> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Dennis Saputelli > Sent: 21 February 2005 16:48 > To: Protel EDA Discussion List > Subject: Re: [PEDA] how close 0603 > > very instructive john > thanks > i never really thought about tol of size of part
Dennis If you want I can pull some areas of boards we have done and you can lift the sizes yourself. > so what are you saying here Pb-free pads are bigger? Depends on process, materials used, plating, paste it will effect pad geometries and also sizes (paste volume) and one compromise is actually paste reductions. Mostly to avoid insufficient paste volumes, overheating joints/stress causing fractures during cooling and so on so the oven capabilities to adhere to strict profile is also important. Most 5 zone ovens even with cooling plants in the last zone won't cut it. I have a spare 5 Zone convection oven for sale if anyone is interested..... > if so Pb-free really does impact pcb design Yes it does, but it can be quite process / capability specific, I have seen work we have done here which works fine, falling down on higher capacity lines as they changed the paste so it can be printed faster (less viscosity), some issues are true for what we use now with Pb but because of the higher temps involved it is more process intensive. We avoid bismuth where we can. On a whole one of our biggest issues have been with SMT E-Caps which are quite fragile at the best of times, but mounted on a board with a large BGAs in PB Free we have seen increased failures so we are removing them from products at the moment as suppliers have obviously not got their act together yet. Motorola had some nice info at one time so I guess that Freescale's site would be worth a visit. All Best John > > Dennis Saputelli > > ______________________________________________________________ > _________ > Integrated Controls, Inc. Tel: 415-647-0480 EXT 107 > 2851 21st Street Fax: 415-647-3003 > San Francisco, CA 94110 www.integratedcontrolsinc.com > > > John A. Ross [Design] wrote: > > Dennis > > > > On 0603 here, plucked randomly from a production board, Pad size > > (standard pb) is 1 x 1 mm with pads 1.7mm apart. Component > pitch 1.6mm > > (gives gap of 0.6 mm aprox). Our Pb free size is different although > > this still works its not optimal. > > > > These run through our process here of paste (using MPM3030 > printers) > > and Philips (Assembleon/Yamaha) placement machines and Soltec oven > > just fine, including double sided reflow. > > > > The same boards are also made elsewhere using a mixture of > Dek printer > > / Universal chip shooters/Panasonic placement/Soltec reflow ovens. > > > > What you will get away with regarding component pitch and densities > > will depend also on the reflow process as your paste > definitions are > > closely linked to the reflow capabilities of the CEM. If you go pb > > free you will have a lot less reduction on pad size so the printer > > tolerances (or slowed down for repatability) so will need > to be looked > > at, as you want to retain good gasketing to the pad even at > high speed > > using very wet pastes so it does not weep in between the SM > pads you > > could end up with some paste deposit in the trench which > will solder > > ball who knows where.... > > > > I would expect some comments from your CEM with a 40 mil > (1mm approx) > > pitch as this only leaves a gap of 0.2 mm between pads of > 0.8 x 0.8 mm > > which will end up with no solder mask between them, since most 0603 > > (1608) parts have width of 0.8 mm +/- 0.15mm or so, if the > max parts > > tolerances for physical size are seen in reality (0.15mm) > on 2 parts > > side by side then this exceeds the available space between parts so > > they will touch. So placement accuracy does not even come > into it as > > the physical dimensions of the parts leave no tolerance at > all. 0603 > > resistor sizes and tolerances based on Rohm MCR03/Samsung > RC1608, Cap > > sizes from Murata GRM18/Samsung CL10 series. > > > > Hope you find some of this useful, hopefully I did not make > an error > > jumping between mils/mm :-) > > > > John > > > > > > > > > >>-----Original Message----- > >>From: Dennis Saputelli [mailto:[EMAIL PROTECTED] > >>Sent: 20 February 2005 18:43 > >>To: Protel EDA Discussion List > >>Subject: Re: [PEDA] how close 0603 > >> > >> > >>how close do y'all pack 0603's side by side ? > >> > >>Dennis Saputelli > >> > >>______________________________________________________________ > >>_________ > >>Integrated Controls, Inc. Tel: 415-647-0480 EXT 107 > >>2851 21st Street Fax: 415-647-3003 > >>San Francisco, CA 94110 www.integratedcontrolsinc.com > >> > >> > >> > >> > >>____________________________________________________________ > >>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] > > > > > > > > > > ____________________________________________________________ > 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]
