[SI-LIST] Tip and Ring routing consideration

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

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