While workers from Samsung-owned factories spoke well of their monthly wages, pay at neighboring suppliers to Samsung is generally significantly lower.

Twenty-seven-year-old Xue Junfen worked at a factory operated by Yaguang Nypro Precision Molding, assembling and inspecting mobile phone casings for three years before leaving in March to join a Chinese NGO (non-governmental organization). When she started at the factory in 2009 she was making 700 yuan as a base salary. That climbed to 900 yuan the following year and 1,160 yuan by 2011.

With overtime, however, workers were generally earning 2,300 yuan a month, Xue said. But to do so, she said, they had to work 12 hours a day throughout the month.

During her time there, Xue assembled and inspected phone casings for Samsung, Nokia and Research In Motion. In a single day, she would look over 4,300 to 5,600 casings, her job sometimes to check if the ID stickers behind a phone casing were properly placed.

"Workers didn't understand what these components were for," she said. "You are making this product over and over again, but you don't know what it does."