Resistance of conductive adhesive joints on non-noble surface finishes

Electrically conductive adhesives (ECAs) have number of advantages comparing to solder joints. They are environmentally friendly and have lower processing temperature that makes them suitable for manufacturing of LCD's or connecting flexible solar cell arrays in modules. However, in flexible solar cells the metal contact is usually made of non-noble metal, and this joint can suffer from decrease of conductivity at the operation environment. In this work the joint behavior between different metal surfaces (Au, Sn, Mo) and ECAs during different ageing conditions is investigated. The aim of the work is to investigate the degradation of non-noble metal-ECA joints in order to predict the reliability of such an electrical contact. The results of the literature review and ageing experiments are presented. The ageing conditions were 120 °C thermal ageing and damp heat test (85 °C/85RH). The test samples were manufactured on FR-4-boards with metal stripes and applied ECAs between them. The experiments are focused on the electrical conductivity. The experiments have shown significant increase in joint resistance after 85 °C/85RH, while under 120 °C ageing a slight decrease was observed.