Masking boot FAQs

Download the Conformal coating masking boots FAQs


Where are conformal coating masking boots used in the production process?

Custom masking boots provide protection for many different types of components on a circuit board when insulative thin films are applied and temporary masking is required.

They are used in all of the conformal coating application techniques including batch and selective robotic spraying (as an alternative to difficult technical programming), vertical and horizontal dipping and vapour deposition of coatings such as Parylene and atomic layer deposition (ALD).

Where are conformal coating masking boots used in the production process?

Our conformal coating masking boots are used in many different conformal coating processes including liquid conformal coatings, Parylene deposition and specialist processing such as Atomic Layer Deposition (ALD).

They offer a highly flexible and cost effective alternative to masking using tape and dots where the volume is significant enough to invest in the manufacture of the boots.

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How are conformal coating masking boots used?

Using custom conformal coating masking boots in the production line is easy.

The operator selects the right masking boot for the component to be masked and places it over the component to protect it from the conformal coating application. This applies to any type of component whether it is a connector, plug, socket or device that requires protection from the conformal coating being applied.

The design of the masking boot can vary. It can be a simple boot that fits simply over the top of a connector. Or, the boots can be a more sophisticated design that covers several components at once.

Examples of conformal coating masking boots being used on printed circuit boards

Using conformal coating masking boots is simple if the design is correct. Most boots simply fit straight over the component. This means the masking and de-masking time is a few seconds compared to using masking tape that is normally much longer.

We can help in the design stage to give you the most effective format to save you time and money.

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Why use conformal coating masking boots in your production process?

Masking boots can be an integral part of a full masking solution and replace masking tapes and dots in the conformal coating applications for printed circuit boards. This can be for both a liquid conformal coating process and a vapour deposition process such as Parylene.

Many components and printed circuit board locations must remain uncoated during the application of the conformal coating. The purpose of the masking process is to prevent migration of the conformal coatings into components and keep out areas.

Comparing masking tape versus conformal coating masking boots in the masking process

When a circuit board was masked with conformal coating masking boots and then masked in masking tape the difference in timing was extreme. The board took 5x more to mask and 5x more time to de-mask when masking tape was used. This equated to a saving of approx 25 minutes per board in the masking and de-masking process. 

The use of masking tapes, dots and liquid latex is an effective process in protecting components from ingress of conformal coating. However, the application of the masking materials can be labour intensive, especially in higher volume applications.

Therefore, masking boots can offer a labour saving alternative in both the masking and de-masking stages of the coating process.

In the above image the same board was masked with tape and masking boots. The time taken for the tape to be applied was 5x longer than the boots. The same was true when the tape was removed.

This provides a huge opportunity to reduce costs in the masking process.

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How often can you reuse the conformal coating masking boots?

For normal conformal coating processes most boots can be reused greater than 200 times. In fact, we have some boots still in use in our coating service that have never been replaced and that have probably been used over 400-500 times. They last a long time.

However, there are a number of key factors that can affect the boot including:

  • The complexity of the boot design. The more complex the design the more likely the boot will eventually rip or tear.
  • The thickness of the wall of the masking boot. If the boot wall thickness is less than 2mm then that can make the boot more fragile.
  • The way the boot is cleaned when removing the dry coating. Peeling the coating off is the best method. Solvent cleaning can affect the life of the boot.
  • How tight you require the boot to fit on the components. If you require a tightly fitting gasket seal for processes like dipping or parylene coating you may not be able to use the boot more than 1-2 times. This is because the seal has to be perfect.

If in doubt ask us about your design and we can be accurate on the lifetime / number of uses we expect your masking boot to be used.

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What types of masking boots are available?

Thin Film Partner can provide custom boots solutions for a customer depending on their needs.

We provide both non ESD and ESD versions and we can design the boots to fit your requirements.

different conformal coating masking boots used in the masking production process

We can supply all types of designs of masking boots in both ESD and non ESD material.

We can also determine the best Return on Investment (ROI) when using masking boots for the customer for their particular application.

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Are the conformal coating masking boots ESD safe?

ESD safe conformal coating masking boots from Thin Film Partners

We can provide both non ESD and ESD versions of the reusable conformal coating masking boots.

The ESD versions are more expensive due to the cost of the resin. However, you can also use non-ESD masking boots with desk de-ionisers and this will work perfectly well.

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How do I get a quote for custom masking boots? 

There are three requirements for getting accurate quotes for custom masking boots.

These are:

  • Supply a sample of the PCB along with a masking diagram or photos of the PCB along with exact dimensions of the board itself.
  • Component codes for the individual parts to be masked. You can get this from the component supplier.
  • The number of boots to be quoted for? Remember these reusable boots will last >200 times in production if used correctly.

With this information we will then provide a quote for you.

We will make the boots to a very high tolerance and need to get the measurements correct. Please remember we want to get this right so we cannot guess. 

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What is the temperature limit of the masking boots?

The maximum temperature is approximately 200C since they are silicone.

The boots will last higher temperatures for shorter periods of time so discuss your needs with us.

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Why would a conformal coating masking boot leak?

The masking boots are completely leak proof if they are undamaged. The conformal coating cannot go through the silicone wall.

However, the coating can go under the boot and leak in that way through capillary effects. So, care has to be taken with conformal coating leaking under the masking boot.

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How do I clean the conformal coating masking boot?

The masking boots should NOT be cleaned in solvents. The integrity and lifetime of the masking boot will be degraded.

The conformal coating generally does not stick to the masking boot. Also, the masking boot material is a soft silicone so is very flexible.

So, if you flex the boot, the conformal coating will crack and it is generally possible to peel or flake the coating away.

This is the easiest method. 

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What is the typical thickness of the masking boot wall?

Typical thickness is 1-2mm but we can customise to any thickness.

A thicker wall ensures the boot lasts longer but it will cover more of the board and shield the area.

conformal coating masking boot wall thickness

The wall thickness can vary depending on the design of the boot. We do not recommend a wall thickness <1mm if you require the masking boots to be used >200 times in the production process.

We can discuss your design and requirements on a case by case basis.

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Can a custom mark be added to the surface of the masking boot to make identification easier?

conformal coating masking boots with codes imprinted on them

We can add detail markings if this will help.

As long as the marking can fit on the boot, cap or plug then there is no problem. 

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What conformal coatings can be used with the masking boots?

The masking boots are compatible with nearly all conformal coating materials and solvents. This includes all of the Parylene compositions and the liquid conformal coatings like acrylics, polyurethanes, silicones and epoxies.

However, if you unsure let use know what coating you would like to use and we can check for you.

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Ask us how we can help you

Talk to us about your coating requirements now whatever they may be.

We have the knowledge, tools, experience and the complete solutions whatever you need. We are here to help. 

Contact us now.