Hello All, What consideration to be taken care for TIP and Ring (Telecom domain) pair routing in PCB layout , and let me know the reason also.pls send me if u have any guidelines regarding this. Advance thanks for your Help!! Regards Sug -------Original Message------- From: Sol.Tatlow@xxxxxxxxxxxxxxx Date: 06/29/05 15:12:13 To: gzilber@xxxxxxxxxx; billw@xxxxxxxxxxx; si-list Subject: [SI-LIST] Re: Fixing a black pad Hi Gil, The 'Black Pad' phenomonen is well known in the industry - the root of the problem is generally the nickel plating applied during the ENIG (electroless nickel immersion gold) plating process, where a corroded nickel layer leads to weak solder joints after assembly. This phenomonen therefore only affects boards with ENIG plating, and although reflow temperature/profiles may exacerbate the problem, they are not the real cause. The worst part is, you cannot detect it optically before assembly - it only becomes apparent when the joints fail, as you found out. And, if you have this problem with one board, you will most likely have more boards coming back to you with the same problem, since it is related to the plating bath (which was no doubt used to produce a whole batch of your boards). AFTER failure, there is not too much you can do about it - with an aggressive flux you may succeed in soldering the component back onto the board, but since the problem is with the nickel plating (which, due to corrosion, allows the copper underneath to interact with the joint), reworks are likely to suffer a similar fate (even if the reworked component SEEMS to be properly soldered). PLUS, even if only one BGA on the board has failed, if there are others, they are also likely to fail at some point. The safest solution, if also the most expensive (short term!), is to replace the board. For the future, since finding a PCB manufacturer who can produce a reliable ENIG finish is easier said than done (not because they don't exist, rather, because you only know if they weren't reliable when they prove it!!), for the future you may want to consider immersion tin or silver. These have other disadvantages (there is no perfect surface finish), but they tend to give overall better results. The best thing to do is do some Googling/reading about the subject, and decide on the basis of your specific needs. ____________________________________ Sol Tatlow, M.Eng. (Oxon) ProDesign Electronic & CAD Layout GmbH Product Developer Albert-Mayer-Str. 16 D-83052 Bruckmuehl Phone: +49 (0) 8062-808-302 Fax: +49 (0) 8062-808-333 Mailto:sol.tatlow@xxxxxxxxxxxxxxxxxxxx www.prodesign-europe.com ____________________________________=20 -----Urspr=FCngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] = Im Auftrag von Zilber Gil Gesendet: Dienstag, 28. Juni 2005 16:33 An: billw@xxxxxxxxxxx; si-list Betreff: [SI-LIST] Re: Fixing a black pad Hello Bill, Thanks for the response. The pad finishing was ENIG and the BGA have SnPb solder balls. I saw the Black pad only after removing the BGA components that was mounted more then a year ago (due to disconnections). Is it possible that it is not a real black pad but too low reflow temp in this components (partially could soldering) causing to oxidation of the Ni? Thanks, Gil=20 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Bill Wurst Sent: Tuesday, June 28, 2005 2:46 PM To: si-list Subject: [SI-LIST] Re: Fixing a black pad Gil, I'm wondering if the black pad is silver (Ag) oxide. Have you recently switched to lead (Pb) free processing? Or worse, has your BGA vendor begun to supply you with lead free parts without your knowledge?=20 Unfortunately, I'm not very knowledgeable when it comes to silver solder processes, but would like to hear from anyone else with more knowledge than I in this area. We may all need to learn about this quickly as the electronics industry makes the lead-free transition. -Bill /************************************ / billw@xxxxxxxxxxx / / / / Advanced Electronic Concepts, LLC / / www.aec-lab.com / ************************************ =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D Zilber Gil wrote: > Hello all, > After removing a BGA components a black pads was seen on some of the=20 > pads. Is it possible to fix it? If trying to use activated flux it is=20 > possible to coat the pad with solder (receive back the wetting). Does=20 > the black pad phenomenon will appear again on this pad (will I=20 > encounter it later on other pads?)? >=20 > =20 >=20 > Thanks, >=20 > Gil Zilber >=20 > Elta systems ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu