If you want to remove iCloud from the iPhone, go to Settings - iCloud, disable Find my iPhone, and sign out. It's not stored on the device, so if you wish to get rid of it, there's no other way.
If you're trying to remove the iCloud Activation Lock from that iPhone 6, it can't be done without the iCloud ID and password of the original owner.
iPhone motherboards are assembled by very precise automated assembly robots. Swapping out chips on the motherboard is not practical because of the almost certain chance of damaging the motherboard beyond repair during such an attempt.
Activation Locked iPhones are normally locked for one of two reasons. They've either been reported as lost or stolen and the original owner doesn't want anyone else to access the iPhone.