Photos: WS2812 LED ring, soldering, desoldering

  • November 29, 2016
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Mucking About With Things Sodding soldering The Diary of Lupin Pooter
No black wire available at the time for the GND connections, so I used gray.

Last week, I wanted to test-drive one of the 24-LED WS2812 5050 RGB LED rings I’d bought a ways back. Getting it working, controlled by an Arduino board running the Adafruit NeoPixel library, was easy peasy. Except for the soldering step. For reasons that weren’t apparent to me while I was wielding my soldering iron, getting those six leads attached to the LED ring was more of a chore than it ought to have been.

Regarding my choice of wire colors, yes, the GND wires should’ve been black and the VCC wires should’ve been red. However, it wasn’t until after I’d begun cutting lengths of 22 AWG wire to use as leads that I realized I didn’t have any black wire in the same gauge on hand, so I snipped two lengths of gray wire for the GND connections instead. Then, I managed to solder the first of my blue lead wires to a VCC pad. The proverbial die had been cast and I was loath to desolder anything if at all possible, so I settled for consistency rather than correctness.

GND: gray, VCC: blue, and IN and OUT: red. Voilà!

Too much heat and you shrivel your wire insulation.

Next, please allow me to draw your attention to the edges of the insulation on most of the wires. They look mighty shrinky-melty, eh? That’s because I held the point of the soldering iron on each of the wire ends (resting, in turn, against a pad on the LED ring) until the solder would melt and flow onto it. Evidently, long enough to melt the solder was a tad excessive from the perspective of the wires’ insulation.

In the end, I was compelled to desolder one of the leads because I’d flubbed my first pass and that wire’s solder blob was touching a neighboring wire’s solder blob. And though I have spools of desoldering wick, I hadn’t yet gotten around to skimming any of the YouTube videos illustrating its correct use and I didn’t have any flux, which I could’ve applied to the desoldering wick to help it take up the melted solder a bit better. Still, I managed to muddle through.

TAKUMi ECO A075 lead-free solder.

I’ve been using TAKUMi ECO A075 solder, because it was the only lead-free solder available at WECL, Hong Kong’s closest facsimile of a hobbyist electronics shop. There doesn’t seem to be a TAKUMi web presence, only odds and ends of TAKUMi-branded electronics equipment and material listed for sale on sites like eBay. That, and the fact that takumi is a Japanese term meaning artisan, leads me to wonder whether this mightn’t be a case of made-in-China-but-a-Japanese-name-sounds-more-trustworthy. For the solder alloy composition, I’m relying on the store-printed sticker affixed to the far side of the dispenser shown above. It says my TAKUMi ECO A075 solder is 99.25% SN (tin) and 0.75% Cu (copper) by weight.

Belatedly, I looked into the characteristics of that combination of tin and copper. The closest alloy in Wikipedia’s solder alloys chart is the Sn99.3Cu0.7 mixture. The description in the Wikipedia article mentions that incorporating some nickel yields an alloy that’s more fluid and hence easier to work with, but there’s no indication on my package of TAKUMi solder wire that it includes anything other than tin and copper.

Next time, I’m going to give a different flavor of solder a whirl and see whether that makes the experience less white-knuckly.

Indium Corp.'s SAC 305 solder.

Months ago, I purchased a (still unopened) one-pound spool of Indium Corporation’s CW-807, a SAC305 (96.6% Sn, 3.0% Ag, and 0.5% Cu) product. It’s lead-free and rosin-cored and, according to its data sheet (see link in table on the manufacturer’s Flux-Cored Wire product page), it’s Indium Corp.’s best selling flux-cored wire. That certainly sounds promising.