Influence of continual mechanical stress on climatic ageing of conductive adhesive joints

0R0 resistors of the type 1206 were mounted on a test PCB with adhesive assembly to form adhesive joints. The joints were made of four types of electrically conductive adhesives. The adhesive joints were mechanically loaded by bonding of a test PCB with mounted resistors. Then the samples were climatic aged in relative humidity of 85 % at the temperature of 85 °C for 300 hours. The resistances of the joints and their nonlinearity of the current vs. voltage characteristic were examined. The joint resistance was measured using an LCR meter HP 4278 in by four-point method, the nonlinearity using a nonlinearity meter CLT 20. It was found that the mechanical stress in the adhesive joints causes changes of the resistance and nonlinearity of the joints and supports changes of these parameters induced by climatic ageing. It was also found that these changes are higher in comparison with the changes caused by the climatic load of the joints without the mechanical load. It is assumed that the changes of electrical parameters of the joints are dominantly influenced by changes of properties of tunnel barriers between filler particles caused by ageing.