United Microelectronics (UMC) will soon break ground for the fifth and sixth phase construction of its 12-inch fab located at the Southern Taiwan Science Park (STSP), according to an invitation to the groundbreaking ceremony scheduled for May 24.

Dubbed Fab 12A, UMC's STSP plant reached a capacity of 14,000 wafers in the first quarter of 2012, while the other 12-inch fab located in Singapore (Fab 12i) produced a total of 13,400 wafers.

UMC also has plans to build the seventh- and eighth-phase production facilities at Fab 12A. The foundry has secured a plot of land for the next expansion project.

UMC said previously that its planned capex budget for 2012 of US$2 billion remains unchanged. The majority of the capex will be allocated for advanced 28nm process capacity and 12-inch fab expansion.

UMC is looking to enter volume production for 28nm processes in the second half of 2012, and expects the technology to account for about 5% of company revenues by the year-end.