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

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

– Bubbles at the Edges and around the Barcode Labels Due to EVA and Lamination Issues

Bubbles appear at the edges and around the barcode labels on PV modules. Such bubbles can lead to delamination (and subsequent failure) of the PV modules in the field.

The edge bubbles were due to inadequate tracking and adjustment after replacing the EVA roll, leading to bubble formation. The bubbles around the barcode were caused due to the barcode increased thickness, which is affecting the lamination process.

To address these issues, the factory has implemented measures including training personnel to monitor EVA laying more closely; optimizing lamination parameters to improve pressure and temperature control; and increasing the EVA pad width to ensure proper placement.

– Cell Soldering Defects

1. Vertical Soldering Defects
Vertical soldering defects cause shadows to appear between the PAD points after lamination. They are due to minor variations in current density at solder points, which become visible only after the POE film fills in and lamination is complete.

2. Large-area Soldering Defects
Large-area soldering defects are caused by temperature loss in the lamp soldering box during machine downtime. When the machine restarts, this leads to poor tinning of solder strips and to ineffective bonding with the cell’s silver paste.

To address these issues, the factory has implemented several measures:

For vertical soldering defects, they have optimized soldering power and time, adjusted the lamp box height, repositioned lamp tubes to improve thermal radiation, and refined fixture placement to enhance alignment.

For large-area defects, they have extended the re-start soldering time, standardized lamp box height, and optimized the delay in lamp box elevation after shutdown to reduce heat loss.

These measures aim to improve soldering quality and prevent recurrence of these defects.

– POE Melting Issues and Appearance Defects

We identified a non-conformity in the PV modules where the POE was not properly melted around the glass edges.

This is due to three reasons. Firstly, because of utilizing leftover POE pieces which had been left unused for too long, which leads to dampness; Secondly, due to an inadequate cross-linking caused by issues with lamination parameters; And finally, because of uneven heating caused by insufficient maintenance of the laminator.

To address these problems, the factory has implemented measures including using POE within 24 hours of cutting, updating lamination parameters, and ensuring regular maintenance and inspection of the laminator by a dedicated team.

– Inconsistent Cell Efficiency Due to Improper Distribution on Production Line

PV cells on the production line had inconsistent efficiency levels. This issue arose because cells were not distributed according to the single-line, single-machine principle, leading to unclassified cells being used interchangeably.

To address this issue, the factory has implemented measures including appointing personnel to ensure consistent cell distribution, enforcing feedback mechanisms to align incoming materials, and labeling each machine with up-to-date material information to prevent errors.

– Expired Modules Due to Improper Return Processing

We conducted an inspection project where we discovered a backlog of modules sent back for repairs due to string soldering defects. Typically, defective modules should be repaired within 12 hours of return (in consideration of oxidation risk). However, due to improper handling and failure to follow the first-in-first-out principle by the personnel, this backlog had surpassed the repair time limit, and the modules needed to be discarded instead.

In response, the factory has implemented several measures: improving equipment processes to reduce defects in string soldering, increasing manpower and skills for string repair to avoid backlog, and appointing a supervisor to oversee the return process and track repair status.