There are many common welding defects on circuit boards, as shown in the figure below. The following is a detailed description of the common welding defects, appearance characteristics, hazards and causes.
A, virtual welding
1. Appearance characteristics
There is a clear black boundary between solder and component leads or copper foil, solder to the boundary depression.
2, harm
Not working properly.
3. Cause analysis
1) the leads of components are not clean, not coated with tin or oxidized.
2) printed board is not clean, spray flux quality is not good.
Two, solder accumulation
1. Appearance characteristics
Solder joints are loose, white and dull.
2, harm
Lack of mechanical strength, may be virtual welding.
3. Cause analysis
1) poor solder quality.
2) insufficient welding temperature.
3) when the solder is not solidified, the lead of components is loose.
Too much solder
1. Appearance characteristics
Solder faces are convex.
2, harm
Waste solder and may contain defects.
3. Cause analysis
The solder left too late.
Too little solder
1. Appearance characteristics
The welding area is less than 80% of the solder pad, and the solder does not form a smooth transition surface.
2, harm
Insufficient mechanical strength.
3. Cause analysis
1) poor fluidity of solder or premature withdrawal of solder.
2) insufficient flux.
3) the welding time is too short.
Five, rosin welding
1. Appearance characteristics
There is rosin slag in the weld.
2, harm
Insufficient strength, poor conduction, may be on and off.
3. Cause analysis
1) the welder is too much or has failed.
2) insufficient welding time and insufficient heating.
3) the surface oxide film is not removed.
Six, overheating
1. Appearance characteristics
White solder joint, no metallic luster, rough surface.
2, harm
The solder pads are easy to peel off and the strength is reduced.
3. Cause analysis
Too much power of the soldering iron, too long heating time.
Seven, cold welding
1. Appearance characteristics
The surface into bean curd slaggy particles, sometimes there may be cracks.
2, harm
Low strength, poor electrical conductivity.
3. Cause analysis
The solder quivered before it solidified.
Analysis of 16 common welding defects in circuit boards
Eight, poor infiltration
1. Appearance characteristics
Solder and solder interface contact is too large, not smooth.
2, harm
Low strength, impassable or on and off.
3. Cause analysis
1) the welding parts are not clean.
2) insufficient flux or poor quality.
3) the welded parts are not heated adequately.
asymmetry
1. Appearance characteristics
The solder hasn’t flowed all over the pad.
2, harm
Insufficient intensity.
3. Cause analysis
1) poor fluidity of solder.
2) insufficient flux or poor quality.
3) insufficient heating.
Ten, loose
1. Appearance characteristics
The wire or component lead can be moved.
2, harm
Poor or no conduction.
3. Cause analysis
1) the lead wire moves before the solder is not solidified, resulting in the gap.
2) the lead is not properly handled (poor or no infiltration).
Eleven, pull the tip
1. Appearance characteristics
The tip appears.
2, harm
Poor appearance, easy to cause bridge phenomenon.
3. Cause analysis
1) too little flux and too long heating time.
2) improper exit Angle of soldering iron.
Twelve, bridge
1. Appearance characteristics
Adjacent wires connect.
2, harm
Electrical short circuit.
3. Cause analysis
1) too much soldering.
2) improper exit Angle of soldering iron.
Analysis of common defects, hazards and causes of PCB welding
Xiii. Pinholes
1. Appearance characteristics
Holes are visible on visual or low power amplifiers.
2, harm
Weak strength, welding spot easy to corrosion.
3. Cause analysis
The gap between the lead and the weld pad is too large.
14. Bubbles
1. Appearance characteristics
Lead root has spitfire solder bump, internal cavity.
2, harm
Temporarily conducted, but for a long time easy to cause poor conducted.
3. Cause analysis
1) large gap between lead wire and welding pad.
2) poor lead infiltration.
3) the welding time of blocking through hole of double panel is long, and the air inside the hole expands.
Fifteen, copper foil warped
1. Appearance characteristics
The copper foil is stripped from the printed board.
2, harm
The printed board is damaged.
3. Cause analysis
The welding time is too long and the temperature is too high.
16. Stripping
1. Appearance characteristics
Solder joints are peeled off from copper foil (not copper foil with PCB).
2, harm
Open circuit.
3. Cause analysis
Poor metal plating on the welding pad.