Cutting edge preparation of microdrills by shear thickening polishing for improved hole quality in electronic PCBs

Printed circuit boards(PCBs)are representative composite materials,and their high-quality drilling machining remains a persistent challenge in the industry.The finishing of the cutting edge of a microdrill is crucial to drill performance in machining fine-quality holes with a prolonged tool life.The miniature size involving submicron scale geometric dimensions,a complex flute shape,and low fracture toughness makes the cutting edge of microdrills susceptible to breakage and has been the primary limiting factor in edge preparation for microdrills.In this study,a newly developed cutting edge preparation method for microdrills was tested experimentally on electronic printed circuit boards.The proposed method,namely,shear thickening polishing,limited the cutting edge burrs and chipping on the cutting edge,and this in turn transformed the cutting edge’s radius from being sharp to smooth.Moreover,the edge–edge radius could be regulated by adjusting the processing time.PCB drilling experiments were conducted to investigate the influence of different cutting edge radii on wear,hole position accuracy,nail head value,and hole wall roughness.The proposed approach showed 20%enhancement in hole position accuracy,33%reduction in the nail head value,and 19%reduction in hole wall roughness compared with the original microdrill.However,a threshold is needed;without it,excessive shear thickening polishing will result in a blunt edge,which may accelerate the wear of the microdrill.Wear was identified as the primary factor that reduced hole quality.The study indicates that in printed circuit board machining,microdrills should effectively eliminate grinding defects and maintain the sharpness of the cutting edge as much as possible to obtain excellent drilling quality.Overall,shear thickening polishing is a promising method for cutting edge preparation of microdrills.Further research and optimization can lead to additional improvements in microdrill performance and contribute to the continued advancement of printed circuit board manufacturing.

Edge preparation methods for cutting tools:a review

Edge preparation can remove cutting edge defects,such as burrs,chippings,and grinding marks,generated in the grinding process and improve the cutting performance and service life of tools.Various edge preparation methods have been proposed for different tool matrix materials,geometries,and application requirements.This study presents a scientific and systematic review of the development of tool edge preparation technology and provides ideas for its future development.First,typical edge characterization methods,which associate the microgeometric characteristics of the cutting edge with cutting performance,are briefly introduced.Then,edge preparation methods for cutting tools,in which materials at the cutting edge area are removed to decrease defects and obtain a suitable microgeometry of the cutting edge for machining,are discussed.New edge preparation methods are explored on the basis of existing processing technologies,and the principles,advantages,and limitations of these methods are systematically summarized and analyzed.Edge preparation methods are classified into two categories:mechanical processing methods and nontraditional processing methods.These methods are compared from the aspects of edge consistency,surface quality,efficiency,processing difficulty,machining cost,and general availability.In this manner,a more intuitive understanding of the characteristics can be gained.Finally,the future development direction of tool edge preparation technology is prospected.

Review on the progress of ultra-precision machining technologies

Ultra-precision machining technologies are the essential methods, to obtain the highest form accuracy and surface quality. As more research findings are published, such technologies now involve complicated systems engineering and been widely used in the production of components in various aerospace, national defense, optics, mechanics, electronics, and other high-tech applications. The conception, applications and history of ultra-precision machining are introduced in this article, and the develop- ments of ultra-precision machining technologies, espe- cially ultra-precision grinding, ultra-precision cutting and polishing are also reviewed. The current state and problems of this field in China are analyzed. Finally, the development trends of this field and the coping strategies employed in China to keep up with the trends are discussed.

Anhydrous based shear-thickening polishing of KDP crystal

Based on the special physical–chemical characteristics of optical crystal in the field of aeronautics,a new anhydrous based shear-thickening polishing(ASTP)method has been proposed to restrain deliquescence and to improve physical properties for KDP machining.The ultraprecision polishing of KDP crystal is completed by ASTP.A kind of anhydrous based thickening polishing slurry(ATPS)was proposed in our work,and high-performance rheological properties were determined to achieve the ASTP of KDP crystal.A material removal model of ASTP in KDP machining is established,followed by the verification experiment of the prediction model.The maximum error of the predictive model is only 9.8%,which proves the validity of the material removal model for KDP polishing.The polishing experiments were carried out on the polishing platform developed by ourselves.The results show that the new polishing method can polish20 mm×20 mm×5 mm KDP crystal and obtain a super-smooth surface with a surface roughness of 1.37 nm and high shape accuracy.The surface accuracy of polished KDP crystal reaches up to0.68 k(RMS).The experimental results show that the ASTP is a potential ultra-precision machining method for KDP crystal.