Mfg. unipolar or bipolar pulsed current for plating esp. of circuit boards at high current

摘要

A process is disclosed for generating short, cyclically repeated unipolar or bipolar electroplating pulse-shaped currents IG, IE, as well as an electroplating circuitry with which such pulse-shaped currents IG, IE can be generated. Such electroplating processes are known as pulse-plating processes. The secondary winding (6) of a current transformer (1) is connected in series to the electroplating direct current circuit (5) which consists of a bath direct current source (2) and a bath resistor (RB) formed by an electroplating cell (4). The primary winding (7) of the transformer has a larger number of turns than the secondary winding. The primary winding is driven with high-voltage and relatively low-current pulses. The high pulsed current at the secondary side temporarily compensates in a pulsed manner the electroplating direct current. This compensation may be a multiple of the electroplating current, producing high amplitude demetallisation pulses. The capacitor (10) leads the compensation current by charge and discharge. Thanks to the invention, known electronic heavy current isolating switches which are uneconomical in operation because of high current conductivity losses may be dispensed with for the pulse plating.