Hydrodynamically modulated hull cell

Abstract

Electrodeposition in surface finishing as well as in electroforming can be performed in a broad range of hydrodynamic conditions. In some instances, such as barrel plating, the liquid is barely moving relative to the work piece, while in jet plating the solution moves up to several meters per second relative to the piece to be plated. In such a wide range of hydrodynamic conditions, the selection of appropriate quality control (QC) methods for each particular operation is very critical. The QC method has to resemble the manufacturing operation in terms of the hydrodynamic conditions otherwise the quality control and the functional test for the bath performance have no meaning. Available Hull Cell systems have a limited capability in varying the liquid velocity. At best a relative velocity of up to 20 or perhaps 30 cm/sec can be achieved with uneven distribution. The invention provides, in electroplating QC methods for manufacturing, better similarity and relevance between a Hull Cell QC test and a particular plating operation. The invention is a simple and yet functional instrument which can be used to identify the performance of the plating bath prior to manufacturing operation under similar hydrodynamic conditions. The instrument is a rotating cylinder with a flexible Cu test panel attached to its surface. Like a Hull Cell, a range of current density can be simultaneously applied. Unlike a Hull Cell, the rotating speed of the cylinder and hence the solution agitation is practically unlimited. The operator can identify the operating window for the particular process and apply them to the production line. The instrument has also demonstrated usefulness in developing proprietary electroplating chemistries.