After months and months, and countless hours spent (and a good deal of destroyed Nexus 5 motherboards...) ,I have succeeded in expanding both RAM and storage of a Nexus 5!
I have been thinking about it for quite some time, then I decided to go for it, so I bought a 24Gb LPDDR3 memory chip from Aliexpress and attempted a replacement to my spare Nexus 5. Well, believe it or not, it worked!!! My N5 has 3 GB of RAM, and the difference, with my 242 apps installed, is very evident! It has been hard work, not easy at all, but if there is anyone who has the necessary skill/equipment and is wondering if it can be done, well, the answer is YES!
The memory chip I purchased is the K3QF7F70DM-QGCF.
Replacement requires removing the ePOP memory from the top of the Snapdragon chip, then cleaning carefully the BGA land pads from any resin/glue residue, then re-soldering the new chip. I am not going into details (unless requested) because those who know about BGA reworking know what it is all about and those who don't... Well, don't try it! Anyway, I am available to provide any further explanation.
Then... I could not stop there. RAM is nice, but I was running out of storage space... Plus, it seems it had been done before, even if not many details had been provided... Well, there is all sort of documentation and software one can desire for the Nexus 5... So let's go for it! Let's buy a 64 GB eMMC chip from Aliexpress and let's try to transplant it!
The operation has proven more complex than I could have imagined: I collected 13 (!) dead Nexus 5s so that I could experiment with them, I fixed some of them and then I destroyed them again in the attempt to transplant the chip! The endline is: "Don't try this at home unless you are willing to end up with a broken phone"! And, believe me, it is VERY likely this is going to happen!
But the screenshots speak for themselves:
If anyone is interested (be careful if you want to attempt the mod) I will provide all details of hardware equipment used, how to desolder chips, how to solder the new ones (but if you need to read my instructions then the operation is clearly out of your reach!) and how to flash the new chip with bootloader, recovery, ROM and everything. Just let me know!