Hi,
Out at APEX last week there was a paper about paste release from different
materials. I was surprised at the results. The Ni based materials had some
issues but try to get the paper.
Paper and Speaker:
Quantitative Evaluation of New Smt Stencil Materials Chrys Shea, Shea
Engineering Services
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Amol Kane
Sent: Tuesday, April 19, 2011 9:10 AM
To: [log in to unmask]
Subject: Re: [TN] Stencil Thickness
With a 6 mil and no reduction, you end up with area ratio of 0.69, which is
very close to the critical value of 0.66. I am assuming you will need to do
a reduction on the aperture size which put you under 0.66. you will lose
paste release repeatability below 0.66. You could go with a 5 mil step on
that part, or even 4 mils if the paste volume is sufficient for soldering.
Assuming a 2 mil reduction, your area ratio would be 0.7 with 5 mils (0.87
with 4 mils), which is still above the 0.66 threshold for laser cut
stainless. Also ask if the stencil house can use a Ni based alloy or newer
finer grain steel which gives smoother aperture walls as compared to
standard stainless, thereby improving release.
Amol Kane | Process Engineer
Catalyst Manufacturing Services, Inc.
941 Route 38, Owego NY 13827
Phone: (607) 687-7669 Extn 349 | Website: www.catalystems.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jean-Francois
Bissonnette
Sent: Tuesday, April 19, 2011 8:55 AM
To: [log in to unmask]
Subject: [TN] Stencil Thickness
Hello Technetters,
We have to order a stencil and I'm not too sure what to do in this
situation. I use IPC-7525A for selecting the stencil thickness. While 99%+
of the components are way within the Laser Range, 6mil thickness, there is a
component which leads are 11mil x 34mil. In the 6mil thickness chart, this
falls in the electroform range. What I'm a risking if I still select laser
cut, 6 mil thickness? What would you guys suggest?
Thanks to all!
JF
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