Hi, Earl,
What a neat castration job!
Observations:
1) Ball adhesion to the package only seems to have been at the perimeter.
2) Some voiding but nothing too detrimental.
3) Focus on the board-end SJ's isn't so good, but although they look well
wetted and formed, they look a bit barrel-shaped themselves, not filleted
nicely to the balls (unless that's an optical illusion or trick of the
light).
4) Lots of barnacles and whiskers appearing on the balls in picture #3.
5) The bottom right quarter of picture 1 shows a reddish glow - is this
reflection of the hell fire that caused this problem?
6) The brown deposits among the balls in picture 1, I took to be substrate
remains, but the close-up view in picture 2 makes me doubt that.
Questions:
1) Is this the only thermally massive component on the board, or are there
others? How are they distributed?
2) What thermal profiling, temp cycling, rework has the board been through?
3) How old is the BGA?
4) Do you know what the brown deposits are?
5) Under what conditions was the BGA so summarily neutered? Vibration?
Sudden shock (e.g. dropped)? It just came off in my hand, honest!?
6) Are these eutectic balls (PBGA's) or HMP (CBGA's)?
7) Is the soldering process clean or no-clean?
8) Is the board double sided, and subjected to two reflows? And are there
then and through-hole parts that are wave soldered? How many times has this
poor specimen been through the oven, or at least near-reflow temp?
Opinion:
Neither very academic, nor drawn from the wisdom and knowledge of great
experience, but you may have the result of a component that's been around a
while (IMC build-up between balls and component body, causing poor adhesion
to the substrate) being soldered using a profile that may be too low temp
for too long.
I had a couple of boards last year that failed vibration testing very
quickly and the balls looked a bit like those in the pics - maybe not quite
so 'warty' but showing as very coarse and full of striations as if
partially reflowed and solidified again.
Have you done any sections on this one yet? An ESM picture of the result
might be interesting, especially at the interfaces.
Peter
SteveZeva@AOL
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Sent by: cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST
TechNet Aero/ST Group)
<[log in to unmask] Subject: Re: [TN] REALLY EXCITING STUFF AND A
ORG> BUG IN MY CAVE
02/27/02
10:57 PM
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Hey Earl!
The pic's are up! Go to:
http://www.stevezeva.homestead.com
(I spelt it right this time...hehehe)
-Steve Gregory-
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