Mounted components technics requirements. Mounted components shall be accurately placed one by one on the designated position of printed circuit board in accordance with the assembly board assembly drawing and the detailed list requirements.
1. Mounting technics requirements. The type, model, nominal value and polarity of each component of the component on the board must conform to the requirements of the product assembly drawing and the detailed list.
The mounted components must be intact.
The soldered end of the mounted component or the lead is not less than 1/2 thickness immersed in the solder paste. For general components, the extrusion amount of solder paste should be less than 0.2mm during smt process. For fine pitch components, the extrusion amount of solder paste should be less than 0.1mm.
The solder terminals or pins of the component should be aligned and centered with the land pattern. Due to the self-alignment effect of reflow soldering, certain deviations are allowed when mounting components. The specific deviation range of various components can be found in the relevant IPC standards.
2 .The three elements to PCB board mounting quality.
a. The components are correct. It is required that the type, model, nominal value and polarity of each component number component should conform to the assembly drawing and detailed list requirements of the product, and the wrong position cannot be placed.
b. The position is accurate. The soldering end or pins of the components are aligned and centered as much as possible on the land pattern, and the soldering end of the components are in contact with the solder paste pattern.
c. Proper pressure . The placement pressure is equivalent to the Z-axis height of the nozzle, and the high Z-axis height is equivalent to a small placement pressure, and the low Z-axis height is equivalent to a large placement pressure. If the height of the B-axis is too high, the solder joints or pins of the components are not pressed into solder paste, floating on the surface of the solder paste, the solder paste cannot stick to the components, and positional movement is likely to occur during transfer and reflow soldering.
In addition, the Z-axis height is too high, so that the components are free to fall from the height during smt process, which may cause the placement position to shift. On the other hand, if the height of the B-axis is too low, the amount of solder paste is too much, which is likely to cause adhesion of the solder paste. Bridging connection is likely to occur during reflow soldering. At the same time, the position of the placement is shifted due to the sliding of the alloy particles in the solder paste. It can also damage components. Therefore, the Z-axis height of the nozzle is required to be proper during smt process.