Concur with Kathy on all points .
On the switching (contact points) we tested with no resistivity changes on
carbon pill mounted in silicon pad action up to 50K cycles before we got
down to copper .
On the contact however ; once you wear the organic from top ; it does
oxidize ;
therefore unsuitable for more repeated low force low current switching . OK
for edge con's in commercial applications , just.

Which was the only reason why we keep NiAu ; which is not such a dream to
solder ; as we have the silipad switching .

Paul Klasek
http://www.resmed.com

-----Original Message-----
From: Kathy Palumbo [mailto:[log in to unmask]]
Sent: Tuesday, June 08, 1999 9:35 AM
To: [log in to unmask]
Subject: Re: [TN] Imersion Silver


Charles,

I did an extensive analysis (temperature cycling, vibration, humidity, lead
pull testing, and cross sectioning) on completed assemblies with this
coating on the PCB prior to approving it as an alternative coating to HASL.
I found that the coating is a direct drop in replacement to HASL.  In other
words you can use the coatings interchangeable with no problems.  The
storage life is equivalent to HASL.  The coating has no special handeling,
or storage requirements.  Keep in mind that if you are using the coating on
your PCB as a contact point (i.e. a KEY BOARD) then the silver immersion
coating is not the way to go (too thin).  If you intend to solder to the
coating, then it is not a problem.

We have been using silver immersion as an alternative coating to HASL for
more than 1 1/2 years with no problems.  The wetting action of the solder to
the pads was better than HASL coated PCB's, and the cross sectioning of
several solder joints showed an even better fill of the solder under the
leads than with HASL (which had quite a few voids).  The biggest advantage
was the elimination of bridging issues on fine pitch devices caused by the
variance of the HASL deposit.  We have virtually eliminated all of our
bridging issues on fine pitch devices.  This includes our PCMCIA Fax Modem
product, which use to be our worse yeild and now is one of the best.

Contact Steve Biegle with Alpha at (219) 922-7990.  He has a lot of good
data which you can review and use to set-up your own testing/evaluation
process.

If you have more specific questions regarding the testing I did you can
contact me direct.

Good Luck!!

Kathy Palumbo
Manufacturing Engineer
Viking COmponents
BUS.:  (949) 643-7255

----- Original Message -----
From: CharlesC <[log in to unmask]>
To: <[log in to unmask]>
Sent: 07 June 1999 14:33
Subject: [TN] Imersion Silver


> Once again I need help.
>  I am looking for information on Alpha Metal's "AlphaLevel" Imersion
silver
> deposition. I have never built boards made with this process and would
like to
> know what experience anyone else may have had with this (good or bad ).
The PWB
> is mixed, some through hole mostly surface mount. I would especially like
to
> know about solderability and storage life.
>
> Thanks in advance.
>
> Charles Caswell
> Process Lead,
> Printed Circuit Board Dept.
> Frontier Electronic Systems
>
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