Rene Good point, SMD electrolytic in particular, in some case Tantalums also, cannot withstand the more aggressive lead free profile needed by some dense boards or they are at least too close to their datasheet limits for comfort.
John > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Rene Tschaggelar > Sent: Monday, December 06, 2004 9:06 PM > To: Protel EDA Discussion List > Subject: Re: [PEDA] Lead free re design > > Dennis, > as European, I don't have the option to stay out of the lead > free, thus I had to get some information in the last few months. > While my pcb assembler acknowledges that he doesn't have the > proper process parameters, he said the problems are multiple. > The lifetime is reduced, because the tinn eats the copper, > meaning after about 7 years there might be a gap between the > copper trace and the tinned part. > The lead till now supressed this effect. Silver would solve > it at increased cost, beside that silver can grow whiskers of > several mm in length, thus shorting a 0603. > If the silver-tin was heated above 230 degrees that would not happen. > The increased melting point of the new tin alloys is between > 217 and 220 degrees, whereas the lead-tin was at 188 degrees. > This can give problems with subunits such as DC/DC converters > or overized oscillators. These shouldn't fall apart when > being subject to the normal soldering process. Meaning they > internally have to be soldered with something higher melting. > With the new 220 degree tin alloy this margin became smaller. > > There are multiple exceptions to follow the lead free. > The automobile industry is amongst them. > Ok, I could classify my products as automobile classified, > and earn less/more. But what is my customer going to do ? > > That some call this new requirement a chessplay to shorten > the lifecycle and thus increase the turnover is as little > helping as that some claim it was invented to keep the asian > competition out. Japan started this process 15 years ago and > introduced it throughout, apparently having solved the problems. > To me it is a task on the list. > > Rene > > Dennis Saputelli wrote: > > > > > i may have posted this before but don't recall an answer > > > > someone has asked me if there are *design* issues re pc bd > designs and > > the movement to lead-free > > > > i said i didn't think so, but then i wondered about the elevated > > temperatures and surface finsishes > > > > what is the proper call out for surface finish of a pcb for > lead free ? > > and are there any actual design issues (as opposed to > call-out issues) > > > > and also > > can you use the new lead free components in a standard 'lead-full' > > process ? (thanks for 'lead-full' Ivan) > > > > and what about cleaning under CSPs and BGAs ? > > is the standard water based OA fluz a problem ? > > seems like it would be > > > > ____________________________________________________________ > You are subscribed to the PEDA discussion forum > > To Post messages: > mailto:[EMAIL PROTECTED] > > Unsubscribe and Other Options: > http://techservinc.com/mailman/listinfo/peda_techservinc.com > > Browse or Search Old Archives (2001-2004): > http://www.mail-archive.com/[email protected] > > Browse or Search Current Archives (2004-Current): > http://www.mail-archive.com/[email protected] > > ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[EMAIL PROTECTED] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
