PV MODULE INSPECTION
– HIGH-VOLTAGE WITHSTAND SAFETY TEST
– SOLDERING DEFECTS
– STATIC ELECTRICITY DISCHARGE
Here is a subset of some interesting findings identified last month:
– High-voltage withstand safety test. November was rainy in China, especially in this particular region. When environment is not sufficiently controlled, outdoors humidity can change indoors conditions. In this one particular workshop, the conditions were such that all modules on the line were systematically failing the high-voltage electric withstand test, a safety test performed at the end of the line. Instead of correcting the problem, and to avoid rejecting all modules, this manufacturer chose to simply bypass the test, creating an unsafe situation for the module buyer.
This issue could have been solved by proper maintenance, proper environmental control, and proper training of the operators.
– Soldering defects. Soldering defects are very common nowadays. In this particular case, like in many others, we identified this issue during pre-shipment inspection. Soldering between the cell ribbon and the bus ribbon was uncontrolled, sometimes performed manually, and in many cases defective. This defect was not spotted during EL inspection either.
This issue could have been solved by soldering machine maintenance, proper operator training, avoidance of manual soldering. It should have been spotted during in-line EL inspection, even before lamination.
– Static electricity discharge. From times to times, like in this particular case, we witness the damage that can cause static electricity discharge to the modules. The most sensitive part to this issue is the diodes located in the junction boxes. Proper SOPs call for static electricity-release bracelets, but these are not always respected in production. In this case, the EL images were showing a third of the module fully inactive at pre-shipment inspection.
It is important to have the right standard operating procedures (SOPs) in place for each process. Such risks are typically assessed during factory audit before production.