I assume you are using "positive" acting resist, where the
exposed portions of the resist become soluble in the developer.
If you experienced incomplete developing then it sounds like your
13 minute maximum test was still not long enough. From my
experience with positive resists, the unexposed resist will still
dissolve in developer after extend period of time. Normally this
time is significantly longer than the time it takes for exposed
resist to dissolve, so the resist image can be left on the PCB.
Before testing with artworks, simply expose pieces of photoresist
coated PCB and compare them with unexposed pieces. Try placing a
piece out in the sun for 20+ minutes to guarantee full exposure,
then compare that with unexposed piece.
Once you get a ball part figure of the exposure time, then you
can refine it with the stepped method you did earlier.
Adam
tboneuk_2000 wrote:
> Hello all,
> Wondering if anyone could point me in the right direction.
> To find the correct exposure time I made up a strip of inkjet
> transparent film with 10 identical dill sockets plus some lines,
> placed this over a strip of "fotoboard 2" board (with glass holding
> it all together) and placed it under a 2∗ 8W uv light for between 4
> and 13 mins (uncovering each dill socket every minuite). I made up
> the developing solution ratio 10:1, and placed the board in a glass
> dish containg developer.
> After about 1 min I started to see my image appear on the board and
> a bluish residue around the exposed print. This seemed ok but did
> not develop any more as left it in the solution for a couple of more
> mins, then the print slowely started to dissapear to nothing. I
> tried etching anyway but all I got was a nice clean board striped of
> all copper and no tracks/sockets at all.
> At least I know how to etch the board but I am confused why the
> image started to develop and then dissapeared.
>
> In case it helps I used fotoboard 2, pcb developer and pcb etchent
> from maplins ( the products are made by chiltern and I had a 1:1
> ratio of etchent to water)
>
> Any help graetfully received
>
> Kind regards Tbone
>
>
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