I have not seen this problem, mainly because we are not running fine line
traces on the external layers.  If we did,  the teardrop would be added.
Our approach is to use a dog bone bga pad to via.




                                                                           
                                                                           
             "Constantino J.                                               
             Gonzalez"                                                     
             <[log in to unmask]                                          To 
             T>                        [log in to unmask]                
             Sent by:                                                   cc 
             IPC-600-6012                                                  
             <IPC-600-6012@IPC                                     Subject 
             .ORG>                     [IPC-600-6012] FW: Pad to trace     
                                       interface on BGAs.                  
                                                                           
             05/10/2007 12:39                                              
             PM                                                            
                                                                           
                                                                           
             Please respond to                                             
             "(Combined Forum                                              
               of D-33a and                                                
                   7-31a                                                   
              Subcommittees)"                                              
             <IPC-600-6012@IPC                                             
                   .ORG>                                                   
                                                                           
                                                                           
                                                                           




Hello, I have a customer with a problem described below, PLEASE HELP?

The problem is that several boards are being returned to the plant after
failing in the field.



After Failure Analysis the engineers have found that the reason for the
failure is that one of the traces of the PCB connected to a BGA pad is
becoming cracked (Micro crack at BGA Pad AJ29 in the corner of the BGA) as
showed in picture below:







They have concluded that Copper qty at PCB layer is not enough to support
the normal Mechanical Stress in the unit chassis during the Transportation
resulting in the trace and pad crack.

Based on Jedec JESD22B113 standard, they are suggesting that the customer
change design on the traces connected to BGA pads as shown below: Does the
IPC7351 suggest anything related to this.







I have not heard before about this type of junction from traces to pads,
and
being honest I did not know the Jedec STD mentioned.



Have any of you ever heard about this special union from traces to BGA pads
to avoid stress or any other recommendation to reinforce trace to pad
joints?

Could you please enlight me with your thoughts or opinions about this
issue?



Thanks,





 Constantino Gonzalez

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