Common Soldering Issues

 

Common Soldering Issues

Following are several soldering issues that may occur during solder training or production operations.

 

solder issue

Pad Contamination

Cause: Inadequate removal/cleaning of flux residue after reflow.

(ref: EPEC)

Correction: RMA flux residues must be removed from the assembly. On some assemblies or locations, no-clean fluxes must also be removed.

solder issue


Excess Solder

Cause: Excess solder was applied to the connection during hand soldering.

ref: adafruit.com

Correction: Remove excess solder using fluxed solder wick and soldering iron or a solder sucker.

solder issue

Cold Solder

Cause: Insufficient heating of the solder connection.

(ref: quoroa.com)

Correction: Flux the connection on both sides of the PCB. Contact both the pin and pad with a soldering iron and reflow. Add solder as necessary.

solder issue

Poor Wetting

Cause: Surface contamination on the soldered surface.

(ref: visioneng.com)

Correction: Clean both sides of the PCB with PCB cleaner and brush. Flux both sides and reflow from the bottom side. Add solder as required.

 

solder issue

Solder Tear

Cause: During solder solidification, solder may separate at the grain boundary as it contracts. More common in lead-free solders.

(ref: ett.bme.hu)

Correction: IPC-610G states there is no defect associated with this anomaly provided the connection meets all other acceptance criteria.

solder issue

Poor Wetting

Cause: Poor solder wetting on the component or insufficient solder volume.

(ref: visioneng.com)

Correction: Clean the component and both ends with PCB cleaner and brush. For resistors, flux and reflow each end. Add solder as necessary. For chip caps, use hot air reflow.

solder issue

Solder Bridge (Short)

Cause: Excessive solder, or excessive pad size vs. pad gap.

(ref: adafruit.com)

Correction: Clean both sides of the PCB with PCB cleaner and brush. Flux both sides. Use solder wick and soldering iron or solder sucker to remove excess solder from the bottom side. Clean both sides.

solder issue


Insufficient Solder

Cause: Insufficient solder application during hand soldering.

(ref: autodesk.com)

Correction: IPC J-STD-001G specifies minimum solder fillet height on 1, 2, 3 and 5-sided SMT chip components for Class 1, 2, and 3 applications.

 

solder issue

Chip Component Side Overhang "A"

Cause: Incorrect side placement of the chip component on its mounting pads.

(ref: emerald.com)

Correction: IPC-610G specifies Maximum Side Overhang of 50%(W) for Classes 1 and 2 and 25%(W) for Class 3 chip components.

solder issue

Solder Non-Wetting

Cause: Insufficient heat applied to lead during hand soldering reflow.

(ref: discovercircuits.com)
solder issue

Solder Short

Cause: Application of excess solder during hand soldering.

(ref: autodesk.com)

Correction: Flux the connection and use a soldering iron to draw off the excess solder. Or, remove the excess solder using solder wick and soldering iron.

solder issue

Insufficient Fillet Height

Cause: “Operator error” in installing the component onto the PCB.

(ref: autodesk.com)

 

solder issue

Cold Solder (Solder Paste)

Cause: Incomplete reflow (melting) of solder paste balls during the reflow cycle.

(ref: workmanship.nasa.gov)

Correction: Flux the lead, pad, and topside. Reflow lead and pad by concurrent contact with the soldering iron.

solder issue

Insufficient Wetting

Cause: Poor circumferential wetting of the pad. Poor wetting of the lead barrel.

(ref: adafruit.com)

solder issue


Tombstoned Component

Cause: Imbalance of solder joint surface tension in molten solder causes the “stronger” joint (right side) to lift the component up off the board, creating the “tombstone.”

(ref: resources.ocb.cadence.com)

Correction: Correct this defect by fluxing and reflowing the chip component using hot air or thermal tweezers (not on chip caps). Or, alternate reflow of chip terminations via soldering iron.

solder issue

Chip Component End Overlap

Cause: Misplacement of the chip component end placement on its mounting pads.

(ref: EPEC)

Correction: J-001G requires “Minimum End Overlap” for Classes 1 and 2, and 25% R for Class 3 where R = Termination Length.