Hi John,
Our board cleaner is a roller-type machine (Teknek). In theory, the
roller picks up any stray contaminants on the PCB (fiberglass, etc.) and
deposits them to a sticky paper roll.
We're going to look into our reflow ovens this weekend and see if we can
find anything.
The stencil cleaning process has already been investigated and found to
be OK.
I don't know what else to do at the moment.
Leland
-----Original Message-----
From: John Burke [mailto:[log in to unmask]]
Sent: Friday, May 16, 2008 12:36 PM
To: Leland Woodall; 'TechNet E-Mail Forum'
Subject: RE: Stainless Steel Contamination Question - Update
Board cleaning machine??
Have you tried running something through the board cleaner which would
trap
particles if they are present??
Maybe run something like a pan scrubber (plastic) though the board
cleaner
and see if it traps residues.
It really does sound like the contamination may be being introduced by
some
of the equipment that was cleaned using steel wool at some time??
Cleaning
out the board cleaner?
As for the reflow system. Take a panel of anything, spray it with
photographic contact adhesive and run it through the reflow with all
fans
running with zero heat and see what sticks.
You forgot the screen printer. The contamination may be present on your
stencils/ screens - being introduced by contamination from the stencil
cleaner??
John
John Burke
(408) 515 4992
-----Original Message-----
From: Leland Woodall [mailto:[log in to unmask]]
Sent: Friday, May 16, 2008 9:06 AM
To: TechNet E-Mail Forum; John Burke
Subject: Stainless Steel Contamination Question - Update
Importance: High
Everyone,
Thanks for your previous help and suggestions, and hope you're having a
great Friday.
To update the group, there was another piece of this aggravating
material found last evening on third shift. It is consistent in size,
shape, and compositional analysis as the previous samples.
It was found prior to the conformal coating process, so I was able to
check the magnetic properties. It has none.
Unlike the others, this one was found on the bottom side of the board.
Removal of the material resulted in cracked flux and a slight visual
indication of an imprint of the wire on top of one of the effected
solder joints.
If I'm now thinking correctly (may not be, as this is wearing me down
fast), this was introduced to our product somewhere between our board
cleaning machine and the exit of our first reflow oven.
I intend to perform a solderability test this afternoon, laying a
portion of the sample in two adjacent paste deposits and checking the
results after reflow. I expect to see the sample still there, only
having floated to the top of the reflowed joints but still encased in
flux.
Am I missing anything, or do you have any other suggestions on what I
can do with this material in an attempt to identify the source?
Thanks again for all your feedback in advance.
Leland
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