In SMT manufacturers, the size of 0201 in the mounting accuracy is very small. Because the components are relatively small, light weight, low fault tolerance and high quality requirements for suction nozzle and solder paste printing. Therefore, monument erection and displacement are easy to occur during reflow welding in SMT patch. In particular, the welding of components is relatively intensive, which is more likely to cause quality problems for PCBA processed products.
To solve this problem, the best solution is to take into account all objective conditions that may lead to excessive and unbalanced solder paste printing, such as asymmetric characters and solder resist layer. Therefore, it is recommended that:
(1) Cancel silk screen frame and characters.
(2) 0.1mm thick steel mesh is adopted.
(3) The thickness of steel mesh within 2.5mm around shall not exceed 0.1mm.
(4) Accurate assembly.
In addition, there is a common problem in the welding of chip capacitors, BGA and other components, that is, fear of the role of "stress", especially the role of multiple stress (such as installing multiple screws) and over stress (such as falling). Therefore, they can be classified as stress sensitive components.
In the process of PCBA welding, additional stress may be generated in the links such as single hand plate holding, plug-in pressing, plate splicing and plate splitting, manual crimping, installation screw, ICT test, FA test and turnover transportation, which may cause the cracking or "fracture" of the solder joints of these components.