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August 2010

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Wed, 18 Aug 2010 11:34:29 -0500
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TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
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Victor Hernandez <[log in to unmask]>
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Ian,

   Is there supporting articles on the acrylic coating and temps at or below 10 degree C.

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Fox, Ian
Sent: Wednesday, August 18, 2010 10:45 AM
To: [log in to unmask]
Subject: Re: [TN] Bulging solder on the sides of QFP leads

I agree with Dave on this one generally a small amount of midriff bulge is nothing to worry about. As a bit of additional information though, if your bulging reduces the dielectric separation down to about 50% of the design dimension i.e. still visually OK and you use an acrylic coating, and if your assembly spends significant periods of time at 10degC or below you can get solder extrusion occurring. The bulged joints will naturally retain more coating than none bulged joints and the modulus of the acrylic goes through the roof below 10degC and the compressive stress generated as a result will extrude solder out of the joints and will eventually produce a short.

Been there and got that particular T-shirt

Regards
Ian

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: 18 August 2010 16:09
To: [log in to unmask]
Subject: Re: [TN] Bulging solder on the sides of QFP leads

Hi Ioan - you might reduce the solder print volume slightly to reduce the bulge. As Leland detailed, if the bulge does not cause any workmanship inspection or functional issues, it would not be considered a problem.

Dave Hillman
Rockwell Collins
[log in to unmask]




Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
08/18/2010 09:36 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to Ioan Tempea <[log in to unmask]>


To
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Subject
Re: [TN] Bulging solder on the sides of QFP leads






20 mil pitch, 10 mil wide and 5 mils longer than pad length apertures, 6 
mil stencil

 

Thanks,

 

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]> 
W | www.digico.cc <http://www.digico.cc/> 

 
 N'imprimer que si nécessaire - Print only if you must

 

De : [log in to unmask] [mailto:[log in to unmask]] 
Envoyé : August-18-10 10:32 AM
À : TechNet E-Mail Forum; Ioan Tempea
Cc : [log in to unmask]
Objet : Re: [TN] Bulging solder on the sides of QFP leads

 


Hi Ioan - what stencil thickness did you use and what stencil aperture 
scheme did you use? 

Dave Hillman 
Rockwell Collins 
[log in to unmask] 



Ioan Tempea <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]> 

08/18/2010 09:27 AM 

Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Ioan Tempea <[log in to unmask]>

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[TN] Bulging solder on the sides of QFP leads

 

 




Dear Technos,



Please see the gallery http://ipc-technet.groupsite.com/gallery/14996



There seems to be an excess of solder, hence the bulging aspect of the 
joints along the pins. Can there be any issue with this? IPC-A-610 does 
not seem to be concerned with this situation, as long as the minimal 
electrical clearance is not violated, and it's not.



Thanks,



Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]> 
W | www.digico.cc <http://www.digico.cc/> 


N'imprimer que si nécessaire - Print only if you must




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