**2.1 Test sequence**

The tests were programmed in sequences, to show the progressive deterioration (if any) of the PI properties. The test logic is shown in **Figure 3** and follows the ideas reported in [17]. Aging is subdivided in aging sub-cycles followed by diagnostic sub-cycles. During the diagnostic sub-cycles, measurements apt to infer the degradation of the PI films as electrical insulators are carried out. The samples that during the tests are modified by the test itself are discarded, and aging continues with the remaining samples. Therefore, PI films were prepared in large numbers to ensure that aging tests could be performed on different samples to highlight the degradation of PI dielectric properties (and not the effect of previous tests).
