[Tinkerphones] [Gta04-owner] GTA04A5: good news and bad news

H. Nikolaus Schaller hns at goldelico.com
Mon Feb 27 19:30:54 CET 2017

Hi Marek,

> Am 27.02.2017 um 11:46 schrieb Belisko Marek <marek.belisko at gmail.com>:
>> -1.: Only 12 out of 36 (*) GTA04A5 boards we
>> have produced, are booting to Linux. The others either have a
>> short circuit under the OMAP (which is the general PoP soldering
>> problem we already know since the first generations of the
>> GTA04) or the OMAP shows no response or does not recognise the
>> µSD card for unknown reasons.

> Hmm this is bad. Doesn't something like that happen in first verification run? But maybe I'm wrong.
> Did you try to get some info from chip producer what could be a problem or which technology should be used to have it solder properly.

Yes, we asked TI in details some years ago when we built the GTA04A3 and A4.
From that we probably know everything what can be known about this DM3730 soldering issue...

And we though that this knowledge is enough to avoid to fall back into the same
old problems we had back then when using a new (and modern) production line.

Back then we had to experiment several months to raise yield from ca. 30% to 90%.
Then, the production batch was completed. But we had to do a lot of repairs back
then as well.

So all this means the production process of the DM3730 + PoP is very very critical
to parameters we can't repeat several years later. And therefore we had to start
optimization almost from scratch. But do not have the means to continue to reach
90% again.

> 12 from 36 is exactly third which is too high. I'm sorry to hear such bad news.

I am currently making a plan in which sequence we try to repair what (desolder chips
and replace). So I am confident that we can come a little closer to 36 of 36.


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