최적화 실험설계법을 적용한 무전해 은 코팅 구리 입자 제조

Abstract

The distinct properties of metallic particles have given somebody to new applications and possibilities of making new products such as electronic, optical, and magnetic devices, nanoelectromechanical system, energy conversion and photothermal devies, catalysts, biosensors, biolabels and drug delivery system, conductive coatings and pigments for inkjet inks. In addition, the metallic particles used as electrically and thermally conductive fillers for polymeric materials typically consist of gold, silver, copper, nickel or aluminum. Generally gold and silver while processing outstanding conductivity properties are, however, expensive. Copper and nickel display good electrical conductivities but are deleterious sensitive to oxidation, resulting in the concomitant diminution of useful properties of a kind that quality and stability. In order to get over the problems connected with the oxidation of copper and nickel, or the high cost of using silver, the substitution by silver coated on copper particles for solid silver particles has been investigated. Generally, particles coating treatment can be achieved by electroless plating, electroplating, and vacuum process(evaporation, sputtering etc.). It is well known that silver can be deposited on many substrates by electroplating. However, electroplating and vacuum coating for particles is effectiveness. Consequently, they are not possible for commercial purpose. Electroless silver coated on copper particles, however, can be successfully achieved on copper particles and has much higher deposition rate than electroplating, although there are still problems in decrease process steps and coating on the copper particle which would have good sinterability. This study indicates that silver coated on copper particles approaches the ideal materials for this purpose. There are many important parameters to prepare micro sized particle with uniform silver layer. In the formation of silver coated on copper particles, there are several important factors to prepare those particles. Properties of then obtained by electroless plating method are affected by three parameters such as the molar ratio of AgNO3/NH4OH, feeding rate time and reduction time. The interrelation ships between the above parameters are complex, and the analysis of this electroless plating system to optimize the factors is a time and labor consuming work. Therefore, Taguchi optimization method was introduced in this study. Taguchi method is a combination of mathematical and statistical techniques used in an empirical study. It is economical for characterizing a complicated process. It uses fewer required experiments in order to study all levels of all input parameters, and filters out some effects due to statistical variation. Taguchi method can also determine the experimental condition having the least variability as the optimum condition. The variability of a property is due to ‘noise factor’, which is a factor difficult to control. On the contrary, the factor that is easy to control is called ‘control factor’. The variability can be expressed by signal to noise (S/N) ratio. The experimental condition having the maximum S/N ratio is considered as the optimal condition, as the variability of characteristics is in inverse proportion to the S/N ratio. The objectives of this work are : (1) to suggest a method for the formation of silver coated on copper particle with sub-micron size by using a electroless plating method, (2) to apply the Taguchi method on the optimization of characteristics and to obtain the silver coated on copper particles by using optimal synthesis conditions, and (3) to evaluate the effect of several parameters on the electrical conductivity of silver coated on copper particle.