Martin,
microwave boards are one important sector at our company. We have produced hundreds of thousands of ENIG boards for radio links. And the "frequency" covers many GHz. The reason why I say "frequency" is that it's a somewhat misused term. The uwave guys talk about dB, dBm, spurioses, Smith diagrams, S-parameters, insertion losses, and a lot more terms. If a conductor line somewhere is causing too high losses, or reflexions, or other inconviniences, one got many tricks to improve by compensating networks, amplification, phase changes and lots of uwave mystics. In rare cases, you need finally to change the metal system on the board. Now, we forget another term by just speaking conductor metallisation and that is the DIELECTRIC. If you speak with uwave guys, you'll hear more about dielectric than conductors! The cause is that the RF signals do not only need a good conductor, they need a suitable dielectric too. Obtaining the best dielectric field along the conductor is many a time the real art. In my opinion it's not unusual, that there is too little cooperation between the uwave theoretical specialists and the PWB maker. Today, you can simulate nearly everything in various uwave calculation programs, therefore, a study that way can save money and mistakes. So...the no-no ENIG worked by doing right calculations and optimum design and we needed no costly changes of supplier and plating etc.
Again, don't look for the best-in-show finish only, but take into account all the other parameters...
Good Luck.
Ingemar Hernefjord
Ericsson Microwave Systems
PS. This said, I don't show partiality towards ENIG, we use all other platings too. As the proverbe says 'don't put all eggs in the one and same basket'.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Martin Butcher
Sent: den 15 juni 2005 23:15
To: [log in to unmask]
Subject: [TN] RF board finishes
Hi All,
We are currently assembling an RF product (first time build) that utilizes
several fine pitch devices, leadless fine pitch devices and a great many
0402's. The board finish is currently HASL and as the volume ramps up there
is concern that defects related to the fine pitch and HASL will result in
unacceptable costs.
We prefer to use ENIG as a surface finish for non-RF products that fit this
Bill. I seem to recall reading something on this very Net that mentioned
nickel or ENIG being a no no for RF ccts.
I am not an RF guy and would love to get some feedback as to the effects of
various board finishes on RF products. Perhaps even recommendations as to a
"good" finish that will give better yield than HASL.
Regards,
Martin Butcher,
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