A tale of four substrates-EMI and thermal comparisons of different PCB materials

It is well known that EMI and thermal performance need to be considered together, as reducing the speed of a signal to reduce its emissions will in most situations increase the power dissipation in the driver for that signal. This paper compares the electrical (low and high frequency including EMI effects) and thermal properties of 4 substrates: (1) “standard” epoxy type (types FR-4, FR-N including thin substrates on rigidisers); (2) “flex” substrates; (3) LTCC (low temperature cofired ceramic) substrates; and (4) diffusion patterned substrates. This allows a designer to take as complete view as possible in the choice of a substrate for a given application. It also shows that it is possible to simulate a circuit including the substrate as part of a system to see the EMI and thermal effects