Steinberg Vibration Handbook Question

[stinsondawg]

I'm using Dave S. Steinberg's "Vibration Analysis for Electronic Equipment" to calculate the allowable displacement for a PCB (printed circuit board) with surface mount components. One of the equation variables is the thickness of the PCB. If my PCB is mounted to an aluminum housing should the PCB thickness include the thickness of the aluminum housing? Also, I'm not sure why the equation needs to know the PCB thickness? It seems to me that the surface mount components don't know how thick the PCB is.

 

[Tunalover]

stinsondawg-
Are you saying that one side of the PCB is in contact with the housing with no standoff or spacer between the PCB and housing? If this is true then the formula does not apply (however the deflection would still be dependant on the PCB thickness).

The deflection is ALWAYS dependant on the thickness. You'd be hard-pressed to find any formulae for beam or plate (PCB) deflection that don't include the thickness.

What issue of Steinberg do you have?

Tunalover

 

[shlomor]

In any pcb's problem deal with natural frequencis or deflection the THICKNESS of PCB (including any face plate)
is a critical parameter to solve the problem !!!!

 

[stinsondawg]

The circuit is mounted on 20 high mil standoffs.


I understand the deflection is dependant on thickness. What I don't understand is why Steinberg has thickness as one of the parameters for the desired PCB displacement. I read desired PCB displacement as meaning regardless of how thick the material is, the material shall not deflect more than the desired PCB displacement.

I'm looking at eq 8.5 in Steinverg's Vibration Analysis for Electronic Equipment, 2nd edition