Due to the unparalleled advantages of nano silver, developed countries are vigorously developing new nano silver conductive inks to meet the needs of various printed electronic products, such as RFID ultra-high frequency (UHF) antennas, membrane keyboards and switches, PCBs, Battery testers, flexible displays, electromagnetic wave shielding materials, etc. At present, nano-silver conductive inks with a particle size of less than 20 nm have been successfully commercialized. With a super printer, a wire with a line width/spacing of only 3 μm ~ 5 μm can be produced, which is nearly 90% less than ordinary screen printing. This type of nano silver conductive ink has five main characteristics.
1. Low sintering temperature
The sintering temperature of nano-silver decreases as the particle size decreases, thereby expanding the selection range of substrates, which is its most useful feature in printed electronics. For example, the sintering temperature of ultra-fine metal powder (50 nm in diameter) of Japan’s Daiken Chemical Industry Co., Ltd. is 300 ℃, which can only be screen printed on PI (polyimide) and glass substrates; while the US NanoMas company NTS05IJ40 type The sintering temperature of nano silver conductive ink (particle size <10 nm) can be reduced to 70 ℃ ~ 150 ℃, not only can be deposited on PI, but also can be quickly deposited on low-cost plastics and flexible boards with low Tg, such as PET (Polyethylene terephthalate), paper, etc.
2. Unique conductivity
Silver not only has excellent electrical conductivity, but also has good chemical stability and is not easily oxidized. Even if the surface is partially oxidized due to the preparation process or environmental factors, the generated oxide can also conduct electricity. Therefore, the nano-silver conductive ink is easy to prepare and stable in operation, and no special anti-oxidation measures are required. It is worth mentioning that this advantage is beyond the reach of many metal materials such as copper.
3. Excellent thread quality
The wires made by the combination of nano-silver conductive ink and inkjet printing process have better overall performance. For example, compared with flat and screen-printed silver wires and screen-printed copper wires, wires printed by nano-silver conductive ink have higher resolution, better conductivity, and denser structure. As well as a brighter surface, it has stronger moisture and corrosion resistance than silk-screened copper wires.
Four, good adhesion to the substrate
The nano-silver has a large specific surface area, which means that the number of atoms per unit area increases, which improves the adhesion to the substrate and makes the nano-silver conductive ink difficult to fall off. These advantages make it possible to print electronic products with more complex structures and larger areas on flexible boards.
Five, rich application experience
In the field of printed electronics, silver ink has been used as one of the main materials for screen printed electronic products for many years. It can be said that the use of silver ink has accumulated rich experience, which has laid a certain foundation for the research and development of nano-silver conductive ink.