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).



At 08:38 AM 4/4/02 -0600, you wrote:
snip
>Anyone know why you would use such a think nickle plating?
>Cheers
>Mark
snip

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* To post a message: mailto:[EMAIL PROTECTED]
*
* To leave this list visit:
* http://www.techservinc.com/protelusers/leave.html
*
* Contact the list manager:
* mailto:[EMAIL PROTECTED]
*
* Forum Guidelines Rules:
* http://www.techservinc.com/protelusers/forumrules.html
*
* Browse or Search previous postings:
* http://www.mail-archive.com/proteledaforum@techservinc.com
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Reply via email to