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topic 4776

Silver Migration Inhibitor


2000

Our company makes small beryllium oxide chip resistors with silver electrodes (applied as a silver paste then fired to fuse them to the BeO). We've encountered a problem with silver migration/dendrite growth causing short circuits. Silver was chosen for solderability and low cost. Materials such as platinum-gold would solve the problem, but at a significant cost increase. A lower cost solution might be to apply a barrier coat of nickel over the silver to prevent the migration then apply a solder plate for solderability. Does this sound reasonable? If so, what would be a good nickel thickness? Any recommendations or comments would be much appreciated.

Thank you.

George

George Flanagan
- Smithtown, New York


2000

It is possible to nickel plate BeO directly without silver paste and firing. For soldering purpose, you need only a couple of micron layer depending on the type of solder. Call us if you need help.

Mandar Sunthankar
- Fort Collins, Colorado


2000

Hey George,

The whisker, migration growth of some metal is thought to be stress related. The cure in most cases is to alloy the metal with a metal that stops the whisker growth. The right metal alloyed with the silver in the paste should be the ticket. Check with your supplier.

Regards,

Fred Mueller, CEF
- Royersford, Pennsylvania


2000

Hi, George! YES, the method of applying Ni as a barrier coat is usual on Ag electrodes on ceramics. Just see the data books of various SMD (surface mount devices) companies in the electronic parts buiz. They usually add a third layer of Sn for best solderability...

Lois Kleewein
Graz. Univ. of Tech'y - Graz, Austria


2000

You may be able to get away with 10 millionths or it may take 50 millionths. As a barrier between Al and Tin we use 50 and it works fine. For Au over Cu or Brass we've used 10 with good success.

jim conner
Jim Conner
Anoplex - Dallas, Texas USA

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