Metallic interlocking structure

1. Technical Field An electronic structure including a metallic interlocking structure for bonding a conductive plated layer to metal surface, and a method of forming the electronic structure. The method provides a substrate having a metallic sheet within a dielectric layer. The metallic sheet includes a metal such as copper. An opening in the substrate, such as a blind via, is formed by laser drilling through the dielectric layer and partially through the metallic sheet. If the opening is a blind via, then the laser drilling is within an outer ring of the blind via cross section using a laser beam having a target diameter between about 20% and about 150% of a radius of the blind via cross section. A surface at the bottom of the opening, called a "blind surface," includes a metallic protrusion formed by the laser drilling, such that the metallic protrusion is integral with a portion of the blind surface. The metallic protrusion includes the metal of the metallic sheet and at least one constituent element from the dielectric layer. The metallic protrusion is then etched to form a metallic interlocking structure that is integral with the portion of the blind surface. The metallic interlocking structure includes discrete metallic fibers, with each metallic fiber having a curved (or curled) geometry. Each metallic fiber has its own unique composition that includes the metal, at least one constituent element of the dielectric layer, or both.