1/2oz copper clad is typically used in the manufacture of double sided PCB's with Plated Through Holes or Via's. The 1/2 refers to the thickness of the copper foil cladding. Typically 1/2oz board is processed and plated upto 1oz during the manufacture process. In low current digital applications either 1/2oz or 1oz can be used, for high current or very low resistance applications 1oz is often specified.
The copper clad is based on FR4 (Flame Retardant 4). FR-4 describes the board itself with no copper cladding. Bare FR-4 is yellow/green in colour. Typically FR-4 for PCB manufacture is clad in 1/2oz or 1oz copper foil.
FR-4 has excellent mechanical performance and good performance in dimension thickness.
Copper cladded FR4 board material has an epoxy substrate with glass fiber enforcement, which is compliant with electroplating.
This is a non flammable sheet materiel, however fumes and dust may irritate skin and eyes and inhalation should be avoided to to the fiberglass nature of the sheet.