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1. The full name of SMT is Surface Mount (or mounting) technology, which in Chinese means surface adhesive (or mounting) technology. 2. Generally, the temperature specified in an SMT workshop is 25±3°C. 3. Solder paste 3.1 Materials and tools required for solder paste printing: solder paste, steel plate, squeegee, wiping paper, lint-free paper, cleaner, and stirring tool. 3.2 The components of solder paste include metal powder, solvent, flux, anti-sagging agent, and activator. Its main components are tin powder and flux, with a volume ratio of approximately 1:1 and a weight ratio of approximately 9:1. 3.3 The flux begins to volatilize in the constant-temperature zone to carry out a chemical cleaning process; its main function during welding is to remove oxides, reduce the surface tension of the molten tin, and prevent re-oxidation. Soldering fluxes based on rosin can be divided into four types: R, RA, RSA, and RMA; 3.4 Leaded solder has a Sn/Pb ratio of 63/37, with a melting point of 217°C. The lead-free solder Sn/Ag/Cu has a composition of 96.5/3.0/0.5, with a melting point of 217°C. 3.5 When solder paste is taken out of the refrigerator and used after opening, it must go through two important processes: warming up and mixing. The purpose of warming up is to bring the temperature of the refrigerated solder paste back to room temperature, facilitating printing. If the temperature is not raised, solder beads are likely to form after the PCB enters the reflow oven. 3.6 The principle for taking solder paste is first-in, first-out. 3.7 The solder paste available on the market today actually has only a viscosity duration of 4 hours. 4. Steel mesh 4.1 The common methods for manufacturing steel mesh are: etching, laser, and electroforming. 4.2 The commonly used material for SMT stencil is stainless steel. The thickness is 0.15 mm (or 0.12 mm). 4.3 In SMT, the openings in the steel mesh should generally be 4 um smaller than the PCB pads, which helps to prevent the occurrence of solder ball defects. 5. For PCB 5.1, the commonly used PCB material is FR-4; 5.2 The purpose of vacuum packaging for PCBs is to prevent dust and moisture. 5.3 The warpage of the PCB shall not exceed 0.7% of its diagonal length; 6. Components 6.1 Common passive components include resistors, capacitors, inductors, diodes, etc., and these components are picked up by the nozzles of a pick-and-place machine, which are simply referred to as nozzles ； Active devices include transistors, ICs, etc. 6.2 The controlled relative temperature and humidity for the component drying oven are