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/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
