1. Electro Luminescence Inspection
For electro luminescence inspection a constant DC current is applied to the module. This current may be
set by software to values between 1 and 12 A DC. The voltage limit may be set to values between 1 and
60 V DC.
There are some defects, that are detected by EL very easily:
A) High Impedance Module:
All cells of the module appear completely dark, because no electricity passes through the cells. The cause
for this defect may be missing ribbons in one of the strings, a high impedance cell or faulty busing.
Action required: Check for correct position of outer bus bar, missing bus bar connections or missing
ribbons at cells. If error not found, check for high impedance cell using a volt meter and a power supply.
B) Short Circuit Between Cross Connectors:
All cells of one or more strings appear completely dark. This defect may be caused by a short circuit
between two cross connectors, often caused by ribbons that have not been trimmed to its correct length or
by a missing insulation pad at the junction box leads.
Action required: Report to busing personal
Other defects within individual cells are detected with comprehensive software algorithms described
below, if the inspection system is supplied with optional automatic inspection software.
C) Cracks and Micro Cracks: Annotated with red frame around defect areas
Described in this paragraph are cracks, that are visible in the EL image as line structures. This kind of
cracks may be visible on the surface of the cell with the human eye, but often it is buried inside the silicon
of the cell.
Micro cracks mostly do not yet interrupt the electricity flow and therefor are not causing dark, low
efficiency areas on one side of the crack (passive micro crack).
Active micro cracks, which are causing dark, low efficiency areas are described in paragraph Active
Cracks.
EL Training Defects Detectable V1.4