Hmm.
Well if they don't wet/solder and can't be repaired then they are unusable.
So far as the leaching is concerned, as Dave said you have an unknown. Even
if they look good I would be giving them a prod. Could be you just have a
mechanical (vice like) grip between the two fillets as it's entirely
possible the terminations have leached off completely, or are at least
compromised.

-- 
Regards 
 
Mike 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Wednesday, September 23, 2015 4:04 PM
To: [log in to unmask]
Subject: Re: [TN] Capacitor with AgPdCu Terminations...

Hi Steve - the problem with Pd/Ag type terminations that do not have a
barrier layer such as nickel or copper is that you have an unknown
timeline. We know that the Pd/Ag termination is diffuses into the molten
solder joint but its a time/temperature equation for which most folks don't
have enough process characterization to know where they finally end up in
terms of loss of termination. But - if you have made a good solder joint
then the "leaching" is done and that solder joint should be acceptable per
the design. If you go to touch it up, then no, you just make the situation
worst as more termination will be consumed and at some point you have a
mechanical connection and not a metallurgical connection. If you do have a
barrier layer then you don't have a "leaching" issue. The photo you had
shows a solderabilty issue which is very common for Pd/Ag type
terminations. If the solder joints don't meet the JSTD-002 wetting/geometry
criteria, I would replace them with your alternative component.

Dave Hillman
Rockwell Collins
[log in to unmask]

On Wed, Sep 23, 2015 at 9:11 AM, Steve Gregory <[log in to unmask]> wrote:

> Morning All,
>
> I've just had a problem that I've seen before, but when I seen this in the
> past it was with Tin/Lead soldering, this time it's with Lead Free SAC
> soldering.
>
> We're building a board for a customer and one of the caps called out is
TDK
> PN# CGA3E2X7R1H472K080AD. It's a cap made for conductive epoxy and has
> AgPdCu terminations. Well I missed it in the BOM and we've already built
> the boards. It was brought to my attention that our rework operator was
> having trouble getting the caps to solder and wanted me to take a look at
> them. As soon as I seen them I went; "Oh crap..." and then pulled up the
> datasheet to verify my suspicions. Here's a photo of the cap:
>
> http://stevezeva.homestead.com/TDK_AgPdCu.jpg
>
> So I made the call that the caps needed to be replaced, with a more
> suitable cap like this AVX PN# 06035C472KAT2A. It has a Tin-Nickel
> termination and has a X7R dielectric, and is also 4700pf +/- 10%. Some of
> the existing caps have solder wet to them, but the solder joints are very
> minimal. Knowing how bad these leach I'm leery about leaving them on the
> board. Should they be left on the board if they have a minimal solder
> joint? The ones that have not wet cannot be touched-up, as soon as you hit
> them with a soldering iron the termination dissapears.
>
> Right now we're waiting on the customer to approve the AVX cap.
>
> Steve
>
> --
>
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