Securing a pcb to be used in a keyboard to its case
Obviously, you need to use enough standoffs to do the job!

In addition, if you can't put standoffs every place you think you need them, you might need to use one or more "stiffeners" (usually a metal bar with an L-shaped cross-section) that spans between pairs of standoffs and provides extra mechanical support to the PCB. Make sure that components and their connections won't interfere with where the stiffener needs to touch the PCB.