Diagnostics and aging of electrically conductive adhesives

Resistance and nonlinearity of the current vs. voltage characteristics (NAVC) of adhesive joints was investigated. The joints were prepared of four types of electrically conductive adhesives (ECA) on Cu clad FR4 laminate and on Cu clad FR4 laminate with gold coating on the Cu. The circuit layer was designed to make 4-point measurements possible. Adhesives were applied by dispensing. The boards were assembled by resistors of the value 0 /spl Omega/ recommended for assembly using adhesives. The samples were aged at the temperature of 200/spl deg/C and 160/spl deg/C, respectively, for different time. Significant changes of resistance and NAVC were found during aging of adhesives. It was found that NAVC is a parameter, which is very sensitive to changes of ECA and therefore could be very useful for diagnostics of these materials.