Power cycling has been done for flip-chip and CSP components solder joined onto ceramic substrates. Cycle periods as short as 1 min were applied in the experiments where the chip temperature varied between about 30°C in the power off-state and 100–150°C in the power on-state. Disconnections of the joints were found after 4000–17 000 power cycles. The flip-chip components joined onto low temperature cofired ceramic substrate showed slightly better reliability than the components joined onto alumina substrate. Most of the samples showed clear effects of deterioration of the joints seen as increasing chip temperature for power on-state. The experimental results are compared with calculations based on modified Coffin–Manson equation as well as with one-dimensional simulations.