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Need assistance with positive resist pcb please

Discussion in 'General Electronics Discussion' started by LKO Railroad, Mar 4, 2017.

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  1. LKO Railroad

    LKO Railroad

    43
    6
    Aug 9, 2013
    I have made many PCBs with MG Chemicals boards, developer, and etch. The results have always been pretty good. All of a sudden I am getting consistent failures. Nothing has changed in my process. I've tried fresh boards and developer but get same problem.

    The boards come out of the developer looking as if they are overexposed. I tried stacking art screens, no difference. I exposed a board for half the normal amount of time and it reacted as you would expect - developing took much longer but ultimately got same result.

    There are odd wave patterns across the boards and large areas of complete washout. My glass is flat and the board is sitting tight and flat against the art. When the art and board are viewed during exposing everything looks normal. The washout areas occur in random places and sizes from board to board.

    For the life of me I can't find anything different from how I have always done this. Any clues?

    (There is some residual water on this board. Very noticeable on the left. Sorry, I didn't dry it well before taking the picture.)

    DSC_1381.JPG
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    What are you using to make the resist layer. The dark coloured parts?
    Cheers
    Adam
     
  3. LKO Railroad

    LKO Railroad

    43
    6
    Aug 9, 2013
  4. Bluejets

    Bluejets

    5,251
    1,101
    Oct 5, 2014
    Not past useby date? This stuff can have a short shelf life.
     
  5. LKO Railroad

    LKO Railroad

    43
    6
    Aug 9, 2013
    You may be on to something however I do not see any date markings on the package.

    Earlier today I developed an unexposed board and got the same results. At least I know my process is not at fault. I am going to contact the supplier.
     
  6. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    I was thinking the same thing, are the PCBs old. I guess the only way to tell is to buy a new PCB and try that.
    Thanks
    Adam
     
  7. LKO Railroad

    LKO Railroad

    43
    6
    Aug 9, 2013
    I received new boards. They expose and develop correctly. Appears I had a bad batch of boards. It dawned on me the bad boards were delivered to my house on a brutally cold day. They sat in a box outside for probably 6-8 hours. I wonder if freeze thaw had something to do with it.

    Regardless, I am back in the board making business.
     
    Arouse1973 likes this.
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