PCB Stiffener Be Used in RF/microwave Applications
PCBs are made out of a rigid substrate on which various components are affixed and connected via races to create a finished circuit. With more advanced electronics, however, engineers developed flexible PCBs with traces sunk into thin strips that allow for flexible connectivity. These new boards are very useful, but they also require a specific component to bridge the gap between solid and flexible PCBs: the pcb stiffener.
Stiffeners are used in a variety of ways to improve the performance and durability of flex circuits. They can reduce sagging, stop shorts from occurring between board layers, and provide more support in critical areas of the assembly. They can be attached to a flex circuit with thermally cured acrylic adhesives or pressure-sensitive adhesives. They can also be fabricated with different materials, such as polyimide, stainless steel, or aluminum.
Depending on the type of application, the pcb stiffener material should be resistant to moisture and corrosion. It should also be able to maintain its physical integrity in extreme temperatures and have good electrical conductivity. Finally, it should be affixed to the flex circuit board in a way that will prevent damage or misalignment.
Can a PCB Stiffener Be Used in RF/microwave Applications?
The most common pcb stiffener is FR-4 glass epoxy, which uses the same laminate material as the FPC base layer and provides good mechanical stability. It is also easily obtainable, making it a cost-effective option for most applications. However, it has a disadvantage of retaining moisture and solvents, which can weaken the copper plating.
Other types of pcb stiffener include aluminum or stainless steel, which offer greater strength and rigidity. They can be attached to a pcb with either thermally cured acrylic adhesives or pressure-sensitive ones, which offer different strengths and durability levels. However, they may require special lamination equipment or additional steps to achieve optimal bonding.
A key benefit of pcb stiffeners is their resistance to flexing, which can prevent the circuit board from suffering from damage during the manufacturing process, assembly, or normal operation. Stiffeners can also strengthen connection sites, which can protect them from wear and tear during connections, disconnection, or regular activity. Stiffeners can also help with heat distribution and dissipation, which promotes superior thermal control of the flex circuit board.
In order to prevent stress on the flex circuit board, it is recommended that the stiffener overlap the bared coverlay by at least.030″ to relieve tension. It is also important to ensure that the stiffener is the same thickness as the bared coverlay.
Typically, the pcb stiffener is attached to the flex circuit board through either thermal bonding or pressure-sensitive adhesives. Both methods have their advantages and disadvantages, and it is necessary to choose a method that will work best with the design of the flex circuit board and its environment.
Thermal bonding is more durable and permanent, but it requires specialized equipment to apply the heat required to activate the adhesive. PSA is simpler and less expensive, but it may not be as strong or stable in certain environments. In either case, careful attention to the flex circuit’s configuration, industry standards, and thorough prototyping are essential to avoid any issues or problems during assembly.
