elogesh
Mechanical
- May 10, 2002
- 187
Hi,
This is regarding the random vibration analysis of PCB.
One of our group company is involved in the design and maufacture of PCB board for electronic circuits -UPS systems.
In this regard, they are looking forward to evaluate the vibration, shock and thermal robustness of the PCB.
Our team being assigned in this vibration and shock test of the PCB board, both analytically (using FE) and then validation using testing.
In this regard, I have gone through this link
"
In this link (Vibration analysis of electronic equipment), they quoted the transmissibility as
Q = C (fn)^1/2
How they arrived out this relationship.
Where is the effect of excitation frequency and damping in this equation? or they used any empirical relations?
Then in the same article, it was quoted as
"Once an approximation of deflection is made, it should be checked against the design limits. In order to reduce deflection, stiffness of the board has to increase. This is usually done via stiffeners, additional anchor points, snubbers, and other mechanical means. In order to reduce stresses on PCBs or various devices on them the general guideline is to "decouple" hardware by one octave, i.e., 20, 40, 80, 160, and so on. For instance, the relationship between the chassis to board to a heat sink/bracket should follow the above multiplier. This helps mitigate any potential coupling between various constituents of the box."
I could not understand "In order to reduce stresses on PCBs or various devices on them the general guideline is to "decouple" hardware by one octave".
Can any one help in clarifying the above statement?
Looking foward for your help.
Regards,
Logesh.E
This is regarding the random vibration analysis of PCB.
One of our group company is involved in the design and maufacture of PCB board for electronic circuits -UPS systems.
In this regard, they are looking forward to evaluate the vibration, shock and thermal robustness of the PCB.
Our team being assigned in this vibration and shock test of the PCB board, both analytically (using FE) and then validation using testing.
In this regard, I have gone through this link
"
In this link (Vibration analysis of electronic equipment), they quoted the transmissibility as
Q = C (fn)^1/2
How they arrived out this relationship.
Where is the effect of excitation frequency and damping in this equation? or they used any empirical relations?
Then in the same article, it was quoted as
"Once an approximation of deflection is made, it should be checked against the design limits. In order to reduce deflection, stiffness of the board has to increase. This is usually done via stiffeners, additional anchor points, snubbers, and other mechanical means. In order to reduce stresses on PCBs or various devices on them the general guideline is to "decouple" hardware by one octave, i.e., 20, 40, 80, 160, and so on. For instance, the relationship between the chassis to board to a heat sink/bracket should follow the above multiplier. This helps mitigate any potential coupling between various constituents of the box."
I could not understand "In order to reduce stresses on PCBs or various devices on them the general guideline is to "decouple" hardware by one octave".
Can any one help in clarifying the above statement?
Looking foward for your help.
Regards,
Logesh.E
