PCB Etching and Sealing

[Bjorn]

On Thu, 4 Jun 1998, Neo Tribal wrote:
> What products/methods would you recommend for this?
> 
> Ferric Chloride or Photoresist?

or? you mean and, I guess. You use the photoresist coating to transfer the
traces onto the board, which is then etched in ferrochloride or some other
etching agent - different agents have different characteristics, I would
recommend ammonium persulfate or whatever it's called, instead of the
ferrochloride. keep it warm while etching and keep bubbles in it, then it
should etch in 5 minutes. 

> And for sealing, what sort of substance is best for coating the traces 
> (or is this not even necessary?)

it's not necessary, and you can't do it yourself anyway. you need a mask
with holes over each pad you're going to solder on. you can't just spray
it on and solder stuff through it. 

> Has anyone ever used those Laser Printer Toner Transfer things? Are 
> those worth the trouble, or is freehand the best way to go?

just print the traces using your laser printer onto a transparent sheet,
then put that and the photoresist board in an UV-box for some minutes.
then you need to apply that stuff which i dont know the english word for,
to fix the photoresist so the parts that were UV exposed, are washed away. 

don't do freehand unless you really want something that looks like shit or
dont have access to any of the devices you need for the photoresist
process. UV-lamps come in millions of versions some cheap some expensive.

if you live in the US, there are several companies who take your gerber
plot from your CAD program and sends you a bunch of professionally made
boards with sealing and everything, I think they go as cheap as below 100
bucks for a bunch of boards. that is certainly the best way to do it if
you can afford it but of course it's not really DIY :)

/bjorn