BGA Failure

Have you performed any fatigue calculations using Steinberg's method?

Steinberg's method shows that the relative deflection of the circuit board in bending is a concern because the resulting stress can cause leads and solder joints to fail.

Stiffening the board can increase the natural frequency which in turns tends to reduce the relative displacement of the board's bending.

The board level vibration can usually be reduced if the housing or chassis is mounted via isolator bushings, but there are trade-offs and even some exceptions to this rule.

Tom Irvine
Orbital Sciences