Do you need UL qualification for your conformal coating?

June 1, 2017 Blog, conformal coating

UL are the Underwriters Laboratories and are a global safety certification body for consumer electronics. They are a 3rd Party test service. There is no self-certification available. A qualification to UL can be used as a sign of quality control and testing independently of the coatings protective ability.

When do you need UL?

Sometimes it may be required that the conformal coating needs UL approval to be applied to a circuit board. It will depend on the market the electronics goes into. UL approved coatings can be used on electronics in many diverse sectors such as the domestic home, industrial controls, telecommunications and aerospace.

In fact, in nearly all areas conformal coatings tend to be used for protection.

SCH Services UK conformal coating facility and production environment

UL approved coatings can be requested in nearly all areas conformal coatings tend to be used for protection for electronics including domestic home, industrial controls, telecommunications and aerospace.

What standards are used from UL for conformal coatings?

For conformal coating, two parts of the UL standards are important. These are:

UL 94: Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing.
UL 746E: Standard Polymeric Materials: Industrial Laminates, Filament Wound Tubing, Vulcanized Fiber and Materials Used in Printed-Wiring Boards

The two standards together control the quality of the conformal coating.

UL 94

It is a plastic material flammability standard.
The standard classifies plastics according to how they burn in various orientations and thicknesses.
UL 94 measures conformal coating material’s tendency either to extinguish or to spread the flame once the test specimen has been ignited.

For conformal coatings the test coupons are normally tested horizontally. Tests are normally conducted on coupons of the minimum approved thickness with different types of laminate. The conformal coating thickness range also is normally specified.

The ratings are as follows:

V-2 burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.
V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

Most conformal coatings aim to achieve V-0 status (top result).

UL 746E

UL 746E is the Standard Polymeric Materials: Industrial Laminates, Filament Wound Tubing, Vulcanized Fiber and Materials Used in Printed-Wiring Boards

UL 746E measures the ignition resistance of the conformal coating to electrical ignition sources. The conformal coating material’s resistance to ignition and surface tracking characteristics is described in UL 746E.

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

How do I selectively apply my conformal coating?

May 30, 2017 Blog, conformal coating

Selective application of conformal coating in this case is applying the conformal coating without using masking to shield components from ingress.

Technically, using masking tapes, latex and boots is a selective process. But, we are looking at coating applications without masking. This leaves a couple of different options.

The first is brushing. This is a simple selective process that can be highly effective.

The second, and the more obvious option, is selective robot. This process uses a small spray valve (there are many conformal coating spray valve types) that is attached to a robot that follows a set pattern applying the conformal coating selectively to the circuit board.

Advantages and disadvantages of selective conformal coating robots

The five advantages and disadvantages of selective application of conformal coating are:

Advantages

Masking can be eliminated or minimised
High speed coating process
High volume process
High quality finish when under control
Simple process to operate when set up

Disadvantages

High engineering skill required for set up and programming
High engineering skill required for troubleshooting and supervision
High capital cost initially
Process controls need to be enforced for good quality production
Environment can influence the process controls

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

SCH supports OEMs and EMS providers with a fully integrated total-solutions approach to conformal coating and Parylene—spanning in-house process development through to fully outsourced production. Our focus is on delivering coating strategies that are technically robust, commercially viable and scalable, from early prototype through to full-rate manufacture.

For manufacturers operating their own coating lines, we provide comprehensive engineering support including PCB design reviews, conformal coating line set-up, Parylene deposition equipment, masking optimisation, SPC and control planning, and operator training. We also support NPI programmes, helping teams validate chemistries, define robust masking strategies, optimise equipment parameters and benchmark new materials or processes prior to volume release.

For organisations outsourcing coating, SCH delivers fully managed coating services covering both liquid conformal coatings and Parylene. These services are underpinned by structured technical consultancy, specification development and detailed troubleshooting and failure analysis. Whether addressing a short-term process issue or establishing a long-term coating partnership, we ensure assemblies meet demanding environmental and reliability requirements.

At every level of engagement, SCH provides tailored training and technical consultancy, including process benchmarking, defect prevention, troubleshooting, design-for-coating guidance, and on-site or remote support for engineering and quality teams.

Whether your requirement is technical guidance, equipment supply, production capacity, NPI validation or continuous process improvement, SCH delivers end-to-end support across the complete coating lifecycle.

Find out more about our:

👉 C onformal Coating Solutions
👉 Pa rylene Solutions

Call: +44 (0)1226 249019
Email: sales@schservices.com
Contact Us ›

How do conformal coating masking boots save money in your production process?

May 25, 2017 Blog, conformal coating

Three ways reusable PCB masking solutions reduce coating costs

Reusable masking solutions protecting PCB components during conformal coating at SCH Services

Switching from disposable tapes to reusable masking solutions can cut conformal coating costs by up to 80%, particularly in medium- to high-volume production.

1. Faster application. Pre-formed boots are typically 4–5× quicker to apply than manual tape masking,
  reducing operator time per board.
2. Rapid removal after coating. One-piece removal eliminates the slow peeling, residue cleanup, and inspection
  associated with traditional masking materials.
3. Lower rework risk. Unlike tape, moulded boots provide consistent sealing around connectors and interfaces,
  reducing coating ingress and costly touch-up or strip-and-recoat cycles.

The result is a more predictable masking process, improved yield, and faster throughput—especially where repeatability matters.

Get expert advice on reusable masking for conformal coating

SCH helps manufacturers select and implement reusable masking boots and component protection solutions that reduce labour, improve consistency, and support scalable production.

You can explore our range of reusable PCB masking boots, or review our technical guidance on conformal coating masking strategies, which explains when to use boots, tapes, dots, liquid mask, or custom plugs—along with best practice,
standards considerations, and common failure modes.

This approach helps ensure your coating operation remains efficient, repeatable, and rework-friendly as volumes increase.
Contact us to discuss your application →

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.

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

How thick should I apply my conformal coating?

April 27, 2017 Blog, conformal coating

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 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 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.

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.

What started as a simple trial led to a huge saving to Diamond MT as a partner with SCH.

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

Diamond MT reduced their masking costs by more than 60% after switching to SCH’s reusable conformal coating masking boots.

Read our article in the Conformal Coating Masking Knowledge Hub on Reusable masking boots and find out how they give fast, repeatable seals around connectors and keep-outs, so you can lift first-pass yield and cut masking labour.

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

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