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Nearly any uses for flexible electronics would also be satisfied by sufficiently small electronics such that lack of flexibility doesn't matter. Eg. rather tha

Nearly any uses for flexible electronics would also be satisfied by sufficiently small electronics such that lack of flexibility doesn't matter. Eg. rather than having every pixel in your flexible screen be flexible, you make each pixel rigid and have the joints between pixels flexible. In this case, this design is based on SERV, which uses ~2100 gate equivalents, which in a recent tech node would be 40 um^2. That means you could fit a 10x10 grid of these in a single pixel on an iphone screen. I really can't think of a use case where a region 1/100th of an iphone screen pixel being rigid would be a problem.

wslh 2y ago
So, nothing particularly interesting here? When I first saw 'flexible' I immediately thought about balancing a chip's specifications, not its material flexibility!
- dragontamer 2y ago
  Flexible circuits are interesting and worthy of discussion. Really, the whole process here is fascinating to me. There's been a lot of progress in flex circuits over this recent decade. None of it is electrically or computationally new. It's 1980s tech from a computation perspective. But mechanically?? Being able to weave circuits seamlessly into clothes, tapestry, and such is pretty cool. If only for the cosplay / costume designers but that's still a pretty / beautifully kind of display (especially with a few fiber optics to move lights around). One of the interesting electro-mechanical issues is that flex circuits are necessarily thin, making grounding / return currents exceptionally consistent. On the downside however, solid planes / ground fills are bad for flexibility, so you apparently need to make a ground-grid instead of ground-fill. Very interesting tech overall. Even if it's applications are quite small right now.
- grayhatter 2y ago
  It's funny, I thought the exact opposite. > Flexible... isn't that the point of any central processing unit, to be able to handle many differing types of work? Oh, pliable? that's cool, I wonder how that works?
kibwen 2y ago
At a certain threshold, miniaturization of electronics can become counterproductive for space applications. The amount of radiation received per unit of area remains constant but our transistor density keeps increasing, which means that every individual event threatens to wreak an increasing amount of havoc (e.g. more bits flipped in RAM per cosmic ray). Considering the increasing amount of error correction and redundancy needed to counter this, we may reach a practical floor on transistor density for such domains.
- spwa4 2y ago
  ... which is a huge problem for solar panels ... but why would it matter for microprocessors?
  - deleted 2y ago
    [deleted]
  - undersuit 2y ago
    You don't want transistors operating under the influence of outside forces. More than just having a bit flip in your data, what if one of the control lines in the CPU flips and the entire instruction stream gets corrupted... while you're trying to perform orbital maneuvers.
    - vmladenov 2y ago
      You use multiple processors and a consensus algorithm.
      - undersuit 2y ago
        You can do that.
- synthos 2y ago
  It's also, if not more so, a factor of transistor voltage. 1.1V transistors are less prone to upset events than 0.7V. It's possible (assumption, here) that some 3+ volt circuits are still used for critical components of the system
mlyle 2y ago
You would need to connect wires to that little 40 um^2 mote to do anything, though, which in practice makes the rigid places needing strain relief a lot larger.
- marshray 2y ago
  It also makes the amount of strain proportionately smaller. We're talking about a 3mm bend radius here, so there's a few orders of magnitude to work with.
  - mlyle 2y ago
    Not as many as you think, because you need to have targets bigger than the ~20um wirebond wire to solder to... and the little wire and bond pad are not very tolerant of strain at all. Bonding wires to the thing in the first place easily increases its size by a couple of orders of magnitude.
zozbot234 2y ago
Leading-edge fab nodes are way too costly for this kind of use. Specialty, low-volume chips are the domain of trailing-edge tech nodes, sometimes even at the μm level. Besides as some sibling comments mentioned, contact pads for off-chip wires would get so big as to ultimately take up most of the area, so there would be no real advantage to using the finer nodes.
- pclmulqdq 2y ago
  Most microcontrollers today are using 40-90 nm processes. That's not the micron level at all. Chips that need current-handling capabilities or have weird needs will use bigger process nodes. This is a big part of why automotive electronics use old nodes.
  - amelius 2y ago
    You're thinking of power mosfets, but automobiles have entertainment systems too.
    - pclmulqdq 2y ago
      The power electronics are more complicated than MOSFETs, and the entertainment systems use chips on modern process nodes. The main use I can see for MCUs/MPUs on old process nodes is replacement parts for 10+ year old equipment.
addaon 2y ago
40 um^2 might cover the logic (although I think your logic transistor count is a factor of three low; and something like this is most likely to be made on a 45 nm or bigger process), but doesn’t cover IO pads. If you’re willing to wire bond directly to a flex circuit you may be able to use pads on to order of 50 um x 50 um (each! Likely need 6 or 8 pads to be useful), but that’s a hell of a process, and you’d have to encapsulate afterwards, adding bulk. If you want to flip-chip mount it’s pretty hard to go under 1 mm x 1 mm for a useful microcontroller, although there’s some stuff out there at 600 um x 600 um or so from memory — but pad sizes under 300 um then bump up your resolution requirements for the flex circuit you’re bonding to.
- hajile 2y ago
  They are spot-on with the transistor count for the CPU (though I believe it doesn't include all your RAM registers). SERV is a serial CPU that can range from doing calculations just 1 bit at a time up to doing them 4 bits at a time. https://github.com/olofk/serv https://github.com/olofk/serv It's pretty incredible considering the 6502 was already considered tiny when it was released with just ~4500 gates vs the 6500 in the 8085 and the 8500 in the z80.
  - tycoon666 2y ago
    6502 has 3510 Transistors. 4500 gates seam impossible.
Brian_K_White 2y ago
What are the fab requirements of the two techs? If the ffc version can be manufactured with as basic tech as ffc, then that is huge. Also bonding small rigid things to flexible things is never actually the same as a flexible thing, in several different ways. These are not equivalent even if you can manage to use either one for some use cases by accepting various compromises.
alted 2y ago
Ignoring flexibility and cost/performance, this may be a sign that rapid chip fab turnaround times are possible. These were made by Pragmatic Semiconductor [1], who claim they can make chips within 48 hours and deliver within 4 weeks (likely due to their use of unconventional materials). Traditional silicon fabs, including trailing-edge foundries and TSMC, take 2-9 months. I do wish they'd emphasized this instead of flexibility. [1] https://www.pragmaticsemi.com/ https://www.pragmaticsemi.com/
- IshKebab 2y ago
  Yeah but traditional silicon fabs aren't making 12k gate chips.
  - Teever 2y ago
    What's the turn around time on 12k gate chips from a traditional fab?
    - dragontamer 2y ago
      Just googling really quick: the Lattice Semiconductor LFE5U-12 is a 12k-LUT FPGA (and a LUT is way more flexible than a gate). So realistically, if you need fully custom digital logic, you'd buy LFE5U-12 instead and program that. So that's $16 FPGA from widely available distributors (like Digikey) who likely can afford 1 or 2 day shipping. ------------- Custom chip design for a flex-circuit is interesting, but only if you have substantial analog parts that cannot be easily implemented by an FPGA.
      - rkangel 2y ago
        The power profile of an FPGA is very different (worse) than dedicated silicon. Both the background current and cost of a gate switch. There are a lot of situations where that isn't acceptable.
        londons_explore 2y ago
ChuckMcM 2y ago
Some questions you might consider which would help you to think of some use cases; 1) How would wiring to you processor work? 2) How many flexible compute applications are currently using just really small processors? 3) Given that Pragmatic has raised a lot of money, what was it in their use case that the investors thought would make a better product? 4) Besides flexibility, are there other requirements in this product space? 5) Given that you've just imagined a product with a flexible screen but solid pixels, does this exist on the market? Are there flexible screens on the market? How do those screens choose to implement flex versus the idea you have proposed? What factors might make their choices better (or worse) than the idea you proposed? I'm not being critical here, I think you start with an excellent starter question which is "Would the requirements be satisfied by sufficiently small electronics such that [the] lack of flexibility [in the electronics] doesn't matter?" The trick then is to see if you can see how other people who invested time and money in answering either that, or a closely adjacent, question answered it. When you do that you'll get to see what they thought the overall requirements were vs the technology they picked, and perhaps it might inform if the Pragmatic solution would be a better fit or the 'tiny electronics' solution would be a better fit. I'll be the first to admit that I'm 'weird' in that I really do enjoy going down these sort of engineering optimization rabbit holes to develop a better understanding of what problems various proposed solutions are trying to solve.
- saulrh 2y ago
  > 1) How would wiring to you processor work? My (relatively limited) experience is that this is what really makes wearable projects obnoxious. Even if you have a chip with a tiny footprint, you either put it on a breakout board that isn't tiny or you spend twenty hours soldering nearly microscopic bits of magnet wire to it. It's the same for the piles of passive components and peripherals that every project requires, the voltage regulators and smoothing capacitors and power transistors and stuff: You either attach everything to a big PCB or you're faced with a spaghetti nightmare of point-to-point wiring that makes "normal" dead-bug circuitry, the kind you might find embedded in a block of resin for aesthetic points, look like a walk in the park. Flexible processors don't necessarily solve that problem, but they definitely demonstrate that flexible circuits in general are advancing in useful ways, better signal quality and longer runs and better process yield. The bigger these things get the better they are for replacing that mess of integration spaghetti that I always see DIY wearable projects suffering from. (I think that industrial wearables typically solve this by concentrating everything complicated down to a rigid brain-box, c.f. smart-watches or those heated jackets that have a socket for a power tool battery in the pocket.)
nine_k 2y ago
> you make each pixel rigid and have the joints between pixels flexible Alternative 1: Assemble about 3 million individual rigid pixels of an iPhone screen on a flexible substrate, keeping the gaps flexible. Alternative 2: Produce a single flexible screen piece, requiring no per-pixel assembly. Which alternative, to your opinion, is likely to cost less?
leptons 2y ago
The article is about a CPU, not a display technology - there's a big difference in functionality and fabrication between those two things, so your iPhone screen pixel example doesn't really fit this use case. I think this flexible CPU tech is interesting. If it's possible to build an ADC onto it and monitor flexible sensors, that would open up one kind of possibility, and probably an advantage over chip-on-flex solutions. I'm sure there are many more interesting uses for this. It's impressive that a CPU can be implemented with this tech, but interesting things can be done with far fewer gates.
wyldfire 2y ago
Don't you have to put those BGAs on some kind of pad?
RachelF 2y ago
I agree, this CPU has double the transistors of a 6502, and runs at 1/20th of a 6502 speed. A silicon product will be faster, the size of a printed dot and use less power. No word either on how many bending cycles the product supports. Still, it's early days, and flexibility might have some use.
fsckboy 2y ago
>Nearly any uses for flexible electronics would also be satisfied by sufficiently small electronics such that lack of flexibility doesn't matter. we make microelectronics as complex as we can because 128 bits would be better than 64 bits, and floating point, and parallelism, pipelining, speculative execution, and caches, etc. we already make microelectronics as small as we know how, because speed of light makes a difference, and power dissipation also. and our chips, already completely consumed by the tasks we give them, are too big to fit your definition of flexibility not mattering. So-ooo-o, if our chips were flexible it would solve the problem we are both trying to solve, which will not be solved your way, except in some uncertain future.

wslh 2y ago

So, nothing particularly interesting here? When I first saw 'flexible' I immediately thought about balancing a chip's specifications, not its material flexibility!

dragontamer 2y ago
Flexible circuits are interesting and worthy of discussion. Really, the whole process here is fascinating to me. There's been a lot of progress in flex circuits over this recent decade. None of it is electrically or computationally new. It's 1980s tech from a computation perspective. But mechanically?? Being able to weave circuits seamlessly into clothes, tapestry, and such is pretty cool. If only for the cosplay / costume designers but that's still a pretty / beautifully kind of display (especially with a few fiber optics to move lights around). One of the interesting electro-mechanical issues is that flex circuits are necessarily thin, making grounding / return currents exceptionally consistent. On the downside however, solid planes / ground fills are bad for flexibility, so you apparently need to make a ground-grid instead of ground-fill. Very interesting tech overall. Even if it's applications are quite small right now.
grayhatter 2y ago
It's funny, I thought the exact opposite. > Flexible... isn't that the point of any central processing unit, to be able to handle many differing types of work? Oh, pliable? that's cool, I wonder how that works?

kibwen 2y ago

At a certain threshold, miniaturization of electronics can become counterproductive for space applications. The amount of radiation received per unit of area remains constant but our transistor density keeps increasing, which means that every individual event threatens to wreak an increasing amount of havoc (e.g. more bits flipped in RAM per cosmic ray). Considering the increasing amount of error correction and redundancy needed to counter this, we may reach a practical floor on transistor density for such domains.

spwa4 2y ago
... which is a huge problem for solar panels ... but why would it matter for microprocessors?
- deleted 2y ago
  [deleted]
- undersuit 2y ago
  You don't want transistors operating under the influence of outside forces. More than just having a bit flip in your data, what if one of the control lines in the CPU flips and the entire instruction stream gets corrupted... while you're trying to perform orbital maneuvers.
  - vmladenov 2y ago
    You use multiple processors and a consensus algorithm.
    - undersuit 2y ago
      You can do that.
synthos 2y ago
It's also, if not more so, a factor of transistor voltage. 1.1V transistors are less prone to upset events than 0.7V. It's possible (assumption, here) that some 3+ volt circuits are still used for critical components of the system

mlyle 2y ago

You would need to connect wires to that little 40 um^2 mote to do anything, though, which in practice makes the rigid places needing strain relief a lot larger.

marshray 2y ago
It also makes the amount of strain proportionately smaller. We're talking about a 3mm bend radius here, so there's a few orders of magnitude to work with.
- mlyle 2y ago
  Not as many as you think, because you need to have targets bigger than the ~20um wirebond wire to solder to... and the little wire and bond pad are not very tolerant of strain at all. Bonding wires to the thing in the first place easily increases its size by a couple of orders of magnitude.

zozbot234 2y ago

Leading-edge fab nodes are way too costly for this kind of use. Specialty, low-volume chips are the domain of trailing-edge tech nodes, sometimes even at the μm level. Besides as some sibling comments mentioned, contact pads for off-chip wires would get so big as to ultimately take up most of the area, so there would be no real advantage to using the finer nodes.

pclmulqdq 2y ago
Most microcontrollers today are using 40-90 nm processes. That's not the micron level at all. Chips that need current-handling capabilities or have weird needs will use bigger process nodes. This is a big part of why automotive electronics use old nodes.
- amelius 2y ago
  You're thinking of power mosfets, but automobiles have entertainment systems too.
  - pclmulqdq 2y ago
    The power electronics are more complicated than MOSFETs, and the entertainment systems use chips on modern process nodes. The main use I can see for MCUs/MPUs on old process nodes is replacement parts for 10+ year old equipment.

addaon 2y ago

40 um^2 might cover the logic (although I think your logic transistor count is a factor of three low; and something like this is most likely to be made on a 45 nm or bigger process), but doesn’t cover IO pads. If you’re willing to wire bond directly to a flex circuit you may be able to use pads on to order of 50 um x 50 um (each! Likely need 6 or 8 pads to be useful), but that’s a hell of a process, and you’d have to encapsulate afterwards, adding bulk. If you want to flip-chip mount it’s pretty hard to go under 1 mm x 1 mm for a useful microcontroller, although there’s some stuff out there at 600 um x 600 um or so from memory — but pad sizes under 300 um then bump up your resolution requirements for the flex circuit you’re bonding to.

hajile 2y ago
They are spot-on with the transistor count for the CPU (though I believe it doesn't include all your RAM registers). SERV is a serial CPU that can range from doing calculations just 1 bit at a time up to doing them 4 bits at a time. https://github.com/olofk/serv https://github.com/olofk/serv It's pretty incredible considering the 6502 was already considered tiny when it was released with just ~4500 gates vs the 6500 in the 8085 and the 8500 in the z80.
- tycoon666 2y ago
  6502 has 3510 Transistors. 4500 gates seam impossible.

Brian_K_White 2y ago

What are the fab requirements of the two techs? If the ffc version can be manufactured with as basic tech as ffc, then that is huge. Also bonding small rigid things to flexible things is never actually the same as a flexible thing, in several different ways. These are not equivalent even if you can manage to use either one for some use cases by accepting various compromises.

alted 2y ago

Ignoring flexibility and cost/performance, this may be a sign that rapid chip fab turnaround times are possible. These were made by Pragmatic Semiconductor [1], who claim they can make chips within 48 hours and deliver within 4 weeks (likely due to their use of unconventional materials). Traditional silicon fabs, including trailing-edge foundries and TSMC, take 2-9 months. I do wish they'd emphasized this instead of flexibility. [1] https://www.pragmaticsemi.com/ https://www.pragmaticsemi.com/

IshKebab 2y ago
Yeah but traditional silicon fabs aren't making 12k gate chips.
- Teever 2y ago
  What's the turn around time on 12k gate chips from a traditional fab?
  - dragontamer 2y ago
    Just googling really quick: the Lattice Semiconductor LFE5U-12 is a 12k-LUT FPGA (and a LUT is way more flexible than a gate). So realistically, if you need fully custom digital logic, you'd buy LFE5U-12 instead and program that. So that's $16 FPGA from widely available distributors (like Digikey) who likely can afford 1 or 2 day shipping. ------------- Custom chip design for a flex-circuit is interesting, but only if you have substantial analog parts that cannot be easily implemented by an FPGA.
    - rkangel 2y ago
      The power profile of an FPGA is very different (worse) than dedicated silicon. Both the background current and cost of a gate switch. There are a lot of situations where that isn't acceptable.
      - londons_explore 2y ago

ChuckMcM 2y ago

Some questions you might consider which would help you to think of some use cases; 1) How would wiring to you processor work? 2) How many flexible compute applications are currently using just really small processors? 3) Given that Pragmatic has raised a lot of money, what was it in their use case that the investors thought would make a better product? 4) Besides flexibility, are there other requirements in this product space? 5) Given that you've just imagined a product with a flexible screen but solid pixels, does this exist on the market? Are there flexible screens on the market? How do those screens choose to implement flex versus the idea you have proposed? What factors might make their choices better (or worse) than the idea you proposed? I'm not being critical here, I think you start with an excellent starter question which is "Would the requirements be satisfied by sufficiently small electronics such that [the] lack of flexibility [in the electronics] doesn't matter?" The trick then is to see if you can see how other people who invested time and money in answering either that, or a closely adjacent, question answered it. When you do that you'll get to see what they thought the overall requirements were vs the technology they picked, and perhaps it might inform if the Pragmatic solution would be a better fit or the 'tiny electronics' solution would be a better fit. I'll be the first to admit that I'm 'weird' in that I really do enjoy going down these sort of engineering optimization rabbit holes to develop a better understanding of what problems various proposed solutions are trying to solve.

saulrh 2y ago
> 1) How would wiring to you processor work? My (relatively limited) experience is that this is what really makes wearable projects obnoxious. Even if you have a chip with a tiny footprint, you either put it on a breakout board that isn't tiny or you spend twenty hours soldering nearly microscopic bits of magnet wire to it. It's the same for the piles of passive components and peripherals that every project requires, the voltage regulators and smoothing capacitors and power transistors and stuff: You either attach everything to a big PCB or you're faced with a spaghetti nightmare of point-to-point wiring that makes "normal" dead-bug circuitry, the kind you might find embedded in a block of resin for aesthetic points, look like a walk in the park. Flexible processors don't necessarily solve that problem, but they definitely demonstrate that flexible circuits in general are advancing in useful ways, better signal quality and longer runs and better process yield. The bigger these things get the better they are for replacing that mess of integration spaghetti that I always see DIY wearable projects suffering from. (I think that industrial wearables typically solve this by concentrating everything complicated down to a rigid brain-box, c.f. smart-watches or those heated jackets that have a socket for a power tool battery in the pocket.)

nine_k 2y ago

> you make each pixel rigid and have the joints between pixels flexible Alternative 1: Assemble about 3 million individual rigid pixels of an iPhone screen on a flexible substrate, keeping the gaps flexible. Alternative 2: Produce a single flexible screen piece, requiring no per-pixel assembly. Which alternative, to your opinion, is likely to cost less?

leptons 2y ago

The article is about a CPU, not a display technology - there's a big difference in functionality and fabrication between those two things, so your iPhone screen pixel example doesn't really fit this use case. I think this flexible CPU tech is interesting. If it's possible to build an ADC onto it and monitor flexible sensors, that would open up one kind of possibility, and probably an advantage over chip-on-flex solutions. I'm sure there are many more interesting uses for this. It's impressive that a CPU can be implemented with this tech, but interesting things can be done with far fewer gates.

wyldfire 2y ago

Don't you have to put those BGAs on some kind of pad?

RachelF 2y ago

I agree, this CPU has double the transistors of a 6502, and runs at 1/20th of a 6502 speed. A silicon product will be faster, the size of a printed dot and use less power. No word either on how many bending cycles the product supports. Still, it's early days, and flexibility might have some use.

fsckboy 2y ago

>Nearly any uses for flexible electronics would also be satisfied by sufficiently small electronics such that lack of flexibility doesn't matter. we make microelectronics as complex as we can because 128 bits would be better than 64 bits, and floating point, and parallelism, pipelining, speculative execution, and caches, etc. we already make microelectronics as small as we know how, because speed of light makes a difference, and power dissipation also. and our chips, already completely consumed by the tasks we give them, are too big to fit your definition of flexibility not mattering. So-ooo-o, if our chips were flexible it would solve the problem we are both trying to solve, which will not be solved your way, except in some uncertain future.