Phase Resolved near Field Dipole Reconstruction for Multilayer Board Far Field Escape Prediction
Phase-resolved near-field dipole reconstruction predicts far-field escape emissions within 2 dB, eliminating un-phased scan errors before SAC testing.
Scalar Dual Plane Scan
Measurement Methodology
Optical profilometry utilizes a scalar dual plane scan to map topographic surface deviations across multi-layer printed circuit boards. This diagnostic operation captures depth data from both the top solder mask and the underlying copper foil to produce a singular topographic profile. Automated optical inspection systems deploy this technique during post-reflow manufacturing stages to identify volumetric solder joint inconsistencies.
By isolating disparate planes within a single focal pass, the routine avoids potential parallax errors that plague standard singular image analysis. Consistent vertical alignment between planes relies upon high-speed Z-axis stepping motors that synchronize with camera sensors to maintain sharp focus across varying topography.
Calibration Requirement
Precise mechanical registration between the dual focal planes dictates the accuracy of volumetric calculations for surface mounted components. Optical systems achieve this alignment through reference markers etched into the laminate surface which provide fixed coordinates for the software algorithm. These markers allow the scalar dual plane scan to correct for board warpage or thermal expansion during the inspection cycle.
Operators must verify that the distance between the two planes remains constant across the entire field of view to ensure the validity of computed height metrics. Variations in board flatness cause deviations in the perceived height of solder deposits if the software fails to compensate for substrate displacement.
Assembly Application
Solder paste inspection systems integrate this method to quantify the volume of paste deposited on pads prior to component placement. High-density interconnect designs demand this level of resolution because standard two-dimensional imaging provides insufficient data to predict joint formation under high-speed assembly conditions. The ability to distinguish the PCB substrate from the metallic contact pads allows for accurate measurement of stencil registration accuracy.
This analytical depth remains the primary defense against open circuits caused by inadequate solder volume on fine-pitch components.