[sdiy] Re: Possibly quick / cheap pcb service - anyone interested?

[Olav Martin Kvern]

Hi Julian,

I use my CNC machine to make all of my boards and front panels--it gave me a 
great way to get away from using nasty chemicals (and/or board houses with 
unknown labor and environmental practices).

You mentioned clamping--one thing that made a huge difference for me was 
getting a vacuum hold-down unit. It keeps the boards absolutely flat. With 
clamps, I found that the center of the board would always bow upwards, and 
that the height of the board could vary from side to side due to uneven 
clamping pressure. I got to the point where the inaccuracy was only around 
.1 mm, but that's still way too much when you're running traces between IC 
pads.

The vacuum unit I bought cost around $80 US, is about 160 x 210 mm, and 
attaches to a ShopVac (around $40)--I had thought that it would cost many 
times that much to get what I needed, but then I tried searching eBay! This 
thing is great--when the ShopVac is on, it is impossible to move the board.

You can add pins to the hold-down unit to achieve good registration when 
doing double-sided boards. I've only started experimenting with this, and 
haven't yet made a complete double-sided board, but it seems that it'll work 
just fine.

Thanks,

Ole