Ultra Low Resistivity and High Electrical Stability Silo-Ag ECAs Produced from Curing Chemistry Optimization for Flexible Electronics

Highly conductive and both mechanically and electrically stable polymer-based adhesive composites are now more extensively used in die attachment, flip-chip interconnections, surface mount interconnections, and are especially important to flexible and wearable electronics. To enhance conductivity, most researches devoted to filler surface engineering and largely neglected network development of polymer matrix. While ultra low resistivity has been achieved, most of these electrically conductive adhesives (ECAs) display poor electrical stability under reversed mechanical deformation. For practical implications to wearable electronic applications, the performance stability of ECA under reversed deformation under relatively small strains of human movement is of critical significance. We investigate the effect of polymer matrix stoichiometry during curing on the conductivity and electrical stability of silver-poly(dimethyl siloxane) (PDMS) ECA composites. Characterization of crosslinking density reveals a competition between crosslinking reaction and surfactant reduction with silver flake sintering during curing, leading to a tradeoff relationship between stretchability and electrical conductivity. By tuning the crosslinking functional group ratio, the best combination of ultra-low resistivity of 1.33×10
^-4
Ω·cm and high stability of 22.2% increase in resistivity after 100 cycles of tensile 0-25% tensile straining is achieved at an intermediate hydride-to-vinyl group ratio of 1:2.