Fine Line through Hole Copper Filling in VCP for Next Generation Packaging
Authors: Olivier Mann, Ph.D., Henning Hübner, Angelo Ferro Company: Atotech Deutschland GmbH Date Published: 9/17/2017
Abstract: This paper presents the complete through hole filling for cores using a Cu electroplating process for IC Package production, especially for FC-BGA and FC-CSP. There are two main objectives for this application: technological aspects and productivity. The only state-of-the-art through hole filling in panel plating providing inclusion-free performance is available for horizontal conveyorised systems with pulse plating since 2005 and already used in full mass production. When it comes to pattern through hole filling the process presented hereafter has been designed for vertical continuous plating (VCP) equipment. In order to meet the technological requirements for next generation packaging, parameters such as pattern plating with excellent within-unit distribution and inclusion-less filling performance are of utmost importance. From a productivity standpoint high current densities and reduced plated thickness are the preferred two ways to follow. This paper focusses on technological aspects and on difficulties to fill through holes of various dimensions and sizes that exist in the market. The fluctuating drilling tolerances/ qualities (protruding glass fibres, laser drilling asymmetry) give indications how to minimise the inclusion rate. In detail the influence of electrolyte agitation, current density, inorganic and organic concentrations on the filling performance are described and discussed. The result of our investigations is a process with improved TH filling capability at low void occurrence and excellent within-unit distribution. The new process has shown improved capability to fill though holes in cores of up to 200 µm, while further investigation continues.
Through hole filling, VCP, horizontal systems, IC packaging.