Conductive paste is the basis for the development of electronic components and a key material for packaging, electrodes and interconnections. With the development of electronic components toward miniaturization, precision, and flexibility, research on the nano-conduction of metal conductive fillers is being carried out at home and abroad. Among them, nano-silver filled conductive paste has become a research hotspot in this field. There is no uniform conclusion on whether nano-silver as a conductive filler affects the properties of silver paste. It is generally believed that nano-silver is filled into the matrix, because the contact point area between the particles is small, the number of filler particles increases and the contact resistance increases. Only when the distance between nano-silver is within a certain range, the conductivity is enhanced due to the tunnel effect and the like. This is mainly related to its particle size and morphology, surface properties and sintering behavior.
Electrically conductive paste is the basis for the development of electronic components and the key material for packaging, electrodes, and interconnections. It is mainly used in various areas of the electronics industry such as surface packaging technology and sensitive components. In recent years, with the rapid development of the information industry, devices have been developed in the direction of miniaturization, precision, and flexibility. Many domestic and foreign scientific research institutions have developed great interest in the development and application of conductive pastes.
The conductive paste is generally composed of 2 to 3 basic parts, namely the conductive phase (gold, silver, copper, nickel and tin-bismuth alloy, etc.), organic vehicle (organic resin and solvent) and / or permanent adhesive (silicic acid Salt glass, etc.). According to the properties of the composition of the conductive paste, the conductive paste is roughly divided into an organic conductive paste, an inorganic conductive paste, and a composite conductive paste. Among them, the composite conductive paste uses conductive metal particles as the conductive phase and high-molecular polymer as the binding phase. It has excellent conductivity and mechanical properties. The processing process is relatively simple, the repeatability and conductivity are strong, and the storage is stable. It has a longer period, has higher practicability, and has a wide application prospect. At present, most of the conductive pastes on the market are of this type.
Silver has a high electrical conductivity, excellent physical and chemical properties, acceptable prices and its oxides also have conductive properties and other characteristics are widely used as conductive fillers. Conductive silver paste is moving in the direction of simplified process, stronger performance, higher reliability, and lower cost. At present, the conductive phase in the conductive silver paste is mainly micron or submicron silver powder, and these pastes cannot meet the requirements of new technologies such as low temperature sintering and multilayer wiring. In recent years, domestic and foreign researches on the nanometerization of conductive paste precious metals are being carried out, and a certain degree of industrialization has been formed. Due to the surface effect and small size effect of nano-silver, using nano-silver as a conductive filler can improve electrical conductivity and thermal conductivity; reduce the amount of silver and reduce production costs; reduce the curing temperature, so that silver paste can be applied to PET templates, flexible substrates, etc .; The surface of the layer of the welded metal and ceramic is very flat; the shear strength of the conductive adhesive is improved. In addition to the obvious advantages mentioned above, there are also problems such as poor dispersion stability of the slurry, extremely easy to appear agglomeration and sedimentation of nano-silver after placement, unstable electrical conductivity and short adaptation period.
At present, the preparation method of nano-silver filled conductive paste is similar to the preparation method of micro-silver paste, mainly using commercially available or self-made nano-silver in dry powder or liquid form, alone or mixed with micro-silver flakes, mechanical stirring, and ultrasonic Dispersion, high-energy ball milling and other methods to disperse into the organic vehicle.