“Green” nanocomposites for electronic packaging

This paper examines the use of nanocomposites in the area of ldquogreenrdquo technology. A variety of green materials for advanced organic packaging have been developed. These include capacitors and resistors as embedded passives, resin coated Cu (RCC) as buildup layers, highly conducting nano-micro media for Z-interconnects, lead free assembly paste, ZnO based additives and magnetic materials. Nanocomposites can provide high capacitance densities, ranging from 5 nf/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 capacitance over a temperature range from 20degC to 120degC. A variety of printable discrete resistors with different sheet resistances, ranging from 1 ohm to 120 Mohm, processed utilizing a large panel format (19.5 times 24 inches) have been fabricated. Low resistivity nanocomposites, 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. A variety of metals including Cu, Ag, LMP (low melting point) and LMP-coated Cu fillers have been used to make halogen free, lead free electrically conducting adhesive technology as an alternative to solders. Halogen free resin modified with ceramics/organic particles can produce low Dk resin coated Cu (RCC) with Dk value in the range between 4.2 and 3.2. Similarly, low loss RCC materials can be produced by combining HF resin with low loss fillers. The mechanical strength of the various RCC was characterized by a 90 degree peel test and measurement of tensile strength. RCC exhibited peel strength with Gould´s JTC-treated Cu as high as 6 lbs/inch for halogen free RCC. These halogen free RCC materials exhibit coefficients of thermal expansion (CTE), ranging from 27 ppm/degC to 32- ppm/degC. Altogether, this is a new direction in the development of Green Packages and more specifically in the development of coreless substrates for semiconductor packaging.