Sunday, July 6, 2014

How to etc PCB

Just few hours back , in Mumbai we had a very warm eyeball qso with OM Cyril and OM Sudhir bhai shah and OM charudutt.
In the island of shops I was not able to find the copper board but VU2UPX led me to the visha electronics on the third floor off lamington market on main road and I had my second big copper clad board after a two decades. first time I bought big copper board from Ahmedabad. ok, glass epoxy cost me around175rs/-, normal phenolic is 75/-. size is 1 foot by 1 foot.
I had used first copper board for making the VU2ATN 20 meter transceiver with mc1496 double balanced mixer. zeroxed the ckt layout from EFY magazine. Then to make it transparent applied oil to the papers and let it dry. then with the help of pensil and carbon paper traced it on copper board. Now, ball pens ink was used to mark the traces by hand. when it solidified after some time and tracks were visually checked with EFY magazines original layout. I finally put the pcb on a small lunch box poured some water and then goes the ferric chloride may be two or three table spoon. then let it eat the extra copper and atlast finally after an hour the copper board was taken out. seen that everything was done properly. satisfied, washed with water. then with the help of soap and kerosene it was cleaned. finally I got my firs etched pcb.
This is a very old tech. So, I feel at liberty to ask my junior hams but very seasoned in this etching pcb to help me out with latest techniques and here comes the reply from my friend JAYDEEP BANERGEE (VU3JOJ )I have seen he has made very good pcb better then professional quality.
with his permission , I reproduce his reply. Let it be verbatim. I hope it will be helpful to my friends. Foe any queries and question please call him up directly. He will be willing to help you out. He is available on gmail and facebook. thank 3joj.


For a professional look of your pcb I suggest you to follow what I learnt at my university of life.

  1. first clean the surface of the clad board with soft scotchbrite. Do not press hard. You do it to remove the weather coating of the copper board.
  2. Then clean the copper piece with soft cloth or tissue paper by pressing hard. The cloth/paper will become black. Then moisten another clean cloth with (no tissue paper) Acetone (if not available use spirit) and clean again until no black spot come on the cloth.
  3. Before preparing the clad board (step 1& 2) you have to print the negative on a thin photo paper by tuning the laser printer in darkest mode. You also have to turn off the page scaling buttons of printer properties. Use photo paper because toner is not glued to this paper. If it is printed on a normal paper the image will be permanent and unfit for transfer on copper.
  4. Now follow step 1 & 2. and place the negative on the copper clad board. Fix it with paper cellotape at corners to prevent displacement while ironing.
  5. Now heat your iron to its full capacity. Place the copper board under a layer of a thick cloth ( I use my worn out denim). Remember the surface must be smooth for ironing.
  6. Now the main secret. Do not iron initially on the paper side. Put it in up side down position under the thick cloth. Press iron hard for 30 seconds. Now reverse it ( put the paper side top). Iron light for a minute. Stop for 30 seconds and then again iron for a minute.
  7. Now keep the board on the thick cloth and iron directly with light strokes until you see the pcb tracks.
  8. Left it for cooling. Do not dip in water. Try to peel off the paper gently. Now the whole toner is transferred to the copper. The paper is absolutely blank.
  9. Using a magnifying glass examine the tracks and if you find any paper residue wipe out with a soft brush. If you find any track missing or broken then paint with Erase X Pen ( permanent marker will not work)
  10. Now dip the board in FECL3 copper side top position. Always cradle the container lightly until unwanted copper wiped away.
  11. Clean the board with plenty of water. Do not drain the fecl3 solution. Keep it in a glass container with big mouth. For next etching just add little fecl3 and it will work. It is also illegal to drain fecl3 in foreign countries. There is scientific procedure to dispose it off.
  12. Now wipe the board with VIM dish washer and scotchbrite until it is shining. Then dry it with a cloth and again wipe with acetone or spirit. Then spray ACRYLCOTE on it and leave to dry. Then spray the same on the reverse side olso.
  13. Drill holes. See my homebrew drill on facebook wall.