 Although most microvia reliability research focuses on single-level microvias, Birch tested multiple-level stacked and staggered microvias using IST test.Weibull analysis on the test data showed that single- and 2-level stacked microvias last longer than 3- and 4-level microvias (e. g. 2-level stacked microvias experienced about 20 times more cycles to failure than 4-level stacked microvias).One challenge for high density interconnect board development, is to fabricate reliable microvias, especially for stacked microvias, without resulting in incomplete filling, dimples, or voids in the copper plating process.