Research On Roll-bond Aluminum Vapor Chamber Sealing Technology And Automatic Equipment Development

At present,the power consumption of 5G base stations has reached more than 3 times that of 4G base stations.The maximum power consumption of a single AAU(active antenna unit)can reach 1500 W.Roll-bond Aluminum Vapor Chamber(RAVC)is used to replace pure aluminum fins due to their high thermal conductivity,small size restrictions and light weight.Since the RAVC uses the phase change of the working fluid to transfer heat and its cavity needs to be kept vacuum and sealed,its sealing process directly affects the production yield and service life.In this paper,the sealing process of the RAVC is researched,and the main research contents are as follows:Because the flow channel of RAVC is covered by graphite layer,the production yield of cold welding is low.The welding heat affected zone should be small because of working fluid cracking at high temperature.And the injection pipe of RAVC is required to be completely removed.Based on these three characteristics,the sealing process was designed to cut off the injection pipe and then weld with laser in the pressure holding state,which reduced the cold welding process and reduced the production defect rate.At the same time,based on the advantages of pulse laser welding with non-contact welding,no special requirements for tooling and fixtures,energy concentration and small heat affected zone,pulse laser welding was used for sealing.Then,the finite element model of pulse laser welding process of RAVC was established.The parameter of material at high temperature was obtained through JMatpro material calculation software.FORTRAN language were used to define and load heat source.And the temperature field changes during the pulse laser welding process were analyzed with the ABAQUS software.The process parameters that affect the welding temperature field,such as peak power,pulse width,welding speed and welding frequency were simulated and compared to obtain the relevant influence rules.It was found that the peak power and pulse width affected the maximum temperature of the weld center,while the welding speed and welding frequency had little effect on it.Under the set working conditions,the material cannot reach the melting point because the heat flux density was too small when the peak power was 1kW.A sealing experimental test platform of RAVC was set up to explore the influence of process parameters,such as peak power,pulse width,welding speed and welding frequency,on the quality of the sealing with the method of single factor variable.And it was found that the production yield would decrease,whether these parameters were too low or too high,due to welding defects.And we obtained beautiful fish-scale welds with high sealing yield under the experimental conditions,when the peak power was 3kW,the pulse width was 5ms,the welding frequency was 10 Hz and the welding speed was 1.5mm/s.Then,based on the coupling relationship between peak power and pulse width,and between welding speed and welding frequency,the compound influence rules of the two pairs of process parameters on the sealing quality were analyzed.And the application conditions of the established finite element model was analyzed by the comparison of simulation results and experimental results.Through the strength comparison test,it was preliminarily proved that the graphite layer of the flow channel of RAVC would weaken the strength of the sealing weld.The designed sealing process was verified.According to the designed RAVC sealing process,the RAVC sealing automation equipment that can realize automatic loading and unloading,cutting of the liquid injection pipe and sealing was developed.