The Lifespan of PCB Flex Circuits
Lifespan of PCB Flex Circuits
PCB flex is designed to handle long duty cycles for a wide range of applications. It can withstand high temperatures and bending. These features make it ideal for use in the aerospace, defense, down hole oil, and medical industries. It can also withstand vibrations due to its low mass and ductility.
The lifespan of a pcb flex depends on its copper weight, the thickness and spacing of the conductors, and how it is made. To increase its longevity, it is advisable to keep the length of the copper traces as short as possible. This will minimize stress on the traces, and therefore, reduce the likelihood of them breaking. In addition, it is also advisable to avoid sharp angles in the traces. Instead, they should be curved to prevent the copper from experiencing any stresses that could cause damage.
A flex circuit board should have enough copper to sustain the dynamic bending required for its use. It is advisable to choose higher-grade rolled annealed copper. This is because it can stretch more before fatigue cracking occurs and is more springy in the z deflection direction, which makes it better for a flex circuit board that will be continuously bending. It is also advisable to choose a copper foil with an FR-4 rating, as it will have greater thermal stability.
The Lifespan of PCB Flex Circuits
In addition, a flex circuit board should have an appropriate layer stack to ensure that it can accommodate the desired number of bends. Ideally, the layer stack should consist of an outer core and inner core that will be bonded together with epoxy. The outer core can be made of fiberglass or metal. The inner core is typically made of a polyimide (PI) film. PI is an excellent choice because it does not soften when it is heated, unlike other thermosetting materials. It is also highly tolerant of solder reflow cycles and expansion and contraction due to temperature changes.
The layers of a flex circuit board can be printed using photochemical etching. After printing the copper layers, holes are drilled to connect the different sections of the circuit. The final step is to plate the copper using either panel plating or pad-only plating. Both options are acceptable, but choosing the right one will help to save time and money.
The PCB flex will need to be coated with various coatings and adhesives to ensure that it can stand up to the conditions in which it will be used. For instance, it will need to be coated with tin finishing for protection against moisture and corrosion. Alternatively, it can be coated with a soft gold covering that will protect the circuit from any scratches and nicks during the assembly process. It is also a good idea to apply an inorganic stiffener material on the flex circuit to prevent it from buckling under pressure.