Great! Wonderful! So with RoHS (Risk of Halting Soldering) you can at least solder once. What a hit! Inge ----- Original Message ----- From: "R Sedlak" <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, July 04, 2008 5:27 PM Subject: Re: [TN] Immersion Tin Problem > All of this makes perfect sense if you consider the mechanisms. > > ImSn has a shelf life, which is controlled by the spontaneous formation of > the Tin/Copper intermetallic, which begins to form as the Tin is plated at > the interface. When the Tin has totally converted to the Tin/Copper > intermetallic, it can no longer be soldered. > > Heat accelerates the formation of the intermetallic. > > Your first pass is accelerating the formation of the intermetallic > dramatically. You are likely simply converting the whole of the ImSn to > intermetallic, and it is game over. > > Rudy Sedlak > RD Chemical Company > > > --- On Fri, 7/4/08, Rex Waygood <[log in to unmask]> wrote: > >> From: Rex Waygood <[log in to unmask]> >> Subject: [TN] Immersion Tin Problem >> To: [log in to unmask] >> Date: Friday, July 4, 2008, 2:35 AM >> We do not usually use Immersion Tin finish boards but we >> have some with >> a problem. >> The boards are about 10-12 weeks old, stored in original >> packing, double >> sided PTH and lead free processed. >> Side 1 processed OK >> Side 2 had some non-wet problems (Profiles and dwells etc >> are industry >> 'norm') >> Hand soldering has proved to be nigh on impossible. >> The immersion tin is within the thickness specified >> (typical values 1.1 >> to 1.2 micron) >> >> Should we have avoided ImSn (as we have done previously)? >> >> Is the spec for the ImSn OK? >> >> Has the PCB mfr done something wrong? >> >> Have we? (apart from accepting ImSn) >> >> Rex >> >> >> Rex Waygood >> Technical Manager >> >> PartnerTech Poole Ltd >> Benson Road >> Poole >> Dorset BH17 0RY >> United Kingdom >> >> Tel: +44 (0)1202 674333 >> Fax: +44 (0)1202 678028 >> DDI: +44 (0)1202 338222 >> Mob: +44 (0)7887 997403 >> >> [log in to unmask] >> www.PartnerTech.co.uk >> >> >> ------------------------------------------------------------------------------- >> The information contained within this e-mail and any >> attachments contained therein may be confidential and/or >> legally privileged and is for the use of the intended >> recipient only. If you are not the intended recipient >> please delete it from your system and notify the sender by >> return e-mail. The content of this e-mail may not be copied >> or disclosed to any third parties without prior permission >> from the sender. >> >> E-mail is susceptible to data corruption, interception, >> tampering and viruses. 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