Is it possible to replace internal memory of a android phone ?
Yes.
Lots of Taobao (think of it as Chinese eBay?) merchants actually offer services of enlarging RAM and internal storage by replacing the chip, and these are actually quite popular, at least around me. Most are for Apple and Xiaomi phones which are popular and often lacking in storage. For example, they could expand the storage of a Xiaomi MI 5 to 6GB+128GB, a configuration Xiaomi themselves never offered.
Here's a very simple search with the keywords "Xiaomi" + "capacity enlargement" (in Chinese):
The internal storage chip (eMMC/UFS) is not an integral part of the SoC, but on most modern phones, it's packaged together with the SoC, often stacked on top of it, as the picture below demonstrates:
(AP≈SoC)
(Source article - also worth a read)
Have anybody tried this out ?
There are several factors preventing you from trying it out, however:
- The tiny size and mass amount of pins connecting the two together means you need professional devices to de-solder and re-solder them. The merchants above are usually situated in Shenzhen in real life - known for flourishing electronic industry, so they are well-equipped for such, but same can't be said for a random DIYer.
- You can't handily buy replacement chips unless you are familiar with the supply chains, and even then you can't make sure what you bought is compatible.
- You also need to load the blank chip with basic data (such as partition tables), which usually only professionals have access to.
Even if you are professional enough to overcome all of this, the stability of the modification is questionable - there are numerous examples of unstable re-solder job undermining the connection, causing the phone to fail. Such mods, naturally, are not covered within warranties, and therefore only you get to shoulder the consequences.
TL;DR: YES technically, but NO realistically.