There is no gold, no one is perfect”, so does PCB board. In PCB welding, due to various reasons, various defects often appear, such as virtual welding, overheating, bridging and so on. This article, We explain in detail the appearance characteristics, hazards and cause analysis of 16 common PCB soldering defects.
01
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.
Cause Analysis:
The leads of the components are not cleaned, tinned or oxidized.
The printed board is not clean, and the sprayed flux is of poor quality.
02
Solder accumulation
Appearance characteristics: The solder joint structure is loose, white and dull.
Hazard: Insufficient mechanical strength, possibly false welding.
Cause Analysis:
The solder quality is not good.
The soldering temperature is not enough.
When the solder is not solidified, the lead of the component becomes loose.
03
Too much solder
Appearance characteristics: The solder surface is convex.
Hazard: Waste solder, and may contain defects.
Reason analysis: solder withdrawal is too late.
04
Too little solder
Appearance characteristics: The soldering area is less than 80% of the pad, and the solder does not form a smooth transition surface.
Hazard: insufficient mechanical strength.
Cause Analysis:
The solder fluidity is poor or the solder is withdrawn too early.
Insufficient flux.
The welding time is too short.
05
Rosin welding
Appearance characteristics: Rosin slag is contained in the weld.
Hazard: Insufficient strength, poor continuity, and may be switched on and off.
Cause Analysis:
Too many welders or have failed.
Insufficient welding time and insufficient heating.
The surface oxide film is not removed.
06
overheat
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.
07
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 jitters before it solidifies.
08
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.
09
Asymmetry
Appearance characteristics: solder does not flow over the pad.
Harm: Insufficient strength.
Cause Analysis:
The solder has poor fluidity.
Insufficient flux or poor quality.
Insufficient heating.
10
Loose
Appearance characteristics: The wire or component lead can be moved.
Hazard: Poor or non-conduction.
Cause Analysis:
The lead moves before the solder is solidified and causes a void.
The lead is not processed well (poor or not wetted).
11
Sharpen
Appearance characteristics: sharp.
Harm: Poor appearance, easy to cause bridging.
Cause Analysis:
The flux is too little and the heating time is too long.
Improper evacuation angle of the soldering iron.
12
bridging
Appearance characteristics: adjacent wires are connected.
Hazard: Electrical short circuit.
Cause Analysis:
Too much solder.
Improper evacuation angle of the soldering iron.
13
Pinhole
Appearance features: visual inspection or low-power amplifiers can see holes.
Hazard: Insufficient strength and easy corrosion of solder joints.
Reason analysis: the gap between the lead and the pad hole is too large.
14
bubble
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 infiltration.
The welding time of the double-sided plate plugging the through hole is long, and the air in the hole expands.
15
Copper foil cocked
Appearance characteristics: The copper foil is peeled from the printed board.
Hazard: The printed board is damaged.
Reason analysis: the welding time is too long and the temperature is too high.
16
Peel off
Appearance characteristics: the solder joints peel off from the copper foil (not the copper foil and the printed board peeling off).
Hazard: Open circuit.
Reason analysis: bad metal plating on the pad.