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April 2005

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Subject:
From:
John Maxwell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Maxwell <[log in to unmask]>
Date:
Mon, 11 Apr 2005 10:01:50 -0700
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Hi Ingemar,
I just recently joined the throngs of the unemployed after not surviving a
RIF (reduction of force) as there was not much need for a scientist when
times are tight in power supplies. Finished up determining what it takes to
make reliable (process, components & alloys) power supplies to meet RoHS
for both SMT and through hole assemblies for telecomn and out the door you
go. This gives me plenty of time to think about and answer your question in
excruciating detail.

I have not seen nor hear about a AgCuNiPbSn termination. Common termination
structures include Cu in a glass frit plated w/nickel barrier and then Sn
or SnPb layer. Copper termination is use in base metal electrode systems
like low fire NP0 ceramics where these is a Cu electrode or a Ni electrode
used in high k dielectric systems. Copper is adjacent to nickel in the
periodic table and has excellent solid solubility resulting is very low
ESR. This is why BME (base metal electrode) capacitors have ESR values 1/10
that of precious metal systems. Yes the answer as to why precious metal
electrodes systems have higher ESR is hidden later in the text.

Precious metal electrode systems use Ag or PdAg (older terminations) in a
glass frit where the metal flakes make point contact to a Ag or PdAg
electrode.

A third termination combination is to add a compliant conductive polymer
layer between the termination metal glass frit attached to the ceramic body
and is then nickel plated with either Sn or PbSn for solderability
preservation. Seifer out of the UK and AVX offer this type of termination
and I suspect other manufacturers will follow.

If the termination metal order was CuAgNiPbAg then that does make sense as
it is the flexible termination. If the metal order is AgCuNiPbSn then I am
not familiar with it. If you have a base metal part then NiCuAgNiPbSn would
be consistent with a silver filler polymer flexible termination system.

The image on Steve's web site is a classical BME nickel electrode, copper
glass frit w/nickel barrier and solder solderability preservation.

I do get long winded at time but hopefully all were not bored with the
details but it was fun for me.

John Maxwell


At 11:55 PM 4/10/2005, you wrote:
>John, need immediate advice from you, as you are being very familiar with
>ceramic caps.
>Got problem with 0603 100nF/16VDC/X7R, Rins > 10-100 kOhms, sometimes
>lower. Failure rate 1-2%.
>Q: Terminals AgCuNiSnPb instead of usual AgNiSnPb. Never seen Cu before.
>Why Cu?
>Thx in advance
>Ingemar Hernefjord
>Ericsson Microwave Systems
>
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