Printable electronics: towards materials development and device fabrication

Purpose - There has been increasing interest in the development of printable electronics to meet the growing demand for low-cost, large-area, miniaturized, flexible and lightweight devices. The purpose of this paper is to discuss the electronic applications of novel printable materials. Design/methodology/approach - The paper addresses the utilization of polymer nanocomposites as it relates to printable and flexible technology for electronic packaging. Printable technology such as screen-printing, ink-jet printing, and microcontact printing provides a fully additive, non-contacting deposition method that is suitable for flexible production. Findings - A variety of printable nanomaterials for electronic packaging have been developed. This includes nanocapacitors and resistors as embedded passives, nanolaser materials, optical materials, etc. Materials can provide high-capacitance densities, ranging from 5 to 25 nF/in(2), depending on composition, particle size, and film thickness. The electrical properties of capacitors fabricated from BaTiO3-epoxy nanocomposites showed a stable dielectric constant and low loss over a frequency range from 1 to 1,000 MHz. A variety of printable discrete resistors with different sheet resistances, ranging from ohm to Mohm, processed on large panels (19.5 x 24 inches) have been fabricated. Low-resistivity materials, with volume resistivity in the range of 10(-4), 10(-6) ohm cm, depending on composition, particle size, and loading, can be used as conductive joints for high-frequency and high-density interconnect applications. Thermosetting polymers modified with ceramics or organics can produce low k and lower loss dielectrics. Reliability of the materials was ascertained by (Infrared; IR-reflow), thermal cycling, pressure cooker test (PCT) and solder shock testing. The change in capacitance after 3 x IR-reflow and after 1,000 cycles of deep thermal cycling between -55 degrees C and +125 degrees C was within 5 per cent. Most of the materials in the test vehicle were stable after IR-reflow, PCT, and solder shock. Research limitations/implications - The electronic applications of printable, high-performance nanocomposite materials such as adhesives (both conductive and non-conductive), interlayer dielectrics (low-k, low-loss dielectrics), embedded passives (capacitors and resistors), and circuits, etc.. are discussed. Also addressed are investigations of printable optically/magnetically active nanocomposite and polymeric materials for fabrication of devices such as inductors, embedded lasers, and optical interconnects. Originality/value - A thin film printable technology was developed to manufacture large-area microelectronics with embedded passives, Z-interconnects and optical waveguides, etc. The overall approach lends itself to package miniaturization because multiple materials and devices can be printed in the same layer to increase functionality.