Analysis of common defects, hazards and causes of circuit board welding

tiankai001

Analysis of common defects, hazards and causes of circuit board welding [Copy link]

This post was last edited by tiankai001 on 2019-1-2 10:01 There are many common soldering defects on circuit boards. The following figure shows the sixteen common soldering defects.

The following is a detailed description of common soldering defects, appearance characteristics, hazards, and cause analysis. 1. Cold solder joint

1. Appearance characteristics

There is an obvious black boundary between the solder and the component lead or the copper foil, and the solder is sunken towards the boundary.

2. Hazards

Cannot work normally.

3. Cause analysis

1) Component leads are not cleaned well, are not tinned well or are oxidized. 2) The printed circuit board is not cleaned well and the quality of the sprayed flux is poor.

2. Solder accumulation

1. Appearance characteristics

The solder joint structure is loose, white and dull.

2. Hazards

Insufficient mechanical strength may cause cold soldering.

3. Cause Analysis

1) Poor quality of solder. 2) The soldering temperature is not high enough. 3) When the solder is not solidified, the leads of the components are loose.

3. Too much solder

1. Appearance characteristics

The solder surface is convex. 2. Hazards: Waste of solder and possible concealment of defects. 3. Cause Analysis: Solder withdrawal is too late.

Fourth, too little solder

1. Appearance characteristics

The soldering area is less than 80% of the pad, and the solder has not formed a smooth transition surface.

2. Hazards

Insufficient mechanical strength.

3. Cause Analysis

1) Poor solder fluidity or premature solder withdrawal.

2) Insufficient flux. 3) The welding time is too short.

5. Rosin welding

1. Appearance characteristics

There is rosin slag in the weld.

2. Hazards

Insufficient strength, poor conduction, and may be intermittent.

3. Cause analysis

1) Too many welding machines or they are out of service.

2) Insufficient welding time and insufficient heating.

3) The surface oxide film has not been removed.

tiankai001

This post was last edited by tiankai001 on 2019-1-2 10:03 VI. Overheating 1. Appearance characteristics The solder joint is whitish, has no metallic luster, and has a rough surface. 2. Hazards The solder pad is easy to peel off and the strength is reduced. 3. Cause analysis The soldering iron power is too large and the heating time is too long. VII. Cold welding 1. Appearance characteristics The surface is in the shape of tofu dregs, and sometimes there may be cracks. 2. Hazards Low strength and poor electrical conductivity. 3. Cause analysis The solder shakes before solidification. VIII. Poor wetting 1. Appearance characteristics The interface between the solder and the weldment is too large and not smooth. 2. Hazards Low strength, no connection or intermittent connection. 3. Cause analysis 1) The weldment is not cleaned properly. 2) Insufficient or poor quality flux. 3) The weldment is not heated sufficiently. IX. Asymmetry 1. Appearance characteristics The solder does not flow all over the pad. 2. Hazards Insufficient strength. 3. Cause analysis 1) The solder has poor fluidity. 2) Insufficient or poor quality flux. 3) Insufficient heating. X. Looseness 1. Appearance characteristics The wire or component lead can be moved. 2. Hazards Poor or no conduction. 3. Cause analysis 1) The lead moves before the solder solidifies, causing gaps. 2) The lead is not handled well (poor wetting or no wetting).

tiankai001

This post was last edited by tiankai001 on 2019-1-2 10:05 XI. Pull tip 1. Appearance characteristics The tip appears. 2. Hazards Poor appearance, easy to cause bridging phenomenon. 3. Cause analysis 1) Too little flux and too long heating time. 2) Improper soldering iron withdrawal angle. 12. Bridging 1. Appearance characteristics Adjacent wires are connected. 2. Hazards Electrical short circuit. 3. Cause analysis 1) Too much solder. 2) Improper soldering iron withdrawal angle. 13. Pinholes 1. Appearance characteristics Hole can be seen by visual inspection or low-power magnifier. 2. Hazards Insufficient strength, solder joints are prone to corrosion. 3. Cause Analysis The gap between the lead and the pad hole is too large. 14. Bubbles 1. Appearance characteristics There is a flame-like solder bulge at the root of the lead, and there is a cavity inside. 2. Hazards It is temporarily conductive, but it is easy to cause poor conduction for a long time. 3. Cause Analysis 1) The gap between the lead and the pad hole is large. 2) The lead is not wetted well. 3) The double-sided board plugging through-hole welding time is long, and the air in the hole expands. 15. Copper foil lift 1. Appearance characteristics The copper foil peels off from the printed board. 2. Hazards The printed board is damaged. 3. Cause analysis The welding time is too long and the temperature is too high. 16. Peeling 1. Appearance characteristics The solder joint peels off from the copper foil (not the copper foil and the printed board). 2. Hazards Broken circuit. 3. Cause Analysis: Poor metal coating on the pad.