While searching for the Galaxy Nexus (GSM) breakdown, I came across this unanswered post, so I figured I would do a little research and answer it.
There is no microSDHC in this Samsung device. The storage in the Galaxy Nexus is much more complex as the memory chip has dozens of pins soldered into the main board. and the chip that needs to be replaced on the motherboard is of 32nm design. The most expensive part of this upgrade, which quite honestly will most likely exceed the entire cost of the Galaxy Nexus is the 216FBGA Samsung firmware flasher. I'm quite honestly not sure where you can even buy one, but it will have to read and write (because you will need to create an image the old FBGA you pull out to flash onto the new chip). The upgrade will also require a professional hot air workstation, an adjustable heat soldering iron and probably a desoldering iron, soldering wick, flush cutter, and all the tools required in the Galaxy Nexus Teardown.
So basically the chip that contains the 16GB storage is a 2 Channel K3PE7E700M-XG which is basically 2x K3PE7E700M-XGC1 (8Gb LPDDR2 eMMC). The Samsung K3PE7E700M-XGC1 itself is a 2x 4 Gb low power mobile DDR2 SDRAM module, fabricated in a 32 nm CMOS process. The usage of Mobile LPDDR2 for Internal storage and for the emulated SD card is what makes the Galaxy Nexus one of, if not the fastest booting Android devices.
As for upgrade:
I cannot verify that this process will even work, and at this point is theoretical and speculative. If I had the main component board schematic (PCB Design document), and the design specifications of the larger chip, I could give a more definitive answer as to whether this will work or not. The Samsung chip that is of the same FBGA package (216-FBGA) is Samsung Part Number K3PE0E000M-XG(2) which is double the size of the chip specified in the Nexus Teardown here on iFixit.
As for which chip you actually need to replace, here are some images:
Here is a view of the entire PCB (it is dual-sided but this is the side that has the storage chip). The Internal Storage chip is outlined with a yellow rectangle.
Here is a closer look at the chip.
Here is what you will need to desolder on the reverse side. I have outlined the pins with a yellow rectangle.
So if you have decided to attempt this process and you have obtained all the required tools and the replacement Samsung chip, you need to Teardown the Galaxy Nexus. The procedure for this is in the iFixit Guides located here.
Once you have removed the chip from the board, you will need a Samsung Mobile LPDDR2 216-FBGA reader/writer to save an image of the existing chip. This is where the process might not even be possible, because usually this type of device is write only, and there is no way, that I know of to obtain an image of the entire device. Even Odin v3 is not capable through the Download mode of the Galaxy Nexus of doing this, because the Download mode boot partition is on the Internal storage card, so Odin would not be capable of downloading this partition, therefore is not capable of saving all partitions of the internal storage drive.
There is one other possibility for getting the image to flash the new chip with, and that is by calling Samsung Mobility and Samsung Semiconductor and asking them for the image (and possible resized for the larger 32Gb chip).
Well, if you get to this step, you are surely a master EE, so now you need to write image to the new storage chip, insert the chip to the board, use the flush cutter to cut the excess length off of the 12x12 pins, and then use your hot air workstation to solder the pins to the board. Now it's time to reassemble the device and boot it up. If the device boots, then you now need to resize the partitions. The partition size that you want to increase will be the biggest partition. If you want to expand the External storage (SD card, which is a virtual drive that uses the same space of the main Internal storage partition) and the External storage does not reflect the increased chip size, contact me and I'm sure I can figure a way to modify the emulation size.
Making this modification will absolutely and completely void and and all warranties on the Galaxy Nexus (GSM) device. If you do attempt this modification, I can offer support advice, but I am not at all liable if you break, damage, brick or otherwise render your Galaxy Nexus useless. I recommend that only experienced Electrical Engineers with experience in PCB design (especially High Density PCB [HD-PCB]), circuit board mass production, and circuit and PCB repair. I would also suggest the individual have ample experience with the Android platform, Odin, Samsung/Google Engineering Boot-loaders, Linux, Linux Administration, Linux 3.0 kernels, and knows the intricacies of the Android mobile flavor of Linux as well as the differences between Android (ARMv7a in this case) and other Linux distributions. Please post any results if you attempt this major Galaxy Nexus (GSM) customization, and I hold absolutely no liability if you are to attempt this project, I posted a theoretical process, non-proven, and quite honestly what could be a mission impossible. My ultimate suggestion is to wait 3-12 months for the next Google Nexus Model, I'm sure it will have at least 32Gb of storage.
For documentation, I used the following Samsung Semiconductor links and iFixit Guide to form my theoretical process:
Samsung Galaxy Nexus Teardown