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May 2006

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Subject:
From:
"Douglas O. Pauls" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 16 May 2006 15:27:39 -0500
Content-Type:
text/plain
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text/plain (203 lines)
Dewey,
You make it sound like I died and this is my eulogy.  Past my prime?  You
been talking to my wife?

As to the rest, I think you been sniffing the cactus flowers
again.............

Doug Pauls




             "Whittaker, Dewey
             (AZ75)"
             <Dewey.Whittaker@                                          To
             HONEYWELL.COM>            [log in to unmask]
             Sent by: TechNet                                           cc
             <[log in to unmask]>
                                                                   Subject
                                       Re: [TN] Question about ENIG and
             05/16/2006 03:05          other surface finishing
             PM


             Please respond to
              TechNet E-Mail
                   Forum
             <[log in to unmask]>
             ; Please respond
                    to
             "Whittaker, Dewey
                  (AZ75)"
             <Dewey.Whittaker@
              HONEYWELL.COM>






Either tis' true that the memory is the first to go
Or Doug Paul's fame has "Stoop"ed to a new low
Some may think he has past his prime
But we say not in our life time
To defend his position he'll go toe to toe
Cause his answers will always win, place or show
With all his expressions he could be a good mime
although what he lacks in rhythm, he makes up in rhyme

In honor of Doug Pauls;
Owner of the answer " It depends".
Wannebe Poet-laureate of tech-net
Friend
And truly great supporter of our Industry
Dewey






-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger Stoops
Sent: Tuesday, May 16, 2006 7:34 AM
To: [log in to unmask]
Subject: Re: [TN] Question about ENIG and other surface finishing

I just received a question from someone inside my organization asking
about why not use ENIG instead of Iag because of storage issues...
Doing a quick Internet search took me to a paper at
http://www.mse.uiuc.edu/Faculty/Shang/Preprints/1997-2006/JMR00-pilin.pd
f#search='tin%20nickel%20intermetallic%20strength'
discussing "a comparative fatigue study of solder/electroless-nickel and
solder/copper interfaces."  It's dated from 2000 and does not include
any study using Pb-free solders.  Final thought is that Sn-Ni SJs do not
behave well under high stress environments after aging.
Found a few others, Daan's website was also very helpful, but time does
not permit further discussion.
We have used ENIG, Iag, HASL, Pb-free HAL, and it seems our choices (as
far as I have anything to say about it) will likely be Iag and Pb-free
HAL, due to our operating environment and quality requirements.
So, should one use ENIG instead of other SFs?  In the now immortal words
of (can't remember who, sorry), "It Depends"...

Roger

-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Monday, May 15, 2006 4:50 PM
Subject: Re: Question about ENIG and other surface finishing

Good points, George.
Trouble is, in order for the temperature under a large BGA to reach 220C
for any duration, the rest of the component leads on the assembly will
be close to what? 235C? Not a good process for some components.
The problem with the logic that the ENIG will work better at higher
reflow temperatures seen with Pb-free processes is this:
The plating issues that cause the nickel oxide formation during the
immersion gold step (related to the phosphorus content, amongst other
variables) are exacerbated by subsequent temperature excursions. If the
plating is properly done, then yes, perhaps the IMF formed to nickel
will be more easily accomplished. However, if NOT done properly, the
higher temperatures will make the Black Pad and other nickel plating
process-related problems much, much worse.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of George Milad
Sent: Monday, May 15, 2006 2:15 PM
To: [log in to unmask]
Subject: Re: [TN] Question about ENIG and other surface finishing

I believe one of the key issues in assembling ENIG parts is that the
inter-metallic formed is a Ni/Sn. Ni/Sn inter-metallic requires  higher
peak assembly temperature and a longer dwell at peak temperature. The
right  re-flow temperature profile is a must.

The recommendation of ENIG assembly is 220 C for 20 seconds.

Some of the failures with ENIG may be attributed to colder assembly
temperatures.

The transition to Pb-Free should favor ENIG as the assembly temperature
for Pb-Free is going to be higher and the Ni/Sn inter-metallic will
always be formed  successfully.


Best  regards

George Milad
[log in to unmask]
National Accounts Manager  for Technology Uyemura International
Corporation Technical Center 240  Town LIne Rd Southington CT 06489
(516) 901 3874 (mobile)
(860)  793-4011 (office)
(860) 793-4020 (fax)

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