Síntese de nanopartículas metálicas e uso de grafeno para tintas condutivas aplicadas a blindagem eletromagnética

Abstract

The development of conductive inks has increased recently, especially in the microelectronics industry. Micro and nanoparticles of copper or silver are generally used in the composition of inks, but the high cost of silver and the oxidation of copper are challenges for industrial use. Another option is the use of particles with a copper core covered by silver (Cu-Ag), also called core-shell, as it overcomes both limitations of the pure metals mentioned. Graphene is another conductive nanomaterial emphasized in scientific studies to formulate new inks. A silver ink painting of the system in a package (SiP) chip is a technology that produces a conductive film covering these devices against electromagnetic interference (EMI). This is an alternative method to metal cans that have been used in the shielding of these microchips. Nevertheless, painting with Cu-Ag or graphene inks can reduce the amount of silver, becoming an opportunity for innovation. Furthermore, it reduces production costs and generates environmental gains through metal cans. Therefore, this research proposes using conductive inks with these nanomaterials as an alternative to forming films for electromagnetic shielding and painting SiP chips to cover it. The objective was to synthesize and disperse Cu-Ag particles for the formulation of metallic paints and a water-based graphene suspension for electromagnetic shielding. The morphology, size, chemical composition, and crystalline phases of the particles used techniques of atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), light diffraction, and X-ray diffraction (DRX). Films were produced by casting and spray painting to measure resistivity, test substrate adhesion, and electromagnetic shielding, including evaluating coverage on SiP chips. The Cu-Ag particles had different shapes with complete and partial coverage of silver on copper. The few-layer and multilayer graphene were used. The Cu-Ag ink showed an electrical resistivity of 10-04 Ω.cm at 200 °C, while the graphene suspension 10-02 Ω.cm at 300°C. PET presented better adhesion in the test on different substrates according to standard d3359. The shielding efficiency was -44 dB for CU-Ag ink and -9 dB for graphene suspension, according to ASTM d4935.