Colin Weber said:

>I have been reviewing comments from past emails to the Technet forum
>w.r.t. gold finishes on edge connectors.
>
>I have concluded I should not require a nickel barrier for my application.
>This could be qualified by noting the board will not be used in harsh
>environments or be inserted more than several times in it's lifetime.

Hang on a bit; before you conclude here's another comment: copper will
rapidly diffuse into the porous gold. The nickel barrier is universally
used between Cu and Au, and without it you will soon see a very ugly and
high resistance dark color on the thin Au plating typical of board
contacts. It's not simply a matter of hardness or wear resistance. Copper
oxides will make that edge connector a no-connect at logic voltages.

>However I am still left wondering about the thickness of the hard gold
>finish. In the past I have specified, for Class3, 1.3um. However, the
>product shall be used in a class 2 environment.
>Are there any disadvantages in using 1.3um (particularly since the IPC
>standards state 0.8um for class 2), apart from cost?

No. Bellcore/ATT used to require 50 uin Au, they still show it as a
"preferred" finish. To some extent, the additional thickness is a safety
factor because of the known porosity of Au electroplate finishes.


regards,


Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com

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