The Improvement And Performance Analysis Of Sn-Ag-Cu Lead-Free Solder Paste

This paper analyzed the properties of the Sn3Ag2.8Cu lead-free solder paste and flux, researched the reflow soldering technical conditions. A new type of flux has been developed by changing the components of the fluxes and improved the reflow soldering technical conditions. The solder paste has been prepared by using the improving flux. The printing properties and the jointing have been studied. The performance of the flux and the solder paste has been tested. The results show that:1. The original solder paste former welding spots by original reflow soldering process, but the welding spots have been oxidized seriously. The major problem is the original component can not fit to practical process. The properties of original flux unstable because of unfit rosin competent. High solvent content lead to decrease of the flux viscosity, and volatilization of the solvent.2. Improved the reflow soldering process parameters: through changing the ratio of the cacophonies components ,the stability of the flux has been improved; Good solvent component systems which can reduce the volatilization and higher dissolving ability was brought out .choosing new kinds and ratio of the active agents to improve the active abidance of the solder paste. Adding the reagent to form a protective film to avoid oxidization.3. Using the orthogonal design to select the rosins,activators,and surfactants, and get a new flux which can reducing the spread area most. When the PH value of the flux is 5, the density is 1.37g/ml, and contains 29.58% non-volatile, it can show rather good stability and milk white color .when it applied, and it has no rust effect on the base board.4. When the soldering micro-powder is account for 87.5% of the solder paste, it can be better printed than the other ones. Increasing the time stayed in the region of activation, the volume of the lacuna in the soldering point can be low down.5. The solder past optimized by this experiment has reached the first grade of JISZ3284.the spread rate of it is 87.51%. The soldering point is satiety brightness. It can also wetting the .the solid leftover after soldering is rather a bit and it is transparence colorless with no glutinosity.