Come testare la scheda di controllo di una lavatrice?

I am getting a PCB manufactured for a project that I am working on. One of the parts, the A4950 motor driver, has a “pad” on the bottom, which is meant to be soldered to GND of the PCB for thermal dissipation. I was thinking about the prototyping, and I am unsure how I would go about (using a soldering iron), soldering the pad on the bottom.

I want to implement a control system I designed for a light electric motorbike. I would like to mount it as professionally as possible on the chassis. It consists of a power system pcb and a SAMC21 development board which I’ll merge later once this all works properly. I have tried screwing it directly on the aluminium chassis but have found that shocks and vibrations from the horn disturbed the system or even destroyed it upon large shocks. Is there a specific way car and motorcycle manufacturers mount their electronics to make their system as robust as possible?