The step of preparing flake-shaped silver-coated copper powder by mechanical ball milling is generally to spherical, quasi-spherical, or dendritic silver powder particles, which are repeatedly deformed, broken, welded, and diffused between atoms by mechanical ball milling. Flake silver powder. After the spherical silver powder was prepared by the PVD method, it was ball milled with ethanol solution of stearic acid as a grinding aid for 4 h to obtain a superfine flaky silver powder with a median particle size of 2.258 pum and good tableting effect and the ball milling time was studied. The effect of grinding aid type on the ball-milled silver-coated copper powder. Ammonia water is used as complexing agent and pH adjusting agent. Polyvinylpyrrolidone and Tween 80 double dispersant are used as the dispersing system. Hydration is used as the reducing agent. The original silver powder is obtained and then ball milled. The final irregular silver powder has a particle size of 2 ~4pm, the powder can be used alone as a silver powder for solar back silver paste.
However, there are many influencing factors in the ball milling process, and different batches of silver-coated copper powder produced by different processes, different producers, or the same producer in the same process are difficult to have consistent technical specifications. The flake-shaped silver-coated copper powder is the main body of the conductive silver paste, and its particle size, particle shape, particle size concentration, surface state, etc. have an important influence on the process performance and performance of the conductive silver paste. It is difficult for the flake silver-coated copper powder produced by different batches to be the same in size, average particle size, and surface condition, which is not conducive to the printing of silver conductive paste, the flatness of the printing is poor, and the uneven printed circuit is prone to generate fine cracks , Increase the contact resistance of the circuit. In addition, impurities are easily brought in during the ball milling process, which will cause hardening, not easy to achieve the required fineness, and affect the purity of silver powder. The purity of the flake-shaped silver-coated copper powder is not high, and may contain dissociable inorganic ions, which makes the preparation of the slurry and the sintering process and other conditions fail to meet the specified requirements, which eventually leads to the migration of silver and the increase of the product’s resistance. , Or even short circuit self-opening phenomenon.
Therefore, as long as the flake silver-coated copper powder produced by the mechanical ball milling method is effectively controlled during the manufacturing process, its shortcomings can be maximized and avoided, so as to achieve quantitative production applications in enterprises.