Traditional single-level microvia structures generally are considered the most robust type of interconnection within a printed circuit board substrate. However, rapid implementation of high-density interconnect technology now commonly requires two, three or even four levels of microvias sequentially processed into the product. Stacked microvias require duplicating and/or additional process steps in fabrication, including filling of the microvia, which establishes an ability to sequentially ablate additional vias into a structure containing microvias stacked on both sides of the substrate (FIGURE 1).
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