What are the reasons for PCB pads to fall off?
1. PCB circuit board product quality problems.
The substrate of PCB is copper clad laminate. If the resin adhesive adhesion between the copper foil of the copper clad laminate and the epoxy resin is insufficient, the copper foil is slightly heated or under mechanical external force. It is easier to separate from the epoxy resin, resulting in pads and copper foil falling off. This adhesion problem may be caused by improper selection of raw materials, lax production process control or material aging.
2. The influence of PCB storage conditions.
Due to weather factors or long-term storage in a humid environment, PCB circuit boards may have too high a moisture content. In order to ensure the ideal welding effect, the heat taken away by the evaporation of water needs to be considered during patch welding, which requires extending the temperature and time of welding. However, this welding condition may cause stratification between the copper foil and the epoxy resin of the PCB circuit board. In addition, high humidity and temperature fluctuations can also cause oxidation problems on the PCB surface. At the same time, chemical corrosion (such as acid and alkali) will also affect the strength of the pad.
3. Electric soldering iron welding phenomenon.
Usually, the adhesion of PCB circuit boards can meet the normal welding, and the pad will not fall off. However, electronic products are usually likely to be repaired. The repair is usually repaired by soldering with a soldering iron. Given that the local high temperature of the soldering iron often reaches about 300-400 degrees, the temperature of the pad is too high for a moment, and the resin glue under the copper foil of the pad falls off due to the high temperature, resulting in pad falling off. When the soldering iron is disassembled and assembled, it is also easy to be accompanied by the physical force of the soldering iron head on the pad, which is also the cause of the pad falling off. Welding process problems: Inappropriate welding temperature or time, improper welding tools or methods will cause the pad to be not firmly bonded to the substrate.
4. Pad design defects.
The pad design is unreasonable, the size is too small or the shape is not suitable for welding. Improper pad position design leads to stress concentration.
To reduce the phenomenon of PCB pad falling off, there are several coping strategies:
1. Optimize the welding process:
Determine the appropriate welding temperature and time, and strictly follow the process flow.
Regularly train operators to improve welding skills.
2. Choose high-quality materials:
Purchase high-quality PCB substrates and welding materials to ensure that they meet industry standards.
Check material inventory regularly to avoid using expired or inferior materials.
3. Improve design:
Use reasonable pad design to ensure that the pad size and shape are suitable for welding requirements.
Perform stress analysis in the design stage to optimize the pad position.
4. Control environmental conditions and use moisture-proof packaging:
Control temperature and humidity in the production environment to prevent materials from getting damp or oxidized.
Monitor environmental conditions regularly to ensure a stable production environment.
Use vacuum packaging or add desiccant to reduce the risk of moisture absorption of PCB boards during transportation and storage.
5. Enhance mechanical strength:
When installing components, ensure the correct installation method to avoid excessive mechanical stress.
For high-power or sensitive components, support or protection measures can be added.
6. Use suitable welding materials:
Choose suitable solder and flux to ensure their quality and applicability.
Perform quality inspection on welding materials to ensure compliance with standards.
7. Strict process control:
Establish a complete production monitoring system and conduct quality inspections regularly.
Optimize the production process to ensure that each link meets the quality standards.
Through the above cause analysis and response strategies, the risk of PCB pad falling off can be effectively reduced, and the overall reliability and service life of the PCB can be improved.
