The Problem

Early electrical engineers designed for connectivity.  One of the original ways that the pins of vacuum tubes, wires, capacitors, and other components were connected was with wire-wrapping.  This technique requires a machine or operator to wrap a small wire around a post that protrudes through a non-conductive base.  Each net is laboriously constructed in a spaghetti-like mixture of wires and pins.

Example of wire-wrapping from Wikimedia.org

As you can imagine, mistakes were common and almost impossible to trace.  Assembly, troubleshooting, and repairs were difficult if not impossible -- in some cases, it was faster to simply remove all the wires and start over.  That is simply not a sustainable production model.  As early as 1903, engineers began creating the precursors to modern circuitboards and by the middle of the 20th century, the circuit boards we recognize today began to appear in consumer appliances.

The Current Solution

The way the industry collectively decided to solve the problem of connecting the pins of the various microcontrollers is with interconnects made of horizontal copper traces to make in-plane connections, and electrodeposited copper to make out-of-plane connections.

This two-layer circuitboard is the power supply unit from a big-screen television.

This artistic image shows a combination of horizontal and vertical interconnects with the dielectric layers removed

It would be a mistake to assume that PCB manufacture will continue down this one path to manufacture.  There are companies working to integrate additive manufacturing techniques into the PCB space.  For now, this is the world we live in and one that electrical engineers must understand.

So, let's take a quick look at what it takes to put a modern PCB together.