Hi,
What I have Seen:
Part placement squeezes paste causing small amounts of paste to be
separated from the main past deposit. During reflow isolated deposits form a
ball.
The "Home Plate" design for paste apertures helps minimize the paste
directly under the end cap or a small part. Less paste to get squeezed into
isolate sections.
One solder ball can be a problem. How many shorts does it take to cause a
failure?
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Wednesday, October 28, 2009 9:26 AM
To: [log in to unmask]
Subject: Re: [TN] Birth of a Solderball
One fly makes no summer. Is ONE solder ball a problem? We see small solder
balls frequently when the boards are inspected after wave or vapour
soldering. It's because the process is not 100% perfect. Out of billions of
solder particles, some singular escape and do not participate in the solder
melting. The reasons for that is many. We don't see the phenomenon as a
problem, because the 'free' solderballs use to vanish during the board
cleaning. The jet pressure is so high, that they can't stick to the board.
/Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Iven, Jowan
Sent: onsdag 28 oktober 2009 14:06
To: [log in to unmask]
Subject: Re: [TN] Birth of a Solderball
Hi Leland,
What about the location of the solderball?
Doesn't that give you enough information?
Where on the board was the solderball located?
Or did the problem occur somewere else but the board?
Jowan
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Wednesday, October 28, 2009 12:54 PM
To: [log in to unmask]
Subject: Birth of a Solderball
TechNetters,
Is there any possible way to determine the origin of a solder ball?
We've had a failure because of one, and we're trying to determine whether it
came from our SMT or wave soldering process.
We use SAC305 at both, so using the SEM to determine alloy composition is
not really helping.
The ball itself is spherical with no "tails" and quite shiny in appearance.
If we cross section the ball, will we see a difference in grain structure
due to the differences in cool down rates? Is there anything else we can
use or do?
Thanks in advance for your help!
Leland
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