Sixteen Common Welding Defects in Circuit Board Processing (Part 1)

There are many common welding defects in circuit board processing. The following figure shows sixteen common welding defects.

The following is a detailed description of common welding defects, appearance characteristics, hazards, and possible causes.

1. Welding

a.) Appearance Characteristics: There is an obvious black boundary line between the solder and the lead of the component or the copper foil, and the solder is sunken toward the boundary.

b.) Hazards: Can not work properly.

c.) Possible Causes:

–The component leads are not cleaned, tinned or oxidized.

–The printed circuit board is not clean, and the sprayed flux is of poor quality.

2. Solder accumulation

a.) Appearance Characteristic: The solder joint structure is loose, white and dull.

b.) Hazards: Insufficient mechanical strength may cause false welding.

c.) Possible Causes:

–The solder quality is not good.

–The welding temperature is not enough.

— When the solder is not solidified, the lead of the component becomes loose.

3. Too Much Solder

a.) Appearance Characteristics: The solder surface is convex.

b.) Hazards: Waste solder and may contain defects.

c.) Possible Causes:

–The solder evacuation is too late.

4. Too Little Solder

a.) Appearance Characteristics:  The soldering area is less than 80% of the pad, and the solder does not form a smooth transition surface.

b.) Hazards: Insufficient mechanical strength.

c.) Possible Causes:

— The solder fluidity is poor or the solder is withdrawn too early.

— Insufficient flux.

— The welding time is too short.

5. Rosin Welding

a.) Appearance Characteristics: Rosin slag is contained in the weld.

b.) Hazards: Insufficient strength, poor continuity, and possibly off and on.

c.) Possible Causes:

— Too many welders or have failed.
— Insufficient welding time and insufficient heating.
— The surface oxide film is not removed.

6. Overheating

a.) Appearance Characteristics:  The solder joints are white, without metallic luster, and the surface is rough.

b.) Hazards: The pad is easy to peel off and the strength is reduced.

c.) Possible Causes:

-The power of the soldering iron is too large and the heating time is too long.

7. Cold Welding

a.) Appearance Characteristics:  The surface becomes tofu-like particles, and sometimes there may be cracks.

b.) Hazards:  The strength is low and the conductivity is not good.

c.) Possible Causes:

–There is shaking before the solder has solidified.

8. Poor Infiltration

a.) Appearance Characteristics:  The contact between the solder and the soldering interface is too large and not smooth.

b.) Hazards:  The intensity is low, and it is blocked or on and off from time to time.

c.) Possible Causes:

— The weldment is not cleaned up.

— Insufficient flux or poor quality.

— The weldment is not fully heated.