Resurrecting integrated circuits by cooking them.

[Brent Hilpert]

On 2019-Jul-24, at 10:31 AM, 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.

> ...

> 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.



.. cross your fingers that it stays working. I performed a fix like this some years ago with a ca.1970 chip from an SSI logic family from Sony. However, it reverted to its failed state some weeks or months after the heat application, long after (obviously) the chip had returned to ambient temperature. So it wasn't merely that the chip was temperature sensitive, the heat application indeed must have had made some internal alteration, but it wasn't permanent.