A particle-free silver precursor ink useful for inkjet printing to fabricate highly conductive patterns
A particle-free silver precursor ink suitable for inkjet printing was developed using silver citrate as the functional material and ethylenediamine as the complex solvent. The long-term storage stability and satisfactory printability of this ink have been proved and it was successfully printed on a flexible polyimide slice using a commercial printer. Its efficient catalytic activation for subsequent electroless plating was confirmed by the rapid growth of copper layers, and the resulting copper layer exhibited a compact, uniform and well-crystallized structure. The electrical resistivity as low as 2.80 μΩ cm (1.67 times larger than that of bulk copper) and adhesion on a polyimide substrate as high as 5B category according to the ASTM D-3359 could be achieved for the copper layer. In addition, copper tracks as narrow as 61 μm could be obtained based on the inkjet printing of this ink followed by electroless plating. These results suggest the great potential of this particle-free precursor ink in the field of flexible printed electronics.