Propensity for Pad Cratering Evaluation in Board Resin and Board-Resin/Glass Interface Under Assembly and Rework

Abstract

Abstract. Pad cratering is a major concern in high I/O ball grid array packaging architectures. Assessment of propensity for pad cratering is presently beyond the state of art. Failure in pad cratering is manifested through the fracture of the bulk resin below the interconnect pad, followed by the fracture at the resin-glass weave interface in the organic laminate. A new metric has been proposed and evaluated for assessing the propensity for pad cratering. A model has been developed using experimental measurements to predict pad cratering resistance, identifying the resin-glass-reflow process condition combinations that have the lowest propensity for pad cratering. Experimental data have been measured by analyzing the bulk behavior of the resins using a tensile specimen and by measuring the fracture toughness at the resin-glass interface through measurement of a specifically fabricated resin-glass bimaterial interface specimen. A total of 12 different resin formulations were studied to quantify the material properties under various reflow exposure conditions, ranging from no-reflow to six-reflow conditions. A four-point bend interface specimen was used for the measurement of the fracture toughness of the resin-glass interface. The interface behavior was measured for 30 glass-resin interfaces consisting of 15 resin types and three glass styles as a function of mode-I stress intensity factor to pristine, two reflow, and six reflow conditions. Multiple replicates have been tested for each combination to create a massive dataset. A predictive model has been developed to assess the pad cratering resistance for resin-glass-reflow condition combinations using principal component regression on experimental data, with the newly developed pad cratering resistance metric as the response variable. The model has been assessed for accuracy versus test data.