On Sun, Aug 21, 2011 at 8:46 PM, Anna <ascho...@gmail.com> wrote: > On Sun, Aug 21, 2011 at 10:18 PM, Richard A. Smith <rich...@laptop.org> > wrote: >> >> Interesting. If you did in fact reflow anything then it was probably due >> to the poor temp regulation of your toaster oven. The solder in the XO is >> lead free and melts a higher melting point than 385. I don't know the exact >> formulation that Quanta uses but most lead free formulations melt at > 215C >> which is 419F. > > Thank you for being the first person to offer actual data on this. Since I > baked it at 385, or thought I did, if in fact the melting point is 419, then > I didn't reflow the solder at all. I need to get an independent oven > thermometer to stick in there if this turns into an habitual endeavor. > >> >> If you actually didn't reflow anything then the forces from the large >> thermal gradient may have been sufficient to push the cracks back together >> enough to work again. (Sort of the same thing that happens when you test by >> pressing on the chip hard to see if it boots) >> >> A production line oven uses a soldering profile. Pre-heat, then a brief >> spike over the melting point and then a cool down. >> >> If you do a search for lead free soldering profile you will see loads of >> information on various profiles. Picking something that closely matches one >> of those profiles will give you the greatest chance of success. > > Good to know. Since this isn't like tempering steel, if something goes > wonky in the future, I can examine what production lines do and try to > emulate that as best I can. The wikipedia entry on reflow ovens wasn't very > detailed, but I didn't know what else to search for so I just hauled off and > did the best I could. I got most of my info from a message board where > folks put their HP laptop mobos in the oven. > >> >> As James mentioned if you forget and bake the RTC battery then there is a >> very high probability it will explode. At my previous job we once used old >> computer motherboards with thermocouples attached to tune our profile and we >> forgot to take out the RTC battery. It exploded but thankfully it was while >> it was inside the oven and no one was injured. > > Oh, yeah, I made sure to remove the battery. And anything else that might > explode, catch fire, melt, or otherwise make a wicked mess. > > A couple of hours ago, I baked the second XO 1.5 motherboard and yep, it > booted after that. I took tons of pictures this time. I'll post a writeup > with the pictures in the next few days. At this point I feel like Julia > Child. If Julia Child put circuit boards in her oven. > > And no, this is definitely not for the "typical" user, but hey, on Friday I > had two dead XO 1.5's and now on Sunday evening I've got two working units. > No idea on the longevity of this fix, but OLPC is all about experimentation, > right?
Many +1 on a job well done. Indeed this project is about experimentation what an incredible group of crazies we have here! There are no boundaries to learning. Keep plugging away! I will now go and drink in your honor :-) Oh, and be sure to come attend OLPC SF Community Summit 2011 in October so we can buy you a few rounds!!! cheers, Sameer > > Anna Schoolfield > Birmingham > > _______________________________________________ > Devel mailing list > Devel@lists.laptop.org > http://lists.laptop.org/listinfo/devel > > _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
