Hi Steve! Greetings from the snowy north east!
Cool F16 exit picture.
I agree with John Maxwell's assessment. (which, realistically, is about
the same as a high school physics teacher saying he agrees with
Einstein...). We just built a new board with some tantalum capacitors
on it, where the pad design was a touch wide and the outside end of the
pads were too close together - pretty much the same as your picture,
although our pads weren't quite that wide.
We placed the parts perfectly lined up, and on reflow they all skewed
somewhat. The surface tension of the solder would pull the part either
clockwise or counter clockwise, and orient it so that the end joint was
as fat as possible.
Our conclusion was the same as yours, not a defect because the parts
are 100% on the pads. If the board gets re-spun I will request that the
pad dimensions be modified so as to put the outside edges a bit farther
apart.
regards,
Graham Collins
Process Engineer,
Northrop Grumman Canada Corporation
Halifax
(902) 873-2000 ext 6215
>>> [log in to unmask] 02/24/04 06:33PM >>>
Hi All!
Got a little issue here that I need to dig in deeper to, but I thought
I'd
post a picture on my web page and ask for your valued opinions. Was
building a
board today that we've built before, never had any problems with it.
But today
certain 0805 resistors started skewing on their pads during reflow,
and I
don't know why. Take a look at:
http://www.stevezeva.homestead.com and look at "skewed components".
It's not
really a defect because they're 100% on the pads, and the wetting and
fillets
are fine too. They just look funky...and this just started happening.
Not so
much as a pimple on the boards before when we built them.
As I said, there's more that I have to dig into, but thought maybe
someone
might have had this happen before, and can go; "A-ha Steve! you need to
do
this...."
Also, I've posted a pretty awesome picture on my page. Take a look at
"F-16
Exit".
A photographer just happened to be at the right place, at the right
time,
with the right lense on his camera, the right F-stop, and everything in
focus to
take this picture...this truly is a once in a lifetime picture.
The picture was taken from the tower at Mountain Home AFB in September
last
year at the air show they have there, the Thunderbirds were
demonstrating.
The aircraft was one of the two on the Thunderbird team that flies solo
most
of the show, the other 4 aircraft fly in formation.
This aircraft had just done a high performance take-off straight-up,
and then
did a split S into a loop, and was just about to round out the loop at
the
bottom and pass show center, when the engine started spitting out
turbine
blades. There was no power to stop the huge rate of decent of the
aircraft, so the
pilot punched out at about 100-feet altitude, and the photographer
snapped the
picture.
-Steve Gregory-
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