Etude de la microstructuration du verre par étincelage assisté par attaque chimique: une approche électrochimique
We are surrounded by glass! This material has been greatly used for thousand years. More than 2000 years ago in ancient Egypt glass was used to manufacture bottles of perfume. So its first uses were primarily related to decoration and jewellery. The researchers left its decorative use to introduce it to new technologies. Today miniaturisation is a major technological challenge. Material machining to micrometric or submicrometric scale becomes one of the key techniques for the future. Glass is often involved in these miniaturized devices. This interest can be explained by its properties: glass is transparent and has a good chemical durability. Many techniques of glass micromachining exist from laser to HF etching and sand powder blasting. In this work, we introduce a glass microstructuring technique, that we called Spark Assisted Chemical Engraving (SACE). It was presented for the first time in the Sixties to drill microholes in glass (diameter = 6 μ). Since the first use of SACE as machining technology in 1968, theoretical approaches were proposed in literature to understand the process. They are based on thermal models by finite elements method or on electrical characterization, with ohmic resistances calculations. They give a good quantitative approximation of the material removal rate. The goals of the thesis are to achieve a local understanding of the process and to highlight electrochemical and thermal phenomena involved around tool-electrode tip before and during SACE process. This thesis will try to answer two questions: How does SACE work? and how to apply it to microstructure glass? A new approach based on potential sweep is proposed to study the process. The originality consists in matching electrochemical measurements with high resolution photographs from the tool-electrode. This report is structured in three parts. A bibliographical part, which introduces not only glass as a material but also presents technologies for glass microstructuration (including SACE). A theoretical part, which focuses on describing current behaviour before spark formation, which allows material removal. It starts by a theoretical recall of variations of electric parameters (conductivity, resistance) as a function of gas hold-up. This theory is then applied to build a model, based on resistance calculations in the system. The goal of this model is to explain electrochemical measurements. An experimental part, which validates the theory developed to explain what happens before spark formation. Characteristics of sparks are then studied by a technique based on voltage pulses and used in a finite elements model. Finally, we will present concrete results, illustrating SACE possibilities to drill microholes. A mechanical prototype for SACE was developed during this thesis and is presented for microreactors fabrication and other glass microstructurations.