This question is semi-related to my previous post "A few questions about potting". What I am curious of is what about physical jarring and g-forces harms electronics? And why? In my mind, a solid state component should not be effected by anything except extreme heat/cold, incorrect application of current, and direct phsical abuse. I think that if a circuit were suspended in potting or other medium where direct contact were not able to be made with it, then it should be fine no matter how many "g"s you put on it. Yet, electronics are rated for g-forces and sure enough, if you drop your cell phone, chances are that it won't work anymore. why is this?

 

Dropping equipment can cause case deformations that cause mechanical damage, like cracked PCB's and destroyed IC's - that epoxy is brittle. Too much G can do the same, and cause connectors to unseat.

If you do a really complete job of potting, then you change the rate at which heat can dissipate and risk damage because some component will go into thermal runaway. Makes it a bear to fix, too.

 

There can be wires bonded from the silicon die to the package leads and those are prone to breaking under too much acceleration or shock. Problems like electromigration can lead to the formation of intermetallics which, in turn, lead to increased sensitivity to shock. I'm sure if you went to the library and found a book on electronic reliability you could find many more potential problem areas.

 

This question is semi-related to my previous post "A few questions about potting". What I am curious of is what about physical jarring and g-forces harms electronics? And why? In my mind, a solid state component should not be effected by anything except extreme heat/cold, incorrect application of current, and direct phsical abuse. I think that if a circuit were suspended in potting or other medium where direct contact were not able to be made with it, then it should be fine no matter how many "g"s you put on it. Yet, electronics are rated for g-forces and sure enough, if you drop your cell phone, chances are that it won't work anymore. why is this?

In radio frequency circuits, deformation of components (especially coils) that are too small to even detect can seriously detune a circuit. VHF circuits have to be made extremely rigid mechanically, AND have to be THERMALLY stable.

Eric