SMT is Surface assembly Technology (short for Surface Mounted Technology), is the most popular technology and process in the electronic assembly industry. Features: high assembly density, small size and light weight of electronic products, the volume and weight of the patch components are only about 1\/10 of the traditional plug-in components, generally after the use of SMT, the volume of electronic products is reduced by 40% to 60%, and the weight is reduced by 60% to 80%. High reliability and strong vibration resistance. Low defect rate of solder joint. Good high frequency characteristics. The so-called SOP is the uppercase of the first letter in the three words of Standard Operation Procedure, that is, standard operation procedure, which describes the standard operating procedures and requirements of an event in a unified format, used to guide and standardize daily work. The essence of SOP is the quantification of details, in more general terms,SOP is the elaboration and quantification of critical control points in a process.