Ryan,
I think that alloy composition is part of the formula. Lead-free solder
wetting forces are different and the reflow temp is higher, which could lead
to additional slumping. I have found in my experience that the stencil has
to change due to the change in alloy composition which affects other parts
of the entire process. In the asking of my original question I was wondering
if others were having similar experiences.              Joel

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Ryan Grant
Sent: Friday, December 23, 2005 12:57 PM
To: [log in to unmask]
Subject: Re: [LF] Stencil Design for Fine-Pitch Lead-Free

Joel, I'm afraid your question has nothing to do with alloy composition
of solder.  Aperture size is dictated by the flux rheology and will vary
by each formulation.  The good news is there isn't any change in
aperture size when switching to lead-free, other than the usual fine
tuning for whatever paste formulation you choose.

Ryan Grant

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Joel Mearig
Sent: Thursday, December 15, 2005 3:48 PM
To: [log in to unmask]
Subject: [LF] Stencil Design for Fine-Pitch Lead-Free

I am looking for information regarding stencil design for fine-pitch
lead-free applications. I am interested to see what most people are
doing
for the aperture size. Are you reducing or going 1 to 1? If you are
reducing
what is the reduction formula? Are you reducing the same regardless of
aperture stance to print direction? Any input would be much appreciated.



Joel Mearig

Delta Tau Data Systems, Inc.


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