Fixing tombstoned 0603 and 0805 parts
Tombstoning is a reflow defect that hand-soldering inherits: one termination melted before the other and the resulting surface-tension imbalance lifted the free end. The repair is not to press the part down - it is to equalise the two joints before the alloy freezes.
Procedure
- 1
Identify which termination is the frozen, standing one - the lifted end is the one whose joint failed to wet, not necessarily the one that melted first.
- 2
Flux both joints generously with ROL0, working the pen under the lifted termination where possible.
- 3
Melt the standing joint for half a second with a 0.8 mm conical tip at 310 degrees C.
- 4
Immediately draw the tip across to the other joint and hold for one second, adding a touch of 0.3 mm wire if starved.
- 5
Wait three seconds for the alloy to freeze undisturbed, then inspect at 20x for a fillet on both ends and zero rotation.
Workshop notes
Why pressing does not work
Pushing a tombstoned chip down with tweezers while the solder is liquid simply embeds the termination in a blob that will re-lift as soon as the alloy solidifies. The imbalance has to be removed: the joint that froze first must be re-melted slightly before the second joint solidifies, so both fillets pull in opposite directions with equal force and cancel out.
The two-iron equalisation method
With a single iron: flux both joints generously, melt the standing (frozen) joint for half a second, then immediately draw the tip across to the other joint and hold for one second. The first joint re-melts under its own residual heat while the second is wetted, and the chip drops flat within about 300 ms. With two irons it is easier: apply both tips simultaneously for one second, lift one, then the other half a second later. Cap total contact at 2.5 seconds per joint pair.
Preventing the next one
The most common cause in hand assembly is unequal pre-tinning: a pad with 0.2 mm of solder against a pad with 0.05 mm will always tombstone. Tin both pads equally and thin - the film left by one touch of a 0.8 mm conical tip with 0.5 mm wire is about right for a 0603. The second most common cause is flux imbalance: flux applied to one joint only, so only one joint wets properly.
Practice drill
Deliberately create ten tombstoned 0603 parts by pre-tinning only one pad, then fix each using the single-iron equalisation sequence. Time yourself; under twelve seconds per part is the target for a repair that will pass a 20x inspection.
Failure modes
| Symptom | Cause | Treatment |
|---|---|---|
| Part re-lifts immediately after the tip is removed | The second joint was not yet liquid when the first froze again, so the imbalance returned | Wet both joints within a single 2.5-second window and do not lift the tip until the chip has visibly dropped flat |
| Termination cracks after the repair | Tweezers pressed the chip during cooling, or the board moved before the alloy froze | Use tweezers only to stabilise laterally, and count three seconds of stillness after the last tip contact |
| Same part tombstones again within a week | Unequal solder volume on the two pads was never corrected | Wick both pads clean, re-tin them equally with a single touch each, and reduce the paste or wire volume by half |
Supplies
- 0.3 mm SAC305 solder wire
- ROL0 no-clean flux pen with a fine nozzle
- 0.5 mm wire for equalising the pre-tin
- Isopropyl alcohol and a fine brush
Tools
- Station at 310 degrees C
- 0.8 mm conical tip (a second iron helps)
- Fine tweezers for stabilising, not pressing
- 20x stereo microscope
Safety
Repeatedly reheating a small footprint drives flux volatiles into the air directly in front of your face. Work with the extraction nozzle between you and the board, at bench height, not above chest height.
Neighbouring cards
- Dead-bug wiring a TSSOP 300 °C / 0.8 s
- Tip tinning, storage and end-of-day care 300 °C / 0.5 s
- Hand-placing a 0402 passive 320 °C / 1.0 s
- Two-iron removal of a 0805 chip 330 °C / 1.5 s