Advances in polycrystalline diamond (PCD) micro drills for efficient micro-hole machining in hard-brittle materials: a review of design, fabrication, and performance

Hard-brittle materials offer outstanding mechanical, optical, and chemical properties, making them highly valuable for aerospace and astronomy applications. However, their extreme hardness and brittleness present significant challenges for micro-hole machining. While non-conventional methods like laser machining offer potential, they often result in poor precision and quality of the micro-hole. Conventional mechanical micro-drilling using polycrystalline diamond (PCD) micro drills remains the most effective option due to its accuracy, efficiency, and cost-effectiveness. This review discusses the material selection, geometric design, fabrication methods, and drilling performance of PCD micro drills, emphasizing advances in tool design, fabrication techniques, and process optimization to improve machining outcomes of the micro-hole in hard-brittle materials.