Flex Rigid PCBs Handle Moisture and Humidity
Rigid flex PCBs are used in applications that handle high currents and generate heat, such as industrial equipment or power electronics. They are also used in consumer electronics, like flexible tablets and smartphones. In these applications, the flex circuit connections help to improve the device’s functionality, durability and flexibility. However, these specialized applications are not without their challenges — including the need to carefully control environmental conditions like moisture and humidity.
In general, a flex rigid pcb can be more difficult to manufacture than a pure rigid PCB due to the need for plated through holes (PTHs) and mounting components in flex sections of the board. However, a well-designed flex PCB can take advantage of the rigid parts of the board to eliminate or reduce the need for bulky cable harnesses — which can save space and assembly time. Rigid flex boards can be made with a combination of rigid and flexible materials, and they have a higher current carrying capacity than traditional rigid PCBs.
When comparing the manufacturing costs of a flex PCB with a rigid PCB, it’s important to consider the number of layers in the PCB and its overall thickness. The more layers and thickness of a PCB, the higher the cost. To lower manufacturing costs, a designer can minimize layers and use thinner materials. Additionally, a designer can choose to minimize the width and spacing of traces on the board. This can increase reliability and allow the flex circuit to handle more electrical stress.
How Do Flex Rigid PCBs Handle Moisture and Humidity?
A common issue that can affect flex PCBs is the infiltration of atmospheric moisture into the polymer material that is used to make the flex circuit. This can cause outgassing and reduced insulation resistance. It’s possible to reduce this risk through careful design, the use of protective coatings and thorough mechanical testing.
Rigid-flex PCBs can also be exposed to unique environmental stresses that aren’t found in other types of electronic assemblies, like vibration and shock. A careful mechanical analysis of the flex region can prevent these stresses from creating unique failure modes in the structure. It’s also critical to evaluate the performance of the rigid-flex PCB through thermal cycling, corrosion testing and vibration/shock tests.
Ultimately, it’s important to consider the entire product design and its intended function when choosing a rigid-flex PCB. Early collaboration with fabricators can also help to minimize the impact of these factors and ensure a successful rigid-flex PCB.
A webinar from Epec Engineered Technologies compared the manufacturing processes and materials involved in producing a rigid PCB and a flex PCB. The webinar showed that a flex PCB requires 8 steps to produce, whereas a rigid PCB takes 17 with more materials and processes. These differences in the manufacturing process and materials help to reduce the cost of production for a flex PCB. In addition to reducing costs, this can also improve the overall quality of the resulting product.