Design And Application Of Vision System And Single-phase Current Driver For Wafer Level Flip-chip Packaging Equipment

The wafer bonding process is a continuous process in which the vision system is responsible for positioning correction,and the single-phase current driver is responsible to provide accurate current to the bond-head motor to drive bond-head to bond chips to the substrate.However,in the research and development stage,there is often a problem that the substrate template matching deviation is too large.It is confirmed that there is flaw on previous template edge detection algorithm in the flip-chip equipment vision system.The edge detection of the template is incomplete,and some edges are missing,which results in excessive template matching deviation.The other issue is that the single-phase current driver in the motion control system cannot achieve the high/low gain switching to provide different current for both precise position control and precise force control,which results in excessive oscillation of the bond-head at the force/position switching point.The machine vision and motion control systems are two important modules in the flip-chip equipment.The wafer bonding process needs to be completed on the basis of precise positioning of the vision system,combined with the precision motion control technology.Only when these two modules are optimized at the same time,the existing problems can be solved.These two core modules jointly support the wafer bonding process.With these two modules,high-precision wafer level flip-chip packaging can be realized.To achieve above goal,this paper focuses on following tasks:1.Design of machine vision hardware system and light source lighting system.The whole vision system is divided into four modules: wafer vision,flip-chip vision,workbench vision and bonding vision.Four vision modules need appropriate selection of the cameras,lens,and light source lighting modes,according to the actual working conditions.2.An adaptive Canny edge detection operator based on central weighted MTM algorithm and Otsu algorithm is proposed.The improved Canny operator is used to replace the original edge detection algorithm of vision system.Through experiments and simulation,the complete template edge is detected and the template matching deviation is reduced.3.As the existing single-phase current driver cannot achieve high /low gain switching.To solve the problem,a driver with high/low gain switching circuit is designed.And the high/low gain switching delay time of the driver is obtained through the experimental test.It provides the foundation to solve the oscillation problem of bond-head at force/position switching point.4.The open and closed loop channels of the driver are tested,to obtain performance parameters of the driver.MATLAB is used to fit the relationship curve between the input and output.Theoretical analysis and supporting data are provided for accurate control of bond-head motor force/position switching.The influence of the driver high/low gain switching on the force/position switching of the bond-head motor is tested,and the oscillation mechanism of the force/position switching point is analyzed.Both the high/low gain switching of the driver and the force/position switching algorithm in motion control card are implemented in the low level DSP real time operating system to reduce the delay time of the driver high/low gain switching caused by software implementation to prevent large oscillation of bond-head at force/position switching points.