Thank you for responding.

The problem is, someone is asking me about the MAXIMUM before
damage occurs, so I am quite interested in your statement that it
"tends to deform the fiberglass over time".

Where can I learn more about that?
Does any IPC document even mention it?
I wish there was such a thing as an "IPC index"... any IPC people listening?

thanks again, though
Jack


On 10/12/06, Stadem, Richard D. <[log in to unmask]> wrote:
>
> Hi, Jack
> I can tell you that typically the torque setting used for hardware on
> pwb assemblies is between 1 to 6 in/lbs. More than that tends to deform
> the fiberglass over time. Of course, it all depends on the type of board
> material, layer count, etc.
> It also depends on the application.
> Realize that a lot of relaxation occurs during any type of thermal
> excursion, and the hardware will loosen up. It is always a good idea to
> use a Bellville washer in conjunction with a serrated or star washer to
> continue to hold the torque. It is also a good idea to use Glyptol or
> some other threadlocker.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
> Sent: Thursday, October 12, 2006 1:54 PM
> To: [log in to unmask]
> Subject: [TN] Compression Limit on FR4?
>
> Does anyone know of any guidelines or recommendations that suggest a
> maximum limit on compressing board material?
>
> Can any damage occur by over-torque'n screws, for example?
>
> I've never heard anyone discuss that...
>
> Jack
>
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