A potential problem with a negative wetting angle is that it can (but only can) have/form a stress concentrator....... I'm too. Can't prove it, but much points in that direction. I'm trying to find old reports on that. Too old maybe. The 5S gang whirl like a tornado, and when they have finished their patrol job, a lot is missing. I had to take job material to my home, in order not to let it go to the waste bin. Inge > -------------------------------------------------- From: "vladimir Igoshev" <[log in to unmask]> Sent: den 26 March 2010 06:48 To: <[log in to unmask]> Subject: Re: [TN] Need some opinions > Well, I'd say that the presence of a proper intermetallic layer in the > region is a good indication of a proper SMT process (re-flow profile), but > rather irrelevant to the negative wetting angle issue. > > A potential problem with a negative wetting angle is that it can (but only > can) have/form a stress concentrator. > > in some cases of a "generally" (at a low optical magnification) negative > wetting angle a close up view (couple of thousands magnification) shows > that there is a positive meniscus right at the surface. That one I > wouldn't fail. > > Regards, > > Vladimir > Vladimir > > SENTEC Testing Laboratory Inc. > 11 Canadian Road, Unit 7. > Scarborough, ON M1R 5G1 > Tel: (416) 899-1882 > Fax: (905) 882-8812 > www.sentec.ca > > -----Original Message----- > From: "Fox, Ian" <[log in to unmask]> > Date: Fri, 26 Mar 2010 09:20:08 > To: <[log in to unmask]> > Subject: Re: [TN] Need some opinions > > Bev, my feeling would be that if the other surfaces of the lead > exhibited proper wetting and the only issue was a bulbous heel fillet, > for the reasons you've outlined, and provided a cross section showed > proper intermetallic formation (I'm assuming Cu leads) in the heel > region then I don't think I would necessarily fail it on qualification. > It would though probably lead to confusion amongst operations personnel > with what is and isn't acceptable from an inspection standpoint and for > that reason I'd have to think about it. > > Regards > Ian > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian > Sent: 26 March 2010 01:58 > To: [log in to unmask] > Subject: Re: [TN] Need some opinions > > Steve, > Gull wings. > > Yes, cheap, cheap cheap! > > Bev > > ----- Original Message ----- > From: TechNet <[log in to unmask]> > To: [log in to unmask] <[log in to unmask]> > Sent: Thu Mar 25 21:49:18 2010 > Subject: Re: [TN] Need some opinions > > Hi Bev, > > Don't leave us hanging, what components are you seeing that with? I'd > like to have a "heads-up". > > This begs the question, why do you think they are doing that? Are things > getting so tight that they're trying to pinch a penny by reducing > plating coverage? Hmmmm... > > Steve > > ----- Original Message ----- > From: "Bev Christian" <[log in to unmask]> > To: <[log in to unmask]> > Sent: Thursday, March 25, 2010 9:08 PM > Subject: [TN] Need some opinions > > >> Technetters, >> It seems that more and more component suppliers are not plating their >> leads >> all the way up to the component body. In fact some are getting > downright >> skimpy and only plating to the bottom bend, never mind the upper one. > If >> you >> put down a lot of solder paste you end up with a bulbous joint, a > negative >> wetting angle and a stress concentration point. If you put down less > paste >> and have a co-planarity issue, then you have the potential for opens. > The >> other option of course is getting the supplier to plate higher up the >> leads. >> >> Question: would you consider the condition of the formation of the >> negative >> wetting angles a failure during process qualification? >> >> Bev >> RIM >> >> >> ______________________________________________________________________ >> 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 transmission (including any attachments) may contain confidential > information, privileged material (including material protected by the > solicitor-client or other applicable privileges), or constitute > non-public information. 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