Back in the 70s when I started getting interested in electronics, tons of magazines catered to the hobbyist market. Popular Electronics was my favorite, and I think I remember the advertisements more than anything, probably because they outnumbered articles by a large margin. Looking back, it seemed like a lot of ad space was sold to companies hawking the tools and materials needed for wire wrapping, which was very popular for prototyping in the days before solderless breadboards were readily available. I remember beauty shots of neat rows of small, gold posts, with stripped wires wrapped evenly around them.
To the budding hobbyist, wire wrapping looked like the skill to have. With a huge selection of posts, terminals, and sockets for ICs and discrete components, as well as a wide range of manual and powered wrapping tools, it seemed like you could build anything with wire wrapping. But fast forward just a decade or so, and wire wrapping seemed to drop out of favor. And today — well, does anyone even wire wrap anymore?
Where Inventions Were Born
Almost everything we take for granted in the modern world can trace at least some of its lineage back to Bell Labs, the invention factory in the New Jersey suburbs, and wire wrapping is no exception. While wire wrapping may not have been invented there — a good argument can be made that it started in the previous century with telegraph linesmen splicing and securing wires in the field — the needs of the telephone industry, particularly in the central office, propelled the development of tools and techniques that would make connections easier. Bell Labs and Western Electric, the manufacturing arm of AT&T, would perfect wire wrapping in the mid-1950s.
The idea behind wire wrapped connections is simple — make a tight, metal-to-metal connection that’s electrically and mechanically solid, and do it as rapidly as possible. Soldering seems like it would make more sense electrically and mechanically, but it takes time and skill to execute properly, and introduces problems of its own. Wire wrapping, on the other hand, allowed telco techs to make hundreds of connections quickly, with simple tools, and in tight spaces.
Specifics varied between applications, but the basics include terminals in the form of posts with a square cross-section and insulated solid wire. Insulation was stripped to a specified length, with care taken to avoid nicking the conductor within. The stripped wire was loaded into the metal bit of a wrapping tool, which was then placed over the post. A few quick turns of the bit, either with hand or electric power, wrapped the wire snugly around the post for about five complete turns and completed the connection.
Bil Herd did a great piece on the tools and techniques of wire wrapping a few years back, and this video shows what’s involved in making wire wraps:
Where Is It Now?
So what made wrapped connections so great? Part of it was the electrical and mechanical properties of the connection. A properly wrapped post would have at least one turn of the insulated part of the wire wrapped around the post, providing a degree of mechanical support that kept the conductor from breaking if the assembly were subjected to vibration. There’s also the benefits of the square post corners cutting into the round conductor twenty or so times along the wrap. Such connections are gas-tight, so oxygen is excluded from the mating surfaces and oxidation inside the joint is avoided. This also lets the wire and post form a cold weld, significantly reducing the resistance of the connection.
But if wire wrapped connections are so good, why don’t we seem to see it used much anymore? As Bil pointed out in his article, wire wrapping was the way to go when prototyping digital circuits during his Commodore days, allowing techs to execute an engineer’s latest design quickly and easily. It seems like there would still be a market for that in the hobby electronics field; dominated though it may be by Arduinos and Pis, there are still a lot of terminals with square posts on such modules that are just begging to be wrapped.
And yet we see precious little wire wrapping these days, at least judging by your tips and Hackaday.io projects. Why is that? Is it the rise of super cheap PCBs and the tools to design them quickly? Is it the increased availability and use of SMD components and the tools to properly handle them? Maybe wire wrapping is mainly used in the industry today for prototyping and has just lost favor in at the hobby end of the market? Or perhaps my perception is wrong, and wire wrapping is alive and well across the board, in which case maybe I should invest in some Kynar and a squeeze tool and get wrapping.
What’s your experience with wire wrapping? Sound off in the comments below.