[sdiy] More about IC design

[Dave Manley]

The whole point of all the test procedures is to toss out a bad part as 
soon as possible.

The cost of a bad part goes up the further thru the manufacturing 
process it gets.  From best place to worst place is something like this:

1. on the wafer before the individual die are cut
2. at die before packaging
3. after packaging
4. after the part is assembled on to a pcb (trust me manufacturers get 
really unhappy if they find your part has a problem after they have put 
it on a board with a lot of other expensive components!)
5. at unit test after the pcb is assembled into a housing
6. at the end customer

There is a lot of science and engineering in making ICs, so that from 
start to finish as few bad parts as possible are manufactured, and that 
the process captures as many bad parts as possible, of course at a 
reasonable cost to the manufacturer.  Some amount of bad parts are going 
to escape and someone will have to pay to resolve the issue, it just 
part of the cost of doing business.   In the end, this is really no 
different than any other manufacturing process, you need Quality all 
through the process, whatever it is you are building, whether it is ICs 
or power cables for synth modules!

There's another whole interesting chapter of IC development related to 
getting a prototype chip back and what you can do to diagnose the 
failure, and to try a fix.  A process known as 'FIB'ing (Focused Ion 
Beam) allows you to basically drill down into the device and do cut and 
jumps.  Try green wiring a sub-micron design!

This is now a long way from SDIY!

-D