[Tinkerphones] [Gta04-owner] GTA04A5 and News from the Kernel

H. Nikolaus Schaller hns at goldelico.com
Fri Oct 28 18:59:41 CEST 2016


Hi,

> Am 27.10.2016 um 19:43 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> Hi,
> finally we got a time slot tomorrow to do the next
> soldering tests for the GTA04A5

...

> So thats it for today. And I hope I can bring some
> news about the GTA04A5 tomorrow.

we have done the soldering test and the result is really
interesting and not exactly what I have expected.

First of all the good news: none of the 4 boards has the
short circuits in the middle area any more :)

This is good news!

But there is a "but":
now we have a new problem: all 4 boards have been produced
using different methods of preparation.

So all 4 methods appear to be better than the previous
methods done in the first attempt.

The big question is now: which factor was the most
important? And which of the 4 methods is really the
best one to build the other ca. 100 boards with lowest
risk of getting scrap again?

To immediately answer this question we should have produced
more combinations of parameter changes...

So we have learned a lot, but the outcome is not 100% indicative.

Now we have to do the best guess.

For doing this, I need to get the X-ray screen shots to look
deeper into them and what I also want to try is to find out
if there are differences in how well the solder joints are.

Not that we avoid shorts but have missing contacts. This is
something hardly visible in X-ray.

Since the production line is already producing something else
now, we have some days to finally decide.

Here are some photos from the production of the 4 boards:

Preparation of stencil:





Solder paste applied (you see that we did paste only the corners in this case):



firsts chip placed:



preparation of DM3730 with a snippet of Kapton tape:



All 4 boards (just 4 DM3730 + PoP installed - all others chips don't show problems)



As soon as I have the X-rays I can share them as well.

BR,
Nikolaus

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