Buildup Insulation
A thermosetting resin sheet applied to ultra-fine line printed circuit boards provides the insulating medium between successive microvia layers. Epoxy-based abf film enables the fabrication of high-density interconnect structures by allowing sub-ten-micron trace routing on successive build-up layers. The material maintains uniform thickness across the entire panel surface.
This consistency prevents impedance variation and signal distortion in high-frequency semiconductor packages.
Dielectric Lamination
Dry vacuum deposition applies the dielectric sheet onto a prepared core board under high pressure and temperature to ensure complete fill of blind vias and blind trenches. After the lamination step, a thermal bake cures the resin to its final mechanical strength. This curing reaction creates a stable platform for subsequent chemical processing and copper deposition.
The cured film exhibits a low coefficient of thermal expansion which matches the adjacent copper lines to prevent delamination during thermal cycling. Inadequate vacuum during this step results in trapped air pockets that cause localized resin starvation and micro-delamination during reflow soldering. Proper temperature profiles are critical to allow the resin to flow adequately before cross-linking commences.
Laser Metallization
Laser drilling creates microvias directly through the cured resin layer to expose the underlying copper pads for electrical connection. Desmear chemicals then roughen the laser-drilled hole and the resin surface to ensure strong adhesion of the electroless copper layer. This chemical roughing establishes the anchoring sites for the subsequent electrolytic plating step.
Consistent adhesion prevents trace lifting under high current densities and prolonged thermal stress.
