Conformal coating and hydrophobic coating are two types of protective coating used in electronics manufacturing to enhance the durability and reliability of products.
Conformal coating has been used in the industry for several decades, while hydrophobic coating has gained prominence more recently as the need for water resistance in electronic devices has grown.
But what sets them apart? And when should we call upon each?
What is conformal coating?
Conformal coating is a thin protective layer applied to electronic components and circuit boards. Its purpose is to shield them from environmental threats such as moisture, dust, chemicals, and even temperature variations, in order to fight off corrosion, keep mould at bay and prevent electrical failures.
When applied to a printed circuit board (PCB), it ‘conforms’ to the board and its components, like a snug-fitting shield. This thin layer, typically around 25-250 micrometers thick, covers everything from solder joints to electronic component leads, exposed traces, and other metal areas. In doing so, it creates a protective armour against corrosion, giving the PCB a longer lifespan.
Conformal coating can be applied in various ways, depending on the complexity and size of the electronic assembly. It can be sprayed on, dipped on, brushed on, or selectively applied to specific areas, ensuring every part of the board gets the protection it needs.
Types of conformal coating
Conformal coating can be made from several materials, each with their own beneficial properties for the different environments the electronic assembly will be operating in:
- Acrylic coating - A low cost option that provides good flexibility and environmental protection, and is easy to apply and dries quickly. However, it’s not suitable for harsh environments or high-temperature applications as it has limited abrasion, chemical or solvent resistance. Acrylic coating is commonly used in consumer electronics, automotive electronics, and indoor applications.
- Polyurethane coating - In contrast to acrylics, polyurethane coating offers excellent chemical resistance and superior protection in harsh environments - particularly in low temperatures.
- Silicone coating - Highly flexible and offers great protection in extreme temperature ranges. It has excellent resistance to moisture, chemicals, and UV light, making it well-suited for outdoor environments. It’s often used in automotive electronics, outdoor LED displays and marine electronics.
- Epoxy coating - Known for its excellent adhesion and durability, it provides a tough protective layer resistant to chipping or cracking, providing good protection against abrasion and moisture. But because epoxy-based materials are so durable, it is less flexible, and making any subsequent modifications or repairs to the board can be tricky. It's most often used when the highest level of protection is required, for example in automotive, aerospace, industrial, and military applications.
- Parylene coating - Applied through a specialised vapour deposition process, parylene coatings form a thin and uniform coating that adheres well to the PCB and its components. It has exceptional moisture and chemical barrier properties and is particularly good in high-temperature environments. Parylene coating is typically used in medical devices, military and aerospace electronics, and other high-reliability electronics.
What is hydrophobic coating?
Unlike conformal coating, which provides comprehensive protection, hydrophobic coating focuses primarily on repelling water and preventing water-related damage.
Imagine having a magic shield that repels water like it’s no big deal. That’s where hydrophobic coating comes in. This special type of protective coating creates a barrier against water, making it slide right off the surface instead of sticking around.
Hydrophobic coating keeps electronic devices and components safe from corrosion, short circuits or malfunctions caused by water sneaking in. It’s like having a waterproof cloak to guard electronics from harm.
You can learn more about hydrophobic coating and its unique qualities in this blog post.
Which coating should be used when?
The main difference is that conformal coatings provide extensive protection against general environmental factors, whereas hydrophobic coatings focus on protection against water.
Deciding which coating to use in electronics manufacturing depends on the assembly itself and the level of protection required.
Conformal coating is often the first choice for PCB assembly. It is often used for delicate electronic components like capacitors, resistors, and integrated circuits which can be susceptible to moisture and corrosion. Likewise, solder joints on PCBs are prone to corrosion and conformal coating can provide insulation to protect against it.
Hydrophobic coating, on the other hand, is typically used for electronic devices like smartphones, tablets, and cameras that are prone to damage if exposed to water. The protective layer repels water, stopping it from reaching the sensitive electronic components inside.
A powerful tag team
In some cases, both conformal and hydrophobic coatings may be used in combination to provide enhanced protection against a range of environmental hazards.
Take electronic devices used outside, like communication equipment or monitoring systems. They often face challenges from moisture, dust, chemicals, and water exposure. In this instance, conformal coating takes the stage as the primary defender, creating a protective layer against general environmental factors like moisture and dust. Adding hydrophobic coating on top provides an extra layer of water resistance, making the device more resilient against rain and water splashes.
And what about wearables like fitness trackers and smart watches? They’re no strangers to sweat, rain, and water adventures. In these cases, conformal coating steps in to provide overall protection against moisture and chemicals. And to seal the deal, hydrophobic coating takes the spotlight, ensuring the device remains water-resistant and safeguarded from water damage during active pursuits.
Combining conformal coatings and hydrophobic coatings unleashes a powerful defence against various environmental hazards. But the specific choice and application of coatings will depend on the requirements, level of protection needed, and the expected environmental challenges faced by the electronic devices.
Conclusion
Both conformal coating and hydrophobic coating play crucial roles in electronics manufacturing to enhance durability and reliability of products.
Conformal coating provides a fantastic defence against a wide array of environmental threats, while hydrophobic coating specialises in repelling water and thwarting any water-related damage. Together, they can form a dynamic duo, each with its own unique focus, working together to ensure electronic devices are shielded from both general environmental factors and the perils of water.
