Equipment/PCB etch station

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Etch station

Important Warnings

  • Do not put any water in the spray wash tanks or the sink at the moment : it will flow straight onto the floor.
  • Do not run any heater unless the tank is full of liquid. It should blow a thermal fuse before melting the tank, but that may involve replacing the heater. Keep unused heated tanks full of plain water until we have disabled the heaters.
  • Do not etch anything except copper (other metals will pollute the etchant).
  • Do not drink the contents, even when there's no beer.
  • Do not allow children or drunken hackers to play with the tanks.
  • Check the power has been turned off after use.
  • Do not dip a basket soaked in one chemical into the tank of another chemical.
  • Read the instructions (pdf)

Less important warnings

  • You normally place boards to be etched in the plastic basket under a tank lid, then dip it into the tank. If the PCB is too close to the open end, it will fall out. You may have to drain the tank to retrieve it. You don't want to do this, so put the pcb well into the opening and don't tip it forwards as you remove the basket from the tank.
  • Very small PCBs may fall through the holes. A possible solution is to put them in fine-mesh envelopes before putting them in the basket. Finding a suitable envelope is left as an exercise for the user.

Status

Working, fully charged with chemicals (ferric chloride etchant) 

There's some spilt etchant on the cupboard floor. Please keep a careful eye on this in case it's actually a sign of a leak.

Solexious reports the air bubbling may be blocked. Needs investigating.

Todo

Next

  • is it OK to install it in the current location ?
  • Fit splashback. I suggest a sheet of roofing plastic (PET from Wickes or similar).
  • There is a stub of 50mm waste pipe heading left from the fitted sink. and a hole in the side of the sink carcase. The 32mm etch tank waste outlet needs to be linked to it.
    • Could extend at 50mm to rear of tank, then a short 32mm section into a reducer
    • Could reduce to 32mm under sink, then 32mm all the way to tank
    • Does the tank system have a water trap inside the cabinet ? If not, we will need a U-bend trap in the linkage
    • Could use simple angled piping or a short flexible section to make access to the rear easier

Soon

  • Scrub out sink
  • Build splashback if possible.
  • Connect waste pipe on back of cabinet. There are some random plumbing fittings in a bag in the cupboard and may be some more in the space, possibly under the lab 24 sink. A length of 32mm or 50mm pipe, a 50 to 32mm reducer and maybe a few other fittings will be needed. A short flexible section or something easily disconnected would be a good idea.
  • Connect cold water to wash tanks. This can probably be done using the tap just above the tank, if the pipes are long enough. BUT DON'T DO THIS UNTIL THE WASTE IS CONNECTED!!
  • Connect cold water to tap. Might be possible using a Y connector on the same supply as the wash tank, but a neater solution would be to add washing machine fittings to the side of the existing sink unit. Unfortunately there's a water heater in the cupboard just where you need to work.
  • Connect hot water to tap. Probably not really needed since there's an adjacent sink, but would complete the job.

Usage configuration

  • Since it's already stained there's no problem in putting ferric chloride in it if we have some available (it needs 5 litres but 3 or 4 would do).
  • We can use a spare tank to start brewing the cupric chloride if we want to do that
  • There were some chemicals in the cupboard - developer, tinner, stain remover.
  • I (artag) have some date-expired mask stripper we can try in a strip tank

Placement

  • We need water and waste connections for the rinse tanks. These are simple washing machine fittings but we may need adapters for the supply pipework and a waste hose. I do have some plumbing fittings but we may need more.
    • Depending on when you need these, I could go out and get these on Fri/Sat. -- Elliot
    • I think we'll need at least one cold fitting, ideally another cold and a hot too, and a way to get 1.25" waste into the sink plumbing - possibly just a length of pipe, possibly some joints. May be easiest to put things in place and then find exactly what's needed.
  • Where do we put it ? I suggested replacing the unit 23 sink, but short-term it could simply go next to it. Tools may need moving, though. Or it could be installed in the unit 23 toilet. Or it could be integrated into a darkroom build. Discuss ..
    • I think it can fit next to the sink in the place of the metal cabinet that is there currently - it may be a bit longer and deeper but that shouldn't be a problem. Ideally it'd be nice to keep the sink for other chemical type experiments. If we can avoid talking about the darkroom then we can save ourselves a lot of hassle :-) -- Elliot.
  • It would be nice to have power without using the extension lead. The existing ring main might be extended fairly easily to put sockets on the wall near the sink.
    • Again, depending on when electrical stuff is needed, I could go out and get conduit/socket/back box/etc. on Fri/Sat. -- Elliot
    • I see there's a bit of conduit near #23 back door. Needs a socket plate and probably some more 2.5mm wire to link into the ring. Could be patched up but a better plan might be to look at fixing a couple of electrical jobs and buy the bits at the best price rather than in small pieces.

Model

Controls

The leftmost button on the control panel is mains power. If you see it lit up when no-one is using the tank, please turn it off (but if someone _might_ be waiting for it to warm up, please check first!). Probably a good idea to switch off at the mains as well.

Each tank and rinser then has a control section. Working from left to right, these are:

  • Developer - Heat button and 'heater active' light. Set to about 28°C. Heating not normally required.
  • Developer rinse - Spray button activates spray bar. Not yet available as it requires plumbing in.
  • Etch - Heat button and 'heater active' light. Set to about 48°C. Takes about 15-20 minutes to get hot.
    • Air bubbler button - only active when heating is also on.
  • Etch rinse - Spray button activates spray bar. Not yet available as it requires plumbing in.
  • Photoresist stripper - Heat button and 'heater active' light. Set to about 50°C. Optional.
  • Stripper rinse - Spray button activates spray bar. Not yet available as it requires plumbing in.
  • Tinning - Heat button and 'heater active' light. Set to about 50°C. Optional.

Instructions

The tank was previously in a school and there is a laminated sheet with usage instructions. It may not be applicable to our use but is worth looking at.

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