Stiffeners Improve Drop Resistance on PCBs
Adding rigidity to the flexible sections of a pcb board improves drop resistance and protects fragile circuit elements during insertion, removal, or normal operation. Stiffeners offer a variety of benefits, including stress relief, weight balance, and enhanced heat distribution, and can be fabricated from a variety of materials including metals and FR4 fiberglass. They are typically attached to the flex circuit with either pressure-sensitive or acrylic thermally cured adhesives.
The best stiffener material for a given flex PCB depends on the type of application and its specific requirements. For example, a flexible circuit that needs to withstand high vibrations and bending may be better served by a thicker stiffener than one for low-stress applications. FEA stress simulation tools can also help identify weak areas that need reinforcement.
A common choice is a FR4 glass epoxy stiffener, as it uses the same laminate base as the FPC and offers good stability and cost efficiency. Another option is a polyimide stiffener, which is made from a high-temperature polymer formed into thin film layers that are stacked together to achieve greater thickness. Classic examples include kapton and polonomide. Stiffeners are also available in aluminum and stainless steel, but these tend to be more expensive.
The main reason to choose a particular stiffener is its ability to resist flexing, which can cause stress that will rip copper from solder pads or other components. Stiffeners act as a countermeasure against this, as they help to prevent copper tearing away from the plated copper on the flex circuit. In addition, they can increase the strength of a flex circuit by reinforcing connections and other breakable points.
How Do Stiffeners Improve Drop Resistance on PCBs?
Stiffeners can also help to reduce sagging, which can occur when a flex PCB is stacked on top of other boards and can result in shorts between traces or other damage. They can also be used to correct a warped PCB by providing additional support where it is needed.
Other benefits of pcb board stiffeners include resistance to flexing, improved temperature dissipation, and the ability to mount auxiliary components. They can also provide a sturdy foundation for soldering, making them a vital component of any flex circuit assembly.
The type and location of stiffeners on a flex circuit is critical, as they can dramatically impact its performance. For example, stiffeners can be placed under tall components that concentrate stresses and along zones prone to bending or vibrations. They can also be positioned over hole locations to shield them from the strain of repeated insertions and removals, limiting damage that might affect the reliability of the connection.
Another important consideration is that stiffeners need to be sized appropriately for the application. They should not be too big or too small, as they could have an effect on how easy it is to insert and remove components. In addition, the thickness of a stiffener will impact its weight, which can also influence the overall balance and flexibility of a flex circuit.