Something to check, if it was sheared off, there should be scuff marks on the board. A consistent clean shear is very unlikely. Do not forget to use high magnification to look for this sign. Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Barmuta, Michael Sent: Friday, January 12, 2007 10:32 AM To: [log in to unmask] Subject: Re: [TN] SMD Capacitor Shear Strength Rick: Yes, it definitely can be caused by operator handling or better worded mishandling. Let me add to some of the comments made by others. It usually occurs on parts located towards the outer edge of the board. Also smaller parts simply do not have as much soldered surface area as larger parts so the are more easily knocked off with less force. The three primary areas we have seen this problem are at: * The exit end of the reflow and/or wavesolder conveyor. Operators not paying attention, allow boards to stack up and slide over one another, shearing off components. To alleviate this we poke oke'd it by installing a proximity switch and alarm. So if the first board is not removed before the second board arrives it activates an audio visual signal. * Operators sliding boards into transfer carts with sharp edges or protrusions. These sharp edges act like a guillotine and break off the part. We have switched to carts that do not have this style of construction or we have modified them to eliminate it. * Transport totes with vertical dividers. If operators are not careful in how they load or place the board in the tote they can catch a part on the edge of the divider and knock it off. We install a rolled soft rubber edging over the dividers to minimize the impact. The best way to find out where it is happening is to work your way backwards from the end of the process until start seeing missing parts. Example, look at the end of the reflow for parts on the floor and surrounding area. Look at were they are loading boards into carts or totes are there components in the bottom or on the floor, etc. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Todd, Richard Sent: Friday, January 12, 2007 6:46 AM To: [log in to unmask] Subject: Re: [TN] SMD Capacitor Shear Strength Ramon, I couldn't agree more. I have looked at the solder joint areas. I do not see any evidence that the solder joints did not wet properly nor had voiding. I am trying to build a case against this being caused by operator handling. Something more nefarious is at work. Regards, Rick Panasonic Automotive Systems Hi Rick: Take a look at the missing component area on the board. Look at the solder joint areas. Look for voids or signs of poor wetting. Make sure that the components have a good metal wettable termination finish. I suspect that those caps are old and oxidized. A well soldered cap would not pry off easily when someone is trying to remove it by force. Regards, Ramon -----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 ----------------------------------------------------- This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. 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