A Newbie Takes The SMD Challenge At Supercon

First-time visitors to Disneyworld often naively think they’re going to “do” the park in three days: one day for the Magic Kingdom, one day for Epcot, and one day for everything else. It’s easy to spot such people, collapsed on a bench or dragging exhausted kids around while trying to make their way to the next must-see attraction. Supercon is something like that — a Disney-esque theme park for hackers that will exhaust you if you don’t have a plan, and if you don’t set reasonable expectations. Which is why I was glad that I set only one real goal for my first Supercon: take the SMD Soldering Challenge.

Now, while I’m pretty handy with a soldering iron, I was under no illusion that I would be at all competitive. All my soldering experience has been with through-hole components, and while I also used to doing some production soldering on fine-pitch connectors, the whole surface-mount thing is new to me. I entered mainly because I wanted to see what was possible coming in raw. At best I’d learn what my limits are, and at worst I’d fail spectacularly and provide grist for a “Fail of the Supercon” post. It’s a win either way.

Scoping It Out

I decided to get the challenge out of the way as quickly as possible, so I started sharking around the table early in the afternoon on Friday. As he did last year, Al Williams was running the station. I signed up for the 4:30 heat and hung around a bit to get enough of an idea of what to do to not embarrass myself. It looked like everything was laid out really well. Each station had a good quality soldering station, a lighted magnifier, a few hand tools like flush cutters, pliers, and the all-important tweezers, and a roll of fine solder. There were a bunch of shared tools and supplies too, like desoldering braid, solder suckers, flux pens, and an LED tester. I watched enough of the action to get an idea of the workflow.

When it came time for my heat, I settled into my station and got things squared away. They thoughtfully provided magnifier hoods so that those of us with older eye could partake, and I got mine set up just the way I like it. The rules are simple: you get five minutes to open your kit and scan for missing parts, and to ask any questions you might have. After that, it’s 35 minutes to solder up everything, and each board is graded on function, neatness, and time.

The kit is a simple blinky, powered by a coin cell with an ATtiny85 driving five LEDs. The current limiting resistors and LED footprints start at 1206 and go down to a ridiculous 0201. When I opened mine, I knew the toughest part wouldn’t be the soldering itself, it would be getting the components free from their carriers. The components were helpfully segregated by size but taped down to a piece of paper. Adhesive tape and I are old enemies, so I knew there’d be trouble.

A Man With a Plan

Not too shabby, but 0402’s my limit.

I worked out a quick strategy: tape the PCB down and start with the largest components. I’ve watched enough soldering videos on YouTube to know that flux is your friend, so I got busy with the flux pen. I added a dab of solder to one of the ATtiny85 pads and tacked that in place. It’s about this time that I noticed the soldering iron tip was not exactly ideal — a chisel point — which looked massive even next to the fine pins on the SOIC package. I was surprised by how easily the chip soldered down, likely more a testimony to the ample use of flux and the good quality solder masking on the PCB.

I decided to get the cap and the first resistor and LED soldered down to make sure I had the polarity right. I assumed that the blinky would blink even if only partially assembled, an assumption borne out once I soldered down the coin cell holder (upside down, d’oh!) and slipped the battery in. My earlier fear that getting access to the components would be the bottleneck were well-founded; just getting the cover tapes peeled off the carriers was a tedious, time-consuming job. But I kept going with the next size down, the 0805s, without much trouble.

Like a machine – an amazing 6:45 start to finish by Fred T!

Just about then, someone called time, only about 8 minutes in. Oh perfect, I thought – I’m not even a third of the way done. But as I said, I wasn’t trying to be competitive, so I shrugged it off and kept going. The 0603s were a little tougher, but I still managed to get them soldered down. I found the LEDs to be the most challenging; figuring out the polarity was tough with the smaller sizes. The wheels finally fell off for me with the 0402s. I managed to get the resistor on, and the LED, but I must have reversed the polarity because the LED wouldn’t light. I tried unsoldering it and reversing it, but all I managed to do was turn it into a molten blob. I called it at 33 minutes, and Al generously scored me a 3.25 out of a possible 5.

How fast?

Records for the SMD Challenge have been falling all weekend. The winner last year put in an amazing 16 minute time. This year, Fred T. set the record with a mind-boggling time of 6:45! Contributing Editor Tom Nardi was watching that heat, and said, “The guy looked like he was just vibrating!” And the quality was top notch — it certainly looks hand-soldered rather than reflowed, but amazing nonetheless.

All in all, I really enjoyed taking the SMD Challenge. I learned a ton, and I feel like I added another skill to my repertoire. I’ve got several designs in the works that I was planning on making through-hole simply because I hadn’t taken the leap into SMD yet. Now that I have, I’ll have to rework the design and join the cool kids on the surface-mount side of the street.

17 thoughts on “A Newbie Takes The SMD Challenge At Supercon

  1. At the risk of getting discouraged early on I think I would have started with the smallest parts. That way when I am working on the hardest part there is the least stuff to get in my way.

    I suppose that thinking comes from through-hole soldering and those other parts shouldn’t really be “in the way” but even if it’s only a psychological advantage I think it would still just seem easier.

    1. Half way through university, I came up with a strategy for writing exams: read all the questions first, then do the problems in order easiest first, hardest last. It would feel really stupid to get stuck at the hardest led when you could have done all the others successfully.

      1. In general, the best strategy is to do the easy ones first. Then the ones you aren’t quite sure of. If there is time, then tackle the really hard ones. If there isn’t, then you probably are no worse off.

  2. Also worth mentioning that Fred actually took a time penalty to clean up his work, as I recall his original time was under 6 minutes, but he had a non-functional LED and some issues he wanted to resolve so Al let him go back at it. Was incredible to watch.

  3. Pre-tin all 22 RCD pads in one go. Use a knife tip to reflow both pads of each while placing each component. Pre-tin one pad of the SOIC and tack-in-place. Drag the other 7. 6 min seems slow, but I imagine it looks easier than it is under a clock. Are the boards for sale anywhere?

  4. I like the idea of putting the battery in as soon as you can. That way, you can put in the resistor and then hold the LED up to the pads with the tweezers to see if you have it the right way around right away (according to whether or not it blinks). Although I suppose with the smallest ones, you’d have to be careful not to short out the pads with the tweezers (or too much solder).

  5. I clean everything well with IPA, use new “no-clean” flux core solder (clean it too) and never touch flux outside of what’s already in the solder. Extra flux just makes a mess and tends to want to float components off of their pads, instead of sucking down with just solder. For really tiny stuff, it makes it hard to see what the heck is going on.
    I leave flux to soldering heavy braid to large, heat sinking chassis’ and the like or I might clean up old dried out soldering braid with it to give it a little extra punch.
    Some people swear by it and use it by the bucket full, but I’ve never found it to be terribly useful as most parts are pre-tinned anyway and do fine with a little cleaning.

  6. SMD is surprisingly easy. I am not expert as I have only done it a dozen times or so, but I honestly think it is better than through hole, especially if you need to re-work anything. Obviously it isnt practical to do it by hand on a large scale, but if I were handy enough to make my own PCBs, I would probably do SMD for almost all of my small projects.

    1. This is true.

      And there’s a surface-mount part out there for everyone. Heck, 1206 parts are just about as big as through-hole components are. I use them all the time without magnification. 0805 and on, I like a loupe.

      Nothing _requires_ a hotplate/reflow, but I switch methods at 0402.

      And do note that this was Dan’s first try at SMD soldering ever! The non-insane stuff is simply not insane. :)

  7. I amazes me how this project took on a life of its own. I really just wanted to see what the different packages looked next to each other and didn’t actually believe a 0201 was possible by hand. Sooo many people have proved me wrong. You can see the list here: https://hackaday.io/project/25265-an-unfortunate-smd-project/log/71954-0201-club

    If you completed the challenge at this event and want a certificate, follow the instructions on the site above.

  8. What I like about 1206 and 0805 is you can actually solder those onto perf board without too much trouble. They’re just the right size to span the gap. Even something like an SOT-23 can be turned 45 degrees and span 3 0.1″ holes. I got a bunch of the Adafruit Perma-Proto Half-sized Breadboard PCBs made up and mix and match through-hole and SMD parts on them with no problems at all. Cut one of the traces in the middle and then stick a SOT-23 package on that row at the 45 degree angle with one of the the two legs and the single leg spanning the cut and the second leg over to the next trace, etc.

  9. There are SMD practice solder boards available on eBay, Amazon, Aliex and even Wish for about $2. They have all different sizes and many more pads and parts to practice on if anyone is looking into learning hand smd work. I actually bought a few because I needed some SMD components and it was cheaper than buying them on a reel strip!

    1. Well done Dan and every one else that gave it a go.

      My job doesn’t require much soldering, its quiet discouraged in the medical repair business so when I need a mental health break at work I grab a trashed circuit board and find the smallest pin pitch IC’s desolder one clean up the boards and solder it back on.

      I try different techniques just for the exercise. helps keep the eye/hand cordination up for when a family member or friend brings me their laptop to fix up.

      I find those illuminated magnifiers to be next to useless, or maybe Ive only been exposed to really crap ones. In my experience I have found them to have a large amount of distortion particularly anywhere away from the center and the distortion is frequency dependent. ie they will separate the colors.

      A stereo microscope is the best way to fly.

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