Samsung K4S511632D-UC75 SDRAM working when warmed up


Hello all,
I had a problem with an HMI that sometimes doesn’t boot, what we discovered is that if we warm it up by a heat gun for a while and then power the screen, it boots and works perfectly. We then tried to replace it with an available, but smaller in memory capacity, SDRAM from the same family, however, it didn’t work.
Finally, we swapped the two rams and it worked perfectly.
My question is why it worked when warmed up without swapping? and why it worked when swapped without warming-up the rams?

Thank you in advance.


Either bad solder joints, or damaged SDRAM module. Probably the best option is to contact the manufacture, send them the modules and request that they do a root cause analysis, otherwise honestly it will be a guess.