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72 SMT007 MAGAZINE I AUGUST 2021 I-V Curve Measurement Modified Sinton Instrument FMT-0038 was used to measure electrical properties of mini panels. I-V curve was derived from which effi- ciency, power output, fill factor, etc., parame- ters were obtained. Results and Discussion e Multi-Busbar (MBB) technology appears to be another novel cell interconnec- tion technology to increase the module power. Figure 1 shows 12 BB and silver pad design. e interconnection was processed with the help of the Lead Xi machine. e intercon- nected cells were laminated with a glass and EVA. We identified four factors that affect the solder joints. ey are: 1. Cell metallization 2. Solder wire 3. Flux 4. Process condition We will discuss on each in detail in ensuing sections. Cell Metallization MBB cells were analyzed closely for surface smoothness and topology using higher magni- fied microscope (Figure 1). Screen printing metallization is cost-com- petitive and robust technology used in the production. e technology has attracted con- siderable attention due to significant improve- ment in printing medium and simplicity of the process. e new generation solder pastes provide better aspect ratio (the ratio of line height to line width) which helps in improving the current-carrying capacity of the contacts, as the shadow loss and the series resistance decreases. However, if the right screen param- eters such as mesh count, wire dimension, and emulsion thickness are not chosen, the final outcome suffers from issues like adhesion, glass on the surface, printing smoothness, etc., of the metallization surface will impact the sol- dering adhesion. dardized specimens were used along with a set of specified test variables. In this test, fluxed standardized copper specimens are dipped into the molten bath of alloy (Sn-Pb) while time and force required for the solder to wet the surface was measured and plotted. Raman Spectroscopy Raman spectrum is a distinct chemical fin- gerprint for a particular molecule or mate- rial that can be used to very quickly identify the material or distinguish it from others. e LabRAM HR Evolution Raman microscope (Horiba Scientific) with ultra-fast confocal imaging and high spectral and spatial resolu- tions was used to identify any oxides present on the wire surface. X-Ray Analysis e phoenix microme|x is a 180 kV micro- focus X-ray inspection system used for real time inspection of solder joints and voiding analysis. Reliability Reliability of modules was investigated by performing thermal cycling (TC) and damp heat (DH) testing as per IEC61215. In this pro- cess, modules were subject to climatic testing with defined temperatures and humidity con- ditions while the change in module perfor- mance aer testing was the key parameter to be evaluated. Conditions for damp heat were: • Test temperature: 85°C ±2°C • Relative humidity: 85% ±5% • Test duration: 1000 hours • Conditions for thermocycling were: • Test temperature: 40°C to 90°C [30 min minimum dwell times, <100°C/min. transition] for 200 cycles. An electroluminescence system was used to inspect the modules for any kind of cracks and other defects. Electrical performance was determined by I-V curve measurement.