Well Purism made the design decision to place the PGP smartcard where the SIM card would typically be in a clamshell phone, and their sizes cannot be interchangeably swapped. Not many phones have a smartcard in the first place for Purism to work from prior experience.
I have my OpenPGP card inside the phone behind the battery.
I do not see what your point is in making that statement. My post is highlighting that the Librem 5 has the smartcard behind the battery instead of the SIM card, in comparison to clamshell phones.
I am now religiously removing the battery for any card changes. I know I haven’t done this on my Android phones as it has never been a problem but because this is still really an early model of the phone I suspect it may not have all the same level of protections in place to protect from nuke’ing your SIM card or damaging the phone.
Because you said that Purism placed the PGP smartcard by design where the SIM card typically is, and this is just not true.
I mentioned that in reference to clamshell phones, where removing the battery is required in order to access the SIM card behind it. To give a specific example, the Alcatel Go Flip 3, which was the clamshell phone I used as a stopgap before the Librem 5 USA.
It’s not a clamshell phone and every brick phone I’ve ever seen for years now has an externally accessible sim card slot. I’ve never killed a sim swapping them out on an Android phone but I’m sure it’s recommended to power off the phone. Mind you with today’s Android phones are they ever truly off? I don’t think so.
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The Alcatel Go Flip 3 is a clamshell phone.
It certainly isn’t true with any iPhone I’ve had in the last decade or so. In more recent iPhones, the battery isn’t even (user-)removable so it wouldn’t be realistic to put any card behind the battery.
(I wish Purism had put all three cards behind the battery.)
iPhones also come with the warning: shut down before removing or inserting the SIM card.
Ha ha. Good point. Are they indeed? (same for iPhone)
@guru only partially quoted my statement. The full statement is this:
They omitted the “in a clamshell phone” part (and thereafter) and made arguments based on the incomplete quote.
I think the question is … relevance. What percentage of mobile phone users today are using clamshell phones? Form factor (mobile phones) - Wikipedia
The form factor of the Librem 5 is pretty common and it is clear what the mainstream phones of the same form factor are.
While I haven’t checked this rigorously, “all” the iPhone models from the last 15 years have the same form factor (as each other / as the Librem 5) and they all have the SIM in the SIM tray that comes out the side - which means of course they are all subject to the same possibility of removing the SIM tray / SIM card while the phone is operating.
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Well my statement is based on the design of clamshell phones and the requirement of removing the back, then battery, in order to access the SIM card behind it. It has relevance in a thread where users of slate phones such as the Librem 5 still fry their SIM cards simply due to it being accessible on the side instead of the back, even when the device is turned on.
It builds on the other statement I made in that Purism had to decide where to place the PGP smartcard. Since very few, if any, phones have portable/removable cryptographic processors to begin with, Purism had to make their own decision on where to place it. They chose to put it behind the battery, where the SIM card typically is in a clamshell phone, and relocated it instead to the tray on the side where most slate phone users are familiar with, at the cost of this thread’s creation.
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… and other threads. 
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The SIM frying incident also happened to me recently. (I read the QSG, but missed the warning as an usual precautionary note. Shame on me… Fortunately, it was a “toy” prepaid card brought just to test the phone before I put my real card in it.) After that, I was curious why this happens with L5 and not with other phones so I took a look on the schematics (do this with a “standard” phone… ). For me, it indeed seems an immaturity in the design. What I found out:
- The combo card socket is such, that the SD part’s contacts sweep over the SIM card while the tray is moved
- The SD card power supply contact is always energized, even when the tray is pulled out (tray detect switch is disengaged), contrary to both ISO 7816 (which requires all contacts to be de-energized and disconnected immediately upon the beginning of removal of the card) and common sense
- The relative arrangement of the SIM and SD contacts result in 3.3V with reverse-polarity to be applied to the SIM power supply pad and then clock, then reset pads in while the tray is pulled out (and in reverse sequence when it is pushed in), damaging the SIM card and also possibly over-stressing U43 (power switch of SD card)
A possible fix to this problem that can be made by Purism in future releases of the mainboard is to make sure that disengagement of the tray detect switch disables the SD card power immediately in hardware, for example, by adding an additional pull-down transistor at TF_PWR_3V3_EN driven by TF_NCD or 4G_SIM_CD depending on the card detect switch’s operation. Aslo, what can be done meanwhile is updating the documentation to make it explicit that the “don’t remove the SIM tray while the phone is on” statement is not a customary warning that can be routinely ignored, but a workaround of an otherwise serious hardware bug.
I also wonder if this or similar deficiencies may have been spotted (and corrected) if the schematics would be subjected to public scrutiny before start of manufacturing.
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Most of that is over my head but it sounds like worthwhile feedback for Purism, which can be sent directly to feedback@puri.sm
Also @JCS
You can find discussion on the internet telling you to do the same with iPhones i.e. shut down before removing SIM card. Again though I don’t have the expertise to know whether that is just “precautionary”.
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It’s pretty hard to kill things with 3.3V over a momentary connection but you make a valid point if it’s not in industry spec.
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The latest batch of Librem 5 (~mid-2023) include a fuse intended to prevent damage to the SIM card. It is still highly encouraged that the device is powered off when inserting or removing the SIM card, as noted in the quick start guide. As far as ISO/IEC 7816 compliance, that is something that would need to be reviewed for future hardware releases.
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So now your SIM card is OK but you need to replace a (presumably SMD) fuse?
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Presumably so. Even if this does not yet comply with an ISO standard, it is a known issue with the L5 that has been documented for a long time and is disclosed with new product. The next question is “where can I find the documentation for the location and specs of the fuse, and fuse replacement instructions” and that is something I would have to ask, as I don’t have access to board design files or highly-detailed specs.
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