Re: melting through 2901s?

>I've got a couple of Tempest aux boards that have AMD 2901s that seem to
>have been melted through to the chip center. There is a Battlezone aux
>board on eBay right now that shows the same characteristics.
>
>http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=556670453
>
>Is there any reason for this?

I don't think it's a "melting" as much as explosion damage. ;-)

If the die in the chip carrier fails in a sufficiently spectacular way it'll
basically turn into a little space heater. The die area will get extremely
hot (very quickly) and the plastic DIP carrier can't dissipate the heat
quickly enough. The result is usually the carrier "blowing open" leaving a
little crater-shaped hole in the top of the package.

I actually had a 74xx series chip do that on a Pole Position board and it
kept on cooking-- burned the chip down to the leadframe and pretty-much
evaporated about a 2"x1" section of the PCB.

Old process chips (like original 2901's, 74xx chips, I/O driver chips, etc)
used relatively big die at the time, and could actually generate enough
internal heat to fracture the chip carrier. You see "blown" transistors do
that sometimes too-- literally blowing apart...

-Clay
(Yes, a post by Clay. I'm not dead. ;-)
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Received on Wed Feb 7 17:37:17 2001