain how hydrophobic coatings could work for you.

Contact us now.

 

The ABCs of ultra-thin fluoropolymer coatings for electronic circuit boards

alternative, Blog, conformal coating, Fluoropolymer

 

Nano coatings are no mask conformal coatings with great water repellent properties

What is a fluoropolymer coating?

A fluoropolymer coating is typically comprised of fluorocarbons and characterised by carbon-fluorine bonds.

They have many interesting properties and especially for printed circuit boards.

However the three key properties for electronics are that the coatings are:

  • Hydrophobic
  • Chemically resistant
  • No masking required

These properties can be key to protecting the electronics and providing a highly cost effective production process.

Hydrophobic coating

Fluorocarbons are not susceptible to Van der Waals force.

This gives the coatings their signature characteristics. That is they are non-stick, hydrophobic and friction reducing.

Therefore, water does not like to wet the surface of the circuit board and this gives the circuit excellent protection.

Chemically Resistant

These fluorinated coatings are chemically inert.

Owing to the fluorine bonds, fluoropolymer coatings demonstrate a high level of durability as well as resistance to acids, bases and most solvents.

This gives the circuit board a high degree of protection from chemical attack.

No masking required

Finally, what is really interesting is that these properties are exhibited at ultra-thin film thicknesses.

Typically a dry film can be 1-2um or even less.

This means that masking generally is not required for circuit boards before application.  Therefore, you can dip the whole product into the liquid and there is no issue with electrical contact.

This can lead to significant cost savings in production.

What other properties do the fluoropolymer coatings have that may be relevant in electronics?

SCHUK 2

As already mentioned these hydrophobic coatings have very specialised properties.

They can include:

  • Being highly hydrophobic (water repellent)
  • Having a high moisture barrier
  • Requiring no masking before application
  • Being highly oleophobic (oil repellent)
  • Having a high chemical resistance
  • Having a high lubricity
  • Having high dielectric properties
  • Providing high corrosion resistance
  • Providing good abrasion / wear resistance

Note, not all fluoropolymer coatings have all of the above properties. But, some coatings can in fact have almost all of the properties.

The fluoropolymer coatings are extremely flexible coatings and becoming more prolifically used throughout engineering.

What sectors of industry are fluoropolymer coatings being used in protecting electronics?

SCHUK3

Fluorinated coatings are used to protect electronics in almost all industrial sectors.

They include:

  • Aviation
  • Aerospace
  • Defence
  • Automotive
  • Industrial
  • Oil & Gas
  • LEDs
  • Medical
  • Optics
  • Telecommunications
  • White goods / Commercial

This list is limited and there are a lot more areas that they are used.

What are the major differences between a fluoropolymer coating and a conformal coating for protecting an electronic printed circuit board or assembly?

There are several key differences between a conformal coating and a fluoropolymer coating.

They include:

  • Hydrophobic Properties – A fluoropolymer coating is generally hydrophobic in nature. It repels water when the water is on the surface of the coating.
  • Extremely thin coating – The fluoropolymer coating is normally applied a lot thinner than a typical liquid conformal coating. This is due to its superior performance when repels liquids
  • No masking – Due to the extremely thin fluoropolymer coating applied (<1-2um), the components that normally require protecting (connectors, switches etc) from the insulating liquid conformal coating may not need to be masked for the fluoropolymer. The circuit board can be completely submerged in the liquid with no masking applied without fear of damaging the connections.
  • Simple process – No masking means an extremely fast application process
  • Fast drying – due to the thin nature of the fluoropolymer coating and the solvents normally used the coating dries extremely quickly.

Find out how we can help you with your ultra-thin hydrophobic coatings now.

Contact us to discuss your needs and let us explain how hydrophobic coatings could work for you.

Contact us now.

How thick should I apply my conformal coating?

Blog, conformal coating

So, here is a question I am regularly asked. How thick should the conformal coating be on the circuit board?

Well, the simple answer is thick enough so the conformal coating works and protects the circuit board.

But not too thick as this can cause problems for the circuit board in the long term.

After all, the performance of the conformal coating is dependent on the thickness applied.

But, it is possible to quantify this a little more.

Help for determining the right conformal coating thickness

First off it’s probably best to use guidelines from International Standards like IPC A 610.

These standards specify the conformal coating thickness based upon the generic material types like acrylics, polyurethanes, and silicones.

Further, you can also reference this data against the material manufacturers technical recommendations.

Combining these two pieces of information should give you a target range for the conformal coating thickness.

However, ultimately, the coating thickness is down to the user.

How you decide if the conformal coating thickness is good enough is up to you. Too thin and you will not protect the circuit as effectively as you may need. Too thick and you could have reliability issues in the future. So, monitor your conformal coating thickness with care.
How you decide if the conformal coating thickness is good enough is up to you. Too thin and you will not protect the circuit as effectively as you may need. Too thick and you could have reliability issues in the future. So, monitor your conformal coating thickness with care.

So what do the IPC Standards recommend when considering conformal coating thickness?

The IPC A 610 standard defines ideal liquid conformal coating thickness values as:

  • Acrylic: 30-130μm
  • Polyurethane: 30-130μm
  • Silicone: 50-210μm

However, this is not the end of the story.

Using the target coating thicknesses as an absolute value can be problematic.

The reality is that the conformal coating thickness will vary massively across the circuit board due to many factors including the surface tension of the liquid, the surface energy of the board surface, the design of the board, the material properties and the application method used.

So, there may be areas on the board that could fall outside of the range where the coating thickness will be less or more than the ideal values.

Therefore, it is highly recommended that the range should be considered as an average value across the board for the conformal coating thickness.

In fact, the IPC go further and suggest using flat test coupons coated in the same way as the process you use for the circuit boards. Then, these test coupons are measured against the standards.

In the end how you decide if the coating thickness is good enough is up to you.

Too thin and you will not protect the circuit as effectively as you may need. Too thick and you could have reliability issues in the future.

So, monitor your conformal coating thickness with care.

Using the target coating thicknesses as an absolute value across the circuit board can be problematic. The reality is that the thickness will vary across the circuit board due to many factors including the surface tension of the liquid, the surface energy of the board surface, the design of the board, the material properties and the application method used.
Using the target coating thicknesses as an absolute value across the circuit board can be problematic. The reality is that the thickness will vary across the circuit board due to many factors including the surface tension of the liquid, the surface energy of the board surface, the design of the board, the material properties and the application method used.

Need to know more about measuring conformal coating thickness in your application process?

Contact us now and we can discuss how we can help you.

Give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

Find out how one company saved 60% of their process costs by changing to custom conformal coating masking boots

Blog, masking boots

Diamond MT, a conformal coating and Parylene coating service provider in the USA, found they saved more than 60% of their current masking costs by switching to the SCH range of conformal coating masking boots.

Sean Horn, Diamond MT, explains how they did it.

“We had initially wanted to try SCH’s conformal coating masking boots for price savings. However, once we began to work with Lee on our specific masking application, we realised that we could extend the life of our boots over 200%. We switched immediately!

We then realised the importance of working with someone who understands coatings. We will not being going back to our previous supplier.”

Sean Horn, Director, Diamond MT, Parylene and conformal coating subcontract service provider.

Diamond MT saved more than 60% of their current masking costs by switching to the SCH range of conformal coating masking boots.

Diamond MT saved more than 60% of their current masking costs by switching to the SCH range of conformal coating masking boots.

So why did Diamond MT switch to our range of masking boots?

When the analysis was completed, it was found pricing for our conformal coating masking boots was lower by 30% compared to their current supplier.

This made a significant saving to Diamond MT and immediately a trial production run was started.

What was really interesting was after using them in the first month, Diamond MT found the masking boots lasted twice as long as their original boot from the alternate supplier.

This meant that now Diamond MT has halved the volume of boots they order and this has reduced their costs by 60% for the year.

This meant what started as a simple trial led to a huge saving to Diamond MT as a partner with SCH.

Need to know more about using conformal coating masking boots in your application process?

Contact us now and we can discuss how we can help you.

Give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

 

Is there a free guide on conformal coating defects?

Blog, conformal coating

Nexus, the independent conformal coating information site, provide an information section on conformal coating defects in their free online Ebook.

According to Nexus, problems in conformal coating can be broken down into two areas.

  • Problems relating to conformal coating process
  • Problems relating to product reliability

In their troubleshooting section they focus on troubleshooting the problems associated with conformal coating processing and production.

You can download the PDF guide Solving conformal coating problems in the application process now.

Need to know more about conformal coating defects?

Contact us now and we can discuss how we can help you.

Give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

 

Do you need MiL spec qualification for your conformal coating?

Blog, Uncategorized

march 28 image

 

Normally, customers know if they require MIL-I-46058C qualification for their conformal coating. It normally is required if it is a military product.

However, caution should be shown when examining conformal coating datasheets that state MEET the requirements of MIL-I-46058C since the conformal coating will likely not be on the Qualified Product List (QPL).

What is the Qualified Product List (QPL)?

The Mil Standard for conformal coating has been inactive for new designs since November 1998. However, the standard is still widely used for independent certification of conformal coatings.

All companies tested to the MIL-I-46058C standard are listed on the QPL. It is still possible to register the coating on the list.

Conformal coatings listed on the QPL will have been through rigorous 3rd party testing to confirm they meet the standard. They are not self-certified.

So, if you require a conformal coating material that is Mil-spec approved then it will have to be on the QPL and it will have been independently tested.

Need to know more about Mil Standard conformal coatings?

Contact us now to discuss what we can offer you.

Give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

0
    0
    Your Cart
    Your cart is empty
    Continue Shopping
      Calculate Shipping