Welcome back Inge

Best Wishes
 
 
 
Mike


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Wednesday, December 05, 2012 4:55 PM
To: [log in to unmask]
Subject: Re: [TN] Termination finishes, Cu thickness under Ag, Au-Pt-Pd

Hi Wayne & collegues,

heard from Joyce that you missed my comments. Sorry for that. When Steve
Gregory faded away as kind of bagpipe blower in the TN brigade, I lost some
contact with the troops march and became last one and with time I saw the
troops at distance. Well, with  my old legs, seems as I have to get lift
with a jeep and catch up with you.

On the theme you just discuss with Julie, I'd say to her not to mix with
changing the component finish immediately. Doing such things can end in a
never-ending-process. I am not updated with what is actually going on, so
my advice may not be of any help, but there is one soldering method that
have a very generous process window and that is VPS, Vapour Phase
Soldering. It has some very attractive advantages, like instant and
simultaneous heating, extremly low Oxygen presence and is very fast. All
properties that makes even many poor weldable>acceptable weldable. You may
not be able to try this, of some reason. Just wanted to put up a finger and
feel the wind direction

Inge

On 5 December 2012 00:41, Thayer, Wayne - IS
<[log in to unmask]>wrote:

> Hi Julie-
>
> Sorry for the late response.  I have a lot of experience with this or
> similar material.  Yes, burnishing helps.  I also deliberately use an iron
> tip that doesn't wet well.  Paste with SMT works too, and is more
> controllable.  We typically used the SnPbAg alloy with about 2%Ag, but I
> don't know if that helped.  Our rule of thumb was you got three shots to
> solder to it, IF you used pre-heat and were very careful.  BUT, this
> product is cake to solder to compared with AgPd, which most of the thick
> film commercial products used.  That stuff would only survive a very
> carefully controlled single reflow.
>
> One thing we learned is that the leach rate SKYROCKETS if the designer put
> the PtPdAu directly on top of thick film Au where the solder was going to
> be.  That recipe leaches just as bad as plain gold.  The overlap MUST be
> behind a solder dam.  (The thick film vendors only tell you this AFTER you
> figure it out on your own!)  By the way, plain gold solders just fine on
> ceramic using SnAu eutectic solder.  It is very expensive and is quite hot
> (270C or so).  The joints are very pretty shiny silver and very strong.
>  You can also weld copper wires to thick film gold or silver.
MiniCircuits
> sells piles of RF parts containing tiny transformers attached this way,
and
> this technique is also used on RF inductors which are wound on an alumina
> mandrel.
>
> We ended up having a low temperature copper put on top of the gold
> whenever we could.  It is much more robust--still wets horribly though!
>
> Wayne Thayer
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
> Sent: Wednesday, November 28, 2012 8:59 AM
> To: [log in to unmask]
> Subject: Re: [TN] Termination finishes, Cu thickness under Ag, Au-Pt-Pd
>
> Julie,
>
> Yes, the addition of a small amount of Pt does slow up the rate of the
> conductors leaching into the solder.  From practical experience, the more
> Pt is added, the better the leach resistance.  However, the more Pt is
> added, the greater are wetting problems.
>
> Thick film ink suppliers [used to] offer inks with different amounts of Pt
> so you could slightly 'chose your poison.'
>
> Also can depend on whether it is a fritted, or a frit-less, system.
>
> Like Mike says - BURNISH before solder IS the general rule!
>
> Never was something you really 'wanted' to solder to, unless you had no
> other choice.
>
>
> Steve Creswick
> Sr Associate - Balanced Enterprise Solutions
> http://www.linkedin.com/in/stevencreswick
>                          616 834 1883
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
> Sent: Tuesday, November 27, 2012 8:02 PM
> To: [log in to unmask]
> Subject: Re: [TN] Termination finishes, Cu thickness under Ag, Au-Pt-Pd
>
> The claim of the supplier is that the Pt prevents the Au from dissolving
> into the solder.  Hmmm.  Can anyone back that up?
> The recent info on this is that it's looking like a wettability problem
> more than a dissolving-into-the-joint problem, although neither is
> confirmed.
>
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