DISPENSE EXPERT - A GUIDE FOR UNDEFILL DISPENSINGFOR FLIP CHIP ASSEMBLY

摘要

Flip chip assemblies on organic (FR-4) substrates are becoming a focus of research endeavors due to theirrnadvantages such as the direct attachment of the silicon die onto the substrate and the use of area array format.rnHowever, these assemblies need to be underfilled with an epoxy encapsulant in order to compensate for thernCoefficient of Thermal Expansion (CTE) mismatch between the chip and the substrate. Dispensing the underfill is arncomplex process that requires a combination of materials, process, and design-related knowledge. A sub-optimalrnunderfill dispense process can result in defects including voids and inadequate fillets. Decision support in the formrnof a knowledge-based system would be invaluable to a process engineer involved in designing and implementingrnflip chip assembly processes.rnThe objective of this research effort was to design and develop 'Dispense Expert', a knowledge-based system thatrnserves as a guide for the underfill dispense process. Various stages in the development of 'Dispense Expert'rnincluding knowledge acquisition, knowledge representation, design of the inference mechanism, testing, and finallyrnvalidation are discussed. The outputs of 'Dispense Expert' include the volume of underfill required, time to flow,rnnumber of dispense passes required, size of the dispense needle, dispensing height, substrate preheat temperature,rnand curing time. 'Dispense Expert' provides an engineer with these critical parameters, which would otherwise berndetermined experimentally, saving considerable time and effort.