A new approach causing the patterns fabricated by silver nanoparticles to be conductive without sintering

Abstract

Silver nanoparticles (Ag NPs) with a mean size of about 90 nm were synthesized by polyol reduction of silver nitrate with ethylene glycol (EG) in the presence of poly(vinyl pyrrolidone) (PVP). The Ag NPs undergo a spontaneous coalescence in the presence of chloride ions even without a traditional sintering process which occurs at a relatively high temperature. Such behavior can cause a rapid decrease in the resistivity of the patterns fabricated by Ag NPs. Conductive silver lines were successfully fabricated on FR-4 substrate using this method. The resulting conductivity of the silver lines reached about 16% of the bulk silver value, which enables fabrication of conductive patterns on some electronic devices.

Room temperature sintering of printer silver nanoparticle conductive ink

“…4a. The nanoparticles also have a wide size distribution, which could be attributed to Ostwald ripening [3,9,16]. The presence of large particles suggests that sintering and growth possibly occurred.…”

“…1a. It has been reported that Cl -ions can cause the detachment of capping gents, such as PVP that surround the nanoparticles [3,9,16]. Due to high affinity of Ag with Cl -ions, PVP molecures are possibly desorbed from the surface of the nanoparticles.…”

“…The detachment of PVP probably causes destabilization, which increases the surface energy of the NPs. [3,9,16]. The atomic mobility caused by the increase in surface energy of the nanoparticles promotes agglomeration and their eventual sintering to further reduce the surface energy as shown in Fig.…”

“…However, such harsh process complicates printing on heat-sensitive substrates, such as paper and plastics [3][4][8][9]. There are different methods to achieve low temperature sintering, including low-pressure plasma [13], microwaves [14], laser [15], and use of chemical agents [3,9,16]. For example, patterns made of Ag NPs capped with PAA can undergo a built-in sintering mechanism due to exposure to NaCl [9].…”

“…For example, patterns made of Ag NPs capped with PAA can undergo a built-in sintering mechanism due to exposure to NaCl [9]. Similar approach was used to induce sintering of Ag NPs capped with PVP [16]. In this study, sintering of Ag nanoparticle ink prepared with PVP was achieved at room temperature using NaCl as sintering agent.…”