Bill, you just made me curious and then no more explanation. Please, don't close the book before I could read the rest. Why would Cu diffuse so evenly through all hundreds of lands under the BGAs, is 4 microns Ni really that bad barrier you think? And if so, what will happen? Will we get Copper Oxides or Copper Intermetallics that inhibit the wetting? And what did you mean with weak vias? These are offside the lands. Perhaps you aim at hidden stuff in the vias which will then mingle with the soldering? This later matter is carefully examined here, and we have found half universe's elements, but don't think this is the cause for weak solder joints, listen: the best joints are in a very narrow ring of solder joints along the solder pad's periphery. So, the best solder joints are close to the solder mask interface and then also close to the vias. If the vias were bleeding some stuff, we should expect bad joints near the , but have good ones. Some of you guys that have been help!
ful and interested will get a photo from me. So, Bill, if you can develop your sayings a little more I would be glad.
Ingemar
-----Original Message-----
From: Campbell, William (wcampbel) [mailto:[log in to unmask]]
Sent: den 26 januari 2001 21:30
To: 'Ingemar Hernefjord (EMW)'
Subject: RE: [TN] Increased Phosphorus in Electroless Ni
Sorry for the delay Ingemar, I was out on business. If the nickel layer is
too thin, you could end up trying to solder copper to your bga, in essence,
copper migration. This makes for a weak solder joint that fails under
stress/heat after initial reflow. IPC gives a spec for ni thickness, but I
don't remember what that is. Another thought I've had since about your
problem is the possibility of weak vias, perhaps a drilling problem at your
pcb mfg.
Bill C
-----Original Message-----
From: Ingemar Hernefjord (EMW)
[mailto:[log in to unmask]]
Sent: Tuesday, January 23, 2001 10:46 AM
To: 'Campbell, William (wcampbel)'
Subject: RE: [TN] Increased Phosphorus in Electroless Ni
Bill,
I will handle that proposal to our XRF specialist. Nickel is 4-5 microns,
why should this be too thin?
Ingemar
-----Original Message-----
From: Campbell, William (wcampbel) [mailto:[log in to unmask]]
Sent: den 23 januari 2001 13:46
To: 'Ingemar Hernefjord (EMW)'
Subject: RE: [TN] Increased Phosphorus in Electroless Ni
Ingemar- I haven't seen this, but I imagine x-ray flourescence can measure
the pad layers. We used it at my old job to measure plating thicknesses and
the like. It does sound to me like the ni layer is too thin. Good luck
with this. -Bill C
-----Original Message-----
From: Ingemar Hernefjord (EMW)
[mailto:[log in to unmask]]
Sent: Tuesday, January 23, 2001 6:51 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, caused by this layer, then you must
have the content of the thin layer on one or two parts, either on the BGA
balls or on the board lands. If you have these parts in your hand, what
would you do then to find out what the brittle P-rich layer is? In my
reporting I need add who was the murderer.
Sorry for harping this matter over and over again.
Ingemar
-----Original Message-----
From: Furrow, Robert Gordon (Bob) [mailto:[log in to unmask]]
Sent: den 22 januari 2001 19:07
To: [log in to unmask]
Subject: Re: [TN] Increased Phosphorus in Electroless Ni
I agree with Mark and Dave Fish. The CircuiTree article is excellent and
makes the best case yet that I have seen regarding the cause and elimination
of "Black Pad".
Thanks,
Robert Furrow
New Product Engineering
Lucent Technologies
978-960-3224 [log in to unmask]
> -----Original Message-----
> From: Mark Mazzoli [SMTP:[log in to unmask]]
> Sent: Monday, January 22, 2001 11:58 AM
> To: [log in to unmask]
> Subject: Re: [TN] Increased Phosphorus in Electroless Ni
>
> In case you guys haven't had a chance to see it yet, there's a great
> article in January's issue of CircuiTree regarding ENIG and black pad. It
> states, among other things, that those of you who are dealing with a
> modified general metal finishing bath (as most are) will most likely
> suffer
> some amount of black pad (in essence, regardless of phosphorous
> content). The cause of the black pad phenomenon has been found and fixed,
> and it has nothing to do with phosphorous.
>
> Mark Mazzoli
>
>
>
>
>
>
>
> At 04:42 PM 1/22/01 +0100, you wrote:
> >It's late to say thank you, Georg Milad,
> >but better late than never as they say on Greenland.
> >
> >Someone from Shipley have been here together with the PWB maker
> concerning a
> >superlarge BGA soldering problem. We have learnt a lot since september
> but
> >there remains issues still. What you said below is typical for most
> articles
> >and specs: layer thickness and phosphorous but little about foreign stuff
> >that can appear (even for the best in the game it seems), such as fenoxy,
> >epoxies, glycols, hydrates, carboxyls and a lot more. We made a TOFSIMS
> on
> >some board lands and found SiCH3, C2H3, C3H7, Fe, C5H9, In, SnOH, just to
> >mention an example. And added to that comes the morphologic aspects and
> >about microhardness and boundaries and size and shape of Nickel domes.
> >
> >I thought I had learnt a lot about the BGA soldering, but suddenly I feel
> >how empirical a lot seems to be. "We use to..." or "We think that..".
> >Understand that too, but would like something more in the spec than just
> >thickness and P%.
> >
> >If there is something I can hang up on the wall, and tell people 'this is
> >how a solder pad is being done' I would be vary glad. Guess all other
> >Ericsson groups agree (in silence, of course)
> >Best regards
> >
> >Ingemar Hernefjord
> >Ericsson Microwave Systems
> >
> >PS. Isn't Steph Meschter within Lockheed Martin any more or did he sign
> off?
> >
> >
> >
> >
> >
> >
> >-----Original Message-----
> >From: [log in to unmask] [mailto:[log in to unmask]]
> >Sent: den 6 september 2000 21:04
> >To: [log in to unmask]; [log in to unmask]
> >Cc: [log in to unmask]
> >Subject: Re: [TN] Increased Phosphorus in Electroless Ni
> >
> >
> >Here is my two cents worth on the topic of Electroless Ni , Phosphorous
> >content.
> >Here at Shipley our recommendation for thickness of Electroless Ni is 100
> to
> >
> >250 uins or 2.5 to 6.0 microns. For the gold thickness we recommend 2 -
> 4
> >uins (0.05 - 0.10 microns) as the best thickness to protect the Ni during
> >storage and not to create any Ni defects during processing.
> >As far as Phosphorous content in the Ni deposit we are presently staying
> >with
> >7 -9% P. We have seen data, where High phos (10 - 12%) and Low phos (5
> -7%)
> >
> >gave equally good results, with regards to incidences of "Black Pad".
> >Our tests indicate that High Phos is prone to skip plating and gold
> adhesion
> >
> >failure.
> >The IPC Plating Subcommittee 4-14 will be meeting in Miami, during IPC
> Works
> >
> >2000, at 1:30 to 3:00pm on September the 11th, 2000. The agenda of the
> >meeting is to define an IPC-Standard for Electroless Nickel and Immersion
> >Gold as well as Electroless Gold, as surface finishes widely used in the
> >industry today. Anyone interested in participating is welcome to join the
> >meeting or send his input to me, and I will keep him or her informed of
> the
> >committee progress.
> >George Milad
> >Tech Marketing Mgr.
> >Shipley Ronal Inc
> >Chairman IPC Subcommittee 4 -14
> >
> >-------------------------------------------------------------------------
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