Glass transition temperature as an in situ cure index of electrically conductive adhesives in solar photovoltaic module interconnect assemblies

Abstract Electrically conductive adhesives (ECAs) offer a low-temperature alternative to solder processes for interconnection of photovoltaic cells. The curing conversion of the ECA bond can significantly influence its mechanical performance and electrical conductivity. This study developed a method to measure ECA curing conversion in situ of interconnected solar cell assemblies. First, the relationship between the glass transition temperature ( T g ) and the curing conversion was established using neat ECA specimens that were pre-cured to different degrees. Then, the torsional dynamic mechanical analysis (DMA) was used to measure the T g of the actual ECA bond in the cell interconnect assemblies. Finally, the in situ curing conversion of the ECA bond was estimated through the T g –conversion relationship. Regardless of the extremely high silver filler content (>70 wt%) in a typical ECA and little material available in the actual bondline (∼10 vol%), this method provided high sensitivity and ease of implementation.