BGA Probleme (wurde gebeten das hier einzustellen)

03/07/2012 - 17:49 von Joerg | Report spam
Hallo Leute,

Die Entwickler dieses OpenSource Projekts haengen mit BGA
Bestueckungsproblemen fest:

http://projects.goldelico.com/p/gta04-main/

Einer von ihnen (Walter) bat mich das unten beschriebene Problem mal
hier zur Diskussion zu stellen, hat selbst keinen Zugang zur NG. Sehen
ob jemand Ideen hat oder vielleicht gar einen guten Bestuecker bei Euch
weiss der sowas hinkriegt. Ich kenne nur Bestuecker in den USA und
Asien. Wer per PM antworten moechte:

hns <at> goldelico.com (Dr. Nikolaus Schaller)

Ich bin kein BGA Experte (mag die Dinger ueberhaupt nicht) und konnte
nur einen Vorschlag machen der hier mal bei aehnlichen Probleme geholfen
hat. Habe ich ganz am Ende drangehaengt.


Hier der Text, ist was lang, Zitat:

Hi all,
I did a long telephone call this morning to discuss the production
situation of
the GTA04A4 boards.

Am 25.06.2012 um 20:56 schrieb Dr. H. Nikolaus Schaller:


Hi,

Am 25.06.2012 um 16:16 schrieb Gilles Filippini:


Hi Nikolaus,

Dr. H. Nikolaus Schaller a écrit , Le 31/05/2012 17:36:

So please expect that it will become End of June for delivery...



Since we are near to End of June, time for asking how is it going? ;)



Neither good nor bad...

This means:
* we have already shipped some of the GTA04 Group Tour boards
* some friends have upgraded to a complete OpenPhoenux (we have a


handful reworked GTA02)

* but we still have a list of open orders for roughly 90 GTA04 Group


Tour boards


The production company had stopped again to do some more
analyses and the last status I received today is that they had
again made some X-Ray. Now they think they can again optimize
the soldering process a little so that we don't get so much broken
boards that need manual rework.



So here is a copy of the latest X-Ray image of the DM3730CBP with short
circuits:
http://download.goldelico.com/gta04...cht-01.jpg

If you want to compare to the GTA04A3 board X-Ray (with one short):
http://download.goldelico.com/gta04...-xr002.jpg

or the GTA04A2 board (where only 1 unit exists):
http://download.goldelico.com/gta04...erview.jpg


Every rework ruins some components (unfortunately 1 DM3730
+ 1 Memory chip > 50 EUR) and costs intensive working time.
And we simply can't afford that if it happens too often...

So the highest priority is to get rid of the root cause for these
soldering failures.



After analyzing and discussing the X-Ray images we now think we
understand what happens (but you never know if you are right...).

The reason appears that the DM3730CBP gets some warp during
the soldering process squeezing the balls in the middle of the BGA
grid so that they may touch a neighbor and make a short circuit.
And on the corners the balls lift off and this may result in interruptions.

This theory correlates exactly with the error patterns we see:

* some 50% of the boards come out of the soldering process with
shorts on VDD1, VDD2 and/or VIO which are mostly available
on the center balls

* if the chip has no short on the power supply or is reworked some
50% of the boards have interruptions which makes a single function
fail. Sometimes the SD interface has just 3 data lines, sometimes the
WLAN chip. Sometimes some sensor is not working. Sometimes
the USB is not working, or one display data link distorting the
colors etc.

Now comes the crucial question: how can this be improved?

The specialists of the production company have spent whole weekends
to do more experiments but did not yet find the right trick. It is not that
they do not want to solve the problem (they see it as a challenge) they
simply have not yet found the key.

One factor is that our GTA04 board has exceptionally squeezed
components (since we must be small) so the soldering of a OpenPandora
or the BeagleBoard may be a little easier from heat distribution.

I.e. we are pushing an experienced EMS to their limits...
An EMS who has produced more than 2000 different products in small
quantities (which is their strength) including some 0.4mm BGAs.

A new experiment is scheduled for week 29 to use a different
reflow soldering machine and process which uses a little lower
temperature.

Unfortunately, we can't contribute to this production improvement
to speed things up.

Unless one of the readers on these list knows some real specialist
for such PoP soldering of BGAs who is willing and capable to
consult (even if it costs money). So if you know someone, please
let me know.



The good answer is that as soon as we decide to continue,



So we had to decide to wait for the different reflow soldering process
first.


it takes less than 4 weeks to produce, test and ship all missing
boards. They have planned that it works even if holiday season
is coming. And our shipment plan is by sequence of order. So
if you did order early, it is even a little closer.



So it is a stony path towards a community driven independently
developed and produced open smartphone platform. But Rome
wasn't built in one day...

And we have to solve this issue before we can start to think
about a future quad core LTE device with multitouch... Please
keep the faith.

BR,
Nikolaus

Zitat Ende


... Mein Vorschlag war:

Das ganze sieht danach aus dass der Bestuecker mit BGA plus Feinleiter
ein wenig ueberfordert ist. Das Temperaturprofil hinzubekommen ist nicht
einfach. Auf dem ersten Bild sieht es so aus dass Kurzschluesse auch am
Rand vorkommen. Ist total unueblich, aber mal so als Idee:

Wenn Ihr den Verdacht auf Woelbung habt und es weder ueber besseres
Platinenmaterial noch besseres Temperaturprofil hinzubekommen ist, kann
man vor dem Bestuecken in der Mitte und vielleicht noch an den vier
Innenecken duenne Plastikunterlegscheiben aufkleben? Scheiben und Kleber
muessten natuerlich mindestens ebensoviel aushalten wie FR4. Die sollten
dafuer sorgen dass Balls nicht per lokal "zerquetscht" werden koennen.
 

Lesen sie die antworten

#1 Roland Ertelt
03/07/2012 - 18:21 | Warnen spam
Und so sprach Joerg:

Hallo Leute,

Die Entwickler dieses OpenSource Projekts haengen mit BGA
Bestueckungsproblemen fest:

http://projects.goldelico.com/p/gta04-main/

Einer von ihnen (Walter) bat mich das unten beschriebene Problem mal
hier zur Diskussion zu stellen, hat selbst keinen Zugang zur NG. Sehen
ob jemand Ideen hat oder vielleicht gar einen guten Bestuecker bei Euch
weiss der sowas hinkriegt. Ich kenne nur Bestuecker in den USA und
Asien. Wer per PM antworten moechte:

hns <at> goldelico.com (Dr. Nikolaus Schaller)

Ich bin kein BGA Experte (mag die Dinger ueberhaupt nicht) und konnte
nur einen Vorschlag machen der hier mal bei aehnlichen Probleme geholfen
hat. Habe ich ganz am Ende drangehaengt.


Hier der Text, ist was lang, Zitat:

Hi all,
I did a long telephone call this morning to discuss the production
situation of
the GTA04A4 boards.

Am 25.06.2012 um 20:56 schrieb Dr. H. Nikolaus Schaller:

Hi,

Am 25.06.2012 um 16:16 schrieb Gilles Filippini:

Hi Nikolaus,

Dr. H. Nikolaus Schaller a écrit , Le 31/05/2012 17:36:
So please expect that it will become End of June for delivery...



Since we are near to End of June, time for asking how is it going? ;)



Neither good nor bad...

This means:
* we have already shipped some of the GTA04 Group Tour boards
* some friends have upgraded to a complete OpenPhoenux (we have a


handful reworked GTA02)
* but we still have a list of open orders for roughly 90 GTA04 Group


Tour boards

The production company had stopped again to do some more
analyses and the last status I received today is that they had
again made some X-Ray. Now they think they can again optimize
the soldering process a little so that we don't get so much broken
boards that need manual rework.



So here is a copy of the latest X-Ray image of the DM3730CBP with short
circuits:
http://download.goldelico.com/gta04...cht-01.jpg




Sieht aus, wie zu heiss oder zu lange gelötet. Evtl stimmt auch der
Lötstop-Lack nicht. Wurden wirklich die Footprint-Empfehlungen eingehalten?


If you want to compare to the GTA04A3 board X-Ray (with one short):
http://download.goldelico.com/gta04...-xr002.jpg




Der wurde vermutlich beim löten bewegt. (Erschütterungen)


or the GTA04A2 board (where only 1 unit exists):
http://download.goldelico.com/gta04...erview.jpg



Der auch.

(Ich weiss schon, warum mein Chef BGAs nicht mag. Man muss den Prozess
100%ig beherrschen)

Roland

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