The printed circuit board industry defines heavy copper as layers exceeding three ounces of copper, or approximately 0.0042 inches (4.2 mils, 105 μm) thick. PCB designers and fabricators often use heavy copper when design and manufacturing circuit boards in order to increase current-carrying capacity as well as resistance to thermal strains. Heavy copper plated vias transfer heat to external heat sinks. IPC 2152 is a standard for determining current-carrying capacity of printed circuit board traces.
What's the minimum amount of copper a layer in a PCB can have to be considered "heavy copper"? About how thick would a PCB layer be if it contained three oz. of copper? What will a circuit board with heavy copper carry very well? What would a PCB designer use heavy copper to make their circuit board resist? Where does the heat go when it leaves heavy copper-plated vias?