[chbot] PCBs update
Russell & Heather Phillips
heathruss at snap.net.nz
Wed Oct 21 20:57:56 BST 2020
I forgot a few thing on making pcbs:-
1/ Taking the PER-20 coating off the board after etching immerse in a
strong solution of NAOH, caustic soda (drain cleaner from a hardware
store) dissolved in hot water, leave a while and the coating lifts off.
Also instead of using DP10 developer to develop the board use a weak
solution of NAOH dissolved in water at 25 degrees C, the unhardened
resist will change colour and come away, rub with a small piece of rag
or a brush to finish off, then run under hot water.
2/ Drilling, you can drill the board before taking the resist coating
off or after, please your self, I leave centres in the pads as a guide
and use 0.9mm high speed drills maximum speed in my mill on the Emco
Maximat Mentor lathe, sticking out of the chuck as long as possible so
the drill can bend to find the pad centre. (if you use cobalt pcb drills
they brake with this treatment so need to be used in a CNC machine),
then I open the holes out to the required size. The small drills wear
out caused by the glass in the board so I buy them from RS and they come
10 in a pack.
3/ Cutting, I use my PCB guillotine and run over a piece of sand paper
to finish, pcb is excellent to mill or turn in the lathe.
4/ I coat the boards with Rosin to stop tarnishing before I use them.
The Rosin was bought from a chemist 50 years ago and I tried to buy more
but they didn't know what I was talking about so now I wash the boards
populated with 2 Way thinner, then I pore the wash into a small jar and
let it evaporate. the rosin is then used again by putting in the coating
jar, in this jar the rosin is dissolved in meths adding more when
needed. I dip my finger
in and rub the rosin on the boards.
5/ Finally I was using CRC plasticote 70 to protect the boards but I
am not sure if it is now available, so I use one from Jaycar.
6/ At the moment the art work is done on Sprint Layout, bought a few
years ago from Australia $50.
from the Domino house.
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