A design method for an integrated circuit adds spare cells in a System-on-Chip to allow for Engineering Change Orders (ECOs) to be performed at a later stage in the design. This method can be used to provide a second version of the chip having minimal alterations performed in a short cycle time. The spare cells can be divided into combinational and sequential cells. There is an optimum spread of combinational cells in the design for post placement repairs of the chip with just metal layer changes. The method takes into account the drive strength of the spare cells as the main factor in their placement on the chip.