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August 2004

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Subject:
From:
"Creswick, Steven" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Creswick, Steven
Date:
Mon, 30 Aug 2004 06:41:36 -0400
Content-Type:
text/plain
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text/plain (352 lines)
Karen,

I can not say how opaque mold compounds adhere to silver, but most of the optically clear ones that I am familar with advertise better adhesion to silver ... than say to gold plating [somewhat if a 'dah' statement, I realize, since the gold surface SHOULD be non-reactive].

Steve


-----Original Message-----
From: Karen Walters [mailto:[log in to unmask]]
Sent: Friday, August 27, 2004 11:15 AM
To: [log in to unmask]
Subject: Re: [TN] Corrosion in lead frames


Hi David Hillman

I have a question for you.  Do you see Ag lead finishes as a problem with
mold compound adhesion because of the surface finish.  I was told that this
could impact the adhesion property and cause moisture ingress problems.

Please advise.


(Embedded image moved to file: pic11942.pcx)


                                                                                                                                   
                      "David D. Hillman"                                                                                           
                      <ddhillma@ROCKWELLC        To:       [log in to unmask]                                                         
                      OLLINS.COM>                cc:                                                                               
                      Sent by: TechNet           Subject:  Re: [TN] Corrosion in lead frames                                       
                      <[log in to unmask]>                                                                                            
                                                                                                                                   
                                                                                                                                   
                      08/26/2004 11:59 AM                                                                                          
                      Please respond to                                                                                            
                      TechNet E-Mail                                                                                               
                      Forum; Please                                                                                                
                      respond to ddhillma                                                                                          
                                                                                                                                   
                                                                                                                                   




Hi Jose! The photo shows what appears to be silver sulfide (based on
observations we have made on silver issues at Collins). Depending on the
severity of the surface species attack you may or may not be able to
chemically restore the silver surface. Having the discoloration may not be
an indication that you will have problems - at least in terms of soldering,
some discoloration does not impede a flux's ability to create a
metallurgical joint. The same assumption may not hold true for wirebonding.
Good Luck.

Dave Hillman
Rockwell Collins



                      Jose Antonio
                      Garcia Ontalba           To:       [log in to unmask]
                      <ja.garcia@nagare        cc:
                      s.com>                   Subject:  Re: [TN] Corrosion
in lead frames
                      Sent by: TechNet
                      <[log in to unmask]>


                      08/26/2004 10:06
                      AM
                      Please respond to
                      ja.garcia






Hello together!

hier is the link with the image of my problem. Sure is easier to see it
than
my explanations!

http://www.geocities.com/karlsruhero/Silver_corrosion_image.ppt

Thank you for your help!

Best regards

Jose






-----Mensaje original-----
De: TechNet [mailto:[log in to unmask]]En nombre de David D. Hillman
Enviado el: jueves, 26 de agosto de 2004 15:39
Para: [log in to unmask]
Asunto: Re: [TN] Corrosion in lead frames


Hi Jose! It has been my observation/experience that silver oxides are clear
in appearance, silver chlorides are yellowish in appearance and silver
sulfides can be black-to-purpleish in appearance. We have used SERA testing
to confirm the surface species identification. I have not observed a red
color appearance in conjunction with silver. Good luck on solving the
problem.

Dave Hillman
Rockwell Collins
[log in to unmask]



                      Jose Antonio
                      Garcia Ontalba           To:       [log in to unmask]
                      <ja.garcia@nagare        cc:
                      s.com>                   Subject:  Re: [TN] Corrosion
in lead frames
                      Sent by: TechNet
                      <[log in to unmask]>


                      08/25/2004 12:21
                      PM
                      Please respond to
                      ja.garcia






Steve,

You are right, I am speaking of an alumina substrate with a Ag/Pt
metallization, but I have just realized that I was wrong in my first
message: the lead frame is really Ag/Pt and the coating is pure Ag. There
is
not more metalls involved.

I think the red spots are oxides of Ag or Pt or maybe both. But the oxides
of silver are not red coloured, aren't they? So, the red spots have to be
oxides of Pt... Maybe the tempeature helps the reaction of oxidation of Pt.
Anyway I am not sure.

What do you think?

Thank you very much!

Regards

Jose


-----Mensaje original-----
De: TechNet [mailto:[log in to unmask]]En nombre de Creswick, Steven
Enviado el: miércoles, 25 de agosto de 2004 18:02
Para: [log in to unmask]
Asunto: Re: [TN] Corrosion in lead frames


Jose,

Could the red-orange color be from exposed, oxidized copper?

You did not say whether the lead frame was copper, phosphor bronze, or
maybe
a Kovar (Fe, Ni, Co) composition.

 .... although, I am confused by a lead frame having Ag/Pt plating.  Hmmm.
Possibly, are you speaking of an alumina substrate having Ag/Pt
metallization (traces) on it?

Steve Creswick - Gentex

-----Original Message-----
From: Jose Antonio Garcia Ontalba [mailto:[log in to unmask]]
Sent: Wednesday, August 25, 2004 10:59 AM
To: [log in to unmask]
Subject: [TN] Corrosion in lead frames


Hello together!

I have an hybrid circuit with lead frames for bonding encapsulated with
gel.
These lead frames are used for bonding the wires of aluminium only with
heat
(without using solders, flux, etc.). We have made some durations test,
after
them appears some red-orange spots on the lead frames preferably in the
borders, and, in some cases, comes into view blue parts too. We have seen
with Infra-Red photographs that this part (wire+lead frame) is by far the
warmest of the PCB when it is working, because through it comes high
electric flow.

The lead frames have a coating of Ag/Pt and the gel's major components are:
silicone, Pt (polymerization's activator) and alumina (for the thermal
conductivity). The lead frames have not solder nor flux residues.

So, anybody could tell me what is happening in the lead frame? I suppose
that a chemical reaction involves the Ag and/or the Pt but I have no idea
which could be!

Thank you all for your help!

Best regards


--
José Antonio García Ontalba

Quality department
NAGARES, S.A.
Ctra. Madrid-Valencia, Km. 196
16200 Motilla del Palancar (Spain)
Tel:  00 34 969 18 00 21
Fax:  00 34 969 33 11 31
E-mail: [log in to unmask]
--

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