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ELECTROPLATER

The LPKF Contac S4 Electroplating System provides the ability to galvanically electroplate through-holes. Galvanic electroplating is a process by which your substrate sits in an acid bath (in this case, that’s sulfuric acid, H2SO4) along with a slice of the metal that you’re plating (in this case, copper). When a current is passed through the substrate, the liquid, and the metal sheet, copper ions are transported from the copper sheets (called anodes) and distribute themselves onto any conductive surface on your substrate. In a gist.

Critically, what this means is that copper will plate everywhere that there is copper! This means any copper faces of your substrate will get additional copper on them. Astute readers will remember that the internal layer of your substrate (e.g. FR4) is not conductive, so an “Activator” (a conductive ink) is used to coat the inside of your holes with a conductive substance so that current can pass through the holes, and thereby plate your holes.

Electroplater:

• Clean with IPA and a TexWipe before beginning processing.
• If you would like to adjust the plating time, ask a PI to put you in touch with an MPI.
• Do not let your substrate sit in the bath (any bath) for very long after the timer runs out.
• If the machine throws an error on startup, it’s likely a bath needs to be topped off. Get a PI to help.
• After bath 3 (activator):
  • Swipe a “reasonable” amount off with squeegee (mostly just don’t want it dripping)
  • Dry for 20+ mins at 150F. (Higher than this can cause the ink to bake into the copper.)
  • When rinsing after drying (after “bath 4”), scrub the copper surface with a sponge to remove as much of the dried activator off the copper as possible.
• Bath 5:
  • If the current drops to zero or is very low (<10A reverse):
  • First attempt to re-seat the PCB holder (i.e. take PCB holder out and put back onto pegs) and try again.
  • If that doesn’t work, you may need to sand down the PCB holder’s pegs that hold the substrate to the holder (i.e. remove the board, rinse it, and then sand down the holder before restarting the acid bath step).
  • Don’t forget to screw down the holder into place.
• After final bath, dry for 20+ minutes in the oven. * Place a towel underneath the board to prevent reactions between the oven shelf and the copper layers *

What are the different baths?

Why don't we use bath 4?

Is tin plating available?

Electroplater - Device in failed state on startup Potential issue: Baths 1 and/or 2 are low. Lift the lids to baths 1 and 2. If they are low, get a PI/MPI/Staff to refill from the chemical cabinet in the storage closet in the Semi-clean room.

Electroplater - Zero plating current error Potential issue: Too much copper buildup on the PCB holder. Put on the chemical safety gear (apron, goggles, gloves, in that order (Figure 30)) and remove the board from bath 5. Using the drip tray, go to the sink and rinse the drip tray, board, holder, and gloves well. Remove the board from the holder with the allen key. Using a fine-grit sandpaper, file, or sanding block, sand off any copper build-up on the posts and on the metal on the underside. Big flakes of copper may come off; this is expected. Once it looks cleaner, seat the empty holder into an empty bath and screw it down. Get a multimeter. The resistance between either of the posts on the holder and the metal strip that run down the line of baths should be less than 1Ω. If so, re-attach the substrate to the holder, don the chemical gear again, place it back into Bath 5 (and screw it down), and press the play button to continue. If this does not change it, or you are not comfortable doing this, please get a PI. Potential issue: Insufficient contact between the metal pegs in the tool and the metal underside of the tool holder. Make sure that the tool holder is completely screwed down onto the pegs. If the toolholder screws will not tighten further but is not in contact with the rail (i.e. there is a gap between the tool holder and the metal side railings), attempt to re-seat the holder onto the pegs. If that is unsuccessful in solving the issue, don the chemical safety gear, remove the board+holder from bath 5 and, using the drip tray, move to the sink to rinse the board, holder, gloves, and drip tray. Remove the board from the holder with the allen key. Using a wire brush, sandpaper, or other means, clean out the peg holes in the tool holder.

How long does electroplating take?
Between 2 and 3 hours, regardless of board size. This will plate between 8-15 um of copper onto your surfaces. Less than this processing time can cause unreliable vias with variable thickness of the plating.