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Autonomous Vehicles – 4 Ways to Empower Reliability

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January 15, 2021

By 2030, some 20.8 million autonomous vehicles (AVs) will be in operation in the U.S. alone. As the transportation industry turns towards automation, every AV component must be reliable as lives hang in the balance. Unfortunately, the automotive service environment is a severe one for connected electronics. Thermal cycling, exposure to corrosives and contaminants, and intense electrical activity present serious reliability challenges.

As product design teams struggle to pack extra functionality and PCBAs inside industry-first AV chassis, traditional protection methods, such as potting, gaskets, and seals, are reaching limitations as they add bulk and weight into a shrinking electronic landscape. Gaskets and seals can also become dislodged under many circumstances, and corrosives can work their way in, becoming trapped, causing components to fail. Potting and dam and fill encapsulations with traditional conformal coatings add significant weight and bulk to the AV.

Next-generation electronic protection methods, such as thin-film solutions (including Parylene) and nanocoatings, are thinner, less bulky, and offer more reliability, modifying substrate surfaces to augment them with beneficial alternative properties. This blog will address four Parylene conformal coating properties and how they can make your autonomous vehicle product design more reliable.

View our webinar on how to improve automotive electronic performance in harsh service environments.

1. Parylene Corrosion Resistance in Automotive Vehicles

Corrosion resistance is perhaps one of the most sought-after and discussed protection capabilities that thin-film solutions and nanocoatings can deliver. Parylene, other thin-film solutions, and nanocoatings are applied directly to the PCBA, forming powerful barrier protection against corrosive environments.</PBut the most crucial corrosion-resistance property for protective thin-film barriers is the Water Vapor Transmission Rate (WVTR). As mentioned, if water cannot reach the surface, corrosion can’t occur. But all polymers breathe, so a very low WVTR is critical. In addition to WVTR, the water absorption rate is a secondary corrosion-resistance property. It plays a role in overall corrosion protection and affects RF and WiFi designs. The lower the water absorption rate, the better.

View a webinar about proven corrosion resistant methods delivered by Dr. Sean Clancy, Director of Coating Technology at HZO & Anti-Corrosion Expert

The charts below illustrate the WVTR and water absorption rate of Parylene, a thin-film solution, as compared to traditional conformal coatings:

Property

Parylene C
Parylene F
Parylene N
Epoxy
Urethane

WVTR (g·mil)/(100in²·day)

0.21
0.32
1.5
6.6
20.2

Property

Parylene
Epoxy
Urethane

Water Absorption

< 0.1%
0.08 – 1.5%
0.02 – 1.50%

Water absorption for Parylene is significantly lower than alternatives, as is the WVTR. This protection is applied at thicknesses as low as two microns, boasting impressive corrosion-protection with minimal added weight and bulk, enhancing reliability for your autonomous vehicle.

2. Chemical-Resistance

Nanocoatings and thin-film solutions can offer exceptional chemical-resistance properties. Parylene, for example, can survive exposure to corrosives mentioned above and much more. There are multiple thin-film solutions, virtually one for every application. Parylene C has exceptional chemical resistance to most reagents and solvents, including acids, bases, and hydrogen peroxide, as well as organic solvents including toluene, acetone, n-octane, and isopropyl alcohol.

The chart below demonstrates the maximum operating temperature, recommended thickness, and chemical resistance of Parylene types, as opposed to automotive-grade silicone.

Properties

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

Parylene C

100°C
12.5-50μm
High

Parylene F (VT4)

250°C
12.5-50μm
High

Automotive-Grade Silicone

250-370°C
50-200μm
Low to Medium

As autonomous vehicle components face constant exposure to chemicals such as oil, antifreeze, cleaning fluids (to name a few) that can damage components, chemical resistance is an important property you will need in a protective solution to increase reliability.

Download our automotive fact sheet

Parylene, other thin-film solutions, and nanocoatings are applied directly to the PCBA, forming powerful barrier protection against corrosive environments.

3. Thermal Management

Thermal management is crucial for electronics as they get smaller and tolerate higher power. Heat must be dissipated to prevent overheating of components. Thin polymers allow better thermal management, a growing concern as vehicles incorporate more PCBAs.

The chart below demonstrates the thermal conductivity and film thickness of Parylene compared to traditional conformal coatings.

Coating

Desired
Parylene
Acrylic
Epoxy
Silicone
Urethane

Thermal Conductivity (W/mK)

High
0.13 – 0.18
0.13-0.25
0.17-0.21
0.15-0.31
0.21

Film Thickness (µm)

Low
1-25
30-130
30-130
50-210
30-130

Parylene is thermally conductive, but its real strength when it comes to heat dissipation is its low film thickness. When you incorporate thin-film solutions into your product design, thermal management doesn’t have to be a significant concern.

4. Dielectric Properties

Dielectric strength is a measure of how good a material is at electrical insulation. This property is critical for electrostatic discharge and high voltage applications. As the chart indicates below, Parylene delivers the same strength as epoxy and urethane at much thinner coating thicknesses. Additionally, the metal oxide films that plasma-polymerized nanocoatings can produce are potentially even stronger at thinner layers.

Parylene also has lower dielectric constants than liquid conformal coatings, demonstrating an enhanced ability to withstand intense electrical activity in autonomous vehicle operation.

Property

Dielectric Strength short time, V/mil (1-mil thick)
Dielectric Constant
60 Hz
1 kHz
1 MHz

Parylene N

7,000
Dielectric Constant
2.65
2.65
2.65

Parylene C

5,600
Dielectric Constant
3.15
3.1
2.95

Coating Materials for Electronic Applications, Licari

By employing the use of thin-film solutions such as Parylene and/or nanocoatings, you can help ensure that the components powering your autonomous vehicles remain reliable in the harshest of conditions. Are you ready to empower reliability? Talk to one of our SMEs about working with HZO today.

By employing the use of thin-film solutions such as Parylene and/or nanocoatings, you can help ensure that the components powering your autonomous vehicles remain reliable in the harshest of conditions.

Ryan MooreRyan 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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