Five important facts about silicone conformal coatings

  1. Silicone (SR) conformal coatings are inorganic materials. They are polymers in which atoms of silicon and oxygen alternate in a chain. They differ to the organic polymers like the acrylics and urethanes.
  2. The silicone coatings normally have a very wide temperature range of operation compared to the other conformal coatings. Typical range can be -55°C to +200°C (-67°F to +392°F). Like the organic coatings (acrylics and urethanes) they have good moisture protection. They also have good chemical resistance to polar solvents.
  3. SR coatings are generally applied at 2-3 times the thickness dry film compared to organic coatings. This is reflected in the IPC standards on the recommended conformal coating thickness. This increase in material use can lead to increased costs but also better water repellency properties.
  4. Curing of silicones occurs through several different mechanisms, depending on the conformal coating, including RTV (Room Temperature Vulcanisation), Heat, UV, Moisture / Condensation and Catalysed Cure.
  5. In production they can be difficult materials to use due to the cure mechanism being difficult to control. Good housekeeping can minimise these effects. SR coatings can also require different coating equipment or options compared to the organic coatings. This should be considered as part of the holistic approach to conformal coating selection.

The different conformal coating material properties

Conformal coatings can be considered in many different ways.

This includes the different families of materials, their individual properties and the chemistries of these coatings.

The different ways we can examine conformal coatings include:

  • Classification
  • Physical Properties
  • Electrical Properties
  • Chemistry

There is a vast range of options and considerations available.

Click conformal coating material properties to gain a deeper knowledge of conformal coatings.


Need to find out more?

Click silicone conformal 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.

Advertisements

Do you need mil spec qualification for your conformal coating?

1

The Mil Standard (MIL-I-46058C) is a US military conformal coating standard.

It has been inactive for new designs since November 1998.

However, the standard is still widely used for independent certification of conformal coatings.

This means that an independent test house will test the conformal coating. It is not self-certified.

All companies tested to the Mil standard are listed on a Qualified Product List (QPL).

Therefore, conformal coatings listed on the QPL will have been through rigorous 3rd party testing.

MIL-I-46058C is a guideline for quality. However, other standards like IPC-CC-830 may be equally relevant.


2

What is the role of a qualification or standard in conformal coating?

The role of a standard and qualifications is to give a guideline for users on the quality of a product.

For conformal coating standards and qualifications there are two areas that they cover.

These are:

  • Material manufacture
  • Production process

The conformal coating material manufacture standards are used for making the conformal coating.

They are only really relevant to suppliers so that they can measure their coating performance against a set of tests.

The conformal coating production standards are used for qualifying a process.

They are used in the production environment.


Need to find out more?

Click conformal coating standards 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.