Only method I have ever found that works is frequency swept vibration
testing of the final product while powered up and passing
signals...............
Your process engineer is right a 5 Dx will not find a micro fracture. You
will find it (once you suspect it is there) with Dage or similar high
resolution X-Ray equipment.
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rudolph yu
Sent: Monday, December 22, 2008 10:56 AM
To: [log in to unmask]
Subject: Re: [TN] What could be the root cause for a failed board that
passed functiona test after going through reflow for the 2nd time?
Besides performing a destructive test, what other method can be used to
detect microfacture on a solder joints?
According to our process engineer, the 5DX machine is not capble to catch an
hairline open..., and we already use it to inspect for any manufactuing
related defecs, but could not find any.
> Date: Mon, 22 Dec 2008 13:43:23 -0500> From: [log in to unmask]>
Subject: Re: [TN] What could be the root cause for a failed board that
passed functiona test after going through reflow for the 2nd time?> To:
[log in to unmask]> > Hmmmm,> > Familiar Story:> > Board Works, Board Ships,
Board Fails and is returned. Board works back at> factory. You simply added
a reflow cycle to "Fix" the problem.> > Next time you need to find out WHY a
bad bard is failing, making it "Work"> with magic or reflow does not allow
you to resolve the real problem.> > Bob Kondner> > > > > > -----Original
Message-----> From: TechNet [mailto:[log in to unmask]] On Behalf Of Rudolph
yu> Sent: Monday, December 22, 2008 1:35 PM> To: [log in to unmask]> Subject:
[TN] What could be the root cause for a failed board that passed> functiona
test after going through reflow for the 2nd time?> > Hi:> > We have a proto
assembly that passed the functional test initially. But> after we shipped it
to the customer, it failed at the their site for the> same kind of test.
After we received the board back, we reflowed it using> the same reflow
profile, and the board would funcation once again... > We checked the boards
under 5DX after we received it back from the customer> and found no defects
on it.> > What could be causing this? and why the assembly would pass the
test in the> first place? > > Here iare couple areas that I could think
of...but not sure if they are> valid.> > 1. Certain parts (microBGA) may be
better off to have underfill underneath> for thermal mismatch? ( Need to
check spec)> 2. During handling and shipping, the board may be stressed to a
degree that> a microfacture is formed.> > What other areas could cause this
problem.> > Thanks> Rudolph > > > > > >
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