Homebrew PCBs

Markus Zingg wrote:
> 
> As you can see I have 5 bath's. 
> 
> 1 - A cleaning solution (7 minutes) followed by static and spray rinse
> 2 - so called "pre dip" (1 minute)  NO RINSE after this step
> 3 - activation (7 minutes, this is the most expensive one - it
> contains paladium) followed by static and spray rinse
> 4 - intensifier (4 minutes). This bath should transport the paladium
> that happen to stay on the copper sides into the holes also thereby
> avoiding an other wise needed cleaning step of the pcb. Still, static
> and spray rinse is requiered
> 5 - the electrolytic bath (24 minutes) followed by static and spray
> rinse.

You do not mention an electroless copper bath ! If this is 
so then your process uses palladium activation , not 
electroless. Electroless copper involves one additional bath 
containing copper sulfate, formaldehyde plus other 
chemicals. This final bath deposits copper onto all surfaces 
without electricity. After the board is covered with a thin 
layer of copper (usually less than one micrometer) it can 
then be plated at high speed in the electroplating tank. I 
remember Tom (twb8899@...) talking on this group about 
using the palladium process in his PCB shop. Out of interest 
what's the price of the palladium solution ?


> 
> This will produce plates that have 35 u of copper if you start with
> copper plates that have 18u alreay. After this a photoresist is
> laminated on the board. The negative mask is made in a way so as the
> holes are not there, that said, the hole areas do get light during the
> exposion and hence they will not be etched. The developement of the
> photoresist is made with soda. After the etching of the board the
> remaining parts of the photoresist is once more "developped" with
> natriumhydroxid solution.
> 


What type of photoresist are you using, liquid or dry film ?,
Is the photoresist soluble in developer solution BEFORE 
light exposure ? (this is called "negative resist")

How are you applying the resist to the board ?

 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\ufffdC and the stripper (remove all resist) is 
usually 10 to 30g/L of NaOH.

Adam


Adam