Dimple Depth

Geometric Tolerance

Mechanical stability within the high-density interconnect stack relies on the consistency of this measurement across all laser-ablated sites on a panel. A scan across the surface identifies variations in energy density where the laser source pulse width changes or the beam intensity drops during long production runs. Data gathered from this check prevents the thinning of conductive layers near the periphery of the hole which often happens when the laser drills too deeply into the glass-reinforced epoxy.

High vertical deviation creates a localized stress concentration zone that fails during reflow solder testing. Maintaining strict limits allows for uniform current distribution throughout the finished circuit path during high frequency signal transmission.

Assembly Calibration

Automated optical inspection equipment detects these surface anomalies after the outer layer etching process but prior to the solder mask application. The presence of excessive dimple depth triggers a reject signal because the geometry of the landing pad or the registration hole affects the alignment of surface mount components during the pick and place operation. Operators set the pass criteria based on the ability of the plating bath chemistry to fill the cavity without leaving a depression that interferes with stencil printing.

Excess volume in these depressions causes solder paste accumulation that bridges adjacent pads or creates solder balls during the reflow process. Uniform surface topography ensures reliable wetting and prevents thermal fatigue in the joints during board operation in harsh environments.