Hi Leif!

I have your pictures posted. Go to:

http://stevezeva.homestead.com/files/air_bubbles_and_craters_1.jpg

http://stevezeva.homestead.com/files/air_bubbles_and_craters_2.jpg

Is the percentage of metals the same as your leaded paste? I also think
the rheology the paste won't be the same with as it is with the leaded
paste, so there will most likely have to be changes with the set-up of
the print. It almost looks like the separation speed is too fast, and
the paste isn't given time to pull away from the inside of the apertures
causing the crater...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leif Erik Laerum
Sent: Wednesday, July 30, 2008 8:29 AM
To: [log in to unmask]
Subject: [TN] Solder Paste with craters.

Technetters,

We are having an issue with solder fines on our lead free boards. We are
using SAC305 WS and no nitrogen. I noticed that our boards have craters
in the paste on the pads after being printed. Not all pads are deposited
this way, but maybe 25%. These craters have an air bubble in them. The
bubbles usually burst before the boards goes into the P&P, but the
crater stays. The screening process is exactly the same for leaded and
unleaded paste. The leaded paste does not behave this way. Could these
craters be a symptom of the cause of the solder fines? Anyone have any
experience with this?

How do I go about posting pictures to stevezeva.homestead.com?.


--
Leif Erik Laerum
Quality Assurance Manager
Texas Memory Systems
[log in to unmask]
Tel: (713) 266-3200 x468
www.texmemsys.com

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