Should You Choose Hard or Soft PCB Materials?
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These materials differ in their rigidity and various other characteristics, resulting in differences in how readily they can be transformed into high-frequency circuits.
Materials for printed circuit boards (PCBs) can contribute a great deal to the success or failure of a final circuit design, since those materials affect thermal behavior as well as the electrical and mechanical characteristics of the circuit. At one time, the choice in RF/microwave circuit-board materials was simply between a “hard” or rigid circuit material, typically based on some form of ceramic material, and a “soft” or flexible type of circuit material, often based on Teflon or polytetrafluoroethylene (PTFE) with some form of filler.
The number of circuit material choices has grown with time—with circuit materials now available optimized for specific types of designs, such as antennas, or even frequency ranges, such as millimeter-wave frequencies—although most of the materials can still be categorized as being hard/rigid or soft/flexible in nature. Reviewing some of the differences between the two basic types of RF/microwave circuit materials may help clarify when it makes the most sense to use one type or another for a particular high-frequency application.
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