You can try 'sudo mdutil -i off /Volumes/microSDCardName' which will disable Spotlight indexing on it. While a Spotlight index of an empty disk shouldn't cause overheating...there's bugs somewhere in the chain. To say nothing of quality issues on the cards themselves. I often use an app called Disk Arbitrator[0] to mount disks read-only or block automounts when I'm dealing with SD cards because of overheating issues.
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