14 Common PCB Soldering Defects
and Their Causes Explained

　　In electronics manufacturing, the quality of a single solder joint can determine the reliability of an entire circuit board. Even the smallest defect can cause a device to fail at a critical moment, or worse, lead to an entire batch of products being scrapped. In this article, we’ll explore 14 of the most common PCB soldering defects, along with their hazards and causes.

Cold Solder Joint

Appearance：A distinct black boundary between solder and component lead or copper foil; solder appears sunken at the boundary.

Hazard: Electrical failure due to poor connectivity.

Causes:
1、Component leads are not clean, poorly tinned, or oxidized.

2、PCB surface is unclean, or poor-quality flux is used.

Solder Piling 

Appearance: Dull, white, porous solder joint.

Hazard: Weak mechanical strength; potential for cold solder joints.

Causes:
1、Poor solder quality.

2、Insufficient soldering temperature.

3、Movement of the lead before solder solidifies.

Excessive Solder 

Appearance: Solder forms a convex shape on the pad.

Hazard: Waste of solder; may hide internal defects.

Cause: Soldering iron is withdrawn too late.

Insufficient Solder 

Appearance: Solder coverage is less than 80% of the pad; no smooth transition formed.

Hazard: Inadequate mechanical strength.

Causes:

1、Poor solder fluidity or early withdrawal of soldering iron.

2、Insufficient flux.

3、Soldering time too short.

Rosin Inclusion

Appearance: Rosin residue trapped in the solder joint.

Hazard: Weak joints; possible intermittent connections.

Causes:

1、Excessive or degraded flux.

2、Insufficient heating or soldering time.

3、Oxide film not properly removed.

Overheating

Appearance: Dull, white, rough solder joint surface.

Hazard: Pad lifting and reduced mechanical strength.

Cause: Excessive soldering temperature or time.

Cold Weld

Appearance: Solder has a grainy, porous appearance, sometimes with visible cracks.

Hazard: Low strength and poor electrical conductivity.

Cause: Movement before solder has solidified.

Asymmetrical Joint

Appearance: Solder does not fully cover the pad.

Hazard: Insufficient joint strength.

Causes:
1、Poor solder flow.

2、Insufficient or poor-quality flux.

3、Inadequate heating.

Solder Spike

Appearance: Sharp pointed tip formed at the solder joint.

Hazard: Poor appearance; risk of solder bridging.

Causes:

1、Too little flux with excessive heating time.

2、Incorrect soldering iron withdrawal angle.

Solder Bridging

Appearance: Solder connects adjacent conductors unintentionally.

Hazard: Electrical short circuit.

Causes:
1、Excessive solder.

2、Incorrect soldering iron withdrawal angle.

Pinholes

Appearance: Small holes visible to the naked eye or under low magnification.

Hazard: Weak joint; susceptible to corrosion.

Cause: Excessive gap between lead and plated through-hole.

Solder Void

Appearance: Volcano-shaped solder rise at lead root; internal cavities.

Hazard: Initially conductive but may fail over time.

Causes:

1、Large gap between lead and through-hole.

2、Poor wetting of the lead.

3、In double-sided PCBs, long heating times cause air expansion in vias.

Copper Foil Lifting

Appearance: Copper foil detaches from the PCB surface.

Hazard: PCB damage.

Cause: Excessive temperature or soldering time.

Delamination

Appearance: Solder pad detaches from copper foil.

Hazard: Open circuit.

Cause: Poor plating adhesion on the pad.

　　A solder joint may be small, but it is the cornerstone of stable device performance. Understanding and identifying these common defects not only helps improve manufacturing quality but also allows engineers to mitigate risks early during design and inspection. Which soldering issues have you faced in your work? Share your experiences in the comments.