Investigation of Resistivity Variation of Printed Circuit Board Laminates Due to Aging

The scope of this paper is the characterization of the variation of surface and volume resistivities of printed circuit board (PCB) laminates, such as standard epoxy, polyimide, and Thermount, when subjected to different aging tests relevant for harsh environment electronic applications as in avionic, space, defense, high-energy physics, and clinical radiotherapy. In fact, in all of these applications, the PCBs are subjected to energetic sources of various nature and high-dose levels, which can produce relevant aging, possibly modifying their dielectric characteristics. Conditioning processes related to irradiation considered in this paper are: 1) the exposure to an ultraviolet source; 2) irradiation with a 297-keV electron beam; and 3) relative humidity (RH) tests at room temperature (20^°C at 50% RH and at 20°C at 90% RH), which are performed to take into account another important environmental factor that can affect dielectric characteristics through absorption with long exposure time (20 days). The experimental procedure adopted in this paper considers a total number of 30 samples to assess the mean value and variance of each surface and volume resistivity measurement.