Role of a Circuit Board Stiffener
A circuit board stiffener is an integral component that helps to protect components on a flexible printed circuit board. Without them, a flexible PCB can be damaged during manufacturing, installation, and regular use. Stiffeners offer a wide range of benefits, including resistance to flexing, protection of connection sites, and improved heat dissipation.
Typically made from metal, plastic, or FR-4 glass-reinforced epoxy laminate material, the thickness of a PCB stiffener is an important factor that can impact cost, rigidity, and temperature resistance. Metals are generally more expensive, but provide superior rigidity and thermal conductivity. Plastics are typically cheaper, but can compromise structural integrity and flexibility. Stiffeners are available in a variety of thicknesses, from 0.020” to 0.059” to accommodate different design requirements.
A circuit board stiffener is a thin, rigid piece of conductive material that is placed on the top or bottom of a flexible circuit board to strengthen it in specific locations and regions. This prevents bending of the flex in components, which could rip away copper from the board or damage solder joints.
The Role of a Circuit Board Stiffener in Protecting Components
In many cases, stiffeners are placed under tall components like connectors that concentrate stresses. They are also frequently used along zones prone to flexing and vibrations. Stiffeners can also be placed at the edges of a flex circuit to help prevent warping during manufacturing, assembly, or use.
Because a flex circuit has a malleable base, there will be areas that require more support than the base can provide. Stiffeners are a common solution to this problem. They can be made of a wide variety of materials, including polyimide and aluminum. Some manufacturers even have the capability to make a stiffener out of stainless steel. The choice of a particular stiffener depends on the needs of the application, and the manufacturer should have the capacity to provide a variety of options for its customers.
Using stiffeners on a flex PCB requires forethought to avoid creating problems during the manufacturing process. In order to add them, they must be bonded to the circuit board using thermal or pressure-sensitive adhesives. This requires extra steps that can increase the overall fabrication time and costs, but it is often worth it considering the reliability enhancements they can offer.
Moreover, the stiffeners should be placed strategically to ensure that they don’t interfere with the plated holes and traces. Ideally, they should span the area that requires reinforcement and allow access to the components. This can be achieved by performing a mechanical analysis of the flex circuit, or by performing an FEA stress simulation to identify weak areas that need additional stiffness. Stiffeners should be added to these areas as early as possible in the design process to avoid delays in production and assembly. This will also ensure that the stiffeners are ready for use once the fab house is finished. This way, they will be ready to handle the increased stress that the flex will undergo during normal use.