Re: Broken TED for

From: Segher Boessenkool <>
Date: Sun, 15 Jul 2012 02:26:32 +0200
Message-Id: <>
On 14-jul-2012, at 19:03, Gerrit Heitsch wrote:
> On 07/13/2012 12:42 PM, Ingo Korb wrote:
>> Gerrit Heitsch <> writes:
>>> Not that I can make out anything that looks like it's the cause  
>>> for the
>>> chip no longer working.
>> The structures at the lower left side, fourth pin from the bottom  
>> look
>> like they may be damaged.

(That's the A7 pin).

> Yes, but that looks to me like something that happened during the  
> removal of the plastic covering the die. Remember they use hot acid  
> to do this. The die only survives that due to the passivation layer  
> (SiO2, meaning quartz AFAIK). Unfortunatly, you can't cover the  
> bonding pads with it so depending on the tolerances the damage  
> there might just have been some acid getting where it shouldn't  
> have gone.

I agree with Ingo, this doesn't look like it is caused by the  
processing: at many of the pads you see damage to the metal, but it  
different.  Firstly, it is closer to the pad opening than you see  
near A7;
secondly, you don't see that black colouration you have at A7;  
thirdly, the
metal on the pad at A7 looks like it has melted (you don't see damage to
the metal on the pad at all at the other pads, except when it has been
physically ripped away).

Some other observations...  This chip has all the pads it needs to  
as an 8500 or 8502 (#NMI, PHI2 out).  The third pad from the left on the
top is not used by any of these chips; it is an output, I'm guessing
this is SYNC.  The chip has pads for only seven of the Pn port bits;
I'm thinking the space for the eighth was sacrificed for the GATE pad
(another P would very neatly fit there).  The driver structure for P5 is
also missing; for the 8500 and 8502, this will have to be different.   
guessing those do not have the GATE stuff and do have eight P pads and
drivers; the only thing in the way for that is a test structure and the
layer indicators ("0234567").

What is different compared to the 6502...  Well, everything really!  The
layout is quite similar, but all of it seems redone in some CAD thing.
All the transistors are resized, many (all?) depletion pullups now use
buried contacts.  All the pins on the 6502 were carefully close to where
they were needed (like on the 6800, heh); on the 85xx not so, so  
there is
a lot of busing inside the pad ring, taking up all the space where the
drivers used to be.  That accounts for most of the chip growth at the
left and bottom.  At the right there is that, but also the added P port.


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Received on 2012-07-15 01:00:14

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