Phil,

Do you know the duration of the deceleration? That's a very important
parameter.

I know that a 1m drop onto a hard surface produces a ~650g shock load but
the duration is very short ~3ms. That's why you don't see failures in
consumer electronics when you knock them off the table. Naval specs to
simulate depth charges or mines specify something like 500g/50ms but you
don't see military electronics encased in potting compound. Do you know what
your spec relates to in real life?

I suspect that if you're only using small components you won't have to do
any potting - try taking a similar pcb and dropping onto it's edge onto a
pavement from 3m and see what happens. What may be more important is how the
PCB is supported in the casing. Make sure there are plenty of fixing points
and that none of the hole centres are less than 2 diameters from the board
edge.

Good luck!



> Hello Technetters,
>
> I am soon to design a PB for one of our customers that will be required
>  to
> withstand a shock load of approximately 1500 g's.
> Does anyone have any guidelines or advice on how to achieve this?
> I'm thinking of solid potting the assembly within a rigid structure as
>  one
> solution.
> Components are expected to include SMD discretes and BGAs.
> Of course there's the consideration of how hard the potting compound
>  needs
> to be and what it should be (epoxy, silicone elastomer), as well as what
> material the board should be made of, CTE considerations between the
>  board -
> components - compound - housing etc.
> Any advice would be most welcome.
>
>
> Phil Dutton C.I.D.
> Senior CAD Technician
> IPC Certified Interconnect Designer
>


Eric Christison

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------