Building Beautiful Cell Phones Out Of FR4

Over on, [bobricius] took this technology and designed something great. It’s a GSM cell phone with a case made out of FR4. It’s beautiful, and if you’re ever in need of a beautifully crafted burner phone, this is the one to build.

The components, libraries, and toolchains to build a cellphone from scratch have been around for a very long time. Several years ago, the MIT Media Lab prototyped a very simple cellphone on a single piece of FR4. It made calls, but not much else. It was ugly, but it worked. [Bobricius] took the idea and ran with it.

The technique that goes into building an enclosure out of FR4 is something we’ve seen before, but we haven’t seen much of it since. Our resident old-school hacker [Voja Antonic] wrote a guide last year on using FR4 as an enclosure. The process is relatively simple – just leave some exposed copper around the edge of a panel, clamp it at about 90 degrees, and solder it to the edge of another panel. Adding captive nuts, standoffs, angles other than 90 degrees, and interlocking panels are slightly more advanced techniques, but still simple to implement.

[bobricius] has a few more tricks up his sleeve for his next version of this DIY cell phone. The nice, but hard to source, display will be replaced with a Charlieplexed 22×5 array of LEDs on a custom board, and the phone will feature QI wireless charging. If you can’t wait, [bobricius] is even selling a few of the current PCBs up on Tindie.

Of course, all this work would be for naught if the phone didn’t actually work. It does, at least until 2G networks are turned off. You can check out a video of that below.

37 thoughts on “Building Beautiful Cell Phones Out Of FR4

  1. Phones just got thinner?
    This gives me some ideas:
    If major phone companies integrated the circuit substrate as the casing then phones will get as thin as the LCD+Thin battery, the back cover is now the circuit interconnects with the chipset next to the battery and the front is just fr4. Use OLED for the thinnest LCD and place a conductive polymer grid multitouch sensor onto the OLED and a protective glass atop the lot. <3.5mm thick phone anyone?

    1. Aren’t they basically already?
      Phones have been down to 7-8 mm for a few years now. Even old clam shell designs were 7.5mm per half. As iPhone owners discovered, thinness is an issue if your phone is in a small pocket on tight clothing. Maybe chip-on-glass will remedy that with modern tempered glass. Or some sort of sapphire substrate like on watch faces, but there’s probably a reason why that’s not used.
      Using lower power chipsets ought to reduce battery thickness while still giving comparable time between charges. Obviously you’re restricted to text and audio, but if thin is your goal the easiest way to slim down is less mAh in the battery. Until ultra/super caps or new battery tech go commercial.

      1. Apple actually tried that (they bought a whole sapphire manufacturer at a time).

        It’s quite interesting to read on what it takes to “cut” a thin sheet of sapphire off a slab (with traditional Gorilla-type glass you harden the stuff after it’s been formed).

        Spoiler: you bombard the slab with protons of a precisely controlled energy, so they travel by a determined amount into the slab. A layer of hydrogen forms at this depth thus making it easier to separate the sheet.

        Now imagine what it takes to tune this manufacturing process. Apple didn’t manage to pull it through.

          1. It’s a crystal, so thin sheets would need absurd amounts of polishing to get flat.
            It’s easier to use the same general process as making silicon or quartz wafers. Also Sapphire requires high temp and pressure controlled very specifically to form, otherwise you probably get sintered opaque alumina. Most sapphires are/were(?) created in a sort of ‘extrusion’ where alumina is dusted onto a heated plinth that retracts at a specific rate to allow the new material to always be in the correct T/P regimen. Casting sheets would take up much more space than a furnace that makes long crystals to be cut down later.
            I guess the proton beam allows more slabs per crystal than conventional diamond saws would. Seems over the top given what can be done with a saw, but I guess given the investment in a sapphire furnace it makes up for it by having a very narrow kerf.

    1. At least in the US ATT and presumably other big networks will stop supporting the 2G protocol beginning in January including their GSM/ GPRS/ EDGE services. Since it’s built around a GSM module, your SOL until you can source a 3/4G one.

          1. Yeah 2G is used a lot for industrial control and telemetry here.
            3G will go before 2G.
            The talk here has been that the majority of spectrum will be used for 4G and later newer technologies, but some 2G carriers at the low end of the spectrum will be left for legacy 2G systems.

  2. It’s surprising so much 2G stuff is still being made, a lot of the cheap Chinese phones and watch-phones are stuck with 2G. I suppose 2G chipsets are like the PIC of phones, dirt cheap and all over the place. Surprising that so many hobbyist vendors still sell these modules, when 2G has so little time left.

    There might be a possibility for networks to carry on, and support the various burglar alarms and whatever that rely on 2G SMS. But spectrum is very valuable, networks pay a fortune for it. I’d be surprised if they kept on such a wasteful, inefficient use of spectrum. It might mean a lot of telemetry devices suddenly stop working, but they’re not even a blip on the radar, financially, for the networks. They use the cheapest plans, and send a few hundred bytes once every blue moon. Doesn’t make sense to keep supporting them. I suppose a specialist network could start up a 2G service just to service those devices, but the price would be way, way more than anyone would pay.

    It’s about time 3G modules, or 4G, displaced the old 2G ones suppliers are still selling. If eventually the whole system moves onto SDR, cognitive radio, then that should be the last “standard” anyone needs. Everything from then on will be back-compatible forever, since it’s just a matter of software supporting whichever protocol.

    1. “Everything from then on will be back-compatible forever…”

      Nothing is forever when it comes to wireless devices. Just ask anybody who’s bought wireless microphones operating in unlicensed bands over the past few years. The FCC has been very money-driven lately, and will sell any piece of spectrum it can, no matter what already “owns” it.

      If the DOT worked like the FCC, all you’d see on the interstates would be trucks and limos.

      1. Yeah but with SDR and cognitive radio, a cell can do any protocol. If it hears a GSM device broadcasting, looking for a tower, it can reply back in GSM mode, and handle the call. The handoff can be done the same way, this cell telling that cell to expect a GSM connection soon. Then once the GSM call is done, go back to using the frequency and antennas for whatever else pops up. Same for GPRS and whatever other obsolete format.

        Assuming that the GSM frequencies go on to be used for mobile phones, which is pretty likely, phone networks seem to be buying every other bit of spectrum they can get hold of.

        Stuff like this is coming. I dunno if it’s 5G or 6G, whenever they invent that. Radio in general is going more and more software-based. Probably even before it’s fully required, since it makes radio hardware cheaper and better. So it just means leaving the GSM module in the cell’s codebase.

        This all started off from frequency hopping, thank you Hedy Lamarr!

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