High-frequency circuit boards refer to special PCB circuit boards with higher electromagnetic frequencies. They are used in high-frequency (frequency greater than 300MHZ or wavelength less than 1 meter) and microwave (frequency greater than 3GHZ or wavelength less than 0.1 meter) fields. They are produced on microwave substrate copper-clad boards using some processes of ordinary rigid circuit board manufacturing methods or using special processing methods. Generally speaking, high-frequency boards can be defined as circuit boards with frequencies above 1GHz.