Detailed description of SMT processing process

2022-08-05 108

Material acquisition: The material group receives the Production Notice and acquires materials according to the materials required for production. The requirements of the acquired materials are consistent with the material list, such as specification, model, quantity, certification, etc. Trim or pin shape the materials according to the technological requirements. When shaping, it should be noted that components with similar specifications and shapes must be inserted with different specifications, and after shaping, they should be marked, packaged and put back in place to avoid the mixing of components. Plastic materials include: Plastic materials include jumper, resistor, electrolytic capacitor, integrated block, radiator, diode, triode, inductor, etc. 

2. Patch: mainly coating solder paste on the corresponding position of the board according to the technological requirements and heating and curing. Preparation of solder paste: the solder paste should be refrigerated in the refrigerator (about 5℃), taken out and returned to room temperature (about 4 hours) before opening the lid, and stirred evenly. It can be used for about 0.5-1 hour; And correct the template and steel mesh: the missing pattern on the steel mesh and the PCB pad pattern are merged and aligned, and finally the relevant knob is locked. The amount of solder paste (lead or lead-free) used in SMT processing workshop is estimated according to the size and quantity of PCB; In use, we should pay attention to supplement the solder to keep normal printing leakage and avoid uneven printing of solder paste on each pad. Scraper speed is set at 12-40mm/S, and scraper pressure should be 0.5Kg-/30mm. Paste brushing can be done on a semi-automatic printing machine or a fully automatic printing machine. Automatic printing machine = upper plate+printing, one plate can be finished in 30s. For every 5 pieces of solder paste steel mesh processed, the printing machine automatically cleans once, and for every 20 pieces processed, it needs to be cleaned manually. The cleaning method is alcohol spray steel mesh. 

Entering the high-speed mounter: After the PCB is printed, it directly enters the high-speed mounter for mounting. The mounter is actually a kind of precise industrial robot, which is a combination of mechanical-electrical-optical and computer control technology. Through the functions of suction, displacement, positioning and placement, SMC/SMD components can be quickly and accurately attached to the designated pad position of PCB without damaging the components and printed circuit board. There are various material trays outside the mounter, and the materials are absorbed and mounted by the material suction device of the mounter. The selection of materials runs according to the program set by the programmer in advance, so each material can be mounted in an orderly manner. High-speed mounter mainly mounts small materials (resistors, capacitors, electronic products such as diodes and diodes). After mounting, PCB board enters multifunctional mounter for mounting large materials.