Steve,
If you do not prefer the SERA testing to measure/evaluate
the amount of copper migration, what method/test are you doing to insure
that you are giving your customer a good solderable surface. Please explain?
Tony Steinke
AIT-Atlanta Inc.
----- Original Message -----
From: "Steve Kelly" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, June 19, 2002 11:13 AM
Subject: Re: [TN] Immersion Tin
> SERA will not help you - it is only a tool to measure tin /copper
> concentrations . We have been running immersion tin for 5 years with no
> issues but only one thermal excursion is allowed. The tin forms a
> copper/tin intermetallic after thermal. We even silkscreen before tin to
> eliminate this bake cycle. Regards Steve
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
> Sent: Wednesday, June 19, 2002 12:07 PM
> To: [log in to unmask]
> Subject: Re: [TN] Immersion Tin
>
> Hi Tony,
>
> we experienced poor wave soldering after 2 reflows with immersion tin.
> So,
> please give me a few hints on SERA. Is it a test that the board house
> will
> do, or it has to be at our incoming? Does it imply additional charges?
> Where
> can I read more?
>
> Thanks,
> Ioan
>
> > -----Original Message-----
> > From: tony steinke [SMTP:[log in to unmask]]
> > Sent: Wednesday, June 19, 2002 11:19 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Immersion Tin
> >
> > Grant,
> > Having installed the Cookson(Dexter) FST chemistry a couple of years
> > ago at my previous employer, there are concerns that you should be
> aware
> > of.
> > The immersion tin
> > process is a beautiful thing if applied and processed properly. Some
> of
> > the
> > major
> > issues that I experienced were:
> > Solder mask adhesion(you should tape test any incoming product)
> > Request that SERA(sequential electromigration reduction analysis) test
> be
> > performed.
> > And the biggest problem was getting acceptable solderability on second
> > pass
> > wave solder
> > or second pass solder paste. The copper migration greatly accelerates
> > during
> > any thermal
> > excursion, but that is what the SERA testing will show you.
> > Tony Steinke
> > [log in to unmask]
> >
> > ----- Original Message -----
> > From: "Grant Emandien" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Wednesday, June 19, 2002 3:06 AM
> > Subject: [TN] Immersion Tin
> >
> >
> > > Members,
> > >
> > > A PCB supplier has requested us to evaluate immersion tin as a
> finish.
> > > Immediate concerns raised were shelf life, solderability, whiskers,
> etc.
> > > Researching the archives has noted similar as well as opposing views
> and
> > > concerns. In addition to possible problems arising from immersion
> tin
> > > finish, what PCB fabricator process changes may contribute to
> possible
> > > reliability and solderability concerns and how this impacts
> production
> > > processes such as reflow. The proprietary chemistry used is MacStan
> HSR
> > from
> > > Macdermid.
> > >
> > > Anyone willing to share experiences and guide me towards making an
> > informed
> > > decision.
> > >
> > > TIA
> > > Grant
> > >
> > >
> > >
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