Needs a Haswell CPU (fourth generation; parts start with 4). There may be limits depending on the form factor of the system -- the smaller form factors have more limited power and cooling than the desktop or tower systems do.
The 3020 only shipped with i3 and i5 CPUs so there were no i7s validated to work with it, and therefore wouldn't be supported. However, that's not to say that an i7 wouldn't work, the chipset itself (Intel H81)
supports the following i7 CPUs:
As ejn63 says, you will also need to consider the power and cooling aspects. If you are going to go ahead with an upgrade, make sure to update the BIOS beforehand:
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