Homebrew PCBs

At 11:54 AM 3/22/2009, Steve wrote:
>The plastic would tend to seal down and prevent a good vacuum from 
>being pulled all across the surface,

i've never had a problem with that in over 20 years, but since my 
vacuum tables have a grid of holes across the entire surface, the 
vacuum path is along the entire perimeter of the board.  but i will 
say that professional screenprinting exposure machines have a piece 
of string about like a venetian blind cord anchored near the vacuum 
outlet hole and this is laid across the substrate out of any artwork 
path and acts like a wick or 'tunnel' for the air to escape during 
the pump down. these professional machines (i own several different 
kinds) have a highly flexible rubber blanket that pulls the substrate 
against the thick rigid glass. Oh, i also use a vacuum pump from an 
old offset press, but it'll take a decent time interval to wear out a 
motor in a shop vac and you can find them cheap all the time in yard 
sales/goodwill stores.


William Alford

GI Motility Medical Research Page
http://alford.grimtrojan.com/  

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