All Y'all (plural for y'all)
I hate to be the only naysayer in the bunch but Palladium is not without
it's issues and process adjustments.
In my experience the plating thickness is critical for performance in
maintaining solderability while still allowing for solder fillet formation
and performance in the product operational environment. To that end here
are some places that know how to plate palladium and some that do not. If
you don't use one that does you are in for a time.
Most of the product performance issues (given reliable component resources)
were usually related to inadequate formation of the solder fillet. Consider
that the time to solution of palladium is many times that of gold, which it
often replaces, and it will allow some insight as to the profile
modifications you might consider. The time at reflow temperature needs to
be adequate to compensate for the difference or you wind up with a solder
fillet that is so weak that any lead tension will lift it out of the solder
attachment during operation and/or over time. Many of the failure analysis
cases I've seen would have the lead separated from the contact area with an
outline of the lead on the pad. The lead was probably as shiny as when it
was soldered originally but no connection.
Mel Parrish
Soldering Technology International
102 Tribble Drive
Madison, AL 35758
256 705 5530
256 705 5538 Fax
[log in to unmask]
www.solderingtech.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Wenger, George M.
Sent: Thursday, May 09, 2002 12:12 PM
To: [log in to unmask]
Subject: Re: [TN] Palladium Leads
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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