A proper alternative: Ultra sonic bonding for thin film solar cell interconnections

Many different concepts of cell interconnections were aspired during the last years. Within our work, we evaluated an ultrasonic bonding process to interconnect CIGS thin film modules. There are several advantages to shift to an ultrasonic bonding process as thin film back-end interconnection: less material costs (no silver), lead and flux free, simple automation grade and high process control. Furthermore the bonding process is free of wetting or adhesion problems, compared to solder joint formation or conductive adhesive handling. Micro structure analyzes of the connection interface were performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning acoustic microscopy (SAM). Furthermore the characterization of specific contact resistance was evaluated with the transmission line model (TLM) method.