Edge and corner geometry check of solar wafers
The wafer is imaged from above over a backlit opening between two narrow belts. Its outer contour is compared with the nominal geometry; a wafer with a chipped edge or corner is removed by a gantry arm with a vacuum gripper.
Contour deviation and defect location are sent to line control. A nonconforming wafer is moved to a separate tray by the gantry arm; the nominal and measured contours are overlaid on the operator display.
- 01 Infeed
- 02 Silhouette
- 03 Acquire
- 04 Compare
- 05 Sort
The wafer arrives at the backlight window on narrow belts.
- Contour deviation
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- Missing corner area
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Scenes are illustrative simulations; they are not customer references or performance guarantees.
Need
The edge of a thin wafer is fragile. Under top lighting the contrast between the grey wafer and the carrier background stays low, so small edge and corner chips cannot be resolved. Shift and rotation of the wafer on the belts also affect contour measurement.
Solution approach
Narrow transport belts leave the measurement area open; a panel below turns the wafer into a dark silhouette, so the outer contour is extracted independently of surface colour. The image from the perpendicular camera is calibrated to bring the contour into measurement units and aligned to the wafer's own edges; edge and corner deviations are measured against the nominal geometry.
Process steps
- 01
Infeed
The wafer arrives at the backlight window on narrow belts.
- 02
Silhouette
The backlight turns the wafer into a dark silhouette.
- 03
Acquire
The overhead camera captures the outer contour.
- 04
Compare
The contour is aligned to the nominal geometry and the deviation is measured.
- 05
Sort
A wafer with a chipped corner is moved to a separate tray.
Related applications
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