Gregg,
do you happen to have easy-to-mail copy of Wong and Tong?
Another good source is 'Conductive Adhesives for Electonic Packages' by
J.Liu 1999
ISBN 0 901 150 37 1
Ingemar
-----Original Message-----
From: Gregg Klawson [mailto:[log in to unmask]]
Sent: den 31 januari 2001 16:57
To: [log in to unmask]
Subject: Re: [TN] silver epoxy & solder coated parts
Jim,
I ran across this paper: "Mechanisms underlying the unstable contact
resistance of conductive adhesives", Lu, Wong, & Tong, IEEE 1999 Electronic
Components and Technology Conference. They conclude that "electrochemical
corrosion rather than direct metal oxidation is the dominant mechanism" for
increased DC resistance. They didn't find a problem when connecting Ag
filled adhesive to the noble metals Ag, Au, Pt but had issues with Ni, Sn,
Sn/Pb.
-- Gregg
At 09:09 AM 1/26/01, Marsico, James wrote:
>Thanks for all the responses regarding the use of silver epoxy and solder
>coated parts... obviously, not the way to go!
>I'm still trying to understand the mechanism for increased DC resistance,
>though. From what I have learned, silver oxides are conductive, so this
>isn't it. The tin seems to migrate into the epoxy, I assume leaving a
>lead-rich zone. Is it that the lead oxidizes? Are lead oxides conductive?
>Can anyone explain?
>Thanks again,
>Jim Marsico
>EDO Electronic Systems Group
>[log in to unmask] <mailto:[log in to unmask]>
>
>
>
> -----Original Message-----
> From: Mike Fenner [SMTP:[log in to unmask]]
> Sent: Wednesday, January 24, 2001 1:52 PM
> To: TechNet E-Mail Forum.; Marsico, James
> Subject: Re: [TN] silver epoxy & solder coated parts
>
> I would avoid it.
>
> Conventionally:
> Epoxy has poor adhesion to tin and its alloys
> The tin/silver interface will give an inter-reaction at the
bondline
> leading to electrical opens although you may retain mechanical
> adhesion. One/Two years is a long time in this situation
especially
>if
> you have mechanical stress/vibration or any temperature swings in
> service.
> This is very well documented in the literature and you should see
> something in the Technet archives.
>
> More open mindedly:
> There are some companies working on this and there are now
products
> which claim to have solved this problem, either by using a sort of
> halfway house product (adhesive with a fusible metal filler
>basically)
> or by special undisclosed ingredients/formulations.
> Contact suppliers for the latest
>
>
>
> Mike
>
>
> ----- Original Message -----
> From: "Marsico, James" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, January 23, 2001 8:34 PM
> Subject: [TN] silver epoxy & solder coated parts
>
>
> > Hello, Technet...
> >
> > Here is an unusual situation. We have to assemble a surface
mount
> assembly
> > using silver epoxy. Some of the components will be solder
coated.
> I know,
> > don't bother asking... this is the way it has to be. The good
>thing
> is that
> > this assembly is a prototype for bench-top laboratory use only.
> There is no
> > harsh environment and needs to operate 1, maybe 2, years. The
> question is
> > does anyone foresee any problems? What happens when one mixes
toe
> two
> > technologies?
> >
> > Thanks,
> > Jim Marsico
> > EDO Electronic Systems Group
> > [log in to unmask] <mailto:[log in to unmask]>
> >
>
>
>---------------------------------------------------------------------------
------
>Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
>To unsubscribe, send a message to [log in to unmask] with following text in
>the BODY (NOT the subject field): SIGNOFF Technet
>To temporarily halt delivery of Technet send the following message: SET
>Technet NOMAIL
>Search previous postings at: www.ipc.org > On-Line Resources & Databases >
>E-mail Archives
>Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
>information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
>ext.5315
>---------------------------------------------------------------------------
------
----------------------------------------------------------------------------
-----
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET
Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
----------------------------------------------------------------------------
-----
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
