Selecting IPC Class for Medical-Grade Flexible Printed Circuit Boards
In the world of electronics, the International Printed Circuits Association (IPC) plays a crucial role in setting standards for printed circuit board (PCB) manufacturing. One area where these standards are particularly important is in the production of flexible PCBs (Flex PCBs), which are commonly used in medical devices.
For designers working on such projects, choosing the right manufacturing class is essential. Flex PCBs intended for medical applications should be manufactured according to IPC Class 3 standards. This is because Class 3 PCBs are designed for high-reliability electronic parts, including medical applications.
One of the key differences between IPC Class 2 and Class 3 standards for Flex PCBs lies in the allowable defect levels and plating thickness requirements, particularly when it comes to copper plating voids and surface finish coating voids.
In Class 2 Flex PCBs, no more than one void in any hole is acceptable, and not more than 5% of the holes can have voids. Any void should not exceed 5% of the hole length. On the other hand, Class 3 Flex PCBs have no allowed voids in the copper plating holes. This stricter control on plating quality ensures higher durability and electrical performance.
Similarly, while specific quantitative values for coating voids are less frequently detailed in the public domain, Class 3 standards demand virtually zero defects, including voids in surface finish coatings, due to their intended use in high-reliability applications such as aerospace, military, and medical. Class 2 standards, on the other hand, allow for minor imperfections such as very small coating voids that do not impact functionality or reliability.
For those looking for guidance on designing Flex PCBs, a Flex PCB Design Guide is available. This comprehensive guide, spanning 10 chapters, 39 pages, and a 45-minute read, covers topics such as calculating the bend radius, annular ring and via specifications, building a flex stack-up, controlled impedance for flex, fab and drawing requirements, and more.
The article "IPC Class 2 VS Class 3: The Different Design Rules" provides a detailed discussion of these differences. It is essential reading for anyone working on Flex PCB projects, especially those involving medical applications where the highest reliability and zero defects are paramount.
Class 2 Flex PCBs are used in various electronic products, including cameras and smartphones, while Class 3 Flex PCBs are reserved for products requiring the highest reliability and zero defects.
The IPC, as a trade association, plays a vital role in establishing quality standards for PCBs, ensuring that products meet the right qualifications and are safe and reliable for their intended use.
[1] IPC Class 2 VS Class 3: The Different Design Rules [3] Flex PCB Design Guide
Science and technology play significant roles in the development and production of Flex PCBs, particularly in the medical field. For instance, Class 3 Flex PCBs, designed for high-reliability applications, are engineered with stringent controls over plating quality through the guidance provided in the IPC Class 3 design rules (1). This ensures higher durability and electrical performance, essential for medical devices. Furthermore, technology is employed in the creation of the Flex PCB Design Guide (3), which offers comprehensive insight into designing Flex PCBs, using topics such as controlled impedance for flex and ensuring zero defects in medical applications.
