6-9 FQA 

1，Fluxes poor contact with the bottom surface; the angle of the bottom surface and the solder is improper. 

2，The ratio of flux to solder is too high or too low. 

3，Speed of belt conveyer is too fast or too slow. The standard speed should be around 1.2-1.8m/minute. If the speed of belt conveyer is 

too fast, soldering joints may be lustous and pointed. If it is too slow, soldering joints can be undesirably stubbed. 

4，Too much anti-oxidation oil in the soldering furnace or oil degeneration.

5，Preheating temperature is too high or too low. The standard temperature before soldering should be in the range of 75~100℃(Adjusted according to different situation)。 

6，Operating temperature is too high or too low. The standard temperature is about 245-255℃

7，Unstable soldering furnace wave. 

8，Impurity of the solder in the soldering furnace. 

9，Improper direction and array of components's base pins

10，Wrong treatment of PCB and leading wires. 

Chart of Common Soldering Joints Problems