Mechanism Analysis And Experimental Research On Multi-frequency Ultrasonic Machining Of Engineering Ceramics

With the rapid development of electronic technology,the high integration of electronic components has become an inevitable trend.The highly integrated package module requires a good heat dissipation bearing system.Especially in recent years,the rapid development of multi-chip module technology has put forward higher requirements for the heat dissipation capability of the load-bearing circuit board.Ultra-high thermal conductivity ceramic substrate is an ideal packaging material for a new generation of large-scale integrated circuits due to excellent thermal conductivity and air tightness.From blanks to finished products,ceramic substrates usually require secondary processing,such as drilling,cutting,and grooving.In particular,a large number of round and irregular holes need to be processed,but the hard and brittle nature of ceramic materials brings extreme troubles to their processing.At present,the most important reason for restricting the wide application of engineering ceramic materials is the high processing cost.According to statistics,the processing cost of engineering ceramic parts accounts for more than 50% of the total cost.For many precision parts,the processing cost is even as high as 90%.Obviously,the large-scale application of ultra-high thermal conductivity ceramic substrates depend on the development of the processing technology of engineering ceramic parts.Ultrasonic machining is an effective method for processing hard and brittle materials,such as ceramics.Because it is not affected by the electrical and chemical properties of the workpiece and does not change the physical and chemical properties of the workpiece.However,due to the limited power of the existing ultrasonic power supply,it is difficult to increase the amplitude of the single-frequency ultrasonic machining system,which makes the efficiency of the traditional ultrasonic machining lower and cannot fulfill the requirement of industrial production.Therefore,this paper proposes a multi-frequency machining method for engineering ceramics.Through the research on the mechanism of multi-frequency ultrasonic machining of engineering ceramics,an experimental system for multi-frequency ultrasonic machining of engineering ceramic materials was developed.It achieves high-precision and high-efficiency for drilling engineering ceramic holes.The main research contents and conclusions of this paper are as follows:1.By studying the collision characteristics of free mass and the critical conditions of engineering ceramic material cracking,the mathematical model of material removal rate for multi-frequency ultrasonic machining was established.The research shows that in the multi-frequency ultrasonic machining unit,the free mass is used for storaging and transfering energy.By the collision and impact of free mass,low frequency and large amplitude vibration can be introduced on the basis of the traditional ultrasonic machining,thereby the material removal rate is improved effectively.2.Through the design calculation and simulation analysis of the components of the multi-frequency ultrasonic machining unit,the experimental system of multi-frequency ultrasonic machining of engineering ceramic materials was developed,and the vibration frequency measurement and drilling performance test were carried out.The research shows that the introduction of free mass can generate multiple low-frequency vibrations based on the original ultrasonic frequency,and the maximum frequency is measured at 6754 Hz,which is basically consistent with the theoretical calculation value,which further verifies the feasibility of the principle of multi-frequency ultrasonic machining.3.The effects of process parameters such as the thickness of free mass,the movement gap of free mass and the axial static pressure on material removal rate were studied.The results show that the thickness of the free mass has the greatest influence on the material removal rate,while the motion gap of the free mass is less,and the axial static pressure has the least influence.When the parameter values are 4.00 mm,1.80 mm and 40 N respectively,the material removal rate of engineering ceramics multi-frequency ultrasonic machining can be increased by about 8 times compared with conventional ultrasonic machining.4.The capturing device of free mass was designed,and the influence of capture time of free mass on the surface quality was studied.The research shows that with the increase of the capture time of free mass,the collapse area of the hole being processed is gradually reduced.When the capture time is 30 s,the collapse area at the entrance of the machined hole only accounts for 0.736% of the total area.The problem of edge collapse has been improved basically.On this basis,the double-sided machining of the engineering ceramic hole was carried out,and the guiding effect of the blind hole was utilized to solve the problem of edge collapse at the exit of the machined hole effectively,and the surface quality of the machined hole was further improved.