Hi Geordie,

I presume there's a stiffener underneath the BGA device? Provided it's substantial enough eg, steel or
FR4 rather than polyimide AND it extends a little way past the ball pattern the design should be
reasonably robust.

Do you also underfill the BGA?

Regards,



[log in to unmask] wrote:

> I guess my first question is why are you mounting the BGA  a flex circuit ??
> The potential for fractures due to lack of a strain relief is HUGH.  Really
> need a solid surface to mount the BGA to.
>
> Randy Bock Sr.
> Quality Manage
> Bryce Office Systems LLC
> email [log in to unmask]
>
> ----- Original Message -----
> From: Alfson, Geordie (STP) <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, April 09, 2002 3:50 PM
> Subject: [TN] BGA flex circuit failure
>
> > Greetings,
> >
> > I work as a test engineer for a medical device maker. I found this forum
> by
> > way of the Circuits Assembly web site.
> >
> > My area of concern, as a test engineer, is the probing of test pads on
> > flexible double sided PCA's, especially when test pads are located on the
> > opposite side of a BGA. I am concerned that the probing force may result
> in
> > 1)solder joint fracture 2) de-lamination of the PCA 3) dislodgement of
> > components, just to name a few.
> >
> > Do you know of any research (published papers) or colleagues with
> knowledge
> > in this area of flex circuits that can assist me. I want to establish test
> > pin density and force limits and board layout criteria so I (hopefully)
> can
> > prevent PCA failure at the testing phase.
> >
> > Thank you
> >
> > Geordie Alfson
> > [log in to unmask]
> > Test Fixture Mechanical Engineer
> > Guidant Corp
> > Tel 651-582-7635  Fax 651-582-7599
> >
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--
Eric Christison
Mechanical Engineer
STMicroelectronics
33 Pinkhill
Edinburgh
EH12 7BF

Tel: (0)131 336 6165
Fax: (0)131 336 6001

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