I don't see why mirroring should cause any thermomechanical issues. Most of
the board's properties use to be determined by the copper profile and the
number of layers. I can't think that the copper network is an exact mirror,
but I may be wrong.

Inge

On 12 December 2012 00:42, Amol Kane <[log in to unmask]> wrote:

> Dave, are you at the liberty to share the citations?
>
> Regards,
> Amol
>
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
> Sent: Tuesday, December 11, 2012 3:35 PM
> To: [log in to unmask]
> Subject: Re: [TN] Data Concerning Solder Joint Integrity of Assemblies
> with "Mirrored BGA" Configuration
>
> Hi Inge! The TechNetee's lead me to a couple of older but good papers
> showing that having "mirrored" BGA or CSP components has an influence on
> solder joint integrity. It is a topic I wanted to explore since many
> product are now encountering this configuration as assembly size is getting
> much smaller than 10 years ago.  Lots of factors in play but the
> interaction of component configuration and board warpage is one of the
> topics described in the published literature.
>
> Dave
>
>
>
> From:   Inge Hernefjord <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   12/11/2012 04:43 PM
> Subject:        Re: [TN] Data Concerning Solder Joint Integrity of
> Assemblies with "Mirrored BGA" Configuration
> Sent by:        TechNet <[log in to unmask]>
>
>
>
>  Dave, what do they base that apprehension on?
> Inge
>
> On 21 November 2012 23:27, David D. Hillman
> <[log in to unmask]>wrote:
>
> > Hi gang! I have been looking for some data and am not having any great
> > success so I thought I would ask TechNet! I am looking for solder
> > joint integrity data for BGAs and CSPs where you have a two sided
> > board and
> the
> > BGAs or CSPs are "mirrored" (aka side one has a BGA exactly opposite
> > of
> a
> > BGA on side 2).  I have found publications discussing the impact of
> > mirrored BGAs due to rework but I am looking more specifically for the
> > influence of having a mirrored configuration  (or even a partially
> > mirrored configuration) on the solder joint integrity in thermal cycle
> > conditions. There seems to be some industry tribal knowledge that
> > having
> a
> > mirrored BGA/CSP configuration causes a degradation in solder joint
> > integrity but I am not finding supporting data in the industry
> literature.
> > If you know of any published papers/reports, please send me the
> > citation and I can run down the papers.
> >
> > TIA
> >
> > Dave Hillman
> > Rockwell Collins
> > [log in to unmask]
> >
> >
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