tboneuk_2000 wrote:
>
> Although it may not make a differance I fliped the film over, so the
> ink faced the board.
> My original trial board was exposed for 4 to 13 mins at 1 min
> intervals, now I tried exposing another board for 12 to 30 mins in 2
> min steps.
> Still not developing, should I see an image of the transfer (even a
> faint image) before developing the board ?
> One thing that may be worth mentioning is that for this second trial
> I used the same deveoping solution that I used for the first (is it
> normal to do this or should I have made anew batch for each
> development)..?
> The original board had an image for few seconds then seem to
> dissapear in the solution, this new board exposed for longer had no
> such image. Could it be I need to expose for a much shorter time <4
> mins ?
>
> Kind Regards
>
> Tbone
I think the makeup of positive photoresist developer solution is 10 +/-2
grams per liter of sodium hydroxide. Are you using that ?
If you cannot measure in 1 g resolution then do this;
Get yourself;
container of 98% NaOH powder (make sure its free flowing powder).
750ml cleaned softdrink bottle with a non-metalic lid.
(fill bottle with tap water about 3/4 full)
small plastic funnel
a pen, and a note pad.
a plastic drinking cup
Go to the post office with the above items. Ask post worker you like to
weigh some powder. Somewhere close to the scales setup the drink bottle
with the funnel in the top. Put cup on scales, and record weight. Pour
between 75 to 80g of NaOH into the cup and record total weight. Carfully
take cup with NaOH and pour into the bottle using the funnel. Some NaOH may
remain sticking to the cup sides so pour some of the water from the bottle
into the cup and then pour back into bottle again. Put lids on and tell
them thank you.
Top up the bottle with water so it has 750ml. Calculate and mark the bottle
with the NaOH concentration. This will be your developer concentrate. You
can now use simple kitchen volume measuring equipment to make up 10 +-2g
g/L NaOH developer. Never resue developer.
Before worrying about exposure times, try as I said before, and expose a
piece of PCB in the sun for 20+ minutes, put some black PVC tape on one
half to block out the light. Then you have guaranteed exposure. Develope
the PCB and see how it goes.