Process Method Analysis Of Electrolytic Jet Polishing Carbide Micro-drill Bits

With the progress of electronic information technology,the material composition of Printed circuit boards（PCB）is becoming more and more complex,and the surface quality of holes is required more and more.Since carbide micro-drill bits are the main tool used for drilling PCB,the drilling performance of micro-drill bits is required to be better and better.In the process of drilling PCB,the drilling performance of micro-drill bits are affected by the surface quality.Therefore,it is of research significance to use surface polishing technology to improve the surface quality of carbide micro-drill bits,and thus improve the drilling performance of carbide micro-drill bits.Electrolytic jet polishing method can improve the surface quality by using the anode workpiece to undergo selective electrochemical dissolution.Because of its advantages of high adaptability to workpiece shape,high safety,low cost and fast material removal rate.Recently,electrolytic jet polishing method has gradually become a research hotspot for domestic and foreign researchers.In this study,carbide micro-drills were used as the research object to analyze the parameters of electrolytic jet polishing process,and the influence of process parameters on the performance of carbide micro drills was analyzed through a combination method of experimental research and theoretical analysis.Firstly,the theory of electrolytic jet polishing technology is explained,and the jet structure and flow field characteristics of electrolytic jet polishing are analyzed.In addition,elaborating and analyzing each process parameter in the electrolytic jet polishing process,which can provide some theoretical basis for the subsequent design of the process parameters and optimization of the process parameters.Next,a set of electrolytic jet polishing carbide micro-drill device were designed and built,which was mainly composed of electrolytic power supply,servo system,plating solution circulation system,anode rotation device and other parts.The cathode and anode materials for electrolytic jet polishing test were determined,and configured the electrolyte.The scanning electron microscope,white light interferometer and super-depth-of-field microscope were used to characterize and test the performance of carbide micro-drills.Then,the effects of electrolytic jet polishing process parameters（polishing time,jet speed,current density and pole spacing）on the surface quality of carbide micro-drill bits were systematically investigated by single-factor tests to determine a better range of process parameters.On this basis,the surface roughness of the carbide micro-drill was taken as the index,and the electrolytic jet polishing process parameters were optimized by four-factor and three-level orthogonal tests to determine the order of influence of four process parameters on the surface roughness of the carbide micro-drill:current density>jet speed>pole spacing>polishing time.The best combination of process parameters was T₁V₂I₂D₂,which the polishing time was 60 s,jet speed was 1.8 m/s,current density was 12 A/dm²and pole spacing was 20 mm.Finally,electrolytic jet polished carbide micro-drill bits were tested under the best combination of process parameters.The surface of carbide micro-drill bit after electrolytic jet polishing was smooth and flat,and the surface roughness values of unpolished and electrolytic jet polished carbide micro-drill bit were 1.1μm and 0.34μm,respectively.The wear of electrolytic jet polished carbide micro-drill bits was much lower than that of unpolished carbide micro-drill bits after drilling 50 holes and 100 holes in comparative drilling tests.Under different drilling speed conditions,the number of holes drilled by the electrolytic jet polished carbide micro-drill bit was more than that of the unpolished carbide micro-drill bit.In addition,when the drilling speed was 6000 rpm,the number of holes drilled in the electrolytic jet polished carbide micro-drill bit was as high as 400 holes,which was 2.6times the number of holes drilled in the unpolished carbide micro-drill bit.The results showed that electrolytic jet polishing improved the surface quality of the carbide micro-drill bit and enhanced the wear resistance and drilling performance of the carbide micro-drill bit.