1. Correct components:

SMT patch processing requires that the type, model, nominal value and polarity of each assembly number component must comply with the product assembly drawing and BOM requirements, and must not be pasted in the wrong position.

2. Accurate position:

During SMT patch processing, the ends or pins of the components should be aligned and centered with the pad pattern as much as possible, and it is also necessary to ensure that the component solder end contacts the solder paste pattern.

The self-positioning effect of the chip components at both ends is relatively large. When mounting, more than 3/4 of the width direction of the component overlaps the pad, and the two ends in the length direction overlap the corresponding pad and contact the solder paste pattern. It can be self-positioned during reflow soldering. However, if one of the ends does not overlap the pad or does not contact the solder paste pattern, it will shift or bridge during reflow soldering;

The solder balls of BGA are aligned one by one with the corresponding pads;

The maximum offset between the center of the solder ball and the center of the pad is less than 1/2 of the solder ball diameter.

3. Appropriate pressure (patch height):

If the pressure of SMT patch is too small, the solder end or pin of the component will float on the surface of the solder paste, and the solder paste will not stick to the component, which is easy to cause position shift during transfer and reflow. In addition, due to the high Z-axis height, the component will be dropped from a high place during patch, which will cause the patch position to shift.

If the pressure of SMT patch is too large, the amount of solder paste extruded will be too much, which will easily cause solder paste adhesion, and bridging will easily occur during reflow. At the same time, the patch position will shift due to sliding, and in severe cases, the components will be damaged.