Application of More-level Stress on Conductive Adhesive Joints

Three types of stresses have sequentially loaded adhesive joints formed of three types of adhesives with isotropic electrical conductivity. One type of the joints has been prepared by mounting of jumpers (0R0 resistors, type 1206) on the test board. For manufacturing these joints adhesives SC 70MN and Permacol 2369/2 have been used. The second type of the joints has been formed by printing of lines from adhesive between neighbouring pads. Adhesive CW 2200 has been used for manufacturing of these joints. The adhesive joints have been first stressed mechanically by deflection of the board with mounted resistors, then by the thermal shocks -40
^o
C/+80
^o
C and then at the combined climate 80
^o
C/80 % RH for 300 hours. Before and after every type of the load the joints resistance has been measured. It has been found that the mechanical stress as well as stress caused by the thermal shocks have had only low influence on the joints resistance. On the other hand, stress in the combined climate temperature/humidity caused significant changes of the joints resistance due to the penetration of water molecules into the adhesive and affecting quality of the insulation barriers between the filler particles.