There are about six failure modes that can occur with a four stack
microvia on a buried.

Because the microvias are stacked on a buried via pad rotation on the
microvia is up rather than down. 

There is microvia to target pad separation, corner cracks on the filled
microvia (where the fill dips down there will be a thin copper at the
knee) , copper pull out (crack around the base of the microvia on the
cap of the buried, wrap crack, cap lift and cap crack just beside the
knee of the buried via.

Tell us that this is a lead free application.




Sincerely, 
Paul Reid 

Program Coordinator 
PWB Interconnect Solutions Inc. 
235 Stafford Rd., West, Unit 103 
Nepean, Ontario 
Canada, K2H 9C1 
613 596 4244 ext. 229 
Skype paul_reid_pwb 
[log in to unmask] <mailto:[log in to unmask]> 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: February 9, 2011 12:13 PM
To: [log in to unmask]
Subject: [TN] Thermal shock, IPC-TM-650 sec 2.6.8 ot 2.6.27

Folks,

   Given:
-        FR4
-       Th.  0.094 inch
-       Layer Count   20
-       Technology
o       4 tier totem pole stack micro vias
o       Buried conductive filled blind vias
-        Post 3x and 6x solder float test
-        Cross section

What are some of the expected anomaly to look for?

Victor,


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