> > > > > -----Original Message----- > > > From: moonman [SMTP:[log in to unmask]] > > > Sent: Tuesday, January 13, 2004 2:29 PM > > > To: Dehoyos, Ramon > > > Subject: Re: [TN] reflowing 0402 SMT capacitors with underside > > termination s > > > > > > Hey Ramon, > > > > > > How you doing? > > > > > > The phased reflow profiles can do a lot for this condition. You simply > > > determine the ones that will work with your solder pastes and your other > > > soldering requirements. > > > > > > I never have liked to use an non-eutectic solder of any type but in > these > > > cases, as Steve said, a 2% silver formulation can be beneficial for the > > same > > > basic reasons as phased reflow. Simply, the small chip devices have a > > > buoyancy that prevents proper wetting so they "float" in all directions > > > starting with up as there are no end terminations to be "grabbed" and > > held, > > > via wetting, during the soldering process. > > > > > > Using phases or "phased" solder pastes provides time for the devices to > > > "adhere" to the solder without "roaming" all over. The Ag2 goes through > > > phases pure eutectic pastes do not. They go through a minor plastic > phase > > > whereas eutectics go from solid to liquid without the plastic phase. > > > > > > I have had problems coming up with "good," well balanced profiles, using > > > phased reflow soldering, that satisfy my requirements for what I would > > call > > > good wetting for all components of varying thermal densities or of > varying > > > solder termination differences. Something personal I guess or maybe I > just > > > didn't take enough time. As a team we managed to get the job done but it > > was > > > a trial. > > > > > > Another thing to be considered is the solder paste volume that needs to > > > minimal but enough to effect acceptable solder joints. However, with > these > > > things - what is acceptable? The question must be asked for obvious > > reasons. > > > The other major point to be considered is the solder termination > geometry > > > and size. Again, I and many others use minimal pad sizes for most chip > > > devices with very small solder joints. Another consideration would be > > using > > > the "home plate" design for many small chip devices though I've not yet > > > tried them for the devices in question. > > > > > > Lots' to be considered not the least of which, again, is what is an > > > acceptable solder joint and how do you determine it. I've read little > > about > > > initial quality or long term reliability investigations. Have you? > > > > > > Personally, I think these little devices should be outlawed > > > > > > Keep me posted and take care, > > > > > > MoonMan > > > > > > ----- Original Message ----- > > > From: "Dehoyos, Ramon" <[log in to unmask]> > > > To: "moonman" <[log in to unmask]> > > > Sent: Tuesday, January 13, 2004 11:27 AM > > > Subject: FW: [TN] reflowing 0402 SMT capacitors with underside > termination > > s > > > > > > > > > > > > > > > Some of the big guns are away and have not > > been > > > > > heard from.What do you think about this 0402 chip problem Moonman? > > > > > Regards, > > > > > Ramon > > > > > > > > > > > -----Original Message----- > > > > > > From: Steve Gregory [SMTP:[log in to unmask]] > > > > > > Sent: Monday, January 12, 2004 3:23 PM > > > > > > To: [log in to unmask] > > > > > > Subject: Re: [TN] reflowing 0402 SMT capacitors with > underside > > > > > terminations > > > > > > > > > > > > Hi Tom! > > > > > > > > > > > > There's a few articles out there that talk about "Phased Reflow > > > > > Soldering". > > > > > > Here's a link to one: > > > > > > > > > > > > > > > http://www.reed-electronics.com/semiconductor/index.asp?layout=article& > > > > > > articleid=CA274087&industryid=3026 > > > > > > > > > > > > Something I've done in the past that works really well in my > > opinion, > > > is > > > > > to> > > > > > > use a 2% > > > > > > silver solder paste. Sn62/Pb36/Ag2...works in the same way that > > Phased > > > > > Reflow > > > > > > does. > > > > > > The difference is pretty dramatic when it comes to eliminating > > > > tombstones! > > > > > > > > > > > > -Steve Gregory- > > > > > > > > > > > > > > > > > > > Greetings All, > > > > > > > > > > > > > > I am having my first experience working with an assembly design > > that> > > > > > > > involves 0402 capacitors with underside solderable terminations > > > (vice > > > > > > > wrap-around end terminations)... The reflow process seems to > cause > > > the > > > > > > > components to tilt and skew to highly unacceptable levels. > > > Physically > > > > it > > > > > > > looks as if the caps floated to the top of the molten solder > > volume > > > > (as > > > > > if > > > > > > > on pontoons) then slid down one way or the other. The vendor > made > > a > > > > few > > > > > > > recommendations including migration to a thinner (4 mil) stencil > > as > > > > well > > > > > as > > > > > > > some pad design and nitrogen tweaks and... Even after > implementing > > > > these > > > > > > > recommendations we are experiencing the same problems, just to a > > > > > slightly > > > > > > > lesser (although still unacceptable) degree... Does anyone out > > there > > > > > have > > > > > > > any additional thoughts on how to remedy this sort of issue? > > > > > > > > > > > > > > We do build another part [successfully] with a similar style > > > > component, > > > > > but > > > > > > > it is a 1206 form factor and is perhaps massive enough to keep > > from > > > > > floating > > > > > > > up the way the 0402 caps do... > > > > > > > > > > > > > > Your collective wisdom is greatly appreciated! > > > > > > > > > > > > > > Best Regards, > > > > > > > > > > > > > > Tom Ochenas > > > > > > > Process Engineering > > > > > > > Maxtek Components Corporation > > > > > > > 2905 SW Hocken Avenue > > > > > > > Beaverton, OR 97005 > > > > > > > [log in to unmask] > > > > > > > desk: 503-627-3078 > > > > > > > fax: 503-627-4651 > > > > > > > > > > > > > > > > > > > > > > > > > --------------------------------------------------- > > > > > > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > > > > > > 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 > > > > > 847-509-9700 ext.5315 > > > > > > ----------------------------------------------------- > > > > > > > > > > --------------------------------------------------- > > > > > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > > > > > 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 > > > > 847-509-9700 ext.5315 > > > > > ----------------------------------------------------->> --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 847-509-9700 ext.5315 -----------------------------------------------------