The characteristics of high frequency PCB are as follows:
1. DK should be small and stable enough, usually the smaller the better. High DK may cause signal transmission delay.
2. DF should be small, which mainly affects the quality of signal transmission. A smaller DF can reduce signal loss accordingly.
3. The thermal expansion coefficient should be the same as the copper foil as much as possible, because the difference will cause the copper foil to separate when the heat and cold change.
4. In a humid environment, the water absorption rate must be low, and the water absorption rate is high, which will affect DK and DF.
5. Heat resistance, chemical resistance, impact resistance, and peel resistance must be good.
