TL;DR
3D height errors are usually caused by a dirty projection lens, a fringe pattern calibration drift, or board warpage exceeding the measurement range. Run the system calibration and check the calibration target.
What you might see
- solder paste height measurements shifted from reference
- component height outside acceptance window on good parts
- 3D measurement noise increasing on flat reference surface
- calibration check failing during daily verification
Likely causes
Fringe projection lens or camera lens contamination reducing phase measurement accuracy
Phase shift calibration drift in the moiré fringe measurement system
Calibration target surface contamination or surface scratch altering reference height
Ambient temperature change shifting the optical bench reference
Required tools
- Koh Young calibration target
- Dry lens tissue
- Height reference standard
Safety first
- The structured light projector emits bright visible and near-IR light. Avoid looking directly into the projection unit when the machine is powered.
Procedure
- 1
Run the daily height calibration check on the calibration target and record the result against the specification.
- 2
If the calibration check fails, clean the fringe projection lens and the camera lens with a dry lens tissue. Do not use solvents.[1]
- 3
Inspect the calibration target surface for scratches or contamination. Replace the calibration target if any scratch is visible.
- 4
Run the full system calibration procedure from the main menu after cleaning.[1]
- 5
Verify the machine ambient temperature is within the operating specification before running calibration. Temperature outside the range will invalidate the result.
- 6
After calibration, run a height check on a reference standard of known thickness and verify the reading matches within tolerance.
- 7
If calibration still fails after cleaning and re-running, contact Koh Young field service for fringe projector alignment.
Sources
Koh Young Koh Young Zenith Alpha / Aurora AOI / X-Ray Inspection general technical documentation, Koh Young
Koh Young AOI system general 3D calibration and maintenance procedures (general)
More guides for Koh Young Koh Young Zenith Alpha / Aurora
How to fix board alignment failure on a Koh Young Zenith Alpha / Aurora AOI
Board alignment failures are typically a dirty fiducial, a worn conveyor stopper, or an incorrect fiducial reference in the job file. Clean the fiducials and verify the job file first.
How to reduce false call rate on a Koh Young Zenith Alpha / Aurora AOI system
Rising false calls are usually a library threshold that needs re-tuning, an illumination change, or a conveyor vibration issue. Audit the top false-call component families first.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.