HOW-TO GUIDE
How to Solder Fine-Pitch SMD Components
By the OhmSavvy Research Team ·
Safety: hot tip, flux fumes and tiny parts
- A soldering tip commonly runs at 300–370°C. Always return the iron to its stand, and work with the cord routed away from your hands.
- Fine-pitch work means heavy flux use and your face close to the board. Use a fan or fume extractor that pulls fumes away from you, and wear eye protection: flux can spit.
- Wash your hands after handling leaded solder, and clean flux residue with isopropyl alcohol in a ventilated space.
What counts as fine pitch?
Pitch is the center-to-center distance between neighboring pins. Through-hole DIP chips use 2.54 mm (0.1 inch), which gives you plenty of room. Surface-mount packages shrink that to half or less, and anything around 0.65 mm or finer is generally treated as fine pitch, because the gap between pins becomes narrower than the tip you are soldering with. The values below are common for each package family; always confirm the exact pitch on the part's datasheet.
| Package family | Common pitch | Iron-solderable? |
|---|---|---|
| DIP (through-hole) | 2.54 mm | Yes, the easy baseline |
| SOIC | 1.27 mm | Yes, pin by pin or drag |
| TSSOP / SSOP | 0.65 mm (often) | Yes, drag soldering recommended |
| QFP / TQFP | 0.8, 0.65, 0.5 or 0.4 mm | Yes, drag soldering with plenty of flux |
| QFN / DFN | 0.5 mm (often) | Pads are under the body: hot air or reflow |
1Gather the right tools
An iron alone won't get you through a 0.5 mm QFP. These are the basics that make fine-pitch soldering repeatable rather than lucky:
Temperature-controlled iron
A stable, adjustable tip temperature so the joint heats quickly without cooking the part.
Flux (gel or liquid)
The single biggest factor. Gel or tacky flux stays where you put it on the pads.
Thin solder wire
Around 0.3–0.5 mm makes it easier to load only a small amount onto the tip.
Fine tweezers
Non-magnetic, fine-point tweezers to place and nudge the part.
Solder wick
Fine braid for pulling excess solder off a row.
Magnification + light
A loupe, head magnifier or stereo microscope, with light from a low angle.
2Choose the tip and set the temperature
For tacking corners and touching up single pins, a fine conical or small bevel tip gives the most control. For drag soldering whole rows, a small bevel (sometimes sold as a "mini wave" or hoof tip) or a knife tip holds a small reservoir of solder and slides along the pins. A broad chisel tip is the hardest shape to keep off neighboring pins. Our guide to soldering iron tip types explains the trade-offs, and tip care matters more here than anywhere: an oxidised tip won't wet, and a tip that won't wet leaves blobs.
Fine SMD work usually wants a slightly lower, steadier temperature than general through-hole work, because small pins have little thermal mass and heat quickly. The ranges below are typical starting points, not rules; check your solder manufacturer's recommendations and the component's datasheet for its soldering temperature limits. Our soldering iron temperature guide goes into more detail.
3Flux the pads and tin one corner pad
Start with clean pads. If you removed an old part, wick the pads flat first so the new component can sit level; a lump of leftover solder on one pad will tilt the part and lift pins on the opposite side. Wipe the area with isopropyl alcohol, then apply a thin layer of flux across all the pads. Put a small amount of solder on just one corner pad. That pre-tinned pad is what you will reflow to tack the part down.
4Tack one corner and check alignment
Check pin 1 orientation against the dot or notch on the board marking before anything else; a part soldered rotated is far more work to fix than one placed correctly. Hold the part with tweezers so its pins sit centred on the pads on every side, touch the iron to the tinned corner pin, and let the solder reflow onto it. Remove the iron and keep the part still for a moment.
Now look under magnification. Every pin on all sides should sit squarely on its pad. If the part is off by even a fraction of the pitch, reheat the corner and nudge it. Only when alignment is right do you tack the diagonally opposite corner, which locks the part in place.
5Drag solder each row
Apply fresh flux generously along the row. Load a small bead of solder onto the tip, then place the tip at one end of the row where pins meet pads and draw it slowly along the row. The flux lets the molten solder flow onto each pin and pad, and surface tension pulls it back off the gaps between them. Keep the tip moving at a steady pace; stopping in one spot both overheats that pin and dumps solder there.
01
Flux + tin
Clean pads, flux, tin one corner
02
Tack
Reflow one corner pin
03
Align
Check every side, then tack opposite corner
04
Drag
Fresh flux, small bead, steady pass
05
Inspect
Magnify, wick any excess, clean
Tip angle, speed and where to finish
Hold the tip at a shallow angle so its flat face, not its point, rests against the heel of the pins where they meet the pads. Pressing down on the pins can bend fine leads, so let the tip glide rather than push. Move steadily enough that each pin is heated briefly but fully; if the solder starts to look dull or spiky, the flux is spent and it is time to stop, add more and go again. Any excess solder tends to gather at the last pin of the row, so finish each pass by lifting the tip off past the end pin, where a clean tip can carry the extra away.
If you prefer, solder each pin individually with a fine conical tip instead. It is slower but easier to control on SOIC parts and wider pitches. Either way, the iron basics from how to use a soldering iron still apply: heat the pin and pad together, and let the solder flow to the heat.
6Inspect every pin under magnification
Inspect each row from straight above and then from a low angle with the light behind you. A good joint shows a smooth fillet running from the pad up onto the pin, with clean board visible in every gap. Use this table to read what you see:
| What you see | Likely cause | Fix |
|---|---|---|
| Solder joining two pins | Too much solder, or flux burned off | Fresh flux and a clean tip drag; wick if needed |
| Pin with no fillet | Pin not touching the pad, or not heated | Flux and touch that pin with a fine tip |
| Dull, grainy joint | Overheated, or part moved while cooling | Flux and reflow briefly |
| Ball of solder on a pin | Too much solder, too little flux | Flux and drag the excess away |
| All pins offset to one side | Part slid before tacking held | Reflow both corners and realign |
Fix bridges and clean up
Bridges happen to everyone on fine-pitch parts. Most clear by adding fresh flux, wiping the tip clean, and dragging it away from the body along the bridged pins: the clean tip picks up the excess. For a stubborn one, lay fine solder wick across the pins and press the iron on top. Our guide on how to prevent solder bridges covers causes and fixes in more depth, and how to remove solder from a circuit board explains wick technique. When the rows are clean, scrub the flux residue off with isopropyl alcohol and a brush, then inspect once more: residue can hide a hairline bridge.
More flux, less solder
Common fine-pitch soldering mistakes
- Soldering before the part is aligned. Once two corners are soldered, moving the part means reheating both, and every reheat risks the pads.
- Feeding solder straight into the row. Touching wire solder to fine pins dumps far more than they need. Load the tip instead, or add a tiny amount at the start of the row only.
- Turning the temperature up to fix a slow joint. On small pins, a joint that won't flow usually needs fresh flux or a cleaner tip, not more heat. Excess heat chars flux and can damage the part or lift pads.
- Using a worn or oxidised tip. If the tip won't hold a bright coat of solder, it won't move solder cleanly either. See why a soldering iron won't melt solder for related symptoms.
- Skipping the low-angle inspection. Pins that look fine from above can hide a lifted lead or a hairline bridge at the heel.
- Powering up before checking for shorts. A bridge between a supply pin and ground can damage the part. A quick continuity check between neighboring supply pins, with the power off, is cheap insurance.
Which iron suits fine-pitch SMD work?
Any iron with adjustable, stable temperature control and a fine tip available can do fine-pitch work. A bench station is the comfortable choice for regular SMD soldering, while a compact USB-C iron covers occasional jobs. For more options, see our best soldering iron for circuit board repair picks and the full best soldering irons roundup.
Irons in our reviews that suit SMD work
ESD-safe 100W station with closed-loop control and T18 tips; five presets hold separate settings for fine pins and ground pads.
85W digital, ESD-safe station (70W iron) that heats in about 28 seconds, for dedicated workbenches.
About 60W from 20V USB-C PD (up to 88W at 24V), ~12 second heat-up and an OLED display; built for portability and field repairs.
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Frequently asked questions
Can you solder fine-pitch SMD parts without a microscope?
Down to about 0.65 mm pitch, many people manage with a good head-mounted magnifier or a strong loupe and bright, angled light. At 0.5 mm and below, a stereo microscope makes inspection far more reliable, because a hairline bridge or an unwetted pin is easy to miss at low magnification. A phone camera zoomed in on the joint is a usable stopgap.
Is solder paste better than wire solder for fine-pitch parts?
Paste with a stencil and hot air or a reflow oven is how fine-pitch parts are assembled in production, and it handles leadless packages such as QFN that an iron cannot reach. For leaded packages like TSSOP and QFP, wire solder with plenty of flux and drag soldering works well for one-off builds and repairs.
What size solder wire should I use for SMD soldering?
Thin wire makes it easier to control how much solder reaches the tip. Diameters around 0.3 to 0.5 mm are a common choice for fine-pitch work, compared with the thicker wire often used for through-hole joints. Too much solder on the tip at once is the main cause of bridges, so thinner wire helps.
Why do my SMD pins look soldered but the circuit does not work?
The usual culprits are a pin that looks wetted but is not actually bonded to its pad, a hidden hairline bridge, or a part rotated 90 or 180 degrees. Recheck pin 1 orientation against the board marking, inspect each pin from a low angle, and use a multimeter continuity check between suspect neighbors.
How do I remove a fine-pitch IC without lifting the pads?
Hot air is the usual tool: flux the pins, heat the whole package evenly until every joint melts at once, then lift it off with tweezers using no force. With only an iron, flood each row with solder or a low-melting removal alloy so all pins stay molten together. Never lever the chip up while any pin is still solid, because that is what tears pads and traces away.
