Rigid Flex PCBs
When designing complex electronic products that require both flexibility and precision, rigid flex circuit boards are often the most effective option. Rigid-flex circuits consist of a rigid printed circuit board with a flexible printed circuit substrate attached, and they are commonly found in devices like laptop computers, smartphones, and wearable electronics. However, even though rigid-flex PCBs offer significant space efficiency and weight reduction benefits compared to traditional rigid PCBs, they do come with their own unique set of challenges. This is particularly true when it comes to thermal management.
Thermal management in rigid flex circuits is a multifaceted process that requires careful consideration during the design stage. Incorporating strategies such as optimizing design layout, utilizing thermal management solutions, and implementing consistent monitoring and maintenance practices can significantly reduce the risk of overheating and thermal stress in rigid-flex circuits.
Despite their smaller size and lighter weight, rigid-flex circuits can still generate substantial amounts of heat, especially during assembly. Without proper thermal management, this excess heat can cause a variety of problems, including the potential for warping, delamination, and even failure of individual components.
How Do You Handle Thermal Management in Rigid Flex PCBs?
In order to minimize the effects of excess heat, it is important to select materials and laminations that have a high thermal conductivity. Achieving this is possible through the use of copper-based laminates, but it’s also essential to consider the thermal properties of the surrounding rigid and flex sections. Different materials have varying thermal expansion coefficients and moisture absorption rates, which can lead to mismatched CTEs between the rigid and flex sections of the circuit.
A common example of this is when rigid-flex circuits are assembled using a CBT patch. During this process, the flex circuits are soldered to their respective rigid components using a low temperature eutectic solder. In the past, this process was problematic because it caused the flex layers to warp and break down. However, this issue was eventually resolved by adjusting the solder reflow temperature and profile to avoid air-pockets that can influence the flow of heat.
Overheating can also occur when the conductive paths on a rigid-flex circuit are not properly shielded. This can lead to excessive currents that can strain the rigid-flex circuit and cause it to malfunction or even fail completely. This is especially true for applications that involve high levels of current and power, such as LED lights or industrial equipment.
Regardless of the type of application, effective thermal management is vital for a rigid-flex circuit’s long-term reliability. By incorporating effective strategies such as optimizing design layout, leveraging thermal management solutions, and implementing consistent monitoring, maintenance, and testing practices, you can ensure that your rigid-flex circuits operate at their optimal level.
If you’re considering using a rigid-flex circuit in your next project, contact us to learn more about how we can help. Our experienced engineers can provide the advice and guidance you need to achieve your desired results, while minimizing risk and ensuring that your product meets all applicable industry standards.