What are these circular patterns on PCBs?

Question

What are these circular patterns on PCBs? Are they called PCB copper thieving? What is the use of these designs?

Answer 1

The top board is too blurry to tell. It could be anything from test points to pads for interfacing with another board or even a via array for RF shielding.

The bottom picture is just a copper hatch. Copper hatches are used for a variety of reasons including saving a very small amount of copper or using less copper for thermal, mechanical or capacitive reasons.

Less copper means less thermal transfer which can be useful if you don't want as much heat flowing throughout the PCB.

In flex cables copper hatches are used to allow the cable to be more flexible.

Capacitive touch sensors can use a copper hatch pattern to reduce capacitance between two conductors.

Answer 2

That does look like copper thieving.

On external layers like this it is usually done to create more uniform copper distribution to help the etching and plating be more uniform and predictable. It can also prevent warping of the board from thermal cycles.

These pours are often left floating, but may be connected to ground or Vcc.