CNC Mill Repairs IPhone 7

Modern smartphones are highly integrated devices, bringing immense computing power into the palm of one’s hand. This portable computing power and connectivity has both changed society in innumerable ways, and also tends to lead to said powerful computers ending up dropped on the ground or into toilets. Repairs are often limited to screen replacement or exchanging broken modules, but it’s possible to go much further.

The phone is an iPhone 7, which a service center reported had issues with the CPU, and the only fix was a full mainboard replacement. [The Kardi Lab] weren’t fussed, however, and got to work. The mainboard is installed in a CNC fixture, and the A10 CPU is delicately milled away, layer by layer. A scalpel and hot air gun are then used for some further cleanup of the solder pads. Some conductivity testing to various pads is then carried out, for reasons that aren’t entirely clear.

At this point, a spare A10 CPU is sourced, and a stencil is used to apply solder paste or balls – it is not immediately obvious which. The new chip is then reflowed on to the mainboard, and the phone reassembled. The device is then powered on and shown to be functional.

It’s an impressive repair, and shows that modern electronics isn’t so impossible to fix – as long as you have the right tools to hand. The smart thing is, by using the CNC machine with a pre-baked program, it greatly reduces the labor required in the removal stage, making the repair much more cost-effective. The team are particularly helpful, linking to the tools used to pull off the repair in the video description. We’ve seen similar hacks, too – such as upgrading an iPhone’s memory.  Video after the break.

[Thanks to Nikolai for the tip!]

39 thoughts on “CNC Mill Repairs IPhone 7

  1. Wouldn’t it be easier and less intrusive with less risk issues to just heat the CPU to the appropriate temperature so it will lift off the ball grid array solder pads – or is it affixed in a different way ?
    I wonder if just reviewing the CPU region again at appropriate temperature could be tried first, as it may be a simple matter of one or more of the ball pads going open or erratic with a ‘reflow’ by way of heating CPU with maybe a little pressure too as means to at first determine if it’s a simple solder issue ?

    1. given the part density, it’s probably next to impossible to remove JUST the “CPU” (more like an entire SOC), not to mention that you’d be heating the surrounding components and PCB twice instead of just once.

      This is probably a more cost effective way of doing it…it would be even more cost effective to just mill off the outer edge where the pads are and ignore the middle with all the hard silicon, which wears out the tool.

    2. I also do not really understand this trend, but it seems to be quite common.
      I first noticed it while browsing Ali Express and I saw CNC machines specifically designed for this purpose.

      I wonder if anyone ever tried a 500W soldering iron on those chips with a tip that is the same size as the chip that has to removed. Such a soldering iron could also be CNC’d. and combined with pre-heating the board and thermal conductive paste between the top of the chip and the soldering iron it could weel be a much faster and easier way.

      You will need some way to grab the chip, vacuum may work but could be problematic because it might interfere with heat transfer, but some clamp on the sides of the chip must be doable.

        1. Underfill is a PITA but I understand is also needed for things like vibration resistance

          I hope one of these ultrasonic cutter projects might lead to an ultrasonic wire cutter that can be used to cut through the underfill and solder balls and might lead to easier reworking of boards with BGA parts.

      1. You don’t understand the trend because you don’t understand what just happened. The CPU wasn’t removed, the RAM chip that sits on the back of the CPU was removed. This is a package-on-package design. There’s no way to heat these components without potentially dislodging the CPU in the process.

          1. I only discovered it after a bit of a search since it looked weird that what I thought was the A10 processor had about as many pins as a cheap microcontroller :-). That of course was not the case, the A10 has a crapload of pins on its BGA package.

    3. Yes there is an easier way by using induction heating and suction tool. These are custom made tools. You have a suction tool made of copper the same size as the chip your removing. place it on top of the ic, the induction heat allows the connections to soften and chip to be lifted with the suction. Pace is one company that makes this equipment.

    4. If you want to remove and replace the CPU then it would be. The CPU wasn’t touched. The A10 is Package-on-Package chip with the RAM sitting on top of the CPU. They used a mill to remove the RAM chip without touching the A10 CPU itself. You can tell if they milled down to the board level, the A10 CPU has an order of magnitude more pins on the bottom.

      1. I don’t think the person who wrote the article understands this either but I was wondering because the video clearly says ‘iPhone 7 DDR replacement’ which would indicate they were only replacing the RAM. Very interesting. The article should be updated to indicate this.

    5. I would do it that way. With a good hot air tool and some preheating of the board (100°C to 125°C) that should be easier than milling. You can protect the neighboring components with kapton tape or aluminium foil.

  2. First of all, it isn’t the CPU being replaced, its only the RAM chip (PoP arrangement, like on RPi) – The CPU is paired with the baseband, NAND and a few other things, making it essentially impossible to replace. The reason for him doing diode measurements on what is the output capacitors for the main PMIC is to check if certain rails (from what i can see, he’s checking PP1V1_SDRAM) to see if they’re shorted, which they often would be if a component such as RAM fails. The most compelling reason for using a mill rather than just desoldering the whole thing, which can indeed be done, is not to risk damaging the CPU and possibly also the board by ripping pads while cleaning (CPU’s underfilled mind you). Also, reballing CPU is a PITA, and again, risky.

    How do i know? I repair these things.

    1. Yeah. It’s actually kind of clever since iPhones are RoHS so soldered using lead-free solder at higher temperatures. By milling away the pieces they’re not affecting any of the other components, the new component is then soldered using leaded or other lower temperature solder so they’re again not risking to affect any other components in the vicinity. Far easier than having use heat shielding and potentially custom shields all over the map and still risk to move, lift or lose components… I like it.

  3. “shows that modern electronics isn’t so impossible to fix – as long as you have the right tools to hand”
    Seriously?!?!? This way you can also state that you can build your own saturn 5 rocket, if you only have the space, the proper amount of parts and enough time. In other words, you can do anything sure, but when it is far from practical or realistic then it doesn’t count or does it?

  4. For everyone asking why CNC, the answer is underfill. It’s very common in mobile application to essentially glue the chips to the main board. The glue or “underfill” doesn’t melt with heat. The CNC removes the chip exposing the solder joints. The level surface and partially cut solder balls left behind by the milling process makes a great foundation for the solder paste and replacement part.

  5. OK I watched that, and thought… with a little care and some careful milling, would it be possible to gain access to encryption keys and other stuff that Apple assumes are completely secure?

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