INVESTIGATION OF RESISTIVITY VARIATION OF PRINTED CIRCUIT BOARD LAMINATES DUE TO AGEING

The scope of this study 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 ageing tests relevant for harsh environment electronic applications as in avionic, space, defense, high energy physics and clinical radiotherapy. In fact, in all these applications the PCBs are subjected to energetic sources of various nature and high dose levels, which can produce relevant ageing, possibly modifying their dielectric characteristics. Conditioning processes related to irradiation considered in this study are the exposure to an ultraviolet source and to a 297keV electron beam. Moreover, relative humidity tests at room temperature (20C @ 50%RH and at 20C @ 90%RH) are performed to take into account of another important environmental factor that can affect dielectric characteristics through adsorption with long exposure time (20 days). The experimental procedure adopted considers a large number of samples (30) to assess mean value and variance of each surface and volume resistivity measurement.