1. As a PCB expert, I’d revise and refine the following passage to ensure clarity and coherence:
2. In circuit board processing, numerous welding defects can arise. Refer to the accompanying figure illustrating sixteen prevalent welding defects.
3. Below, you’ll find an exhaustive breakdown of these common welding defects, including their visual characteristics, associated risks, and potential causes.
1. Welding
a.) **Appearance Characteristics:** An obvious black boundary line appears between the solder and the lead of the component or the copper foil, with the solder sunken towards the boundary.
b.) **Hazards:** Impairs proper functionality.
c.) **Possible Causes:**
– Component leads are not adequately cleaned, tinned, or may be oxidized.
– The printed circuit board lacks cleanliness, and the applied flux is of inferior quality.
2. Solder Accumulation
a.) **Appearance Characteristics:** The solder joint structure appears loose, white, and dull.
b.) **Hazards:** Insufficient mechanical strength, potentially leading to false welds.
c.) **Possible Causes:**
– Poor solder quality.
– Inadequate welding temperature.
– Component lead becoming loose due to insufficient solidification of solder.
3. Too Much Solder
a.) **Appearance Characteristics:** The solder surface exhibits a convex shape.
b.) **Hazards:** Wastage of solder and potential inclusion of defects.
c.) **Possible Causes:**
– Delayed solder evacuation.
4. Too Little Solder
a.) **Appearance Characteristics:** Soldering area covers less than 80% of the pad, lacking a smooth transition surface.
b.) **Hazards:** Insufficient mechanical strength.
c.) **Possible Causes:**
– Poor solder fluidity or premature withdrawal.
– Inadequate flux.
– Short welding time.
5. Rosin Welding
a.) **Appearance Characteristics:** Rosin slag is present in the weld.
b.) **Hazards:** Reduced strength, poor continuity, and possible intermittent connections.
c.) **Possible Causes:**
– Excessive or failed attempts at welding.
– Inadequate welding time and heating.
– Failure to remove surface oxide film.
6. Overheating
a.) **Appearance Characteristics:** Solder joints appear white, lacking metallic luster, with a rough surface.
b.) **Hazards:** Increased likelihood of pad detachment and reduced strength.
c.) **Possible Causes:**
– Excessive power from the soldering iron and prolonged heating time.
7. Cold Welding
a.) **Appearance Characteristics:** Surface resembles tofu-like particles, with occasional cracks.
b.) **Hazards:** Reduced strength and poor conductivity.
c.) **Possible Causes:**
– Movement before solder solidification.
8. Poor Infiltration
a.) **Appearance Characteristics:** Contact between solder and soldering interface is too large and uneven.
b.) **Hazards:** Low strength, intermittent connectivity.
c.) **Possible Causes:**
– Inadequately cleaned weldment.
– Insufficient or poor-quality flux.
– Inadequate heating of the weldment.
2. In circuit board processing, numerous welding defects can arise. Refer to the accompanying figure illustrating sixteen prevalent welding defects.
3. Below, you’ll find an exhaustive breakdown of these common welding defects, including their visual characteristics, associated risks, and potential causes.
1. Welding
a.) **Appearance Characteristics:** An obvious black boundary line appears between the solder and the lead of the component or the copper foil, with the solder sunken towards the boundary.
b.) **Hazards:** Impairs proper functionality.
c.) **Possible Causes:**
– Component leads are not adequately cleaned, tinned, or may be oxidized.
– The printed circuit board lacks cleanliness, and the applied flux is of inferior quality.
2. Solder Accumulation
a.) **Appearance Characteristics:** The solder joint structure appears loose, white, and dull.
b.) **Hazards:** Insufficient mechanical strength, potentially leading to false welds.
c.) **Possible Causes:**
– Poor solder quality.
– Inadequate welding temperature.
– Component lead becoming loose due to insufficient solidification of solder.
3. Too Much Solder
a.) **Appearance Characteristics:** The solder surface exhibits a convex shape.
b.) **Hazards:** Wastage of solder and potential inclusion of defects.
c.) **Possible Causes:**
– Delayed solder evacuation.
4. Too Little Solder
a.) **Appearance Characteristics:** Soldering area covers less than 80% of the pad, lacking a smooth transition surface.
b.) **Hazards:** Insufficient mechanical strength.
c.) **Possible Causes:**
– Poor solder fluidity or premature withdrawal.
– Inadequate flux.
– Short welding time.
5. Rosin Welding
a.) **Appearance Characteristics:** Rosin slag is present in the weld.
b.) **Hazards:** Reduced strength, poor continuity, and possible intermittent connections.
c.) **Possible Causes:**
– Excessive or failed attempts at welding.
– Inadequate welding time and heating.
– Failure to remove surface oxide film.
6. Overheating
a.) **Appearance Characteristics:** Solder joints appear white, lacking metallic luster, with a rough surface.
b.) **Hazards:** Increased likelihood of pad detachment and reduced strength.
c.) **Possible Causes:**
– Excessive power from the soldering iron and prolonged heating time.
7. Cold Welding
a.) **Appearance Characteristics:** Surface resembles tofu-like particles, with occasional cracks.
b.) **Hazards:** Reduced strength and poor conductivity.
c.) **Possible Causes:**
– Movement before solder solidification.
8. Poor Infiltration
a.) **Appearance Characteristics:** Contact between solder and soldering interface is too large and uneven.
b.) **Hazards:** Low strength, intermittent connectivity.
c.) **Possible Causes:**
– Inadequately cleaned weldment.
– Insufficient or poor-quality flux.
– Inadequate heating of the weldment.
