The effect of thinner SDS-coated Ag NPs and organic carrier PVAc on properties of low-temperature silver paste

Low-temperature silver paste (LT-SP) is a critical conductive material for its use in flexible electronic devices. The high-purity thinner-coated Ag NPs with a size of about 100 - 200 nm are important for their oxidation resistance. Here, by adjusting mixed reduction of ascorbic acid (Vc), glucose (Clu), and sodium citrate (Na(3)Cit), with n(AgNO3): n(SDS) at 3:1, the size of obtained Ag NPs can be decreased to 158.1 nm. A simple natural precipitation purification was performed to obtain large-scale, thinner SDS-coated Ag NPs with lower energy consumption. With the increase of purification times from 1 to 3 and 5, the purification time was longer and longer, the surface coating layer decreased from 3.716 to 1.429 and 1.093 wt.%, and the size of the initial soft agglomerated Ag NPs gradually dispersed from 481.4 to 153.5 and 97.6 nm, indicating that the surface coating layer gradually became thinner. Considering the properties requirement/time-cost, 3 times purification was chosen. To improve the properties of LT-SP, a single green-white glue (PVAc) with excellent adhesion was used as the organic carrier, which was added to the obtained Ag NPs to produce a series of LT-SP samples. When Ag-4.8 wt.% PVAc, a low resistance of 6.2×10-8 Ω·cm could be obtained by sintering at 140 °C for 25 min, and excellent electrical conductivity was still maintained after 50,000 times bending. Its adhesion could reach the 4B standard confirmed by the Burger test. In summary, an excellent LT-SP can be large-scale produced with high-purity thinner SDS-coated Ag NPs and PVAc organic carriers.