So I used something like these some years ago to recover data off a phone, but I was wondering if the reverse is possible in having a bga soldered adapter with a microsd slot on top. Or if PCBs can even be soldered together like that. I've never actually checked if bga chips have raised pads or something. The purpose would be for rapidly testing custom firmware for shitty old devices that were designed to be replaced without removing the emmc to flash it separately.
From some chats a few years ago with EEs in the industry, eMMC chips -- as the "e" would suggest -- are embedded on the board and aren't meant to be removed once placed. To program these devices after-the-fact, the prototype units will usually load a header with maybe 6-8 pins, that breaks out the SPI lines and power. Then an ISP device would be used against that header -- with appropriate breakout board -- to load the flash image. Once the image passes final verification, it's given to the manufacturing line to load prior to being soldered down. The SPI lines usually suffice, trading off performance.
In one instance, I have seen a USB-to-SD card adapter that was rewired in a pinch, so that it could read out the image from an installed eMMC chip.
I've seen a lot of single board computers with removable eMMC memory. Many of the Orange Pi boards have eMMC modules.
TIL. Although to be fair, the removable part of that Orange Pi is a modular PCB that happens to have only an eMMC chip mounted on it. It's still very clever as it offers the user a choice in memory size, but it's apparently not standardized by any industry body, at least that I'm aware of.
Plus, if we allow that the loading if a normally embedded chip onto a PCB makes it removable, there's a Ship of Theseus quandary that arises lol
I'll have to look in to this as well. Certainly less scary than my freehand hot air bga rework attempts. Actually I don't know why I never thought of this before. Maybe I was blinded by having access to the waffle press looking thing for connecting unsoldered emmc chips.
The usage of a USB SD adapter hacked in makes me think that my original idea is at the very least not impossible, though admittedly convoluted.
If there are pads that break out the pins to the eMMC, then manually soldering very tiny wires is usually doable with steady hands. If test pads, then a jig/PCB with pogo pins can work.
For really fine pads, then it'll be quite the uphill battle, bordering on whether to even attempt it. I personally miss the days when devices had a MicroDrive or ConpactFlash card hidden inside.