Refer to the PDF data sheet for device specific package drawings
The PCIe data signal traces must be routed to achieve 100-Ω (±10%) differential impedance and 60-Ω (±10%) single-ended impedance. The single-ended impedance is required because differential signals are extremely difficult to closely couple on PCBs and, therefore, single-ended impedance becomes important. These requirements are the same as those recommended in the PCIe Motherboard Checklist 1.0 document, available from PCI-SIG (www.pcisig.com).
These impedances are impacted by trace width, trace spacing, distance between signals and referencing planes, and dielectric material. Verify with a PCB design tool that the trace geometry for both data signal pairs result in as close to 100-Ω differential impedance and 60-Ω single-ended impedance as possible. For best accuracy, work with your PCB fabricator to ensure this impedance is met. See Table 8-23 below.