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I am going to use TZC3 family trimmer capacitors from Murata (datasheet, skip to TZC3 section).

enter image description here

It has one of its terminals very close to the mounting surface, and theoretically if rotor is pressed too much (or device is overheated during soldering causing damage to the body), body can be bent and it potentially causes shortage of the rotor with the tracks on the surface of PCB underneath. No clearance size value is given in datsheets (I have no real device on hand to measure).

enter image description here

enter image description here

There're a number of slightly varying datasheets available on the internet, none of them mention that area underneath must be restricted.

Do I bother about it too much, or risk is real?

While writing this question I have got an idea to simply extend the track connecting to the rotor terminal to the central point of the device PCB area so that if issue happens, it shorts to the same signal. But one of the capacitors in my design is having power rail under it, and it seems I will have to divert it out of the area.

Update:

Following Finbarr's comment I did the following layout:

enter image description here

removing ground potential in proximity with the bottom knob.

Anonymous
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    The datasheet does say "do not apply excessive force", so don't! Bear in mind you'll have solder in between the terminals and the track to lift it up as well. I'd be more concerned about the capacitance between the rotor and the track and its effect on the circuit. – Finbarr Aug 30 '19 at 10:47
  • you might find a ancient BAKELITE capacitor, instead of a modern nylon-body capacitor that will cold-flow (or hot-flow) – analogsystemsrf Aug 30 '19 at 14:38
  • @Finbarr Board is having ground copper under them, and I have two caps of this type: one is connected to the ground by its rotor terminal (thus rotor appears above the same signal), and another NOT connected with its rotor to the ground (while having ground under the device). I have put a restrict space under the rotor's bottom knob (see newly added picture in the question), any better idea? – Anonymous Oct 22 '19 at 06:42

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