Laser Microvia

Laser Ablation

High-density circuit boards use focused laser energy to drill extremely small blind vias through thin dielectric layers. A laser microvia typically has a diameter below one hundred and fifty micrometers, connecting the outer circuit layer to the immediate inner layer. This drilling technique allows for much higher routing density than is possible with mechanical drills.

Blind Via

Carbon dioxide or ultraviolet lasers vaporize the epoxy resin and stop when they encounter the copper layer below. This selective ablation relies on the higher melting point of copper, which acts as a drilling shield. The resulting cone-shaped hole is then chemically cleaned and electroplated to establish a solid electrical and thermal connection between the layers.

Reliability Limit

Industry standards limit the aspect ratio of these blind vias to prevent plating voids. If the depth of the hole exceeds its diameter, the electroplating chemistry cannot flow properly, resulting in a thin or incomplete copper barrel. Consequently, microvias are generally stacked or staggered across multiple sequential layers to build deep interconnects rather than drilled through multiple cores at once.

This stacking requires precise alignment, as even a small offset between stacked microvias will induce mechanical stress that cracks the copper plating during thermal cycles.