[chbot] PCBs update

Russell & Heather Phillips heathruss at snap.net.nz
Wed Oct 21 20:57:56 BST 2020

Hi all,

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 
after being

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.


Russell Phillips

from the Domino house.

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