Richard,
I worked with Dr. Parker for many years and I'm sure he would tell you
there were many times I took exception to many of his comments and there
were probably many times he took exception to many of my comments. I
think that comes with the nature of engineers who are analytical.
However, he was a Bell labs Distinguished Member of Technical Staff and
the lead PCB technologist for the AT&T/Western Electric/Lucent
Technologies PCB shop in Richmond, VA. He, like I, retired form Lucent
Technologies and he is no longer trying to sell anyone PCB's his company
makes. I, like Lee, must be one of those "Silver Guys" that Steve
mentioned in his email. However, I'm willing to listen.
I don't know the analytical services lab in Minneapolis but I do know
several others who have and are working on ENIG issues. I don't want to
say they are working on "Black Pad" issues because I hate the names
"Black pad", "Blick Line Nickel", "Weak Nickel"; they describe what some
one sees not what the failure mechanism is. I should commend Gerard,
the other members of the IPC-4552 and the suppliers of ENIG chemistry.
They have done a great job of reducing, not eliminating, the occurrences
of brittle fractures users have experienced with solder joints on ENIG
boards. My view is that 4552 is a mitigation document. In Gerard's
latest email he indicates that "It is amazing that there are so many
experts on black pad but yet the extensive work by the IPC could not
produce ONE single incidence of black pad". This is the issue that
bothers me about ENIG; we don't know enough about the failure mechanism
to be able to generate the failure at will.
At the present time I run the FMA Lab for our company and I get to see
PCB assembly issues from all over the world. Immersion silver is our
surface finish of choice and has been for the past 8 years (five years
with my current company and 3 with my former company). We also have
some legacy products that still use ENIG and they are so simple (2" x 3"
x 0.020" thick RF35 double sided with 10-30 surface mounted discrete
chip components and one LDMOS on Layer 1 and ground plane on Layer 2 and
old that we have elected not to convert them to immersion silver. We
also have several large, dense advanced technology boards with ENIG
surface finish (16" x 12" x 0.104" thk, 12-layer PCB's with blind vias
1-5 and 6-12) that we inherited from companies we acquired. We have
experienced a brittle solder failure associated with ENIG on one product
and have converted that to immersion silver. The one development
product that the models appear so far to be okay happens to have been
fabricated by Gerard's company. Although these ENIG boards haven't been
a problem yet we are giving serious consideration to switching them to
immersion silver. This consideration is not due to Dr. Parker's
comments on TN, it is based on our own experience and the comments from
many people on TN as well as direct interaction with our contract
manufacturer and other CM's we interact with.
Regards,
George (The Andrew Silver Haired Guy)
George M. Wenger
Reliability / FMA Engineer
Base Station and Subsystems Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard
Sent: Wednesday, October 12, 2005 9:53 AM
To: [log in to unmask]
Subject: Re: [TN] Hasl
Gerard,
So, the days of Black Pad are over, eh?
Tell that to XXX Analytical Services in Minneapolis. I know they have
more than one analysis going on to confirm the presence of ENIG plating
issues. The symptoms are the classic "cracked mud" appearance of the
nickel under the gold.
Tell that to YYY Labs. They have been doing analysis on several ENIG
issues in the past few weeks.
Tell that to the folks at many other fabricators struggling to fix ENIG
plating issues. They may not all admit it, but there are many who are
still struggling with the reliability problems inherent to ENIG.
One of the reasons two different fabricators closed down in the Twin
Cities area last year was due to liability issues with ENIG plating. Not
the only reasons, but definitely a big factor.
Sorry to be so negative. But I have to tell you that what I see and what
you are saying are two completely different things.
Mr. Parker has company. Lots of it.
You may not be aware of it. That does not mean the problems don't exist.
The problems are beginning to be better understood. And once again I
state that ENIG is a good finish, if done properly.
And once again, for sure, it is not the best finish to use with area
array packages such as BGAs, interposed components, and CSPs. You cannot
deny that nickel's dissolution into the IMF is much more difficult to
achieve, requires higher reflow temperatures at a longer time. This is
exacerbated by the fact that array packages induce an insulating affect
to the solder joints underneath.
Yes, to all of you who will respond that you never have had a problem
with it. That is good, you have a good supplier. Stick with it.
But too often it is not, and the results are absolutely devastating to
the end customer who ships his product everywhere, only to see their
product fail in the field. It has happened to more than one company that
I have worked at. No matter what anyone tells me, it presents a risk I
would rather not take.
I have pushed many other companies other than the ones I worked for
directly to switch to immersion silver, if the finish is the proper one
for the service environment. They all have, with good results.
I am sorry, but I have not a single problem to report with immersion
silver. None. I can think of over 20 major programs I was involved with
that are using it. Military programs are using it.
High-frequency/high-impedance telecommunications companies are using it.
Medical programs are using it. They have all been using it for more than
4 years now.
And as long as I continue to hear of the ENIG horror stories elsewhere,
I will try to stay away from it.
How anyone can state that there are no more problems with ENIG in the
face of reams of articles, white papers, and reports in every single
major industrial magazine related to electronics assembly, and every
single major trade show, etc. in the past few years is mind-boggling.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerard O'Brien
Sent: Wednesday, October 12, 2005 7:51 AM
To: [log in to unmask]
Subject: Re: [TN] Hasl
Lee - as co-chairman of 4552 I have to take exception to your continuing
negative comments on ENIG. You may be the most unlucky individual on the
planet continuously finding the remaining bad ENIG suppliers, but ENIG
is a mature, high reliable surface finish. We created the 4552 document
to be used to weed out the bad suppliers as well as defining a realistic
deposit thickness to provide a reliable surface finish with excellent
solderability and shelf life. The days of "black pad", whatever the
true definition is, are over. Both myself and my committee would be
delighted to review your data that has the black pad phenomena tied
directly to a deposit over 4 micro inches, perhaps you could stop by the
4-14 meeting at Los Vegas.
Chemical suppliers, FAB houses and industry have worked to produce a
deposit that is multifunctional and world class. If you read the
technical paper in the back of 4552, you will see that a 1 micro inch
deposit was tested as the lowest deposit thickness, which I am still
testing in real time, unprotected going on for 42 months. We obviously
did not spec 1 micro inch minimum as it is not a practical deposit
thickness to maintain on a daily basis, but it proves the point that
thin I Au protects the underlying Ni very well, contrary to you own
experiences unfortunately.
Regards
Gerard O'Brien
Co-chairman 4-14
.
-----Original Message-----
From: Lee Parker [mailto:[log in to unmask]]
Sent: Tuesday, October 11, 2005 9:45 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl
Joel
I am glad to here that you are successfully using ENIG boards;
unfortunately this has not been the case with some other OEMs and CMs.
Almost every week in this forum, I see a report of a problem with ENIG.
I myself spent this spring moving several clients from ENIG to other
solderability coatings. It has been my experience that if the gold
thickness is <2 microinches there is a serious risk of poor
solderability.
If the gold thickness is> 4 microinches black pad may become a problem.
The issue can also be elevated or diminished by the particular plating
chemistry and the ability of the fabricator to control the process.
Consequently, I often work with clients to evaluate and migrate too
other hard metal finishes such as immersion silver and flash gold. The
attributes of immersion silver have been discussed here at length many
times and I am an advocate. I installed the first immersion silver line
in North America at the AT&T plant in Richmond. I then worked with most
of the AT&T assembly locations to verify the process.
Flash gold is more recent and is found mostly in Chinese PCB shops where
it has been resurrected and improved upon. In fact, we used a similar
process at the AT&T facility in Richmond many years ago for "other" OEM
boards. Most Chinese shops have installed the process and have made
substantial improvements. The price is competitive. I along with others
will be giving a paper on this process at the IPC February meeting.
As an aside, this is probably the first novel technology innovation to
originate in the Chinese PCB industry and we should all take notice. I
believe we are seeing the same ingenuity in the Chinese PCB shops that
Marco Polo found on his first visit to China when he returned to Venice
with firecrackers and gun power.
Best regards
Lee
J. L. Parker Ph.D.
JLP Consultants LLC
(804) 779 3389
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joel Mearig
Sent: Tuesday, October 11, 2005 3:54 PM
To: [log in to unmask]
Subject: Re: [TN] Hasl
Lee,
Good input that I agree with. However, I was wondering if you could
further
discuss the "flash" vs. "ENIG" issue. I have been using ENIG on my
Pb-free
assemblies for about 7 years with very little problems. If I am missing
something further education would be extremely helpful. Thanks
Joel Mearig
Delta Tau Data Systems, Inc.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
Sent: Tuesday, October 11, 2005 10:03 AM
To: [log in to unmask]
Subject: Re: [TN] Hasl
Ramon
After reflowing a soldered surface, you will form a meniscus which will
interfere with SMT component placement. To avoid the problem I suggest a
flat metal finish such as immersion silver or flash gold (not ENIG)
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: Dehoyos, Ramon<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Tuesday, October 11, 2005 12:52 PM
Subject: [TN] Hasl
Hi technetters:
Is there a fine pitch limit to the use of HASL board
plating
finish due to its variation in thickness? Does selective solder strip
and reflow plating, SSSR, have a significant advantage over HASL? Any
comments relating to platting finish would be greatly appreciated. I
thank you for your comments.
Ramon
ME
410.552.2210
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