Rigid-Flex PCB Design for Avionics Applications

This whitepaper presents a detailed examination of how American Standard Circuits (ASC) redesigned a rigid-flex four-layer printed circuit board (PCB) to address critical reliability issues in avionics applications. The document outlines the challenges faced by customers, including a 70% failure rate due to copper cracking in the flex area, which compromised electrical connections and raised safety concerns. ASC's proposed solution involved a comprehensive redesign of the PCB stack-up, utilizing adhesiveless Kapton material to enhance durability and flexibility. Key improvements included reducing the flex circuit thickness by 32% and integrating stiffeners to provide additional support in bend-prone areas. The results demonstrated significant enhancements in reliability and performance, leading to qualification on a long-term program and effective mitigation of copper cracking. The whitepaper concludes by emphasizing ASC's commitment to innovation and quality in addressing the unique challenges of the aerospace industry.