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May 2002

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Subject:
From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 9 May 2002 13:11:48 -0400
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The one thing you need to keep in mind is that Pd does what it does in a muffler (i.e., pulls things out of the environment) so you need to know your "environment" and the "environment" the parts were exposed to before you received them in order to know anything about their solderability and shelf life.

In my previous company we used lots of TI PdNi plated IC packages.  Our assembly engineers would rather have used SnPb plated packages but most times you may not have a choice.  Most assembly engineers usually don't have many choices.  Even if they get components that have horrible solderability the answer usually is we need to build product so use them and will scream at the component vendor later.  Most of the reliability studies I've seen or conducted have shown solder joints made to PdNi plated components meet most solder joint integrity/reliability requirements.  The reason assembly engineers don't like PdNi plated components is because the solder joints look different than those made to SnPb plated components.  Assembly engineers in my previous company typically used a single profile for forced convection reflow surface mounting of a given product. They usually didn't increase the temperature because there were some PdNi plated components on their boards.  We used to refer to solder joints made to PdNi plated parts as having an "alligator" surface texture rather than a smooth shiny surface.  Metallurgical evaluations indicated that the surface texture us due to concentrations of pd near the surface.  If we increased reflow profiles 5 to 10C hotter the "alligator" texture would be less pronounced.  What we wound up doing was retraining operators and providing visual aids for inspectors.

We did have at least one case where we had PdNi plated parts that won't solder.  The component vendor indicated that there was organic contamination of the components before we received them.

Regards,
George

George M. Wenger (908)-546-4531 [log in to unmask]
Distinguished Member Technical Staff
Celiant Corporation, FMA Lab, 40 Technology Drive, NJ 07059



-----Original Message-----
From: Guy Ramsey [mailto:[log in to unmask]]
Sent: Thursday, May 09, 2002 11:20 AM
To: [log in to unmask]
Subject: Re: [TN] Palladium Leads


I did a little search on the web and found that TI claims eight years when
stored in their packaging . . . three years outside of it . . . HA!

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Earl Moon
> Sent: Thursday, May 09, 2002 9:07 AM
> To: [log in to unmask]
> Subject: Re: [TN] Palladium Leads
>
>
> Bev and others,
>
> I've worked with Pd in one way or another, starting with hybrids in the
> '60's but never thought about solderability over time. What is the "shelf"
> life of Pd compared, say, with SnPb? Know the question is too general but
> any guesses?
>
> Earl
> ----- Original Message -----
> From: "Bev Christian" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, May 09, 2002 7:59 AM
> Subject: Re: [TN] Palladium Leads
>
>
> > Henry,
> > Back in the mid 90's when these parts (TI palladium plated) were
> introduced
> > in the company I worked at then, we had some teething problems.
>  But with
> > some profile manipulation and training of operators we did not have any
> > issues (Of course there was lab testing in the background).
> The training
> > had to be done because there will be more wetting angles closer to 90
> > degrees than they are used to.
> >
> > One other very important thing, this finish and I suppose other
> palladium
> > finishes, is/are finicky when it comes to fluxes.  Some no-cleans work,
> > others don't.  We were lucky our old standard fluxes - Kester
> R243 solder
> > paste and 923 and 924FB wave solder fluxes worked well.  Others didn't.
> >
> > And finally, how old are your parts and what conditions have they been
> > stored in?  I'm sure others will come up with other good questions and
> > hopefully a few hints for you.
> >
> > regards,
> > Bev Christian
> > Research in Motion
> >
> > -----Original Message-----
> > From: Henry Rekers [mailto:[log in to unmask]]
> > Sent: May 8, 2002 8:33 PM
> > To: [log in to unmask]
> > Subject: [TN] Palladium Leads
> >
> >
> > Has anybody out there experienced non-wetting problems with no-clean
> > solderpastes on parts that have palladium coatings on the leads.
> > Specifically, have you had this problem with Texas Instruments parts?
> >
> > Thanks.
> >
> > Henry J. Rekers
> > Manufacturing Engineer
> >
> >
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