1. **Various soldering problems**
Signs include blast holes in cold or tin solder joints.
**Introspection method:** Regularly analyze the holes before and after soldering to identify the center of copper stress. Additionally, conduct incoming inspections of raw materials.
2. **Reasons for issues:**
Blast holes or cold solder joints often appear post-soldering. Typically, poor copper plating leads to shrinkage during soldering, creating cavities or blast holes in metallized walls. If this occurs during wet processing, absorbed volatiles can become trapped under coatings, causing spouts or blast holes when expelled during dip soldering.
3. **Approach:**
Aim to eliminate copper stress. The laminate’s shrinkage in the z-axis or thickness direction often relates to the material properties, which can promote the fracture of metallized holes.
1. **Engage with laminate manufacturers to obtain recommendations for data that minimize z-axis shrinkage.**
2. **Next, address the issue of bonding strength.**
3. **Observation: During the dip soldering process, pads and wires become detached.**
4. **Self-reflection method: During incoming inspections, halt full testing and closely monitor all wet processing stages.**
5. **Root causes:**
1. The detachment of pads or wires during processing can stem from electroplating solutions, solvent etching, or copper stress associated with electroplating operations.
2. Punching, drilling, or perforation can cause partial detachment of pads, which becomes evident during the hole metallization process.
3. In wave soldering or manual soldering, detachment of pads or wires typically results from improper soldering techniques or excessive temperatures. Additionally, poor laminate bonding or low thermal peel strength may contribute to the detachment of pads or wires.
4. Sometimes, the design and layout of multi-layer PCBs can lead to detachment of pads or wires at opposing centers.
5. During soldering, retained heat from components can cause pad detachment.
6. **Proposed solutions:**
1. Provide the laminate manufacturer with a comprehensive list of solvents and solutions used, along with the processing times and temperatures for each step. Analyze whether the electroplating process contributes to copper stress and excessive thermal shock.
2. Strictly adhere to the recommended machining methods. Regular analysis of metallized holes can help control this issue.
3. Most pad or wire detachment occurs due to insufficient guidelines for all operators. Effective temperature monitoring of the solder bath or extending the dwell time in the solder bath can help. In manual soldering repairs, pad detachment may result from improper wattage usage or insufficient professional training. Some laminate manufacturers now produce laminates with high peel strength at low temperatures for challenging soldering applications.
4. If the PCB design leads to detachment at opposing centers, the design must be revised. This often occurs at the center of thick copper foils or at wire corners. Long wires may also experience this issue due to differing coefficients of thermal contraction.
5. Consider removing heavy components from the PCB or installing them after the dip soldering process. Typically, a low-wattage soldering iron should be used for careful soldering, as it shortens the duration that the substrate material is exposed to heat compared to component dip soldering.
7. **Issue of excessive size changes:**
8. **Observation: The substrate size is out of tolerance or fails to align after processing or soldering.**
9. **Self-reflection method: Implement thorough quality control throughout the processing stages.**
10. **Potential causes:**
1. Insufficient attention to the orientation of paper-based materials leads to shrinkage in the forward direction being approximately half that in the horizontal direction. Furthermore, the substrate may not return to its original size upon cooling.
2. If some stress within the laminate remains unreleased, it may cause irregular dimensional changes during processing.
11. **Proposed solutions:**
1. Instruct all users to cut the board perpendicular to the grain structure. If size changes exceed acceptable limits, consider switching substrates.
2. Consult the PCB laminate manufacturer for advice on relieving material stress prior to processing.
