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March 2005

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Subject:
From:
"Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ingemar Hernefjord (KC/EMW)
Date:
Thu, 17 Mar 2005 08:06:02 +0100
Content-Type:
text/plain
Parts/Attachments:
text/plain (315 lines)
We have been brazing terminals to HiVoltage caps long ago. As far as I remember, we used a Copper/Silver alloy, i.e. real brazing, not soft soldering. I set up a induction coil solder machine for that purpose.  Now, I don't know where the limit between soft soldering and brazing is, but I mean that PbAg2.5 is soft soldering slightly avove 300C. If you use that alloy at 710C, you certainly have a problem. Must confess that I cannot follow your thinking..
Regards
Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: - Bogert [mailto:[log in to unmask]]
Sent: den 17 mars 2005 00:21
To: TechNet E-Mail Forum; Ingemar Hernefjord (KC/EMW)
Subject: Re: [TN] Capacitor Terminal Silver Braze Problem


March 16, 2005
 
One possible problem may be excessive heat used during the braze process.  Do you have any info on what happens to Ag2.5 solder at elevated temperatures.  For example, would brazing at 710C cause the noted problem?  

----- Original Message ----- 
From: Ingemar Hernefjord  <mailto:[log in to unmask]> (KC/EMW) 
To: [log in to unmask] 
Sent: Wednesday, March 16, 2005 6:55 AM
Subject: Re: [TN] Capacitor Terminal Silver Braze Problem

Great, Steve, your new style will make success.

About cap, seems like what I suspected, kind of HiVoltage filter cap. 
Even with those fine pics, it's not easy to see what is what.
From my view, looks like solder fatigue cracking caused by mismatch.
Some sources regard that too as 'corrosion', kind of 'mechanical corrosion'.
Grain sliding and it's consequencies....
A simple drawing would make tele-analysis easier..
Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]
Sent: den 15 mars 2005 20:52
To: [log in to unmask]
Subject: Re: [TN] Capacitor Terminal Silver Braze Problem


Hi All!

It's been one them days...too much to do and not enough hands. Plus,
I'm feeling a bit on the lousy side...hope I'm not getting the flu.

Anyways, I got Les's pictures up. Go to:

http://www.stevezeva.homestead.com and look at  "Capacitor Terminal
Top View, 4 o'clock Position, 8 o'clock Position, and 10 o'clock Position".

I've also changed my website a bit...a little birdie told me it was getting
boring...

Kind regards,

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


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|         |           03/15/2005 04:28 |
|         |           AM               |
|         |           Please respond to|
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  |       To:       [log in to unmask]                                                                              |
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  |       Subject:  Re: [TN] Capacitor Terminal Silver Braze Problem                                             |
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March 15, 2005

Thanks
  ----- Original Message -----
  From: Stephen Gregory< mailto:[log in to unmask]>
  To: [log in to unmask]<mailto:[log in to unmask]>
  Sent: Monday, March 14, 2005 9:52 PM
  Subject: Re: [TN] Capacitor Terminal Silver Braze Problem


  Les,

  Send your images directly to me, and I will post them for everyone to
  view...

  Kind regards,

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



                        - Bogert
                        <[log in to unmask]<mailto:[log in to unmask]>>
To:       [log in to unmask]<mailto:[log in to unmask]>
                        Sent by: TechNet         cc:
                        <[log in to unmask]<mailto:[log in to unmask]>>
Subject:  [TN] Capacitor Terminal Silver Braze Problem


                        03/14/2005 06:12
                        PM
                        Please respond to
                        TechNet E-Mail
                        Forum; Please
                        respond to -
                        Bogert






  March 14, 2005

  Folks, the attached photographs show some type of problem with a silver
to
  ceramic braze joint.  The joint provides a seal around a capacitor
  terminal.  The manufacturer rejected the terminal due to the noted
  conditions.

  In the photo titled top view, the white area on the outer diameter is a
90%
  Alumina ceramic.

  Next to the ceramic is the silver braze connection that connects the
  ceramic to 304 stainless steel using Ag 2.5 silver solder (i.e.,
  97.5PbAg2.5).

  In the middle of the top view photo is a copper terminal.

  The other three photos show the top view enlarged in the 8 o'clock, 4
  o'clock and 10 o'clock positions.

  As you can tell from the photographs, the silver braze joint appears
  corroded.  Also, there appears to be poor or non-wetting to the 304 SST,
or
  otherwise a crack formed.

  We used a knife in the area from the one o'clock position to about the 2
  o'clock position and were able to easily scrape away the top surface of
the
  braze down to about a 1/64 inch or > depth till we got to solid braze
area.

  We had an analysis performed that did not show any chlorides, just silver
  and lead.  It could be that the stuff we were able to scrape away is some
  form of lead oxide, not sure.

  I note that the historical QQ-S-571 specification in section 6 indicates
  that Ag2.5 solder is subject to corrosion in a humid environment, as is
  Ag5.5.  However, the QQ spec indicates that Ag1.5, which is used
  interchangeably with Ag2.5, has better shelf life and will not develop a
  black surface deposit.  I don't know if the corrosion for Ag2.5 means
just
  a black deposit, or if the solder joint will fail due to other type of
  corrosion.  I note that J-STD-006 does not include the same information
as
  does section 6 of QQ-S-571.

  During our qualification testing, we subjected a capacitor to high
humidity
  at high temp for an extended period of time with no evidence of
corrosion.


  Can you folks please answer the following questions?

  1.  What caused the conditions shown in the photographs?  What are the
  photographs showing?

  2.  Would brazing (probably a furnace braze, not sure) at too high or too
  low a temperature cause the condition?

  3.  Will Ag2.5 corrode in a humid environment? If so, what type of
  corrosion, and why can it occur?  Is it a black surface condition?, or
can
  the corrosion ultimately cause failure of the braze joint?  What is the
  physical science basis for the corrosion?  Why does it only occur for
  certain % of silver content, and not for all % of silver?

  4.  Why doesn't J-STD-006 have the same info as QQ-S-571 regarding
  corrosion of Ag2.5 and Ag5.5 solder?

  5.  Will the corrosion continue?

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kindly notify the sender by reply e-mail.

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