Perhaps it is shear forces acting, instead of vibration?

You sit down, your leg presses the memory module against the cloth. The
lateral force stresses the solder joints...

Just a thought.


Isaac


Em 23/10/2010 02:40, RussellMc escreveu:
>>  We are developing a controller board that will be mounted on a
>> machine, the machine will vibrate (shake) heavily, but should not
>> exceed 3g ... (balance at at end) ...
>
>    BCCs may have useful comment?
>
> I don't know if the following is an issue but it would be worth being sur=
e of.
>
> Old memory SIMS with SMD memory ICsmake good key rings (for some
> values of good) - different than most and interesting to other people.
>
> Carry such a keyring in your pocket and you find that all the memory
> ICs fall off in quite a short time - weeks to months - one day you
> look at the board and note that there are no ICs. Thi is from the
> forces experienced in a pocket or, perhaps, when dangling from a car
> ignition key?
>
> (All?) Non ferrous metals have no fatigue limit and will fail under
> vibration at any level given enough cycles. I don't know the mechanism
> for the IC debonding mentioned above but forces in a pocket would not
> be expected to be large or especially frequent. Perhaps keychain
> vibration is the main mechanism?  Loss of ICs invariably seems to
> happen. Solder would probably be tinlead as these were older SIMs some
> yeas ago. Maybe I should try it with a newer RAM.
>
>
>     Russell McMahon
>
>
>>  We are developing a controller board that will be mounted on a
>> machine, the machine will vibrate (shake) heavily, but should not
>> exceed 3g. We have no control which direction it goes, so the circuit
>> board need to sustain vibration in all directions.  On top of that,
>> the environment is moist, we have some modules mounted with heavy
>> insulation inside. The insulation also added weight to the modules
>> (the modules are about the size of a deck of poker cards. places wide
>> side down to circuit.
>>
>>  What are the good ways to secure the modules and circuit board that
>> can sustain the vibrations?
>>

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