Research On A PCB Process Based Piezoelectric Microfluidic Pump Integrated Into PCB

With the continuous improvement of the process of semiconductor device fabrication,more and more components that can be integrated in the chip,resulting in an increase in the amount of heat generated during operation.The working performance of the chip will reduce when the working temperature is too high.The thermal problem of the chip will become the bottleneck of the development of the integrated circuit.At present,the problem of chip overheating can not be solved effectively.The main reason is that the liquid cooling system with high heat dissipation efficiency is large in volume and low in integration.It can not be widely used in chip heat dissipation.As an external driving source of liquid cooling systems currently,microfluidic pumps,which provide driving force for fluid flow.The pumps needs high pressure output and accurate flow control.The processing technology of microfluidic pumps made of materials such as silicon,quartz and high molecular polymers is complicated,which makes microfluidic systems both huge and complex,and it is difficult to integrate with other components of microfluidic systems.Printed circuit board(PCB)based process microfluidic pumps currently researched are valveless pumps and passive valve pumps,which cannot achieve precise control of liquid flow.Researches on microfluidic pumps that can be integrated into PCB will provide a solution for further miniaturization and integration of microfluidic systems with low costs.The structure and principle of the microfluidic pump integrated on the PCB should be compatible with the PCB process and have sufficient output pressure to drive the liquid cooling chip.In previous works,Wang and Pan(Journal of Intelligent Material Systems and Structures 2016 27(16): 2237-2248)developed an active piezoelectric microfluidic valve with annular boundary and established an active control flow model based on a deformation mathematical model of partially covered circular piezoelectric unimorph actuator for the clamped support condition under voltage control(Wang and Huo,Journal of Intelligent Material Systems and Structures 2010 21(16): 1603-1616).The maximum flow rate of the valve is 3 mL/min when the differential pressure between inlet and outlet and voltage are respectively 1 kPa and 150 V.On this basis,the principle and structure of a PCB process based piezoelectric microfluidic pump integrated into PCB are proposed and realized in this paper.The flow theory and PCB process based design of a piezoelectric microfluidic pump integrated into PCB is researched.The flow characteristics of the fabricated microfluidic pump are experimentally tested.The major research works completed in this dissertation include:First,the principle and structure of a PCB process based piezoelectric microfluidic pump integrated into PCB are proposed and realized in this paper.It is composed of a cylindrical pumping unit and two piezoelectric microfluidic valves with annular boundary.This pump can control the flow of liquid accurately.Second,the characteristics for liquid flow of the microfluidic pump are simulated by the finite element method,and the flow characteristics of the liquid in the pump chamber and the valve chamber are obtained respectively,which provided a basis for establishing the flow model.The flow characteristics of PCB process based piezoelectric microfluidic pump are studied.The solid-liquid coupling model for deformation and output pressure model of the pumping unit are established.The influence of the height and radius of the pumping chamber on the output pressure of the pumping unit is analyzed.The results show that the pumping unit with small pump chamber height and large pump chamber radius has a large output pressure.Third,based on the solid-liquid coupling model and the output pressure model,the flow model of the piezoelectric microfluidic pump is established by the circular tube flow formula.The results show that the flow rate of the microfluidic pump varies with the voltage amplitude and the inner radius of the annular boundary.The increase and linear increase,the flow rate of the microfluidic pump decreases with the increase of the pump chamber height and the outer radius of the annular boundary.Fourth,the PCB process based design and manufacturing technology of a piezoelectric microfluidic pump integrated into PCB is researched utilizing PCB as a platform.The microfluidic pump substrate with toroidal pads,the annular boundary and the chamber walls are machined using a standard PCB process.The annular boundary,the chamber walls and the capillary copper tube are welded on the microfluidic pump substrate,and the circular piezoelectric unimorph actuator is welded on the annular chamber to form a microfluidic pump.Finally,the experimental test platform for the deformation of the circular piezoelectric unimorph actuator is built.The relationship between the deformation and the voltage of the circular piezoelectric unimorph actuator is obtained.The flow experimental test platform of the piezoelectric actuated microfluidic pump is built.Verify the relationship between the flowrate of the microfluidic pump and its structure.The relationship between the flow rate of the piezoelectric microfluidic pump and the voltage is tested.The maximum flow rate and the back pressure of the microfluidic pump are obtained.The proposed principle and structure of a PCB process based piezoelectric microfluidic pump integrated into PCB are suitable to be integrated into PCB.The established flow model provides a theoretical basis for optimizing the structure of the microfluidic pump.The proposed integration method is compatible with the PCB process,and is beneficial to integrate the fabricated PCB process based piezoelectric microfluidic pump with other microfluidic components to realize complicated microfluidic systems on PCB.It is suitable for applications where cooling chip.The research work provides a novel solution for cooling chip,and is of great significance for promoting the development of integrated circuit technology.