What are the hazards of 16 PCB soldering defects

2021-10-23

Author：Downs

The common PCB soldering defects, appearance characteristics, hazards, and cause analysis will be explained in detail.

Welding

Appearance characteristics: There is a clear black boundary between the solder and the lead of the component or with the copper foil, and the solder is recessed toward the boundary. Harm: Not working properly. Reason analysis: the lead of the component is not cleaned, not plated with tin or oxidized. The PCB printed board is not clean, and the sprayed flux is of poor quality. Appearance characteristics of solder accumulation: loose solder joint structure, white, matt. Hazard: insufficient mechanical strength, possibly false soldering. Reason analysis: the quality of solder is not good. The soldering temperature is not enough. When the solder is not solidified, the lead of the component becomes loose. Excessive solder appearance characteristics: the solder surface is convex. Hazard: Waste solder, and may contain defects. Analysis of the cause: too late solder withdrawal appearance characteristics: soldering area is less than 80% of the pad, and the solder does not form a smooth transition surface. Hazard: insufficient mechanical strength. Reason analysis: poor solder fluidity or solder withdrawal prematurely. Insufficient flux. The welding time is too short. Appearance characteristics of rosin welding: There is rosin slag in the weld. Hazard: Insufficient strength, poor continuity, and may be switched on and off. Reason analysis: too many welders or have failed. Insufficient welding time and insufficient heating. The surface oxide film is not removed. Overheating appearance characteristics: white solder joints, no metallic luster, rough surface.

Hazard: The pad is easy to peel off and the strength is reduced.

Reason analysis: the power of the soldering iron is too large, and the heating time is too long.

Cold welding

Appearance characteristics: the surface becomes tofu-like particles, and sometimes there may be cracks

Harm: Low strength and poor conductivity.

Reason analysis: the solder shakes before it solidifies.

pcb board

Poor infiltration

Appearance characteristics: The contact between the solder and the weldment is too large and not smooth.

Hazard: Low strength, unavailable or intermittently on and off.

Cause Analysis:

The weldment is not cleaned up.

Insufficient flux or poor quality.

The weldment is not heated sufficiently.

Asymmetry

Appearance characteristics: The solder does not flow over the pad.

Harm: Insufficient strength.

Cause Analysis:

The solder has poor fluidity.

Insufficient flux or poor quality.

Insufficient heating.

Loose

Appearance features: PCB wire or PCB component leads can be moved.

Hazard: Poor or non-conduction.

Cause Analysis

The lead moves before the solder is solidified, causing voids.

The lead is not processed well (poor or not wetted).

Sharpen

Appearance characteristics: sharp. Harm: Poor appearance, easy to cause bridging phenomenon.

Reason analysis: too little flux and too long heating time. Improper evacuation angle of soldering iron.

Features of bridge appearance: Adjacent wires are connected. Hazard: Electrical short circuit. Reason analysis: too much solder. Improper evacuation angle of soldering iron.

Pinhole

Appearance features: visual inspection or low-power amplifiers can see holes.

Hazard: Insufficient strength, solder joints are easy to corrode.

Reason analysis: the gap between the lead and the pad hole is too large.

Appearance characteristics: there is a fire-breathing solder bulge at the root of the lead, and a cavity is hidden inside.

Hazard: Temporary conduction, but it is easy to cause poor conduction for a long time.

Cause Analysis:

There is a large gap between the lead and the pad hole.

Poor lead in double-sided PCB filtration.

board plugging through-hole welding takes a long time, and the air in the hole expands.

Copper foil cocked

Appearance characteristics: the copper foil is peeled off from the PCB printed board