Flex PCBs Handle Vibration and Shock
Flex PCBs are increasingly being used in a variety of applications. They provide excellent resistance to environmental conditions that would cause failure in rigid printed circuit boards, such as heat, chemicals, and shocks and vibrations. However, their flexibility also makes them susceptible to mechanical stress that can lead to failure if not adequately addressed. In this blog post, we explore how flex pcbs handle vibration and shock, and offer some tips for designing a resilient flex circuit board.
One of the most important factors in determining the durability of a flex PCB is its base material. The most common choice for a flex PCB is polyimide film, which provides the flexibility and resilience that give flex circuits their unique ability to bend dynamically. However, not all polyimide films are created equal; variations in thickness, tensile strength, and elongation at break can significantly impact a flex circuit board’s ability to resist vibrational stress.
Another critical factor in a flex circuit’s ability to withstand vibration is the copper foil layer. The conductive copper in a flex circuit is usually bonded to the substrate with an acrylic or epoxy adhesive optimized for flexible PCB construction. This adhesive helps ensure that the copper conductors stay secure during dynamic bending, which can otherwise cause them to crack or deform.
How Do Flex PCBs Handle Vibration and Shock?
The etching process used to create copper on a flex PCB can have a significant effect on its ability to withstand vibration. Using pad-only plating, where copper is only deposited on vias and pads, improves etch yields and reduces the thickness of the copper, thereby increasing the flex circuit’s flexibility. Another option is to stagger traces instead of stacking them one on top of the other, as this reduces the i-beam effect and increases flex circuit strength.
Lastly, proper routing of the conductive traces is essential to ensuring that they don’t break under stress. Ideally, the traces should be routed perpendicular to the bend line and any discontinuities in the traces should be bridged with solder or solder mask to avoid stress points that could potentially break the traces during bending.
Rigid-flex circuits are an alternative to flex circuits for applications that require more rugged construction. Rigid-flex circuits combine rigid sections with flex areas and provide mounts for components like servomotors, robotic arms, and advanced medical devices. While rigid-flex circuits can’t be bent as dynamically as a flex circuit, they offer superior resistance to vibration and shock and a high degree of reliability.
Whether your design calls for a single- or double-layer flex PCB, you can use the Altium 365 platform to easily specify the appropriate materials and layouts to maximize its ability to resist vibration and shock. Integrated finite element analysis and simulation tools help you model your design’s mechanical performance under various conditions, so you can optimize the materials and layout to meet your specifications. To learn more, get started with a free trial of Altium Designer today. It includes a full set of CAD features, automated drawing tools, and the Draftsman package for flexible PCBs.
