Preparation Of Silver Conductive Ink And Its Performance In Inkjet Printing At Room Temperature

In the electronic industry, the fabricating of printed circuit boards and conductive lines is very important. Ink jet printing technology using conductive ink is a new technique to fabricate printed circuit board instead of the traditional method such as screen printing, etching and offset printing. Ink jet printing technology can use a variety of organic functional materials, as well as inorganic functional materials printing on the surface of various types of substrates directly without contact and mask, thereby a high precision conductive lines can be formed. Because of its simple process parameters, low requirements to the equipment, environment-friendly, this technology can be widely used in many fields such as flexible circuit boards, solar cell, biosensor, transparent conductive film, electromagnetic wave shielding material, radio frequency electronic tags.In this research, the conductive ink is been studied. Silver nanoparticles have been used as conductive component in the conductive ink. It has excellent electrical conductivity and stable chemical stability. Silver nitrate and hydrated sodium citrate were used as raw materials to prepare silver nanoparticles. Two different silver nanoparticles which have particle size of 20 nm and 50 nm have been prepared. These silver nanoparticles were used to prepare conductive ink. They are conductive ink with silver nanoparticles of 20 nm particle size and with silver nanoparticles of 50 nm particle size. And composite conductive ink contains silver nanoparticles with both particle sizes were prepared. The conductive ink were printed on the substrate to form conductive layer. The resistivity and the sintering morphology of the conductive layer were used to evaluate the properties of different conductive ink, wherein the 60% composite silver nanoparticles?20 nm particle size silver nanoparticles: 50 nm particle size silver nanoparticles = 2:1? conductive ink has the lowest conductivity which is only 3.576×10-6 ?·cm. The 60% composite silver nanoparticles conductive ink were used to study the relationship between the number of the printing layers and the sintering temperature. The experimental results show that when the printing number of conductive layers is 17 and the sintering temperature is 180?, the lowest resistivity is 3.542×10-6 ?·cm.When the conductive ink was printing on the Fuji photo paper substrate, the conductive layers can sintering at room temperature. The study of the surface structure of Fuji paper substrate shows that the silanol groups helps silver nanoparticles to sinter at room temperature. The mechanism for this is that the silanol groups break the coordination bond between the silver nanoparticle and the organic coating layer. The silver nanoparticles can touch each other and then sinter. According to this, NaOH solution, NaCl solution, Na₂CO₃ solution and Na₂SO₄ solution were used to print on the conductive layers. The results show that the NaOH solution and NaCl solution can make the silver nanoparticles sintered at room temperature. When print NaCl solution on the conductive layer, the resistivity of the conductive layer can be as low as 5.3×10-6 ?·cm.