Study On Reliability Of Lead - Free Mixed - Batch Process For Military Electronic Products

It has become an urgent problem to be solved how to solder lead devices and lead-free devices in lead process and assure its reliability for military electronic products. This paper is based on experiments and the subject of nonferrous metals materials for theoretical guidance. Firstly,it has an research on parameters of mixed process of military electronic products,including printing parameters,placement parameters and reflow soldering parameters,etc. The experiments finished SMT mixed welding under lead components, lead-free components and lead solder paste. Secondly,the PCB has made the reliability test, including the temperature cycling test and vibration test. Finally, the solder joints were detected by using X-Ray detector and the morphology and alloy layer of the components in different solder joints were analyzed by metallographic microscope. In order to achieve the stable, controllable and reliable production process,the technology can be operable,widely and consistent.In the experiment the solder paste composition is Sn62Pb36Ag2. The lead solder paste welding lead components, lead-free components of pure tin, nickel, palladium, tin silver copper and other coating conditions. When the welding temperature control between the 235℃ plus or minus 5℃, more than 179℃ reflux time is about 80 s and more than 220 ℃ for at least 40 seconds, the result can guarantee to get the effective of the Cu6Sn5 alloy layer thickness in 4um range.