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

[tgrauss]

Hi,

If you are confident that all of them can be repaired, maybe we can then 
manufacture the other boards without the CPU/RAM and solder these 2 
chips with the repair procedure? This way we don't loose more components 
and limit the production problem.

Best regards

Thierry GRAUSS

On 27/02/2017 19:30, H. Nikolaus Schaller 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.
> 
> BR,
> Nikolaus
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