How can the amount of dielectric material affect a PCB?

I understand that the dielectric material on a PCB (i.e. FR-4) can affect the capacitance of the board. But I don't understand why is that capacitance significant, and in what applications should the amount of dielectric material be taken into consideration?

PCB Design, PCB Materials
November 17, 2023

The capacitance formed between copper planes in different board layers is typically much smaller than the capacitance from discrete capacitors. but it has a very low parasitic series inductance and therefore is the most important capacitance for frequencies above a few 100 MHz. This frequency range is important for decoupling fast ICs or for handling ESD.

The capacitance between a trace and the plane underneath is important for transmission line impedance. A thinner dielectric reduces the characteristic impedance at the same dimensions. therefore trace dimensions can be smaller for the same characteristic impedance, which facilitates dense high-speed routing.

Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.

Oliver Smith

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