Thanks for all the ideas, we will test the controller on vibration
table for make sure it will survive the vibration.

The controller will be used in machines in extremely hard to access
place, will likely operating 24 hours a day.
The vibration is not continuous, but when it vibrates, it will be
vibrate for some time.

So far we have separate the components into modules, each modules is
enclosed in there own enclosure, with silicon rubber filled in.

The modules are mounted on main PCB, main PCB has a metal frame
underneath to support it,
the complete board is then mounted on the rubber foot to the chassis.

The modules may need some more reenforcement to make sure it will not
fall of the main PCB board.

-- Youda

On Sat, Oct 23, 2010 at 2:22 PM, Gordon Williams <gwilliams@ncf.ca> wrote:
> I would expect the forces in general use of a key ring would exceed 10's =
of
> Gs under normal use. =A0People drop them on counters or drawers, they col=
lide
> with keys, shoved around with other things in the pocket. =A0I wouldn't w=
ant
> to live my life as a key ring.
>
> There is a logarithmic relationship between fatigue life and stress. =A0A
> small decrease in stress increases the part fatigue life by a large amoun=
t.
> Typically, when you are less than 1/3 the ultimate breaking load of a
> nonferrous material you will be into the very high cycle life range (>10^=
6
> cycles). =A0I'm not familiar with electronics failure modes under fatigue=
 so
> YMMV.
>
> 3G's isn't that much unless it is causing resonance problems. =A0As a fir=
st
> pass test I would load the components to 9 Gs and see what falls off. You
> could spin it or attach an accelerometer to it and drop it onto a complia=
nt
> surface to generate the force (soft surface better than hard surface). =
=A0If
> that passes then go to 12 G's and if it survives you will have a decent
> safety factor.
>
> If it is safety critical or loosing it means big $, then it is off to the
> shaker table lab.
>
> Regards,
>
> Gordon Williams
>
>
> ----- Original Message -----
> From: "RussellMc" <apptechnz@gmail.com>
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Sent: Friday, October 22, 2010 11:40 PM
> Subject: Re: [EE] circuit board under vibration
>
>
>> 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) ...
>
>
> =A0I 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? =A0Loss 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.
>
>
> =A0 =A0Russell McMahon
>
>
> --
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