Electronics > PCB/EDA/CAD

dry film problem

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5282:
i have big problem with dry film

i buy from china negative dry film.
i use soduim carbonate to developing dry film . after developing i see the copper good

when i put pcb in ferric chloride to etching it. the some pcb area is not etching  because there are an Transparent layer protect copper from etching  " i use a correct layer of dry film i know there is 3layer sandwitch". i try all thing and no solve

are the problem in developer or what ?

sleemanj:

--- Quote from: 5282 on December 01, 2013, 04:44:56 pm ---are the problem in developer or what ?

--- End quote ---

You are not developing long enough.

I use 30g/L Sodium Carbonate at room temperature, developing will take a couple of minutes, I also use an old vibrating toothbrush and gently brush the board to make sure that all the remnants have been wiped away.

When you put the board in the etchant you should see the colour of the copper change to a sort of "pink" that indicates that the etchant has reached the copper, if you don't, then rinse and develop a bit longer.

BravoV:
+1 to above comments.

Also if you're using the blue film instead of the green on like below :



I learned from the Korean's dry film resist instructions, download -> HERE(PDF), its stated during development, its advisable to spray the board with developing solution (sodium carbonate or potassium carbonate) especially there are fine resolution needed, I just used those water sprayer filled with the clean and freshly diluted solution and keeps squirting the board. It works better than without spraying.

5282:
 i try all thing's and no solve  :-[ . it try from 2 month ago and problem is still.
i put my board in developer  along time and no solve .
 i try etching with  ferric chloride and try with hcl  + h2o2 and no solve
here is my pcb picture after putting it in  ferric chloride and  hcl  + h2o2 etching

sleemanj:

--- Quote from: 5282 on December 02, 2013, 09:50:34 pm ---

--- End quote ---

Hmm, you are removing the top protective layer after exposure and before developing, aren't you?  If you don't, nothing's going to happen, it can't etch through the protective layer.

Also see my dry film tips.

In fact after re-reading your initial post, I think that indeed you are not removing the layer.

You have the process working up to exposure OK.  After exposure, you must simply peel off the transparent film on the top layer, then develop it, and etch.

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