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|Investigation of Polyimide/Carbon Nanotube Nanocomposites for High Temperature Electronic Packaging Applications|
|Keywords: Nanocomposites, Carbon nanotubes, Electronic packaging|
|Polyimide (PI) has been widely used in microelectronics as a substrate or interlayer, and the high Tg (>300oC) of PI makes it suitable for high temperature applications, such as devices in automotive, power electronics, measurement and control components of aircraft engines or well drilling. However, as a polymer, PI could lose weight, absorb waters and change shape due to thermal expansion, which is harmful for their reliability under high temperature service operations. In order to overcome these problems, inorganic materials such as Al2O3 or SiC are added into the polymer. Unfortunately, a large amount of inorganic additives increase the weight and weaken some other properties of polymers, such as flexibility. Carbon nanotubes (CNTs) which show light weight and superior thermal, electrical, and mechanical properties could be an attractive filler for polymer composite materials. However, due to Van der Waals¡¯ forces, CNTs tend to aggregate into clusters and bundles in a matrix. Thus preparing homogeneous dispersion of CNTs inside the polymer is difficult and therefore retaining this dispersion in the material treating process is significant for such applications. In this paper, surfactant-assisted polyimide/carbon nanotube (PI-CNT) composites were prepared by in-situ polymerization. The optical microscope showed homogeneous dispersion of CNTs after adding 2 wt% of surfactant, and the microstructure of cross section was displayed finer than that of the film without surfactant. Moreover, the coefficient of thermal expansion (CTE) of the PI-CNT film was decreased by 11% after adding the surfactant. The conductivity of the PI-CNT film with 1 wt% of CNTs assisted by a surfactant was 3.36¡Á10-7S/cm, which reached the antistatic criterion of thin films for space applications (1¡Á10-8S/cm). Reliability studies of high temperature and high humidity tests on the PI-CNT composites have demonstrated the potential applications of such materials for high temperature and humidity ambiance.|
|Qing-Yuan Tang, Student
City University of Hong Kong
Kowloon Tong, Hong Kong,