Homebrew PCBs

Hmm, this is a good point so it bears checking on.  I currently use 
a clothes iron and press it by hand and use about 5 inches square of 
the sole plate at any one time.  I weigh about 225 pounds these days 
and am pushing down on the iron with a fair amount of force - lets 
say half my weight 112 pounds - which I am sure is more than I am 
pushing down.

5 x 5 = 25 sqaure inches of surface area
112 / 25 = 4.48 pounds per square inch

This has worked very good for me so far (although I suspect I have 
beginners luck).  So, a 12" x 12" board would require

12 x 12 = 144 square inches x 4.48 pounds per square inch = 645 
pounds of presure on that plate for a large circuit board.  This 
would be pretty hard to achieve without some form of mechanical 
advantage (unless I keep putting on weight since I quit smoking!)

Chris






--- In Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
>
> Steve wrote:
> 
> >--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
> ><stefan_trethan@g...> wrote:
> >...
> >  
> >
> >>The thing is, pressure, as in force per area, depends, well, 
like on
> >>    
> >>
> >area.  
> >  
> >
> >>In a fuser/laminator you only have a "line" thus 1-dimensional  
> >>relationship between boardsize and pressure.  In a press you 
have that  
> >>squared, which could be another problem.
> >>    
> >>
> >
> >Very good point. I doubt an electric griddle could stand up to 
much
> >pressure, too.
> >
> >Steve Greenfield
> >
> >
> >  
> >
> 
>   A ton or two may be closer than you'd think off hand, remember 
the 
> rollers flatten out a bit and create a contact patch.  Not sure 
extreme 
> pressure is really important, with correct heat the toner should 
flow 
> without that much pressure.  Reinforcing a plate is easy enough, 
and 
> actually had thought of using a levered hand roller like in the 
manual 
> tile cutter I used last week.  But probably too much work to keep 
the 
> board and print aligned that way..  Just worth investigating a 
bit, 
> since the griddle is useful on it's own for SMT reflow anyway.  If 
it 
> can be made to work it'd be great, if not there is no real loss 
either..
> 
> Alan
>