Automatic quality control during electric resistance welding - used e.g. to avoid welding defects when making electric connections to solar cells

摘要

Welding defects are prevented by measuring the welding current (I) at a high repetition rate during a welding pulse, and feeding the values (I) into a digital memory. At the end of the pulse, the current integrals are calculated for the total time (Itt) and for two or more equal fractions (Ift) of the total time. When the ratio of the fractions (Ift) deviates from a prescribed value, the welding process is stopped while the welding electrodes are polished, wet cleaned, and dried. In the pref. welding appts., the current generator includes a controller fed with the actual voltage (UUist) and a desired reference voltage (Usoll), the latter being supplied from a digital processor fed with values (I) from an analogue/digital converter. Used e.g. in the microwelding of electric connections on semiconductor elements used in mfg. solar cells.