Condensation: The hidden vehicle failure mode
Article By : Jeremy Garbacik, actnano
With vehicles laden as they are with electronics, protecting those systems from environmental conditions, including condensation, is critical.
On-vehicle electronics have increased exponentially over the past 20 years and will continue on this trajectory through L5 autonomy. Autonomous vehicles combine an impressive array of analog and digital circuitry that will inevitably alter the way we commute. Ensuring the safety of drivers, passengers and pedestrians remains the top priority. To achieve safe ADAS (advanced driver assisted systems), we should consider all aspects of the environment including one that is often overlooked: condensation.
Condensation on vehicle electronics is an expanding concern as power density increases, graphics processors grow, and micro-climates collide. Condensation occurs when warm board-level temperatures clash with cool housings and/or liquid cooled systems. Water does not respect keep-out zones, unprotected components, or hardware redundancy. When accumulating on a printed circuit board assembly (PCBA), condensation acts as a catalyst to reduce system performance and leads to short circuit failure modes.
AVs resemble moving servers
As automobiles begin to resemble moving servers without the benefit of controlled environmental conditions, condensation is a severe threat to the long-term reliability of these systems.
Compounding the condensation obstacle is the expected size increase of many components. Engineers designing these intricate systems are continually pushing the boundaries of system integration by combining cameras, long-range and near-field radar, LiDAR, proximity sensors and more. Larger packages can lead to micro-climate areas with increased disparities in temperature, adding condensation to the overall system. It is crucial while focusing efforts on harmoniously combining advanced technologies to also have an eye toward advanced circuit protection strategies and technologies.
When determining a PCBA protection strategy, engineers must consider its impact on sensitive high-speed digital signals, analog signals, and thermal management performance. The added cost and manufacturing complexity versus protection level is an application design risk each company must weigh. Given the targeted safety level of autonomous vehicles, having a well-designed condensation protection strategy is imperative to system performance.
The good news is there have been significant advances in PCBA coatings. The capability now exists for developers to protect connectors and antennas, as well as the underside of large components without negatively impacting thermals, electrical performance, RF performance, or signal integrity. This advancement in hydrophobic coating technology allows for thinner coatings (~25µm) that provide high thermal dissipation along with more efficient manufacturing processes.
Condensation on a PCBA requires 100% 3D protection on all components and connections. Using a viscoelastic coating is critical to ensure the coating is expanding and contracting at the same rate as the substrate. When high viscous materials are used, their thermal expansion properties differ from the PCBA component materials such as ceramic capacitors, resistors, IC plastics, FR4, metal througholes/vias etc…. Over time and temperature cycles, the differences in thermal expansion properties lead to mechanical stresses, which can crack coatings or displace components. Using viscoelastic coatings eliminates mechanical stress concerns and allows designers to protect the PCBA without apprehension of causing more failure modes than they resolve.
We can’t design tomorrow’s vehicles with yesterday’s technology
It is significantly more challenging to design tomorrow’s autonomous vehicles using yesterday’s PCBA protection strategies. As we rapidly approach a future that will include passengers in autonomous vehicles, confidence in the protection of the electronics directly relates to passenger safety which is clearly the #1 requirement. Long-term reliability of these complex autonomous systems is essential for companies to reach a return-on-investment from the billions of dollars spent during development and production. Given the allocated resources, developed standards, and blending of advanced technologies, it is remarkable to consider something as simple as condensation could rapidly instigate system failure. Companies with a condensation plan will have a strategic market advantage in system performance and life.
This article was originally published on EE Times.
Jeremy Garbacik is vice president of actnano Inc. He has extensive background in application design and custom development of next generation nanotechnology and ICs for the automotive and ADAS markets. He began his career as an applications engineer before moving into various roles in field applications. He has worked for companies including Arrow Electronics, Linear Technology & Analog Devices before joining actnano in 2018. Jeremy earned his BSEE from Michigan State University.