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

Belisko Marek marek.belisko at gmail.com
Tue Feb 28 08:33:11 CET 2017

Hi Nikolaus,

On Mon, Feb 27, 2017 at 7:30 PM, H. Nikolaus Schaller <hns at goldelico.com> wrote:
> 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.
This is great news. But AFAIK desoldering/soldering BGA is not really
easy process and sometimes happens that chip is damaged.
Do you have some special idea how to do that? Thanks for sharing.
> BR,
> Nikolaus
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Marek Belisko - OPEN-NANDRA
Freelance Developer

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Tel: +421 915 052 184
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