So far I haven't seen a cell phone that allows to detach the SIM card without first detaching the battery - the SIM card is placed behind the battery and inaccessible unless the battery is detached.
I assume there's some electrical engineering reason for that - like maybe detaching a SIM card with battery installed will damage it.
Is there any electrical engineering reason for that?
I am currently working on a GSM connected device and I feel like I have something to contribute, although I am no expert so be sure to do further research if this doesn't satisfy.
The GSM module I am working with states something along the lines of this in its datasheet (re-worded for NDA purposes, and to make it more general):
A SIM detection pin must be used in order to comply with the 3GPP TS 11.11 document recommendation if the physical design of the mobile equipment allows the user to remove the SIM card during operation.
I combed the mentioned 3GPP document and did not find much talking about this so I am unsure of how well this is specified or if that point was from an older version of the document. Section 11.2.8 "SIM Presence Detection and Proactive Polling" of that document defines a polling procedure to detect SIM removal but only at critical times (what they call "card sessions", for example a phone call).
In any case, my theory is this: this is done as a design decision to simplify the phone firmware, as the phone would only ever need to do its SIM card initialization on power up, and to avoid having to comply with any possible procedures which only apply if you allow the user to remove the SIM card during operation. Seeing as there isn't a clear advantage of providing that feature, it's a no-brainer (for me at least) to go with a design that does not allow SIM hot-swapping.
SIMs are definitely supposed to survive powered insertion and removal. They're also ESD protected so you can handle them.
Most likely it's done this way to simplify the design of the phone and reduce cost: there only has to be one access cover for the battery. This cover is the size of the battery. Therefore it covers the SIM holder, which is soldered to the board. Any other design involves extra space or another hole in the phone, through which dust and moisture can enter.
3GPP TS 11.11 doesn't say anything about batteries, but it does date from the era when SIMs could theoretically be full smartcard sized. If those were ever used they were probably removable through a card slot.
My understanding is that at least part of the reason for this is pressure from carriers: They don't want to make it easy for users to switch SIMs, because they'd rather force you to buy more than one phone if that's something you'd do regularly.
