hello hang19840324!
these are my suggestions:
the ram heat sinks work best with good air ventilation in your cpu case.
the thermal tape used on ram heat sinks were purposely made difficult to remove. they're for permanent attachment purposes. the thermal tape is specially manufactured to efficiently transfer the direct heat from the ram chips to the heat sink. then its up to the air cooling in your case to dissipate the heat.
Is your ram heat sink like this:
Or are they more like
"heat spreaders" 
while there isnt much to be very technically correct on the topic of ram heatsink or heat spreaders, they both have the same idea of trying to conduct the heat from the ram chips, and spread them out and further using the corrugated design of the sinks.
again, ram heat sinks or ram heat spreaders will work best when you have good cpu air flow.
**In my experience so far, we've encountered few defective ram chips -- our desktops and laptops take a good amount of abuse and heat. ive encountered a burnt processor due to a malfunctioned cpu fan, but ive not had any defective ram chips due to overheat/burning. the ram chips that gave out and had to be replaced were due to electrical problems (a curious case of a strong lightning-thunder strike and sudden power fluctuation that killed the desktop's motherboard and ram.)
Shown below is the ideal cooling and air flow for cpu cases. The front of the case may have airflow vents, next to it would be a fan for intake -- sucking cool air from outside of the cpu, and blowing it inside the cpu case.
the first passage of the cool air would be the hard disks, and then on to the ram chips, and then to be further blown and circulated by the processor fans. at the back of the cpu should be an exhaust fan.
It is becoming more common on cpu case designs to include more intake and exhaust vents.
Notice the side fan on the removal panel. The side fan is set as intake to suck cool air from the side of the case and blow it to the cpu processor, ram chips, and video card. The top exhaust vents also contribute to even better airflow.
Of course, having more air vents in the cpu case will suck in more dust and dirt to the cpu. dust filters that come with cooling fans/ cpu cases work best in this scenario. and finally its a good idea to set a schedule to dust and vacuum the cpu innards
good luck, and happy gaming
