Influence of Surface Modification of Alumina Substrates on Wetting -- Bond Strength Relationship in Cu/Al_2O_3 System

摘要

The subject of the work was to study the effect of Ti thin film on alumina substrates on wetting and bond strength properties in Cu/Al_2O_3 couples. Applying the sessile drop method, the wetting behaviour of molten Cu (99.99 percent) on coated and uncoated alumina substrates was studied at 1373 K and 1423 K under a vacuum of 0.2 mPa. The sessile drop samples were used to examine the interface structure and shear strength. The Ti layer of 800 nm thickness improves the wetting properties in Cu/Al_2O_3 and for all couples the temperature increase results in lower values of contact angle. The shear test demonstrates different wetting-bond strength relationship for coated and uncoated couples. Contrary to Cu/Ti/Al_2O_3, the Cu/Al_2O_3 couples showed higher shear strength for higher contact angle, corresponding to lower temperature of wettability test. The structure characterisation of interfaces by means of optical microscopy and electron microscopy equipped with spectrometric system for microanalysis of chemical composition suggests that positive effect of Ti layer on the improvement of both wetting and bond strength properties in Cu/Al_2O_3 system results from a favourable change of structure and chemistry of the interface.