Investigations of carbon nanotubes epoxy composites for electronics packaging

Abstract

The part of electronics packaging is steadily forced to adapt the requirements of the microelectronic industry. For future electronics application such needs will be: 1) steady miniaturisation of the electronic devices 2) high pin count up to 5000 i / o per device 3) pitches down to 20 mum 4) higher current density per devices 5) higher thermal dissipation loss This is only a small extract of the challenges facing the electronics packaging industry in the future. The aim and duty for electronics packaging is to realize a reliable package for future electronics. Commonplace materials for joining elements like solder are not able to solve these requirements. For example in [1] the authors describe that future IC's operating at high frequencies of 10-28 GHz, signal bandwidths of 20 Gbps and lower supply voltages require an estimated maximum of R (< 10 mOhm), L (<5-10pH) and C (<5-10 fF).[l] Current joining elements can not meet these requirements. To solve these problems the electronics packaging industry researches technologies and materials of the nanotechnology. Especially researches concerning new materials for electronics packaging rise up since the last three years. One of the most researched new materials are Carbon Nanotubes (CNT). Carbon Nanotubes have superior mechanical, electrical and thermal properties. Due to these properties CNT are considered as promising candidates in packaging technology. The most interesting field of application is the use of the Carbon Nanotubes as filler in electrical conductive adhesives. The aim is to improve the performance of conductive adhesives in comparison to common products. This study deals with characterization of carbon nanotube / epoxy adhesives in electronics packaging. For this study we optimize the CNT - adhesive system by modification of the CNT, use of different dispersion technologies and under variation of the epoxy matrix. The resulting adhesives are characterized by measuring their viscosity, mechanical strength and their thermal and electrical conductivity. For all studies Multi Wall Nanotubes were used which can be purchased at a reasonable price. For modification of the CNT they can be treated by low pressure plasma (cvd), UV / ozone treatment or modifiedchemically in solution to achieve a higher polarity resulting in a better dispersibility. Also bonding to the polymer matrix is improved. Success of the processes is studied by XPS and REM. For dispersion technology ultrasonic bath, speed mixing and/or treatment with a roll calander can be used. The polymer matrix is also varied in order to achieve an appropriate viscosity at the CNT-content of interest that enables good results in screen printing. Also CNT-polymer interaction can be adapted by varying polarity of the resin used. The distribution of CNT in the matrix is studied by TEM. The first investigations show that ultrasonic finger is the favourable dispersion technology to achieve well dispersed CNT. For modification of the CNT the plasma treatment came out to be efficient to give appropriate amounts of hydroxyl groups.