I have upgraded my Macmini(Late 2012) from 1TB Fusion Drive to 1TB SSD. I bought a Crucial MX500 at Amazon.com and used it for upgrading. 

And I also re-pasted thermal compoud(Artic Silver5).

I wanted a better performance and thermal control. My Mac usually hit over 100 degrees Celsius. So I had to find a way.

When I tear down my mac, I refered to these videos.

I found a trouble to this upgrade process.

That is the Fact, 1TB FD is not 1TB.

Yes, 1TB Fusion Drive is not actually 1TB, but is 1.28TB. So what? I planned to use Restore function of Disk Utility for convenience, but I couldn’t. Because the source drive(Fusion Drive) is larger than the target drive!.

So I changed my plan to reinstall MacOS at MX500 using Install MacOS Mojave.app and migrate from a Time Machine backup. To do so,

A. First, I had to back up my entire Fusion Drive using Time Machine,

B. Second, downloaded the MacOS Mojave install.app at the Mac App Store(it’s over 6GB!),

C. Third, installed MacOS to the MX500,

D. Fourth, replaced the Old SSD to MX500 using Xiomi Screw Driver Kit and re-pasted a thermal compound,

E. Fifth, migrated from Time Machine backup to MX500.

It took about 10 hours to complete these whole processes.

This upgrade makes my Mac blazing fast! I think at least until 2020, I do not need to upgrade my Mac mini(Late 2012) to New Mac mini(2018). When around 2020, I think Intel could do something to current mess chipset process and improve the thermal issue.