1. Excessive pressure is not conducive to heat conduction, and will only lead to oxidation of the soldering iron tip, pad dents and warpage.

2. Incorrect size, shape and length of the soldering iron tip will affect the heat capacity and contact area.

3. Too high temperature and too long time will make the flux ineffective and increase the thickness of the intermetallic compound.

4. The tin wire is not placed correctly and cannot form a thermal bridge. Solder transfer does not transfer heat efficiently.

5. Improper use of flux, excessive use of flux can cause corrosion and electromigration

6. Unnecessary modifications and rework will increase intermetallic compounds and affect the strength of the solder joints.

7. The transfer welding method will volatilize the flux in advance and cannot be used for the welding of through-hole parts. Welded SMD can be used.