Homebrew PCBs

>The same would seem to apply to photo resist

Not quite. You print the artwork only once (both sides for double 
sided). You then align both sides and permanently fix the alignment 
of top and bottom transparencies using tape. A lightbox is not 
necessary for the alignment since you're dealing with 
transparencies. This packet is then good for any amount of boards. 
You never have to print or align the artwork again.

You then slide a board in the packet, temporarily fix it using tape 
and expose one side. Flip it for the other side. Remove the tape, 
slide out the board then insert another and so on. When done you 
develop them.

>All that aside, the quality of the artwork would seem to be 
>paramount. The laserjet prints very clean, very crisp edges. Filled 
>areas are very dense black and consistent.

Quite the opposite on transparencies. Take a look here;

http://www.pbase.com/eldata/lasvsink

While the inkjet edges are more jagged this is actually a non-issue 
since with the right exposure time those edges disappear. What you 
cannot see in the laser print is the pin holes and dropouts that 
will lead to holes and pits in the tracks. The same holes and pits 
that are often there after etching a TT board. You just need greater 
magnification in order to see them. The transfer of toner from paper 
to copper is far from perfect.

>The Epson 1280 (28800 dpi) only manages a fuzzy edge,not crisp at 
>all, and not nearly as dense.

Fuzzy edge was discussed above but density of an inkjet print on 
transparencies should always be several times greater than that of a 
laserjet. You need to use Epson inkjet transparencies.

>If both are available, I expect you would choose the laserjet.

No, just the opposite. Furthermore, just about every laser printer I 
have used has issues when it comes to CNC drilling. And this is not 
something scaling can correct since it's inconsistent.

>And if you're printing on the laserjet anyway, why not go straight 
>to the board for the onesie-twosie?

When you magnify the tracks of your TT boards, do you really like 
what you see?


--- In Homebrew_PCBs@yahoogroups.com, "Mike Young" <mikewhy@s...> 
wrote:
>