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1. The opening of the green oil solder mask window leads to the green oil cover device pads, and the soldering of SMD/SMC devices is prone to false soldering of the SMD/SMC device during SMT soldering.
There is a green oil bridge between the PIN and the PIN. During the production process, the green oil exposure alignment offset directly affects the green oil cover pads. SMT will cause false welding, virtual welding, soldering and other welding during welding. bad.
2. The cover film (cover film) is attached to the offset, resulting in a large pad and a small pad. SMT soldering is prone to false soldering, virtual soldering, and tombstones at one end of the SMD/SMC device. The overall offset of the cover film causes the device to fail. The pads cause the pads of the SMD/SMC devices to be completely covered, causing the SMT to be unable to be soldered.
3. Surface contamination of SMD/SMC pads
Such as cover film overflow, gold surface exposed copper oxidation, black pads, etc., which directly affect the SMT assembly and welding, drop parts, false welding, and poor soldering of the pad. The defects are concentrated in the solder paste and the FPCB pad cannot produce the alloy layer, resulting in false soldering of the device, which seems to be soldered together, in fact, it is not soldered together.
4. Deformation of the reinforcing plate. When attaching the reinforcement board on the back of the SMD/SMC device on the FPCB, it is necessary to ensure the flatness of the board surface after attaching the reinforcement board. Generally, the steel sheet reinforcement is not easy to deform (hot pressing/cold pasting process). The cold bonding process of the reinforcing plate is prone to air bubbles during reflow soldering, resulting in defects such as false soldering and false soldering in SMT soldering. Generally, a hot pressing process is used. The following is the deformation of various reinforcing plates in the easy process.
5. The effect of different processing technology on the SMT of the reinforcing plate is also different.
in conclusion
Considering some of the above factors affecting the reliability of SMT soldering, in addition to considering important links such as process materials, process equipment, process experience, testing and quality control, attention should also be paid to the rational design of SMD/SMC pad design and FPC flexible printed circuits. The impact of some defects in the board manufacturing process on SMT processing. Only grasping the rationality of SMD/SMC pad design and avoiding the defects in the manufacturing process of FPC flexible printed circuit board is one of the key links to ensure the quality of SMT processing and welding.
Therefore, establish a technical management mechanism closely related to SMD/SMC pad design and SMT processing technology. Once it is discovered in production, soldering defects caused by unreasonable SMD/SMC pad design and defects in the FPC flexible printed circuit board manufacturing process, Should return to the R&D and design team and the process team in time to improve the design process, so as to achieve the goal of "zero defect" in the welding of SMT processed products.
