Challenges and Opportunities in Direct Write Technology Using Nano-metal Particles

Abstract

Direct write technology assists the electronic industry in their effort to miniaturize electronic circuits and enhance speed of printing capability. The technology allows printing various patterns without employing a mask or a resist with an enhanced speed with the aid of computer. This paper describes the current status of the synthesis of conductive inks, a key to success in this technology. There are numerous factors to overcome in manufacturing inks which meet all the necessary conditions of conductivity, viscosity, and stability. In order to achieve the required conductivity, nano-particles used in the ink have to be made from gold, silver or copper. Inherent problems involved in these metal powders include high melting point, coagulation, impurities, cost, and, in the case of copper, oxidation. The direction of research currently being carried out in meeting and overcoming various challenges in this technology is reviewed and discussed. Other salient applications of nano-sized metal powders are also briefly examined.

A chemical reduction approach to the synthesis of copper nanoparticles

“…Addition of sodium hydroxide augmented the rate of reduction [30]. Copper is easily oxidized with a small amount of oxygen present [11]. Consequently, the oxidation of metallic Cu is a key to the production of greater amount of cuprite instead of metallic Cu [17].…”

“…Oxidation of copper nanoparticles can be eliminated if the synthesis is conducted in the presence of CO or H 2 . On the other hand, handling these gases is rather cumbersome, and use of such gases is avoided when possible [11].…”

“…Among these processes, chemical reduction is usually preferred, because this method is easy, cost-effective and efficient, and it can apprehend improved size and size dispersion control by optimizing the experimental factors, for instance the molar ratio of the stabilizer with the precursor salt and the fraction of reducing agent with the precursor salt [16]. The rate of growth of the nanoparticles depends upon various variables, including the concentration of metal ions, the type of reductant, pH and temperature [11]. Time is also a key parameter in nanoparticles synthesis.…”

Effect of Lithium Ions on Copper Nanoparticle Size, Shape, and Distribution

“…Recently, there have been numerous studies regarding the manufacturing of nanosized metal particles on nanoink applications [1][2][3][4]. Metal inks containing nanoparticles can be used in the fabrication of a variety of printed electronics [5][6][7], such as flexible antennas [5], displays [8], and printed circuit boards [9].…”

“…Using the wet method, parameters such as particle size [19][20][21][22], shape [23,24], and distribution [25][26][27][28] can be controlled relatively easily. In the wet method, the size of the reduced particles is mainly influenced by factors like the concentration of metal ions, pH, temperature, and reducing agent [1]. In previous studies, the research team demonstrated that the aqueous electrical conductivity can be altered by the reducing agent and the concentration of metal ions in the solution, which can also influence the size of the nanoparticles [3].…”