Investigation of Surface Contaminants on Copper Components for Quantum Computing Applications and Effective Methods for Contaminants Removal Prior to Gold Plating

Abstract

This thesis examined cleaning techniques for preparing copper components for gold plating, particularly for applications in quantum computing, where copper’s high thermal conductivity is critical at low temperatures. The research aimed to identify the most effective cleaning method and investigate various residues left on copper surfaces. All Method A, Method B and custom cleaning methods were evaluated, revealing that the choice of method significantly impacts surface cleanliness.

The study found that Method B, consisting of ultrasonic cleaning in an Alconox solution followed by a citric acid immersion, was an effective cleaning process for copper surfaces. Its performance could be improved by adjusting the citric acid temperature and concentration. Sandpaper use may not be necessary unless there are visible surface irregularities; if used, fine-grit sandpaper (P 1000–2000) is recommended over coarser options to avoid deep surface damage. However, there were suspicions of remaining residues, which may originate from the Alconox solution, rinse water, or the compressed air used. For more precise residue analysis in future studies, sensitive methods such as XPS, AES, or SIMS spectroscopy are recommended. This thesis provided valuable insights into scientific writing and practical laboratory skills.