One-step synthesis of micro-sized flake silver particles as electrically conductive adhesive fillers in printed electronics

A novel one-step liquid phase reduction method was proposed to synthesize uniform micro-sized flake silver particles at room temperature. The La(OH)3 was used to replace other expensive agent (H2PtCl6 or H2PdCl4) as structure-directing agent. The role of the reagents and possible formation mechanism of micro-sized flake silver particles were investigated in detail. The effect of each synthesis parameter on morphology and particle size of micro-sized flake silver particles was also explored. It is found that La(OH)3 could control the reduction rate of Ag+ and its oriented growth by adsorbing on the (111) crystal plane of silver particles. The uniform micro-sized flake silver particles with a length of 4-55 μm and thickness of 0.2-5 μm could be synthesized by tuning the synthesis parameters. The synthesized micro-sized flake silver particles presented a smoother and straighter surface compared with commercial micro-sized flake silver particles prepared by ball milling. What is more important, the electrically conductive adhesive (ECA) filled by as-prepared micro-sized flake silver particles printed on polyethylene terephthalate film (PET) exhibited lower bulk resistivity (about 4.4×10-5 Ω·cm) than that filled by the commercial ball-milled micro-sized flake silver particles with the same Ag content of 80 wt. % (about 1.2×10-4 Ω·cm).