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triffid_hunter

PCB Heatbead for Home Etching

by triffid_hunter Sep 7, 2011
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FYI
https://oshpark.com/shared_projects/dGKHCD1f
2 layer board of 7.89x7.89 inches (200.41x200.41mm). $311.25 for three.

Hey man, my original bead heater broke and there is no way of replacing it, is it possible to hook this up directly to my MKS board? (i have a sunhokey prusa I3 ) the original thermal pad that came under the alluminum bed is about 2.1 (at around 27 C)OHMs and this you have here is rated for about .98 ohms.

Sooo, would it work? :D

Thanks in advance! :D

I made this heated bed for my Prusa on a double sided board, it came out fairly well just had two broken rails used solder to fix that. And than later used lacquer spray to cover the boards. Connected the wires to an ATX PSU. The Points of connection show 12V(-12V) but the board was all cold ? How to calculate the resistance ?

how do i have to connect the bed to my gen 7??

I was also wondering, in your pictures it looks like you kept the (toner?) etch resist on the copper after etching, then coated it with...something. Does the toner burn off when the bed is heated up, or was there another cleaning step that's not shown here?

I'm thinking of trying this out on a double sided board, but how would I etch-resist the side I want to keep solid? I was hoping to avoid using the toner-transfer method with an essentially all-black piece of toner paper.

I wonder if laying out Kapton on the solid side would be sufficient to resist etching? The only info I could find about this was an Instuctable related to making soft circuits. It seemed to imply the kapton/copper boundary was still intact after etching, so I think that might work.

Anyway, I'll g
ive it a try in a few days (weeks?) and report back, but if there's anyone else willing to give it a try sooner, please do!

Electrical tape works!

You could also try one or two good layers of spray paint, but test if the type you have dissolves with acetone.

quite a lot of this board was touched up with standard permanent marker. do a few coats for best results. if the adhesive on your kapton will survive your etchant, that should work too. maybe do both? I did leave the toner on, and gave it a blast of hairspray afterwards to help protect any exposed copper, hasn't done anything strange after being left at 130
°c a few times

Since the stock is bigger than the final device:

May I suggest adding a 10 to 15 mm side extension whit cuts where the cables connect? Then after soldering you can add strain relief with a couple of shrink wrap tubing. Pictured is what I mean.

(note in that case I had to make last-minute improvised changes to the circuit since the copper layer
turned out to be way less thick than expected. Origin of stock: shenzen, china, 200x150mm, eBay. Works well though.)

Where do you guys get 200x200 mm blank stock at a decent price?

ebay. posted from thailand for $10 incl. postage! It was 200x300!

Great!

And they really feature a 36 microns thick copper layer?

I don't know about exact copper thickness, but measured resistance and design resistance match to within my multimeter's ability to measure which is all I care about for this application! Actually using it seems to indicate that it's close enough too.

Resolder your connections! It looks messy, and at a glance I can tell its not a properly soldered connection.

When you're done, the solder should be smooth, low profile, and shiny. I think you had two issues here:

  1. Soldering iron too cold - leave it on the trace longer!
  2. Trace still protected by sharpie - hot solder works kind of like an acid; if the etching acid can't get to the trace, then the sol
    der can't get to it either... a little acetone will clean all the sharpie residue off the board

Also, you could be trying to use that atrocious rohs lead free stuff. Go down to rat shack and get you a nice big roll of carcinogenic solder. Your electronics (though not necessarily your lungs) will
thank you...

The photos make the joints look much worse than they are. Like looking at a reflection in glass, the photo shows up every miniscule variation in surface smoothness as an obvious blight.

Trust me, I have many years of soldering experience and when you see those joints IRL rather than through a photo you can see that they're fairly smooth and solidly attached, and could hold the weight of the whole printer without failing :)

They're never going to be perfectly smooth all over at t
hat size and with that much copper around unless I use a plumber's 150w iron or a gas torch or some other thing more substantial than a 50w temperature controlled iron.

I, for one, would like to see it hold up the weight of the printer! lol!!!

seriously though, I didn't consider the flash, but now that you mention it, I've had similar problems taking pictures of my electronics...

It also looks like there is too much exposed conductor where the wire meets the board. It might be worth sacrificing a little bit of build area to drill holes and bring the wires through from the top. This way it looks like it is begging for a short or to put 12V on your thermistor.

there is provision for drilling holes for the heater leads, but this board is exactly the same size as my glass plate, so I can't have anything sticking out the top