Markus Zingg wrote:
>>Markus Zingg wrote:
>
>
> You are right, I am using palladium activation. The palladium is 200
> EUR per 0.5 liter. That's expensive, but my 2.5 liter tank only needs
> 125ml per load. The remaining part is filled up with the pre-dip
> solution which is a lot cheaper. That said, the 200 EUR palladium is
> sufficient for four loads which last quite a while.
Thanks for the price info. I'd expected that price range. I
remember once a friend looked into doing his own through
hole plating using conventional electroless copper and got a
shock when the sales person faxed him the prices :). You
point out that the economics going down this path yourself
is still small compared to professional made boards, which
is all the matters at the end of the day.
I guess the importnat thing now is to take extra care not to
comtaminate the palladium solution.
There is really no alternative because its not likely your
going to develop your own chemistry and go through the years
of research that the manufactures once did. Its taken
decades for these alternative electroless copper systems to
make it in the industry. If your are interested in the
subject you might like to read;
http://nr.stic.gov.tw/ejournal/ProceedingA/v23n3/365-368.pdf >
> I have to laminate it, then do the light exposure then developp it. I
> used the term "negative" becuase the exposed parts of the film are
> thereafter resisting to the developper and those which are not exposed
> to light will be taken away from the developper.
Yes, that's what people call a "negative" resist.
>
>>From what you mentioned above I suspect your using dry film
>>negative photoresist. Developer of this resist is 10g/L of
>>Na2CO3 at 25~30°C and the stripper (remove all resist) is
>>usually 10 to 30g/L of NaOH.
>
>
> I use 20g/L of Na2CO3
> and later on to strip 15g/L of NaOH
>
The strip solution is not critical, but from what I've read
on all dry film data sheets is the developer should be 9 to
11g/L NaCO3. If the instructions say 20g/L then use that.
For my developing method I pour 500 ml of warm water into a
plastic tray and then add 50 ml of concentrate stock
solution (100g/L NaCO3). I drop in the PCB and gently brush
over with a 50 mm wide paint brush until I can clearly see
all the copper. Then I continue brushing for another minute
just to make sure all the (unexposed) resist is removed.
I've had problems with resist residue if I don't do the
extra brushing. Then the board is quickly rinsed and goes
straight into the etchant. I found the resists can swell a
the edges if rinsed for too long a time in fresh water. Once
the bard goes into the acidic etchant then the resist film
returns hard again.
Adam