DEVICE FOR THE GENERATION OF A TEMPERATURE-CONTROLLED THERMAL BARRIER TO THE MAGNETIC INDUCTION POLES OF A WELDING HEAD

摘要

An induction welding head for welding multilayer printed circuits (PCB) comprises a ferrite induction device with polar U-shaped expansions in sliding contact against two movable induction electrodes of elongated form. The induction electrodes are aligned along the same translation axis and are controlled by pneumatic actuators in order to be positioned against the multilayer exerting a pressure on the contact surface. Each opposed ends of the induction electrodes has a thermal barrier constituted by a small Teflon plate with a 70-microns copper layer sticked at one face, and the other face glued by a bi-adhesive tape to the polar face of the induction electrode. The copper layer extends for a part of the end surface of the induction electrode. A ribbon thermocouple is brought in contact with the copper layer of the thermal barrier maintained against it by a small Teflon lid. The thermocouple sends a measurement signal of the temperature reached by the thermal barrier to a controller device of the power circuit feeding the induction winding with 500 V square-wave at 24 kHz (fig. 3).