Sefika
There are a number of flat metal finishes from which to choose: immersion
silver, flash gold etc. These generally perform well; however, when a
process goes out of the processing limits you can expect trouble. It is the
suppliers job to insure this does not occur or that all questionable product
is captured. It is the OEM's job to set the end point specs.
Regardless of the finish you select, I suggest you go through a
qualification process and then place end point requirements on the product
and that you rigorously enforce these requirements. I know of one OEM that
has a very long check list of end point requirements that are enforced.
Although it was inconvenient and expensive to the supplier, great care is
taken with their product. This OEM seldom has quality issues once the
supplier understands the consequences.
Best regards
Lee
----- Original Message -----
From: "Şefika ÖZKAL" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, May 15, 2006 2:19 AM
Subject: Re: [TN] Question about ENIG in SnPb process . . . .
> Dear Technetters,
>
> Instead of ENIG what should we choose? For example, for high density (with
> bgas) boards with some of the components lead-free plated?
>
> Moreover what is the choice when the components assembled to the boards
> are
> both lead-free alloy plated and lead alloy plated (mixed)?
>
> Regards
>
> Sefika
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> Sent: Friday, May 12, 2006 11:52 PM
> To: [log in to unmask]
> Subject: Re: [TN] Question about ENIG in SnPb process . . . .
>
> LOL Werner,
> I totally understand where you are coming from. As a process engineer,
> you should see how much hell I need to go through to verify that the
> root cause of the solder reliability issues is not the process but the
> pwb finish, or issues related to it. And identifying surface finish
> problems is not easy, nor cheap. We usually need to go to an outside
> failure analysis house to get verification. This is very costly. Thus I
> also have a somewhat biased opinion towards ENIG using standard 63/37
> solder. And as you pointed out, Werner, the lead-free alloys combined
> with ENIG makes the situation potentially much worse.
> With ENIG, some of the plating issues are exacerbated by further thermal
> cycles during normal processing. This is why it is difficult to prove
> "is it the plating, or is it the process". There quite often are
> situations where it is a little of both.
> When I am working with military hardware (or really, any electronic
> assemblies), the last thing I want to take a chance on is solder
> reliability issues with the board finish that go undetected until
> hundreds or even thousands of assemblies are built and in the field.
> Because of ENIG's fickle nature, and because I do not like to solder to
> nickel for all of the reasons that are well documented here in the forum
> archives and hundreds of white papers, articles, and so forth, I simply
> try to stay away from it whenever possible. Why would I ever need to use
> it, except for in certain situations and space applications where it is
> not qualified?
>
> And Gerard, I want you to understand I respect your knowledge and
> opinions fully, I simply choose to disagree with you on this.
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
> Sent: Friday, May 12, 2006 1:15 PM
> To: [log in to unmask]
> Subject: Re: [TN] Question about ENIG in SnPb process . . . .
>
> Thanks Lee, Richard & Daniel,for backing up my experience.
>
> Gerard, of course, as a consultant clients come to you when they have
> problems, not when everything works as advertised. So, purely
> statistically, consultants get a one-sided picture.
> As a consultant, one of your first obligations is to do no harm with our
> advice [sort of like physicians]-having seen what I have, there is no
> way I can advise a client in favor of ENIG. Of course it works most of
> the time, but God help me i advice ENIG to a client and all hell breaks
> loose.
>
> Werner
>
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