What Are The Common Mistakes in Manual Soldering?

Introduction

In SMT production line, manual soldering, board repair, and rework are indispensable processes.

As SMT technology continues to advance, not only have components become increasingly smaller, but new types of packaged components have emerged, along with requirements for lead-free and VOC-free manufacturing. These developments have not only increased the difficulty of assembly but also raised the complexity of rework operations. For high-density, BGA, CSP, QN, and other new packaging types of components, how to perform rework, how to improve rework success rates, and how to ensure rework quality and reliability are also critical concerns in the SMT industry. 

We will analyze common incorrect operations in manual soldering to help you avoid these issues in future soldering processes:

1. Excessive pressure does not aid heat conduction but only causes the soldering iron tip to oxidize, create indentations, and lift the pad.
2. Incorrect soldering iron tip size, shape, or length affects thermal capacity and contact area.
3. Excessively high temperatures and prolonged exposure times cause flux to degrade and increase the thickness of intermetallic compounds.
4. Improper placement of solder wire prevents the formation of a thermal bridge, hindering effective heat transfer.
5. Inappropriate use of flux, with excessive flux leading to corrosion and electromigration. 
6. Unnecessary modifications and rework increase intermetallic compounds, compromising joint strength.
7. Transfer welding techniques cause flux to evaporate prematurely, making them unsuitable for through-hole component welding; they can be used for SMD welding.
   The transfer welding method involves first melting a small amount of solder on the solder wire using the soldering iron tip, then using the soldering iron tip to perform the weld. This method is a traditional manual welding technique but is incorrect. Since the soldering iron tip reaches high temperatures, melting the solder causes the flux in the solder wire to evaporate prematurely before welding, resulting in poor solder joint quality due to the absence of flux assistance during welding.

Conclusion

Manual soldering is an important process in daily SMD assembly. Many customers' products are not adequately designed to account for the processing workflow differences between SMD components and through-hole components, including variations in reflow oven soldering temperature versus wave soldering machine temperature. This can lead to sensitivity issues regarding temperature tolerance for through-hole and SMD components, or timing constraints for material availability. Additionally, certain irregularly shaped components may also require manual soldering. When evaluating SMT manufacturing facilities, customers typically also assess the actual production capacity of DIP insertion lines and the adequacy of manual soldering capabilities.

Quick facts about NeoDen

1. Established in 2010, 200 + employees, 27000+ Sq.m. factory.
2. NeoDen Products:Different Series PnP machines, NeoDen YY1, NeoDen4 ,NeoDen5, NeoDen K1830, NeoDen9, NeoDen N10P. Reflow Oven IN Series, as well as complete SMT Line includes all necessary SMT equipment.
3. Successful 10000+ customers across the globe.
4. 40+ Global Agents covered in Asia, Europe, America, Oceania and Africa.
5. R&D Center: 3 R&D departments with 25+ professional R&D engineers.
6. Listed with CE and got 70+ patents.
7. 30+ quality control and technical support engineers, 15+ senior international sales, for timely customer responding within 8 hours, and professional solutions providing within 24 hours.