Tribological performance and wear mechanism of AlCrSiN-DLC composite coatings on PCB carbide microdrills

Abstract The tribological properties of PCB microdrills have become a critical factor affecting the rapid development of the printed circuit board microvia machining industry. In this study, AlCrSiN, DLC and AlCrSiN-DLC composite coatings were deposited on cemented carbide microdrills by the magnetic filtered cathodic arc deposition (FCVA) method, and the optimal coatings that can enhance the tribological performance of PCB microdrills were derived through the observation of the surface topography of the coatings and analysis of the friction and wear. The wear process of coated microdrills is generally influenced by the coatings’ surface finish, friction coefficient, and wear resistance. Among the three groups of coatings, the AlCrSiN-DLC composite coating and the DLC coating have a more polished surface morphology, while the friction coefficient of the AlCrSiN-DLC composite coating is the lowest, only 0.112, which is nearly 50% of the friction coefficient of the DLC coating. And the addition of AlCrSiN as a transition layer enhances the adhesion of the DLC coating, which makes the composite coating have only slight abrasive wear and oxidative wear during the friction process, and the amount of abrasion is much less, which effectively enhances the wear resistance of the microdrill. Verified by drilling experiments: When drilling up to 1800 holes, the hole wall roughness of AlCrSiN-DLC coated microdrill is the lowest among the three groups of coatings, which is 4.790 μm. And as the number of drilled holes increases up to 4000, the roughness of the hole wall decreases to 4.204 μm, which indicates the superiority of its self-lubricating property. The excellent microjunction drilling performance of AlCrSiN-DLC composite coating is proof that AlCrSiN-DLC composite coating combines the advantages of low friction characteristics of DLC and wear resistance of AlCrSiN, and has the best tribological performance.