Design Guidelines for Flexible Printed Circuit Boards (Flex PCB) - Phase 1: Pre-Design Considerations
In the ever-evolving world of electronics, flexible printed circuit boards (FPCs) have emerged as a game-changer. These versatile boards are crucial in various static and dynamic applications, from consumer electronics and wearable devices to automotive systems, printers, humanoid robotics, medical electronics, space applications, and more [1].
Consulting with a contract manufacturer is essential when it comes to FPC design, ensuring the best possible outcome for your project [2]. By collaborating with experts, you can optimise the materials used, such as the most common base material, polyimide, known for its excellent heat resistance and mechanical flexibility [3]. Alternatively, polyester, while less expensive, may not be ideal for high-temperature or dynamic bending environments [3].
Protecting the circuitry is essential, and instead of traditional solder masks, coverlays are used, particularly suited for curved areas to prevent cracking [3]. Interlayer bonding and reinforcing panels are handled by acrylic or epoxy adhesives, chosen for their good heat resistance and high flexibility [3].
The conductor layer typically uses rolled annealed copper, which is suitable for bending, making it the optimal choice for flexible PCBs [3]. Additional layers, such as insulating layers made from epoxy or silicone, or extra conductive layers and shielding for more complex applications, can be added as needed [4].
By consolidating multiple boards, wire harnesses, and connector pairs, using flexible printed circuits can result in direct cost savings [5]. Indirect cost savings come from simplified assembly processes, reduced labor costs, assembly time, and lower risks of wiring errors [5].
Traditional connectors, susceptible to mechanical wear and damage, are often a weak point in electronic devices. By eliminating these connectors, flex PCBs reduce the number of potential points of failure, resulting in improved reliability and longevity of the product [6].
When designing FPCs, it's essential to follow the IPC standards, such as IPC-2223, 4203, 4204, 4205, and 6013, for flex and rigid-flex boards [7]. Customising the design to align with specific application needs is also crucial [8].
Vern Solberg, a flex PCB expert, advises determining the type of application before starting the design process [9]. Building a paper doll model before starting the prototyping process can help refine the design and layout, reducing the need for respins in the prototype [10].
In conclusion, flexible printed circuit boards represent a significant leap forward in electronics technology, offering numerous benefits in terms of cost savings, reliability, and versatility. By working closely with contract manufacturers and adhering to industry standards, designers can create innovative, high-quality FPCs that meet the demands of a wide range of applications.
References: [1] Flexible Printed Circuits: Advantages and Applications. (n.d.). Retrieved from https://www.alliedelectronics.com/library/articles/flexible-printed-circuits-advantages-and-applications/ [2] Choosing a Contract Manufacturer for Flex PCB Design. (n.d.). Retrieved from https://www.pcbway.com/library/articles/choosing-a-contract-manufacturer-for-flex-pcb-design/ [3] Materials for Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.alliedelectronics.com/library/articles/materials-for-flexible-printed-circuit-boards/ [4] Designing Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.pcbway.com/library/articles/designing-flexible-printed-circuit-boards/ [5] Cost Savings with Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.pcbway.com/library/articles/cost-savings-with-flexible-printed-circuit-boards/ [6] Reliability of Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.pcbway.com/library/articles/reliability-of-flexible-printed-circuit-boards/ [7] IPC Standards for Flexible and Rigid-Flex Boards. (n.d.). Retrieved from https://www.ipc.org/standards/standards-by-category/flexible-and-rigid-flex-boards/ [8] Customising Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.pcbway.com/library/articles/customising-flexible-printed-circuit-boards/ [9] Vern Solberg on Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.pcbway.com/library/articles/vern-solberg-on-flexible-printed-circuit-boards/ [10] Prototyping Flexible Printed Circuit Boards. (n.d.). Retrieved from https://www.pcbway.com/library/articles/prototyping-flexible-printed-circuit-boards/
When designing FPCs, it's crucial to select materials appropriate for specific applications, such as using rolled annealed copper for the conductor layer due to its bending suitability, or choosing acrylic or epoxy adhesives for interlayer bonding and reinforcing panels due to their good heat resistance and high flexibility. In the process of creating innovative FPCs, experts recommend consulting technology like controlled impedance to manage signal integrity issues for high-speed applications.
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