Role of dielectric material and geometry on the thermo-mechanical reliability of microvias

The Microvia Substrate technology will play a crucial role to accommodate high I/O's of fine-pitch area-array packages such as flip chips and chip scale packages, which are needed to meet the demands of high functionality and performance of the electronic industry. A comprehensive experimental and theoretical program is underway at the Georgia Institute of Technology to develop the microvia substrate technology. The experimental aspect of this program involves fabrication in a class 1000 clean room facility to understand the effect of process parameters on yield and reliability of the microvia and high density wiring (HDW) structures. The theoretical program aims to understand the mechanics of deformation and thus predict and enhance the reliability of the HDW structures. The focus of this paper is a) to understand the effect of processing parameters on yield b) to characterize the effect of microvia geometry parameters on the evolution of strain and c) to determine the effect of dielectric material property on the thermo-mechanical reliability of the microvias. Finite element simulations were carried out with different microvia diameters to understand the failure mechanisms of these structures. The reliability predictions are compared with thermal cycling test data of the test vehicles. This current study will help to develop upfront design guidelines to fabricate thermo-mechanically reliable microvias.