Microvias are conductive holes forming connections between HDI layers with an aspect ratio of 1:1. Blind Vias start on an outer layer but terminate on an inner layer. Buried Vias exist between inner layers and do not begin or end on an outer layer. Stacked Vias are infused with electroplated copper to interconnect high density layers. Stacked microvias are used if an essential blind via exceeds an aspect ratio of 1:1 phasing out sequential lamination due to a new blind via starting on the same layer that the aforementioned blind via ends. Staggered Vias are the most common and economical form of microvias. However, staggered microvias require more space as a result of not being built around the same core. Via Fill, or copper filled via, increases the thermal conductivity of the via by closing via hole with epoxy using a specific fabrication process. Any-Layer Vias are HDI layers that interconnect conductors on any layer with microvias when board is immensely cramped.
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