George,
I found this article on the Cookson homepage, it is more
related to black pad issue and the heading (failure mechanism, from
beginning to end) seems to cover much of the kinetics involved.
I just thought it would be of any help, anyway.
Regard, Ivan
Il giorno 12/ott/05, alle ore 17:10, Wenger, George M. ha scritto:
> 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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