At 0.5mm pitch we've had BGA voids large enough to cause adjacent balls to
bridge. In those cases, it was usually the result of a uVia plating defect
(uVia in the pad). Makes for an interesting cross-section.
dw
At 06:30 AM 10/18/2005, you wrote:
> 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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