The screening system may consist of a conveyor belt that carries numerous wafers and exposes them in succession to an optical source, such as a tungsten-halogen lamp. A wafer’s narrow, uneven illumination from the optical source causes a pre-determined thermal stress in a wafer such that wafers compromised by micro-cracks may break and then be removed from the production stream. The energy generated by the optical source is used to induce the maximum thermal stress that a wafer would experience during manufacturing. If a wafer survives this stress test, then it likely would survive the cell fabrication process without breakage.
Traditional wafer-screening methods like three-point testing may suffer from relatively complex and slow implementation schemes and from inaccurate results gained from tests performed over local areas of the wafers. As an alternative to the application of mechanical stress, wafer cracks may be analyzed with thermal imaging. However, small cracks can be difficult to detect with the imaging method. Moreover, because thermal imaging provides sufficiently indirect data about the wafers’ propensity to break from detected micro-cracks, selection of uncompromised wafers can be difficult with this crack-detection method. The disclosed screening method and apparatus provide an efficient and easy way to detect and remove compromised wafers from the production stream before unnecessary labor, materials, and energy are invested.
To learn more about Screening of Silicon Wafers Used in Photovoltaics, please contact Bill Hadley at:
Patent: US 8,006,566 B2
Applications and Industries
- Solar cell manufacturing
- Solar module manufacturing
- Wafer manufacturing
- Solar equipment manufacturing
- A superior screening method and apparatus to both detect and remove compromised solar-cell wafers from the production stream
- Screening of compromised wafers before unnecessary labor, materials, and energy are invested
- Enhanced micro-crack detection efficiency and reliability over mechanical and imaging detection methods.