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Tuesday, January 22, 2013

Laser Cut Circuit Boards


I've had my laser cutter (Full Spectrum 40-watt CO2) for about 1.5 years - and over that time have spent a good amount of time trying to make circuit boards on it.  To be clear - I wanted to cut circuit boards.  Others have used their lasers to remove resist - to ultimately chemically etch boards.  

The barrier was cutting the metal.  I tried various tricks to cut copper - with little luck - even with unimaginably thin "copper leaf".

Then an employee of a local commercial hackerspace mentioned he'd cut .001" stainless steel shim. Stainless isn't solderable - but it made me wonder if mild steel could also be cut (which is solderable).  Turns out you can!  (stay tuned for a future blog post on cutting metal with lasers...)

It's taken a bunch of tweaks - but I can now reliably produce boards that are good enough to be used with 0.1" DIP components.

All is revealed in this video:



Quick summary (step-by-step / more details in video):
1. Attach .001" steel shim to cast acrylic sheet with mounting tape (leave paper backing on acrylic)
2. Cut out though-holes and board itself at 6.5 mm/s (2 passes)
3. Cut traces at 15 mm/s (2 passes)
4. Peel off non-trace segments from board surface (including tape and paper backing)
5. You have a circuit board!

Pros:
Fast - can make a simple board in only a few minutes
No chemical etching needed
Boards can be any color acrylic comes in - including transparent!
Laser can be used to cut through-holes / cut the board out in any shape

Cons:
Steel isn't a great conductor / may be an issue for some circuits
Boards are not as sturdy as etched ones
Traces limited to minimum of around 1/16" wide - not suitable for SMD
Soldering smaller (DIP) components can be a bit finicky

Click here to download the SVG for the 555 LED flasher

555 LED Flasher Circuit Details:
+Vin: About 3v (depending on LED)
R1: 10k ohm resistor
R2: 10k ohm resistor
C1: 33uf electrolytic capacitor
LED: An LED

This board was manually designed in Inkscape.  I'm very interested in how it goes if anyone tries this process with a board designed using EAGLE or other real software. 

If you try this project - please post your own tips / tricks here!

-Rich


14 comments:

  1. this just crossed my mind, one could under vacuum vaporize/boil a metalic, the metalic gas could condens on a colder surface (oh well it will condens anyway). this is how some scientific mirrors are made with ultra thin layers of metal.
    ofcourse you could repeat it to create thicker layers. Combined with laser cutting you could use any metal.

    ReplyDelete
    Replies
    1. Once you get a layer of copper thin enough to cut though... do you have a trace thick enough to use? How much current could it pass? Would it be prone to corrosion? Easy to damage while soldering? It's worth trying as an experiment but I suspect that if PCBs could use thin enough copper for easy laser cutting then they already would come that way. If for no other reason manufacturers might do this to save money since the price of copper has been so high.

      Delete
  2. "Steel isn't a great conductor / may be an issue for some circuits"

    My first though on this was to copper plate it. You would have to do that after cutting though or you are back to trying to cut copper. Then, at least using methods known to my very limited knowledge of such things, you would need to apply electricity to every trace which would be too much trouble.

    But...

    Maybe you could tin it? I wonder if liquid tin would work on steel. Actually, maybe that would be a way to make stainless steel solderable. Would that make a board with greater longevity than mild steel?

    ReplyDelete
    Replies
    1. yes - one quick work around is to manually tin the steel with solder.

      I've tried this - and it seems to work fine. If you linger in one spot too long though - the traces tend to peel up.

      Can also just tin the connections you're most concerned about.

      But realistically - if you're doing something tricky (1+ghz signal processing / etc) - this may not be the right prototyping method for the job.

      Delete
  3. Hi, a variant of this might be laser assisted etching.. the plan here is to use a lower power
    NUV 300mW diode, flat bottom flask with spacer and a mild etchant such as vinegar/peroxide.
    It spot heats the metal and etches in a single step, and also has the advantage that you can redo "bad" spots on the fly.
    Unfortunately my diodes aren't powerful enough but maybe use 4 of the 120mW PHR803T focussed on the same spot using 3D printed plastic and aixiz modules to generate higher power levels.

    ReplyDelete
  4. I've silver soldered stainless steel TIG welding rod for creating geometric models. I assume you mean soldering low temperature electrical connections when you say "stainless steel can't be soldered"

    ReplyDelete
    Replies
    1. Yes - referring to stainless not be solderable for electronics purposes.

      It actually can be soldered at lower temps - but needs acid flux - which will cause serious corrosion issues / bad news for electronics.

      Delete
  5. You say cutting copper simply don't work, care to elabourate what goes wrong?

    ReplyDelete
    Replies
    1. pretty much nothing happens. the copper seems to reflect back almost all the energy - in one case the reflected IR actually caused some tubing in my laser cutter to burn / smoke a bit.

      further - copper conducts heat very well - which makes me think what heat does go into the copper dissipates too quickly to do any good.

      painting the copper black helps a bit - but only enough to make some messy scorches / indents - not cut clean traces.

      Delete
  6. Our maker group has had quite good success cutting copper foil boards using very high pressure dog urine. The key to success is in being able to maintain consistently very high pressures using a positive displacement pump.

    We used a modified Toyota Landcruiser diesel engine fuel pump mechanism powered from a 24 volt source.

    ReplyDelete
  7. I continue coming back to read your brilliant quality blog post content, thanks for this wonderful blog post sharing,

    ReplyDelete
  8. Dog urine. pressurized? You missed the blog by a few days. April 1 was later.

    ReplyDelete
  9. wow... Its really very nice to read something on Laser Cut Circuit Boards. I like your post. Thanks for sharing.
    laser cutting

    ReplyDelete