Superior Automotive Conformal Coatings to Help You Avoid Road Hazards Ahead

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Dominique McCook | April 8, 2021

If you are an automotive product designer or OEM, chances are, electronics have taken “a front seat” in your career. By 2030, electronics will account for 50% of cars’ total cost worldwide.

Automotive Electronics as % of Total Cost Globally 1970-2030

As more components are integrated into vehicles every year, brands and consumers count on them for critical performance capabilities. Sensors for blind-spot detection, cameras for backup and surround view, lane keep, adaptive cruise control, and park assist are now standard features. From convenience to criticality, it’s essential that all of these function consistently.

Safe Driving is a Priority

Global Automotive Electronics Market by Segment – Safety is an increasing priority

Today’s vehicle PCBAs help power “nice to have” modules such as power windows and heated seats, but they also manage more critical components such as the drivetrain. As the chart above indicates, safety systems are more prevalent than ever, relying upon electronics to function. Failure from corrosion or short-circuiting isn’t an option. If a power mirror stops working due to moisture, it’s a headache. If a safety system fails due to corrosion, it’s a tragedy.

Over the years, the automotive industry has developed solutions to protect primitive vehicle electronics, but can they protect tomorrow’s ADAS and critical components?

Technology has Changed, the Operating Environment Hasn’t

As we see vehicles relying more on electronics for basic and advanced functionality, they aren’t spared the harsh environments they’ve always endured.

Exterior hazards such as rain, salt, mud, standing water, humidity, and pollution all wreak havoc on a vehicle’s external components. Meanwhile, internal threats such as gases, oils, corrosives, and more can render a vehicle inoperable in seconds. When an increasing reliance on electronics and vehicles’ corrosive environments combine, it creates significant challenges for design engineers and OEMs.

Vehicles are expected to last for ten or more years, regardless of where they are safely taken. From salty air and heat in Florida to frozen winters in Canada, vehicles need to handle every environment in between. Inside the car, components may be exposed to coffee, sunscreen, bug spray, or hand sanitizer (especially now). Heat and foreign substances rarely mix well when it comes to the interior of a car.

The environment is no less harsh under the hood. The temperature is hotter, and added solvents such as washer fluid or oil cause reactions with components when exposed to heat.


On Engine / Trans
At Engine / Manifold
Under hood / Near Engine
Underhood / Remote Location
Passenger Compartment

Max Operating Temperature

125°C or 105°C
105°C or 85°C

Contaminant Example

Engine Oil
Cleaning Agents
Transmission Fluid
Washer Fluid
Road Salt
Coffee, Lotion

The severe automotive service environment

The Problems With Old Protection

For years, OEMs have been using traditional mechanical seals and bulky conformal coatings to address the protection of onboard sensitive circuitry. While these solutions have worked to a degree, today’s connected vehicles pack more critical components in a complex footprint than ever before. Traditional conformal coatings are meeting roadblocks as protection demands require smaller, thinner, more sustainable solutions.

For example, silicone, a traditional protective coating commonly seen in vehicles that requires outgassing during manufacturing, must be carefully monitored to ensure complete curing. Mechanical stresses are also possible with silicones, especially when enduring hot-cold cycles. This issue means that additional materials such as underfills or adhesive materials may be needed to hold the part in place if the silicone expands to the point of dislocation.

Rethinking Automotive Protection with Parylene

Parylene is a conformal coating option that offers superior protection without the bulk and weight of traditional coatings such as silicones. Compared to silicone, Parylene exhibits stronger dielectric strength, eliminating performance concerns. Dielectric strength refers to how well an electrically insulating material can perform. This number is calculated based on the maximum electric field the material can withstand under ideal conditions before it breakdowns and becomes conductive. For vehicles, an instant of dielectric breakdown could lead to a nonfunctioning component, all the way up to a small explosion if safety measures fail. Having a material that is a strong dielectric is vital in preventing these issues from ever taking place.

Testing done under ideal conditions rarely reflect reality. That’s where the longevity and chemically inert properties of Parylene come in handy. Even in a scenario that the product has been exposed to salt, humidity, gasoline, or other common vehicle hazards, Parylene can still be expected to perform under pressure.


Parylene C
Parylene F (AF-4)
Parylene N

Dielectric Strength

5,600 V/mil
5,400 V/mil
7,000 V/mil

Dielectric Strength

Download the HZO Guardian Series™ Data Sheet


Max Operating Temp °C
Minimum Coating Thickness to Meet IPC Standards
Chemical Resistance

Parylene C


Parylene F (VT4)


Automotive Grade Silicone


Silicone and Parylene Comparison

For vehicles, an instant of dielectric breakdown could lead to a nonfunctioning component. Having a material that is a strong dielectric is vital in preventing these issues from ever taking place.

Use Case – ECUs

Complex PCBAs that have not previously existed on vehicles. Electronic control units (ECU) such as the telematic ECU, Automatic Gearbox ECU, and Park Assist ECU featured on vehicle screens are now standard. The complexity of PCBAs and modules is increasing, and available space is decreasing as more and more components are added to the vehicle. A balance of putting more in a smaller area is a real challenge.

Newer devices such as BGAs help reduce board size but add challenges in board layouts and manufacturing. Depending on the ECU location, sealing and/or conformal coating may be required to protect against liquid hazards. These requisites must be fulfilled at the best cost and lowest weight, as the automotive industry is highly cost-competitive.

Parylene provides the strong barrier protection required for the complex components at minimal thickness, ranging from 12-50 microns, reducing unnecessary bulk and weight.

HZO’s Solution

While Parylene is considered the “gold standard” of conformal coating protection, it can potentially be costly. That’s where HZO comes in, with proprietary automated masking and demasking that can drastically reduce or eliminate labor and high costs.

HZO can reduce the Total Cost of Ownership (TOC), especially when it comes to warranty claims. Since our Parylene coating is long-lasting, it can keep up with the life of the average car, including risks from salt, rain, snow, and more, by keeping any high-risk modules functioning correctly during the car’s lifetime.

HZO has a yield greater than 99% when it comes to manufacturing. The repeatability of the HZO process ensures that parts are done right every time. On top of that, the IQC/OQC procedures ensure that reworking is successfully completed on any parts that do not meet HZO’s quality expectations.

Because our coating chambers are a meter cubed, they can fit significantly more substrates in one run than other Parylene systems. This, in turn, reduces the turnaround time from start to finish as well as reduces cost. Larger coating chambers also mean that much larger parts can be Parylene coated, which may not have been an option before. The quality assurance at HZO guarantees that parts produced will meet our quality standards to ensure functionality and protection.

Of course, we would not expect you to take our word for this, so we encourage you to reach out to our automotive SMEs for a consultation. We are confident that you will be pleased with our engineering team’s technical know-how and dedication to service. Reach out today.

The complexity of PCBAs and modules is increasing, and available space is decreasing as more and more components are added to the vehicle. A balance of putting more in a smaller area is a real challenge.

Dominique McCook

Application Engineer, Automotive

Dominique McCook has worked in the automotive industry for over five years at a Massachusetts-based Tier II supplier working with many Tier I and OEM companies. She has experience as a Quality Engineer and a Sr. Materials Engineer, as well as a few other roles along the way. McCook holds a B.S. in Chemical Engineering from Worcester Polytechnic Institute.

Ryan Moore

Ryan is a 9-year veteran to the world of protecting electronics from harsh environments and a lover of all things technology.

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