Are there Design Rules for conformal coating dipping?

May 23, 2017 Blog, conformal coating

PCB design rules for dip-applied conformal coating, showing component placement and coating flow behaviour

Applying clear design guidelines for dip-applied conformal coating can dramatically simplify the coating process, reduce defects, and prevent costly production delays.

When boards are designed specifically with immersion coating behaviour in mind, manufacturers benefit from more consistent coverage, easier masking, and far fewer downstream issues on the production line.

Key design rules for dip-applied conformal coating

When designing printed circuit boards for dip conformal coating, attention to layout, handling, drainage, and fixture interaction is critical. The following practical guidelines should be considered at both the PCB and tooling design stage:

Group masked components at one end of the PCB. Place connectors and keep-out features so the board can be dipped to a controlled depth without coating sensitive areas.
Define secure handling points. Ensure the PCB can be reliably held or fixtured without contacting coated or functional areas.
Prevent fixture contamination. Fixtures should avoid entering the coating bath and must not accumulate coating over repeated cycles.
Match coating chemistry to the dip process. Confirm viscosity, cure mechanism, and material compatibility are suitable for immersion coating.
Design for controlled drainage. Allow the board to drain toward a defined edge or corner to minimise pooling and excessive thickness build-up.
Avoid components that trap coating. Select components and orientations that allow coating to drain freely during withdrawal.
Choose masking-friendly components. Where masking is required, use connectors and parts that can be easily protected using boots, caps, or standard masking solutions.

For a deeper technical discussion – including designing PCBs and assemblies for coating, including keep-out zones, component spacing, creepage and clearance, and applying DfM/DfCC principles before manufacture go to our conformal coating design hub.

Why use conformal coating design rules?

Well-defined design rules for conformal coating significantly reduce cost, process risk, and production disruption while improving coating quality and long-term reliability.

Although many principles apply across all coating technologies, each application method introduces process-specific design constraints that must be addressed early in the design stage.

General design fundamentals – geometry, drainage paths, handling points, and coating access
Selective robotic coating – valve access, shadowing, programming tolerances, and keep-out definition
Dip coating – orientation, drainage control, fixture interaction, and thickness build-up
Batch spray coating – coverage consistency, overlap zones, and edge definition
Parylene coating – vapour access, clearances, masking strategy, and material compatibility

Many of these rules overlap across processes, while others are highly application-specific. Understanding where design decisions influence coating behaviour helps engineers avoid rework, reduce masking complexity, and ensure the selected coating process is robust, repeatable, and scalable.

Why conformal coating problems often start at the design stage

Most manufacturers have successfully adopted Design for Manufacture (DFM) principles, improving communication between design teams and production to reduce avoidable challenges.

However, conformal coating is frequently treated as a simple material selection rather than a process-dependent manufacturing operation. Too often, coating is reduced to a part number applied late in the design cycle.

For organisations applying lean manufacturing principles, this lack of early consideration can result in assemblies that are difficult—or impossible—to coat as specified, regardless of equipment capability.

Fortunately, conformal coating design rules are straightforward. When applied early, they save both time and money. When ignored, even the most advanced coating systems can struggle to achieve the required finish.

In nearly all cases, these “nightmare” production scenarios could have been avoided during the design review or prototyping stage.

Get expert help selecting the right conformal coating process

If you are evaluating conformal coating methods or experiencing application challenges, SCH can help review your design and recommend the most suitable coating process, equipment, and masking strategy.

What Application Methods Are Used for Conformal Coating?

May 18, 2017 Blog, conformal coating

Conformal coatings can be applied to printed circuit boards (PCB) in the production process environment in many alternative ways. Listed below are the common methods of applying the conformal coating materials:

Brushing
Aerosol spray
Batch spray
Selective spray
Dipping
Vapour deposition

There are many different methods of applying conformal coatings including brushing, aerosol spray, batch spray, selective spray, dipping and vapour deposition (Parylene).

It is possible to split the different application methods and their suitability in many different ways including:

Compatibility with the conformal coating material
Design of the circuit board
Suitability to low, medium and high volume
Manual versus automatic process
Type of method of application
Level of control required

Each of the various methods has different advantages and disadvantages and should be carefully considered.

This thought process relates to the holistic approach to conformal coating processing that states that you should consider the conformal coating material, the application process and the circuit board together and not as three separate entities.

Find out how we can help you with your conformal coating application selection now.

Partnering with SCH Services means more than just outsourcing — you gain a complete, integrated platform for Conformal Coating, Parylene & ProShieldESD Solutions, alongside equipment, materials and training, all backed by decades of hands-on expertise.

25+ Years of Expertise – Specialists in coating technologies trusted worldwide.
End-to-End Support – Coating selection, masking, inspection and process validation.
Scalable Solutions – From prototypes and NPI through to high-volume production.
Global Reach – Responsive support across Europe, North America and Asia.
Proven Reliability – Built on quality, consistency and long-term customer partnerships.

Call: +44 (0)1226 249019
Email: sales@schservices.com
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What is a hydrophobic conformal coating?

May 16, 2017 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).*

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.

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

How Do I Spray My Conformal Coating?

May 11, 2017 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.

find out more about our conformal coating spray booth and how it can help you.

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.

Let us help you with our conformal coating training courses for spraying conformal coating.

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.

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

May 9, 2017 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.

Find out more about our range of fluoropolymer nano coatings here.

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.

How to Remove Parylene From a Printed Circuit Board

May 4, 2017 Blog, Parylene

conformal coating rework collage 640_SCH UK

Removing conformal coatings from a printed circuit board (PCB) is a hard process to do well. Removing Parylene coating is even more difficult.

The problems are many but a key reason is that the Parylene coating itself is chemically inert. It has a very high chemical resistance so the solvents don’t work well. This means any chemical attack tried with solvents or other liquid chemicals on the Parylene is as much likely to damage the circuit board than remove the actual coating.

This leaves the basic option of mechanical abrasion.

Mechanical Abrasion

Mechanical abrasion is a well known method for Parylene Removal. It can be done crudely by scraping off the Parylene with a knife or tool. Or, removal can be done with a media blast system like a Vaniman Problast system that gradually erodes the Parylene coating away.

However, mechanical abrasion is a time consuming process and is highly skilled. Also, it tends to be a localised repair and removal technique.

The concept of completely removing all of the Parylene off a circuit by mechanical abrasion is considered almost impossible unless a ridiculous amount of time and effort is injected into the process.

Find out now how much money you can save by using our Parylene removal service

We are happy to provide a quotation for removing Parylene through our coating services so you can see for yourself how much you can save.

Contact us now to request your quotation for complete removal of Parylene from a circuit board. Or, give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

Improve your conformal coating masking process reliability with custom boots

May 2, 2017 masking boots

How reusable masking boots improve sealing consistency, reduce operator dependency and strengthen masking process control

Masking reliability is one of the most underestimated drivers of conformal coating quality. When masking fails, coating enters connectors, interfaces and keep-out zones, leading to rework, cleaning and potential field reliability risks.

In many cases, the coating material is blamed. In reality, variability introduced during masking is the root cause. Tape-based masking can be effective, but it depends heavily on operator skill, consistency and geometry access.

Reusable custom masking boots remove much of this variability. By introducing a defined, repeatable sealing method, they stabilise the masking stage and improve overall process control across operators, shifts and production batches.

Customer case study showing over 60 percent reduction in conformal coating masking costs after switching to reusable masking boots

Reusable masking boots provide a controlled sealing method that improves consistency while reducing masking time and rework risk in production environments.

Why masking reliability breaks down in real production

Tape masking introduces variability because the seal is created manually each time. Small defects such as edge lift, wrinkles, contamination or slight misalignment can allow coating to enter protected areas. These failures are often only detected after curing or during inspection.

The risk increases with connector density, tight geometries and repeated masking operations. Over time, even experienced operators introduce variation simply due to fatigue, access limitations or time pressure.

This is why masking is a major contributor to defects. Many issues traced back to coating failures are actually masking-driven. See the Conformal Coating Defects Hub for a breakdown of common failure mechanisms.

If you are comparing masking approaches, refer to our guide to conformal coating masking methods and materials.

Reality check: a large proportion of coating defects originate from masking variability, not coating chemistry.

How custom masking boots improve process consistency

Reusable masking boots replace manual sealing with a defined mechanical interface. Once designed for a specific geometry, they deliver the same sealing performance every time they are applied.

This reduces operator dependency and transforms masking into a controlled process step rather than a manual skill. Application becomes faster, inspection becomes simpler and variation between operators is significantly reduced.

Boots are particularly effective for protecting connectors and contact areas. For more detail on why these areas are critical, see protecting connector interfaces during conformal coating.

At a process level, this contributes to improved first-pass yield, reduced cleaning effort and greater production stability. Masking becomes predictable rather than variable.

What improvements you can typically expect

The benefits of masking boots depend on application, but they are typically adopted where manual masking is limiting throughput or creating inconsistency.

Repeatable sealing performance across batches
Reduced reliance on operator technique
Faster masking cycle times
Lower risk of coating ingress into critical areas
Reduced rework, cleaning and inspection effort
Improved production consistency and yield

In many cases, this translates directly into both quality improvement and cost reduction. It is not uncommon to see significant labour savings alongside improved process robustness. For more on the wider process context, see the Conformal Coating Processes Hub.

Are masking boots always the right choice?

No. Traditional masking methods such as tape and dots remain appropriate for low volumes, prototyping and highly irregular geometries where custom tooling may not be justified.

The correct approach depends on geometry, coating process, sealing requirements and production volume. Boots are most effective where repeatability, speed and protection of defined features are critical to production performance.

For a broader view of masking strategy, visit the Conformal Coating Masking Hub.

Related guidance

These resources provide a complete view of masking strategy, defect prevention and process optimisation.

Why Choose SCH Services?

SCH Services provides practical, production-focused support for conformal coating processes, including masking solutions, training and consultancy. Our approach focuses on reducing variability, improving yield and delivering stable, repeatable coating performance.

If you are assessing masking improvements or considering reusable boots, contact SCH Services here.

This article is provided as general technical guidance only. Masking method selection, sealing performance, reuse life and process suitability should always be validated against your specific assembly geometry, coating materials and production conditions.

How thick should I apply my conformal coating?

April 27, 2017 Uncategorized

So, a question I am regularly asked is,“What is a good conformal coating thickness for my printed 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 material 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 a suitable 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.

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

The IPC A 610 standard defines ideal 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 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 with care.

Learn more about the different methods for measuring the thickness of conformal coating here. Find out more about conformal coating thickness targets and how they are defined by chemistry and function through our knowledge hub.

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. Or, 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

April 25, 2017 Masking

A practical case study showing how lower unit cost and longer boot life combined to reduce annual masking spend

Masking cost is often judged only on the price of the individual boot, tape or masking component. In production, that is too narrow. True masking cost is driven by purchase price, life in service, replacement frequency and the effect on process consistency.

This customer case study shows why that distinction matters. A lower purchase price created the initial interest, but the real saving came from improved boot life and reduced ordering volume over time.

For subcontract coating businesses and production environments, this is the difference between buying masking products and improving the economics of the masking process itself.

Customer background

Diamond MT, a conformal coating and Parylene coating service provider in the USA, reviewed its current masking boot supply as part of a cost-reduction exercise. The initial aim was straightforward: find a more competitive option without compromising masking performance.

What followed was more valuable than a simple price comparison. Once the masking application was reviewed properly, the customer identified both an immediate purchase saving and a significant improvement in boot life.

Diamond MT saved more than 60 percent of their masking costs by switching to reusable conformal coating masking boots from SCH Services

Diamond MT reduced masking costs by more than 60% after moving to SCH reusable conformal coating masking boots with improved service life.

Key point: the biggest saving did not come from unit price alone. It came from combining lower purchase cost with longer usable life in production.

What Diamond MT said

Sean Horn of Diamond MT explained that the original interest was based on price. However, after reviewing the application and using the boots in service, the commercial picture changed significantly.

“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 be going back to our previous supplier.”

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

So why did Diamond MT switch?

The first finding was simple: SCH masking boots were priced approximately 30% lower than the customer’s existing supply. That was enough to justify an initial production trial and begin comparing real-world performance.

The more important finding came after the first month of use. Diamond MT found that the boots lasted around twice as long as the previous alternative. This changed the economics of the full process, because the customer no longer needed to replace boots at the same rate.

As a result, annual ordering volume was effectively halved. When lower purchase price and longer service life were combined, the customer’s total masking boot cost fell by more than 60% over the year.

What this case study really shows

This is not just a price story. It is a process-cost story. In masking applications, the cheapest-looking option is not always the lowest-cost option once replacement frequency, handling life and repeat usage are included.

For many users, especially in repetitive production or subcontract coating environments, the more important question is how long the masking product survives in real service and how consistently it performs over time.

That is why custom reusable boots can create a stronger commercial result than basic unit-price comparison suggests. If you want to explore the broader process-control argument, see our article on improving conformal coating masking process reliability with custom boots.

Where reusable masking boots add most value

Reusable masking boots are most valuable where a masking feature is repeated often enough for speed, seal repeatability and service life to matter commercially. This is particularly relevant in production runs involving connectors, interfaces and defined keep-out areas.

High-repeat masking applications
Subcontract coating and service environments
Connector and keep-out protection
Processes where masking labour is significant
Applications where consistent fit and reuse life affect cost

If you are comparing different masking options, our reusable masking boots guide explains how these products are used to create fast, repeatable seals around connectors and protected features.

Related guidance

These pages explain where reusable boots fit commercially and technically within the wider masking process.

Why Choose SCH Services?

SCH Services supports manufacturers and coating service providers with practical masking solutions, production-focused advice and reusable products designed for real conformal coating and Parylene applications. We help customers look beyond simple purchase price and focus on total masking cost, repeatability and process performance.

If you want to review whether reusable masking boots are likely to reduce masking cost in your own process, get in touch and we can discuss the application with you.

This article is provided as general guidance and customer example content only. Cost savings, service life and suitability will vary depending on masking geometry, coating type, handling practice, reuse conditions and production environment. All applications should be assessed against actual process conditions.

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