Geometric Calibration Targets for Surface Mount X-Ray Inspection
Geometric calibration targets establish spatial scale and correct optical distortion, guaranteeing valid void and dimensional measurements in SMT X-ray inspection.
Synthetic Quartz Target
Substrate Disk
Precision calibration plates used in high-resolution optical and X-ray metrology require substrates with extremely low thermal expansion. A synthetic quartz target is a disk or rectangular plate made from high-purity silica glass and patterned with sub-micron metallic features. This target is used as a reference standard to calibrate the coordinate systems of automated board inspection systems.
The high dimensional stability of this material ensures that the pattern remains consistent under varying temperature conditions.
Thermal Stability
Thermal expansion can introduce significant errors in high-magnification automated inspection systems. When a synthetic quartz target is used, its coefficient of thermal expansion of about zero point five parts per million per degree Celsius ensures that the distance between patterns does not change with temperature. This property is crucial for calibrating three-dimensional solder paste inspection systems where sub-micron accuracy is required.
System software relies on the stability of the target to calculate and correct for optical distortion and lens aberrations.
Calibration Accuracy
Regular calibration runs are performed at the start of each production shift to maintain the measurement accuracy of the inspection systems. This target is placed on the system stage and scanned to compare the measured positions of the patterns with their certified coordinates. Because of the high purity and uniformity of the synthetic quartz target, it provides a stable and traceable reference that satisfies international metrology standards.
These targets are housed in protective cases and handled with care to prevent surface scratches that could interfere with the calibration software. This routine check ensures that the automated inspection equipment can reliably distinguish between acceptable solder fillets and nonconforming defects.