Conductive Pattern Flash Sintering Mechanism And Parameter Optimization And Adjustment Method

The conformal load-bearing phased array antenna is a highly integrated functional component that has multiple functions such as electromagnetic radiation,beam scanning,heat dissipation,and load bearing.Integrated rapid-prototyping technology can be applied to the manufacture of functional components as it can perform printing and sintering of substrates,conductive paths,and load-bearing structures in a short time through a multimaterial and multi-jet printing process.Compared with the complex process of traditional step-by-step manufacturing and assembly,the components generated by this technology are highly integrated and adaptable.The sintering process in rapid-prototyping technology has been employed for the curing of accumulated materials to ensure that the materials can exert their corresponding mechanical and electrical properties.Compared with the common thermal sintering and microwave sintering processes,flash sintering is more compatible with rapid-prototyping technology,which uses high-power pulsed xenon lamps as the sintering light source,as it has the advantages of high sintering efficiency and low temperature rise.However,the conductivity of the sintered conductive pattern is poor because of the high energy release in a short time,and the sintering parameters are not matched,resulting in unstable electrical properties.This dissertation aims to reveal the mechanism of flash sintering and improve the quality of sintering.It conducts research through modeling,simulation,control,and experiments.The main contributions are as follows:1.A pre-sintering analysis model is established,and the solvent volatilization characteristics in the pre-sintering of nanometal particle ink are analyzed.Pre-sintering is divided into two stages.In the first stage,when the solvent volume is much larger than the metal solid,it can be equivalent to a strong volatilization model of a continuous medium.In the second stage,the solvent is excessively reduced,and the nano-metal particles bottom out and support each other to form a porous medium structure with small pores.At this time,based on the pre-sintering temperature field,a volatilization model is constructed based on the Darcy fluid equation to solve the second stage of pre-sintering.Parameter prediction is adjusted according to the ink characteristics.The detailed modeling and analysis of presintering are performed,which lays the foundation for the quantitative analysis of the sintering performance.2.A multi-scale analysis and performance-prediction model for flash-sintered silver nanoparticles is established.First,on the microscale,molecular-dynamics models are used to analyze the sintering state of nano-silver clusters under variable temperature fields,and the sintering characteristics of nanoclusters are analyzed by changing the lattice constants of the cluster particles.Second,on the macroscale,different sintering parameters are used to construct the flash-sintering temperature field according to the heat-transfer formula.Based on the characteristics of the sintering process of nano-silver particles,the two-phase flow dynamics are used(according to the Navier–Stokes equation)to simulate the mass and momentum transfer process of nano-silver particles during the sintering process in terms of viscosity change,melting,and connection with adjacent particles to form a sintering neck.By examining the results of the microscopic analysis in comparison with those of the macroscopic nano-silver multi-particle model,a quantitative analysis of the relationship between the sintering state of the nanoparticles and the electrical properties is conducted,and the mechanism of the influence of the sintering process parameters on the sintering performance is revealed.3.An adaptive sintering control method is proposed based on multi-sensor data feedback.We analyze the difference in surface morphology and the relationship between the surface temperature and the sintering state and propose a method for monitoring the sintering state based on the combination of the optical spot state capture method and the temperature distribution measurement method.Using this,the optimal weighting is calculated from the sensor data.After fitting the variable parameter of the sintering data,the sintering parameters are optimized by partial guidance,and the sintering state monitoring and sintering power optimization control are realized.4.A sintering quality monitoring and sintering energy adaptive control system is developed based on laser-reflection scanning.The morphology state is obtained by analyzing the change in the moving laser spot through dual cameras,and the morphology change of the nano-silver layer is measured with high repeatability and sensitivity.Combined with the temperature field distribution data,the sintering state is fused with variable weights.The empirical parameters are compared,the sintering state of the conductive pattern is monitored in real time,and the sintering parameters are adjusted after optimizing the calculation.This method is utilized in the development of microstrip antennas and energy storage devices;rapid and stable sintering of an 8-element microstrip antenna on the conformal substrate is realized.On comparing the pattern with the simulation,the main and side lobes are observed to have a similarity of 70%.In the energy field,the current collector,which is manufactured by adaptively adjusting the flash-sintering process,provides stable charge and discharge of more than 2000 cycles for the ionic capacitor.