On Sun, 19 Feb 2012 11:45:39 +0000, you wrote:
>On 19/02/2012 03:20, Terry wrote:
>> Joe, I think your results are more the exception than the rule. I have
>> been able to get down to 8mil traces with the Pulsar paper, and just as
>> good with the HP Presentation paper.
>>
>> The problem with the photosensitive steps is there are just too many
>> chemicals and steps involved for it to be quick.
>
>
>All that is required is some developer (I use NaOH), in addition to the
>etchant. Hardly "too many chemicals"!
>
>It takes me something like 20 minutes to make a board using photo-etch.
For the quantities of board I use, if I had access to good
photosensitive board in the sizes I need, I'd use it. That is, if it
were cheap enough. I can get (locally) single sided 0.23 inch PCB
which is ideal for making double sided boards. For some reason, I
seem to make double sided more than single sided.
My problems in photoetch are not the developer, nor the exposure (made
a vacuum frame and use an enlarger timer), but the density of the
positive. Neither the laser nor the inkjet seem to do quite a good
enough job so far. Exposure therefore is tricky. I do miss kodalith
a lot.
I don't miss the tape, though.
I could even do negative photoresist (I think) by going to persulfate
etchant (see previous posts) and tin/lead plating before the etching,
which would work for the negative photoresist process. (it's what the
old PC board houses used to use, and perhaps still do).
Right now, with CuCl etchant, a 4x6 board will cost me about 4.50 to
do, and with persulfate, perhaps 6 dollars.
4x6 double sided photosensitized is way more expensive than that, and
there's no "redo"....
Not unless I invest in trying to put my own film resist on.
Harvey
>
>Leon