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Peroxy-Sulfuric Etching Module
Operation/Etching a printed circuit

Etching a printed circuit

Copperclan in board clamp
Fig. 5
  1. Put the board in the etcher and etch for T/2 minutes.
  2. Pull the board from the etcher, flip it top to bottom and left to right, and etch for another T/2 minutes.
  3. Pull the board from the etcher, thoroughly rinse in deionized (or distilled) water and carefully examine the etched pattern for shorts or incompletely etched areas.
  4. If you find, small isolated shorts, but the rest of the board looks pretty good, etch the board for another 30 seconds and re-examine. If the shorts persist, it might be easier to remove them with a razor knife or other implement of destruction. If shorts seem to occur in localized groups, and there are no signs of resist failure, etch the board for another minute and re-examine.
  5. Continue in this fashion until the etched circuit is totally free from shorts and other defects. Be careful, however, not to over-etch the board. It is generally easier to cut away a few shorts than it is to rebuild traces that have been totally etched away.
  6. Once you are satisfied with the quality of the etched image, thoroughly rinse the board, first in deionized water, then under cool tap water.
  7. Immerse the board in a heated (50°C) 5% solution of sodium hydroxide. After about 2 minutes, the resist will start to lift off of the copper. Swish the board around (or scrub it with a lightly abrasive pad) until all of the resist is removed.
  8. Rinse the board under warm tap water and blow dry.
  9. The etched board is now ready for further processing.
If the total etching time is more than 20% greater than T, it might be a good idea to conduct a chemical analysis to see if any of the bath components need replenishing.

If you initially mixed your etchant without adding copper sulfate, you may find that the etching time decreases until the amount of dissolved copper approaches 5 oz/gal (36 g/l) at which point the etching time and the quality of etch will stabilize and become more predictable.

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