Investigation of the Adhesion of Electroless Copper to Glass Substrates

Abstract

This paper reports the effect of a Pd/Sn catalyst treatment process on the adhesion of electroless copper deposited onto a glass substrate. Adhesion of the copper varied with catalyst treatment time: short or extended catalyst immersion times led to lower adhesion. In this work silanisation of the glass surface with (3-aminopropyl)-trimethoxysilane was used to provide a layer of functional molecules to assist the adhesion of the Pd/Sn catalyst. Surface analysis of the catalyzed glass was carried out by X-ray Photoelectron Spectroscopy (XPS) and together with Time-of-Flight Secondary Ion Mass Spectrometry, showed that the Pd/Sn structures changed with increasing immersion time in the catalyst bath. The Pd XPS core level peaks indicated that Pd(0) became more significant in the catalyst layer than Pd(II) with increasing immersion time. Tape peel testing was used to assess the adhesion of the coatings: thin layers adhered well to the glass, but for layers thicker than 160 nm tape tests removed large areas. The failure surfaces of copper layers peeled off the glass were also examined by XPS which indicated that the failure occurred between the copper and catalyst.