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March 2008

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Subject:
Re: Solder Mask Defined Pad BGA Reliability
From:
"Thayer, Wayne" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Thayer, Wayne
Date:
Tue, 18 Mar 2008 12:58:58 -0400
Content-Type:
text/plain
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text/plain (52 lines) 
My thinking is that I want to separate the amount of metal surface area in contact with the base laminate material from the diameter of the pad.  Most guidelines suggest making a ball symmetrical top to bottom:  Make the reflowed area of the pad pretty close to the area on the BGA you are planning to put down.
 
Sometimes, as I indicated previously in this thread, the two coincide:  The largest pad I can put down is the same as exposed pad desired for the reflowed ball.  But sometimes I can get away with a significantly larger pad.
 
Wayne

________________________________

From: TechNet on behalf of Werner Engelmaier /*
Sent: Tue 3/18/2008 12:49 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Mask Defined Pad BGA Reliability



Hi Wayne,
I am all for larger pads-but why do you think SMD pads have less pad
lift-offs then non-SMDs?



Werner



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