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November 2005

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Subject:
From:
Ingemar Hernefjord <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ingemar Hernefjord <[log in to unmask]>
Date:
Sat, 12 Nov 2005 07:21:37 +0100
Content-Type:
text/plain
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text/plain (154 lines)
Steve,
Did you have a comment on that, I'm curious..
Inge

-----Ursprungligt meddelande-----
Från: Ingemar Hernefjord [mailto:[log in to unmask]] 
Skickat: den 11 november 2005 13:50
Till: 'TechNet E-Mail Forum'; [log in to unmask]
Ämne: SV: [TN] Gold plated components, what a pain!!

Steve,
As far as I can see, the pic shows a thickfilm circuit. These are always
gold/palladium or gold/platinum printed and fired at +900 Centgrades. We
have been producing such components ourselves for twenty years, and we
buy from outside also. Mounting with 3%Ag in the Sn/Pb makes the solder
joint even safer. Many or our products with these components in have
been working in the field for decades without failures reported..
Inge

-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Steve Gregory
Skickat: den 10 november 2005 15:37
Till: [log in to unmask]
Ämne: [TN] Gold plated components, what a pain!!

Good Mornin' Everyone!

We've got a little problem here that I think everyone goes through, and
maybe I can get some
pointers on how to deal with it.

J-STD-001 states that:

3.9.3 Gold Removal

Gold shall be removed:

   From at least 95% of the surface to be soldered of the through-hole
   component leads with 2.5 ìm [0.0984 mil] or more of gold.

   From 95% of all surfaces of surface mount components to be soldered
   regardless of gold thickness.

   From the surface of solder terminals plated with 2.5 ìm [0.0984 mil]
or
   more of gold.

A double tinning process or dynamic solder wave may be used for gold
removal.

Electroless nickel immersion gold (ENIG) finishes on PCBs are exempt
from
this requirement.

These requirements may be eliminated if there is documented objective
evidence available for review that there are no gold related solder
embrittlement problems associated with the soldering process being used.

I have no problem with the requirement, and I understand why the
requirement is there, but the
problem that we're having is that these gold plated parts sometimes are
discovered only when
they've been pulled for a work order to be released for production, or
even
worse, when they are
being loaded on a feeder during machine set-up.

"Hey Steve, we got a gold plated part here!" So the set-up will be
delayed,
or the assembly will
be built short and then the gold plated part hand-soldered later after
the
gold has been removed
depending on how urgent the schedule is.

We try to catch these gold plated parts in parts in receiving, if they
can
be identified there. But there are many parts are coming in sealed, and
we've discouraged sealed packaging from being opened until it is used.

Our manufacturing engineers say that they can't identify every single
part
that is gold plated without going through the datasheet of every single
part, or calling the component manufacturer, which there isn't enough
hours
in the day for them to do.

On top of the problem trying to identify the parts before they hit the
SMT
line, there is the difficulty of actually removing the gold from some of
these little beasts because of the size and geometry. For example, look
at:

http://www.stevezeva.homestead.com/LEDFootPrint.jpg

How do you go about removing the gold on something like that? JANTX
transistors are another one...

We've got a few customers that are giving indications that they might
start
banning 100% tin plated components unless they've been tinned with
standard
tin/lead solder which will only intensify the problems that we're seeing
now.

I'm just wondering how everyone else deals with this? I'm open for
anything...any suggestions at all.

Kind regards,

-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX

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