Processing And Application Research Of Nano Copper Conductive Ink

The development of printable electronics makes conductive ink more and morepopular. Nano metal based conductive ink with low sintering temperature, micro-sizeprocessing capacity and suitable for flexible printing becomes the most importantmaterial for printable electronics. In now, researches about conductive ink are focusedon nano silver conductive ink because silver has good conductivity and stableperformance. Copper has good conductivity too, and it is cheaper than silver, but it isunstable in the air. How to solve the problem of nano copper antioxidant and inventnano copper conductive ink is meaningful and important.This article describes a method of preparation nano copper based conductive ink,nano copper particles was prepared by laser heating, then the nano copper coated byorganic compounds for antioxidant and improving dispersion property. At last, nanocopper was mixed with solvent by grinding and ultrasonic dispersion.Then the properties of nano copper conductive were tested, the results are asfollows: diameter of copper particles dispersed in the ink is between78⁹8nanometer, the average particle size is88nanometers. The solid content of theconductive ink is15%to40%. The thickness of copper film printed by nano copperconductive ink that was measured by surface roughness tester and SEM images canreach1³μ m. The resistivity of copper film measured by four-probe method isabout2⁵×10^-5Ω cm, it is an order of magnitude higher than bulk copper.Adhesion of the conductive ink on polyimide was tested by cross cut10×10tapetest, the result indicated it has excellent adhesion.Copper film printed on polyimide passed through the hot and cold shock test（-40⁸0℃for30minutes,10cycles）without failure.Nano conductive ink can be printed by inkjet and scraping ink-mask lithography.Inkjet printing process can print conductive lines by CAD file directly, but the properties of conductive ink for inkjet printing have strict requirements and theprinting nozzle can be easily blocked. scraping ink-mask lithography process canprinting conductive lines with25μ m width.Nano copper can be sintered by oven, laser, UV（ultraviolet） and microwave. UVsintering with high sintering speed is an ideal sintering process for nano copperconductive ink. Oven sintering need a long sintering time and must be sintered invacuum or protective atmosphere. The surface and edge of copper films sintered bylaser is rough. The printed conductive ink without any sintering can not be heatedefficiently by microwave. SEM images of sintered copper films indicate that there areholes in the films.Several HF an UHF RFID antennas were printed on polyimide flexible board,then the printed UHF RFID antenna was packaged with RF chip by anisotropicconductive adhesive （ACA）. The reading distance of RF tag measured by RFIDreader can reach3meters. In addition, the nano copper conductive ink was used toprint PCB board, touch panel and membrane switch.