Advancements in electronics design and manufacture, as well as the general trend toward optimization on all fronts – size, weight, power, and cost (also known as SWAP-C) have put a lot of pressure on electronics designers in recent years. These include a push for miniaturization and modularity for devices with increased thermal performance and power requirements. Notably, higher frequencies are required for technologies such as radar, electronic warfare, navigation, and communications, to provide bandwidth for complex subsystems.  

In turn, these developments require electronics protection solutions to be compatible with geometrically complex, high-density, miniaturized devices, such as  stacks of chips, chip-on-board, flip-chips, or other high aspect ratio features, while being suitable for high-frequency RF and microwave performance. Additionally, electronics in scope are often used for critical applications, such as Defense and Aerospace, where reliability is of highest importance and devices must survive some of the harshest environments for extended periods of time.  

Historically, hermetic packaging designed and tested per MIL-STD-883 has been the conventional approach to environmental protection of high-frequency devices, as it provides an airtight seal that keeps moisture and other gasses from penetrating the sealed package. Materials used for this solution are typically metals and ceramics, which are not only bulky and heavy, but are usually difficult, time-consuming and expensive to install. 

In recent years, there has been an increased interest in what is referred to as ‘near-hermetic’ approach, as it provides a number of benefits that align with the SWAP-C requirements.Those packaging solutions consist of cavity packaging molded from LCP, PEEK, epoxies, and other polymeric materials; however, they are significantly more permeable than the ceramics and metals utilized in hermetic packaging. While these materials provide limited protection for a number of use-cases, they cannot guarantee reliability under environmental stress entirely on their own, especially for moisture-sensitive components.  

Finally, conformal coatings are another alternative to encapsulation of electronics, which range in thickness and dielectric properties (from thicker silicones and urethanes, to thinner layers of parylene). However, most begin to show significant impact on RF and microwave performance above ~ 6-8 GHz. Additionally, otherwise thin, highly uniform materials such as parylene show limitation at high temperatures, oxidizing at about 100-150 degrees Celsius.  

To address the needs of the industry, GVD has developed Exilis – an ultra-thin, low-k, protective polymer with a high breakdown voltage and thermal stability, that is uniformly deposited on the micron scale. Most importantly, Exilis is highly conformal and capable of uniformly coating complex features (40:1+ aspect ratio). Exilis can supplement polymeric cavity packaging if applied directly over bare die before overmolding with a plastic or an epoxy package. This semi-hermetic concept enables applications for flip-chip, chip-on-board, and other complex designs and features. The coating also protects against dust and contamination during processing & packaging, and provides electrical insulation of bare die devices and wafers. 

The novel CVD process is being specifically developed and scaled to support DARPA’s DAHI & CHIPS heterogeneous semiconductor integration programs, where it enables the integration of die and components created using different technologies, materials and geometries into a single fab flow.