UCC14130-Q1: Layout recommendation

The main point is not to apply any copper pour under the IC (keep out area) for the purpose of maintaining the rated isolation voltage (3kV or 5kV) of the DC/DC module. This is true for the top and bottom PCB layers that are exposed to air and is necessary for maintaining the required creepage/clearance distances as they relate to isolation voltage rating.

If your isolation requirement is much less than the 3kV (or 5kV) rating specified for the DC/DC module, you could, in theory, route or extend copper beneath the DC/DC module as long as you can maintain the required separation distance to achieve whatever isolation voltage you need to meet.

Because the UCC14130-Q1 includes an integrated high frequency transformer, I would not recommend routing signals underneath the IC. Just as you would likely not route signal tracks beneath an external transformer in a traditional DC/DC converter, there is the high risk of coupling noise/EMI into the copper/routing placed beneath any high frequency transformer. 

Regards,

Steve