An Optical Set-Up For Inspecting Edge Chipping Defects Of Dws Solar Wafer
Diamond-Wire Sawn (DWS) technique in Photovoltaic (PV) wafer slicing has the capability to slice out thinner wafers at a faster speed and lower kerf lost. However, thinner wafers will cause higher breakage rate. In-line inspection of defects such as wafer’s edge chipping has become more important...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://eprints.usm.my/50617/1/An%20Optical%20Set-Up%20For%20Inspecting%20Edge%20Chipping%20Defects%20Of%20Dws%20Solar%20Wafer.pdf |
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| Summary: | Diamond-Wire Sawn (DWS) technique in Photovoltaic (PV) wafer slicing has the
capability to slice out thinner wafers at a faster speed and lower kerf lost. However,
thinner wafers will cause higher breakage rate. In-line inspection of defects such as
wafer’s edge chipping has become more important. This research focuses on the
optical set-up for silicon solar wafer’s edge chipping inspection system, resulting in
the proposal of a novel set-up. It was discovered that the optimum camera set-up is at
45° and this angular view achieved surface visibility above 70% for all the three
surfaces of a wafer’s edge, i.e., the top, side, and bottom surfaces. The use of dome
light in the set-up was proven effective in generating best image quality for DWS
surface with SNR of 14.4dB. Also, the back-lit illumination resulted in the best
contrast averaging at 85.0%. The proposed set-up is applicable to run in-line on
353.7 mm/s of conveyor speed, which is equivalent to 4200 UPH production with the
wafers pitch of 300 mm per unit. It achieved 100% detection for the three major
types of chippings which are (i) the non-through, (ii) the through, and (iii) the side
chipping, for chipping samples with size between 33 μm to 780 μm. The correctness
of defect region segmentation scores 68.1% with false negative about 31.9% while
the false positive maintained at 2.3%. |
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