Homebrew PCBs

Hi Mike,

>Les, I agree that that is the ultimate method of making PCBs 
>but...you forgot to mention follwing problems:
>1. You must have a good UV exposure box-- let's not start another 
>dicussioon today what that means. It is not a trivial issue although 
>for some it might be.
>
I have no problems with a very basic setup. I admit I tend to stick to 
12 thou track/gap because I know it will work every time. For one-offs 
size isn't usually a problem so you can afford to space things out a bit.

>
>2. Once you have the box you need to calibrate the bloody box and 
>depending what light it uses the timing might be all over the map, 
>depending on the preheated condition of the lamp. Depending on what 
>you are using. Calibration alone is not for weak people either.
>  
>
Leaving the box on for 10-15 minutes before use solves the warmup 
problem. Calibration is a little tedious but it isn't exactly difficult. 
You only have to do it once.

>3. PCB material: buy ready made (expensive),
>
Ready made works for me. Yes it is more expensive but not that much more 
expensive. In the small quantities most of us use the increased cost is 
not going to make a noticeable difference to the overall cost of 
building a circuit. The quality of ready made does vary quite widely 
between different suppliers. Mega Electronics for instance sell two 
different types, Microtrak and Fotoboard. They are both near as dammit 
the same price but the Microtrak is miles easier to use.

>Now, I am waiting for someone to say that he is happy with scratch 
>and etch or printing directly on copper!
>  
>
I used to plot directly onto copper but I had problems with the ink 
spreading. One method that did work, and you are gonna laugh at this 
one, was to plot onto photoresist board then expose and etch. The ink 
didn't spread on the photo resist. Exposure time was whatever you 
wanted. Anything from 5 minutes to 30 minutes gave good results. 
Printing onto film is a lot quicker than plotting so I use film these 
days. I like the idea of scratch and etch. One day when I get the right 
software and a few spare hours...

>Overall, I know that UV is best, and I know it works fine because I 
>have the whole process prepared when... when I get tired of TT-ing 
>PCBs. So far I don't foresee it. Stick a secret Staples paper in the 
>laser printer, hit 'print' and pull the paper out of the printer. 
>etch it and remove the paper. Then you drill.  No adjustment process, 
>no secret uv boxes.  Mike
>
>  
>
Your experience with TT must be very different to mine. I spent a cople 
of days in total trying to get it to work and never ended up with 
anything useable. I have a big stack of assorted papers bought from 
Staples and other suppliers. None of them worked reliably. Distortion 
was the final straw. If I got the cnc lined up perfecly on one end of 
the board it would be missing pads completely at the other end of the 
board. Maybe my Samsung laser was the problem. I don't know. I'll stick 
with what works for me :-)

Les