I’ve been working with the BeagleBone Black and discovered today that I had a bad SD card. Not only could I not access it, but it was also getting hot. Instead of just throwing it away, I decided to do what any other curious person would do – I removed the solder mask so I could get a look at the layout.
These devices are basically just PCBs with flash memory molded into the substrate. I do a lot of PCB layouts, but this was particularly impressive to me, given the trace/space distance and the free form trace routing. Due to the transfer speeds and layout requirements some of the traces are probably length-matched, which would help explain the routing. Also, this is done in a very restrictive form factor.
I got some images with my digital microscope, so you can really see the detail.
MicroSD Card PCB Layout Detail
MicroSD Card PCB Layout Detail
MicroSD Card PCB Layout Detail
MicroSD Card PCB Layout Detail
MicroSD Card PCB Layout Detail
MicroSD Card PCB Layout Detail
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