XO 1.5 Solder Reflow in Toaster Oven

[Sameer Verma]

On Sun, Aug 21, 2011 at 8:46 PM, Anna <aschoolf at gmail.com> wrote:
> On Sun, Aug 21, 2011 at 10:18 PM, Richard A. Smith <richard at 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
>
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