How to expose CPU die?

[Jd007]

I have a spare Athlon X2 CPU which is old, and I want to take a look at its real CPU die, like in this die shot.

However, if you've seen any mobile CPUs or desktop CPUs with the IHS removed, you'll know that the die is actually covered by a layer of black insulation/protective material. I tried scraping it off with a previous attempt to expose the die (another Athlon X2 CPU), but it didn't work, and completely ruined my processor.

Is there anyway to remove this layer of material and expose the beautiful semiconductor die itself? Perhaps through some chemical process (like dipping it in some sort of corrosive solution)?

I obviously don't expect the CPU to be still usable after; I just want to see the nice colorful silicon for real.

 

[PottedMeat]

I believe what you're looking at with the IHS removed is the bottom of the die. The top faces down on the carrier with solder bumps to contact the breakout traces to the pins/lands. You would have to heat up the die to get it off ( assuming the filler comes off easily ), then either lap it with a very fine abrasive or etch it with hydrogen fluoride.

There was a user CTho something that did that, he even put up some photos.

My suggestion is to just get a 80186 or 80486 with the metal plate covering the die. These were mounted face up with gold wires ultrasonically bonded to the die then jumped to the lands on the ceramic carrier. You can easily remove the metal plate with a soldering iron or with careful use of a torch.

edit: here's CTho9305's thread about die deprocessing - http://forums.anandtech.com/showthread.php?t=180048&highlight=ctho+etch

 

[Jd007]

Thank you PottedMeat. I'll try it when I get some time.

 

[Dr. Mcbudstoke]

i agree with using an old cpu like a pentium. I know for a fact that the die is mounted with the etching exposed - i've removed the protective metal plate before. plus the process is larger so it might be easier to see.

 

[Red Squirrel]

haha I remember breaking a 486 to see the die. I'm guessing it's not as easy now given the die is way smaller and such.

 

[Colt45]

Yeah, modern CPU's are all flipchips.. the die is upside down.

Here's a shot of a pentium1 and a pentium pro I have... one die is cache, the other is the CPU. I broke the P1 opening it, lol.. this was years ago..

But for all the hassle, you can get junk wafers on ebay for pretty cheap. eg:

 

[Jd007]

Yeah but junk wafers don't have the correct CPU etching on them. I have old Pentium's exposed die, but want to see the newer architecture. They are prettier lol.

 

[Colt45]

blank wafers dont. botched, outdated, or for some other reason unusable ones do.

 

[CTho9305]

I believe what you're looking at with the IHS removed is the bottom of the die. The top faces down on the carrier with solder bumps to contact the breakout traces to the pins/lands. You would have to heat up the die to get it off ( assuming the filler comes off easily ), then either lap it with a very fine abrasive or etch it with hydrogen fluoride.

There was a user CTho something that did that, he even put up some photos.

My suggestion is to just get a 80186 or 80486 with the metal plate covering the die. These were mounted face up with gold wires ultrasonically bonded to the die then jumped to the lands on the ceramic carrier. You can easily remove the metal plate with a soldering iron or with careful use of a torch.

edit: here's CTho9305's thread about die deprocessing - http://forums.anandtech.com/showthread.php?t=180048&highlight=ctho+etch

I recommend just using sandpaper instead of glass etching paste. You can get up to 2000 grit at an auto parts store.
1) Nothing to splash, and nothing dangerous to dispose of.
2) It's much easier to control what metal layer you're removing. That said, even sanding got progressively more difficult on more modern processes.

I wrote a newer post here when somebody else asked about it recently: http://forums.anandtech.com/showpost.php?p=28930136&postcount=6.