Hi Vlad - all true but you are not accounting for incidental transfer of tin from contact with the assembly or the soldering process. Just because the toe is most likely a shear surface and is not wettable, doesn't mean that an SEM analysis wouldn't pick up Sn. Leland should be able to easily distinguish what surface he is analyzing by careful selection of SEM collection area. Dave "vladimir Igoshev" <[log in to unmask]> 03/27/2012 05:30 PM Please respond to [log in to unmask] To [log in to unmask] cc "TechNet E-Mail Forum" <[log in to unmask]> Subject Re: [TN] Rework Concern and Question Hi Dave,With all due respect I completely disagree. What you are saying is applicable in case the plating finish if thin (below 1 micron). But if someone analysts the toe of a lead, all the person should see is only the elements of the lead material, as there is no plating on the toe surface due to the way it's normally made. VladimirSENTEC Testing Laboratory Inc.11 Canadian Road, Unit 7.Scarborough, ON M1R 5G1Tel: (416) 899-1882Fax: (905) 882-8812www.sentec.ca From: [log in to unmask] Date: Tue, 27 Mar 2012 17:11:05 -0500 To: <[log in to unmask]> Cc: TechNet E-Mail Forum<[log in to unmask]> Subject: Re: [TN] Rework Concern and Question Hi Vlad - it depends on the selected analysis location and the kV selection they used during the analysis. Dave "vladimir Igoshev" <[log in to unmask]> 03/27/2012 03:25 PM Please respond to [log in to unmask] To "TechNet E-Mail Forum" <[log in to unmask]>, [log in to unmask] cc Subject Re: [TN] Rework Concern and Question Dave, if they did that then they wouldn't have seen Sn as leads are usually chopped off. 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: "David D. Hillman" <[log in to unmask]> Sender: TechNet <[log in to unmask]> Date: Tue, 27 Mar 2012 15:05:00 To: <[log in to unmask]> Reply-To: TechNet E-Mail Forum <[log in to unmask]>, <[log in to unmask]> Subject: Re: [TN] Rework Concern and Question Hi Leland - I recommend you find out the lead base metal composition. If you shot an SEM-EDS of the lead toe, you could be getting the Si from the base metal composition and not part of the solder alloy composition. Dave Hillman Rockwell Collins [log in to unmask] Leland Woodall <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 03/27/2012 02:52 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Leland Woodall <[log in to unmask]> To <[log in to unmask]> cc Subject Re: [TN] Rework Concern and Question Vladimir, We analyzed raw components straight out of the tape and reel packaging. The site selection was on the bottom side of the leads at the toe. Leland -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev Sent: Tuesday, March 27, 2012 3:12 PM To: [log in to unmask] Subject: Re: [TN] Rework Concern and Question Sorry Ben, it doesn't. Leland, What you are saying sounds strange. What does it mean: "We've analyzed the lead material beneath the SEM and it returns 98% tin and 2% silicone"? Did you analyzed leads or solder? Where the analysis was taken from? Did you analyzed leads with pads ripped off? Regards, 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: "Gumpert, Ben" <[log in to unmask]> Sender: TechNet <[log in to unmask]> Date: Tue, 27 Mar 2012 18:58:21 To: <[log in to unmask]> Reply-To: TechNet E-Mail Forum <[log in to unmask]>, "Gumpert, Ben" <[log in to unmask]> Subject: Re: [TN] Rework Concern and Question Leland, I won't claim to be an expert, but this website seems to imply something along those lines. http://resource.npl.co.uk/mtdata/phdiagrams/sisn.htm Ben -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall Sent: Tuesday, March 27, 2012 2:18 PM To: [log in to unmask] Subject: EXTERNAL: [TN] Rework Concern and Question Folks, We've ran across a strange incident and I'd like a little advice from the group. We recently underwent a component vendor change, and part of the first group of boards were misbuilt due to incorrect polarity (the part marking was misinterpreted by the vision operator). Anyway, an attempt to remove the part by our Repair group resulted in lifted pads on 10 of the first 12 boards. We've analyzed the lead material beneath the SEM and it returns 98% tin and 2% silicone. The old style component comes off quite easily (within 3 seconds), and an analysis of its leads shows to be 100% tin. It's a 6 pin diode with very little mass. What's going on here? Does a 2% silicone mix raise the melting point of solder by 200 degrees C? Please help me understand. Thanks, Leland ________________________________ ?Confidentiality Notice: This transmission (including any attachments) may contain confidential information belonging to the sender and is intended only for the use of the party or entity to which it is addressed. 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