There is really no set definition of what constitutes a Heavy Copper PCB. General,in the industry label PCBs with 3 or more ounces of copper on the inner or outer layers as a heavy copper PCB.
Andwin have made many type heavy copper pcb and extreme thick copper PCB for Customer.
such as inner layer 8 OZ, out layer 40 OZ(1.05mm). http://www.andwinpcb.com/heavy-copper-pcb/
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