What the Flux: How Does Solder Work Anyway?

I’ve been soldering for a long time, and I take pride in my abilities. I won’t say that I’m the best solder-slinger around, but I’m pretty good at this essential shop skill — at least for through-hole and “traditional” soldering; I haven’t had much practice at SMD stuff yet. I’m confident that I could make a good, strong, stable joint that’s both electrically and mechanically sound in just about any kind of wire or conductor.

But like some many of us, I learned soldering as a practical skill; put solder and iron together, observe results, repeat the stuff that works and avoid the stuff that doesn’t. Seems like adding a little inside information might help me improve my skills, so I set about learning what’s going on mechanically and chemically inside a solder joint.

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Solder at Room Temperature

Have you ever seen the science experiment (or magic trick?) where you get water supercooled to where it isn’t frozen, but then it freezes when you touch it, pour it, or otherwise disturb it? Apparently, ice crystals form around impurities or disturbances in the liquid and then “spread.” A similar effect can occur in metals where the molten metal cools in such a way that it stays melted even below the temperature that would usually cause it to melt.

[Martin Thuo] at Iowa University used this property to make solder joints at room temperature using Field’s metal (a combination of bismuth, indium, and tin). The key is a process that coats the molten metal with several nanolayers that protect it from solidifying until something disturbs the protective layer.

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Altoids upstaged by gift card tins

Nothing Earth-shattering here. Just, dare we say it, really cute!

The venerable Altoids mint tin has become an icon of the maker culture. Browsing through past articles on Hack a Day, Adafruit or Instructables, you’ll find project after project for which these pocket-sized enclosures provided just the right fit. Eminently practical, affordable, but the aesthetics have occasionally left something to be desired.

We recently stumbled upon these nifty gift card holders that resemble miniature versions of current-generation game consoles. They might be the perfect housing for your next microcontroller project…

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