Abstract

Printing technologies provide a simple solution to build electronic circuits on low-cost flexible substrates. Materials will play important role for developing advanced printable technology. Advanced printing is relatively new technology and needs more characterization and optimization for practical applications. In this paper, the authors examine the use of different materials in the area of printing technology.

A variety of printable nanomaterials for electronic packaging have been developed. This includes nanocapacitors and resistors as embedded passives, nano laser materials, optical materials, etc. Materials can provide high capacitance densities, ranging from 5nF/inch² to 25 nF/inch², 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 1MHz to 1,000MHz. A variety of printable discrete resistors with different sheet resistances, ranging from ohm to Mohm, processed on large panels (19.5 inches x 24 inches) have been fabricated. Low resistivity materials, with volume resistivity in the range of 10-4 ohm-cm to 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 IR-reflow, thermal cycling, pressure cooker test (PCT) and solder shock. Change in capacitance after 3X IR-reflow and after 1,000 cycles of deep thermal cycling (DTC) between -55°C and 125°C was within 5%. Most of the materials in the test vehicle were stable after IR-reflow, PCT and solder shock.

Introduction

In recent years, significant progress has been achieved in the development of semiconductor packaging technology using various printing methods, such as screen-printing, ink-jet printing and microcontact printing. This trend is driven by demand for low-cost, large-area, flexible and light-weight devices. Since printing is inherently additive in nature, material and disposal costs are expected to be reduced, resulting in an extremely low net system cost. Most of the research activities in this printable area have been devoted to developing ink-jet solution-processable conductor materials [1-4]. Printable materials need to be chemically and physically inert to the other functional, dielectric, photoimageable materials processing in the same layer to preserve the structural and electrical integrity of devices/packages and they have to be operationally stable to sustain long operation life.

For these purposes, organic and polymeric materials have been widely pursued since they offer numerous advantages, including low-temperature processing, compatibility with organic substrates, stable, and significant opportunity for structural modification. Nanomaterials/composites/hybrids provide the greatest potential benefit for high-density, high-speed, miniaturized advanced packaging. The small dimensions, strength and the remarkable physical and electrical properties of these structures, make them very unique materials with a range of promising applications. Semiconductor devices based on functional polymers, composites, hybrids are considered to be very promising for electronic applications since they may potentially be fabricated entirely using similar printable polymer technologies where different active fillers can be introduced within the same functional polymer system.