Aging And Fatigue Of Aerosol Jet-Printed Nano-Ag Traces On Flexible Substrate

Conducting traces on a flexible substrate often have to survive significant and repeated deformation, making their fatigue resistance and the stability of it during long-term storage and use a potential concern. The question of stability is obvious in the case of, for example, screen or ink jet-printed traces where the organic matrix remains a critical part of the structure. We show it also to be important for nano-Ag traces that are sintered to ensure metallic bonding between the particles while eliminating most of the organics. We also show conventional accelerated aging tests to be potentially confusing or misleading for such traces, depending among other on practical limitations on sintering conditions. Examples are presented of how the fatigue resistance of application relevant aerosol jet-printed nano-Ag traces may degrade relatively rapidly at moderate temperatures. Even after "optimized" sintering at a much higher temperature subsequent aging at 75 degrees C for only 100 h led to an order of magnitude reduction in the fatigue life in subsequent mild cycling. The rate of degradation is certain to vary with the design and the ink used as well as with sintering conditions, making it important to account for it all in materials selection, process optimization, and assessments of practical life.