Joint type · SMD
Surface mount
Chip, gull-wing and small-outline parts that carry their own heat away faster than the iron can deliver it.
- In this joint type
- 7/10
- Tip temperature span
- 300–350°C
- Dwell span
- 0.5–1.5s
- Scheduled ahead
- 3
| Technique | Tip | Tip °C | Dwell s | Flux | Alloy |
|---|---|---|---|---|---|
| Dead-bug wiring a TSSOP | conical 0.2 mm | 300 | 0.8 | ROL0 no-clean | SAC305 |
| Dragging a 0.5 mm pitch QFP and clearing bridges | hoof 1.2 mm | 350 | 1.2 | ROL1 mildly activated | SAC305 |
| Two-iron removal of a 0805 chip | knife 2.0 mm | 330 | 1.5 | ROL0 no-clean | SAC305 |
| Fixing tombstoned 0603 and 0805 parts | conical 0.8 mm | 310 | 1.0 | ROL0 no-clean | SAC305 |
| Tip tinning, storage and end-of-day care | chisel 2.4 mm (care applies to all geometries) | 300 | 0.5 | ROL1 mildly activated | Sn63Pb37 |
| Drag soldering a SOIC-8 with gel flux | hoof 2.0 mm | 340 | 1.5 | ROL1 mildly activated | SAC305 |
| Hand-placing a 0402 passive | conical 0.4 mm | 320 | 1.0 | ROL0 no-clean | SAC305 |
Dead-bug wiring a TSSOP
Dead-bug mounting - the package upside down with its leads in the air - is the standard way to prototype with a fine-pitch part that has no breakout board. Each lead gets a 0.1 mm wire, and the whole assembly is held by the first two wires you solder.
Dragging a 0.5 mm pitch QFP and clearing bridges
At 0.5 mm pitch the gap between leads is smaller than the diameter of most solder wire, so the alloy has to come from the tip's reservoir rather than from a hand-fed wire. Bridging is not a mistake to avoid - it is a stage in the process to be cleared afterwards.
Two-iron removal of a 0805 chip
Two irons remove a passive in two seconds without touching the body, which matters when the part is under a microscope and the neighbouring components are 0.5 mm away. The technique is also the safest way to lift a component from a board you intend to re-use.
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.
Tip tinning, storage and end-of-day care
Most soldering failures blamed on technique are actually failures of the tip: an oxidised face transfers heat at a fraction of its rated rate, and the operator compensates by pressing harder and holding longer. Tip care is the cheapest quality improvement available.
Drag soldering a SOIC-8 with gel flux
A SOIC-8 at 1.27 mm pitch is the easiest drag-soldering target there is: wide enough that bridges clear easily, narrow enough that a 2.0 mm hoof can span two leads. This is the technique to learn drag soldering on before attempting TSSOP.
Hand-placing a 0402 passive
A 0402 chip is 1.0 mm long and weighs about 0.6 mg, which means the iron's own magnetic field and the flux vapour are both strong enough to move it. The technique is to stop trying to hold the part and let surface tension centre it instead.