What is the benefits of using an online AOI detector after solder paste printing?Before the paste is printed, the perfect combination of PCB bare plate and tin paste requires perfect technical means。At least need a fully automatic solder paste printing machine with more than 900 rpm for complete stirring and defoaming of thawed solder paste.After evenly stirred tin paste, good viscosity, no foaming, can be perfectly combined with the PCB plate in the printing process of tin paste.The pass rate of subsequent solder paste printing is usually ideal, which lays a good foundation for the later patch assembly。If the tin paste printing process meets the requirements, the number of defects found in the ICT function detection can be greatly reduced. If the tin paste printing process can not meet the requirements, there are many quality problems in the later process.

Typical printing defects include the following points :

1. The solder on the pad is less than
2. Too much solder on the pad.
3. The overlap of solder to the pad is.
4. Solder bridge between pads.A slight little tin rarely leads to defects, while serious situations, such as fundamental miss solder, almost always cause defects in ICT.Insufficient solder may be a cause of missing components or open solder joints. However, deciding where to place AOI needs to recognize that component loss may occur for other reasons that must be placed in the inspection plan.A phase of inspection most directly supports process tracking and characterization.Quantitative process control data at this stage include printing offset and solder quantity information, and qualitative information about printed solder will also produce.The best control method is to use the AOI system in this process. And usually the best control method of the patch quality is to use an on-line AOI quality detector after solder paste printing, which is specially used to detect the quality, quantity and defect of solder printing.After this control, the quality control effect is better in the next process, and then an on-line AOI placed in front of reflow welding for secondary quality control. This level controls the mounting quality of the placement machine, so that the quality of reflow welding is further controlled. Such SMT processing quality is almost perfect if one more online or offline AOI installed after reflow oven.