Homebrew PCBs

Adam Seychell wrote: 
> 
> I have no desmear removal step. Never had an inner layer electrical 
> problem yet. 

Maybe i didn't explain with the right English words. Etchback is used to
from etch resin sidewalls of holes in order exposing a copper anular
ring of innerlayers. There are good images on the web to explain this
but i didn't find any good right know, choose this because is Australian
and has other useful content
http://www.precisioncircuits.com.au/cid/011.html
on bottom 'etch back hole' but not easy understanding 
This is used to improve surface contact between plated copper and
innerlayers and should be used. For double sided board desmear or good
cleaning with air compressor or high pressure water on the holes is good
enough but it surprises me you could do it without even desmear for
multilayers, but just proves your genius skills again.

A good easy to use and maintenance free homebrew plating chemistry,
should not require high temp bath to be always ready to use or
incompatible consecutive baths for avoid long water rinses and its
disposal, and bath longer life. I don't like either microetch. So have
decided for palladium based. Palladium tin colloid with vanilla to
improve tin stability. The one i have used from bungard from what i know
now is like this and uses NaCl instead of HCl for Pd/Sn suspension i
guess to don't attack copper. The next bath is K2CO3 which removes
vanilla and with it tin and salt leaving only the palladium bonded to
resin surface. Or at least is what i can understand. 
It uses a mix of MEA and PEG600 (not really sure) for desmear at 60�C
with slow 3hour heat time. And a 25% NaCl and 1% HCl bath because of the
incompatibility of the desmear and the activation. 
I would like to make my homebrew version of desmear with a acidic
version compatible with the activation, i would love to use sulphuric
acid with EG antifreezer or DOT3/4 brake fluid for desmear but i can't
be sure it will work and it affects the bath compatibility. But the
K2CO3 at 40�C bath i don't know any replacement so it still requires a
water rinse and heat time here before the plating bath.
Your genius developing tank with nylon brushing fabric answered me
numerous ideas. Using it with NaOH as a degrease cleaning instead of
manually scrubbing is a saver way and time saver (no hands on chemicals
or gloves necessity), followed by one acidic desmear can de-oxidize the
board also, and be a bit more compatible with the activation.
My question, can you comment/help/improve the compatibility between this
NaOH degrease -  H2SO4 desmear - Pd/Sn organic activator - K2CO3 'salt
remover' - H2SO4/CuSO4 based plating, to minimize water rinses, heat
time, compatibility (residues from one bath don't affect next one) ? I
hope to have all this and be doing it in February finally.


> I think because professionals use 100k+ RPM drill speeds 
> there is much more probability of epoxy smear. My home made manual
> drill press runs at 15k RPM max.

I already suspected that you was able to do pth boards without a cnc (or
desmear) but is breath taking know that you said it...  Congratulations
i guess... Don't know what to say.

About drill speed, it's not that fast, and depends on drill diameter, a
0.5mm drill is recommended to run at 60.000rpm, 100krpm are for 0.2mm or
so, but a 2mm should run at 20krpm. But there are under 0.1mm drills and
above 200krpm spindles (high pressure air bearings). Pcb laminate
manufacturers say something about 'drill surface speed per minute' but
my few experiments with a 30-60krpm spindle said faster is not necessary
better. Maybe is just a recommendable limit speed and not recommended
speed.
http://www.isola-group.com/images/file/ISOLADE104iPGOriginalRelease3608.pdf
Check this file is from a common used laminate here in Europe, the file
has speed drill tables, and a pressure/temp vs time in multilayer
press. 

> 98% sulfuric is an excellent epoxy etch. In hot H2SO4 for few hours 
> your can remove all epoxy and just have nothing but bare copper
> traces.

Hot sulfuric acid shouldn't etch copper too?



Thanks.