Hi Marek, > Am 28.02.2017 um 08:33 schrieb Belisko Marek <[email protected]>: > > Hi Nikolaus, > > On Mon, Feb 27, 2017 at 7:30 PM, H. Nikolaus Schaller <[email protected]> > wrote: >> Hi Marek, >> >>> Am 27.02.2017 um 11:46 schrieb Belisko Marek <[email protected]>: >>> >>> >>>> -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
Desoldering is the easier part. > and sometimes happens that chip is damaged. Yes, that will happen and we must try a second and third time. At some point the unsoldering/resoldering stress will have damaged something else. > Do you have some special idea how to do that? Thanks for sharing. No special idea except trying... If we can finally repair 50% of the damaged ones, we are good. BR, Nikolaus _______________________________________________ Community mailing list [email protected] http://lists.goldelico.com/mailman/listinfo.cgi/community http://www.tinkerphones.org
