Rolled Annealed (RA) Copper. RA copper has been used extensively in the flex circuits manufacturing and rigid-flex PCB fabrication industry for decades. The grain structure and smooth surface is ideal for dynamic, flexible circuitry applications. Another area of interest with rolled copper types exists in the high-frequency signals and applications. It has been proven that copper surface roughness can impact high-frequency insertion loss and a smoother copper surface is advantageous. Please check another type Electro Deposited (ED) Copper.