Thanks for your inquiry.
You don't need to calibrate BMM150 after you solder it on your PCB. You need to run self-test to see if BMM150 is working or not after PCB assembly. You may also need to check if BMM150 x/y/z data is not saturated on your PCB meaning that you don't have other strong inductor or metal screws near BMM150.
Every time when you start using BMM150 in your application you always need to calibrate it because the environmental magnetic filed has changed. Please refer to online article at https://www.ednasia.com/sensor-data-fusion-enhancing-gaming-navigation-and-vr-experiences/ for more information.
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