A system and method of thermal management of electrical and electronic systems and components that adequately maintains the temperatures of the system electronics and electrical devices within reliable limits during various postulated system malfunctions. The system and method use a phase change material (PCM). In at least some embodiments, the PCM is disposed such that, if a flow of coolant ceases when primary and backup control circuits are energized, primary control circuit temperature will exceed a predetermined temperature within a first time period after the flow of coolant ceases, and backup control circuit temperature will exceed the predetermined temperature a second time period, which is greater than the first time period, after the flow of coolant ceases.