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Characterization and improvement of copper / glass adhesion

By Baofeng He

Abstract

A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.The development of glass substrates for use as an alternative to printed circuit boards (PCBs)\ud attracts significant industrial attention, because of the potential for low cost but high\ud performance interconnects and optical connection. Electroless plating is currently used to\ud deposit conductive tracks on glass substrates and the quality of copper / glass adhesion is a\ud key functional issue. Without adequate adhesive strength the copper plating will prematurely\ud fail. Existing studies have covered the relationship between surface roughness and adhesion\ud performance, but few of them have considered the detail of surface topography in any depth.\ud This research is specifically considering the mechanical contribution of the glass surface\ud texture to the copper / glass adhesive bond, and attempting to isolate new ISO 25178 areal\ud surface texture parameters that can describe these surfaces.\ud Excimer laser machining has been developed and used to create a range of micro pattern\ud structured surfaces on CMG glass substrates. Excimer mask dimensions and laser operation\ud parameters have been varied and optimized according to surface topography and adhesion\ud performance of the samples. Non-contact surface measurement equipment (Zygo NewView\ud 5000 coherence scanning interferometry) has been utilized to measure and parameterize (ISO\ud 25178) the surface texture of the glass substrates before electroless copper metallization.\ud Copper adhesion quality has been tested using quantitative scratch testing techniques,\ud providing an identification of the critical load of failure for different plated substrates. This\ud research is establishing the statistical quality of correlation between the critical load values\ud and the associated areal parameters.\ud In this thesis, the optimal laser processing parameter settings for CMG glass substrate\ud machining and the topographic images of structured surfaces for achieving strong copper /\ud glass plating adhesion are identified. The experimental relationships between critical load and\ud areal surface parameters, as well as the discussions of a theoretical approach are presented. It\ud is more significant to consider Sq, Sdq, Sdr, Sxp, Vv, Vmc and Vvc to describe glass substrate\ud surface topography and the recommended data value ranges for each parameter have been\ud identified to predict copper / plating adhesion performance

Topics: Glass, Surface texture, Areal parameters, Adhesion, Laser machining
Publisher: © Baofeng He
Year: 2012
OAI identifier: oai:dspace.lboro.ac.uk:2134/10056

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