Fabrication Constraint
Laser drilling parameters determine the hole bottom geometry relative to the target land buried beneath a dielectric layer. Microvia depth control manages the ablation energy and pulse frequency to ensure the dielectric removes cleanly without compromising the underlying copper surface. Successful execution prevents pad damage or incomplete penetration of the buildup material.
Process Variation
Thermal properties of the resin matrix shift the ablation rate as the drill progresses through alternating layers of glass fibre and epoxy. Manufacturers compensate for these fluctuations by adjusting the focus offset or the number of pulses applied to each site. Feedback loops within the laser system monitor signal changes from the surface to identify the exact moment the drill breaks through the dielectric interface.
Stability of this penetration ensures a consistent connection geometry for subsequent plating steps.
Acceptance Boundary
Inspection protocols rely on cross sectional analysis to verify that the hole depth remains within the tolerances specified by the original design file. Measurements confirm the absence of excessive copper gouging or residual dielectric film at the base of the via. Standards governing these features prioritize the integrity of the metallic interface between the laser drilled hole and the landing pad to maintain reliable signal transmission.
Any deviation beyond established limits indicates a failure of the drilling cycle to maintain the required dielectric thickness.
