Resurrecting integrated circuits by cooking them.

[dwight]

Failure of the POKEY chip were likely bonding wire failures. Voltage stress failures are not likely to self repair.
I would agree, the fix is likely temporary.
Many early chips used gold wire for bonding but later chips used aluminum. Which is better is always a question. The pads on the die were usually aluminum, while the package was often gold. These are acoustically bonded.
One wonders if one put a capacitor on the lead with a non-lethal voltage and used such a heating method, it might be able to arc weld the wire back on. Using the method of heating might enhance the success as well.
Dwight

________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Pete Rittwage via cctalk <cctalk at classiccmp.org>
Sent: Wednesday, July 24, 2019 6:24 PM
To: Jeffrey S. Worley <technoid6502 at gmail.com>; General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: Resurrecting integrated circuits by cooking them.

On 2019-07-24 13:31, Jeffrey S. Worley via cctalk wrote:
> Yesterday evening, in the process of refurbishing five very badly
> treated Atari 800 computers I had a hunch and subjected a failed Pokey
> chip (Atari Part CO12294 Wikki link https://en.wikipedia.org/wiki/POKEY
>     ) to high heat by way of the barrel of my soldering iron until
> saliva evaporated from it in about 1 second.
>
> The chip, which did not work before in any of the machines now works
> perfectly.
>
> Pokey (see wikki link) is common to all Atari 8-bit computers and
> common in many Atari coinop video game systems.  These chips are
> becoming scarce, so much so there is a sort of replacement being
> manufactured
> https://hotrodarcade.com/products/pokeyone-atari-pokey-chip-replacement-for-atari-arcade-games
> .
>
> The replacement Pokey only emulates the audio portion of the original
> chip, leaving the PotKEY part unimplemented.  Pokey gets its name from
> Potentiometer Keyboard.  It also handles the Atari SIO peripheral
> signals, so without those an Atari computer cannot use standard
> peripherals like serial disk drives, and other common interfaces.
> Thus, for Atari computers a true Pokey is a must.
>
> I stumbled upon a fix for this one and wonder if I reinvented the wheel
> or if this information may be of use to the group in treating other
> sorts of chips.
>
> Reflowing is a treatment for a lot of hardware these days and generally
> regarded as a hack which won't last.  As modern hardware, CPU's and
> video chips in particular run very hot, I can see how this might be,
> but Pokey and most of the stuff we work with don't have this
> environmental restriction.  Most of our gear runs at 40 degrees
> centigrade or lower.  So I'm guessing the problem with my disused chip
> was oxidation within the package and that cooking the chip a bit
> cleaned things up?  Any advise or observations would be appreciated.
>
> I tried this on another chip the same evening, an Antic.  The Antic DID
> work for a second or two, whereas it had before given no signs of life,
> but then returned to its failed state.
>
> Best,
>
> Jeff
> (Technoid Mutant)

I tried this a year or two back with about 30 x SID, VIC, and PLA chips
out of C64's. I heated them in the oven at about 250 for 15 minutes.
None of them showed any more signs of life than before I tried it,
unfortunately.

--
-Pete Rittwage