Electronics > Projects, Designs, and Technical Stuff
Decapping ICs for investigation.
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bsudbrink:
Actually, it was more like static ram (AMI S4008).  I built a unit (or a replica, depending on your point of view) based on the plans and photographs in the February 1975 issue of Popular Electronics:

http://www.swtpc.com/mholley/PopularElectronics/Feb1975/PE_Feb1975.htm

I exhibited it at VCF East last year and HACKADAY did a little writeup:

http://hackaday.com/2016/04/17/building-the-first-digital-camera/

The problem with still images is that the design duty cycles the pixels but here are a couple that aren't in the HACKADAY article.  The last image is my hand, palm towards the camera, thumb up.

orolo:
I've followed BarsMonster's suggestions and I'm very happy with the results.

First, the test tube method works, using a minimum amount of acid, leading to much easier neutralization and disposal. I baked the remains of my OP07 and a LM317. I think the LM317 die cracked; I don't know if it was overheating or the die was very low quality. The thing was a fake for sure, it had a ST marking clearly distorted. The OP07 die was cleanly extracted. It's a big die, some features like the caps can be seen without magnification.

For the frontal lighting, first I tried a miniature tungsten bulb with a constant op-amp current driver from 0 to 30mA. The filament was projected into the die, so I discarded the idea, and changed it for a white LED. Projecting the white LED through a 15x eyepiece, the results were fantastic.

Here is the whole die, at low magnification:



Here is a lame attempt to build a mosaic from two images. The OP07 marking is very clear. Above it, there seems to be a "Ti" mark. I think this chip is legit, also  :) .



This op amp uses zener zapping for trimming, so looking around at great magnification I found this. Is this a zener zap shunting a resistor?



Anyway, with frontal lighting the doping profiles become apparent, at least for a chip as big as this. For reverse engineering some old analog pieces, a simple binocular microscope plus a regulable LED light could be enough.

Thank you very much for all the suggestions! From now on I'll be much better prepared to spot ebay fakes, something that really bothers me. Examining the die doesn't discard products that didn't pass quality testing, but filters out the worst fakes, and it's a lot of fun. Besides, it's easy.
T3sl4co1l:
Using the thermal method (heat the package until it's soft and pliable), I took this apart:



Sacrificed a salvaged part I'm sure never to need: an ATI Rage Theater 213RT1ZUA43 in rectangular QFP format.  It came from an old Radeon board.

I don't have much of a macro lens, let alone a microscope, so the resolution is only enough to see gross features.  Also, I scratched the die down in the middle, removing some coating or passivation on it, oops.

I wonder if it was polyimide?  It was yellowish and foggy at first.  I decided to try pyrolyzing it; it didn't evaporate at red heat though, only leaving a black coating.  I scraped this off with a stainless steel blade; it didn't exactly flake off, but didn't seem to affect the die.  The SiO2 passivation is hard, but evidently not quite strong enough to withstand my brutish hands, and this is how I scratched it.  Interestingly, I may've felt fine structures on the surface, wiring or trenching perhaps, and I definitely felt the bondwire blobs around the edges.  Impressive just how fine of structures you can feel.  Also, I nicked the die edge by gripping it with pliers, oops.

This particular chip is 2005 era I think, and I would guess looks to be a sea-of-gates ASIC, with some unused "sea" around some edges (top left, bottom left), and the topmost metal layer over it having considerable left-to-right bias.  To the eye, this area looks like a flat diffraction grating; the traces must be very consistently spaced, and very consistently horizontal.  Alternately, the top-left and bottom-left areas might be some kind of memory array, but it seems maybe more likely that's in the bottom-right if at all?  Could also be some kind of processor, although I'm not sure quite how much functionality you can get in that much area

AFAIK, this chip was probably MPEG decoding, so I don't know that it needed all that much memory.  I wonder how many DSP cells it might use, if that explains the right-hand side blocks for example, or what.  The periphery looks to be a fair width, taken up by IO cells of various sorts I suppose, and the bond pads.

Reference:



Tim
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