Qfn vendor usually tell you what thickness of stencil to use with what size of opening. How was that recommendation compare to your design?
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----- Original Message -----
From: Roger Mack [mailto:[log in to unmask]]
Sent: Thursday, August 19, 2010 10:51 AM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Bulging solder on the sides of QFP leads
Have you measured the actual pad widths? If your design has a 20mil pitch
part with 10mil pads, you will likely have a much narrower pad at the
surface on a 3 oz. board. If your stencil design was for a 10mil pad you
may have poor gasketing and be depositting more paste than you intended
to.
Roger Mack P.Eng.
Manufacturing Specialist
Parker Hannifin Electronic Controls
Electronic Controls Division
1305 Clarence Avenue
Winnipeg, MB R3T 1T4 Canada
direct 204 453 3339 x373
[log in to unmask]
www.parker.com/ecd
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
08-19-2010 08:34
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TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Ioan Tempea <[log in to unmask]>
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Re: [TN] Bulging solder on the sides of QFP leads
Thanks again!
To get back a bit to Steve's observation: the boards indeed have 2 layers
of soldermask. But it has 3oz of Cu on all the layers.
Would it be necessary to have 2 layers of SM, just because of the
thickness of the traces?
If not, why would one lay down extra SM?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask]
W | www.digico.cc
N'imprimer que si nécessaire - Print only if you must
-----Message d'origine-----
De : Guy Ramsey [mailto:[log in to unmask]]
Envoyé : August-19-10 9:26 AM
À : [log in to unmask]
Objet : Re: [TN] Bulging solder on the sides of QFP leads
No, I would not consider it a defect, given the information you have
provided.
IMHO, it is better to optimize toward excess solder than insufficient.
Solder shorts are obvious and easy to troubleshoot, compared to
troubleshooting an intermittent insufficient solder joint.
Guy
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