1, the components correctly require the type, model, nominal value and polarity of the components of the assembly number to be in accordance with the product assembly drawing and schedule requirements, can not be misplaced.
2. Accurate position (1) The end or pin of the component should be aligned and centered as much as possible, and the soldered end of the component should be in contact with the solder paste pattern. (2) The placement position of components must meet the process requirements.
The two-end Chip component has a relatively large self-positioning effect. When mounting, the width direction of the component is 1/2~3/4 or more. It is overlapped on the pad, and the two ends of the length direction are connected to the corresponding ones. The solder paste pattern on the pad (see Figure 2-2) can be self-aligned when soldering, but if one of the terminals is not attached to the pad or does not touch the solder paste pattern, then it will be soldered. Will produce a shift or suspension bridge:
For SOP, SOJ, QFP, PLCC and other devices have a relatively small self-positioning effect, and the placement offset cannot be corrected by reflow soldering. If the placement position is outside the allowable deviation range, it must be manually adjusted before entering the reflow oven. Otherwise, it must be repaired after reflow, which will cause working hours, material waste, and even affect product reliability. During the production process, it is found that the placement coordinates should be corrected in time when the placement position exceeds the allowable deviation range. Manual placement or manual dialing requires accurate placement, pin-to-pad alignment, centering, and do not stick. Do not drag on the solder paste to avoid solder paste pattern sticking and cause bridging. 3, the pressure (patch height) is suitable