George,
Yes, it was only a couple pads where there had clearly been no connection
formed. I suspect there was some "Head In Pillow" but I have yet to see the
PCB myself. They also had some leaded BGAs on the board, they all soldered
fine. Pulling them tore the pads off the PCB and device.
I need to read through some of the doc I have located but I have been busy
writing code for another project.
Do you know if running at lower temps makes "Head In Pillow" worse? I
suspect so but I don't want to be guilty of letting hogwash cloud my
thinking!
Thanks,
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Thursday, October 04, 2012 8:17 PM
To: [log in to unmask]
Subject: Re: [TN] The Great Broken Via Mistery
Bob,
I assume that there must have been some sites where the solder on the pad
had wet, or at least partially wet, the BGA solder ball otherwise it would
have fallen off instead of having to be pulled off. Besides insufficient
wetting could there also have been a Head-On-Pillow issue?
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer Andrew Corporation - Wireless
Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, October 04, 2012 7:46 PM
To: [log in to unmask]
Subject: [TN] The Great Broken Via Mistery
Hi,
The other week I had posted about broken vias on an expensive PCB with
filled vias.
Well, let me inform folks about what really happened.
1. There were no bad vias. The profile used was low, only 221C at one
measured spot. They used leaded paste and lead free BGAs.
2. After pulling a part they found nice shiny reflowed pads and nice
round BGA balls that had never contacted.
3. Today they fluxed and reflowed a dead board and it came back to
life.
4. The Altera reflow process guidelines (AN 353) had errors in the
reflow tables. The Altera "Engineer" confirmed the data was good.
Now I don't know who started this Bad Via story but my guess is a CM how
screwed up doing a profile. Better to point fingers towards the board house
is my guess Their "Engineer" thought that if parts got to 250C they would
stop working. So using leaded paste on lead free parts was a really smart
move.
This is a classic case of people using data they think is good and forget to
think, ask and observe.
Such a big world, so many problem to solve and so much hogwash in so many
heads.
Bob K.
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