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March 2011

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TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 28 Mar 2011 13:17:42 -0700
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I must have missed it but what are the parts w/cracked solder joints
and how large are they?

John Maxwell

On Mon, 28 Mar 2011 15:46:16 -0400, Joyce Koo <[log in to unmask]> wrote:
> You have other problem: may be your PWB Tg is not suitable for the
> application. Let me guess: it should be polyimide board and got
> changed to FR4 for lower cost?
> --------------------------
> Sent using BlackBerry
> 
> 
> ----- Original Message -----
> From: Dale Hart [mailto:[log in to unmask]]
> Sent: Monday, March 28, 2011 03:01 PM
> To: [log in to unmask] <[log in to unmask]>
> 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
> 
> ______________________________________________________________________
> T


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