Homebrew PCBs

>> Adam Seychell wrote:
>> I found that to get anything close to 8mil
>> (0.2mm) features, you need a much better
>> collimated light than an array of fluorescent
>> 'BL' tubes.

> derekhawkins wrote: 
> 8 mil is a walk in the park with or without
> collimation provided you're using a contact
> frame. Less than 5 mil may benefit from it but 
> by that time you've hit the resolution
> limitations of the inkjet printer.


I agree that 8/8 is quite do-able with a contact
frame and UV tubes.

However - what I am calling 8/8 and what others
call 8/8 may differ.

I think that I have sucessfully made an 8/8
board if I can get 150mm x 300mm pre-coated PCB
to have no shorts and no breaks across a dense
area of 8 thou tracks and 8 thou spaces AND
still be able to see that with my luxo desk lamp
that the lines all look like they have straight
edges and that the track thickness does not vary
to greatly. (i dont use a microscope just a
magnifier)

Some people might claim that the optical and
chemical undercut that makes my 8 thou tracks
realy be 6 or 7 thou in places be a failure.

It's all up to what you call a success i guess.

I do agree collimated light is a big advantage.

I am going to build a good collimated source
one day.  But for now I think I get reliable
8/8 from a Kinsten suitcase exposure box.

I think better results will come from the
photo plotter (which is still slowly moving
along).  Hopefully I will move to the 6/6
realm when it is done (maybe even 4/6).