Plating Requirement
A metallic deposition process ensures that holes connecting printed circuit layers contain enough conductive material to withstand thermal expansion without cracking. Microvia fill addresses the high aspect ratio challenges of high density interconnect technology by replacing air voids with solid copper or conductive paste. This procedure prevents the entrapment of chemical solutions during secondary etching or plating operations.
Mechanical strength during reflow depends entirely on the complete encapsulation of the conductive path within the small laser drilled opening.
Process Stability
Uniformity across the surface determines the success of the chemical deposition or screening operation. Microvia fill results rely on the viscosity of the dielectric material or the plating bath additives to force metal into tight geometries. Any deviation in the current density during electroplating produces non-uniformity that impacts the reliability of the interconnect.
Voids inside these structures create thermal stress points during assembly cycles because the copper coefficient of thermal expansion differs from the surrounding resin.
Inspection Boundary
Optical and cross-section analysis verifies that the copper deposition creates a solid connection between the land and the internal layers. Microvia fill performance remains acceptable when no separation exists between the plated material and the sidewall of the hole. Imaging techniques detect internal voids that remain hidden under the top layer of copper.
Strict adherence to this filling protocol remains the primary defense against internal barrel fatigue in high reliability electronics.
