Are the caps near the edge?
I would think a part at the edge of the board is
more likely to get knocked off than in the center of the PCBA.
I have also seen parts very close to the edge of the PCBA get
knocked off by the deep slots in the card racks being used .
Just some ideas.
dave
Jerry Dengler wrote:
>Hi Rick,
>
>It's very hard to get a well solder 0603 off of the board through what I
>would call normal handling. However I have seen cases where PCB are
>allowed to fall out of an oven or wave solder machine and occasionally
>the falling board will catch a board sitting there just right to shear
>components off.
>
>Regards,
>
>Jerry Dengler
>Production Manager
>Pergamon Corporation
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Todd, Richard
>Sent: Friday, January 12, 2007 9:23 AM
>To: [log in to unmask]
>Subject: Re: [TN] SMD Capacitor Shear Strength
>
>Hi Werner, Hi John, Hi Steven -
>
>Thank you for your responses.
>
>I regards to the question of "Why?" We are experiencing some capacitors
>that are broken off of the PCB; not a lot, just a few. The prevailing
>wisdom is that during physical handling of the PCB, an operator is
>inadvertently breaking the parts off the board. This suggestion
>prompted me to think about the shear (or peel) force required to break
>the solder joint of a 0603 capacitor.
>
>My original question was not prompted by a concern for the reliability
>of the solder joint, but simply whether or not an operator, under normal
>conditions, can exert enough force on a low-profile device to break the
>solder bond.
>
>
>
>By the way, I failed to mention that our surface finish is HASL.
>
>
>
>Regards,
>
>
>
>Rick Todd
>
>Senior Engineer
>
>Process Quality Engineering
>
>
>
>Panasonic Automotive Systems Company of America
>
>Division of Panasonic Corporation of North America
>
>776 Highway 74 South, Peachtree City, GA 30269
>
>770-515-1087 Direct
>
>678-458-2887 Cell
>
>770-486-2248 Fax
>
>[log in to unmask] <mailto:[log in to unmask]>
>
>
>
> _____
>
>From: [log in to unmask] [mailto:[log in to unmask]]
>Sent: Thursday, January 11, 2007 9:37 PM
>To: [log in to unmask]; [log in to unmask]
>Subject: Re: [TN] SMD Capacitor Shear Strength
>
>
>
>Hi Rick, hi John,
>I am indeed on line-are not all consultants working 24/7?
>Whenever the shear/pull stength question comes up, my first reaction is
>'Why?'
>Here is my standard answer:
>No standards on shear/pull tests exist-nor should they exist. And there
>are good reasons none exist.
>First, there cannot be such thing as a true 'shear/pull test;' while you
>are of course stressing the solder joint, what you are doing to the
>solder joint in most cases is primarily peeling it-the proper reference
>would be a 'peeling' test.
>Second, the solder joint strength, as determined by a lead peeling test,
>has no bearing on the reliability of the solder joint, provided the
>peeling test does not reveal inadequate wetting or poor metallization,
>e.g., 'Black Pad.'
>Third, in a peeling test you always need to observe the whole peel-load
>history for the whole peeling process; e.g., with a leaded solder joint
>the largest load will be at the initial portion of peeling through the
>heel fillet, with lower loads subsequently depending on whether or not
>(or to what extent) side fillets are present.
>Fourth, the fracture surfaces of the peeled solder joints give typically
>more information than do the peel-load histories, because the ONLY
>really important finding is whether or not adequate wetting has taken
>place, i.e.
>the separation is mostly in the solder vs. being interfacial; or whether
>or not the metallization is the 'weakest' link, i.e. the separation is
>between metallization layers. Good quality solder joints frequently
>cause failure between the soldering pad and the component/PCB resin
>matrix.
>Fifth, for leaded solder joints, the reliability in actual use does to a
>large extent depend on the heel fillet and the 'bottom flat' wetting; if
>the foot length is <3W, than also on the presence of a toe fillet,
>because short feet 'rock' during thermal cycling. Side fillets are less
>important, unless you have wetting problems.
>
>Regards,
>Werner Engelmaier
>Engelmaier Associates, L.C.
>Electronic Packaging, Interconnection and Reliability Consulting
>7 Jasmine Run
>Ormond Beach, FL 32174 USA
>Phone: 386-437-8747, Cell: 386-316-5904
>E-mail: [log in to unmask], Website: www.engelmaier.com
>
>
>
>
>---------------------------------------------------
>Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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
>-----------------------------------------------------
>
>---------------------------------------------------
>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
>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
>-----------------------------------------------------
>
>
>
--
Dave Seymour, CID+
Catapult Communications Inc.
800 Perimeter Park Dr, Suite A
Morrisville, NC 27560
Direct: (919)653-4249
Main: (919)653-4180
Fax: (919)653-4297
[log in to unmask]
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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
-----------------------------------------------------
|
