STS is your “eyes and ears” in the manufacturing lines!

Here are two examples of some non-conformities identified in our recent quality inspections during manufacturing of PV modules:

– “Oval Marks” on the PV Cells

Oval marks happen during the process of cell manufacturing, where a layer of aluminum oxide is deposited on front side of the wafer via ALD (Atomic Layer Deposition).

To avoid unsuitable deposition of aluminum oxide on the rear side of the wafer, manufacturers protect the rear side using either horizontal carriers, or vertical carriers with two wafers sitting back-to-back.

In the case of vertical carriers, the rear side of the wafer can still be partially exposed to deposition because of wafer wrapping, airflow disturbances or mispositioned carrier holder. This results in uneven deposition of aluminum oxide on the rear side of the wafer, leading to the visible “oval marks” on the finished cell. However, within certain limits, the unintended rear-side deposition is not detrimental to the cell performance and no intervention is needed.

– Bubbles in the Frame Sealant

This issue occurs during framing of the PV modules, and is due to the unintended introduction of air when gluing the frame to the module glass.

During the replacement of the sealant barrel, glue remnants in the tube are not fully cleared, and the glue gun head is positioned too high. Consequently, air leaks in the tube and the sealant application is inconsistent, leading to bubbles in the modules.

The defective modules are rejected and immediate corrective actions to prevent recurrence by the factory include the implementation of standardized Operational Procedure Lists (OPLs) for sealant barrel replacement, adjustment of the glue gun head to a standardized height, and enhanced inspections at the four corners of modules during framing.

Conducting quality control activities before shipping is crucial for identifying non-conformities and preventing performance issues in the field.