More info

5 mil trace, 0.5oz Cu.  Board is 10 layer, .063"
The material is rated to IPC4101B/129.
Still trying to find out the reflow profile.
The board sees double-sided reflow.  Not sure if the BGA is on 1st or 2nd side.
There may also be a repetitive mechanical stress factor though, based on how the board is installed in the chassis.
Had occasional intermittents before, but now we have a few occurrences over a short period of time.  
A peel strength test apparently passed, but that was done on the board after the 2 reflow cycles.  Would that potentially influence the results if possibly the board material wasn't properly cured?


--- On Wed, 2/3/10, pearl petras <[log in to unmask]> wrote:

> From: pearl petras <[log in to unmask]>
> Subject: Re: [TN] track lifting
> To: [log in to unmask]
> Received: Wednesday, February 3, 2010, 10:26 AM
> I'll see what I can do to reply to
> all the questions.
> 676 ball,  1 mm pitch, 27mm sq
> tracks lifted on only one side of device.
> not all tracks lifted, and sometimes non-adjacent tracks
> lifted, which was a mystery to us, but if John is noticing
> some tracks are broken, that might explain it.  We
> hadn't noticed that yet.
> leadfree
> Has happened a few times.  We are trying to determine
> when in the process, now.  Unsure if during production
> or only after it leaves our facility.
> 
> 
> Thanks for all the replies so far.
> 
> 
> --- On Wed, 2/3/10, Leland Woodall <[log in to unmask]>
> wrote:
> 
> > From: Leland Woodall <[log in to unmask]>
> > Subject: Re: [TN] track lifting
> > To: [log in to unmask]
> > Received: Wednesday, February 3, 2010, 9:57 AM
> > Brian,
> > 
> > Was the strain you mention below originate from the
> reflow
> > process?  Was
> > it because of a thermal mismatch or an accelerated
> cooling
> > rate?
> > 
> > Just curious...
> > 
> > Leland
> > 
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]
> > On Behalf Of Brian Chandler
> > Sent: Wednesday, February 03, 2010 7:28 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] track lifting
> > 
> > We just conducted a study on acceptable strain levels
> for
> > lead free
> > products. 
> > Our BGA test coupons showed this exact result from
> excess
> > strain.
> > 
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