[SI-LIST] Re: Fixing a black pad
- From: Zilber Gil <gzilber@xxxxxxxxxx>
- To: Sol Tatlow <Sol.Tatlow@xxxxxxxxxxxxxxx>, si-list <si-list@xxxxxxxxxxxxx>
- Date: Wed, 29 Jun 2005 16:20:09 +0200
Hello Sol,=0D=0AThank you for your detailed reply=2E Is it possib=
le that not enough heating during the reflow caused, in some exte=
nt, too cold soldering and due to that bad wetting of the Ni fol=
lowed by oxidation of the Ni pad=2E The phenomena may look the sa=
me after removing the components, black unwetted pad, but in this=
case the reason is the assembly house and not the PCB manufactur=
ing=2E =0D=0A=0D=0AThanks,=0D=0AGil Zilber=0D=0AElta system Ltd=2E=
=0D=0ATel=2E +972-8-8577240=0D=0AMobile +972-54-4983222=0D=0Ahttp=
://www=2Eiai=2Eco=2Eil/site/en/iai=2Easp?pi=3D17887=0D=0A =0D=0A=0D=
=0A=0D=0A-----Original Message-----=0D=0AFrom: Sol Tatlow [mailto=
:Sol=2ETatlow@prodesigncad=2Ede] =0D=0ASent: Wednesday, June 29,=20=
2005 11:38 AM=0D=0ATo: Zilber Gil; billw@aec-lab=2Ecom; si-list=0D=
=0ASubject: Re: Fixing a black pad=0D=0A=0D=0AHi Gil,=0D=0A=0D=0A=
The 'Black Pad' phenomonen is well known in the industry - the ro=
ot of the problem is generally the nickel plating applied during=20=
the ENIG (electroless nickel immersion gold) plating process, whe=
re a corroded nickel layer leads to weak solder joints after asse=
mbly=2E=0D=0AThis phenomonen therefore only affects boards with E=
NIG plating, and although reflow temperature/profiles may exacerb=
ate the problem, they are not the real cause=2E=0D=0A=0D=0AThe wo=
rst part is, you cannot detect it optically before assembly - it=20=
only becomes apparent when the joints fail, as you found out=2E=0D=
=0AAnd, if you have this problem with one board, you will most li=
kely have more boards coming back to you with the same problem, s=
ince it is related to the plating bath (which was no doubt used t=
o produce a whole batch of your boards)=2E=0D=0A=0D=0AAFTER failu=
re, there is not too much you can do about it - with an aggressiv=
e flux you may succeed in soldering the component back onto the b=
oard, but since the problem is with the nickel plating (which, du=
e 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)=2E PLUS, even=20=
if only one BGA on the board has failed, if there are others, the=
y are also likely to fail at some point=2E The safest solution, i=
f also the most expensive (short term!), is to replace the board=2E=
=0D=0A=0D=0AFor the future, since finding a PCB manufacturer who=20=
can produce a reliable ENIG finish is easier said than done (not=20=
because they don't exist, rather, because you only know if they w=
eren't reliable when they prove it!!), for the future you may wan=
t to consider immersion tin or silver=2E These have other disadva=
ntages (there is no perfect surface finish), but they tend to giv=
e overall better results=2E=0D=0AThe best thing to do is do some=20=
Googling/reading about the subject, and decide on the basis of yo=
ur specific needs=2E=0D=0A____________________________________=0D=
=0ASol Tatlow, M=2EEng=2E (Oxon)=0D=0AProDesign Electronic & CAD=20=
Layout GmbH=0D=0AProduct Developer=0D=0AAlbert-Mayer-Str=2E 16=0D=
=0AD-83052 Bruckmuehl=0D=0APhone: +49 (0) 8062-808-302=0D=0AFax:=20=
+49 (0) 8062-808-333=0D=0AMailto:sol=2Etatlow@prodesign-europe=2E=
com=0D=0Awww=2Eprodesign-europe=2Ecom=0D=0A______________________=
______________ =0D=0A=0D=0A=0D=0A=0D=0A-----Urspr=FCngliche Nachr=
icht-----=0D=0AVon: si-list-bounce@freelists=2Eorg [mailto:si-lis=
t-bounce@freelists=2Eorg] Im Auftrag von Zilber Gil=0D=0AGesendet=
: Dienstag, 28=2E Juni 2005 16:33=0D=0AAn: billw@aec-lab=2Ecom; s=
i-list=0D=0ABetreff: [SI-LIST] Re: Fixing a black pad=0D=0A=0D=0A=
=0D=0AHello Bill,=0D=0AThanks for the response=2E The pad finishi=
ng was ENIG and the BGA have SnPb solder balls=2E I saw the Black=
pad only after removing the BGA components that was mounted more=
then a year ago (due to disconnections)=2E Is it possible that i=
t is not a real black pad but too low reflow temp in this compone=
nts (partially could soldering) causing to oxidation of the Ni?=0D=
=0A=0D=0AThanks,=0D=0AGil =0D=0A=0D=0A-----Original Message-----=0D=
=0AFrom: si-list-bounce@freelists=2Eorg [mailto:si-list-bounce@fr=
eelists=2Eorg]=0D=0AOn Behalf Of Bill Wurst=0D=0ASent: Tuesday, J=
une 28, 2005 2:46 PM=0D=0ATo: si-list=0D=0ASubject: [SI-LIST] Re:=
Fixing a black pad=0D=0A=0D=0AGil,=0D=0A=0D=0AI'm wondering if t=
he black pad is silver (Ag) oxide=2E Have you recently switched=20=
to lead (Pb) free processing? Or worse, has your BGA vendor begu=
n to supply you with lead free parts without your knowledge? =0D=0A=
Unfortunately, I'm not very knowledgeable when it comes to silver=
solder processes, but would like to hear from anyone else with m=
ore knowledge than I in this area=2E We may all need to learn ab=
out this quickly as the electronics industry makes the lead-free=20=
transition=2E=0D=0A=0D=0A -Bill=0D=0A=0D=0A=0D=0A /****=
********************************=0D=0A / billw@aec-l=
ab=2Ecom /=0D=0A / =20=
/=0D=0A / Advanced Electronic Concepts, LLC /=0D=0A / =20=
www=2Eaec-lab=2Ecom /=0D=0A ***********************=
*************=0D=0A=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=0D=0AZi=
lber Gil wrote:=0D=0A> Hello all,=0D=0A> After removing a BGA com=
ponents a black pads was seen on some of the =0D=0A> pads=2E Is i=
t possible to fix it? If trying to use activated flux it is =0D=0A=
> possible to coat the pad with solder (receive back the wetting)=
=2E Does =0D=0A> the black pad phenomenon will appear again on th=
is pad (will I =0D=0A> encounter it later on other pads?)?=0D=0A>=
=0D=0A> =0D=0A> =0D=0A> Thanks,=0D=0A> =0D=0A> Gil Zilber=0D=0A=
> =0D=0A> Elta systems=0D=0A=0D=0A=0D=0A=0D=0AThis message is pro=
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see thereof=2E If you are not the intended addressee, please be a=
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