There are two ways to put in and take out the PCB: one is to lift the whole scraper mechanism together with the template, the PCB will be pulled into or out of the PCB, using this way, the PCB positioning accuracy is not high; the other is the scraper mechanism and the template does not move, the PCB is "flat in and flat out", so that the template and the vertical separation of PCB, the positioning accuracy is high, the printing of the PCB is not high, and the positioning accuracy is high, and the printing is not high. This way of positioning accuracy is high, the shape of the printed solder paste is good.
Because of the PCB deformation or PCB pads on the graphic production is not accurate, the use of vision systems on the PCB datum mark positioning, and correction. This allows for less setup time and high accuracy, while also checking the position of the PCB pad pattern informing the operator once the error exceeds the deviation standard.
Different brands of printing machine positioning methods will vary. As shown in Figure 3-31 is a fully automatic printing machine positioning system schematic, CCD camera in the middle of the template and PCB position. PCB incoming, the camera automatically look for templates and PCB on the positioning mark (Mark), through the Mark point of the position of the alignment of the realization of the template and the precise positioning of the PCB.