As a kid I re­mem­ber find­ing mar­velous glis­teny ma­te­r­ial at the cen­ter of dis­carded mi­crochips. I wanted to look at some­thing man-made for this year’s SEM com­pe­ti­tion, so I sac­ri­ficed an SD card to find out what’s in­side.

The outer shell popped off with a lit­tle co­er­cion from a nar­row screw­driver to re­veal two mi­crochips on a flimsy printed cir­cuit board:


I was sur­prised to see that the write-pro­tect switch does­n’t have any con­tact with the in­ter­nal com­po­nents of the card. Its po­si­tion is read ex­ter­nally and must be re­spected by the card reader.

The two mi­crochips tore of eas­ily. The larger chip is the NAND flash mem­ory, and the smaller chip is the SD con­troller:

Chips removed

The con­troller did­n’t last long against a duo of nee­dle-nose pli­ers:

Controller chip

At the cen­ter is a shiny in­te­grated cir­cuit:

Controller chip core

The NAND mem­ory chip con­tained a more uni­form mesh that re­sisted crum­bling, kind of like minia­ture re­bar:

Flash memory chip

With only two hours at the SEM and other sam­ples to ex­plore, I only man­aged to take two im­ages of the SD card. The first is a dis­ap­point­ingly blurry im­age of the NAND flash mem­ory at ten thou­sand times mag­ni­fi­ca­tion, show­ing a larger grid formed from fine fil­a­ments:

NAND memory

The other im­age, at only eight hun­dred times mag­ni­fi­ca­tion, shows the thresh­old be­tween the in­te­grated cir­cuit and its con­nec­tions through the en­cap­su­la­tion: