Control Of Flexure Bonder For Flip Chip Bonding Interconnection System

In the Post-Moore Era,advanced chip packaging technology represented by wafer-level flip-chip direct packaging has continued to develop to cope with the changing trend of electronic production with miniaturization,thinness and 3D integration property.The latest state-of-art technics indicate that,the minimum diameter of LED chip solder ball is only about 10?m,the solder distance is<15?m,as well as I/O density is>10~3/mm~2,which results in extremely stringent requirements on the accuracy of bonding pressure(?±5N)and the accuracy of positioning(?±500 nm)duringhe flip-chip vertical interconnection process.Otherwise,it will cause impact crack,welding and even chip failure if the bonding force is too large or too small between solder balls and substrate.Therefore,how to simultaneously achieve high-accuracy,high-flexibility,and high-reliability chip interconnection has become a big challenging issue for developing an advanced flip-chip bonding system.To address the above-mentioned problems,the hybrid position/force fully closed-loop control strategy with integrator composed of inertial filter is proposed,which enables the flexure bonding system to run in the manner of high-efficiency,high-accuracy,and high-quality interconnection.Besides,a parameter tuning method based on quantitative bandwidth is proposed,in which only one parameter needs to be tuned,which provides a convenient means for the successful implementation of the position/force hybrid full-closed-loop control strategy.Finally,a series of validation experiments including ICIF comparing tests,closed-loop trajectory tracking,and actual flip-chip interconnection tests are carried out to verify the effectiveness of the proposed method.The main contents of this paper are as follows:(1)A few of pioneering studies such as the research background and significance of flip-chip packaging equipment are carried out.The domestic and foreign research status and requirements of position/force hybrid control for flip-chip packaging equipment have been thoroughly investigated.And the difficulties and key technologies of position/force hybrid control have been pointed out.The research methods and technical solutions have been formulated in this paper.(2)Starting from the flexure bonder of research object,the design procedure of flexure bonder is described in detail,and the static relationship between the displacement and force of the flexure bonder is established.Besides,the natural frequency model of the flexure bonder is derived by analyzing the dynamic relationship of the flexure bonder.Afterward,the system identification method of the flexure bonder is introduced.Based on the established dynamic model,the amplitude frequency characteristics and phase frequency characteristics of the flexure bonder are obtained by sine sweep tests.Finally,the model parameters of the flexure bonder are fitted by least square method,which lays the foundation for achieving the accurate control of the flexure bonder.(3)The problems existing in the absence of closed-loop control on the flexure bonder are analyzed and pointed out in detail in the viewpoint of the three evaluation indexes(Efficiency,Accuracy and Quality)of flip-chip interconnection effect.Then,the limitations of PID controller in controlling flexure bonder are pointed out.To this end,a novel integrator composed of inertial filter(ICIF)is proposed.Besides,the superiority of ICIF on the control of flexure bonder is revealed by comparative simulation experiments in the viewpoint of time domain and frequency domain.Moreover,the stability of the ICIF is proved via Routh criterion theory and numerical simulation.Finally,in order to achieve high-efficiency,high-accuracy,and high-quality interconnection,the hybrid position/force fully closed-loop control strategy with ICIF is proposed.(4)Focusing on parameters tuning for controlling flexure bonder,several common parameter tuning methods are investigated.It turns obstreperous to implement the control strategy for high-efficiency,high-accuracy,and high-quality interconnection,largely because of the difficulty in many parameters to be tuned.To this end,the characteristic of linear active disturbance rejection control(LADRC)is proved that it is equivelant to the characteristic of PD+ICIF and low-pass filter.And there are only two parameters to be tuned for LADRC.Besides,the parameter tuning method based on quantitative bandwidth is proposed by analyzing the parameter distribution law of the PD+ICIF for controlling the flexure bonder.Only one parameter needs to be tuned,which is easy to implement.Finally,a simulation experiment of tracking under different loads and different trajectories is carried out,which verify the effectiveness of the parameter tuning method based on quantitative bandwidth.(5)The experimental prototype of flip-chip interconnection system is established.With the developed control strategy,a series of validation experiments including ICIF comparing tests,closed-loop trajectory tracking,and actual flip-chip interconnection tests are successfully carried out in detail,which uniformly verifies that the developed flip-chip ASL bonding system can effectively perform high-efficiency,high-accuracy,and high-quality interconnection tasks.The results indicate that the maximum peak-to-peak positioning errors of different types of trajectory tracking are kept within±100nm.Besides,the maximum settling time of the bonding system is kept within 135ms.Moreover,it can be concluded that it successfully maintains a constant force of 300N with the deviation of±4N during the soft-landing process under 2812N/s,5732N/s and 10843 N/s loading speed,respectively.