Saw the thread about first-time header soldering and figured I'd share what took me way too long to learn. The trick with headers is to solder just one corner pin first, then check if the header is sitting straight before doing the rest. If it's tilted, melt that joint and reposition it. So much easier than fixing twenty crooked joints later. Once you're going, touch the iron to the pin and pad at the same time and feed solder into the joint, not onto the iron tip. Two or three seconds is plenty. If solder won't stick, the joint isn't hot enough yet, not the other way round, so hold the iron there a moment longer instead of piling on more solder. A cheap iron makes this harder because the tip temperture drops when it touches a big pin, but it can still do the job. Clean the tip on a damp sponge often and tin it with a little fresh solder before each joint. A tiny bit of flux helps everything flow. Afterwards, look at each joint. It should look like a small shiny volcano hugging the pin. Dull and lumpy means reheat it. Then plug the board in and see if it shows up. Even ugly joints usally work if the solder actually wetted the pin.
A quick guide to soldering pin headers for beginners
Nov 06, 2026
Last reply: 10 hours ago
4 Replies
I did my first Pico header job last month for a door sensor project and learned the corner-pin lesson the hard way, except I didn't learn it. Soldered all 40 pins on my Waveshare board before noticing the whole header sat at a slight angle. Had to reflow nearly every joint with a cheap 30W iron from an electronics starter kit, which was miserable becasue the tip cooled down the second it touched a pin.
One thing that saved me on the next board: I stuck the header pins into a breadboard first, set the Pico on top, and soldered it that way. The breadboard keeps everthing perfectly lined up so even if my joints are ugly the pins stay parallel. Took maybe ten minutes versus the hour of rework on the first attempt. The dull versus shiny joint thing took me a while to trust. My first instinct was that a good joint needed more solder, so I ended up with big blobs that turned out fine electrically but looked terrible. Reheating with a touch of flux from a syringe I got for a few quid fixed most of them without adding anything. The only joint that actually failed me was one where the pad lifted slightly, probaly from me holding the iron on too long out of impatience. It read fine on the multimeter but dropped out intermittently once the board was in the enclosure. Reflowed it properly and it's been solid for weeks now.
Ha, the breadboard trick is the modern way of doing it alright. Back in the day we'd stick the header in place with a dab of Blu Tack or a scrap of masking tape and eyeball it. Works too, but the breadboard is neater if you've got one spare. One thing I picked up decades ago that still serves me: tin both the pad and the pin with the tiniest amount of solder first, then just touch the iron to bring them togather. Barely need to feed any extra wire in after that. Makes the whole job faster and the joints come out neater without trying.
One thing that made a big difference for me early on was switching from lead-free solder to the old 60/40 stuff. Leaded flows so much easier and forgives a slow hand, which is handy when you're still figuring out timing. Just wash your hands after and keep it away from the kitchen table if there's kids around. Also don't skip trimming the pins short afterwards. I left mine long on my first board and shorted a couple against the USB shield. Took ages to find that one.
Seconding the corner pin method, it genuinely makes all the difference. First board I ever did went fine thanks to it, but I'd add one thing that helped me: solder the corner pin on one side, then count how many pin lengths stick up on each edge before committing. I caught one sitting one notch off centre that way, the board would never have lined up with the case holes. A couple of seconds saved me a whole strip of soldering and a reflow session.
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