Can I cut an IC?

Question

As far as I understand, the die of a DIP package is located at the center and the rest is just the lead frame. Given that I have unused pins, can I cut the top part of this microcontroller (ATmega16/32)? Will it still function afterwards?

Edit: thank you for all the answers. I have realized that cutting an IC is a delicate process and there is a high risk of damaging the chip. But I've done it anyway, shear cutters worked a treat. I decided to go for the 3 lower pins instead of the upper ones since they are further away from the ISP connector. Here is a photo of the final result (My new DIP-34 package works just fine):

Answer 1

How do you intend to do this butchery?

Unless you have very specialized tools, a Dremel cutting disk or something like that could generate a lot of static charges. Well enough to kill the chip!

Moreover, mechanical stresses could damage the internal bond wires, or even the die. Let alone you would have the bond wires to the cut-off pins protruding flush from the cut side (8 of them), maybe shorted together due to harsh mechanical stresses during the butchering action.

People needing to reverse-engineer a chip do this kind of things, but they use much more "delicate" measures. Moreover, they want to expose the die, so they "cut" off the upper part of the package.

In particular see this video showing LASER decapsulation.

Google for "chip decapsulation" and you'll find tons of references and you'll understand why it is a costly process if you want your die to survive! People pay big bucks to reverse engineer chips (both for legitimate and criminal purposes). Legitimate purposes comprise failure analysis ("Why our top notch IC failed unexpectedly?!? Let's crack it open and see what happened!") or retrieving lost designs ("OK, we acquired this little IC design house with these excellent parts. But, wait! Where are the design sheets of the groundbreaking HQC954888PXQ processor?!? Who fired the design engineers who knew?!?" - Yes these things happen!).

BTW, Did I mention all these methods are delicate?!? Side cutters are not what I could call delicate. When I was a boy I remember cutting a (dead) IC to see the die using a big side cutter: it splintered wildly!

YMMV!

Answer 2

I've never heard of anyone trying to cut an IC package like that, but it seems very risky to me. In addition to the potential for shorting bond wires and crushing the die that Lorenzo mentioned, I would also be worried about the performance of any analog subsystems like internal oscillators and flash memory. Package stress can shift the performance of analog circuits -- even the normal deposition of the mold compound tends to shift currents and voltages.

I have worked with decapsulated ICs and wafers, and I can tell you that IC dies and bond wires are thin and delicate, and are not designed to handle trauma. I'm curious to hear whether your chip still works, but I wouldn't recommend doing this with any chip you actually care about.

EDIT: I got curious and looked up pictures of DIP lead frames. Here's a picture of some DIP-36 lead frames on a reel that I found at a wholesaler's site:

And here's a labeled close-up of the cut side of your package:

Answer 3

Such things have been done at various times for various reasons. If one doesn't get too close to the chip cavity such techniques would be likely to short out an unknown number of adjacent pins but otherwise could work if one uses a cutting device which doesn't generate excessive voltages. There is a substantial likelihood of breaking the hermetic seal on the package exposing the chip to air and moisture, which could greatly hasten failure; I know of no means of inspecting a chip to determine if damage has occurred.

If one can accept a high likelihood of rendering a chip immediately unusable and uncertain reliability after that, such a trick might be usable if there is some particular reason you need to use a particular package which is too large for your requirements (e.g. if a part had 15 consecutive I/O pins, it might be possible to solder the legs of the chip directly to the legs of an LCD without using a PC board). Such designs tend to be rather hokey and unreliable, so cutting the chip might not make things too much worse.

Answer 4

There is no hermetic sealing involved like metal and ceramic packages as the plastic moulding is homogeneous and does not contain an open space that is brazed, soldered or welded closed. The thickness of plastic required for protection is very little, less than 1mm on modern thin flat packs, on a 40 pin DIP it is generous in all directions.

The biggest danger is cracking the casing close to the bonding wires and this is most likely to occur if a pincer or shear method is attempted.

Using low speeds with a coarse abrasive cutter to reduce vibration or using a fine abrasive or abrasive water jet to cut slowly there should be little chance of mechanical or thermal damage.

Using water or alcohol spray, flood or immersion would solve cooling issues in high speed cutting and mitigate possible static build up though a humid work environment might be enough.

A typical 40 pin DIP IC might tolerate 7 or 8 pin pairs removed safely from each end if the internal die size is not unusually large.

In general the plastic ICs are very robust and most static protection on mature components is quite robust.

Answer 5

How barbarous! Even though it was to be expected the chip would still work (provided the surgery is done properly) why haven't you opted for a non-destructive method like a socket adapter or build yourself one using a flat-cable between 2 sockets of different sizes, for instance? While your method obviously works it irremediably damages the IC and makes replacement [almost] impossible.