| Currently,PZT ferroelectric ceramic piles are bonded by using polymer based adhesive materials.Due to the low conductivity,poor aging performance and low anti-shock properties of the joints,the properties of the ferroelectric ceramic piles are greatly influenced.Solder powder and flux are mainly used in the of electric packaging,the joints show high strength,excellent stability and great conductivity,but due to the ferroelectric material thermal depolarization temperature limit,the traditional brazing process also cannot be applied in PZT ceramic piles connecting.In this study we proposes the use of a variable low-melting-point alloy as an interlayer of solder,and investigate the processes and mechanisms of the brazing technology based on the principle of Transient Liquid Phase bonding.The preparation of low-melting-point alloy powder and no-clean flux,as well as the TLP bonding of PZT ceramic were proposed in this study.Through the characterization and analysis of the experimental results,the following conclusions was obtained.The optimum process parameters of the preparation of solder alloy powder by liquid phase dispersion method are as follows:2g of low-melting-point alloy pellets were added to 40ml of PEG200,heated to 120℃,stirred for 5h,and then centrifuge and dry to obtain the powder.The powder show highly sphericity,good surface morphology without defects,and the median particle size is 30μm.The melting point of the alloy powder is 74.70℃,with molten temperature region less than 4℃,which can be used as solder alloy.Preparation process of no-clean flux:a mixture of ethanol,isopropanol,ethylene glycol and ethylene glycol monobutyl ether in a mass ratio of 53-40 to 5-2 is mixed to obtain a complex solvent,which has a boilling point of 86℃.13%lactic acid is added as an active agent in solvent,and 5%castor oil is added as a thixotropic agent.The matrix is obtained by stirring at 40℃for 4h,and then,added other compenents to obtain the no-clean flux.The self-made no-clean flux is light yellow liquid,with a stable physical properties,weak acidity,low viscosity,as well as great wetting properties.The pH of the no-clean flux is 4.86,the nonvolatile content is 16.17,the results of the solder joint test are so good that it can be used at 100℃.Using low-melting-point solder paste as the interlayer solder to bonding the PZT ceramic by Transient Liquid Phase process,and the holding time is set to 2h、4h、6h and 8h,respectively.The bonding joints is well combined without defects.The main phase of the bonding joints are CdAg、Ag5Cd8、Cd3Ag and Ag3Sn.With the prolonging of the holding time,the degree of homogenization of the intermetallic compound layer become higher,the thickness of IMC layer gradually widens,and the edge of the IMC gradually evolved into a scallop-like protrusion.The bonding joint strength adapt the welding requirement. |
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