Re: gEDA-user: pcb crooked traces

["Andrew Miner" <andy@xxxxxxxxxxxxx>]

> > FYI -- the largest dimension I ever did on a board was 54 inches.
>
>The largest board I've done in PCB was a quarter mile... I had a "my
>house" element.  It was tiny.
>
>But I was only testing pcb's limits at the time...
>
> > I couldn't say what the standard panel sizes are in the industry,
> > but I could make an effort to find out.
>
>I'm guessing they're around 0.5 to 1.0 meter, based on the size of the
>drill machines...

>To find out would probably require a few calls to some of the larger 
>PCB fab houses.  If the drill machine were the ultimate limit, I 
>would think that would only limit one dimension.  Even if the table 
>doesn't travel enough to cover the whole board, it can be 
>repositioned after the first pass.  But you can't drill further into 
>the board than the machine will reach.  I guess it may not be the 
>same as CNC work, but I've done this with my drill press a number of times.

For flexible PCBs which are made on roll to roll machinery, the laser drills
can make the required holes in a section, and then advance the web (roll)
align to the previous holes, and continue.  If they use a laser imager the
same could be done on that step.  All of the wet process steps are done roll
to roll, so in reality you could make a continuous PCB thousands* of feet
long.  The main restriction is if their equipment could handle a gerber file
that would need to be sectioned into hundreds or thousands of process steps
(instead of their normal step and repeat).

*The biggest constraint on roll length is how thick the rolls of material
are when wound up, since the winding/unwinding machines have a diameter and
weight limit.   

Andrew Miner



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