Make Beautiful Solder Joints

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Introduction: Make Beautiful Solder Joints

About: I run the Maker Project Lab blog, and a weekly video series called Maker Update. Email me at donald@makerprojectlab.com

The quality and design of project boards has become so good in recent years, that I almost feel bad putting them together. In this guide, I'm going to show you a simple soldering technique that can make the back of your boards look as nice as the front. You'll learn how to make perfectly smooth, consistent solder joints that look impossibly tidy.

In full disclosure, I learned this technique from Saar Drimmer, who runs Boldport and sells stunning kits (some shown above, with permission) through his club. I don't work for them or make any money from them, I'm just a fan.

But as a fan, I had this dilemma of loving his board designs so much that I didn't want to destroy them with my haphazard soldering. The boards in his photos looked immaculate, like the soldering had been done by a robot.

It turns out he was just using a technique I hadn't seen before (also described in his video here). I suspect the technique predates Boldport, but I refer to it as Boldport Style. If there's already a name for this I should know of, please correct me.

Step 1: Create a Standard Through-Hole Solder Joint

First, you just need to make a standard, through-hole soldering connection. Nothing fancy. No special solder or soldering iron.

For what it's worth, though, here's what I'm using (linked out to Amazon):

Hakko FX-901 Portable Soldering Iron
Love this thing. Heats quick, gets hot, solder anywhere. I use rechargables.

Hakko CHP-170 Flush Cutters
THE critical tool for making this technique work, though any flush-style snips will work.

Lead Free Rosin-Core Solder
Because it turns out lead is toxic, so why not?

Brass Wire Sponge
Cleans without water. Keeps your tip hot. Looks like C-3PO's... er, ashtray.

Safety Glasses
All those clipped leads have to go somewhere. Better it not be your eyeball.

If you need any guidance learning how to solder, Adafruit has a great guide. I also love the EMSL guide on how NOT to solder.

Step 2: Flush Cut the Joint

Next (with safety goggles on your face!), trim the lead or wire you just soldered down as flat against the board as you can go. Basic wire cutters won't get you all the way flat, that's why the flush cutters are key.

If you've received any instruction on soldering, or read any books on the subject, you've likely been warned not to aggressively cut the solder joint down all the way. For all practical reasons, they're right. If you're soldering up something that has a critical task and people depend on it working, don't monkey around with fancy soldering tricks. You could damage the board, weaken the joint, and generally ruin someone's day.

That said, if you're soldering up a blinky robot badge (like me) and don't want the backside poking your shirt. Or maybe you've got some artsy, portable project that people are going to fondle at Maker Faire -- then by all means, live dangerously and flush cut that sucker in the name of beauty.

Step 3: Reheat Joint With Dab of Solder

Now, the trimmed joint may be flat, but it's not pretty until you briefly reheat it and introduce just a touch of solder.

Poke your iron back into the joint just long enough to see the solder liquify, then add just the smallest amount of new solder back into it and pull your iron away. This will take some practice to not go overboard with the solder or leave your iron in too long.

Ideally, what your left with is a smooth, shiny dome of solder that reminds me of a mini upholstery tack. My guess is that it has something to do with the surface tension created by adding new solder and the lack of any central element for it to gather around.

When you do this across every solder point on a board, the cumulative effect looks really sharp. And because every joint is built up from the same flat starting point, I find it much easier to get a consistent look from point to point.

That said, pulling off this trick essentially means soldering every connection twice. For a few dozen connections, it's cute. For a few hundred, it's a chore.

Step 4: Remove Flux

And since we're being all type-A about making the board pretty, take a moment to soak a rag in some rubbing alcohol and scrub away at the little pools of flux left behind on each joint. With the solder points all smooth now, it's really easy to scrub away at the board without hurting your hands or getting the rag caught on the leads.

For what it's worth, I also have a can of stuff called Flux Off, but I don't recommend it. It's nasty stuff with all kinds of warnings on the side. Especially with the smoothed out solder connections, rubbing alcohol and elbow grease tends to get the job done just as well in most cases.

If you liked this tip, be sure to give me a vote!

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69 Discussions

I've done this before, and like the results. But I wanted everyone to know about a possible complication, which sort of reinforces the warning given by the author not to do this on important circuits.

Shortening the leads like this allows the component to fall out partially if you hit both leads at the same time (like with 5mm white indicator LEDs) or if you switch too quickly from one lead to the other. And you may not be able to tell if one of the leads has a poor connection, because the smoothness of the finish hides whether the lead is in or out. So, I try to keep track of the component position and angle especially, as well as reinspect after finishing. And I also tend to do all left leads at once, and then all right leads in a separate operation, thereby ensuring that both leads aren't in the melted state at the same time. This way of soldering also reduces the chance of overheating a component, since you're allowing it to cool down before heating up the other side. Hope this helps.

This is great!! I have been soldering since 1990 and my joints still look amateur-ish. I am self-taught and know the basics but now I will have technique.

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beul

11 months ago

Thank you for shared, i like it

Crazy comment thread. Where do I put in a request for an "Soldering to IPC Standards" Instructable?

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gm280

11 months ago

It is good you are re-flowing the sold after cutting the wire. That way there is no dissimilar metals exposed to start corrosion. A different idea, and the way they teach you in the NASA certified soldering schools, is to cut off a small portion of the component lead, lay it down flat next to the feed-though component lead and use your flush cutters to cut the lead to the diameter of the lead. Then you solder the lead and everything is covered and finished at once. I used to be a NASA certified micro-miniature solderer for decades. Retired now.

15 replies

thats military spec so its expected. these are just consumer projects so the standard doesn't have to be that high

Could you please clarify this? I was following you right up until the "cut the lead to the diameter of the lead". It sounds like something I would like to understand. Have you ever considered doing an instructable that would give additional tips on soldering or micro-soldering? I think that would be a very useful instructable.

Elohira, What I mean is you cut a small portion of the component lead off. Then you lay it flat next to the though lead of the same component. The stay a flush cutter and use the cut off lead to cut the component lead to the same height. That would make the component lead the exact same length as the diameter of the lead. Then you remove the cut off lead and solder the connection.

Soldering Aid.jpg

Thank youl. That makes it entirely clear

I think what is meant is to cut the height of the protruding lead to the width of the wire. So if the wire is 1 mm in diameter, let 1 mm protrude before reflowing the solder.

Thanks. what you say makes sense.

I did not understand what you wrote. I am a NASA engineer and have do some soldering now and again but have not taken any soldering classes at NASA. I re-read what you wrote and cannot understand it. please if you don't mind, say it differently so I can understand. Sorry to bother you. Thanks.

I also had the NASA soldering classes, although I managed only class 2 certified. I was a missile tech some 30 + years ago.

This type of soldering was always called blob solder and is not a way to have a good solid connection. The clenched lead is always going to be the strongest.

Semper Fi...

Familiar with clenching nails, i.e. turning over, usually on the backside, but not heard of it for wiring.

I'm probably already using it, but hadn't named it. A classic use is when attaching flying leads to a board. A flying lead, just through the hole with no support is soon going to come adrift and start to rotate and lead to some funny results.

With flying leads, I push some excess stripped lead through the hole, trim it to leave a few millimetres sticking out. Turn it over 90-degrees and solder.

Result is a much stronger, non-rotating flying lead.

Just as an add-on, a good flux is key. Never rely on the cored flux alone, but now exclusively use a syringe of Chip Quik. Gooey, but good.

I love this idea. I'm excited to give it a try.

This is actually better than what the instructable teaches. Because when cutting flush to the board after soldering, he is putting heavy tension on the copper island on the board, which might get loose because of that. Cutting the wire short before soldering will not give you the risk of loose copper tracks.

...also called "lifting a pad", and is VERY frustrating when it happens... :-)

Just FYI, this is mostly for appearances. If your assembly Is going in something critical like medical patient qualified devices, nuclear power plants or SpaceX Rockets, your friendly IPC quality inspector is going to have a conniption fit. ;)

It is in fact beautiful though.

In Mill-Spec soldering the joint must not have any exposed copper, so the hand soldering technique is much like shown here. We had a flow solder machine that flowed a layer of wax on the solder side of the board to hold the components in place. Then a lead saw cut all the leads to length. The board was then brought over the solder wave and soldered. It produced perfect solder joints, but like most flow solder machines, there was a lot on maintainance.

That's a neat trick and a neat job