Smartheat improves PV tabbing and bussing results

The proprietary Smartheat Technology produces and maintains a specific, self-regulated temperature with a heater that requires no calibration and responds directly to thermal loads.

The technology consists of a high-frequency alternating-current (AC) power supply and a self-regulating heating element.

The heater utilises the electrical and metallurgical characteristics of two different metals: copper, which is a material with high electrical conductivity, and a magnetic material with high resistivity.

Hoa Nguyen, vice-president of technology at OK, said: 'The micro-cracking of delicate solar-cell substrates is a common defect that can occur during PV tabbing and bussing soldering processes.

'The soldering temperature must be reduced to a minimum so that the solar cells will not be subjected to mechanical or thermal stresses from the soldering process,' added Nguyen.

During the soldering operation, the differential thermal expansion of the copper and the silicon elements can occur at temperatures greater than 300C.

This differential can result in the formation of micro-cracks that may not be detected during the manufacturing process and result in a reduced field lifespan.

The need for precise time and temperature control is made additionally critical by the precise inter-metallic layer requirement of 1-2um that must be created during the solder-joint formation.

The OK Smartheat PS-900 soldering system with a specially designed STV-DRH440A hoof tip geometry optimises the power delivered to the solder joint, thus providing efficiency with increased tip life.

Its temperature-sensitive 'T' heater series ensures low-temperature soldering and thus minimises thermally induced stresses on the surface of the solar cells.