David,
10 years ago, then you must be full learned now. Something on surface you
say. Taking down a Hornet on a slippery carrier must be a nightmare, but
fortunately they have things for cleaning, and that's maybe what we need
then, solder pad cleaning? You touch something, David, we made a TOFSIMS on
the board pads and found so many strange things (I have told TN before)that
we had to judge the method as too 'scientific', as one guy said you'll find
all kind of stuff in ENIG pads, that's normal. So, the result from that
examination was put under all other reports because of not understanding.
Maybe it's time to have a look again. Now, David, there are two
possibilities: bad wetting or dewetting. I have sent some high mag SEM
images to a couple of persons that were interested in the matter, but noone
of these have responded yet. Maybe you didn't track down the very cause ten
years ago, I don't want to bother you too much but do you have more to say
I'm ready too listen.
The BGA maker is probably not the bad dog here, but they are involved and
seem to be very interested in giving us a hand. Their worldwide experience
must resulted in tons of experience.
Thanks again, David
Gaby whispered interesting things in my ear too
Ingemar
-----Original Message-----
From: David Douthit [mailto:[log in to unmask]]
Sent: den 25 januari 2001 02:53
To: TechNet E-Mail Forum.; Ingemar Hernefjord (EMW)
Subject: Re: [TN] Increased Phosphorus in Electroless Ni
Ingemar,
About 10 years ado I saw the same patterm whem doing desructive analysis of
some gold plated TH pins (square). No phasing of the solder over 90% of the
surface. The phased parts where randomly spotty (no edge exposure to base
metal). The powers that be declared the situation was the same as a "press
fit" pin and the circuit would last past warrenty! Go figure!
As near as I could guess some sort of contamination prevented the complete
phasing of the solder. How long this sort of joint will last on SM is
anybodies guess.
D. A. Douthit
"Ingemar Hernefjord (EMW)" wrote:
> Thanks Hans Shin and ya'll hou'wanna help (to use Steve's language),
> I'm concentrating on reducing my list on 25 matters that can cause BGA
lift trouble.
>
> Did this: provoked a soldered 560BGA by installing a separating force in
one end and gradually increase the force until getting a rupture. At first
nothing happened but suddenly there was 'frrritch' and whole row began to
get apart. But several hundreds left with GRADUAL impact, last in row didn't
get any force at all. This way I had the possibility to study exactly how
the rupture occurs. Now a surprise. The classical elongated rupture
structure occurred only on the periphery of the board's solder pad, and on
some, just small strikes here and there. The rest (90%) of the solder pads
were just shiny Nickel. That RING of genuin solder is so strong that you
could hang a 200 pound Texas guy (visit at Mac Donald included) in the
560BGA package without rupture! I can now omit bad joints caused by a
bleeding solder mask, instead the best adhesion was all around the solder
mask interface. I will be another person after this, sigh. Double sigh.
>
> My intricate question: when you guys have real strong BGA solder joints,
do you know how they look like on inside? Do you have 100% adhesion all over
the solder pad? Do you at all have a requirement in your spec on this? Don't
you just rely on tempchange, ageing and other verification. Perhaps you
don't even need verifying.
>
> Thanks again for all support, will let you know the end...if there is such
a one.
>
> Ingemar
>
> -----Original Message-----
> From: Hans Shin [mailto:[log in to unmask]]
> Sent: den 23 januari 2001 17:20
> To: [log in to unmask]
> Subject: Re: [TN] Increased Phosphorus in Electroless Ni
>
> I thought Mark was referring to Mike Walsh's article in Circuitree
(January 2001). In either case, Mike Walsh is not "discounting the previous
work or theories," but "offer here a new and novel description of the black
pad problem and its possible elimination." And, they strongly believe that
their "work shows that the problem of black pad and many of the other
plagues of ENIG are traceable to the nickel bath."
>
> Ingemar, I think any of those instruments would be fine, although I don't
expect that layer to be organic, so you may want to exclude FTIR. XPS will
probably help, because it also gives you the binding energies of the
elements detected.
>
> Hans Shin
> Pacific Testing Laboratories, Inc.
> http://www.pacifictesting.com/
>
> -----Original Message-----
> From: Ingemar Hernefjord (EMW) [SMTP:[log in to unmask]]
> Sent: Tuesday, January 23, 2001 3:51 AM
> To: [log in to unmask]
> Subject: Re: [TN] Increased Phosphorus in Electroless Ni
>
> Guys, I begin to feel schizo,
> one says this and another that, and me being slow thinker, not easy. Mark
you said this: "The cause of the black pad phenomenon has been found and
fixed,
> and it has nothing to do with phosphorous!" And you refer to CircuiTree's
article by George M. But he pointed that phosphorous was one of mayor
concerns, didn't he?: " Major factor Effects on black pad formation are The
Structure of Nickel deposit, The Phosphorous Content of the Nickel deposit,
The Uniformity of the Nickel and Gold Coatings and finally The Corrosion
Rate of the Immersion Gold."
>
> Another one, not Mark, but all of you: Lucent's people have led us back to
the central issue, the dark, thin, brittle and elusive shadow, I mean the
extremly thin layer between ordinary Ni3Sn4 and the Nickel on the lands. I
have asked a lot of people about their experience of compund findings, but
no respons yet. What tool do you recommend for examination the layer? EDS?
FTIR? XPS? SIMS? or what? Cross sectioning with polishing seems to smear and
mislead. Suppose that the BGA falls of,
>
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