How do I correctly dip coat my circuit board in conformal coating?

April 21, 2017 Blog, conformal coating

The dip process for conformal coating is a method used to coat printed circuit boards for a very long time. The process in its simplest form is as follows:

The printed circuit board (PCB) is lowered into a tank of coating.
This can be complete submersion or partial dip.
The board can be dipped vertically, horizontally or at another angle.
The board can be dipped manually or automatically.
The board is removed from the coating and the excess coating drains away.

This process is highly effective in applying a conformal coating to a printed circuit board (PCB).
Dip conformal coating process showing a PCB being immersed using dip coating equipment for consistent, high-volume application

A simple approach involves dipping a circuit board by hand into a container of conformal coating, which can deliver acceptable results for low-volume work. However, dedicated dip coating equipment is typically used—particularly for medium- and high-volume production—where consistency, control, and repeatability are critical.

What equipment may you need for dipping circuit boards?

The reason for using dipping machines in conformal coating is because the process has variables that are critical to film integrity and they are controlled by the system. The variables that are critical for film quality and thickness are:

The speed of immersion
Dwell time in the coating
The withdrawal speed of the board

These factors, plus the viscosity of the conformal coating, are important to create a high quality finish and reduce costs.

How cost effective is the dip process for conformal coating?

The conformal coating dip process itself can be extremely low cost. The cost of a dip system can be low compared to many other processes and when balanced against the speed of application.

However, if the circuit board demands a lot of components be masked before processing then the overall coating process can be expensive. Masking for dipping can be very demanding and very difficult to complete successfully.

Find out more about effective masking strategies for dip coating at our Conformal Coating Masking Hub.

Need to know more about using a conformal coating 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

How do I brush coat my conformal coating?

April 18, 2017 Blog

The correct technique for applying conformal coating by brush is to flow the coating on.

The material should not be brushed on like you are decorating with paint. The coating should be loaded on to the brush and flowed onto the printed circuit board.

*The correct technique for applying by brush is to flow the conformal coating on to the circuit board. The material should not be brushed on like you are decorating with paint.*

What conformal coatings can be applied by brush?

All conformal coatings can be applied by brush and most lend themselves well to the technique. The key points to be aware of are the material pot life and the conformal coating viscosity.

Material pot life. The pot life of the material may be finite so the conformal coating could cure during use. This may make the material useless to apply after a certain amount of time.
Conformal coating viscosity. The way the conformal coating flows is critical when applied by brush coating. Therefore, the viscosity of the coating material is highly influential on the flow so control of the viscosity is critical to allow good coverage.

What Factors Control the Quality of Conformal Coating Finish with Brushing?

Although brushing is often considered the simplest conformal coating application method, achieving a consistent, defect-free finish requires careful control of several interacting variables. Unlike automated processes, brushing relies heavily on human input, making process understanding and training especially important.

The key factors that influence coating quality when brushing include:

Operator skill and technique – Brush loading, stroke direction, pressure control, overlap, and rework handling all directly affect film thickness, edge definition, and defect formation. Inconsistent technique is a common cause of bubbles, streaking, and uneven coverage.
Brush quality and selection – Bristle material, stiffness, tip shape, and cleanliness determine how evenly the coating is deposited. Poor-quality or worn brushes can introduce fibres, air entrapment, and surface texture defects.
Viscosity of the conformal coating – Coatings that are too viscous may leave heavy brush marks or uneven films, while overly thinned coatings can lead to runs, pooling, or insufficient coverage. Viscosity must be matched to both the coating chemistry and the brushing technique.
Coating environment – Temperature, humidity, airflow, and cleanliness influence solvent evaporation, levelling, and cure behaviour. Uncontrolled environments can increase the risk of bubbles, contamination, and poor surface finish.
Board size, layout, and complexity – Dense assemblies, fine-pitch components, connectors, and vertical features increase the likelihood of shadowing, wicking, and thickness variation when brushing. Design choices can significantly impact how practical brushing is as an application method.
Conformal coating material type – Acrylics, silicones, polyurethanes, epoxies, and UV-curable coatings all behave differently under manual application. Dry time, reworkability, solvent content, and levelling characteristics must be understood to avoid defects.

The Role of Training in Brushed Conformal Coating

Because brushing is highly operator-dependent, training is one of the most effective ways to improve quality, repeatability, and yield. Structured training helps operators understand not just how to apply a coating, but why defects occur and how to prevent them.

SCH provides conformal coating training covering:

Correct brush selection and handling techniques
Coating preparation, thinning, and viscosity control
Defect recognition (bubbles, streaking, dewetting, pinholes)
Environmental control and best-practice setup
Inspection criteria aligned with IPC standards
Rework and repair considerations for brushed coatings

Training can be delivered as part of a wider process review or focused specifically on manual application methods, helping manufacturers reduce rework, improve consistency, and build operator confidence.

To learn more, explore our conformal coating training programmes or review our wider guidance in the Conformal Coating Processes Hub, which covers brushing, spraying, dipping, selective robotic coating, and Parylene deposition.

Need to know more about using a conformal coating 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

How Do I Measure Conformal Coating Thickness?

April 13, 2017 Blog

Practical ways to check wet and dry film thickness on conformal coated PCBs

← Back to Conformal Coating Processes Hub ← Back to Technical Articles Hub

There are several practical ways to measure conformal coating thickness on a printed circuit board (PCB). Some methods are used on the wet coating before cure, while others are used once the coating has dried or fully cured.

Common options include:

Non-destructive eddy current systems
Micrometer screw gauges
Wet film gauges

This page is a quick practical guide. For a broader engineering review, including wet, dry and optical approaches, see our main article: Conformal Coating Thickness Measurement: Wet, Dry & Optical Methods.

Non-destructive eddy current system

A fast method for measuring coating thickness is an eddy current system. When used correctly, the process can be extremely quick and accurate, with resolution down to approximately ±1 µm depending on the equipment, substrate and test conditions.

Using a gauge and flying probe for measurement is straightforward. The process works by placing the test probe head flat on the surface of the conformal coating. The reading is almost instantaneous and provides a repeatable result for coating thickness measurement.

Using a test probe system like the Positector 6000 can quickly give conformal coating thickness measurements without damaging the circuit board.

Test coupons are often the ideal way to measure coating thickness, whether the coating is sprayed or dipped, and they can also be retained as a physical production record.

Apply the coating to the test coupons at the same time as the circuit board. This provides a permanent reference and a practical guide to the coating thickness being achieved in the process.

There are some limitations with this type of system:

There must be conductive metal directly below the measurement point, otherwise the system cannot work correctly.
There must be a flat area large enough for the test probe. The smallest practical probe is approximately 6 mm in diameter, so very small areas are generally not suitable.
The surface being measured needs to be flat. Curved or uneven surfaces can introduce errors into the reading.

Micrometer screw gauge

A lower-cost method is to use a calibrated micrometer screw gauge capable of measuring down to around ±10 µm. First, measure a point on the board or test coupon. Then apply the coating, allow it to cure, and measure the same point again. The difference gives the coating thickness.

There are a couple of pitfalls to avoid. Make sure the coating is cured hard enough before measuring, because a soft coating may compact and give a false reading. Also, do not rely on a single point. Take an average of at least three or four readings to improve confidence in the result.

Again, test coupons are usually the best choice for this type of measurement, whether the process is spraying or dipping, because they can be measured consistently and retained as part of the quality record.

Wet film gauge

A final method is wet film measurement, which is simple and cost-effective.

This technique uses a comb gauge with different tooth heights that is placed into the wet coating. The imprint left in the material indicates the wet film thickness. If the solids content of the coating is known, the approximate dry film thickness can then be estimated.

A wet film gauge is a low cost method for measuring coating thickness while the conformal coating is wet. Using the solids content in the material and the wet film thickness allows the dry film thickness to be estimated.

Choosing the right method

Eddy current is fast and non-destructive, but only works where the board structure and geometry allow it.
Micrometer measurement is inexpensive and simple, but depends on stable repeatable measurement points and a fully cured coating.
Wet film gauges are useful during application control, but they estimate dry thickness rather than directly measuring the final cured film.

In practice, the best method depends on whether you are trying to control the process in real time, verify final cured thickness, or create a documented quality record using test coupons.

Related technical guidance

Thickness should not be considered in isolation. Surface profile, coverage, edge definition and defects such as orange peel can all affect how a measured thickness should be interpreted.

Why Choose SCH Services?

SCH Services supports manufacturers with practical coating process control, thickness measurement guidance, defect reduction and production support across conformal coating operations.

If you need help selecting a suitable measurement method, setting up test coupons, or improving process consistency, contact us to discuss your application.

Disclaimer: This article is provided as general technical guidance only. Measurement method suitability, accuracy and acceptance criteria should be validated against the coating material, board design, process conditions and any applicable customer, IPC or internal quality requirements.

What are the alternative materials to liquid conformal coatings?

April 11, 2017 alternative, Atomic layer deposition (ALD), Blog, conformal coating, Molecular vapour deposition, Parylene

There are several alternative coatings available to the traditional conformal coating materials.

These alternative coatings include:

Parylene and other Chemical Vapour Deposition (CVD) films
Fluorinated ultra-thin and thin film coatings
Molecular Vapour Deposition (MVD) coatings
Atomic Layer Deposition (ALD) coatings

They can provide extremely high protection to circuit boards if used correctly for the right product.

There are several new and old alternative coatings available to the traditional conformal coating materials. They include Parylene, fluorinated Nano-coatings, Molecular Vapour Deposition (MVD) and Atomic Layer Deposition (ALD) thin films.

Parylene (XY) Coatings

Parylene is the trade name for a variety of chemical vapor deposited poly(p-xylylene) polymers used as moisture and dielectric barriers.

Parylene is a conformal coating that is deposited as a gas in a vacuum chamber. It is a dry process compared to the standard “wet” liquid conformal coatings.

Find out more about our Parylene Coating Solutions or compare Parylene vs liquid conformal coatings in our knowledge hub.

Fluoropolymer (FC) Nano Coatings

Surface Modifiers are ultra thin nano coatings that are applied at less than a few microns in thickness. Liquid conformal coatings are applied in the range of 25-75um so they are considerably thicker in nature.

There are several variations in ultra thin conformal coatings out in the market now but two of the most popular types are liquid materials and partial vacuum deposition.

Read more about our full range of Fluoropolymer Nano Coatings.

Atomic Layer Deposition (ALD)

ALD belongs to the family of chemical vapor deposition methods (CVD).

It is a deposition process at a Nano-scale level within a vacuum chamber.
The deposition process forms ultra-thin films (atomic layers) with extremely reliable film thickness control.
This provides for highly conformal and dense films at extremely thin layers (1-100nm).

Molecular vapour deposition (MVD)

MVD belongs to both the families of chemical vapor deposition (CVD) and atomic layer deposition (ALD) methods.

Unlike traditional CVD and ALD flow systems the MVD reaction takes place in a chamber under static pressure resulting in extremely low chemical use.
The MVD process produces highly conformal thin film coatings, typically less than 100nm in thickness.
The coating provides excellent barrier properties and surface energy control.

Need to know more about alternative materials to the traditional liquid conformal coatings?

Contact us now and we can discuss how we can help you. Or, 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?

April 6, 2017 Blog, conformal coating

SCH services Ltd provide an information section on conformal coating defects in their Defects Knowledge Hub.

This hub explains the most common defects and failure mechanisms, their root causes, and practical actions to prevent or correct them in production.

Conformal coating defects can undermine PCB protection, reduce insulation resistance, and cause costly rework or field failures. This hub explains the most common defects like de-wetting, de-lamination, corrosion and cob-webbing and details their causes and how to prevent them.

All this is linked to detailed technical articles and inspection guidance.

Need to know more about coating defects?

Contact us now and we can discuss how we can help you. Or, give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

Are there design rules for applying conformal coatings?

March 30, 2017 conformal coating

Conformal coating is not simply a consumable material. Unfortunately, for too many designers, conformal coating is simply a part number, to be applied to circuit boards. However, this can be a major problem especially in the conformal coating production stage of the process.

There are guidelines in the IPC standards that may help with Design for Manufacture (DFM) principles. These are worth considering. Unfortunately, there are no official design guidelines that will help directly with the application process and conformal coating.

Conformal coating treated as a part number rather than a design consideration can cause production issues

When conformal coating is treated as a simple part number rather than a design consideration, it can create significant problems during the production stage.

Conformal Coating Design Hub

SCH Services Ltd has developed design rules for conformal coating in their Design Hub to help users get the fundamentals right.

The hub focuses on designing PCBs and assemblies for coating, including keep-out zones, component spacing, creepage and clearance, and applying DfM/DfCC principles before manufacture. The philosophy is that for companies embracing lean philosophies and applying conformal coatings, a failure to appreciate the subtleties of the application process can result in an un-coatable (at least as specified) assembly process.

The problem is if the rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.

For further information visit conformal coating design rules to learn more.

Need Process Support?

Optimising electronics coating methods requires the right combination of materials, equipment, and operator training. Partner with SCH Services for:

Training & Consultancy on coating processes
Support Equipment including inspection booths, thickness measurement systems, and curing solutions
Direct technical support from our global team

Infographic explaining whether MIL-SPEC qualification is required for conformal coating and how legacy MIL-I-46058C references relate to modern standards.

Do you need MiL spec qualification for your conformal coating?

March 29, 2017 conformal coating

A common question from aerospace and defence customers is: “Do we need MIL-SPEC qualification for our conformal coating?”

The short answer is: sometimes — but only when it is contractually required.

Confusion usually arises because legacy military standards are still referenced on drawings, purchase orders, or coating datasheets, even though the underlying standards landscape has changed.

For a full explanation of how military (MIL) requirements relate to modern conformal coating standards, see: MIL-I-46058C (Cancelled) & MIL Standards for Conformal Coating
.

When is MIL-SPEC actually required?

In practice, manufacturers usually know they require MIL-related compliance when:

The product is for a military or defence programme
MIL requirements are explicitly called up on the customer drawing
The purchase order or contract includes MIL flow-down requirements

If none of these are present, “MIL-SPEC” is often being used as shorthand for high reliability rather than a defined manufacturing requirement. This is where misunderstandings commonly occur.

Be cautious with datasheets claiming “meets MIL-I-46058C”

Many conformal coating datasheets state that the material “meets the requirements of MIL-I-46058C”. This wording should be treated with caution.

MIL-I-46058C is a cancelled standard, and simply stating compliance does not mean the coating has been independently approved or qualified. In many cases, the claim refers only to internal or historical test data.

Where defence programmes genuinely require MIL-style material qualification, customers will often expect evidence beyond a datasheet statement.

What is the Qualified Product List (QPL)?

Historically, conformal coatings tested against MIL-I-46058C were listed on the Qualified Product List (QPL).

The MIL-I-46058C Conformal coating standard has been inactive for new designs since the late 1990s, but QPL listings are still referenced in legacy documentation and long-lifecycle programmes.

Coatings appearing on the QPL would have undergone independent third-party testing rather than self-certification. This is an important distinction.

However, the presence (or absence) of a coating on the QPL does not automatically determine its suitability for modern programmes. What matters today is how customer requirements are defined and verified.

What is normally used instead today?

Modern defence and aerospace programmes typically rely on a combination of:

IPC-CC-830 for conformal coating material performance and qualification
IPC-A-610 for workmanship and acceptance criteria
Customer drawings and specifications defining coverage, keep-out zones and inspection evidence

MIL requirements are therefore usually met through industry standards plus contractual flow-downs, rather than through a single active “MIL-SPEC” document.

Need to understand how the standards fit together?

The Conformal Coating Standards Hub brings together SCH’s guidance on IPC-A-610, IPC-CC-830, IEC 60664, UL 746, NASA workmanship standards and how they relate to conformal coating and Parylene.

It is designed to help engineering, quality and procurement teams understand:

What each standard actually covers
How acceptance, material qualification and inspection requirements interact
Where legacy MIL references still appear — and how to interpret them safely

You can also explore related hubs covering Design, Inspection & Quality and Parylene Coating.

If you need help interpreting customer requirements, legacy MIL references, or selecting compliant coating materials and inspection criteria, contact SCH Services.

📞 Call: +44 (0)1226 249019 | ✉ Email: sales@schservices.com

FAQs Atomic Layer Deposition (ALD)

March 16, 2017 Atomic layer deposition (ALD)

Atomic Layer Deposition (ALD) is an advanced thin-film coating technology used where extreme thickness control, conformality, and film integrity are required at the nanometre scale. It is increasingly specified for high-reliability electronics, semiconductor devices, optics, energy systems, and biomedical components where conventional coating methods reach their technical limits.

Unlike liquid-applied coatings or conventional vapour deposition processes, ALD builds coatings one atomic layer at a time through a self-limiting surface reaction. This allows engineers to precisely define film thickness, composition, and uniformity—even on complex 3D structures, high-aspect-ratio features, and densely packed devices.

The Atomic Layer Deposition FAQs below provide a practical overview of:

What ALD is and how it differs from other CVD-based coating processes
The types of materials that can be deposited using ALD
How the ALD process works in practice
Where ALD is typically used across different industries
The key advantages and limitations of ALD compared with alternative coating technologies

This section is intended to give engineers, designers, and procurement teams a clear understanding of when ALD is technically justified and how it fits alongside other advanced coating solutions such as Parylene and liquid conformal coatings.

What is ALD?

Atomic Layer Deposition (ALD) belongs to the family of Chemical Vapour Deposition methods (CVD).

It is a deposition process at a nano-scale level within an enclosed vacuum chamber.
The deposition process forms ultra-thin films (atomic layers) with extremely reliable film thickness control.
This provides for highly conformal and dense films at extremely thin layers (1-100nm).

What coatings are deposited in ALD?

ALD principally deposits metal oxide ceramic films. These films range in composition from the most basic and widely used aluminum oxide (Al2O3) and titanium oxide (TiO2) up to mixed metal oxide multilayered or doped systems.

How does ALD work in practice?

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.
The majority of ALD reactions use two chemicals called precursors.
These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner.
Through the repeated exposure to alternating gases there is a build up of a thin coating film.

Where is ALD used?

ALD is used in many different areas including:

Micro-electronics
Semiconductors
Photovoltaics
Biotechnology
biomedical
LEDs
Optics
Fuel cell systems

What are the Advantages and disadvantages of ALD

Advantages

Self-Limiting. The ALD process limits the film thickness. Many other processes like Parylene are dependent upon amount of dimer and will continue to deposit successive polymer layers until it is completely used up.
Conformal films. ALD film thickness can be uniform from end to end throughout the chamber. Other coatings like Parylene can have a varied coating thickness across the chamber and the devices being coated.
Pinhole free. ALD films can be pinhole-free at a sub-nanometer thickness. Parylene and some other materials are only pinhole-free at micron levels.
ALD allows layers or laminates. Most other films including Parylene are single component layers.

Disadvantages

High purity substrate. This is very important to the quality of the finish similar to many other vapour deposition processes.
ALD Systems can range anywhere from $200,000 to $800,000 based on the quality and efficiency of the instrument. This tends to be 3-4 times the prices of a Parylene system.
Reaction time. Traditionally, the process of ALD is very slow and this is known to be its major limitation.
Masking challenges. The ALD masking process must be perfect. Any pinhole in the masking process will allow deposition beyond the masking barrier.

What are some of the ALD coatings that can be deposited?

A wide variety of chemistries are possible with Atomic Layer Deposition. They include oxides, nitrides, metals, carbides and sulfides.

Want to know more about Atomic Layer Deposition (ALD) coatings?

What are conformal coating masking boots and how can they save you money?

March 10, 2017 Blog, masking boots

The use of masking materials such as tapes, dots and liquid latex can be a highly effective process in protecting components from ingress of conformal coating. However, the masking process can be labour intensive, difficult and time consuming.

Using reusable, custom masking boots offers a labour saving alternative in both the masking and de-masking stages of the coating process. This can save you lots of time and money.

Conformal coating masking boots used on Printed circuit board as an alternative to masking tapes

Three simple reasons why conformal coating masking boots can save you money

Masking time is reduced. Using masking boots as an alternative can be 4-5 times quicker than masking tape.
De-masking time is reduced. Again it is much quicker to remove masking boots than tape
Masking boots don’t leak as easily as tape. So there is less chance of a need to repair or remove leaked coating.

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

How Diamond MT saved nearly 60% of their process time switching to masking boots

Diamond MT, a conformal coating and Parylene coating service provider, found they saved 60% of their current 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 conformal coatings. We will not being going back to our previous supplier.”

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

Request Your Free Masking Sample Pack

You can experience the quality of our masking solutions first-hand by requesting a free sample pack. The pack includes a selection of our masking tapes, dots, boots and pre-cut shapes, allowing you to test their performance directly in your coating process. It’s a quick and risk-free way to see how our materials ensure clean removal, precise coverage, and time-saving application.

Find out how much you can save by switching to custom boots

We are happy to provide a quotation for our masking boots so you can see for yourself how much you can save.

Just provide us with three pieces of information:

Provide a picture of the board you wish to test
Identify the components you need to mask
Provide the component identification codes (manufacture details etc)

Contact us today to request your quotation for conformal coating masking boots. Call us on +44 (0) 1226 249019, email your requirements on sales@schservices.com