Every day has learned a little of PCB and I believe I can become more and more professional in my work. Today, I want to introduce 16 kinds of PCB weld defects from appearance characteristics, hazards, causes.
Appearance characteristics: there is an obvious black boundary between solder and component lead or copper foil, and the solder is concave to the boundary
Hazards: cannot work properly
Causes: 1) the lead wires of components are not well cleaned, not well tinned or oxidized.
2) PCB is not clean, and the quality of flux sprayed is not good
2. Solder accumulation
Appearance characteristics: Solder joints are loose, white and dull.
Hazards: mechanical strength is insufficient, may virtual welding
Causes: 1) poor solder quality.2) insufficient welding temperature.3) when the solder is not solidified, the lead of the component becomes loose.
3.Too much solder
Appearance characteristics: The solder face is convex
Hazards: Waste solder and may contain defects
Causes: solder withdrawal is so late
4. Too littler solder
Appearance characteristics: The welding area is less than 80% of the welding pad, and the solder does not form a smooth transition surface
Hazards: mechanical strength is insufficient,
Causes: 1) poor solder fluidity or premature solder withdrawal. 2) insufficient flux.3) welding time is too short.
5. Rosin welding
Appearance characteristics: There is rosin residue in the weld
Hazards: the harm intensity is insufficient, the conduction is bad, possibly when on and off
Causes:1) excessive welding machine or failure.2) insufficient welding time and heating.3) surface oxide film is not removed.
Appearance characteristics: The solder joint is white, without metallic luster, the surface is rough.
Hazards: It is easy to peel off the welding pad and reduce the strength
Causes: he soldering iron is too powerful and the heating time is too long
7. cold welding
Appearance characteristics: the surface into tofu slag particles, sometimes may have cracks
Hazards: Low trength and poor electrical conductivity
Causes: the solder dithers before solidification.
8. Infiltrating the bad
Appearance characteristics: the interface between solder and welding too large, not smooth
Hazards: Low intensity, impassable or intermittent
Causes: 1) welding parts are not cleaned 2) insufficient flux or poor quality.3) welding parts are not fully heated.
Appearance characteristics: the solder plate is not full
Hazards: Insufficient harm intensity
Causes:1) poor solder fluidity.2) insufficient flux or poor quality.3) insufficient heating.
Appearance characteristics: the lead wires or components can be moved
Hazards: bad or don’t conduction
Causes: 1) lead movement causes void before solder solidification.2) lead is not properly handled (poor or not infiltrated)
11. Solder projection
Appearance characteristics: appear cusp
Hazards: Bad appearance, easy to cause bridging
Causes: 1) too little flux and too long heating time.2) improper evacuation Angle of the soldering iron
12. Bridge connection
Appearance characteristics: Adjacent wire connection
Hazards: Electrical short circuit
Causes: 1) excessive solder. 2) improper evacuation Angle of the soldering iron
Appearance characteristics: Holes are visible in visual or low power amplifiers
Hazards: Insufficient strength and easy corrosion of solder joints
Causes: the gap between the lead wire and the hole of the welding pad is too large.
Appearance characteristics: the root of the lead wire has spitfire solder uplift and internal cavity
Hazards: Temporary conduction, but it is easy to cause bad conduction for a long time
Causes: 1) large gap between lead and welding pad hole.2) poor lead infiltration.3) double panel plugging through hole takes a long time to weld, and the air inside the hole expands.
15. Copper foil up
Appearance characteristics: copper foil from the printed board stripping
Hazards: The pcb has been damaged
Causes: the welding time is too long and the temperature is too high.
Appearance characteristics: the solder from the copper foil peeling (not copper foil and PCB stripping)
Hazards: circuit breaker
Causes: poor metal coating on the welding pad.