Copper and silver microparticles for high-performance conductive inks in electronic chip shielding

Abstract

The development of conductive inks has increased in recent years, especially for applications in electronic devices. Inks can be applied by spraying on the IoT chips and forming a shield against electromagnetic interference (EMI). This technology is called conformal shielding, which reduces EMI on the component. Micro and nanoparticles of copper or silver are often used in the composition of the inks, but the high cost of silver and the oxidation of copper limit the application. Another option is using particles with a copper core covered by silver (Cu–Ag), as it overcomes both limitations of the pure metals mentioned. So, there is an opportunity to use these conductive inks as an alternative to traditional EMI shielding methods such as metal cans, sputtering coating, and electroless nickel. Therefore, this work synthesized Cu–Ag particles to use in a conductive ink applied by spray coating. The film's resistivity and shielding effectiveness (SE) were measured. The morphology, size, and chemical composition of the particles were evaluated. The particles presented an irregular shape with complete and partial coverage of silver over copper. The ink showed an electrical resistivity of ∼10−04 Ω cm at 200 °C in sintering. It was also tested on different substrates with better adhesion to PET. The shielding efficiency was −44 dB according to the ASTM d4935 norm. A painting on the chips with a low-thickness film covering all modules demonstrated suitability to conformal shielding.