PCB Board Stiffeners Reduce the Risk of Solder Fatigue
PCBs are delicate, and they can become damaged in a number of ways. One way to protect them is by adding stiffeners. Stiffeners make the board rigid, which can reduce or cancel out vibrations throughout the entire design. They also help the board stay flat, which helps reduce the risk of solder fatigue that may occur if the board is not held in a stable position. Stiffeners are also useful for preventing warping of the board during assembly.
Basically, a pcb board stiffeners is a piece of material that’s adhered to the top or bottom layer of the flexible circuit board. It doesn’t add any electrical value to the board, but it does rigidize a specific zone. This is usually done for a variety of reasons, ranging from meeting thickness requirements for components like zero insertion force (ZIF) connectors to providing supplemental support in select areas earmarked for connection or breakable elements.
There are several different types of stiffeners, and the best one for a given application will vary. Typically, a stiffener is attached to the board using thermal bonding or pressure sensitive adhesive (PSA). Thermal bonding uses heat and pressure to melt the stiffener in place, ensuring it will be secure when the board is used. This method is more expensive, but it provides a stronger and more permanent connection. PSA is cheaper, but it’s not as strong and may not be suitable for high-stress applications or environments.
Can PCB Board Stiffeners Reduce the Risk of Solder Fatigue?
The most common type of stiffener for a flex PCB is polyimide. This is a woven glass-fiber laminate impregnated with epoxy resin, and it’s often used for its ability to reinforce the flex circuit boards’ elongated edges while preserving their flexibility. This makes it an ideal choice for meeting thickness requirements for ZIF connectors, and it’s also often used when a flex PCB is designed to be inserted into a mechanical standoff interface.
A FR-4 frame is another popular stiffener option. It’s commonly used on the plated through-hole side of the flex PCB to replace SMT carriers. This saves time during the assembly process and gives plated through-hole components direct access to the solder pads. FR-4 frames are usually attached to the PCB using thermal bonding or PSA, but they can also be adhered directly onto the component.
As with any component on a flexible circuit board, the location and positioning of the stiffener will be crucial to its performance. If the stiffener is placed in a highly active area of the board, it can cause a stress concentration that can damage other components. However, if the stiffener is located in a less active area, it can minimize the impact of vibrations and other stresses on the underlying copper layers. This can prevent solder fatigue and increase the lifespan of the board. In addition, the stiffener can also act as a buffer against environmental factors, such as humidity and moisture, which can degrade the surface of the copper. This can reduce the need for costly rework and repairs in the future.