Dell LGA1155 heatsink uses M3 screw to be mounted on a threaded backplate fastened to backside of 3020 MT motherboard.  You cannot use (1) intel reference heatsink which is a push on type without screws or (2) aftermarket heatsink that has custom backplate. To replace the dell heatsink using a non-Dell option, you need to find a cooler that uses same M3 screw and same mounting mechanism. it would be much easier to just replace the cooler with a standard Dell heatsink fan assembly for LGA115#. [IMAGE] [IMAGE] Example of heatsink that works like Dell. just make sure it is M3 screw. [IMAGE]   otoh you have the option to replace the Dell fan only while keep using the Dell heatsink. That may be a less involved repair project.  The fan can usually be removed from heatsink by loosening some small screws.
Hi guys,  My trusty old 3020's cpu fan is starting to make a bit of noise and I'd like to replace it. Will any 1150 heatsink fit alright or are there special considerations? Thanks in advance! 
OptiPlex 3020 MT CPU fan replacement.