Interference Metrology
Non-contact surface topography metrology uses light wave interference and confocal scanning to generate three-dimensional surface height maps. Light emitted from an internal source splits into a reference beam and a sample beam that reflects off the target substrate. The resulting optical interference patterns create quantitative surface height profiles without contacting the sample.
Applying optical profilometry to circuit boards enables rapid inspection of surface finishes, copper foil roughness, and solder paste deposit volumes. The measurement range terminates when surface feature heights exceed the vertical coherence length or objective working distance of the instrument.
Topography Quantification
Surface roughness parameters calculated from non-contact optical scans correlate with solder joint wetting and copper foil adhesion performance. Printed circuit board manufacturing requires precise copper foil profile measurements to balance high-frequency conductor loss against mechanical peel strength. Utilizing optical profilometry provides root-mean-square roughness values and surface area ratios across treated copper surfaces.
In surface mount assembly lines, three-dimensional solder paste inspection systems employ structured light profilometry to measure deposit heights and volumes. Solder paste deposits that fall below target volume thresholds are detected before surface mount component placement, preventing open solder joints.
Quality Verification
Profilometer inspection routines generate high-resolution topographical maps that highlight coin-flatness defects on ball grid array landing pads. Non-destructive optical measurements verify that ENIG surface finishes display uniform pad coplanarity without destructive physical contact. Quality assurance laboratories use these surface maps to inspect etching undercut profiles and blind microvia dimple depths.
Trace roughness values obtained from optical scans serve as direct inputs for electromagnetic field simulation tools.
