What are the modern limits on copper circuitry size?

Discussion in 'General Electronics Chat' started by CFlower, Jun 30, 2014.

  1. CFlower

    Thread Starter New Member

    Jun 3, 2014
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    Hi there,

    I'll try my best to be descriptive. I'm looking for as much information as possible on the limits on current technologies in producing copper circuitry. I had a nice conversation the other day with a member of my research group and he was telling me about the demand for the ability to 3D print copper. He was saying as it stands it requires laser power beyond what is readily available. Now I'm not an electrical engineer by trade but I had a few ideas of things that might be fun for me to test regarding that. However, the size regime would be very small.

    Some starting questions I suppose that would help me think are:

    What are the current lower limits (speaking about size and current limitations I suppose) on copper circuitry? Is there a reason why we don't make things smaller than we do, or is smaller printed circuitry desirable?

    What techniques are currently employed for making very small circuitry? I've read up on PCB fabrication techniques and what not but haven't found all the information I'm looking for.

    If anyone could point me in the right direction to learn about the current state of very small scale circuitry production I'd be very grateful.


    Thanks for your help,
    CFlower
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    copper is dificult to cut with a laser, it is reflective, and absorbs heat well. it is not impossible, and current state of the art of lasers is way more than enough, but why when chemical etching is so much better? laser cutting makes funny mittered edges on cuts due to the optical focussing, chemical etching dosnt. chemical etching can use the same procedures and processes as integrated circuit manufacturing.
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    This really depends on what circuitry are we talking about. Chip dies have many layers of copper metalization above the actual silicon which makes the interconnects, and this metalization will have feature size similar to the feature size of the transistors below, so lets say somehwere in tens of nanomemters. This of course is quite costly and requires perfect finishes to be possible.

    Standard PCB production on the other hand is usually limited to 150 or 100um, so roughly thousand times less accurate. There probably exist some technologies that are capable of doing better accuracy, but again they will cost much more than any standard high-volume pcb process.

    Another thing is when you say circuitry, do you mean everything on a normal pcb, like capacitors and resistors, inductors? Some of those components may be made on-chip but some not, so you have to take the package size of those into consideration. Likewise the package of the actual chips, BGAs can get prety small and dense, but then again you pay the price for miniaturization in the pcb, where you need more costly technologies like microvias etc.
     
  4. CFlower

    Thread Starter New Member

    Jun 3, 2014
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    Thanks for the very helpful answers! Alfacliff, I'm not really concerned with cutting metallic copper actually, but what you've brought up about chemical etching is indeed useful. I will look more into it.

    Kubeek, thanks for the numbers! This is precisely what I was looking for. When I said circuitry, I really only meant the copper connections. I've been toying with an idea in my lab that could be a feasible way of producing very small homogeneous customizable copper parts.
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    What would those parts be for? I can only imagine tiny resistors, capacitors or inductors, or an antenna maybe. Or do you mean like parts for some MEMS motors etc.?
     
  6. CFlower

    Thread Starter New Member

    Jun 3, 2014
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    I was thinking more like conductive traces for connections rather than parts for circuit elements. Is this unreasonable?
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Tiny traces means large resistance per length, so the traces need to be short. Which brings another question, where do these traces go to? Most likely to comparatively huge components which need to be spaced apart. Im not saying there is no purpose for such technology, but that you need to consider the pcb as a whole. There are times where you really need to squeeze in a few more traces into a crowded area, or aplications like magnetic field sensors.
     
  8. CFlower

    Thread Starter New Member

    Jun 3, 2014
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    What about production of chip dies like you mentioned above? I'm not so confident that this technique could do something accurate at ~10 nm scale, but ~100 nm might be possible. Maybe this could be a more cost effective option for that. Though I don't know much about the specifics of dies.
     
  9. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Chips are made using photolitography along with etching. They expose a photosensitive mask to light using some pattern, wash away the undeveloped resist and then apply something to the unblocked parts of the chip.
    Metal layers are done using different techniques, like sputtering or evaporation, all done in vacuum chambers.
     
  10. BobTPH

    Active Member

    Jun 5, 2013
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    Intel plans to have 10nm chips out next year, and is currently doing 14nm.

    Bob
     
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