A decade ago, could you ever imagine using your smartphone in the pouring rain or your fitness tracker in full sweat?  Thanks to waterproof PCB. These specially designed PCBs have waterproof circuit boards that protect your gadgets from water or other liquids. It all happens without impacting the performance.

In a 2024 survey by Allstate, 21% of phone owners damaged their smartphones by accidentally dropping them in water.

In another survey by Statista, 39% of people reported dropping their phones in water.

These statistics highlight the prevalence of water damage in mobile electronics. They also show why PCB waterproof coating is important.

So, in the following article, we will read the basic and advanced concepts of waterproof pcb.

Key Takeaways

1. What is a waterproof PCB?

2. The limitations of waterproof PCBs

3. Which PCB waterproofing method is better?

What is a Waterproof PCB?

A Waterproof PCB has a conformal coating.  This coating offers significant protection against environmental impacts such as water, chemicals, or other liquids.

Key Characteristics of a Waterproof PCB:

● Conformal Coating:

● Water Resistance:

● Material Selection:

● Sealed Connectors:

Waterproof vs. Water-Resistant PCBs

A key distinction exists between these two terms:

● Waterproof PCB: Waterproof PCBs act as submersible devices. Such PCBs secure gadgets from water and other contamination.

● Water-Resistant PCB: Water-resistant PCBs provide short-term protection, such as minor splashes.

Components of a Waterproof PCB:

The Waterproof PCB is made up of many major elements:

Base: Contains the conductive traces and components embedded in or mounted to a substrate material. Materials of Waterproof PCB

High Tg FR-4: Like regular but with higher moisture resistance.

(Not necessarily in price but exactly how it handles elements)PTFE (Teflon): Great for chemical and water resistance, still picey.

Ceramic: Provides high thermal conductivity and good water resistance. But it is brittle and hard to implement.

Conductive Traces - These are the copper pathways on a substrate that the electric signals will navigate through in a circuit.

Parts: components with better humidity resistance Water resistant_components

Protective Coating: Less than 12 Microns Thin conformal coating to prevent any liquid from getting in between the vulnerable layers. Examples include Parylene, Epoxy, Urethane, and Silicon.

Benefits of Waterproofing Electronics

Waterproofing electronics offer the following benefits:

Protect from Corrosion: Water can eat away through electrolytic erosion and destroy the conductive path. The waterproofing also shields the metallic elements of your metal components from water. At the same time, it works to extend the life of those parts.

Minimal Short Circuits: Water will be able to flow over the PCB and obstacles. In this way, it allows contact between two conductive traces on the board. Ultimately, short circuits happen. Waterproofing lessens the odds of this happening, and it enables circuits to perform as they should.

Less Electrostatic Discharge (ESD) Damage: There is usually moisture deposited on the PCB surface. It also decreases the surface resistance. It can result in a substantial surface resistivity movement; however, waterproofing substantially reduces this.

What are the Key Reasons for Waterproofing Electronics Devices?

The properties of the conformal coating materials differ. As a result, coating materials with all these three fundamental features should be selected henceforth. It is good in water resistance, adhesion and dielectric properties.

Choice of Substrate Material: FR-4 and other similar materials can be used to make the board water resistant, Ceramic materials may be used. Finally, substrate materials also decrease the risk of moisture penetration into the board.

Test Protocols: The wettest PCBs must be tested to verify that the results gained match expectations. These might include humidity tests, salt spray or submersion testing. Depending on the application, testing protocols determine how well a coating performs.

Testing: An assessment of the selected waterproofing alternative will be based on test data. It also demonstrates the PCB can bring an excessive amount of pressure.

The Limitations of Waterproof PCBs

Material Selection:

This is where the waterproof coatings and water-resistant substrate materials are probably going to cost more than non-waterproof ones. This will also likely require even more custom sealing for the connectors, which could drive costs up further.

Application Time:

More complex PCBs may just require longer to apply conformal coatings. This can lead to higher production costs and time.

Testing:

Pretesting may also be required to verify the waterproofing materials are working. Humidity, salt spray and submersion tests are a few examples. This leads to longer and more costly trials of development.

Coating Thickness:

Thicker coatings = better waterproofing It also adds weight to PCB.

Heat Dissipation:

Certain types of conformal coatings even play a role in heat dissipation. That means a PCB must be able to resist much heat.

Signal Attenuation:

A problem of crosstalk between traces in high-frequency PCBs may! There are a few conformal coatings that generate minor attenuation, such as which need to be factored in when choosing and validating materials.

Re-coating -- If repairs are made, the conformal coating has to be re-applied. To Make PCB waterproof, costs more money and requires some additional effort. But re-coating is more expensive and complicated to repair.

How to Waterproof a Circuit Board?

In this section, you will read how to convert a standard PCB into a waterproof circuit board.

Conformal coatings are just a thin, protective layer. They are designed to protect electric parts from being exposed to water.

Types of Conformal Coatings

Every coating material has its own advantages and disadvantages Common coatings are as follows;

Parylene C & N:

Parylene C & N Conformal, Pinhole Free CoatingsTechnical Details: It is highly conformal coatings. Parylene C shows outstanding chemical/moisture resistance. It is also a better option for electrical insulation compared to the Parylene C variant;

Pros: Great for complex geometries, the best moisture barrier, and dielectric properties.

Cons: It needs a lot of equipment and is expensive.

Epoxy:

Technical information: Epoxy coatings vary in chemical resistance and flexibility.

Pros: It is affordable

Cons: Slightly decreases heat dissipation and epoxy must be cured properly to perform best.

Urethane:

Pros: Durable, versatile approach to abrasion resistance (using variable layers), Good with moisture.

Cons: Long cure time vs epoxies, poor chemical resistance versus other options.

Silicone:

Tech Specs: silicon has great chemical resistance but is not suitable for devices requiring high voltage.

Pros: High flexibility, good thermal stability, and chemical resistance

Cons: lower dielectric strives is not proper for prime-power gadgets

High-density polymers:

Polymers have very good moisture barrier properties.

Pros: - Efficient moisture control and thermal performance.

Cons: It is expensive.

Choosing the Right Conformal Coating 

Selecting the right conformal coating is a detailed process, which should reflect several conditions such as -

Material compatibility: Must be able to accommodate its components with the coating.

The specifics of the application: Application Requirements Complex geometries will be needed for coating. Is flexibility critical? Based on these requirements, you can make your decision.

Application Methods of Conformal Coating

Spray Coating also known as Spray painting uses compressed air to spray. It is Ideal For More Elaborate Designs Ventilation is necessary, though to not breathe in the coating material.

Dipping: The PCB is submerged in the coating material, with complete coverage of the top & bottom surface. This approach works only for large-scale manufacturing. Nonetheless, you must bring in sophisticated equipment and expertise.

Brushing:- This is a manual process in which coating is applied by brush. It is ideal for brushing small administration applications.

Which PCB Waterproofing Method is better?

You would have to follow the strategy procedure so that you can pick out which way is best for your waterproofing. We will discuss this for once in brief below

Confocal Testing vs. Enclosures

This is done in two ways: Conformal Coatings and Enclosures for Waterproofing PCBs. Here, we will study their pros and files:

Conformal Coating:

Advantages:

· Supplies a thin, lightweight shield that protects the more fragile pieces

· Lower in price overall than enclosures

· Helps the overall surface to keep on showing warmth through covering material.

· More accessible for inspection and maintenance of the PCB than those with an enclosure.

Disadvantages:

· Conformal coating is also available but does not provide full water submersion protection depending on the type of coating used.

· Physical Impact Resistance - Harsher environments amounting to extreme physical impacts will render conformal coating unsuitable.

Enclosures:

Advantages:

· Provides strong physical barriers, which keep moisture from entering the PCB.

· Fully submersible design possible

· Supportive of additional PCB-level infrastructure

Disadvantages:

· May dramatically scale in size and weight for the whole solution.

· Because the material of your enclosures acts as another preparer blocking escape, so enclosure limits airflow and heat dissipation.

· Opening the enclosure to access the PCB for inspection could breach this seal.

· More costly than conformal coating in general.

Single Layer Coating vs. Multi-Layer Coating

Conformal coatings are mainly applied in either single or multilayer depending on the requirements of your application. Let's weigh the options:

Single Layer Coating:

Advantages:

· Less complicated process allows quicker application.

· This strikes a healthy balance between protection and preventing the heat from dissipating.

Disadvantages:

· Not as capable of protection in harsh environmental conditions

· Lower margin of error - since you need to get complete coverage for best performance

Multi-Layer Coating:

Advantages:

· Great protection is included with the product to more effectively block water and other contaminants from touching your vehicle.

· enables composite layering with coating materials tailored to each individual layer

· Some redundancy if coating defects occur in one of the layers.

Disadvantages:

· The thicker coating can significantly influence heat dissipation.

· This makes for a pretty heavy and large board with weight or size being key concerns in many space-constrained applications.

· A more costly barrier; the application process is incredibly complex and long.

PCB Waterproofing Materials 

Which Waterproofing Material To Choose? In the next part, we will discuss how to determine a viable waterproofing material.

Resin-Based Materials

Many conformal coatings are based on resin-based materials. They have excellent adhesion and protection. This is a basic look at some critical choices:

Epoxy:

Excellent Adhesion over a wide range of PCB components

Clear Sealer (Corrosion Resistance) - This provides a protective barrier to your application from environmental hazards.

Thermal Insulation Characteristics: Thermal Conductivity and Material insulating nature.

Urethane:

Introduction Film Adhesion: Exhibits excellent adhesion to many substrates. Those which have more flexibility?? and contains a few comparably versatile formulations, part of this.

Chemical resistance: Improves the material resistance to many chemicals.

Thermally: Thermally performing like an epoxy. High heat-generating PCBs require careful consideration.

Parylene

Paryele is a vapor-deposited material. It boasts of the following features:

Full adhesive: Excellent adhesion to a broad array of substrates

Corrosion-resistant - it can withstand most chemicals and moisture.

Thermal performance - some are more resistant to heat, while others handle cold environments just fine.

Silicone

The advantages that silicone has over other materials in waterproofing PCBs include.

Adhesion: Materials sticking to the surface are termed adhesion. It also handles thermal expansion and contraction.

Resistant to Corrosion: Has good resistance against moisture and several chemicals. However, it is not suitable for erosive environments.

Thermal Performance: Outstanding thermal stability and wide temperature range flexibility.

How to Test a Waterproof PCB? 

The protection of all Waterproof PCB should be checked as well. It covers the different types of tests able to check waterproofing.

Visual Inspection

Visual Inspection: One of the most important parts of waterproofing inspection. Here's what to look for:

Total Coverage: Ensure that the surface is entirely covered by the layer

Continuity: The solid coating should be applied uniformly, and no pockets or open spaces are left in the metallic layer.

Consistency of Color: Look for a color that might have checked unequally the coating as it was applied.

Check components Check applications for any damage recurring out of Fortunate Patcher

Electrical Testing

The coating has not affected the PCB operation: electrical testing is used to confirm this. The following are some standard techniques:

Ionic Conductivity Testing: This is a measure taken to check if the coating can conduct electricity or not. A low conductivity indicates good coating.

In-Circuit Testing: This is critical to test the whole circuit after waterproofing. This makes the device work more efficiently with its duties.

Environmental Testing

Various methodologies that can be used in the field of environmental testing are:

Humidity Testing: This process is mainly done to test the exposure of PCB devices to high humidity levels. Additionally, examine the Water Resistance of this coating.

Thermal Shock: A PCB device is exposed to rapid temperature fluctuation. It serves to monitor the thermal expansions of the coating.

Chemical Exposure Testing - Some applications are designed to work for chemically exposed conditions; those types of applications have been passed through such conditions. It tests the resistance of the coating to a chemical, detergent, or solvent.

Leak Detection Tests

Specific leak detection tests may be carried out for critical applications:

Dye Penetrant Testing: A solution is spread on the layer. The use of leaks will disclose the defective place.

Vacuum Leak Testing: This consists of placing the PCB application within a vacuum chamber. In this case, leaks are detected by specialized equipment.

How to Remove Conformal Coating from a Waterproof PCB? 

Removal of conformal coating is mandatory when it comes to PCB repairs or reworking. Common methods of removal Alter Yourself

Removing the Guard with Solvent Method

This process requires the use of specific solvents that dissolve the conformal coating.

Considerations:

List of solvents to the type of coating material

Because solvents are often Flammable (explosive) PPE is always necessary to protect personal safety.

This process takes time and you have to make sure the solvents are gone or else it will be bad.

Micro-blasting

This method uses an abrasive media for the conformal coating removal.

Scraping and Grinding

These include physical techniques, such as scraping or grinding the coating out of the PCB.

Should be done only if you have no other option since this method can scratch the surface of the PCB.

These methods are only suitable for small areas.

How Do You Make Sure the Waterproof Conformal Coating is on the Surface? 

The next step in the process is to make sure that all points on the circuit board are fully covered by a waterproof conformal coating, which can be done by:

Torsion bar visual inspection with correct lighting

The coating covered on the component is visually inspected to verify coverage to get good lighting. However is difficult to achieve strong diffused light with magnification (like a magnifying lamp). The aim is to inspect the whole surface of PCB.

Angles: View PCB from multiple angles to guarantee you have full coverage for all concealed spots

To ensure you deliver the optimal coverage results possible, it is important to compare your observations against existing reference standards in order to identify where improvement can be made.

Fluorescence Penetrant Inspection (FPI)

This method provides a more in-depth view of the coating failures.

Procedure: A fluorescent dye is applied onto the part and allowed time to seep out of any crack. The remaining fluorescent dye will now light up with the UV light.

Pros: FPI can detect defects in even microscopic sizes of photocopying.

Cons: FPI is resource intensive both in equipment and for trained personnel.

The Electrical Test

That is each potential problem as seen in the electrical continuity test:

Procedure Test points on a PCB to ensure electrical continuity between interconnected traces. Continuity test finds the problems on trace conductivity But that will not tell it the exact positions.

What Effect Does Temperature Change Have on Waterproof PCB?

Temperature fluctuations affect the conformal coating and PCB components.

Impact on Coating Properties:

Low-temperature coatings can become brittle, cracking at low temperatures due to decreased flexibility.

Adhesion: The coating is very much affected by temperature extremes. It may, for instance, result in the detachment.

Affects Component Performance:

For example, the electrical properties of some capacitors may change ever so slightly with age and temperature rise. As a result, the difference in component selection is very important.

Thermal Expansion - the circuit board and its components will expand very slightly as it is heated. Thermal expansion coating helps reduce stress on the components.

Waterproofing Considerations 

Building a waterproof PCB must take into account many aspects of induction. For instance;

1. In this post you will learn about the application environment

To be able to design the perfect PCB, one must first understand what environment it will live in. Some important questions to ask are:

Type of Moisture: Is it going to get an occasional splash, or is it constant immersion? Selection of the waterproofing coating: Determined based on the amount of water contact.

Operating Temperatures: How cold and how hot can it get inside the tent? Choose materials with a low heat resistance.

Chemical Exposure- Will the PCB come in contact with any harsh chemicals? Make sure that the coating resists chemicals properly.

Stress due to vibration (physical): Is the PCB going to be prone to vibrations Look for coatings with high flexibility.

Understanding these reasons that contribute to the type of environment you are installing your waterproof coating. Now let us understand some critical points before knowing when and where waterproofing coatings would be required.

2. Material Compatibility

Longevity depends largely on compatibility. Consider these aspects:

Coating-Substrate Adhesion: The coating has to adhere properly to the substrate.

Coating/Component Compatibility-Avoids Coated material should not give any harmful gas. Which is also true, it does not initiate a chemical reaction.

Solder Joint Compatibility: Coatings can frequently impact the solderability of critical parts.

3. Size and Weight Constraints

Some waterproofing methods can be affected by size and weight restrictions:

Coating thickness: Thicker coatings provide better protection but are heavier. Coat to Application Requirements - have the coating thick enough for what is expected of it.

Size of enclosure (if using one for extra protection or not): Size and weight in mm will have a huge effect on post processing.

4. Cost-Effectiveness

Better still, waterproofing solutions are priced differently. How to identify the most cost-effective way of implementing it:-

Coating Complexity: Single-layer conformal coatings cost less to apply than multi-layer applications.

Enclosure Cost: Enclosures significantly raise the overall price over conformal coatings alone.

Quality Testing: Due to the high specifications, you may have to invest a lot in advanced testing facilities at an added cost.

5. Regulatory Compliance

In 2019, there is no denying the fact that waterproof PCBs can be deemed a necessity for many different applications. The objective to consider is:

UL 94 Flammability Rating: UL is an Underwriters Laboratories standard for materials classification on flammability. Choose a covering substance that fulfils the UL 94 rating for your program.

Aerospace, automotive, and other industries have standards for waterproof PCBs. Thus, make sure your design complies with the rules.

Applications of Waterproof PCBs

Waterproofing of PCB is very important in industries. Waterproof PCBs are used in multiple industries listed below:

Medical Applications

ECRI has no internal experience with Medtronic's devices, nor any reports of these being used as life-support equipment; the likely meaning is an ancillary device containing some kind of circuit tied to either a stent or defibrillator. It is available for continuous operation.

Medical Instruments: Medical instruments including portable ultrasound machines frequently require PCBs to be waterproof. This is designed to prevent the cleaning agents and moisture you will find in an operating environment from causing damage.

Military Applications

Military communication devices and weapon control systems- the PCB needs to be Waterproof. They can withstand heavy weather.

Communication Equipment - Radios All radios employ waterproof PCBs for seamless communication under adverse weather conditions.

Aerospace Applications

Electrical systems - Flight control system printed circuit boards are waterproof.

Waterproof PCB enables the smooth functioning of the Satellites.

Consumer Electronics

Most smartwatches have PCBs that are waterproof. These are waterproof devices that allow this equipment to be used during exercising or swimming as well.

Fish finders on boats need to use PCBs that are waterproof Saltwater is corrosive and if your circuit board gets wet it can easily damage the contacts.

Industrial Applications -

Process Control: For smooth functioning in hard environments, industrial control systems utilize waterproof PCBs.

Robotic automation equipment using waterproof PCBs. To make sure that they do not become impeded by coolant sprays.

Waterproof PCB Substrates 

Need to choose the PCB substrate for water-proofing This section includes support for selecting the optimum substrate material for your application:

Importance of a substrate

The performance of the waterproof is mainly determined by PCB substrate material. Here’s why:

Moisture Absorbability: Some substrate materials are more absorbable than others. This phenomenon is a result of the varied properties different substrate materials possess. Water Resistant - decreased the amount of moisture a printed circuit board absorbs

Dimensional Stability: walk do not expand and shrink when moisture into them if they have well dimensional stability of substrates.

Thermal Performance -- Thermally conductive materials will greatly affect the heat transfer rate. Plenty of heat conductivity can be very beneficial for a good thermal design.

Examples of Waterproof PCB Substrates

FR-4 (Flame Retardant 4): FR is the most commonly used PCB Base Material, it has good cost-effectiveness and is waterproof and suitable.

PTEF (Polytetrafluoroethylene)Turns out, PTEF is just another name for Teflon. Superior liquid resistance and thermal stability.

Ceramic Substrates Ceramic substrates have high thermal conductivity and excellent chemical resistance.

Sealing Connectors 

Connectors on the PCB are the weakest part of a waterproof solution. Below are the reasons sealing them is important as well:

Why Sealing Connectors are important?

Waterproofing: One of the main challenges for an electric vehicle is to have complete waterproof connectors; If these plugs are unsealed then it would compromise the overall waterproof effect. Why It Is Crucial To Seal Them

Unsealed Connectors: Unsealed connectors provide a positive path for water to make its way into the PCB, which results in failures.

Sticking: Sealing connectors need to stick with the waterproof enclosure and ensure a water-tight result.

Connector sealing techniques have been standardized as:

Gaskets and O-Rings: W The gasket seals ensure water tightness around the connector.

Sealing Compounds - You can use specialized potting to create a watertight seal along the connector.

Water-resistant connectors: Increased connector types feature built-in seals for a more dependable solution.

Customizing Waterproof PCBs 

The PCBs that are waterproof come in various personalized custom functionalities based on the capital intensity to address specific environmental problems. A few of the important aspects that can be customized include;

Conformal Coating Type and Thickness: the type and thickness of the conforming coating will affect its water resistance. Thickness increases the level of protection, however it also adds weight.

Component Selection: Using waterproof components whenever possible will make your PCB more robust. It could be picking encapsulated housings for some parts.

Cabinets: Enclosures made of waterproof materials for additional protection. Materials: any. e.g., ABS plastic or aluminum

Testing Parameters: Applications can be tested under certain environmental conditions. That would be dependent on the environmental factors

PCBasic--Industry Leader in Waterproof PCB

PCBasic is a leading waterproof PCB manufacturer in China. From CPB design to fabrication and assembly, you get everything in one place. In addition, you can order a range of printed circuit boards such as flex PCBs, prototype PCB assembly, and multilayer PCB up to 50 layers. You can get a custom waterproof PCB board quote online without any MOQ. Enjoy a rapid turnaround time of 24 hours on small-batch orders.

Conclusion

PCB waterproof coating provides a robust protection to electronics. It helps them to extend gadget life and face harsh environments. In this article, you have explored the various aspects of waterproof PCB, including waterproofing materials and testing methods. Let’s see how you can leverage waterproof PCBs to make innovative electronic devices.

 

FAQs

How can I determine the water resistance rating of a waterproof PCB?

 

There is no standard water resistance rating like the IP of waterproof PCBs. You can do this by asking your PCB manufacturer about technical specifications or testing methods such as humidity testing, salt spray testing, or submersion testing.

 

What level of waterproofing do I need?

The required level of waterproofing depends on three major factors:

● Occasional Splashes: A moisture-resistant coating is enough.

● Constant Moisture Exposure: This is a waterproof coating with good adhesion

● Submersion: It is a thicker layer of a waterproof coating.

 

Do waterproof coatings insulate against electricity?

Yes, waterproof coatings are electrical insulators. These insulators prevent electrical current from flowing across the circuit board surface. 

Can I repair a waterproofed circuit board?

Yes, repairing a waterproof PCB is possible, but you need advanced tools and skills. In repairing, you will go through the following steps:

● Removing Coating:

● Re-coating:

However, it is always recommended to ask for professional help.

 

What is the impact of waterproof PCB on conductivity?

 

The impact of conductivity on waterproof PCB is very limited. Thin conformal coatings have dielectric properties, which have a negative effect on PCB conductivity.