Wee Mei:
On the bolt head side, use a flat washer. On the nut
side, use flat washer, lock washer and lastly the nut. The lock washer
regardless of the type, star, split.. should not deform the PWB.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wee Mei
Sent: Thursday, October 12, 2006 6:46 PM
To: [log in to unmask]
Subject: Re: [TN] Compression Limit on FR4?
Hello,
I happen to be trouble with screws and nuts on the PCBA recently. Can
someone point to a site to show how mechanical hardware assembly
installation is carried out on PCBA?
I have come across all sort of assembly configuration on just the screw,
washers and nut on PCBA that I did not know which is correct. Different
engineers used different method and even different screw or nuts on the
same build PCBA. What should be correct hardware assembly configuration.
Thanks and regards,
Wee Mei
----- Original Message -----
From: "Stadem, Richard D." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, October 13, 2006 3:02 AM
Subject: Re: [TN] Compression Limit on FR4?
> 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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