No description available.

The purpose of this work was to study the heating and curing rate of polymers with continuous and pulsed microwave radiation and compare with conventional thermal energy. The heating rate of poly(ethylene glycol) and poly(propylene glycol) has been studied as a function of molecular weight with pulsed as well as continuous microwave radiation, at constant average power. The curing rate of poly(amic acids) have also been studied with thermal energy, continuous and pulsed microwave radiation to better understand the interaction between pulsing the microwave and the polymeric material. Results from the heating rate studies indicate that the enhancement in heating rate with pulsed microwave radiation depends on the low frequency absorption spectrum (i.e., less than 10,000 Hz) of the polymer. The heating rate of poly(propylene glycol), which has a low frequency absorption, was enhanced by pulsing the microwave energy whereas the heating rate of poly(ethylene glycol), which does not have a low frequency absorption, remained the same when compared to continuous wave. Also results from the curing rate studies with poly(amic acids) indicate that the enhancement in curing rate observed in samples cured by microwave radiation as opposed to those thermally cured may be partially due to microwave power distribution in the cavity. This has been tested by agitating the sample to reduce any temperature gradient arising from the power distribution in the cavity. According to the experimental results, as the agitation rate was increased, the rate of imidization of poly(amic acids) with microwave radiation approached the rate of thermal imidization, at constant temperature. However, more research is required to clarify this complex phenomenon. / Master of Science

As the demand for microprocessors is increasing with more and more consumers using integrated circuits in their daily life, the demand on the industry is increasing to ramp up production. In order to speed up the manufacturing processes, new and novel approaches are trying to change certain aspects of it. Microwaves have been tried as an alternative to conventional ovens in the curing of the polymers used as underfills and encapsulants in integrated circuits packages. Microwaves however being electromagnetic waves have non uniform energy distribution in different settings, causing burning or incomplete cure of polymers. In this study, we compare the two main types of microwaves proposed to perform the task of curing the polymers. To limit the study and obtain comparable results, both microwaves were limited to propagate in a single mode, TE10. The first is a closed microwave cavity using air as the propagation medium, and the second is an open microwave oven with a PTFE cavity that uses an evanescent field to provide energy. The open air cavity was studied with different orientations of a substrate placed inside it so as to find the best case scenario in the curing process. This scenario was then compared with the best case scenario found for a sample cured in an evanescent field. This comparison yielded results showing an advantage of the open microwave in maximum field present, thus leading to higher localized energy absorption and temperatures in the substrate, however this case also lead to a higher temperature gradient. The substrate cured in the closed microwave has a lower temperature gradient, but also a lower maximum field which leads to slower cure. In the TE10 mode therefore, a closed microwave has an overall advantage as the heating process is only slightly slower than that of an open cavity, but the temperature gradient in this case is significantly lower.