OK International has launched a new soldering system for PV tabbing and bussing applications proven to reduce micro cracking. The PS900 with specially designed hoof tip geometry optimizes the power delivered to the solder joint while it’s temperature-sensitive heater ensures low temperature soldering thus minimizing thermally induced stresses on cell surfaces.
The PS 900 incorporates OK International’s patented SmartHeat Technology that will produce and maintain a specific, self-regulated temperature with a heater that requires no calibration and responds directly to thermal loads.
There are two suitable solder alloys utilized for solar cell soldering application; Sn96Ag4 with a melting point of 221’C, or bismuth containing Bi58Sn42 with a melting point of 138’C. Proper soldering will result in an intermetallic layer that is 1- 2m, which demands precise time and temperature control during the solder joint formation.
Micro cracking of delicate solar cell substrates is a common defect that can occur during PV tabbing and bussing soldering processes. Reducing the soldering temperature to a minimum prevents the cells being subjected to mechanical or thermal stresses. During the soldering operation, differential thermal expansion of the copper and the silicon elements can occur at temperatures greater than 300’C. This differential can result in the formation of micro-cracks that may not be detected during the manufacturing process and result in reduced field lifespan.
The OK International SmartHeat PS-900 soldering system with specially designed STV-DRH40 hoof tip geometry optimizes the power delivered to the solder joint, thus providing high performance efficiency with increased tip life. It’s temperature-sensitive T heater series ensures low temperature soldering and thus minimizes thermally induced stresses on the surface of the solar cells.
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