Asymmetrical controlled current electroplating

Abstract

Abstract GOLD IS ELECTROPLATED ONTO INTEGRATED CIRCUITS FORMED ON A SLICE OF SILICON WITH SYMMERTRICAL ALTERNATING CURRENT. A UNIQUE CURRENT CONTROL UNIT PROVIDES CONSISTENCY OF THE PLATING CURRENT EVEN THOUGH THE CONCENTRATION OF A PLATING SOLUTION MAY CHANGE DURING THE PLATING OPERATION. THE CURRENT CONTROL UNIT INCLUDES THE NPN TRANSISTOR AND A PNP TRANSISTOR WITH BOTH OUTPUTS OF THE TRANSISTORS CONNECTED IN PARALLEL TO A TERMINAL THAT CONTACTS THE SILICON SILICE DURING PLATING THEREOF. A CONVENTIONAL SOURCE OF SYMMERTRICAL ALTERNATING CURRENT IS CONNECTED TO THE EMITTER O THE TWO TRANSISTORS THROUGH A POTENTIOMETER. THE POTENTIOMETER IS ADJUSTED TO PROVIDE A DESIRED RATIO BETWEEN THE CURRENT CARRIED THROUGH THE NPN TRANSISTOR AND THE CURRENT CARRIED HROUGH THE PNP TRANSSISTOR. A SEPARATE MEANS OF BIASING IS PROVIDED SO THAT THE CURRENT THROUGH THE TRANSISTORS CAN BE ACCURATELY CONTROLLED. THE PNP TRANSISTOR IS BIASED TO CONDUCT A POSITIVE PORTION OF THE WAVE SHAPE AND THE NPN TRANSISTOR IS BIASED TO CONDUCT A NEGATIVE PORTON OF THE WAVE HAPE. THUS, BY ESTABLISHING THE DESIRED RATIO WITH THEPOTENTIOMETER, A CONTROLLED DEGREE OF ASYMMETRY CAN BE ACHIEVED. BY CONTROLLING THE LEVEL OF BIASING, A CONTROLLED MAGNITUDE OF CURRENT CAN ALSO BE PROVIDED TO THE PLATING OPERATION.

Inventors

• 👤 R Miller

Bibliographic Details