Should be easy to compare - sand down both the cheapo and a legit one (with a similar datecode) with fine sandpaper, clean with isoprop and shove under an optical microscope - you can then tell how similar/dissimilar the dies are, you don't even have to look for markings or anything super legible, or even sand them to the same metal layer.
Clones tend to be vastly different - different technology node, architecture, die size, etc. - that's because they are generally functional clones, not mask clones.
I have done this a bunch of different times, mostly to resolve sourcing disputes. Dissolving in boiling sulphuric acid/nitric acid will make quick work of most epoxy packaging
IMO, I have mostly seen mislabeling, rebinning, and passing off obvious QC rejects.
> Dissolving in boiling sulphuric acid/nitric acid will make quick work of most epoxy packaging
That's the better method of course (results wise), but it's not nearly as accessible, hence my recent evangelism of the virtues of 2000 grit sandpaper.
I prefer Japanese sharpening stones or those DMT diamond whetstones. It’s relative easy to 3d print a jig that converts a woodworking honing guide into an IC holder and you get a feel for how many passes to do very quickly before slowing down and checking each pass.
I like it. I've used sandpaper to solve some interesting problems in the past as well with great success. I suspect we are only seeing the beginnings here in a trend of high-tech applications of fine grit paper.
I expect it's much easier to acquire fine sandpaper, yet my inner child yearns for laser decapping. (Or I suppose more than "decapping", depending on the depth.)
High power lasers are becoming more and more affordable. Laser ablation is definitely an option but you really want to have some proper fume extraction around that.
I've heard that boiling epoxy in molten colophony for a few hours, like a long-cooked version of rosin potatoes, will also dissolve it. I haven't tried it myself. Colophony is much more expensive than sulfuric or nitric acid, but safer to handle (when not molten) and often easier to get.
These slides from the talk say it only takes 5–20 minutes. I'm not sure it will smell better when you heat epoxy to the specified 320–360°. I'm interested in hearing whether anyone else has tried this.
There was a sandpaper expert in that company associated with sour-tasting fruit which shall not be named. I believe you guys have met, though I think by that time he already pivoted to making the perfect cheesecake.
It may not even be a clone. As the author said, it could just as easily be production line items that were tested and found to be outside of spec tolerances and resold off-label.
Yes, though depending on the product line it may be binned into lower quality parts first. Remember though, the marginal cost of these chips is so small the packaging is usually more expensive than the silicon. They often get tested before the wafer is even sliced up so any waste is hardly worth mentioning until you get into modern processes with large error rates and huge chips like CPUs.
TI isn't patterning $10000 wafers at 3nm with massive chiplets and questionable yield, they are making mostly commodity ICs on cheaper processes - they can afford to discard rejects.
Not only that, leakage goes way up as you shrink the transistors, an ADC on a 3nm wafer would require a complete redesign, if it could be made to work at all.
Clones tend to be vastly different - different technology node, architecture, die size, etc. - that's because they are generally functional clones, not mask clones.
(also, as a general shoutout to the low tech sandpaper technique for exploratory work, here's a sanded down RP2350 thrown under a clapped out SEM: https://object.ceph-eu.hswaw.net/q3k-personal/484e7b33dbdbd9... https://object.ceph-eu.hswaw.net/q3k-personal/3290eef9b6b9ad... )