The evolution of Pd/Sn catalytic surfaces in electroless copper deposition

This paper describes the different catalytic surfaces of Pd/Sn formed before electroless copper deposition onto a glass substrate. In this study, silanization of the glass surfaces with (3-aminopropyl) trimethoxysilane was used to provide a surface-coupled layer of functional molecules to assist in the adsorption of Pd/Sn catalyst and the subsequent copper deposition. The composition and microstructure of the modified glass surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry. These showed that catalytic Pd/Sn structures on the surface changed with increasing immersion time in the catalyst bath. The core-level XPS spectrum of Pd indicated that metallic Pd(0) became more significant in the catalyst layer than Pd(II) with the increasing immersion time. A model of the adsorption process is proposed to explain these changes. It was observed that too high a quantity of Pd(0) does not always improve the adhesion of the Cu deposits in the electroless process.