Research Of Multi-channel Discharge And Forming Conditions In Silicon EDM

Silicon is one kind of typical hard and brittle materials with special electrical and physicalproperties, and it is becoming more and more widely used in the field of high technology. Thematerials are mainly removed by mechanical force when silicon is processed by traditional machining.And there will be some chips and cracks on the finished surface. However, electrical dischargemachining (EDM) removes materials by electrocorrosion during the process of spark discharge. Andthere is no limits on the hardness or brittleness of materials, so it’s quite suitable for processing silicon.Many scholars at home and abroad have done a lot of studies on discharge channel of traditional metalEDM. The purpose is to achieve the theoretical basis of higher processing efficiency and bettersurface quality through the researches of mechanism. However there is no report about the researchon discharge channel of semiconductor EDM. With the development of technology, the demands ofsemiconductor parts with various shapes on nondestructive testing (NDT) and space spectrumdetection are more and more pressing. In terms of manufacturing silicon parts, there is no report aboutsemiconductor EDM forming. This paper first studied the number of discharge channels of siliconEDM with the method of wire electrical discharge machining (WEDM) and found the multi-channeldischarge phenomenon of silicon EDM because of its special electrical properties. And themulti-channel discharge property has effects on the processing efficiency of EDM with differentworking areas. It established theoretical basis of improving the processing efficiency of silicon EDM.Secondly this paper developed EDM forming system for silicon specially and analyzed the continuousprocessing conditions for silicon EDM forming. At last the forming machining of typical parts wasproceed and achieved great processing results.In this paper, the specific research contents are as follows:(1) Studied the number of discharge channels of silicon EDM by the method of WEDM based onits special electrical properties. Established the equivalent circuit model of silicon WEDM andanalyzed the effects of multi-channel discharge on the processing efficiency of WEDM.(2) Developed special silicon EDM forming system and exploited the special servo controlsystem based on the rate of current pulse and voltage pulse.(3) During the period of silicon EDM forming, the black spot which can stop the processinggenerated on the machining surface easily. Analyzed the black spot and found it is copper oxidewithout electroconductibility. In order to avoid the generating of black spot, graphite electrode is adopted to change the electrode material and choose working fluid containing oxygen as little aspossible. This way is not good for generating the metal oxide without electroconductibility. On theother hand, the vibration or the rotation of electrode are added to improve the conditions of washing,cooling and chip removing between the electrodes. Experiments show that the electric spark formingof silicon can run stably with these mentioned methods above.(4) Proceeded technological tests of silicon EDM forming with the processing system andstudied the relationship between the feed of electrode and the rate of current pulse and voltage pulseunder certain technological conditions. Analyzed the effects of electrical parameters includes voltage,duty ratio and pulse width on processing efficiency and achieved optimized working parameters.(5) Proceeded silicon EDM forming of typical parts include five-pointed star, square and trianglewith the special EDM forming system and obtained great processing results.