Homebrew PCBs

On Sun, 08 Jun 2003 09:29:09 +1000, you wrote:

>
>
>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.

Yes, of course. I added covers to all tanks, and take extreme care to
follow the process specifications to the letter.

>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

Very intresting article! Too bad it's quite short on the methods. The
palladium as well as the pre dip bath smell like vanilla - so I FIGURE
my solution uses the Palladium method which mentiones vanilla...

Again, I'm happy that it works now and currently I really don't have
the time to delve into this.

[snip]

>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.

I too use a wide paint brush and do it quite similarly. Intresting
observation with only rinsing it shortly. I will try this and see if
it changes the quality of the final PCB.

Markus