But Harry,
the query was only, why there was 1.1mils associated with the NI/Au?
Normal standards would call for 150 - 200 uinches of NI and upto 50uinches
of Au. Not 1.1mils!
Sincerely,
Brad Velander.
Lead PCB Designer
Norsat International Inc.
Microwave Products
Tel (604) 292-9089 (direct line)
Fax (604) 292-9010
email: [EMAIL PROTECTED]
http://www.norsat.com
See us at Booth S8155 at NAB 2002 in Las Vegas April 8 - 11.
> -----Original Message-----
> From: H. Selfridge [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, April 04, 2002 10:34 AM
> To: Protel EDA Forum
> Subject: Re: [PEDA] WANTED: PCB Expert (Off Topic)
>
>
> Copper on a printed circuit is subject to severe oxidation
> unless coated.
> Cu oxides are poor electrical conductors.
>
> Gold is a passive metal with excellent conductivity.
>
> If you plate gold directly on copper, Au/Cu intermetallics
> are formed that
> cause the bond to be brittle and subject to mechanical
> failure under stress.
>
> Plating nickel over the copper forms a barrier that has desirable
> intermetallic characteristics. However, Ni also oxidizes
> readily. Ni
> oxides are poor electrical conductors.
>
> Plating Au over the Ni gives the best overall metallic
> structure for a pcb
> (pwb). The Au is corrosion resistant, and has excellent
> conductivity. The
> Ni barrier under the Au prevents Cu migration into the Au.
> Ni/Au and Ni/Cu
> intermetallics at the bonds are both hard and relatively durable.
>
> That is half a semester in 5 lines that tells why nickel
> plating is used
> under gold on a pcb (pwb).
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