Friday already?
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Ahne Oosterhof
Skickat: den 18 oktober 2005 21:43
Till: [log in to unmask]
Ämne: Re: [TN] SV: [TN] Voids in BGAs, again
Yup, osteoporosis.
Need more calcium.
Ahne.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, October 18, 2005 12:12
To: [log in to unmask]
Subject: Re: [TN] SV: [TN] Voids in BGAs, again
Hi Inge!
Got your pictures up finally. It's funny that you mention a FeinFocus
x-ray,
we just got our Tiger 160 installed today, and that's what I've been
doing
most of the day...learning how to use it. New toys!!! WOO-HOO!!
Go to: http://www.stevezeva.homestead.com and look for; "Fresh Ball, and
Corroded Ball - Corroded Ball 3".
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
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| Subject: [TN] SV: [TN] Voids in BGAs, again
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That is probably what we experienced some years ago. FineFocus X-raying
showed what seemed to be voids, but analysis gave that some positions
under
the BGAs had a 'white residue' around the balls...and..those balls were
severely corroded. We tried to analyse the white residues, but did not
succeed very well. Concoat told us, that they have registered as many as
16
chemical compunds called white residues. GEC have found 20.
The most viable explanation was adipid acid from flux inclusions. Water
dropltes from the cleaning process stuck to the white residue, and lead
was
solved from the balls. After adjustments of the paste printing and use
of
Magic D7L, we could reuse the boards and have them accepted.
Analysis of the balls on new packages and failed ones showed that there
is a
zone which is especially sensitive to corrosion, but that's a long story
with many involved.
I'll ask Steve to put up some dirty pictures, that show a fresh ball and
corroded ones.
Ingemar Hernefjord
Ericsson Microwave Systems
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Dehoyos, Ramon
Skickat: den 18 oktober 2005 15:30
Till: [log in to unmask]
Ämne: Re: [TN] Voids in BGAs, again
Flux contains acids that when fully activated turn into inert
chemicals. It is the acids that when not fully activated that corrode,
so
acids will corrode metals whether they are trapped or not. Salts with
moisture and voltage make dendrites. They do need free areas to grow.
In
other words salts and resins or rosins will not cause any trouble when
they
are trapped. For the most part with a good reflow profile that activates
all
the acids of the flux will cause no harm if trapped in a solder joint.
My
two non chemistry cents
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard
Sent: Tuesday, October 18, 2005 9:02 AM
To: [log in to unmask]
Subject: Re: [TN] Voids in BGAs, again
Technet,
Just wanted to say, yes, very few failures have occurred due to voiding,
and
the situations I pointed out were extreme situations. But the interposer
attachment failures I described have also happened to others in not very
severe conditions. There is something about interposer attached parts
and
voids that do not mix well.
Ioan, I may be mistaken, but I was told that flux entrapped inside of
voids
is nothing to worry about because corrosion cannot occur due to a lack
of
oxygen. The voids are sealed. Any chemical or metallurgical engineers
out
there care to respond to this? I would like to know if that is true.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
Sent: Tuesday, October 18, 2005 7:32 AM
To: [log in to unmask]
Subject: Re: [TN] Voids in BGAs, again
Concur with Richard,
good document, professional and academic. But if I am not mistakening,
it
does not mention real failures from voiding.
BTW, your experience is very well appreciated, extreme conditions, bad
voids. I am wondering if regular testing, like HALT and the others
caused
joints to fail due to voiding.
What about failures due to chemistries, WS flux entrapped into voids
that
corrode their way out?
Best regards,
Ioan
> -----Original Message-----
> From: TechNet [SMTP:[log in to unmask]] On Behalf Of Stadem, Richard
> Sent: Tuesday, October 18, 2005 8:14 AM
> To: [log in to unmask]
> Subject: Re: [TN] Voids in BGAs, again
>
> Thank you Steve!
> This is an excellent and informational document. Thank you for posting
> it.
>
>
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