On the integration of microwave curing systems into microelectronics assembly processes

In microelectronics packaging applications a variety of thermosetting polymer materials is applied. Such materials are dispensed in a liquid form and are heated with the intent to cure them. Conventional processes often take several hours to bring the material up to temperatures which result in a significant rate of cure. An alternative approach to curing thermosetting polymers is the use of microwave energy, which has been shown to cure encapsulant materials in substantially shorter times. A recent innovation is the open-ended microwave oven proposed by Sinclair et al.. This paper deals with the implementation of the open-ended microwave oven into a precision placement machine. Two test products for encapsulation and flip-chip serve as objective for microwave-assisted assembly. An integrated system setup including the open ended oven is presented. Modifications on the open-ended microwave oven are described and a concept for the development of an embedded microwave curing system is presented. Tests on curing encapsulant materials dispensed over a commercially available QFN were performed to determine post-process functionality of the package, with no evident detrimental effects.