SD Card Dissection

I use SD Cards in my HP iPAQ Pocket PC and in my Canon PowerShot A520 digital camera.  The other day (which was a Wednesday), one of my SD cards failed.  I tried all kinds of ways to get it working again.  Luckily, I had copies of all the data on it, or I could easily re-download the stuff.  So then I decided to just re-format it.  That failed, too!

The error I got indicated that the card had a Bad Track 0.  That’s bad. 

So essentially the part of the card that tells where all the other data on the card is was broken.  I couldn’t get at any of the data on it and I couldn’t repair the card.  The card was dead – garbage.  I put a piece of tape over the connections and labeled it so I wouldn't accidentally try to use it.

There is something very important to note… All flash-based memory (flash cards, thumb drives, etc.) wears out.  The technology can only handle a certain amount of writes to the storage medium.  The good brands of flash memory do a better job, but all will eventually wear out.  In fact, many will evenly distribute the writes over the entire physical writable “surface” of the memory rather than re-using the same location over an over (if you delete a file from a card and then write it back to the card) so that one part of it won’t wear out prematurely.

Since it was garbage anyway, I decided to take it apart and see what it looked like inside.  It was a 512 MB SD card from SanDisk.  I got it about a year or two ago from a Best Buy store for about $40 after rebate.  Now you can get 4GB cards from places like newegg.com for about that price.  I’ve got a couple other cards, so I’ll probably wait before buying any more.  I plan to get a 4 or 8 GB card or two to hold movies for my iPAQ.  (I’ll discuss that on a future posting).

Anyway…

First, I took off the sticker in case there was anything under it.  There wasn’t.

Next, I just started bending it and found that it was creasing just past the lock switch.  Then it started splitting open.  It turns out the actual guts of the thing is less than half the size of the case!  I’m not sure if all SD cards (with different capacities) have the same size chip, but it’s now easy to understand how mini SD can have the same capacity as standard SD cards.

So now you know what the inside of an SD card looks like, without having to wreck one of your own!