Equipment/PCB etch station

From London Hackspace Wiki
Jump to navigation Jump to search
Etch station

Important Warnings

  • 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 or disable the heaters by unplugging the associated connector inside the cupboard door.
  • 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 (hint - look on the Mega website).

Status

Etch tank bubbling not working

The bubble pump hums, but no bubbles appear. If you use the tank, you'll need to manually agitate the etch (jiggle the etch basket around occasionally).

Todo

Next

  • Add a pipe clip to the cold water feed so the pipe is properly supported
  • Find out why the bubbles fail and fix it
    • The pump hums but no bubbles appear. On one occasion when I looked at it, I found that running the pump with no pipe attached, together with blowing out the bubble pipe to clear it, got it working again.
    • I think what's happening is that the bubble pump is quite low power and if the delivery tube gets full of etchant it has difficulty clearing it. It may be inevitable that the tube gets full of etchant, or it may be that the non-return valve doesn't work. There's a replacement non-return valve in the cupboard that can be tried if someone feels like tackling it. This will almost inevitably result in some etchant spilling so come prepared with very old clothes.
    • If that's not sufficient, we could replace the pump. The existing one is quite handy as it's mounted on the tank, and the whole tank unit can be unplugged and removed. This would be difficult with a larger, more powerful pump. Maybe just a new one would be sufficient. I have a similar tank that is left unused for months at a time but doesn't seem to have any trouble starting the bubbles up.
    • There is a very good pump available, ready in the cupboard if we want to do a complete job on this. It's too big to mount on the tank, so installing it will require a little rewiring to power it direct from the control panel rather than via the etch tank's loom. It will also need a better antisyphon trap as it's far too nice a pump to allow etchant to get in and ruin it. But this trap could be mounted on the cupboard wall, and just the air pipe connected to the tank, leaving the tank nice and easy to remove.

Soon

  • Scrub out sink
  • 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

Placement

  • 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.
  • 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.
  • Photoresist stripper - Heat button and 'heater active' light. Set to about 50°C. Optional.
  • Stripper rinse - Spray button activates spray bar.
  • Tinning - Heat button and 'heater active' light. Set to about 50°C. Optional.

The spray bars work best if only one is on at a time (and unless you're making a lot of boards at once, you probably only need one).

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.

Retrieved from ‘https://wiki.london.hackspace.org.uk/w/index.php?title=Equipment/PCB_etch_station&oldid=14680’