Principle Of Solder Tip Formation (Spiking) in Automatic Soldering Machines

I. Causes of Solder Tip (Spike) Formation

During the soldering process, molten solder often accumulates around component leads. When excessive solder is present, it tends to form a "solder tip" as it cools and solidifies. Reheating may remove the spike, but if the PCB surface is poor or component holes are too large, solder will flow into the hole and solidify under gravity, forming icicle-like solder spikes.

Common soldering defects in automatic soldering include insufficient solder, cold joints, bridging, rough solder surfaces, solder accumulation, and solder tip formation. For the "spiking" issue, careful observation and root cause analysis are necessary to implement effective countermeasures.

Excess solder does not improve conductivity; instead, it reduces joint strength. One major cause is an improper soldering angle. The recommended angle is around 45°, which allows molten solder to separate smoothly under gravity, forming a thinner and smoother solder joint.

When soldering temperature is too low or the soldering time too short, molten solder may solidify before fully flowing, resulting in spikes. Insufficient preheating temperature can also prevent flux from fully evaporating, causing poor solder wetting and excessive residue. Increasing preheat temperature appropriately can improve overall soldering quality.

II. Methods to Eliminate Solder Spiking and Bridging During Wire Soldering

Related to soldering iron power

Different solder wires require different temperatures based on their tin content. Using a low-power iron with low-tin solder wire may result in insufficient heat, causing the solder to remain semi-molten and prone to spiking. Choose a soldering iron with power suitable for the solder wire type.

Related to solder wire composition

Poor solder joint formation may be due to low tin purity or weak flux activity. However, solderability mainly depends on flux activity rather than tin content.

Related to flux activity

Highly active flux provides better wetting, dehydration, and electrical stability. Using solder wire with high flux activity can reduce spiking and bridging, though it may produce more smoke during soldering.

Related to soldered material

The solderability and oxidation level of the base material greatly affect solder wetting and spiking. Selecting proper flux types and concentrations for different materials can enhance wetting performance and minimize solder tip formation.

III. Conclusion

Solder tip formation in automatic soldering machines is mainly caused by factors such as temperature, soldering time, angle, flux activity, and material characteristics. By properly controlling temperature parameters, adjusting soldering angles, and selecting suitable flux, solder spiking defects can be significantly reduced - improving both the reliability and appearance of solder joints.