Highly Conformal Environmental Protection of RF Assemblies

Advance microsystems used in critical applications such as radar, sensing, and high-speed communication utilize devices arranged in complex architectures that are difficult to protect with traditional conformal coatings. GVD has demonstrated that our SignalSeal polymer coating system can meet the environmental protection requirements for these structures with minimal impact on RF performance. The goal of these efforts is to evaluate SignalSeal coatings for present commercial offerings. GVD will address the needs of these devices by modifying existing equipment to accommodate larger assemblies and achieve the required throughput for pilot scale manufacturing. GVD will also validate these SignalSeal coatings on DAHI devices comprised of III-V materials. Demonstrations to date on DAHI devices have been restricted due to the costs and complexities. GVD will look to overcome these restrictions by working with subject matter experts and strategic partners to design custom low-cost III-V devices that permit validation testing on high fidelity substrates. Although SignalSeal materials have yielded promising results, the conformality of deposition from the current process limits the applicability of the coating to bare die and surface mounted assemblies. Complex 3-D microstructures and assemblies possess high aspect ratio features that require the use of prohibitively high nominal coating thicknesses to ensure adequate environmental protection within all areas of the assembly. In this program, GVD will address this limitation of the current processing approach by developing a novel chemical vapor deposition process that will significantly improve coating conformality of the SignalSeal material system and further reduce the RF impact of environmental protection when coating complex 3-D microstructures and assemblies. The new proprietary method is centered around using highly stable initiator molecules for the initiated chemical vapor deposition (iCVD) of SignalSeal. Conventional initiators, while highly reactive, have high sticking probabilities, resulting in gas transport issues that lead to significantly reduced coating conformality. The novel process will enable the synthesis of alternative initiators that are much more stable and eliminate the need to transport high energy initiators in the gas phase. This approach will also eliminate the need for filaments or harsh plasma which can generate other uniformity issues. GVD anticipates that this process will increase coating conformality by up to 200%, reducing the RF impact of SignalSeal on surface structures by 50-80%.  The end result will be a uniquely capable coating system that further minimizes RF impact of SignalSeal coatings through thickness reduction and addresses the unmet protection of future microsystems.