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
[log in to unmask]
cc
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]>
To
[log in to unmask]
cc
Subject
[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
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
--------------------------------------------------------------------------
This message (and any attachment) is confidential and is intended for the named recipient only.
If you receive it in error please e-mail back the sender and permanently delete the original message and any copies.
Rolls-Royce Goodrich Engine Control Systems Limited.
Registered Office: Moor Lane, PO Box 31, Derby, DE24 8BJ.
Registered in England No. 06686268.
--------------------------------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
