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October 2006

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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Tue, 17 Oct 2006 15:08:03 -0700
Content-Type:
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Anyone has a surplus of gold = ping me 'cos I know a safe place where I can
dispose of it - for free!!

John

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: Tuesday, October 17, 2006 12:37 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG problem

Inge,

I am still trying to comprehend where all that gold came from!

My thought was that your supplier put on an 'edge connector gold - being
cobalt hardened, for wear resistance, but then all pads would be of uniform
thickness and properties.   ... so I guess that is not the case.  ...... Any
hardening agent - Thallium, Cobalt, Nickel, Copper ....  Won't EDS/EDAX pick
these up?

Am hoping the George comes back with an answer for my confusion as to why
the gold apparently plates thicker on the bare copper, compared to the
nickel - or maybe I just have my head up where the sun don't shine.  [Must
have already gone down over there!]



Even if burnishing helps, I can still imagine a great deal of grief in being
able to 'turn-ON' Production .... but it may give insight.

Personally, I don't find the ENIG gold to be all that 'soft' by any means.
Definitely not like good ol' electroplated, pure, soft gold .... that one
could almost lay the wire on and have it adhere nicely.

Steve

-----Original Message-----
From: Hfjord [mailto:[log in to unmask]] 
Sent: Tuesday, October 17, 2006 3:21 PM
To: TechNet E-Mail Forum; Creswick, Steven
Subject: Re: [TN] ENIG problem

N.Y.

Good advice!! Why didn't we think of that? Me stupid. Will ask the guys to 
make burnishing tomorrow. Splendid. You not stupid.

Yap, same experience. I worked with the development of a little computer 
made with LTCC technology, and we used copper all the way, all layers, even 
top layer. Bonding was not a problem. So, even if there are copper particles

on the ENIG, it should not lower the pull value. So, focusing on the copper 
particles could be misleading. You not stupid.

Cobalt? Then EDAX is not useful, need chromatographics, which we have. 
Cobalt hardner is used by jewellers, correct? You give me another thread. 
Yes. If the two hardnesses do not coincide, there will be insufficient 
friction and thus lower pull value. ENIG and aluminum wire must match.  I'll

check wire hardness and see if we have doped wires for testing. Again, you 
clever trikeman.

Many thanks. People are waiting for my advice. Two fully automatic lines.

Inge


----- Original Message ----- 
From: "Creswick, Steven" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, October 17, 2006 8:49 PM
Subject: Re: [TN] ENIG problem


Inge,

As I recall, I could ready bond clean copper, and the pulls would remain 
good so long as I left them in an oxidizing environment - eg, not in a 
hybrid/MCM!

Had to ask the simple question about the process.  You understand looking 
for the simple things first.

Interesting color indication.  Sure sounds like copper coming through, 
doesn't it.  Although not a solution, what happens if you burnish the 
surface, then try to bond?  If it were oxides, wouldn't it bond better now?

Could you check for Co in the gold?  Besides an apparently rough surface, 
could the presence of an exceptionally hard gold be another factor?

George Milad - I don't quite understand.  It seems as though you are saying 
that the gold thickness will be self-limiting on Ni, but turns into 
auto-catalytic on Copper??  Wow!  Inge is seeing nearly 40 µinches of Au! 
Can you explain further please?

Steve - N.Y.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Monday, October 16, 2006 2:24 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG problem

You are right. We have re-prepared the samples several times, because we
doubted that the gold thickness was correct.  Polished with various grids
4,000 to 7,000. Used weak etchants and other tricks, but got same result.
Thin areas, just nanometers of gold. Thick areas, more than one micrometer.
I'm not sure, but in the cross section, it looks like being a little copper
between the nickel and the gold. Furthermore, the nickel seems to have
microcracks all the way from the gold and down to the copper.

Did I tell you that the board's gold looks quite normal at the arrival from
China, but looks reddish after the assembly is finished? Like diffused
copper in gold. I've seen copper diffuse through nickel, but then the nickel
was very thin.

Inge


----- Original Message -----
From: "George Milad" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, October 17, 2006 6:48 PM
Subject: Re: [TN] ENIG problem


> Ingemar,
>
> One thing attracted my attention when I read your posting. You  stated
> that
> the gold was very thick (>1um)
>
> As a supplier of ENIG Chemicals and the chairman of the plating committee
> that specified ENIG as surface finish, I can tell you that the process is
> not
> capable of depositing that thickness of gold on nickel.
>
> The only time this gold thickness may be encountered is when the nickel
> plating skips the pad (does not or fails to plate) and the gold is
> deposited
> directly on a copper pad.
>
> Verify the Ni thickness on that specific pad that had the very high gold
> deposit thickness. this may give us a clue as to what is behind the
> failure.
>
> Regards
> George Milad
> George Milad
> National Accounts  Manager for Technology
> Uyemura International Corp (UIC)
> 249 Town Line Rd
> Southington CT 06489
> [log in to unmask]
> Cell: (516) 901  3874
>



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