The Return of Wires
What did electronics look like before the printed circuit board? There really was a time before the printed circuit board came to dominate the electronics industry. Whilst the history of printed circuit boards (PCBs) goes back to the Second World War and beyond, for most of us the PCB is a relatively recent innovation. Before the PCB became readily available, engineers had to rely on wires. But how do you handle huge amounts of wire?
How many wires?
For those who don’t want to muck around with screw terminals or soldering irons, wire-wrapping was developed as a simple and elegant method of fixing wires to connectors, or even other wires. Wire-wrap connectors were fitted with long tails, and installers used a small hand-held tool which created a quick and compact termination
The problem was that it made systems very large. When I was a cadet in the 1980s, I was lucky enough to visit some Royal Air Force establishments. I remember that any major installations, at the time dated from the 1950s and 60s, were housed in large air-conditioned buildings containing rows of cabinets. Each of the cabinets was filled with wire.
Not what you'd call compact...
I can only imagine how long it had taken the poor technicians to install all of this wiring. In fact, the only thing that could have been worse was trying to trace a fault if something went wrong during use.
By the time I joined the interconnect industry, wire-wrapping was becoming less and less common and the PCB had come to dominate electronics design, and with good reason. PCBs are easy to make in large quantities and they’re a lot smaller than a whole cabinet of wires. It is difficult to imagine modern life without the PCB – certainly, smartphones would not be the same if we hadn’t moved on from wired circuits!
Wires are making a comeback
The days of wire-wrap connectors are now gone, but this does not mean that cables and wires have gone too. In fact, the future of communications means that wires may be making a bit of a comeback. The reason is simple – data.
We live in a data-hungry world. The Internet of Things (IoT) is connecting everything together, from our car to our fridge into a worldwide network that depends on the flow of data at higher and higher rates. The hubs of this network are the data centres, whose sole task is to facilitate this flow.
This is where the PCB starts to cause problems. The very features that make PCBs so compact and easy to manufacture – regular design, parallel conductors, high density of components – are detrimental to transmitting data at high speeds. As semiconductors are developed that communicate more rapidly, we need to find solutions that remove the limits imposed by the PCB.
High speed. Really high speed
Connector company Samtec has developed its Flyover® technology to address this high-speed problem. The custom-designed Eye Speed® twin-axial (twinax) eliminates the losses that are generated when a high-speed signal is transmitted over a PCB. When combined with a connector system like the NovaRay®, this cable technology delivers a high-density, high-speed solution for the latest generation of data centres.
The result is a connector system that can carry data at a speed of 112 Gigabits per second, using the PAM4 technique. 112 Gbps is a quite staggering performance. To give you an idea of the scale of this achievement, a 4K High Definition movie is streamed at a rate of 14 Mbps, so in theory, the NovaRay could stream 8000 movies simultaneously.
The next decade will see an explosion in the number of devices that will be sharing data. It doesn’t matter whether it’s in the home or in space, the overwhelming demand for more data means that the infrastructure needs to be ready now. Designers need to think of new and innovative ways to achieve this performance and cannot close their minds to so-called old technology. It might be old technology that holds the key to the future.
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I still use wire wrap for many of my prototypes and one-off jobs. However, PCBs are becoming cheaper all the time and their turn around time is getting quicker as well so I am using them more and more for some prototypes. Also, with the software now available to even hobbyists for circuit design, schematic capture, SPICE or other simulation and PCB layout software, it is getting much easier and faster to design the circuits and the PCB.
However, I am not certain wire wrap will die out completely for some time, at least not for designers and prototypes. Sometimes it is just more convenient to wire wrap.
I'm still a fan and user of wire-wrapping, especially for complex layouts like multi-digit LED displays. Using FR4 double sided "perf" boards and male and female headers, it is possible to stack boards like the Arduino shields, each board having complex circuitry. I don't use specialized pins, but keep a selection of RS male headers. The square section is ideal for wraps. The female headers are Harwin M20 types that are "pass through" types meaning that you can push a male header through from either end. This allows a female header to have a wrapping tail. The cost of Tefzel wire is still high but only small quantities are used, in fact I still have reels of wire that are over 30-years old.My OK wrapping tool is similar age, but due to wear and tear, had to be replaced. I don't like the new Kynar wire so much, In my opinion, wire wrapping is a prototyping method par excellence.
As a youngster there was a magazine called Practical electronics, One month they would publish a project and over the next few months the bugs and defects would be ironed out.
I also remember making printed circuit boards with chemicals in a bowl in my mothers kitchen. We were so pleased when red LEDs dropped in price to 80 pence.
Chasing faults in old wired systems was fun....
Just some stories from the age of wires. A school for air traffic controllers where all the console and equipment wiring was black, every pair of wires was black and black. Chasing faults in an (ex-international) airport's equipment room where the wiring records of racks had been lost. No drawings, nothing existed. The first airport installation where a computer generated wire list was used. Maximum number of termination on a point was two. A wire list would be generated that had six connections on a point. The next printout would undo that mess and there would be some other point that would be overloaded. The bright displays which were designed assembled and tested in close proximity so there were no timing issues. Install them in the real world and there were kilometers of coax cable under the floors to compensate for image time delays. That age of wires still exists.