By Flex PCBs Be Used in RF/Microwave Applications
Flex PCBs have a great deal of versatility that makes them suitable for a wide variety of applications. This includes the ability to be bended and used in tight spaces, as well as the fact that they can be easily modified and repaired when damaged or worn. In addition, a number of design considerations have been made to improve the durability and performance of these circuit boards. This includes the use of polyimide material, which helps to reduce thermal shock, as well as the elimination of interconnection failures, which is one of the main causes of PCB failure.
Flex circuits can be used in a variety of RF and microwave applications, but the selection of materials should be based on the specific requirements of the application. Various materials are available for flex circuits, and each should be selected based on the shielding performance needed, influence on mechanical bend capabilities, and suitability for controlled impedance signal requirements.
For example, copper is a common choice for flex pcbs because of its excellent conductivity and low cost, but it is prone to fatigue and work hardening when subjected to repeated bending. A better alternative is a conductive polymer such as Teflon (PTFE), which is much less susceptible to fatigue and works well with flex circuits.
Can Flex PCBs Be Used in RF/Microwave Applications?
The thickness of the flex circuit board can also impact its performance. Thicker traces have a greater resistance to bending, while thinner ones are more flexible. A good design practice is to use a gradient change in width between the thick and thin traces, as this will increase their flexibility and strength. Additionally, rounded edges on a flex circuit will help to reduce the strain and tear resistance.
A flex circuit can be designed for a variety of connections, including through-holes and solder balls. The placement of these connections can also affect the bending capability and stiffness of the circuit. Using a wider solder ball, for example, can help to improve the bending capability of the circuit. For higher voltages, a blind and buried via is recommended to prevent arcing during soldering.
Lastly, the use of adhesives is a crucial aspect of the construction of a flex circuit. A wide variety of adhesives are available for flex circuits, and the selection should be based on the application and manufacturing process. Acrylics, epoxies and pressure-sensitive adhesives are some of the most popular options. The required level of tack and peel strength is another important factor in selecting the appropriate adhesive for a particular application.
The use of a flex circuit can dramatically decrease the weight of a product while still providing all the functionality and reliability of a traditional rigid PCB. This is due to the incredibly thin substrates of polyester or polyimide that are used. These can be printed with conductive material traces in as many layers as the design requires, and covered with a protective coverlay. If the product needs to be ruggedized, a layer of stiffener can be added for additional rigidity.