How To Waterproof Electronic Circuits? [Step by Step Process]
In our tech-oriented society, everyone is aware that water and electronics are not the best matches for each other. The result of mixing these two components always comes with great inconvenience.
While pure water is a non-conductor, water with dissolved salts, chlorides, and sulfates is actually a good conductor of electricity. The water that is typically present around us is not in its purest form.
When the various components of a circuit are exposed to tap water, it can result in short-circuits or reduce the efficiency of the circuit.
Fortunately, over the years, we have developed many products that can be used to protect electronic circuits not only from water but chemicals, vibrations, heat, and more.
There are two ways to isolate electronic circuits from environmental factors, conformal coating and potting.
This guide focuses on a range of affordable methods that you can use to waterproof electronic circuits at home. But before that let us look into the components used in electronic circuits.
Components in Electronic Circuits
An electrical circuit is an arrangement of several electronic elements in a certain layout. All the electrical components are connected to each other to conduct and control current flow to carry out particular tasks.
A circuit is always a loop that is its starting point, and the ending point is the same to keep the current flowing.
Let’s start with a basic understanding of the components you can come across in different types of circuits:
1. Resistors
A resistor is copper wire enfolded around a non-conducting material. This is probably the most straightforward part of any circuit.
Resistors have only one role in the circuit that is to offer resistance to the flow of current. Without the resistor, the current will flow at higher levels than required. This can cause overheating or damage to some components.
2. Capacitors
Capacitors are used to store energy like batteries. However, capacitors are very different from batteries on many levels. Unlike batteries, capacitors charge and release energy very quickly. For instance, in-camera flashlights.
The flashgun is attached to a capacitor which draws energy from the battery to charge. When the flash is used, the capacitor uses all its charge in split seconds to generate light.
3. Diodes
A diode is an electrical element that enables current to flow only in one direction. It is a two-terminal device made from either a vacuum tube or semiconductors.
Although, in recent times, semiconductor diodes have been preferred more. Its applications include converting AC to DC, voltage spike protection, and more.
4. Transistors
The transistor may be the most vital part of the circuit. It has many wide applications, from hearing aids to audio amplifiers. Transistors are three-terminal devices made from semiconductors that act as switching devices and amplifiers.
5. Inductors
An inductor is a simple two-terminal device that stores energy in a magnetic field. This energy is released to the circuit when needed. They are included in most electronics, from televisions to radios.
6. LEDs
Light-emitting diodes are used to get visual feedback from the circuit. You will find that LEDs are part of the circuits of almost all electronic devices.
7. Transformers
Transforms are used to send electrical energy from one source to the other. They can also “transform” the electrical energy as per needs. For instance, breaking down high voltage to smaller, more manageable levels to prevent overloading in the device.
8. Batteries
Batteries in PCBs are used to supply the required electrical charge in the circuit.
9. Switches
Switches or relays command the flow of electrical charge in the circuit by opening or closing it.
10. Potentiometers
A potentiometer is an element very similar to resistors, except that its resistance can be varied, and it is a three-terminal device.
11. Sensors
Sensors are simple electronic components that give a particular reaction to sensing a physical input or changes in the environment. A sensor can detect heat, moisture, noise, light, and more.
12. Oscillators
Oscillators are programmable times that are used to create electrical signals at precise times.
Integrated circuits
These are basically minimized circuits integrated into the PCBs. Hence, the name integrated circuits.
Types of PCBs circuits are as follows:
- Single-sided PCB circuits: These are the basic PCBs that contain only a few necessary components such as switches, resistors, batteries, capacitors, and LEDs.
- Flexible PCBs: These PCBs are flexible and can bend slightly.
- Rigid PCBs: These PCBs are very sturdy and inflexible.
Most of the electrical components used in a PCB circuit, such as resistors, transformers, transistors, and more, are not waterproof. Some elements may be waterproof, such as diodes.
However, while water cannot cause any physical damage, it can reduce its efficiency or interrupt the electricity flow like water itself is a conductor. Hence, if there is a risk of water exposure, all possible components in the electronic circuits should be made waterproof.
How To Waterproof Electronic Circuits?
There are two methods to insulate electronic circuits, conformal coating and potting. Potting or encapsulation refers to the process of adding a thick coat of resin such as epoxy around the PCBA.
Alternatively, the conformal coating adds a thin, lightweight coat of waterproofing material such as varnish, urethane, and more. Many waterproofing materials are used for conformal coating. However, silicone adhesive and urethane are two of the most popular conformal coatings.
Potting offers more mechanical strength and may also have dielectric properties. On the other hand, conformal coatings are easier to apply and have a negligible dimensional effect on the circuit.
Based on the electrical circuit, you can choose any of the below listed 4 methods.
- Using Nail Varnish
- Using silicone adhesive
- Using Epoxy Potting Compound
- Using Urethane
How To Waterproof Electronic Circuits Using Nail Varnish?
One of the useful properties of nail varnish is its waterproofing ability. It is not a scientifically engineered method but is one DIY method that is recommended for small single-sided PCB circuits because it is easy and economical.
Small circuits where the component you have to protect is the PCB trace or any other component that does not generate heat or is not removable.
A thin coat of nail varnish can protect the electric board without negatively affecting the electrical connections.
This method will save two of the most essential resources that is time and money. If this sounds like something you need, we recommend using nail varnish.
Required Items
- Nail varnish
- The electronic circuit you want to waterproof
- A clean cloth
Step by Step Process
1. Check the circuit board
Nail varnish sets and dries very quickly. Hence, check the circuit before application.
2. Clean the board
You do not want to apply nail varnish over any dirt. Thus, use a clean, dry cloth to wipe the board to ensure that the board is dust-free.
3. Apply nail varnish
Nail varnish usually comes with a brush applicator, and hence, you should face no problem applying it. Dip the brush in varnish and apply a thin coat over the areas you would like to waterproof on your board.
4. Leave to dry
To avoid any scratches in the thin coat of varnish, leave the board for a good ten to twelve minutes to dry. Once the nail varnish is set, then you can work further with the circuit board.
Precautions
- Nail varnish is designed for nails. This explains why it does not work well with high temperatures. Hence, you should avoid applying nail varnish to areas that produce heat. On heating, the varnish will become too soft and can peel off.
- The flexibility of nail varnish can be helpful, but it also makes it more susceptible to scratches. Such scratches can cause water to seep through. Hence, you should only apply it to areas where the water exposure is significantly less.
Cost
Any cheap nail varnish will be suitable for this method. You can easily get nail varnish under 5 USD.
Time
You should be able to apply nail varnish within a couple of minutes. The drying time of nail varnish is ten to twelve minutes, and thus, the total time for this method will be merely fifteen to twenty minutes.
Waterproofing Electronic Circuits Using Silicone Adhesive
The next type of conformal coating you can use is silicon adhesive. Silicone adhesive has properties like resistance to chemicals, including water, flexibility, temperature resistance, etc. Thus, you can count on it for conformal coating on electric circuits.
Additionally, different kinds of silicone adhesives have some unique set of properties such as non-corrosive, high dielectric strength, and more. Hence, you have the freedom to pick the type of silicone adhesive as per your project.
Owing to its wide range of properties, it is suitable for virtually all components of an electronic circuit, such as transformers, rectifiers, sensors, and more. It can be applied on flexible PCB.
If you get a thermal conductive grade silicone, you can apply it to heat-generating components such as LED arrays and microprocessors and connect them to heatsinks, ensuring that heat transfer happens efficiently.
Required Items
- Silicone adhesive
- The electronic circuit you want to waterproof
- Glue gun
- Box cutter
- Rigid foam
- Clean cloth
- Ruler
- Pen
Step by Step Process
1. Create a box using rigid foam
Take a sheet of rigid foam and lay it flat on the table. Use a ruler and pen to create the outlines of pieces of a cuboid. The size of the cuboid should be large enough to accommodate the electronic board you wish to waterproof.
After marking the pieces, use a box cutter to cut them. Assemble the pieces together and use a hot glue gun to hold them in place. Use the glue generously to ensure there is no gap between the joints of the cuboid.
2. Clean the electronic circuit
Grease and dirt will affect how silicone bonds with the surface. Hence, wipe the electronic board with a clean cloth.
3. Fill the foam box with adhesive
Once the glue is dry and cool, fill half or less of the container with the thick black silicone adhesive. You will notice that silicon adhesive is a sticky, thick paste, but it cures to a rubber-like solid when exposed to air.
4. Place the electronic circuit board
Before the silicon dries, put the electronic circuit board on top and press down gently till the board becomes semi-submerged in silicon.
5. Fill the rest of the box with adhesive
Once the circuit board is paced, fill the silicone adhesive over it. Now, the circuit board will be completely surrounded by a flexible, heat, and water-resistant coat of black silicone.
6. Let the adhesive cure
Now you have to wait for the silicone to dry. The one inconvenience is that silicon can take as long as one or two days to set. The surface of the silicone may dry in a few hours, but it will remain liquid on the inside. Hence, you should give plenty of time for it to dry.
7. Dismantle the box
When the silicon is dry, use the box cutter to dismantle the box by separating all the cuboid sides. The silicon would have turned into a rubber seal around the circuit board. The rubber-like structure of the silicone offers flexibility while sealing out all the external environmental factors.
Precautions
- Always read the instructions included with the silicone adhesive, as each type of silicone adhesive has different properties. Some adhesives need to be mixed with other substances before use. Hence, reading the instructions is a must.
- Never try to hasten the drying process of silicone as it can degrade its performance and reliability.
Time
Creating the foam box and filling it in with silicone adhesive will barely take ten minutes. It is the drying process that is painstakingly long. Drying can take up to two days to dry.
Cost
Typically, silicone adhesives cost 9 to 12 USD, and the cost can be more if you need it in a large quantity. A rigid foam sheet can cost 7 to 9 USD depending on the size. You can easily borrow a hot glue gun in a range of 8 to 10 USD. Box cutters can be bought for as low as 3 USD. Thus, the total budget can be between 27 – 31 USD.
How To Waterproof Electronic Circuits Using Epoxy Potting Compound?
Epoxy is a resin-based potting compound that turns into a robust solid on drying. This is a potting compound that is suitable for electronic circuits that require high mechanical strength.
On solidifying, it offers excellent resistance against damage from heat, water, chemicals, and more. Epoxy is available as a clear liquid and also in color.
Epoxy can be used to cover almost every part of the electronic circuit except the components that require free air, such as an air coil or inductor. Hence, as long as you do not have a component that depends on free air, epoxy resin is a good option.
Moreover, it can prevent vibration fatigue in the soldered connections in the rigid PCB circuits. Thus, it is also recommended for electronic circuits that will be exposed to prolonged vibrations.
Required Items
- Epoxy potting compound
- Measuring cups
- Silicon bowl
- Plastic stirrer
- The electronic circuit you want to waterproof
- Protective gloves
- Protective glasses
- Glue gun
- Box cutter
- Rigid foam
- Clean cloth
- Ruler
- Pen
Step by Step Process
1. Create a box using rigid foam
You will need a mold in which you can set the epoxy resin. You can create a custom mold using rigid foam in which the electronic circuit board you want to waterproof can fit.
Start by laying a rigid foam sheet on a flat table. Utilize a pen and ruler to draw the outlines of pieces to create a cuboid-shaped box.
Use a box cutter to cut all the pieces. Put together all the pieces using a hot glue gun. Apply the glue generously to ensure no space is left in the joints of the box. Leave the box to dry.
2. Mix the potting compound
Epoxy is a two-component potting compound that includes resin and epoxy hardeners. While the box is drying, you can mix the two compounds together. Add eight centiliters of component A and four centiliters of compound B in a silicon bowl using a measuring cup.
Stir using a plastic steerer for up to five minutes till both the components are mixed. Then leave the epoxy for two minutes. While handling the epoxy, always wear protective masks and gloves.
3. Place the electronic circuit in the box
Clean the electronic circuit board using a clean cloth. Then place it in the mold or box you created in step 1.
4. Fill the mold with epoxy
Now fill the mold with epoxy. You should ensure that the electronic circuit in the mold is completely covered with resin. Gently tap the box filled with resin on the table to remove air bubbles
5. Let the epoxy dry
Epoxy, like silicon adhesive, will take many hours to dry. Thus, this is the time you need to practice patience. Leave the epoxy to dry for at least a day. After drying, the resin will become hard, and your electronic circuit will be ready to withstand heat, water, vibrations, and more.
Precautions
- Epoxy can have toxic fumes, pungent odor, and other properties that require wearing protective gear while using epoxy.
- Potting components efficiently block unwanted discharge paths present in free air. However, suppose you have a circuit that relies on the impedance of some free air components. In that case, potting compounds can affect the results. Hence, you should be aware of how much the results can deviate due to potting to correct them.
Time
Preparing the epoxy and creating the mold can be done in a few minutes. It is the drying process that makes the entire project time-taking. Including the drying time, this method will take at least a day.
Cost
The starting price of epoxy is 14 USD, and it can be more depending on quality and quantity. A plastic stirrer can cost 7 to 10 USD. Protective gloves are generally very cheap and cost only about 0.09 – 0.1 USD per piece. On the other hand, safety goggles have a price range of 10 – 15 USD. Including the other supportive products such as foam sheets, glue guns, and more, the cost for this project will be 50 – 60 USD.
Waterproof Electronic Circuits Using Urethane
Urethane is a type of conformal coating that combines the benefits of silicone adhesive and epoxy. It has decent mechanical strength with good flexibility.
This is most suited for electronic circuits frequently exposed to chemicals, including water and humidity. However, it lacks heat and vibration resistance. Thus, it is not ideal for components such as solder connections, resistors, etc.
Besides that, it can be applied to microprocessors, inductors, and other non-removable parts of the circuit. Moreover, its drying time is barely a few hours. Thus, if you need a quick formula to make an electronic circuit waterproof, this method might be helpful.
Required Items
- Urethane insulation coating
- The electronic circuit you need to waterproof
- Clean cloth
- Thinner clear and a spray bottle (optional)
Step by Step Process
1. Clean the electronic circuit
Start by cleaning the circuit using a clean cloth. Grease and dirt may affect how urethane bonds with the surface. Hence, this step is necessary.
2. Apply urethane
Urethane is a clear liquid that has a similar consistency as nail varnish. Generally, you will get a brush with urethane for easy application. Dip the brush in urethane and apply a thin film on the electronic circuit you need to waterproof.
To make the application more convenient, you can spray the urethane. However, in that case, you need to dilute it using a thinner cleaner.
Pour a small amount of thinner in the urethane and mix till you get the right consistency. Then fill the thinned urethane in a spraying bottle. Keep the bottle at a distance of 20 cm from the circuit while spraying.
3. Let the urethane dry
After applying a thin coat of urethane on all the critical areas, let it dry for up to two to three hours. Then the clear liquid coat will harden into a solid film that can protect the circuit from chemicals.
Precautions
- Urethane on drying transforms to this rather solid film which would be hard to rework or reform. Hence, only apply urethane when no further work is required on the circuit.
Time
Including the few minutes required to apply the urethane and the drying time, the total time for this method can be three to four hours.
Cost
The price range of urethane insulating coating is 14 – 20 USD. If you are getting the optional thinner cleaner, the cost for this process will increase by 10 – 14 USD.
As the use of electronic circuits increases in various products and primary industries, the need to make them more durable and long-lasting also rises.
Fortunately, saving the electronic circuits from their nemesis, water, is easier than ever. You only have to carefully pick a method that suits your electronic circuits and follow the corresponding steps correctly.
