h a l f b a k e r ycarpe demi
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Following on from an annotation in the linked post.
If dust is a problem in cleanrooms (for microprocessor
fabrication), simply run them under a fairly hard vacuum.
Dust particles of any size will settle out in a rapid and
Newtonian way under vacuum and, with no air currents to
disturb them,
would stay put instead of wafting their motey
ways onto the wafers.
The human operators are already in bunny suits with filtered
air, so a pressure suit wouldn't be too far out of the question
and, in any case, human operators will be less and less
required.
Suggested by:
NexGen_20Clean_20Room
[MaxwellBuchanan, Jul 07 2012]
[link]
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I'm not sure about the state of the art in chip fabs,
but as of a decade or so ago, several processes still
involved liquid. Definitely for board fabs solder
pastes and adhesives are common. These would not
do so well in vacuum. |
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[mechE] you're probably right. |
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The alternative, then, is to stick with atmospheric
pressure but to spin the whole facility up to about
50G. Then dust particles may settle out even in air.
Of course, the people would need a little training. |
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[CaF] has the key point here, I think. |
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That said, I don't think we're talking about assembling mother (or any other close relative) boards - we're talking specifically about "printing" the microprocessor chips themselves. |
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Precisely so. I have seen movies of fab rooms, and
they always seem to have people moving stacks of
wafers from machine to machine, but I find it hard
to believe that this is still the case. |
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//Like a vacuum will suddenly make solder float
away// I think the point was that solder would tend
to boil in a vacuum. Whether that is true or not, I
am unsure. |
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//Are you getting confused with zero G ?// |
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No, I'm talking about the rate of evaporation (or
for pastes, differential evaporation) that would
render various solvents, adhesives, and similar
very difficult to use. |
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//but I find it hard to believe that this is still the
case// |
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That I know to still be the case. Everything in
scoring and making the dies can be automated,
but transferring the wafers and handling filled
spools of the finished product is still largely
manual. |
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...Yeah, but your poor vacuum pumps are going to hate you for producing atmosphere. Just think of how long it's going to take to pull back down to pressure once you flash off a couple litres of toluene or trike or whatever you're using. Gah!! |
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An alternative would be to have a normal air-filled, positive-pressure clean room but to fill it with air from tanks of liquified air. |
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//fill it with air from tanks of liquified air// |
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I don't think there's a problem in getting dustless air
into the room - filters are very effective. The
problem, I presume, is that activities within the
room generate some irreducible amount of dust,
which wafts around before being pulled out by the
filter system. |
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Had better moor this facility tightly to Earth, otherwise it might float away like a proverbial vacuum blimp. Otherwise, [+]; robots can work in vacuum and solder is not used in ultraclean rooms anyway. |
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Solder isn't, but I'm pretty sure various cleaning
solvents are. |
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Also it just occurred to me that some operations in
clean rooms that produce debris are kept clean in
laminar flow hoods. Which means air flow. |
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Soldering would surely work better in a vacuum.
Oxidation would be reduced, and it wouldn't
precipitate much extra evaporation. |
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The issue isn't solder itself (although evaporation of different fractions while in a liquid state would be a problem), but solder paste. Again not relevant for die fab, but the paste is used in board level fab because it dispenses easily. Trying to use that in a vacuum would cause all sorts of problems. |
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