Modern electronic devices keep getting smaller, and that trend has driven the widespread use of Flexible Printed Circuit Boards (FPCs). One interesting thing about FPCs is that in many designs you can actually see the internal traces from the outside, which makes their structure relatively easy to understand.
If we take a single-layer FPC as an example, its structure is quite simple. It usually consists of a copper layer, with insulating cover films on the top and bottom. In some designs, a stiffener is also added to provide extra mechanical support. Because the structure looks simple, many engineers tend to overlook how important the copper foil itself really is.
