Dale,
In all likelihood, the root cause of your SJ failures is the encapsulant.
Werner

 


 

 

-----Original Message-----
From: Dale Hart <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Mar 28, 2011 3:01 pm
Subject: [TN] Solder joint height control


Thanks all for the responses.



The reason for my interest, we were having numerous units returned from the 

field.  Analysis revealed cracked solder joints on the board.  It was learned 

the units were occasionaly being subjected to a 20C per minute thermal cycle out 



in the field.  The field failure was also subsequently verified by lab testing.



The units are encapsulated for vibration protection so our thoughts were to get 

as robust a solder joint as possible and make sure the CTE and modulus at the 

temperature extremes were as benign as possible.



I remember when we had real components on the board (poke through) and the 

module had to encapsulated with a hard polymer a buffer coating was applied 

(possibly silicone) before encapsulation to help reduce the forces on the 

components, is this technique still in packaging folks play book?



Dale Hart

UTC



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