Study On Electromagnetic Compaction Preparation Technology,Microstructure And Properties Of Cadmium-free Silver-based Intermediate Temperature Filler Metals

Cadmium-free silver-based intermediate temperature filler metal has a moderate melting point,good wetting and soldering performance,and higher self-strength,ductility,and is widely used in home appliances,microelectronic packaging,aerospace and other industries,is the most common of a medium temperature brazing filler metals used in current industrial production.At present,the preparation of domestic cadmium-free silver-based intermediate temperature filler metals is mainly traditional rolling process.The traditional technology has the disadvantages of many process steps,long production cycle,unable to avoid the traditional high-temperature melting part of brittle phases,low rate of finished product and low production efficiency.For cadmium-free silver-based intermediate temperature filler metal is difficult to forming,the traditional process is complicated and easy to produce brittle phase,this paper uses a new method for preparing silver-based solder.The silver-based solder foil Ag40Cu23Zn31In4Ni2 was prepared by the method of powder electromagnetic compaction and liquid phase sintering.Powder electromagnetic compaction experiment was carried out by the low-voltage electromagnetic pulse forming machine.In order to obtain high density solder compacts,the effect of discharge voltage and pressing times on the density of the blank was investigated and reasonable pressing process parameters were obtained.The result shows that: when the energy storage capacitor and the coil number is certain,with the increase of discharge voltage,the density of the Ag40Cu23Zn31In4Ni2 silver-based solder compact is started to increase,then the rate of increase slowed,and finally declined.Pressing times have little effect on the density of the compacts,a single pressing is sufficient to obtain a high density compacts.The reasonable pressing process parameters of this experiment are as follows: the powder is pressed under 1300 V discharge voltage by single pressing.The liquid phase sintering of compacts was carried out under argon protection of the SG-GL1200 L vertical tube furnace,for finally obtaining high density and high performance of solder,systematic analysis of the influence of sintering temperature and time on the solder density,organization and spreading performance,so as to obtain the reasonable sintering process parameter combination.The result shows that: when keeping a certain sintering time,with the increase of temperature,the sintering sample density and spreading properties improve within a certain range of sintering temperature;while keeping a certain sintering temperature,with the increase of sintering time,sintering sample density and spreading properties reduced.The reasonable sintering process parameters of this experiment are combined as follows: the sintering temperature is 550°C and the sintering time is 0.5h.The brazing properties and microstructure of the Ag40Cu23Zn31In4Ni2 silver brazing filler metals prepared under the reasonable pressing and sintering process parameters were tested and analyzed.Microstructure and phase composition of solder and weld were respectively analyzed by microstructure observation under optical microscope and scanning electron microscope,EDS energy spectrum analysis and phase diagram analysis,and the spreadability,butt and lap welded joints performance of the solder was tested.The result shows that:(1)The solder prepared by this process and the copper plate has good wettability,and the spreading area reached 298.5mm2;the tensile strength of the welding seam can be reached 165.7Mpa,shear strength reached 174.5Mpa;excellent solder brazing properties to meet the use requirements.(2)The microstructure of Ag40Cu23Zn31In4Ni2 solder is compact and uniform,which is mainly composed of large white silver-based solid solution matrix and gray and black copper-based solid solution,on the base along with the fine In-Ag solid solution structure;The ?-Cu solid solution is arranged in a staggered way,and there is a certain amount of black Ag-Cu and Cu-Zn brittle solid solution in the gap,which has a negative effect on the microstructure and properties of the solder.(3)The microstructure of the solder joint is relatively compact,which is composed of a large white Ag based solid solution matrix and gray Cu based solid solution,with the "pattern" of state organization;the solder to the base material has the obvious diffusion,formed the irregular shape of the eutectic structure at the junction,both the occurrence of a good metallurgical reaction and combination.The results can provide theoretical and data support for the engineering application of electromagnetic compaction to fabrication of cadmium-free silver-based intermediate temperature filler metal.