hi Inge,
You must be hitting some Eigenfrequencies---by changing the vibrational characteristics you should be able to steer clear of the harmonics---I would think just staking the corners should do it.
Werner

 


 

 

-----Original Message-----
From: Inge <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Mar 12, 2010 1:47 pm
Subject: [TN] Vibration issue


Hi all, 
we are making a  very vital part for a aircraft builder. Problem with TQFPs, some 200 legs. There are resonance peaks that kill the package legs. Redesign is not to think of from the customer, so we must do something on inside of the box.  One solution (not popular) is to use a string of a glue along the leg rows in order to lock them.  Another is to place a vibration dampening mat on one side of the board. That one is more tricky , but  there is a US  company with lots of stuff for that purpose.  Anyone with experience from this area? I should add that not all legs are broken, just one or two after 100 hs of random vibration, but that is of course not acceptable.  BGAs would solve the problem, but there is no time for redesign. 
I'm sorry for coming with a  serious message at this holy time of the week. 
Thanks 
/Inge  
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