Performance and Reliability of SMD Interconnections using Low-Temperature Solders and ECAs for FHE Applications

Developing component attachment techniques with mechanical reliability is required to implement flexible hybrid electronics utilizing additively printed circuits. Additive electronics may be made on several substrates, such as Polyimide, PET, and PEN. A variety of novel solder materials have emerged that can be processed at temperatures in the range of 150 degrees Celsius. The low temperature also provides the added benefits of less warpage, less energy use, and a reduced carbon footprint. The connection of components and the investigation of performance and reliability at various mechanical motions, such as folding, flexing, and twisting, is not well known. Prior research has concentrated on electrical conductivity during post-heat treatment, different sintering techniques, thermal behavior, and thermal cycling. This paper has studied the mechanical performance and reliability of the SMD component attachment under folding stress. The bonding materials used in this application are direct-write printable electrically conductive adhesive (ECA), a magnetically oriented anisotropic conductive adhesive (ACA), and low-temperature solder (LTS) on the printed conductive metallization. In flex-to-install applications, the reliability and performance deterioration of additively printed circuits have been measured to understand the cycles to failure under loading stress. The statistical analysis of the cycles to failure using the Weibull distribution has been used to predict the failure.