Steve,

The problem is very consistent and appears on all parts run.

John

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, April 23, 2009 11:43 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Ball Problem

Hi John,

Yeah, like I said when I sent you the links to your pictures, the last time
we had a bad solderball problem we got a bad lot of paste, and to our
vendors credit, they admitted the paste was bad. 

But I went back and looked at the picture of the solderball problem we had
(I learned a new term then, "snotballs", which was what our vendor called
it), and it doesn't look anything like your problem. Check out:

http://stevezeva.homestead.com/files/Snotballs.jpg

I have a question; do all of the boards during a run look like the pictures,
or do you get a few boards out of the run that look okay?

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Parsons
Sent: Thursday, April 23, 2009 1:16 PM
To: [log in to unmask]
Subject: [TN] Solder Ball Problem

I am trying to get to the root of a little solder ball problem.  The problem
is specific to a single part and was evident on the first run of this board
a few months ago.  We are seeing it again on this run although the common
denominator here is that the PCB's are all from the same production batch.

It appears that the formation of solder balls can be reduced by pre-baking
the PCB's (100°C for 4-8 hrs) but not eliminated.  The best results are
obtained by pre-conditioning the PCB's by running them through the reflow
oven first,  letting them cool, then print, populate and re-flow.  The
majority of balls now formed are dealt with at wash.

The PCB's are simple double sided, HASL finish.  I suspect a problem with
the solder finish (HASL) but what exactly that "problem" is I am not sure.
FYI, paste is water soluble.

http://stevezeva.homestead.com/files/Solder_ball_1.jpg - this photo is of a
board that was pre-baked for about 4 hours @ 100°C, it was then printed and
re-flowed.  It does not matter if the 4 hour bake improved things you can
see that the results are pretty spectacular.

The following pictures are really more of the same except that these boards
have been populated and washed. 

http://stevezeva.homestead.com/files/Solder_ball_2.jpg
 
http://stevezeva.homestead.com/files/Solder_ball_3.jpg
 
http://stevezeva.homestead.com/files/Solder_ball_4.jpg

Any insight would be appreciated.

(thanks to Steve for hosting the photos)

Regards
John Parsons

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