Tino,

There was a recent thread on Technet about this very same thing. Recent 
meaning within the past two weeks. Check out a listing and you may have 
your answer. I know that Werner and several others openly discussed this 
issue. It involved over compression of the device to the board and the 
extreme stresses placed at the corners. Unfortunately, I do not recall 
the final results.

I believe the 7351 is not addressing this as a universal problem.

Regards,

Gary Ferrari

Mike Hill wrote:
> Tino,
> 
> I saw this 5-6 years ago and it always occurred in the corners of the PGA.
> Either the traces cracked or the pads were torn from the base material.
> Adding the tear drops certainly will help.  It might also require matching
> the expansion of the component type to the board material.  I would default
> the failure mechanism and subject to Werner Engelmaier.
> 
> Mike Hill
> 
> -----Original Message-----
> From: IPC-600-6012 [mailto:[log in to unmask]]On Behalf Of Constantino
> Gonzalez
> Sent: Monday, December 22, 2008 10:04 PM
> To: [log in to unmask]
> Subject: [IPC-600-6012] Pad to trace interface on BGAs.
> Importance: High
> 
> 
> Hello, I have a customer with a problem described below, Could you PLEASE
> HELP ME?
> 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:
> 
> image001.gif   image002.gif
> 
> 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…
> 
> image003.gif
> 
> 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?
> 
> Regards.
> 
> Constantino J. González, ACME, INC. - GALUSAMEX REPAIR Co.
> President / Consultant Engineer - Official IPC MASTER INSTRUCTOR - IPC-A-610
> Committee Chairman
> USA Cell Phone: 605-381-5963 - Mexico Cell Phone: 55-2709 - 6392 -
> <mailto:[log in to unmask]> [log in to unmask] or  <mailto:[log in to unmask]>
> [log in to unmask]
> 
> Does your Company need Rework, Repair or Inspection of Electronic Assemblies
> Services.
> Do you have too much Rework, Scrap or Rejects from your Customer…..Call us,
> We can help!
> GALUSAMEX REPAIR Co.
>